TOPIC 1 CLUTCH COMPONENT
Learning OutcomeYou will be able to describe the operation and identify the components of a mechanical clutch system.
Assessment Criteria
The student will explain correctly and identify:
• Purpose of a clutch
• Types single and multiple disc clutches
• Basic operation of clutch assembly : flywheel face, clutch disc, Pressure plate assembly
• Clutch mechanical lever
Clutch mechanical and hydraulic controls.
TOPIC 1
CLUTCHES
Clutches are devices which are used to engage (connect) and disengage (disconnect) one mechanical part from another. In a motor vehicle with a manual transmission or a manual transaxle, the clutch is used by the driver to engage and disengage the engine from the transmission. Automatic transmissions also have clutches, but they are engaged and disengaged automatically.The clutches covered in this topic are those used with passenger and light commercial vehicles which have manual transmissions or transaxles.
Purpose of the Clutch
An internal-combustion engine needs a clutch because it has to be started and running at speed before a load can be applied.
The clutch performs the following functions:
1. With the vehicle stationary, the clutch is used to disconnect the engine from the transmission, so that low or reverse gear can be selected.
2. The clutch allows the load to be applied to the engine gradually as it is being engaged, so that the vehicle moves off steadily.
3. When the vehicle is moving forwards, the clutch is disengaged and engaged by the driver whenever gearshifts are to be made.
As well as operating smoothly, the clutch must hold firmly once it is engaged, because all the torque from the engine is carried through the clutch to the transmission.
Transmission
Types of clutches
There are various types of clutches including cone clutches, dog clutches, wet clutches and dry clutches. All these have automotive applications in one form or another, but the single-disc clutch is the design which is used for the transmission clutch in most motor vehicles.
The are two types of the clutches
1. Single-disc (or single-plate) clutch can be seen in in drawing below.
The main parts of a single-disc (or single-plate) clutch.
2. Multiplate clutches, as their name suggests, have two or more plates. Clutches of this design are used automatic transmissions, motor cycles and heavy mechanical equipment.Note that the terms disc and plate are inter- changeable-both names are commonly used
A coil-spring clutch with two friction disks and an intermediate drive Plate.
• Automatic transmissions clutches operate wet, being enclosed within the transmission case and lubricated with automatic transmission fluid.
Clutches for heavy vehicles may have two clutch plates or discs to carry the high torque that has to be transmitted by the clutch. These are referred to as dual-disc clutches.
Clutch assembly
A single-disc or multi-disc-clutch assembly consists of main parts. These are:
1. The rear face of the flywheel - the driving member;
2. The clutch disc - the driven member;
3. The pressure plate assembly - also a driving member;
4. The release mechanism - disengages and engages the clutch
5. Clutch control.
As well as this, there are the clutch controls between the clutch pedal and the release mechanism. The functions of these parts are as follows.
The clutch components including the release mechanism.
Flywheel face
The rear of the flywheel has a machined surface to which the pressure plate assembly is bolted. The flywheel provides a flat face for the clutch disc, which is held against it by the pressure plate. Some flywheels are flat; other are recessed so that the clutch is mounted into the flywheel rather than onto the flywheel face.
Clutch disc
The clutch disc is splined to the transmission input shaft so that it carries the torque from the engine to the transmission when the clutch is engaged, but remains stationary and so transmits no torque when the clutch is disengaged. It is held between the flywheel face and the pressure plate face by spring force
The disc carries facings of asbestos-composition material, so that a high-friction effect will be obtained between the cast iron surfaces of the
flywheel and the pressure plate. For this reason, this type of clutch is sometimes referred to as a friction clutch, and the disc as a friction disc
The splined hub of the disc is not attached directly to the disc itself, but is mounted on a flange which is connected to the disc by a number of heavy coil springs. These act as a dampening device between the disc and the hub to absorb any torsional (twisting) vibrations from the engine.
Parts of a clutch disc
The hub of the disc is therefore driven through the damper springs, although stops limit the movement between the flange of the hub and the disc. As well as this, a moulded friction washers, between the hub flange and the drive washers of the disc, acts as a dampened.
A cushioning device provides for smooth clutch engagement. The outer part of the disc is slotted and 'waved' to form cushion springs. This is the part of the disc to which the facings are riveted. The waves keep the facings spread slightly when the disc is disengaged. They compress as the clutch is being engaged to provide a cushioning effect and smooth engagement
Partially cutaway coil-spring clutch.
Clutch Disc Components
Clutch bearings
There are two bearings associated with the clutch
the clutch release bearing and the clutch pilot bearing.
Clutch release bearing
A clutch release bearing is a thrust-type bearing. The bearing carrier, in most cases, has a groove for the clutch release fork. Clutch release bearings are packed with lubricant during manufacture and generally cannot be lubricated in service. The bearing shown is an angular-contact bearing, which is designed to take a thrust load but which will also accept some radial load.
Section through a clutch bearing
Clutch pilot bearing
The transmission input shaft, sometimes called the clutch shaft because it carries the clutch disc, has splines on which the clutch disc is mounted. The input shaft is carried by a bearing in the transmission housing, but its outer end is supported in a small bearing in the end of the crankshaft. This bearing is known as a pilot bearing, and the small end of the shaft that fits into the bearing is called a spigot. In the drawing below is a sectional view of a clutch assembly which identifies the parts, including the pilot bearing, which is a small ballrace.
Transmissions for rear wheel drive vehicles need a pilot bearing to support the end of the shaft and help carry the mass of the clutch disc. However, all transaxles do not have a pilot bearing. These transaxles have their input shaft more rightly supported in the transaxle housing and so a pilot bearing is not needed.
Section view of a clutch assembly
Ball bearings, rollers and bronze bushes are all used for pilot bearings. Ball bearings are sealed on one or both sides and are lubricated during manufacture. Bronze bushes are usually of sintered bronze with some self-lubricating properties, and are also porous enough to retain lubricant.Pressure Plate
Pressure plate assembly
The pressure plate assembly has a spring-loaded pressure plate which holds the clutch disc firmly against the flywheel. There are two types: pressure plates with a diaphragm spring and pressure plates with coil springs. They both perform the same function. Release levers, or fingers, allow the spring force to be relieved when the clutch is disengaged.
Diaphragm spring clutch
A diaphragm pressure-plate assembly, together with its disc, is shown in Figure 4. This consists of the pressed - steel cover, the diaphragm spring and three straps, or retracting springs. Pressure.
plates of this type are not normally dismantled, and are serviced as an assembly.
Diaphragm pressure-plate assembly and clutch disc
The drawing below is an exploded view of a pressure plate of slightly different design. The exploded view enables the construction to be seen. The diaphragm is located between two pivot rings.
Exploded view of a diaphragm clutch assembly
The diaphragm is a spring steel disc which is slightly coned. It is slotted to form a number of fingers. It not only provides the spring force for the pressure plate, but the fingers form part of the release mechanism.Diaphragm clutch features
Diaphragm clutches are the most commonly used on passenger cars and light commercial vehicles.
One of the features of this clutch is that the spring action of the diaphragm actually becomes easier as the finger are depressed. This provides the driver with a very 'soft' clutch which is easy to operate.
Clutches with coil springs (see next heading ) have the opposite effect because the resistance of the springs increases as they are being compressed. This tends to give a 'hard' clutch pedal, so an assist spring is often fitted to the clutch pedal to make the clutch easier to depress
Coil spring clutch
Coil spring clutches use a number of coil springs between the pressure plate cover and the pressure plate to hold the pressure plate against the clutch disc. A pressure plate assembly of this design is shown in diagram below. It consists of the following parts.
Clutch pressure-plate assembly
1. Pressure plate. This is made of cast iron, with mounting bosses for the coil springs and driving lugs which fit into holes in the cover.
2. Coil springs. There may be from three to twelve of these depending on the particular application for which the clutch is used. Only one spring is shown in the illustration.
3. Cover. This retains the springs against the pressure plate. It is of pressed-steel construction and is provided with a flange which enables the pressure plate assembly to be bolted to the flywheel.
4. Operating mechanism. This includes the release levers, the release lever springs, eyebolts, struts and pins. Three of each of these parts are used, although only one of each is shown in the figure.
Basic Operation of pressure plate assembly
The action of the pressure plate assembly is as follows. When the clutch is operated by depressing the clutch pedal, the release levers are moved inwards by the release bearing. This action pivots the release levers on the pins and against the struts.
Coil –spring clutch in the disengaged position
The struts force against their supports under the driving lugs of the pressure plate to compress the springs and move the pressure plate away from the clutch disc so that it is released.Release mechanism
The release mechanism consists of a release fork which pivots on a ball stud when the clutch is being operated. The forked end of the lever carries the release bearing which operates against the fingers of the pressure plate.
The release mechanism consists of the release fork (also called the release lever) and the release bearing. The release bearing is mounted on a hub which slides on a sleeve on the front of the transmission.
When the clutch is being disengaged, the release fork pivots on the ball stud which is mounted on the clutch housing. The release bearing presses the fingers down to release the disc.
Clutch engaged and Clutch disengaged
When the clutch is engaged, the diaphragm spring holds the pressure plate firmly against the disc so that it can carry the torque from the engine to the transmission.Other release mechanisms
There are other arrangements of release mechanisms. One of these is shown in Figure 8. This has a shaft mounted in bushings in the flywheel housing. The shaft carries the release fork, which operates the clutch release bearing. A return spring is fitted to the shaft to keep the release bearing away from the fingers of the diaphragm when the clutch is not being used
Clutch Control
There are two types of clutch controls are used to transfer movement from the clutch pedal to the clutch release fork
1. Mechanical clutch controls.
2. Hydraulics clutch controls.
Mechanical clutch controls
The clutch is controlled from the driver's clutch pedal by a control cable, or by control linkage. Whatever the arrangement, its purpose is to transfer movement from the clutch pedal to the clutch release fork.
When the driver pushes the clutch pedal down, the spring force against the pressure plate is released and the clutch is disengaged. When the clutch pedal is returned to its normal position, the spring force is again applied and the clutch is engaged.
• Control Cable
The drawing illustrates a cable-operated clutch control for a front wheel drive vehicle
Clutch with control cable
The control cable is connected between the upper end of the clutch pedal and an external lever on top of the clutch housing. This lever is, in turn, connected to a vertical shaft attached to the release fork inside the clutch housing. The cable is provided with an adjustment at the clutch end.
The release fork carries the release bearing which thrusts against the diaphragm fingers when the clutch is operated. The cable adjustment provides a small amount of free play so that the release bearing is not in constant contact with the diaphragm fingers.
Clutch linkage
Linkage arrangements operate in the same manner as control cables. In passenger vehicles, cables have replaced linkages because of their greater flexibility. The flexibility of the cable absorbs engine movement that might otherwise be transmitted
through linkage, which would be less flexible. Also, from a design point of view, the cable is easier to install in the vehicle
Hydraulic clutch controls
The components of a hydraulically controlled clutch are illustrated in drawing below. The arrangement consists of a master cylinder operated by the clutch pedal, with a hydraulic pipe and flexible hose connecting it to a slave cylinder mounted on the clutch housing. The clutch release fork is operated by the slave cylinder
Movement of the clutch pedal by the driver causes hydraulic fluid to be displaced by the master cylinder piston into the slave cylinder. This causes the slave cylinder piston to move in its bore. The
movements then transferred by a pushrod to the clutch release fork to operate the clutch mechanism and so disengage the clutch.
• Master cylinder parts and basic operation
The drawing below is illustrates the parts of a master cylinder of the centre valve type, so named because of its particular design of valve
Part of a centre-valve master cylinder
The piston is fitted with a primary seal and a secondary seal. The valve assembly consists of a seal fitted to the end of the stemThe drawing below is a section view of the assembled cylinder. This shows the location of the piston and associated parts in the cylinder bore
and identifies the two fluid ports: the inlet port in the end of the cylinder, and the outlet port located on top of the master cylinder.
Section view of a centre-valve master cylinder showing the piston assembly in the cylinder
Slave cylinder
Slave cylinders are of much simpler design than master cylinders. They consists basically of a cylinder which when the clutch pedal is depressed forces the slave cylinder piston along its bore. Piston movement is transferred through the pushrod to the end of the clutch release fork to operate the clutch
A slave cylinder and its component parts are shown below.
Parts of a slave cylinder; the assembled cylinder is also shown
There are many variations of the components illustrated, although centre valve type master cylinders are usually used in clutch hydraulic systems. The diagram below is illustrates one of these which has a piston assembly of slightly different design to the on previously shown
Clutch master-cylinder assembly
The reservoir, which is attached to the cylinder by a bolt, is made from transparent material so that the fluid level can be easily checked. In some light commercial vehicles, the reservoir is remote from the master cylinder and connected to it by flexible hoseThe pushrod and the clevis which attaches the rod to the clutch pedal are also shown in the illustration. The clevis is threaded to the pushrod and this provides an adjustment for the rod length.
Written Activity 2
Answer all of the following questions.
1. What is the purpose of a clutch?
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2. What does the clutch do in a motor car?
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3. What are the four which a clutch performs?
1. -------------------------------------
2. ------------------------------------
3. -------------------
4. ------------------------------------
4. What the two types of the mechanical clutches on a vehicles?
1. ----------------------
2. ----------------------
5. Name the parts in the following diagram.
6. What does the clutch disc do?
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7. What is the function of the clutch pressure plate?
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8. Name two type of pressure plates.
1.-------------------------
2. -----------------------
9. What are the two type of clutch controls?
1. ------------------------
2.----------------------
10. What are the two bearings found in a clutch assembly?
1. -------------------
2. ------------------
11. What do clutch controls do?
12. What are the two ways in which pedal movement can be connected to the release fork?
1.-------------------------
2.-----------------------
13. What are the names of the two cylinders in a hydraulic clutch system?
Practical Activity 1
1. For this activity you will be required to identify the basic components of a clutch assembly and to then identify them on a workshop vehicle.
1.1 Component identification Identify for your trainer:
• A flywheel and pilot bearing
• A clutch plate
• A pressure plate assembly
• Release fork
• A clutch housing
1.2 Name the parts of a clutch disc plate for your trainer. Identify the following components:
• Splined hub
• Splashed facings
• Drive washer
• Cushion springs
1.3 Explain to your trainer how the components fit together and operate.
2. You are now required to examine a cut away model of a clutch system on a training workshop. On the vehicle identify all of the components from section 1. When you are confident that you can trace the operation of the system and explain it, have your trainer check you.
TOPIC2
FLUID COUPLINGS/TORQUE CONVERTERS..
You will be able to describe the operation of a fluid coupling and identify the basic components of a system.
Assessment Criteria
You will explain correctly and identify:
• The purpose and principle of fluid coupling
• Torque converters parts: Impeller, Turbine, Stator
• Torque converter - operation
• Torque multiplication
• Lock up clutches.
TOPIC2
FLUID COUPLINGS AND TORQUE CONVERTERS
IntroductionA powershift or automatic transmission does away with all the clutch and gearshift operations that are normally carried out by the driver of a vehicle with manual transmission. As well as powershift or automatic gearshifts. The transmission has a fluid coupling/ torque converter which acts as a fluid coupling.
This topic will provide an introduction to fluid coupling and torque converter.
There are two basic types of hydraulic couplings: those that transmit torque, and those that not only transmit torque, but also increase torque. The latter are referred to as torque converters
External parts of an automatic transmission
Fluid CouplingA simple fluid coupling can be made with two electric fans as shown in drawing below. The air from one fan energized causes the blades of the other fan disenergized to rotate. In this case, the air is no the fluid, and because the fans are not enclosed, much of the air escapes and the coupling is not very efficient
Two fans can from a simple fluid coupling
A fluid coupling is more efficient than the simple fan coupling. It has two members with vanes or blades. The members are mounted close together in a housing and are partly filled with oil, which is the coupling fluid. One member is the driving member and the other is the driven member.
Simplified version of two members of a fluid coupling
When the driving member of the fluid coupling is rotated, it throws oil against the driven member causing it to rotate. In this way, torque is transmitted through the coupling. However, this is still not a very efficient coupling because there is a great deal of turbulence in the oil and this tends to oppose rotation of the driven member.
Fluid coupling in action; oil is thrown from the driving member into the driven member
Both fluid couplings and torque converters have a driving member and a driven member, and they both transmit torque through oil thrown from the blades of one member to the other. However, the fluid coupling only transmits maximum torque when both its members are rotating at the same speed. This not the case with a torque converter.
When the driving member of a fluid coupling turns faster than the driven member, oil thrown onto the driven member bounces back against the driving member and opposes rotation. When there is a big difference in speed between the two members, a large part of the driving torque is used to overcome this, causing a torque loss.
With a torque converter, which has an extra member, the torque is not reduced; instead, the torque is increased.
Torque converter construction
A torque converter is shown in illustration. It has a pressed steel housing welded to a front cover. It is made as an assembly and is not designed to be dismantled, except with special facilities, a torque converter can be opened up for repair/
Torque converter, external view
The cover has three or four bosses, or raised parts (which are bolted to the drive plate, which in turn is bolted or splined to the flywheel. When the engine is running, the complete torque converter rotates with the crankshaft. The engine does not have a conventional flywheel, but has the drive plate or spline and torque converter instead.
Torque converter drive plate
Fiywheel
A torque converter is a particular type of hydraulic coupling which has three main parts and function, These are as follows:
1. Impeller. This is the driving member, which is rotated by the engine.
2. Turbine. This is the driven member, which is driven by fluid from the impeller. The driven member is attached to the input shaft of the transmission
3. Stator. This is mounted on a stationary shaft to enable the oil from turbine some return back to impeller and some to the oil cooler or tank.
Parts of a torque converter
All three main parts are enclosed within the converter housing and cover. The converter operates completely full of oil.The parts of the converter are shown in simple form.
1. The drawing shows the impeller, which has blades attached to the inside of the converter housing. As the impeller rotates, oil is thrown outwards by the blades. The impeller is sometimes referred to as a pump because it has a pumping action.
2. The drawing shows the turbine and the impeller. The turbine is connected to the input shaft of the gear section of the transmission. The turbine is driven by fluid from the impeller. The fluid strikes the turbine blades and then flows inwards to the centre of the converter.
3. The drawing shows a stator added to the other two parts. It is mounted on fixed shaft (the stator shaft) on a one way clutch. This allows the stator to run in one direction, but locks automatically to prevent the stator from turning in the opposite direction. The flow of fluid is as shown from the impeller to the turbine and then to the stator.
Torque converter construction
Torque converter operationThe torque converter acts like a variable gear ratio. It can transmit torque at a 1:1 ratio, or under certain conditions, it can increase (or multiply) torque so that more torque is delivered than is received. Maximum torque multiplication is about 2:1, so having a torque converter is like having extra gears with a2:1 ratio.
With gears, speed reduction means torque increase. This also applies to a torque converter, where speed reduction within the converter means an increase in torque. Torque multiplication is achieved by the action of the stator and the way in which fluid flows in the converter.
Fluid flow in the converter
The drawing shows the fluid flow from the impeller to the turbine through the stator and back to the impeller
NOTE : The oil flow in the torque converter is called Velocity.
Fiuid fiow in the converter
When the converter is rotating, fluid flow is as follows:
1. Fluid is thrown outwards in the impeller as a result of centrifugal force. The impeller blades
direct the fluid from the impeller into the turbine, causing the turbine to turn.
2. Fluid entering the turbine is directed from the outside towards the centre, and because of the curved blades, the fluid leaves the centre of the turbine in the opposite direction to that which it enters.
3. Fluid from the center of the turbine is directed onto the blades of the stator.
4. The direction of the fluid is again changed by the curved stator blades so that it enters the impeller in the direction in which the impeller is rotating. The force of fluid therefore acts on the rear face of the impeller blades, assisting with rotation.
5. The fluid is again thrown from the outside of the impeller into the turbine to repeat the cycle.
It can be seen that the stator and the shape of its blades are the key to torque converter operation. This is further illustrated in drawing, which shows how the oil flows through the stator and the turbine. This is the basic principle of torque multiplication. If the oil flow were not redirected by the stator blades, it would work against the impeller blades and oppose rotation This would cause a torque loss instead of a torque increase.
Fiuid fiow through the turbine and stator
Rotary and vortex flowFluid flow in the torque converter is in two different directions:
1. Rotary flow. The fluid is carried around in a rotary direction with rotation of the impeller.
2. Vortex, or spiral flow. The fluid is circulated in a spiral direction through the passages between the blades of the three members of the converter.
Fiuid fiow through the turbine and stator
Torque multiplication
With the selector lever in Drive position, and the engine idling, the fluid in the converter does not leave the impeller blades with enough force to turn the turbine, and so the vehicle does not move there is no torque multiplication.
However, when the throttle is opened fully and the vehicle is about to move, the impeller will be rotating and the turbine will not. Oil will be thrown into the turbine with great force and there will be maximum torque multiplication. (This will depend on whether the vehicle is level or on an incline.)
Coupling point
At coupling point, there is no torque increase and the converter acts simply as a fluid coupling
Coupling point occurs when the turbine speed reaches approximately 90 per cent of the impeller speed.
Stator and one-way clutch action
The function of the one-way clutch is therefore to prevent power loss within the converter. This would be caused by oil dragging against the stator if were fixed and could not rate when not needed
Lock-up torque converters
Some torque converters are fitted with a clutch. These are referred to as lock-up converters. Converter action is needed in the lower gears and at lower speeds, but is not needed for light load and cruising conditions. Under these conditions, the converter is locked with the clutch to prevent converter 'slip'. This conserves engine power A simplified arrangement is shown in drawing.
The clutch is a disc located within the converter in front of the turbine and attached to the turbine hub. With the converter unlocked, the friction material is clear of the converter in the normal way.
Simpiified arrangement of a converter with a iock-up ciutch
Lock- up ConstructionThe drawing below shows a section through a lock-up torque converter. The lock-up clutch consists of a large piston which is free to move on the turbine hub, and the clutch plate. The centre of the clutch plate is attached to the turbine hub and also to the outer edge of the piston through damper springs. With the clutch applied, drive is transmitted directly from the front cover through the clutch plate to the input shaft
Torque converter with a iock-up ciutch
The pressure in the converter and the direction flow are used to apply and release the clutch
Written Activity 2
Answer all of the following questions.
1. What are the three basic sections of a trorque converter?
---------------------------------------------
2. Name the parts shown on the following diagram
3. What is the primary function of torque converter?
--------------------------------------------------------
4. What are the two basic types of Hydraulic couplings?
1. ---------------------------------------------
2. --------------------------------------------
5. Describe very briefly how a fluid coupling operates
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6. When does a simple torque converter transmit maximum torque?
--------------------------------------------------
7. Name the parts of the following diagram
7. In a torque converter what is the function of the following components?
a. Impeller
b. Turbine.
c. Stator.
8. Can a torque converter increase torque?
If so, up to what ratio
9. What part of the torque converter causes torque multiplication?
-------------------------------------------------------------------------
10. What is coupling point?
----------------------------------------------------
10. What prevents the stator from rotating backwards below coupling point?
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11. What is the difference between a fluid coupling and a torque converter?
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KEY ANSWER FOR WRITTEN ACTIVITY
TOPIC 1 CLUTCH COMPONENT
Written Activity 1
Information which will help you answer these question can be found on the previous page or from what you learned in your previous topic.
1. What is the learning outcome of this topic?
Student will be able to describe basic operation and identify the components of a mechanical clutch system.
2. What are the five things you must be able to explain to pass this topic?
1. The purpose of a clutch.
2. Type of clutch (Single and multiple plate clutches)
3. Basic operation of Clutch
4. Clutch mechanical lever.
5. Clutch hydraulics controls
Written Activity 2
Answer all of the following questions.
1. What is the purpose of a clutch?
Connects (engage/connect and disengge/disconnects are mechanical part to another.
2. What does the clutch do in a motor car?
Engage and disengages the transmission from the engine in a motor car
3. What are the four which a car clutch performs?
1. Disconnects the engine from transmission, so that low or reverse gear can be selected.
2. Allows the load to be Applied to the engine gradually as it is being engaged, so that the vehicle moves off steadely.
3. When the vehicle is moving forwards, the clutch is disengaged and engaged by the driver whenever gearshifts are to be made.
4. Must hold firmly once it is engaged, because all the torque from the engine is caaried through the clutc to the transmission.
4. What the two types of the mechanical clutches on a vehicle?
Single disc (single plate) clutch Multi disc (multi plate) clutch
5. Name the parts in the following diagram
6. What does the clutch disc do?
Carries the drive or torque from the flywheel to the transmission
7. What is the function of the clutch pressure plate?
To hold the clutch disc firmly against to the flywheel.
8. Name four (2) type of pressure plates.
1. Pressure plates with a diaphragm
2. Pressure plates with the coil spring
9. What are the two type of clutch controls?
1. Mechanical
2. hydraulic
10. What are the two bearings found in a clutch assembly?
1. Clutch release
2. Clutch pilot
11. What do clutch controls do?
Transfer movement from the clutch pedal to the clutch release fork.
12. What are the two ways in which pedal movement can be connected to the assembly?
1. Mechanical – cables
2. Hydraulic
13. What are the names of the two cylinders in a hydraulic clutch system?
Master Cylinder Slave Cylinder
Practical Activity 1
1. For this activity you will be required to identify the basic components of a clutch assembly and to then identify them on a workshop vehicle.
1.1 Component identification Identify for your trainer:
• A flywheel
• A clutch plate
• A pressure plate assembly
• Release fork and heavy
• A clutch housing
1.2 Name the parts of a clutch disc plate for your trainer. Identify:
• Splined hub
• Facings
• Drive washer
• Cushion springs
1.3 Explain to your trainer how the components fit together and operate.
You are now required to examine a cut away model of a clutch system on a workshop vehicle. On the vehicle identify all of the components from section 1. When you are confident that you can trace the operation of the system and explain it, have your trainer check you
TOPIC 2
FLUID COUPLINGS/TORQUE CONVERTERS
Written Activity 1Information which will help you answer these question may be found on the previous page or have been learned in the previous unit.
1. What is the learning outcome of this topic?
Describe the operation of a fluid coupling and identify the basic components of system
2. What are the five things which you will learn in this topic?
1. The pupose and principle of fluid coupling
2. Torque converterparts
3. Torque converter operation
4. Torque multiplication
5. Lock up clutches.
Written Activity 2
Answer all of the following questions.
1. What are the three basic sections of a torque converte?
Impellr
Turbine
Stator
2. Name the parts shown on the following diagram.
3. What is the primary function of torque converter?
Torque converter acts like variable gear ratio, it can transmit torque at 1 : 1 ratio, or multiflies torque
4. What are the two basic types of hydraulics coupling?
1. Those that transmit torque - fluid coupling.
2. Those that transmit and increase torque - torque converter.
5. Describe very briefly how a fluid coupling operates.
Students need to mention (1) driving member (2) driven member (3) fluid
6. When does a simple fluid coupling transmit maximum torque?
When both members are rotating at the same speed.
7. Name the parts of the following diagram
8. In a torque converter what is funtion of the following components?
a. Impeller Throws or pumps oil onto the turbine.
b. Turbine Is driven (rotates) by the oil force from the Impeller - transmits force to the transmission
c. Stator Directs the oil from the turbine back to the impeller - increases torque
9. Can a torque converter increase torque? Yes
If so, by up to what ratio 2 : 1
10. What part of the torque converter causes torque multiplication?
Stator
11. What is coupling point?
When impeller and turbine speeds are about same or there is no torque increase.
12. What prevents the stator from rotating backwards below coupling point?
One - way clutch
13. What is the difference between a fluid coupling and a torque converter?
Fluid coupling does not multiply torque, fluid coupling only transmits torque, torque converter increase torque.
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