FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION Clutch system for vehicle
APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Mr. Deepak R R
Indian nationals
of TATA MOTORS LIMITED,
An Indian company having its registered office
At Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is
performed.

FIELD OF INVENTION
This invention relates to clutch system of automobile and more particularly clutch cover assembly which will clamp the clutch disc by means of fluid pressure instead of the force exerted by diaphragm spring in case of existing clutch cover.
BACKGROUND OF INVENTION
The clutch is a subcomponent of the transmission that is designed to engage and disengage power flow between the engine and the transmission whenever desired by driver. The clutch allows us to smoothly engage a spinning engine to a non-spinning transmission by controlling the slippage between them. The clutch system has Clutch Cover assembly consisting of a Pressure plate, diaphragm spring, friction drive straps, Disc: The disc is a critical component consisting of friction liner, cushion segment, torsions dampening springs, friction washers. It is mounted to the input shaft between the flywheel and the clutch. The actuation system may be linkage type, cables type, hydraulics type. Finally comes the pedal on which the force is applied and released in order to release and engage the clutch.
The clutch which acts as a fuse between the engine and the transmission has to undergo a variety of load variation and duty cycle in its life time .With the present advancement in the field of automobile, with the need for development of highly efficient, high power engines. The power from the engines is transmitted down the line to gear box by means of clutch. The clutch should be capable enough to transmit this power. In order to transmit this power, the clutch is associated with certain parameters while designing. The important factors that is considered in designing, is the coefficient of friction of the liner material of the clutch, Diameter of the clutch and clamp load. Since compactness is the trend of the present scenario, increase of diameter will bulge the whole transmission

system. Also, friction coefficient of the liner material has its own limitations based on application and cost. The only factor which can be varied is the clamp load. By increasing the clamp load the torque carrying capacity of the clutch can be increased. But when clamp load is changed it directly affects the release load. The release load is the load applied on the clutch in order to disengage/release the clutch. The disengagement of the clutch is done either mechanically or through hydraulic means, which final gets connected to the clutch pedal. Therefore the final outcome is the effort on the pedal and with the increase in the clamp load the effort also tends to increase.
US20090036249 (Dl) discloses about a plurality of passageways in the body portion extended through the flywheel. Each of the plurality of passageways is adapted to receive a flow of lubricant spilling onto the driver-side of the body portion when the flywheel is rotating, and to expel lubricant out of the driven-side face of the body portion. The fluid is routed to the driven surface at the flywheel clutch interface for lubrication whereas in the present invention an annular area is enclosed and does not have any way for the fluid to pass onto the clutch liner surface. The present invention is for clutch actuation and not for clutch lubrication as in D1.
US 4,664,240 discloses about a friction clutch operated by a fluid pressure that overcomes the deficiency of wearing of the friction liners. A friction clutch comprises double stationary annular cavity, piston, two bearings etc. The flywheel is not fixed to the engine shaft and it is floating. There is no any rotary joint and safety features are present in D2. Whereas the present invention comprises single rotary annular cavity, single annulus piston, rotary joint placed on the crankshaft behind the flywheel etc. No bearing is required for releasing of the clutch system due to available rotary joint in present invention. Additional safety valve is provided on the clutch housing engine interface, on removal or little movement of the clutch housing bolt the power supply to the annulus piston is cut-off.

Now a days, most of the vehicle is modified from mechanical transmission (MT) to automated manual transmission (AMT) during this automation the clutch plays an important role in managing smooth engagement. The smooth engagement of the diaphragm clutch by means of an actuator is not so easy because of the non linearity in the clamp load with respect to the travel of the diaphragm finger further amplified along the clutch pedal lead to uneven torque transmission. This makes the logic of the transmission control unit (TCU) complicated. The simple logic integration would be load based where in the travel and the clamp load followed by the torque transmitted would have linear relation but, this is only possible if the clamp load is linear to the diaphragm finger travel. But the diaphragm clutch need to have travel based logic control, which is complex and there need to be auto correction in the logic to respond to clutch disc wear over number of operations.
Also during clutch disengaging and engaging there is tremendous pressure on the engine crankshaft bearing because of the tremendous load coming on due to clutch release system. The various drawbacks associated with the existing methods are mention below.
- Increase in pedal effort found because of the nature of the diaphragm spring.
- Clamping load on the disc varies with the clutch disc wear.
- Lesser clutch disc wear reserve. ■ - Stack up size is bigger.
To resolve these drawbacks stated above the present invention proposes fluid pressure based clamping system instead of the diaphragm, where in, the clamping load is linear with respect to the diaphragm finger travel. The clamping load can be varied by means of regulating the pressure of the fluid. The advantages of present invention over prior arts are as follows:
- The pedal effort is constant through out the life of clutch as compared to existing.
- The stack up size is smaller as compared to existing systems

- Higher wear reserve.
- Easily adoptable on to automated manual transmission because of pressure based control with just replacing the pressure reducing valve, pressure regulating knob and pedal with servo pressure control valve which will be readily available on the Automated Manual transmission module.
OBJECT OF INVENTION
The primary object of present invention is to develop a clutch system which clamps the clutch disc by means of fluid pressure.
Another object of the present invention is to provide an annular cavity in the flywheel for exerting fluid pressure onto the clamping plate.
Yet another object of the present invention is to provide a flywheel mounting plate being provided with inner projection defining pressure plate.
Yet another object of the present invention is to provide safety valve on the clutch housing engine interface.
SUMMARY OF INVENTION
The present invention relates to a clutch system for a vehicle comprises, a flywheel provided with an annular cavity , an internal fluid path provided in said flywheel, said internal fluid path being connected to said annular cavity for transmitting the fluid, a movable clamping plate and sealing means provided at front end of said flywheel for enclosing said annular cavity, a flywheel mounting plate secured circumferentially onto said flywheel, said mounting plate being provided with inner projection defining pressure plate of said clamping plate, the pressure plate is adapted to bear on one face of friction

liner of a clutch disc, the other face of the friction liner being in contiguous relationship with the clamping plate, said movable clamping plate is adapted to clamp friction liners against the pressure plate owing to rise in fluid pressure in said annular cavity, which leads to gradual increase in torque and revolution, transmitted from said rotating flywheel and said flywheel mounting plate to the clutch disc further to gear box input shaft.
According to a preferred embodiment, the flywheel mounting plate is mounted onto the flywheel by fastening means.
Preferably, said clutch disc is held in place, axially with respect to said flywheel by means of gear box input shaft.
Most preferably, said flywheel has internal drilled circumferential fluid path which connects the annular cavity to dynamic seal body for transmitting the fluid.
According to a preferred embodiment, said dynamic seal body consists of fluid seals which come in contact with static seal body mounted onto the engine for transmitting the fluid to the flywheel due to the rotation transmitted from the crank shaft of the engine. The static seal body has an opening for fluid connection which is pneumatically/hydraulically connected to safety cut off valve.
According to another preferred embodiment, said safety cut off valve is designed for cutoff the fluid flow to the fluid seals and to said annular cavity in case of replacing said clutch disc.
Preferably, said movable clamping plate maintains the same amount of clamp load in case of wearing of friction liner as clamp load only depends on the applied fluid pressure. According to a preferred embodiment, said sealing means is high temperature seals, which function is to seal the fluid inside the annular cavity of the flywheel.

According to a preferred embodiment, a pressure regulating valve of the clutch system can be replaced by servo pressure control valve.
According to a preferred embodiment, the flywheel is mounted on engine crank shaft by fastening means, said fastening means is mounting bolts
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 shows the existing clutch system of commercial vehicles.
FIGURE 2 shows a side view of the invention in engaged condition of the clutch, along with showing the connection to a pressure controlling circuit.
FIGURE 3 shows a side view of the invention in disengaged condition of the clutch, along with showing the connection to a pressure controlling circuit.
FIGURE 4 shows a side view of the Invention adoptability for automated manual transmission (AMT)
Description of reference numbers for the major component in the drawings: 1.
2. Flywheel
3. Flywheel Mounting plate
4. Pressure plate
5. Friction Liner
6. Clutch Disc
7. Clutch Disc hub
8. Gear Box input shaft
9. Flywheel mounting bolts

10. Annulus high temperature Seals
11. Movable clamping plate
12. Bolts
13. Static seal body
14. Fluid Seals
15. Dynamic seal body
16. Crank shaft of engine
17. Fluid path
18. Pressurized reservoir
19. Clutch pedal
20. Clutch pedal spring
21. Pressure regulating knob
22. Pressure regulator valve

23. Clutch housing
24. Clutch housing stopper
25. Valve plunger
26. Safety cut off valve
27. Engine block
28. Annular cavity
29. Servo pressure control valve
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to the accompanying drawing, wherein the showings are for the purpose of
illustrating a preferred embodiment of the invention only, and not for the purpose of
limiting the same.
The working of the existing system with respect to fig 1 is as follows:
It consists of a solid flywheel (1) without any cavity. The clutch disc (4) is sandwiched
by the force of the diaphragm spring (5) and it varies with the clutch disc (4) friction liner
wear. The diaphragm spring always holds the clutch in the engaged position by

sandwiching the clutch disc (4) in-between the pressure plate (3) and the flywheel (1) so in this condition the torque and rotation delivered from the flywheel (1) is transmitted to the gear box input shaft (7) by means of clutch disc (4). The clutch disengagement is done by pushing the diaphragm spring finger (not shown) by means of Clutch release bearing (6) further actuated by the release yoke (7) which is fulcrum at point '9' on the clutch housing ( not shown) due to the push force from the Clutch slave cylinder (12). The clutch slave cylinder (12) is actuated by two forces acting on it.
- First force is due to the hydraulic pressure built because of the hydraulic connection between it and the clutch master cylinder (13).
- Second force is due to the force from the booster (11) which is mechanically connected to the clutch slave cylinder (12).
The master cylinder (13) is connected to the clutch pedal (16) mechanically and to a reservoir (14) hydraulically. Now when the pedal (16) is pressed by human foot the pressure built is transmitted to the clutch slave cylinder (12) which is not sufficient hence, the internal arrangement in the booster (11) comes into play and it starts assisting the slave cylinder (12) in disengaging the clutch through release yoke (7) and bearing (6). Similarly on the release of the clutch pedal (16) the pressure drops at the clutch slave cylinder (12) due to the return travel of the piston (not shown) in the master cylinder (13), this is sensed by the booster (11) and it stops assisting the slave cylinder (12) and the clutch gets slowly engaged with respect to clutch pedal (16) travel.
Referring to the accompanying fig 2 and fig 3, the present invention consist of a Flywheel (1) which is mounted on the engine (26) crank shaft (15) by means of flywheel mounting bolts (8). The flywheel (1) consists of an annular cavity (27) for housing the annulus high temperature seals (9) and Movable clamping plate (10). The front end of the flywheel (1) has a Clutch disc (5), along with the friction liners (4) which is sandwiched by the pressure plate (3) and the pressure plate(3) is a projection of the flywheel mounting plate (2). The flywheel mounting plate (2) is mounted onto the flywheel (1) by

means of the circumferential bolts (11). The clutch disc (5) is held in place, axially with respect to flywheel (1) by means of gear box input shaft (7) further supported by means of gear box bearing (not shown since well know to those skilled in the art). The torque transmission to the gear box input shaft (7) is by means of clutch disc hub (6). The flywheel (1) has internal drilled equidistance circumferential fluid path (16) which connects the annulus cavity (27) to the dynamic seal body (14) for transmitting the fluid (not shown). The dynamic seal body (14) consists of fluid seals (13) which come in contact with static seal body (12) for transmitting the fluid to the flywheel (1) due to the rotation transmitted from the crank shaft (15) of the engine block (26). The complete dynamic seal body (14) fluid seal (13) and static seal "body (12) is also called in as fluid coupling (14, 13, 12). The static seal body (12) is mounted on to the engine block (26) and is stationary. The above explained components except the engine (26) are all enclosed inside the clutch housing (22). The static seal body (12) has an opening (not numbered) for fitment of fluid connection which is pneumatically/hydraulically connected to the safety cut off valve (25). The valve plunger (24) is pressed by means of projection (23) in the clutch housing (22). The safety cut off valve (25) is further pneumatically/hydraulically connected to the pressure regulating valve (21) which is further connected in the same way to the pressure source (17). There is a pressure regulating knob (20) on the pressure regulating valve (21) which is used to regulate pressure coming from pressure source (17) down into the fluid circuit. This pressure regulating knob (20) is further fixed to a pedal (18) which forms a driver interface for clutch operation. The clutch pedal (18) also has a spring (19) for pedal feel and pedal return.
The working of the present invention with respect to fig. 2 and fig. 3, when the engine (26) is started, the flywheel (1) starts rotating. Depending on the clutch pedal (18) position and the pressure in the pressure reservoir (17) the clutch disc (5) friction liners (4) will be either in clamped or undamped condition.

During disengagement (shown in fig 3): when the driver wants to disengage the clutch for shifting to 1st gear he presses the clutch pedal (18) due to which the pressure regulating knob (20) gets turned and the pressure reduces across pressure reducing valve (21). This drop in pressure due to the discharge of the fluid in the pressure reducing valve (21) is through out the fluid system sensed across the safety cut off valve (25) and further down into the fluid coupling (12,13,14) and even annulus cavity (27) of the flywheel(l). This is pressure drop all over is due to the fluid connection between these elements. Due to this the clamp load applied on the friction liner (4) surface reduces. When the clutch pedal is fully pressed the pressure in the system is reduced to zero leading to zero clamp load on the friction liner (4) there by disconnecting the flywheel (1) and flywheel mounting plate (2) for any torque/speed transmission. Now, the Gear box input shaft (7) is free to rotate along with the clutch disc (5) without relative motion between the Clutch disc (5) and gear box input shaft (7) because of the positive locking of the clutch disc hub (6) splines with the splines on the Gear box input shaft (7). Now the driver can shift to 1st gear from neutral or to any other gear to any gear.
During engagement (shown in figure 2) or during launch of vehicle: as soon as the clutch pedal is released the clutch pressure across the pressure regulator valve (21) increases and is transmitted in the same way as in case of disengagement. Due to the rise in pressure the movable clamping plate (10) in the flywheel (1) starts clamping the friction liners (4) against the pressure plate (3) leading to gradual increase in torque and revolution, transmitted from the rotating Flywheel (1) and the flywheel mounting plate (2) to the clutch disc (5) further down into the Gear box (not shown) through the gear box input shaft (7). This leads to vehicle movement.
During Clutch disc wear condition (figure 2) -.Even with the friction liner (4) surface getting worn out the movable clamping plate (10) maintains the same amount of clamp load because the clamp load only depends on applied pressure and not on the nature of diaphragm spring curve as in case of exiting clutch assemblies. Higher wear thickness

can be provided on the friction liner (4) due to the higher travel reserve in the movable clamping plate (10) and also due to static annulus high temperature seal (9) thickness. The annulus high temperature seals (9) main function is to seal the fluid inside the annulus cavity (27) of the flywheel (1) covered in the front end by movable plate (10).
The additional safety features provided in the present invention are:
- Due to the design, the bigger annular cavity (27) achievable in the flywheel (1), so low pressure fluid is sufficient for producing higher clamp load on the friction liner (4) surface. This helps in higher torque transmission at lower pressure resulting in longer life of the two important seals namely at the annulus high temperature seal (9) and at the fluid coupling (12, 13, 14).
- During replacement of the clutch disc (5) the pedal (18) is normally in up condition and on removing of the clutch housing (22) and flywheel mounting plate (2). The moving clamping plate (10) will pop out damaging the annulus high temperature seals (9) in absence of safety cut off valve (25). But, as soon as the clutch housing is removed from the engine (26) block the valve plunger (24) preloaded by the spring (not shown) inside the safety cut-off valve (25) comes outside due to the absence of clutch housing stopper (23). This cuts -off any fluid flow further down into the system and it also relives the pressure inside the flywheel (1) annulus cavity (27). Thus the system is safe.
The Working of the present invention when adopted on the automated manual transmission (shown in fig. 4) is described below:
The working of the system remains same as above with respect to figure 1 and figure 2 except that the pressure control is by servo pressure control valve (28) and not by means of pressure regulating valve (21), pressure regulating knob (20) clutch pedal (18). The said servo pressure control valve (28) is a mostly available in automated manual transmission system.

The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

WE CLAIM
1. A clutch system for a vehicle comprising:
- a flywheel (1) provided with an annular cavity (27),
- an internal fluid path (16) provided in said flywheel (1), said internal fluid path being connected to said annular cavity (27) for transmitting the fluid,
- a movable clamping plate (10) and sealing means (9) provided at front end of said flywheel for enclosing said annular cavity (27),
- a flywheel mounting plate (2) secured circumferentially onto said flywheel, said mounting plate (2) being provided with inner projection defining pressure plate of said clamping plate (10),
- the pressure plate (3) is adapted to bear on one face of friction liner (4) of a clutch disc (5), the other face of the friction liner (4) being in contiguous relationship with the clamping plate (10),
- said movable clamping plate (10) is adapted to clamp friction liners (4) against the pressure plate (3) owing to rise in fluid pressure in said annular cavity, which leads to gradual increase in torque and revolution, transmitted from said rotating flywheel (1) and said flywheel mounting plate (2) to the clutch disc (5) further to gear box input shaft (7).

2. The clutch system as claimed in claim 1, wherein said flywheel mounting plate (2) is mounted onto the flywheel (1) by fastening means (II).
3. The clutch system as claimed in claim 1, wherein said clutch disc (5) is held in place, axially with respect to said flywheel (1) by means of gear box input shaft
(7).

4. The clutch system as claimed in claim 1, wherein said flywheel has internal drilled circumferential fluid path (16) which connects the annular cavity (27) to dynamic seal body (14) for transmitting the fluid.
5. The clutch system as claimed in claim 4, wherein said dynamic seal body (14) consists of fluid seals (13) which come in contact with static seal body (12) mounted onto the engine (26) for transmitting the fluid to the flywheel (1) due to the rotation transmitted from the crank shaft (15) of the engine (26).
6. The clutch system as claimed in claim 5, wherein said static seal body (12) has an opening for fluid connection which is pneumatically/hydraulically connected to safety cut off valve (25).
7. The clutch system as claimed in claim 6, wherein said safety cut off valve (25) is designed for cut-off the fluid flow to said fluid seals (13) and to said annular cavity (27) in case of replacing said clutch disc (5)..
8. The clutch system as claimed in claim 1, wherein said movable clamping plate (10) maintains the same amount of clamp load in case of wearing of friction liner (4) as clamp load only depends on the applied fluid pressure.
9. The clutch system as claimed in claim 1, wherein said sealing means is high temperature seals (9), which function is to seal the fluid inside the annular cavity (27) of the flywheel (1).
10. The clutch system as claimed in claim 1, wherein a pressure regulating valve (21) can be replaced by servo pressure control valve (28),

11. The clutch system as claimed in any of the above claim, wherein said flywheel (1) is mounted on engine crank shaft (15) by fastening means (8).