Ashok Layland 4o624n
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Ashok Leyland
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Ashok Leyland Ashok Leyland is an Indian automobile manufacturing company based in Chennai, India. Founded in 1948, it is the 2nd largest commercial vehicle manufacturer in India, 4th largest manufacturer of buses in the world and 16th largest manufacturer of trucks globally. Operating six plants, Ashok Leyland also makes spare parts and engines for industrial and marine applications. It sells about 60,000 vehicles and about 7,000 engines annually. It is the second largest commercial vehicle company in India in the medium and heavy commercial vehicle (M&HCV) segment with a market share of 28% (2007–08). With enger transportation options ranging from 19 seaters to 80 seaters, Ashok Leyland is a market leader in the bus segment. The company claims to carry more than 60 million engers a day, more people than the entire Indian rail network. In the trucks segment Ashok Leyland primarily concentrates on the 16 ton to 25 ton range of trucks. However Ashok Leyland has presence in the entire truck range starting from 7.5 tons to 49 tons. With a t venture with Nissan Motors of Japan the company made its presence in the Light Commercial Vehicle (LCV) segment (<7.5 tons). Ashok Leyland's UK subsidiary Optare has shut down its bus factory in Blackburn, Lancashire.[3] This subsidiary's traditional home in Leeds has also been vacated in favour of a purpose built plant at Sherburn-in-Elmet.
HISTORY
ASHOK MOTORS Ashok Motors was founded in 1948 by Raghunandan Saran, an Indian freedom fighter from Punjab.[4] After Independence, he was persuaded by India’s first Prime Minister Nehru, to invest in modern industrial venture. Ashok Motors was incorporated in 1948 as a company to assemble and manufacture Austin cars from England, and the company was named after the founder's only son Ashok Saran. The company had its headquarters in Rajaji Saalai, Chennai (then Madras) with the plant in Ennore, a small fishing hamlet in the North of Chennai. The Company was engaged in assembly and distribution of Austin A40 enger cars in India. UNDER LEYLAND Sometime later, Raghunandan Saran died in an air crash, prior to that he had been negotiating with Leyland Motors of England for assembly of commercial vehicles as he envisioned 2
commercial vehicle were more in need at that time than were enger cars. The company later under Madras State Government and other shareholders finalised for an investment and technology partner and thus Leyland Motors ed in 1954 with equity participation, changing the name of the company to Ashok Leyland. Ashok Leyland then started manufacturing commercial vehicles. Under Leyland's management with British expatriate and Indian executives the company grew in strength to become one of India's foremost commercial vehicle manufacturers. The collaboration ended sometime in 1975 but the holding of British Leyland, now a major British Auto Conglomerate as a result of several mergers agreed to assist in technology which continued until the 1980s. Post 1975, changes in management structures saw the company launch various advanced vehicles and pioneering innovations in the Indian market, with many of these models continuing to this day with numerous upgrades over the years.
PRODUCT RANGE OF THE COMPANY INCLUDES:
Buses
Trucks
Engines
Defence & Special Vehicles
ASSOCIATES COMPANIES:
Automotive Coaches & Components Ltd (ACCL)
Lanka Ashok Leyland
Hinduja Foundries
IRIZAR–TVS
Ashok Leyland Project Services Limited
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Awards/Achievements
In the journey towards global standards of quality, Ashok Leyland reached a major milestone in 1993 when it became the first in India's automobile history to win the ISO 9002 certification. The more comprehensive ISO 9001 certification came in 1994, QS 9000 in 1998 and ISO 14001 certification for all vehicle manufacturing units in 2002. It has also become the first Indian auto company to receive the latest ISO/TS 16949 Corporate Certification (in July 2006) which is specific to the auto industry.
DIRECTORS' REPORT
Performance / Operations
The Directors have pleasure in presenting the Annual Report of the Company, together with the financial statements, for the year ended March 31, 2015.
Company Performance
During the year under review, your Company witnessed a modest recovery in the Indian economy, enabling the Medium & Heavy Commercial Vehicle (M&HCV) industry to signal an uptrend after two years of down cycle. Whilst overall commercial vehicle volumes declined by 2.8% over the previous year, the M&HCV segment volumes increased by 16%. Your Company improved its market share from 26.1% to 28.6% in the M&HCV segment, facilitated by appropriate product mix in the growth segments, a sustained focus on meeting customer requirements and initiatives in network expansion. M&HCV export volumes grew by 31.7% to 11,218 units from 8,511 units last year, enabled by growth in target export markets.
In the Light Commercial Vehicle segment, the industry volumes contracted by 13.4%. However, your Company has been able to sustain the market share in the small Commercial Vehicle (2–3.5T) segment ed by sustained product improvements and variants on DOST, which is the 2nd largest player in the segment. The new PARTNER range of products has also achieved significant market share in the 6–7.5T segment, its first full year after launch.
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Power Solutions Business continued to have subdued demand due to improved power availability and slowdown in Industrial / Agricultural segments. The Spare Parts volumes have bounced back due to higher demand and focused actions at improving parts availability and competitiveness. Highlights of performance are discussed in detail in the Management Discussion and Analysis Report attached as Annexure–D to this Report.
DIVIDEND
The Directors recommend a dividend of 45% (Rs. 0.45 per equity share of Rs. 1/– each) for the financial year ended March 31, 2015. Payment of dividend is subject to the approval of shareholders at the ensuing Annual General Meeting.
FUND RAISING
EQUITY – QUALIFIED INSTITUTIONAL PLACEMENT
During the year under review, your Company successfully placed 185,200,000 equity shares through the process of Qualified Institutional Placement (QIP) and raised an amount of Rs. 666.72 crore. The proceeds received through QIP were utilised for the purpose for which it was raised. Consequent to the above, the paid up value of the equity share capital of the Company stands increased from Rs. 266.07 crore to Rs. 284.59 crore.
DEBT
Secured Non–Convertible Debentures (NCD)
During the year, your Company redeemed in full NCD Series AL 14 placed in July 2010 amounting to Rs. 70 crore. No fresh NCDs were issued during the year.
Rupee Term Loans
Your Company has repaid or prepaid Secured Rupee Term Loan availed from Banks to the tune of Rs. 450 crore during the year. No fresh Term Loan was availed during the year.
EXTERNAL COMMERCIAL BORROWINGS (ECBS) 5
During the year under review, your Company repaid ECB loan instalments that fell due, equivalent to USD 71.66 Mn. Your Company availed fresh ECBs for USD 20 Mn, from a Bank for an average tenor of 5 years on unsecured basis. The funds drawn under ECBs were utilised to fund capital expenditure program of the Company and other approved end uses as per extant Reserve Bank of India Guidelines and the of the loan. As at March 31, 2015, long term borrowings stood at Rs. 3,325 crore as against Rs. 4,103 crore on March 31, 2014.
Introduction to Engine Repair – Study Guide Introduction The engine is the power plant of a vehicle. Automotive engines have gone through tremendous changes since the automobile was first introduced in the 1880s, but all combustion engines still have three requirements that must be met to do their job of providing power – air, fuel, and ignition. The mixture of air and fuel must be compressed inside the engine in order to make it highly combustible and get the most out of the energy contained in the fuel mixture. Since the mixture is ignited within the engine, automobile power plants are called internal combustion engines. Most can be further classified as reciprocating piston engines, since pistons move up and down within cylinders to provide power. This up-and-down motion is converted into turning motion by the crankshaft. Some of the main engine components This course will provide an introduction to automotive engines and engine repair. Subjects covered will include: 6
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Major engine components
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Engine classifications
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The four stroke cycle and other engine design operations
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Engine construction
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General engine mechanical diagnosis
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Engine removal and installation
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Cylinder head and valve train diagnosis and repair
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Engine block assembly diagnosis and repair
Unit 1 - Basic Engine Parts and Operation Unit Objective: After completion of this unit, students should be able to identify internal combustion engine components and their modes of operation. Specific Objectives: •
Identify
engine
design
associated and definitions •
Identify internal combustion engine components
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Understand and be able to explain basic internal combustion engine operation 7
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Identify common internal combustion engine design classifications
A small engine, such as one found in a lawn mower, usually contains only one cylinder and piston. Automotive engines use a number of cylinders to produce sufficient power to drive the wheels, but operate much like a small engine in many ways. Let’s look at one cylinder of an engine to see how the main parts work together. Engine Block The block, highlighted at right in grey, is a heavy metal casting, usually cast iron or aluminum, which holds the lower parts of the engine together and in place. The block assembly consists of the block, crankshaft, main bearings and caps, connecting rods, pistons, and other components, and is referred to as the bottom end. The block may also house the camshaft, oil pump, and other parts. The block is machined with ages for oil circulation called oil galleries (not shown) and for coolant circulation called water jackets. Cylinders
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The cylinders are round holes or bores machined into the block for the pistons to travel up and down in. Pistons Combustion pressure acts upon the tops of the pistons in the cylinders, forcing them downward. Usually made of aluminum, the pistons transmit the downward force to the connecting rods. The top of the piston’s travel is called Top Dead Center (TDC) and the bottom of a piston’s travel is called Bottom Dead Center (BDC). Piston Rings Rings are installed in grooves around the pistons to form a seal between the piston and the cylinder wall. Two types of rings are used: compression rings, which prevent combustion pressure from entering the crankcase, and oil control rings, which prevent engine oil from entering the combustion chamber above the piston. Oil rings scrape excess oil from the cylinder walls for return to the crankcase.
Cylinde
Piston
Connecting Rod
Connecting Rods A rod connects each piston to the crankshaft. The small, upper end of the rod commonly has a bushing pressed into it. A piston pin, or wrist pin, attaches the piston to the rod through this bushing, which allows the rod to pivot as needed. The larger, lower end of the rod is attached to the crankshaft through rod bearing inserts that are stationary relative to the rod and allow the crankshaft to turn within the rod on a film of oil. 9
Crankshaft The crankshaft is a strong, alloyed iron or steel shaft that converts the up-and-down motion of the pistons into a turning motion that can be transmitted to the drive train. The crankshaft is ed by the block in several places along its length. The crankshaft rides in main bearings, which are inserts similar to the rod bearings at these s. Where the crankshaft is connected to the rods and where it is ed by the block are called journals. The crank is finely machined and polished at these places. The crankshaft is also drilled with a network of oil ages to deliver oil under pressure to these places from the oil galleries. Counterweights are formed onto the crankshaft to help prevent vibration. These weights are added to offset the weight of the piston and connecting rod assemblies. At the front of the crankshaft, outside the engine front cover, a heavy wheel containing a rubber vibration damper is installed. Also called a harmonic balancer, it often incorporates the crank drive belt pulley, which powers belt- driven accessories. At the rear of the crankshaft, a large flywheel is mounted. The flywheel can serve several purposes: a ring gear is mounted to its circumference to provide a means to start the engine. It also connects the engine to the transmission. Finally, on vehicles with manual transmissions, the flywheel is made very heavy to help smooth out power pulses from the engine (this is accomplished by the torque converter on vehicles equipped with automatic transmissions). Cylinder Head Like the engine block, cylinder heads are usually cast from either iron or aluminum. Most V-type, opposed, and 10
W-type engines have two cylinder heads. Inline engines have only one cylinder head. The head bolts to the top of the block, covering and enclosing the tops of the cylinders. The head forms small pockets over the tops of the pistons called combustion chambers. The spark plugs are threaded into holes in the head and protrude into the combustion chambers (gasoline engines). Intake ports and exhaust ports are cast into the head, and small holes called valve guides are machined into it to position the valves. The valves act as gates. When open, they let air and fuel into the cylinder and exhaust gas out. When closed, they seal the pressure of compression in the combustion chamber. The valves close against machined, press-fitted inserts in the combustion chamber ports called valve seats. On overhead cam engines like the one pictured here, the head also houses the camshaft. The assembly, together with other valve train components and the intake and exhaust manifolds, is referred to as the top end. Between the head and the block, a head gasket seals the combustion chambers, and water and oil ages.
Cylinder Head Valve Train The valve train consists of the valves, camshaft, and other associated parts. The valves control the flow of the incoming air-fuel mixture and the outgoing exhaust gasses. The intake valves are larger than the exhaust valves, and many engines today have two intake and two exhaust valves per cylinder to improve efficiency and performance.Like the crankshaft, the camshaft rides 11
on a film of oil as it rotates on journals. Rotation of the camshaft opens the valves, and valve springs close them. The camshaft has carefully machined high spots called lobes that act upon the valves (or other parts) to open each valve at precisely the right time. As the lobe moves away, the spring closes the valve. Some engines have dual overhead cams (DOHC), with a cam for the intake valves and one for the exhaust valves. The engine shown here uses a single overhead cam (SOHC). Engines with the camshaft located in the block are called pushrod engines, because long pushrods are used to transmit the camshaft’s movement up to the rocker arms, which rock to open the valves. On these engines, the cam acts on a valve lifter, which in turn acts on a pushrod to move the rocker arm and open the valve. We will examine this arrangement later. Overhead cam engines may have a set of parts called valve followers, which operate like lifters. Some engines have a gear on the camshaft to drive the ignition distributor and oil pump, and some diesel engines and older gasoline engines have a rounded lobe on the camshaft to drive a mechanical fuel pump.The engine top end and bottom end must be timed together so that the valves will open and close at the proper times for the positions of the pistons, and this is accomplished through the camshaft drive. The camshaft is driven by a Timing Gears and Belt Valve Train 12
sprocket gear mounted on the front of the crankshaft. The sprocket either meshes with a sprocket on the front of the camshaft, or, more often, the two sprockets are linked by a belt or a chain. In the engine shown here, timing gears and a timing belt are used. Both sprockets must be installed with their timing marks aligned in the proper positions in order to time the engine. The Four-Stroke Cycle (Otto Cycle) A stroke is one movement of the piston either down from Top Dead Center (TDC) to Bottom Dead Center (BDC), or up from BDC to TDC. The term “stroke” also refers to the physical distance between these two points. One stroke of the piston moves the crankshaft through one-half of a revolution. Almost all engines on the road today operate on a cycle of four piston strokes. The strokes are the intake stroke, compression stroke, power stroke, and the exhaust stroke. This cycle turns the crankshaft through two revolutions and then the process begins again.
Intake Stroke The process begins with the intake stroke. The piston moves down from top dead center (TDC) to bottom dead center (BDC). The movement of the piston creates a partial vacuum, drawing air and fuel into the cylinder through the open intake valve. The ideal air-fuel mixture for performance, economy and emission control is 14.7 parts air to 1 part fuel. On Throttle Body fuel Injection (TBI) systems and old carbureted systems, fuel is carried in the air stream through an intake manifold and into the intake port. On Multiport Fuel Injection (MFI) systems, each cylinder has its own injector, which allows fuel to be injected into the port with more precision and uniformity than possible with Throttle Body systems. During this stroke, the exhaust valve remains closed. Compression Stroke After the piston es BDC, the compression stroke begins. The intake valve closes and the 13
mixture in the cylinder is compressed by the piston as it moves upward again to TDC. The intake and exhaust valves are both closed during this stroke, so the pressure and temperature of the air-fuel mixture rises. A typical compression ratio for a gasoline engine might be 9:1. The compression ratio is the volume of the cylinder, including the combustion chamber, with the piston at BDC compared to the volume with the piston at TDC. The crankshaft has now made one revolution. Power Stroke This is what it’s all about! As the piston nears TDC with both valves closed, the compressed airfuel mixture is ignited. Combustion occurs, resulting in a tremendous pressure increase that pushes the piston back down the cylinder. This is the power or “working” stroke. The intake and exhaust valves remain closed. In an idling engine, this happens in each cylinder about five times a second and running at 4,000 RPM it happens over 30 times a second!
Exhaust Stroke Now, the spent gasses must be removed from the cylinder to make room for the next air-fuel charge. The exhaust stroke begins as the piston nears BDC. The exhaust valve opens and the piston moves upward again, pushing the burned exhaust gases out of the cylinder. The intake valve remains closed until the piston has almost reached TDC again. At this point, the engine has completed one full cycle, and the crankshaft has rotated twice. The entire process then repeats.
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Intake
Compression
Power
Exhaust
Other Engine Designs While the vast majority of automobile engines are gasoline- powered, four-stroke reciprocating piston engines, other engine designs have been developed and used in automobiles, some quite successfully. Additionally, changing economic, environmental, and political conditions have created a demand to modify or retire this proven workhorse with new or re-worked designs. As materials and technologies improve and evolve, some of these contenders may come into common use in automobiles. Two-Stroke Cycle Engines A two -stroke cycle engine is another reciprocating piston design. Every downstroke delivers power in this design, and it has no valve train. Instead, in a conventional two-stroke gasoline engine, the air-fuel and exhaust gas are managed by the piston as it covers and uncovers intake and exhaust ports in the side of the cylinder. It also has no oil sump or pressurized oil delivery system, because the crankcase is part of the fuel delivery system. Instead, the crankcase is lubricated by mixing a small amount of oil with the fuel. Being able to deliver power with every down stroke and not having a heavy valve train means the two-stroke engine can provide a lot of power for its size and weight. Two-stroke engines have been used for many years in small engine applications such as outboard boat engines, motorcycles, ultralight aircraft, chainsaws and lawn equipment, etc. Some two-stroke engine automobiles have been imported to the U.S., and many medium and heavy duty diesel applications are currently equipped with two-stroke engines. Unfortunately, the light weight and simplicity come at a price. Conventional two-stroke gasoline engines produce higher exhaust emissions and yield lower fuel economy than a comparable four-stroke engine. This is largely due to the burning of the oil in the combustion chamber and leakage of unburned fuel inherent in the engine’s design. The causes of this will be clearer when we examine the operation of the engine. Nevertheless, the twostroke engine has received renewed interest in recent years, as innovations and advancements in 15
fuel injection, materials, and engine management systems develop. These engines have a pressurized lubrication system, fuel injectors, and superchargers that compress the intake air, similar to a two-stroke diesel engine.
The Two-Stroke Cycle We’ll begin the explanation of the two-stroke cycle with thefiring of the spark plug, which occurs before every downstroke. As the piston moves down, delivering power, the intake and exhaust ports are both covered. At the same time, the downward movement of the piston is pressurizing the crankcase with the next air-fuel charge, which was drawn into the crankcase through the air-fuel inlet and around the reed valve. This pressure forces the reed valve to close. As the piston continues downward, it uncovers the exhaust port. Remaining combustion pressure begins to blow the spent gas out the port. Further downward movement uncovers the intake port as well, and both ports are open for an instant, as the pressurized air-fuel charge from the crankcase enters the cylinder. The incoming air-fuel purges the remaining exhaust gas from the cylinder. As the piston travels upward again, it covers the intake and exhaust ports so compression can begin. At the same time, the piston’s movement creates a vacuum in the crankcase, opening the reed valve again and drawing in the next air-fuel charge. End of up stroke
Near end of down stroke
Diesel Engines The diesel engine is another reciprocating piston 16
design. Diesel engines in enger cars and light trucks operate on the four-stroke cycle, but they have important differences from the gasoline engines we have discussed. The most significant difference is the way in which diesel engines ignite the fuel. Rather than using a spark to start the combustion, a diesel engine uses the heat produced by compression of the air in the cylinder. Diesel engines must compress the air much more than a gasoline engine does – about twice as much – in order to produce enough heat to ignite the fuel. Compression ignition engines such as diesels must be designed heavier and stronger than spark ignition engines to withstand the compression and combustion produced in the cylinders. These engines have steel sleeves pressed into their cylinder bores. Understanding Brakes : Air brake systems are used on heavy trucks for safety, efficiency and reliability. One major advantage to an air brake system is that since air never runs out, the air brake system can always be replenished. An air brake system is marginally functional even with a small leak. But don’t read that as; it is safe to drive your mixer with an air leak. Three in One: The air brake system is actually three separate systems - Service Brake, Parking Brake and Emergency Brake. The various components of an air brake system work together to create and maintain a supply of compressed air and convert air pressure energy into mechanical force. Service Brake: This system applies and releases the (service) brakes when the driver pushes/releases the brake pedal. Pushing the brake pedal, opens a valve to let air flow from the air tank through the airlines to a brake chamber. This air forces a pushrod out, which in turn pushes a slack adjuster, turning the camshaft, twisting the S-Cam forcing the brake linings to make 17
with the brake drum. This causes friction, which slows the vehicle. One drawback to air brakes is brake lag, which is the time required for air to flow through the lines and force the engagement of the linings to the drum. Though the travel time is less than a second, air brakes do not apply immediately after the driver pushes the brake pedal, as they do in a car. Parking Brake: To park the vehicle, a driver applies the spring brakes by pulling out the yellow valve on the dash. This releases air from the brake chamber which allows the brake spring to expand and forces the pushrod out which pushes a slack adjuster that turns the camshaft, twisting the S-Cam and forcing the brake linings against the brake drum. Emergency Brake brakes are held off by air pressure inside the brake chamber, which holds back a very powerful spring. When there is insufficient air in the system to keep the spring in the chamber restrained, the emergency brakes automatically engage. When air pressure falls below 60 psi, a low pressure warning light will come on along with an audible buzzer. If air pressure continues to fall, the emergency brake will automatically apply when air pressure drops to 20-45psi. The fail safe engineering of air brakes will not allow you to control activation of the emergency brake so look for a safe place to pull off the roadway as soon as the low pressure warning activates. Cylinder Head Diagnosis and Repair On-Car Valve Seal Replacement
As mentioned earlier in this course, many technicians will replace valve seals on highmileage engines in response to customer complaints of oil consumption and/or visible smoke out of the tailpipe. This is a short-term repair in many cases. Replacing the valve seals does not recondition the cylinder head, and may not solve the oil consumption problem long-term.
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Manufacturer’s specific published service procedures detailing component and fastener removal or installation sequence and fastener torque should be followed to the letter.
A generic overview of the valve seal replacement process is as follows. Note the key points in bold. 18
1. Disconnect the negative battery cable. 2. Remove the engine accessories necessary for valve cover removal. 3. Remove the valve cover(s). 4. Remove the valve train components (e.g., rocker arms, camshafts) necessary to gain access to the valve springs. 5. Remove the spark plugs. 6. Insert an air hose adapter into the spark plug opening for the cylinder being serviced. 7. Connect the shop air hose to the adapter and pressurize the cylinder. 8. Use a valve spring compressor to compress the valve spring. There are as many different designs of valve spring compressors as there are valvetrain designs. Be sure to use the right compressor for the engine you’re working on to minimize the possibility of injury or damage. 9. Remove the valve locks, retainers, and spring (See image). A magnet will be handy here to remove and capture the valve locks. Be careful not to drop them once they have been removed. 10. Remove the old valve stem seal. 11. Inspect the valve locks, valve lock grooves, and the valve stem and tip for signs of wear or damage. 12. Inspect the valve springs for squareness and signs of wear or damage. Measure their free height. To do this, stand all of the 19
springs on a flat surface next to each other. They should stand the same height and should stand squarely. If there is any discrepancy in their height or if any of the springs do not stand squarely, replace all of the springs. The tension of each valve spring can be tested using a special gauge. Extensive testing of valve springs is generally not cost effective. In most cases, it is cheaper to replace questionable valve springs than it is to test them, particularly in a high-mileage engine. 13. Inspect the top of the valve guide for signs of wear or damage. 14. Install a new valve seal.
Use caution to not nick, cut, chip, or otherwise damage the new valve seal during installation.
15. Reinstall the valve spring, retainer, and locks. Once the valve spring, retainer and locks have been reinstalled, use a brass or plastic-faced non-marring hammer to LIGHTLY tap the tip of the valve stem BEFORE releasing air pressure from the cylinder. Tap ONLY THE TIP of the valve stem, NOT the valve spring retainer. Tap lightly, but hard enough to move the valve off of its seat. You should hear a quick “pop” when the valve has moved caused by air pressure momentarily escaping the cylinder. This is done to make sure that the valve locks are properly installed and seated. Incorrectly secured or 20
damaged valve locks will cause major engine damage when the affected valve falls into the cylinder and collides with the moving piston while the engine is running!
16. Repeat these steps for each valve assembly. 17. Reinstall the valve train components and valve cover(s). 18. Reinstall the spark plugs and wires. 19. Reinstall the engine accessories and connect the negative battery cable. 20. Connect the exhaust ventilation equipment. Be sure to use approved exhaust ventilation equipment when operating a vehicle in an enclosed area. 21. Start the engine and check operation.
Cylinder Head Removal and Disassembly As with engine removal, there are so many different vehicle designs, engine and drivetrain configurations, and other variables that it would be impossible to come up with a valid, generic set of cylinder head removal instructions. Some vehicles may require that the engine assembly be removed from the vehicle before cylinder head removal because of space limitations.
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When removing or reinstalling a cylinder head, follow manufacturer’s specific published service procedures and instructions for the vehicle that you’re working on.
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Also follow standard safety guidelines and procedures when using engine cranes and stands, lifting equipment and safety stands.
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Manufacturer’s specific service procedures detailing component and fastener removal or installation sequence and fastener torque should be followed to the letter.
Be sure to drain coolant and other necessary fluids as completely as possible prior to cylinder head removal to avoid spills. 21
If the head is to be resurfaced or reconditioned, it should be partially disassembled once it has been removed from the engine. Bolt-on parts, like the intake and exhaust manifolds, thermostat housing, rocker shaft or camshaft, spark plugs, glow plugs, fuel injectors and the like should be removed at this time if they were not removed while pulling the head off.
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When removing or reinstalling these parts, follow manufacturer’s specific published service information and instructions for the vehicle that you’re working on.
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Manufacturer’s specific service procedures detailing component and fastener removal or installation sequence and fastener torque should be followed to the letter.
Do not remove the valves and springs at this time. This will be done during the inspection process. If you break a bolt or strip threads on the cylinder head where bolt-on parts attach during disassembly, make note of this. Don’t try to extract a broken bolt or perform a thread repair on the cylinder head until after the head has been inspected thoroughly. There’s no sense in fixing a cylinder head that an inspection may show needs replacement instead of reconditioning.
Once the cylinder head is off and the external bolt-on parts have been removed, the gasket sealing surfaces must be thoroughly cleaned. Be sure to clean all gasket surfaces, especially the head gasket surface and the manifold surfaces. Any gasket material left on the head surface will cause a leak when the engine is reassembled. The head gasket surface on the cylinder block deck should be cleaned as well.
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Use a gasket scraper to remove debris and gasket residue from gasket mating 22
surfaces as previously discussed. Cleaning gasket surfaces with surface conditioning disks is NOT recommended by vehicle manufacturers.
Cylinder Head Inspection Knowing the specific customer complaint (as discussed earlier) can help you find what you’re looking for when inspecting the cylinder head.
For example, cooling system concerns, like overheating and loss of engine coolant, can in many cases be traced to a warped or cracked cylinder head. Oil consumption complaints can sometimes be traced to worn valves and guides. Misfire and power loss complaints are sometimes caused by burned valves that cannot keep the pressure of combustion confined to the inside of the cylinder. In addition, you may find that in some cases that replacing cracked, worn, or high-mileage cylinder heads with new or reconditioned heads makes the most economic sense for the vehicle owner.
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Warpage Check Check the head gasket surface for warpage using a precision straightedge and a set of thin feeler gauges. Check the head gasket surface lengthwise and crosswise in several places. As a general guideline, warpage lengthwise should not measure more than .003 in. (0.076 mm) for a three cylinder (V6) head, .004 in. (0.102 mm) for a four cylinder or V8 head, or .006 in. (0.152 mm) for a straight six head. When measuring side-to-side, the maximum allowable limit for warpage for any head is . 002 in. (.05 mm) •
Manufacturer’s specific specifications for warpage should be followed to the letter. The figures given here are general guidelines.
If a cylinder head is warped, it should be straightened before any other machine work is done. This is typically a job that most shops will sublet out to an automotive machine shop. Some heads can be milled (shaved down) to make the gasket sealing surfaces flat and true again. Overhead cam cylinder heads are sometimes straightened by bolting the head down over shims to a straightening fixture. The head and fixture are then heated in an oven to 450 to 500 deg. F (230 to 260 deg. C) for three to six hours. The assembly is then cooled slowly to “de-stress” the 24
metal.
Black Lines = Straight edge Positions for Warpage Check Disassembly and Visual Inspection for Cracks After checking for warpage, a close visual inspection should also be made for hairline cracks in the combustion chambers, ports, face, sides and top of the head. Be sure to examine the spark plug, glow plug and/or injector holes for damaged threads and cracks. Look closely around the head bolt holes for cracks and evidence of coolant leakage. Many cracks can be very difficult to see. Keep in mind that there may be cracks that aren’t visible even under close scrutiny.
If a crack is found, don’t do anything else to the head until it is determined if the crack is repairable. In most cases, a cracked cylinder head will need to be replaced.
If no cracks are found after a close visual inspection, the valves and springs can be disassembled. Make sure to mark and record the location of each valve as it is removed.
The tips of the valve stems may have become mushroomed or enlarged from being pounded by the rocker arms. This can happen after an engine has been run for long periods of time with excessive valve clearance.
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GENRAL SERIVES STEPS :Emptying of components Components should be emptied as much as possible before dismantling commences. Some drain locations may become easier to access later during the work. See below for the components that are involved, although these are not in any particular order. For more detailed information and working instructions refer to the other service information in the respective groups from 1 to 9. Fluids and chemicals shall be handled, separated and stored in a suitable way and in accordance with local legislation and regulations. Engine, oil and filters Drain the engine oil through the drain plug (A). Remove the engine filters; the full flow filter (B) and by filter (C).
Manual gearbox, oil and filter
Drain and empty the gearbox oil through the drain plug 26
Unscrew the oil filter housing and remove the seal and oil filter.
Gearbox with compact retarder, oil filter Remove the oil filter (H) from the oil filter housing. Cover (D), gasket (E), adapter (F) and stay tube (G).
ZF gearbox, oil
Automatic gearbox, oil and filter
Drain the oil by removing the oil sump drain plug (B), and unscrew the oil filters (A).
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Final drive, oil
Topping-up and drain plugs (A) and (B).
Final drive with hub reduction, oil Topping-up and drain plugs (A and B).
The oil in the hub shall be drained separately.
Retarder, oil
Drain plug (D), topping-up plug (A), vent plug (E).
28
Transfer gearbox, oil
Drain plug (C), topping-up plug (B), level plug (A).
Power take-off, oil draining and filter removal
Drain plug (B), level/topping-up plug (A).
Water separator, filter
Remove the filter.
Driven front axle, oil
Front axle wheel gears. Drain plug (A), level/topping-up plug (B). 29
Front axle differential carrier. Drain plug (B). Urea tank
Remove the filler cap from the urea tank. Remove the drain plug. Empty the urea tank. Note: If urea solution comes into with disconnected electrical connectors, the urea solution spreads rapidly through the wiring and oxidises the metal, which can damage the connectors and cabling.
Urea filter Remove the drain plug and drain the filter housing. Remove the urea filter (A) from the pump unit. Note: If urea solution comes into with disconnected electrical connectors, the urea solution spreads rapidly through the wiring and oxidises the metal, which can damage the connectors and cabling. 30
Fuel tank
Empty the tank by removing the drain plug.
31
BREAKS: Supply System Components
The Air Compressor pumps air into the air tanks supplying the compressed air to power the air brake system and other air operated devices such as the water tank, Tire Boss, chute lock, tilt hopper, etc. It is lubricated by engine oil and is usually gear driven. The Air Compressor Governor controls when the air compressor will pump air into the tanks. When air tank pressure rises to the set maximum, or the “cut out” level, (around 125 psi) the governor stops the compressor from pumping air. When the tank pressure falls to the “cut in” pressure (around 100 psi), the governor allows the compressor to start pumping again. An Air Dryer helps to keep the system free of contaminants. A filter, typically containing a desiccant, is installed between the compressor and air tank to remove moisture and oil from the air. Air Tanks store compressed air. The tanks will hold enough air to allow the brakes to be used several times even if the compressor stops working. The tractors supply air tank receives air from the compressor and delivers it to the primary and secondary air tanks. The tank closest to the compressor is commonly referred to as the “wet tank” because that is where most moisture condenses.
32
Drain Valves manually or automatically purge the air tanks. Compressed air usually has some water and oil in it, which tends to collect in the bottom of the tank. The water can freeze in cold weather and lead to brake failure. Do not depend on the automatic drain valve – Manually drain the air tanks at the end of each driving day. The Air Supply Gauge on the dash indicates how much pressure is in the air tank. Note - Brakes out of adjustment are the #1 violation at weigh stations and the leading cause of braking inefficiency in an air brake system. The manual adjustment of an automatic slack adjuster to bring a brake pushrod stroke within legal limits is masking a mechanical problem and not fixing it. The manual adjustment should only be used as a temporary measure to correct the adjustment in an emergency situation as it is likely the brake will soon be back out of adjustment. Manual adjustment of slack adjusters is dangerous because it can give the operator a false sense of security about the effectiveness of the braking system.
33
Air Brake Test Ensuring the brakes are in peak operating condition is easily the single most important part of your truck inspection – Your life and the lives of others depend on being able to stop when you need to. The below guide will help you develop a proper routine when completing the daily safety inspection of your mixer truck.
Titan Air Brake Test Procedures The test must begin with the following assumptions: • •
Air tanks were drained during the previous post trip. Drain valves are closed. Tire Boss equipped trucks - Wheel valves closed. Reopen the wheel valves upon completion of the brake test to allow the system to inflate/deflate as needed.
34
Air Compressor Build Rate : •
Start the engine and allow the air pressure to increase to 85 PSI. When the air pressure gauge reaches 85 PSI, adjust the engine speed to 900 RPMS.
•
To satisfy this check, the air pressure must reach 100 PSI within 2 minutes
Air Leak Test: Before starting this check, the air system must be at full system pressure which is usually between 125-140 PSI. Rev the engine to 1200-1400 RPMS and watch the air pressure gauge. When the air system is fully pressurized, the pressure gauge will stop climbing and the compressor governor will kick out followed by a “psssst” air release. Complete the following steps: •
Release parking brake
•
Shut off engine
•
Depress the brake pedal as you would in an emergency situation and hold the pedal down for the count of one minute.
•
After the initial drop in air pressure from depressing the brake pedal, the truck must not lose any air as detected by hearing or movement of the air pressure gauge.
35
Low Air Warning: •
Turn the key to the RUN position – Do not start the engine
•
Fan the brake pedal off and watch the air pressure gauge. The low air warning light on the dash and the buzzer must sound before the air pressure reaches 60 PSI.
Emergency Brake Pop Out :
Turn off the key to stop the low air warning buzzer
36
Fan the brake pedal while watching the parking brake knob. The knob must pop out before all of the air is bled from the system – Usually about 20 PSI.
Brake Hold or Tug Test: -
Manual transmission – Start the truck. With the parking brake set, and your foot off the throttle, slowly release the clutch. If the brakes are working properly, the truck should not move. utomatic transmission Start and rev the engine to 1200-1400 RPMs untilthe air pressure gauge reads at least 100 PSI. Drive forward at 3-5 MPH and set the parking brake. The truck should quickly come to stop.
Ashoka Layland Gearing System 37
38
No. of Gear and Size
GEAR DRIVE TO PARLLER SHAFT 39
40
41
42
43
44
45
46
1
Ashok Leyland Ashok Leyland is an Indian automobile manufacturing company based in Chennai, India. Founded in 1948, it is the 2nd largest commercial vehicle manufacturer in India, 4th largest manufacturer of buses in the world and 16th largest manufacturer of trucks globally. Operating six plants, Ashok Leyland also makes spare parts and engines for industrial and marine applications. It sells about 60,000 vehicles and about 7,000 engines annually. It is the second largest commercial vehicle company in India in the medium and heavy commercial vehicle (M&HCV) segment with a market share of 28% (2007–08). With enger transportation options ranging from 19 seaters to 80 seaters, Ashok Leyland is a market leader in the bus segment. The company claims to carry more than 60 million engers a day, more people than the entire Indian rail network. In the trucks segment Ashok Leyland primarily concentrates on the 16 ton to 25 ton range of trucks. However Ashok Leyland has presence in the entire truck range starting from 7.5 tons to 49 tons. With a t venture with Nissan Motors of Japan the company made its presence in the Light Commercial Vehicle (LCV) segment (<7.5 tons). Ashok Leyland's UK subsidiary Optare has shut down its bus factory in Blackburn, Lancashire.[3] This subsidiary's traditional home in Leeds has also been vacated in favour of a purpose built plant at Sherburn-in-Elmet.
HISTORY
ASHOK MOTORS Ashok Motors was founded in 1948 by Raghunandan Saran, an Indian freedom fighter from Punjab.[4] After Independence, he was persuaded by India’s first Prime Minister Nehru, to invest in modern industrial venture. Ashok Motors was incorporated in 1948 as a company to assemble and manufacture Austin cars from England, and the company was named after the founder's only son Ashok Saran. The company had its headquarters in Rajaji Saalai, Chennai (then Madras) with the plant in Ennore, a small fishing hamlet in the North of Chennai. The Company was engaged in assembly and distribution of Austin A40 enger cars in India. UNDER LEYLAND Sometime later, Raghunandan Saran died in an air crash, prior to that he had been negotiating with Leyland Motors of England for assembly of commercial vehicles as he envisioned 2
commercial vehicle were more in need at that time than were enger cars. The company later under Madras State Government and other shareholders finalised for an investment and technology partner and thus Leyland Motors ed in 1954 with equity participation, changing the name of the company to Ashok Leyland. Ashok Leyland then started manufacturing commercial vehicles. Under Leyland's management with British expatriate and Indian executives the company grew in strength to become one of India's foremost commercial vehicle manufacturers. The collaboration ended sometime in 1975 but the holding of British Leyland, now a major British Auto Conglomerate as a result of several mergers agreed to assist in technology which continued until the 1980s. Post 1975, changes in management structures saw the company launch various advanced vehicles and pioneering innovations in the Indian market, with many of these models continuing to this day with numerous upgrades over the years.
PRODUCT RANGE OF THE COMPANY INCLUDES:
Buses
Trucks
Engines
Defence & Special Vehicles
ASSOCIATES COMPANIES:
Automotive Coaches & Components Ltd (ACCL)
Lanka Ashok Leyland
Hinduja Foundries
IRIZAR–TVS
Ashok Leyland Project Services Limited
3
Awards/Achievements
In the journey towards global standards of quality, Ashok Leyland reached a major milestone in 1993 when it became the first in India's automobile history to win the ISO 9002 certification. The more comprehensive ISO 9001 certification came in 1994, QS 9000 in 1998 and ISO 14001 certification for all vehicle manufacturing units in 2002. It has also become the first Indian auto company to receive the latest ISO/TS 16949 Corporate Certification (in July 2006) which is specific to the auto industry.
DIRECTORS' REPORT
Performance / Operations
The Directors have pleasure in presenting the Annual Report of the Company, together with the financial statements, for the year ended March 31, 2015.
Company Performance
During the year under review, your Company witnessed a modest recovery in the Indian economy, enabling the Medium & Heavy Commercial Vehicle (M&HCV) industry to signal an uptrend after two years of down cycle. Whilst overall commercial vehicle volumes declined by 2.8% over the previous year, the M&HCV segment volumes increased by 16%. Your Company improved its market share from 26.1% to 28.6% in the M&HCV segment, facilitated by appropriate product mix in the growth segments, a sustained focus on meeting customer requirements and initiatives in network expansion. M&HCV export volumes grew by 31.7% to 11,218 units from 8,511 units last year, enabled by growth in target export markets.
In the Light Commercial Vehicle segment, the industry volumes contracted by 13.4%. However, your Company has been able to sustain the market share in the small Commercial Vehicle (2–3.5T) segment ed by sustained product improvements and variants on DOST, which is the 2nd largest player in the segment. The new PARTNER range of products has also achieved significant market share in the 6–7.5T segment, its first full year after launch.
4
Power Solutions Business continued to have subdued demand due to improved power availability and slowdown in Industrial / Agricultural segments. The Spare Parts volumes have bounced back due to higher demand and focused actions at improving parts availability and competitiveness. Highlights of performance are discussed in detail in the Management Discussion and Analysis Report attached as Annexure–D to this Report.
DIVIDEND
The Directors recommend a dividend of 45% (Rs. 0.45 per equity share of Rs. 1/– each) for the financial year ended March 31, 2015. Payment of dividend is subject to the approval of shareholders at the ensuing Annual General Meeting.
FUND RAISING
EQUITY – QUALIFIED INSTITUTIONAL PLACEMENT
During the year under review, your Company successfully placed 185,200,000 equity shares through the process of Qualified Institutional Placement (QIP) and raised an amount of Rs. 666.72 crore. The proceeds received through QIP were utilised for the purpose for which it was raised. Consequent to the above, the paid up value of the equity share capital of the Company stands increased from Rs. 266.07 crore to Rs. 284.59 crore.
DEBT
Secured Non–Convertible Debentures (NCD)
During the year, your Company redeemed in full NCD Series AL 14 placed in July 2010 amounting to Rs. 70 crore. No fresh NCDs were issued during the year.
Rupee Term Loans
Your Company has repaid or prepaid Secured Rupee Term Loan availed from Banks to the tune of Rs. 450 crore during the year. No fresh Term Loan was availed during the year.
EXTERNAL COMMERCIAL BORROWINGS (ECBS) 5
During the year under review, your Company repaid ECB loan instalments that fell due, equivalent to USD 71.66 Mn. Your Company availed fresh ECBs for USD 20 Mn, from a Bank for an average tenor of 5 years on unsecured basis. The funds drawn under ECBs were utilised to fund capital expenditure program of the Company and other approved end uses as per extant Reserve Bank of India Guidelines and the of the loan. As at March 31, 2015, long term borrowings stood at Rs. 3,325 crore as against Rs. 4,103 crore on March 31, 2014.
Introduction to Engine Repair – Study Guide Introduction The engine is the power plant of a vehicle. Automotive engines have gone through tremendous changes since the automobile was first introduced in the 1880s, but all combustion engines still have three requirements that must be met to do their job of providing power – air, fuel, and ignition. The mixture of air and fuel must be compressed inside the engine in order to make it highly combustible and get the most out of the energy contained in the fuel mixture. Since the mixture is ignited within the engine, automobile power plants are called internal combustion engines. Most can be further classified as reciprocating piston engines, since pistons move up and down within cylinders to provide power. This up-and-down motion is converted into turning motion by the crankshaft. Some of the main engine components This course will provide an introduction to automotive engines and engine repair. Subjects covered will include: 6
•
Major engine components
•
Engine classifications
•
The four stroke cycle and other engine design operations
•
Engine construction
•
General engine mechanical diagnosis
•
Engine removal and installation
•
Cylinder head and valve train diagnosis and repair
•
Engine block assembly diagnosis and repair
Unit 1 - Basic Engine Parts and Operation Unit Objective: After completion of this unit, students should be able to identify internal combustion engine components and their modes of operation. Specific Objectives: •
Identify
engine
design
associated and definitions •
Identify internal combustion engine components
•
Understand and be able to explain basic internal combustion engine operation 7
•
Identify common internal combustion engine design classifications
A small engine, such as one found in a lawn mower, usually contains only one cylinder and piston. Automotive engines use a number of cylinders to produce sufficient power to drive the wheels, but operate much like a small engine in many ways. Let’s look at one cylinder of an engine to see how the main parts work together. Engine Block The block, highlighted at right in grey, is a heavy metal casting, usually cast iron or aluminum, which holds the lower parts of the engine together and in place. The block assembly consists of the block, crankshaft, main bearings and caps, connecting rods, pistons, and other components, and is referred to as the bottom end. The block may also house the camshaft, oil pump, and other parts. The block is machined with ages for oil circulation called oil galleries (not shown) and for coolant circulation called water jackets. Cylinders
8
The cylinders are round holes or bores machined into the block for the pistons to travel up and down in. Pistons Combustion pressure acts upon the tops of the pistons in the cylinders, forcing them downward. Usually made of aluminum, the pistons transmit the downward force to the connecting rods. The top of the piston’s travel is called Top Dead Center (TDC) and the bottom of a piston’s travel is called Bottom Dead Center (BDC). Piston Rings Rings are installed in grooves around the pistons to form a seal between the piston and the cylinder wall. Two types of rings are used: compression rings, which prevent combustion pressure from entering the crankcase, and oil control rings, which prevent engine oil from entering the combustion chamber above the piston. Oil rings scrape excess oil from the cylinder walls for return to the crankcase.
Cylinde
Piston
Connecting Rod
Connecting Rods A rod connects each piston to the crankshaft. The small, upper end of the rod commonly has a bushing pressed into it. A piston pin, or wrist pin, attaches the piston to the rod through this bushing, which allows the rod to pivot as needed. The larger, lower end of the rod is attached to the crankshaft through rod bearing inserts that are stationary relative to the rod and allow the crankshaft to turn within the rod on a film of oil. 9
Crankshaft The crankshaft is a strong, alloyed iron or steel shaft that converts the up-and-down motion of the pistons into a turning motion that can be transmitted to the drive train. The crankshaft is ed by the block in several places along its length. The crankshaft rides in main bearings, which are inserts similar to the rod bearings at these s. Where the crankshaft is connected to the rods and where it is ed by the block are called journals. The crank is finely machined and polished at these places. The crankshaft is also drilled with a network of oil ages to deliver oil under pressure to these places from the oil galleries. Counterweights are formed onto the crankshaft to help prevent vibration. These weights are added to offset the weight of the piston and connecting rod assemblies. At the front of the crankshaft, outside the engine front cover, a heavy wheel containing a rubber vibration damper is installed. Also called a harmonic balancer, it often incorporates the crank drive belt pulley, which powers belt- driven accessories. At the rear of the crankshaft, a large flywheel is mounted. The flywheel can serve several purposes: a ring gear is mounted to its circumference to provide a means to start the engine. It also connects the engine to the transmission. Finally, on vehicles with manual transmissions, the flywheel is made very heavy to help smooth out power pulses from the engine (this is accomplished by the torque converter on vehicles equipped with automatic transmissions). Cylinder Head Like the engine block, cylinder heads are usually cast from either iron or aluminum. Most V-type, opposed, and 10
W-type engines have two cylinder heads. Inline engines have only one cylinder head. The head bolts to the top of the block, covering and enclosing the tops of the cylinders. The head forms small pockets over the tops of the pistons called combustion chambers. The spark plugs are threaded into holes in the head and protrude into the combustion chambers (gasoline engines). Intake ports and exhaust ports are cast into the head, and small holes called valve guides are machined into it to position the valves. The valves act as gates. When open, they let air and fuel into the cylinder and exhaust gas out. When closed, they seal the pressure of compression in the combustion chamber. The valves close against machined, press-fitted inserts in the combustion chamber ports called valve seats. On overhead cam engines like the one pictured here, the head also houses the camshaft. The assembly, together with other valve train components and the intake and exhaust manifolds, is referred to as the top end. Between the head and the block, a head gasket seals the combustion chambers, and water and oil ages.
Cylinder Head Valve Train The valve train consists of the valves, camshaft, and other associated parts. The valves control the flow of the incoming air-fuel mixture and the outgoing exhaust gasses. The intake valves are larger than the exhaust valves, and many engines today have two intake and two exhaust valves per cylinder to improve efficiency and performance.Like the crankshaft, the camshaft rides 11
on a film of oil as it rotates on journals. Rotation of the camshaft opens the valves, and valve springs close them. The camshaft has carefully machined high spots called lobes that act upon the valves (or other parts) to open each valve at precisely the right time. As the lobe moves away, the spring closes the valve. Some engines have dual overhead cams (DOHC), with a cam for the intake valves and one for the exhaust valves. The engine shown here uses a single overhead cam (SOHC). Engines with the camshaft located in the block are called pushrod engines, because long pushrods are used to transmit the camshaft’s movement up to the rocker arms, which rock to open the valves. On these engines, the cam acts on a valve lifter, which in turn acts on a pushrod to move the rocker arm and open the valve. We will examine this arrangement later. Overhead cam engines may have a set of parts called valve followers, which operate like lifters. Some engines have a gear on the camshaft to drive the ignition distributor and oil pump, and some diesel engines and older gasoline engines have a rounded lobe on the camshaft to drive a mechanical fuel pump.The engine top end and bottom end must be timed together so that the valves will open and close at the proper times for the positions of the pistons, and this is accomplished through the camshaft drive. The camshaft is driven by a Timing Gears and Belt Valve Train 12
sprocket gear mounted on the front of the crankshaft. The sprocket either meshes with a sprocket on the front of the camshaft, or, more often, the two sprockets are linked by a belt or a chain. In the engine shown here, timing gears and a timing belt are used. Both sprockets must be installed with their timing marks aligned in the proper positions in order to time the engine. The Four-Stroke Cycle (Otto Cycle) A stroke is one movement of the piston either down from Top Dead Center (TDC) to Bottom Dead Center (BDC), or up from BDC to TDC. The term “stroke” also refers to the physical distance between these two points. One stroke of the piston moves the crankshaft through one-half of a revolution. Almost all engines on the road today operate on a cycle of four piston strokes. The strokes are the intake stroke, compression stroke, power stroke, and the exhaust stroke. This cycle turns the crankshaft through two revolutions and then the process begins again.
Intake Stroke The process begins with the intake stroke. The piston moves down from top dead center (TDC) to bottom dead center (BDC). The movement of the piston creates a partial vacuum, drawing air and fuel into the cylinder through the open intake valve. The ideal air-fuel mixture for performance, economy and emission control is 14.7 parts air to 1 part fuel. On Throttle Body fuel Injection (TBI) systems and old carbureted systems, fuel is carried in the air stream through an intake manifold and into the intake port. On Multiport Fuel Injection (MFI) systems, each cylinder has its own injector, which allows fuel to be injected into the port with more precision and uniformity than possible with Throttle Body systems. During this stroke, the exhaust valve remains closed. Compression Stroke After the piston es BDC, the compression stroke begins. The intake valve closes and the 13
mixture in the cylinder is compressed by the piston as it moves upward again to TDC. The intake and exhaust valves are both closed during this stroke, so the pressure and temperature of the air-fuel mixture rises. A typical compression ratio for a gasoline engine might be 9:1. The compression ratio is the volume of the cylinder, including the combustion chamber, with the piston at BDC compared to the volume with the piston at TDC. The crankshaft has now made one revolution. Power Stroke This is what it’s all about! As the piston nears TDC with both valves closed, the compressed airfuel mixture is ignited. Combustion occurs, resulting in a tremendous pressure increase that pushes the piston back down the cylinder. This is the power or “working” stroke. The intake and exhaust valves remain closed. In an idling engine, this happens in each cylinder about five times a second and running at 4,000 RPM it happens over 30 times a second!
Exhaust Stroke Now, the spent gasses must be removed from the cylinder to make room for the next air-fuel charge. The exhaust stroke begins as the piston nears BDC. The exhaust valve opens and the piston moves upward again, pushing the burned exhaust gases out of the cylinder. The intake valve remains closed until the piston has almost reached TDC again. At this point, the engine has completed one full cycle, and the crankshaft has rotated twice. The entire process then repeats.
14
Intake
Compression
Power
Exhaust
Other Engine Designs While the vast majority of automobile engines are gasoline- powered, four-stroke reciprocating piston engines, other engine designs have been developed and used in automobiles, some quite successfully. Additionally, changing economic, environmental, and political conditions have created a demand to modify or retire this proven workhorse with new or re-worked designs. As materials and technologies improve and evolve, some of these contenders may come into common use in automobiles. Two-Stroke Cycle Engines A two -stroke cycle engine is another reciprocating piston design. Every downstroke delivers power in this design, and it has no valve train. Instead, in a conventional two-stroke gasoline engine, the air-fuel and exhaust gas are managed by the piston as it covers and uncovers intake and exhaust ports in the side of the cylinder. It also has no oil sump or pressurized oil delivery system, because the crankcase is part of the fuel delivery system. Instead, the crankcase is lubricated by mixing a small amount of oil with the fuel. Being able to deliver power with every down stroke and not having a heavy valve train means the two-stroke engine can provide a lot of power for its size and weight. Two-stroke engines have been used for many years in small engine applications such as outboard boat engines, motorcycles, ultralight aircraft, chainsaws and lawn equipment, etc. Some two-stroke engine automobiles have been imported to the U.S., and many medium and heavy duty diesel applications are currently equipped with two-stroke engines. Unfortunately, the light weight and simplicity come at a price. Conventional two-stroke gasoline engines produce higher exhaust emissions and yield lower fuel economy than a comparable four-stroke engine. This is largely due to the burning of the oil in the combustion chamber and leakage of unburned fuel inherent in the engine’s design. The causes of this will be clearer when we examine the operation of the engine. Nevertheless, the twostroke engine has received renewed interest in recent years, as innovations and advancements in 15
fuel injection, materials, and engine management systems develop. These engines have a pressurized lubrication system, fuel injectors, and superchargers that compress the intake air, similar to a two-stroke diesel engine.
The Two-Stroke Cycle We’ll begin the explanation of the two-stroke cycle with thefiring of the spark plug, which occurs before every downstroke. As the piston moves down, delivering power, the intake and exhaust ports are both covered. At the same time, the downward movement of the piston is pressurizing the crankcase with the next air-fuel charge, which was drawn into the crankcase through the air-fuel inlet and around the reed valve. This pressure forces the reed valve to close. As the piston continues downward, it uncovers the exhaust port. Remaining combustion pressure begins to blow the spent gas out the port. Further downward movement uncovers the intake port as well, and both ports are open for an instant, as the pressurized air-fuel charge from the crankcase enters the cylinder. The incoming air-fuel purges the remaining exhaust gas from the cylinder. As the piston travels upward again, it covers the intake and exhaust ports so compression can begin. At the same time, the piston’s movement creates a vacuum in the crankcase, opening the reed valve again and drawing in the next air-fuel charge. End of up stroke
Near end of down stroke
Diesel Engines The diesel engine is another reciprocating piston 16
design. Diesel engines in enger cars and light trucks operate on the four-stroke cycle, but they have important differences from the gasoline engines we have discussed. The most significant difference is the way in which diesel engines ignite the fuel. Rather than using a spark to start the combustion, a diesel engine uses the heat produced by compression of the air in the cylinder. Diesel engines must compress the air much more than a gasoline engine does – about twice as much – in order to produce enough heat to ignite the fuel. Compression ignition engines such as diesels must be designed heavier and stronger than spark ignition engines to withstand the compression and combustion produced in the cylinders. These engines have steel sleeves pressed into their cylinder bores. Understanding Brakes : Air brake systems are used on heavy trucks for safety, efficiency and reliability. One major advantage to an air brake system is that since air never runs out, the air brake system can always be replenished. An air brake system is marginally functional even with a small leak. But don’t read that as; it is safe to drive your mixer with an air leak. Three in One: The air brake system is actually three separate systems - Service Brake, Parking Brake and Emergency Brake. The various components of an air brake system work together to create and maintain a supply of compressed air and convert air pressure energy into mechanical force. Service Brake: This system applies and releases the (service) brakes when the driver pushes/releases the brake pedal. Pushing the brake pedal, opens a valve to let air flow from the air tank through the airlines to a brake chamber. This air forces a pushrod out, which in turn pushes a slack adjuster, turning the camshaft, twisting the S-Cam forcing the brake linings to make 17
with the brake drum. This causes friction, which slows the vehicle. One drawback to air brakes is brake lag, which is the time required for air to flow through the lines and force the engagement of the linings to the drum. Though the travel time is less than a second, air brakes do not apply immediately after the driver pushes the brake pedal, as they do in a car. Parking Brake: To park the vehicle, a driver applies the spring brakes by pulling out the yellow valve on the dash. This releases air from the brake chamber which allows the brake spring to expand and forces the pushrod out which pushes a slack adjuster that turns the camshaft, twisting the S-Cam and forcing the brake linings against the brake drum. Emergency Brake brakes are held off by air pressure inside the brake chamber, which holds back a very powerful spring. When there is insufficient air in the system to keep the spring in the chamber restrained, the emergency brakes automatically engage. When air pressure falls below 60 psi, a low pressure warning light will come on along with an audible buzzer. If air pressure continues to fall, the emergency brake will automatically apply when air pressure drops to 20-45psi. The fail safe engineering of air brakes will not allow you to control activation of the emergency brake so look for a safe place to pull off the roadway as soon as the low pressure warning activates. Cylinder Head Diagnosis and Repair On-Car Valve Seal Replacement
As mentioned earlier in this course, many technicians will replace valve seals on highmileage engines in response to customer complaints of oil consumption and/or visible smoke out of the tailpipe. This is a short-term repair in many cases. Replacing the valve seals does not recondition the cylinder head, and may not solve the oil consumption problem long-term.
•
Manufacturer’s specific published service procedures detailing component and fastener removal or installation sequence and fastener torque should be followed to the letter.
A generic overview of the valve seal replacement process is as follows. Note the key points in bold. 18
1. Disconnect the negative battery cable. 2. Remove the engine accessories necessary for valve cover removal. 3. Remove the valve cover(s). 4. Remove the valve train components (e.g., rocker arms, camshafts) necessary to gain access to the valve springs. 5. Remove the spark plugs. 6. Insert an air hose adapter into the spark plug opening for the cylinder being serviced. 7. Connect the shop air hose to the adapter and pressurize the cylinder. 8. Use a valve spring compressor to compress the valve spring. There are as many different designs of valve spring compressors as there are valvetrain designs. Be sure to use the right compressor for the engine you’re working on to minimize the possibility of injury or damage. 9. Remove the valve locks, retainers, and spring (See image). A magnet will be handy here to remove and capture the valve locks. Be careful not to drop them once they have been removed. 10. Remove the old valve stem seal. 11. Inspect the valve locks, valve lock grooves, and the valve stem and tip for signs of wear or damage. 12. Inspect the valve springs for squareness and signs of wear or damage. Measure their free height. To do this, stand all of the 19
springs on a flat surface next to each other. They should stand the same height and should stand squarely. If there is any discrepancy in their height or if any of the springs do not stand squarely, replace all of the springs. The tension of each valve spring can be tested using a special gauge. Extensive testing of valve springs is generally not cost effective. In most cases, it is cheaper to replace questionable valve springs than it is to test them, particularly in a high-mileage engine. 13. Inspect the top of the valve guide for signs of wear or damage. 14. Install a new valve seal.
Use caution to not nick, cut, chip, or otherwise damage the new valve seal during installation.
15. Reinstall the valve spring, retainer, and locks. Once the valve spring, retainer and locks have been reinstalled, use a brass or plastic-faced non-marring hammer to LIGHTLY tap the tip of the valve stem BEFORE releasing air pressure from the cylinder. Tap ONLY THE TIP of the valve stem, NOT the valve spring retainer. Tap lightly, but hard enough to move the valve off of its seat. You should hear a quick “pop” when the valve has moved caused by air pressure momentarily escaping the cylinder. This is done to make sure that the valve locks are properly installed and seated. Incorrectly secured or 20
damaged valve locks will cause major engine damage when the affected valve falls into the cylinder and collides with the moving piston while the engine is running!
16. Repeat these steps for each valve assembly. 17. Reinstall the valve train components and valve cover(s). 18. Reinstall the spark plugs and wires. 19. Reinstall the engine accessories and connect the negative battery cable. 20. Connect the exhaust ventilation equipment. Be sure to use approved exhaust ventilation equipment when operating a vehicle in an enclosed area. 21. Start the engine and check operation.
Cylinder Head Removal and Disassembly As with engine removal, there are so many different vehicle designs, engine and drivetrain configurations, and other variables that it would be impossible to come up with a valid, generic set of cylinder head removal instructions. Some vehicles may require that the engine assembly be removed from the vehicle before cylinder head removal because of space limitations.
•
When removing or reinstalling a cylinder head, follow manufacturer’s specific published service procedures and instructions for the vehicle that you’re working on.
•
Also follow standard safety guidelines and procedures when using engine cranes and stands, lifting equipment and safety stands.
•
Manufacturer’s specific service procedures detailing component and fastener removal or installation sequence and fastener torque should be followed to the letter.
Be sure to drain coolant and other necessary fluids as completely as possible prior to cylinder head removal to avoid spills. 21
If the head is to be resurfaced or reconditioned, it should be partially disassembled once it has been removed from the engine. Bolt-on parts, like the intake and exhaust manifolds, thermostat housing, rocker shaft or camshaft, spark plugs, glow plugs, fuel injectors and the like should be removed at this time if they were not removed while pulling the head off.
•
When removing or reinstalling these parts, follow manufacturer’s specific published service information and instructions for the vehicle that you’re working on.
•
Manufacturer’s specific service procedures detailing component and fastener removal or installation sequence and fastener torque should be followed to the letter.
Do not remove the valves and springs at this time. This will be done during the inspection process. If you break a bolt or strip threads on the cylinder head where bolt-on parts attach during disassembly, make note of this. Don’t try to extract a broken bolt or perform a thread repair on the cylinder head until after the head has been inspected thoroughly. There’s no sense in fixing a cylinder head that an inspection may show needs replacement instead of reconditioning.
Once the cylinder head is off and the external bolt-on parts have been removed, the gasket sealing surfaces must be thoroughly cleaned. Be sure to clean all gasket surfaces, especially the head gasket surface and the manifold surfaces. Any gasket material left on the head surface will cause a leak when the engine is reassembled. The head gasket surface on the cylinder block deck should be cleaned as well.
•
Use a gasket scraper to remove debris and gasket residue from gasket mating 22
surfaces as previously discussed. Cleaning gasket surfaces with surface conditioning disks is NOT recommended by vehicle manufacturers.
Cylinder Head Inspection Knowing the specific customer complaint (as discussed earlier) can help you find what you’re looking for when inspecting the cylinder head.
For example, cooling system concerns, like overheating and loss of engine coolant, can in many cases be traced to a warped or cracked cylinder head. Oil consumption complaints can sometimes be traced to worn valves and guides. Misfire and power loss complaints are sometimes caused by burned valves that cannot keep the pressure of combustion confined to the inside of the cylinder. In addition, you may find that in some cases that replacing cracked, worn, or high-mileage cylinder heads with new or reconditioned heads makes the most economic sense for the vehicle owner.
23
Warpage Check Check the head gasket surface for warpage using a precision straightedge and a set of thin feeler gauges. Check the head gasket surface lengthwise and crosswise in several places. As a general guideline, warpage lengthwise should not measure more than .003 in. (0.076 mm) for a three cylinder (V6) head, .004 in. (0.102 mm) for a four cylinder or V8 head, or .006 in. (0.152 mm) for a straight six head. When measuring side-to-side, the maximum allowable limit for warpage for any head is . 002 in. (.05 mm) •
Manufacturer’s specific specifications for warpage should be followed to the letter. The figures given here are general guidelines.
If a cylinder head is warped, it should be straightened before any other machine work is done. This is typically a job that most shops will sublet out to an automotive machine shop. Some heads can be milled (shaved down) to make the gasket sealing surfaces flat and true again. Overhead cam cylinder heads are sometimes straightened by bolting the head down over shims to a straightening fixture. The head and fixture are then heated in an oven to 450 to 500 deg. F (230 to 260 deg. C) for three to six hours. The assembly is then cooled slowly to “de-stress” the 24
metal.
Black Lines = Straight edge Positions for Warpage Check Disassembly and Visual Inspection for Cracks After checking for warpage, a close visual inspection should also be made for hairline cracks in the combustion chambers, ports, face, sides and top of the head. Be sure to examine the spark plug, glow plug and/or injector holes for damaged threads and cracks. Look closely around the head bolt holes for cracks and evidence of coolant leakage. Many cracks can be very difficult to see. Keep in mind that there may be cracks that aren’t visible even under close scrutiny.
If a crack is found, don’t do anything else to the head until it is determined if the crack is repairable. In most cases, a cracked cylinder head will need to be replaced.
If no cracks are found after a close visual inspection, the valves and springs can be disassembled. Make sure to mark and record the location of each valve as it is removed.
The tips of the valve stems may have become mushroomed or enlarged from being pounded by the rocker arms. This can happen after an engine has been run for long periods of time with excessive valve clearance.
25
GENRAL SERIVES STEPS :Emptying of components Components should be emptied as much as possible before dismantling commences. Some drain locations may become easier to access later during the work. See below for the components that are involved, although these are not in any particular order. For more detailed information and working instructions refer to the other service information in the respective groups from 1 to 9. Fluids and chemicals shall be handled, separated and stored in a suitable way and in accordance with local legislation and regulations. Engine, oil and filters Drain the engine oil through the drain plug (A). Remove the engine filters; the full flow filter (B) and by filter (C).
Manual gearbox, oil and filter
Drain and empty the gearbox oil through the drain plug 26
Unscrew the oil filter housing and remove the seal and oil filter.
Gearbox with compact retarder, oil filter Remove the oil filter (H) from the oil filter housing. Cover (D), gasket (E), adapter (F) and stay tube (G).
ZF gearbox, oil
Automatic gearbox, oil and filter
Drain the oil by removing the oil sump drain plug (B), and unscrew the oil filters (A).
27
Final drive, oil
Topping-up and drain plugs (A) and (B).
Final drive with hub reduction, oil Topping-up and drain plugs (A and B).
The oil in the hub shall be drained separately.
Retarder, oil
Drain plug (D), topping-up plug (A), vent plug (E).
28
Transfer gearbox, oil
Drain plug (C), topping-up plug (B), level plug (A).
Power take-off, oil draining and filter removal
Drain plug (B), level/topping-up plug (A).
Water separator, filter
Remove the filter.
Driven front axle, oil
Front axle wheel gears. Drain plug (A), level/topping-up plug (B). 29
Front axle differential carrier. Drain plug (B). Urea tank
Remove the filler cap from the urea tank. Remove the drain plug. Empty the urea tank. Note: If urea solution comes into with disconnected electrical connectors, the urea solution spreads rapidly through the wiring and oxidises the metal, which can damage the connectors and cabling.
Urea filter Remove the drain plug and drain the filter housing. Remove the urea filter (A) from the pump unit. Note: If urea solution comes into with disconnected electrical connectors, the urea solution spreads rapidly through the wiring and oxidises the metal, which can damage the connectors and cabling. 30
Fuel tank
Empty the tank by removing the drain plug.
31
BREAKS: Supply System Components
The Air Compressor pumps air into the air tanks supplying the compressed air to power the air brake system and other air operated devices such as the water tank, Tire Boss, chute lock, tilt hopper, etc. It is lubricated by engine oil and is usually gear driven. The Air Compressor Governor controls when the air compressor will pump air into the tanks. When air tank pressure rises to the set maximum, or the “cut out” level, (around 125 psi) the governor stops the compressor from pumping air. When the tank pressure falls to the “cut in” pressure (around 100 psi), the governor allows the compressor to start pumping again. An Air Dryer helps to keep the system free of contaminants. A filter, typically containing a desiccant, is installed between the compressor and air tank to remove moisture and oil from the air. Air Tanks store compressed air. The tanks will hold enough air to allow the brakes to be used several times even if the compressor stops working. The tractors supply air tank receives air from the compressor and delivers it to the primary and secondary air tanks. The tank closest to the compressor is commonly referred to as the “wet tank” because that is where most moisture condenses.
32
Drain Valves manually or automatically purge the air tanks. Compressed air usually has some water and oil in it, which tends to collect in the bottom of the tank. The water can freeze in cold weather and lead to brake failure. Do not depend on the automatic drain valve – Manually drain the air tanks at the end of each driving day. The Air Supply Gauge on the dash indicates how much pressure is in the air tank. Note - Brakes out of adjustment are the #1 violation at weigh stations and the leading cause of braking inefficiency in an air brake system. The manual adjustment of an automatic slack adjuster to bring a brake pushrod stroke within legal limits is masking a mechanical problem and not fixing it. The manual adjustment should only be used as a temporary measure to correct the adjustment in an emergency situation as it is likely the brake will soon be back out of adjustment. Manual adjustment of slack adjusters is dangerous because it can give the operator a false sense of security about the effectiveness of the braking system.
33
Air Brake Test Ensuring the brakes are in peak operating condition is easily the single most important part of your truck inspection – Your life and the lives of others depend on being able to stop when you need to. The below guide will help you develop a proper routine when completing the daily safety inspection of your mixer truck.
Titan Air Brake Test Procedures The test must begin with the following assumptions: • •
Air tanks were drained during the previous post trip. Drain valves are closed. Tire Boss equipped trucks - Wheel valves closed. Reopen the wheel valves upon completion of the brake test to allow the system to inflate/deflate as needed.
34
Air Compressor Build Rate : •
Start the engine and allow the air pressure to increase to 85 PSI. When the air pressure gauge reaches 85 PSI, adjust the engine speed to 900 RPMS.
•
To satisfy this check, the air pressure must reach 100 PSI within 2 minutes
Air Leak Test: Before starting this check, the air system must be at full system pressure which is usually between 125-140 PSI. Rev the engine to 1200-1400 RPMS and watch the air pressure gauge. When the air system is fully pressurized, the pressure gauge will stop climbing and the compressor governor will kick out followed by a “psssst” air release. Complete the following steps: •
Release parking brake
•
Shut off engine
•
Depress the brake pedal as you would in an emergency situation and hold the pedal down for the count of one minute.
•
After the initial drop in air pressure from depressing the brake pedal, the truck must not lose any air as detected by hearing or movement of the air pressure gauge.
35
Low Air Warning: •
Turn the key to the RUN position – Do not start the engine
•
Fan the brake pedal off and watch the air pressure gauge. The low air warning light on the dash and the buzzer must sound before the air pressure reaches 60 PSI.
Emergency Brake Pop Out :
Turn off the key to stop the low air warning buzzer
36
Fan the brake pedal while watching the parking brake knob. The knob must pop out before all of the air is bled from the system – Usually about 20 PSI.
Brake Hold or Tug Test: -
Manual transmission – Start the truck. With the parking brake set, and your foot off the throttle, slowly release the clutch. If the brakes are working properly, the truck should not move. utomatic transmission Start and rev the engine to 1200-1400 RPMs untilthe air pressure gauge reads at least 100 PSI. Drive forward at 3-5 MPH and set the parking brake. The truck should quickly come to stop.
Ashoka Layland Gearing System 37
38
No. of Gear and Size
GEAR DRIVE TO PARLLER SHAFT 39
40
41
42
43
44
45
46
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