FIELD OF INVENTION:

This invention relates to a mechanical device for automobiles, particularly clutch actuating mechanism. Clutch Booster (or Clutch servo) is an assembly used in Automobiles in the Clutch actuating mechanism. It is primarily used to reduce manual effort needed to dis-engage the clutch whenever gear shift is required.

The device utilizes the compressed air available in the vehicle system to boost the force required for dis-engaging the clutch.

BACKGROUND OF THE INVENTION:

There are many clutch boosters relating to technical field of external control of clutches and providing a combination of pneumatic cylinder and a hydraulic cylinder, wherein the principle of adopting hydraulic-operated pneumatic clutch boosted type clutch systems are made available in prior art. Some prior arts are studied below :

EP2053261 (A2) The coupling booster (10) has a booster piston (60) which is moved by a pneumatic pressure for reinforcing a coupling force. A control piston is moved by a hydraulic pressure. The pneumatic pressure is controlled by the position of the control piston. The booster piston is impinged by the pneumatic pressure. The control piston is displaced in a direction which is different from the direction in which the booster piston is moved.

US 7,543,525 B2 A clutch booster usable for an automobile having a clutch. In one embodiment, the clutch booster includes a booster member coupled with the clutch for engaging or disengaging the clutch from the engine of the vehicle in response to a force applied to the clutch of the vehicle and means for determining the status of the clutch of the automobile

CN 201875020 U The utility model provides a clutch booster, and relates to the external control technology field of clutches, the clutch booster is provided with an air pressure cylinder and a hydraulic cylinder connected along the same axis, a piston is disposed in the air pressure cylinder, one side of the piston is connected with an actuating rod, the other side of the piston is connected with a piston rod, a spring is disposed between one side of the piston and the air pressure cylinder, the piston rod inserts into the hydraulic cylinder, a control valve is disposed perpendicular to the hydraulic cylinder, the air pressure cylinder and the hydraulic cylinder of the clutch booster are constructed to be an integration; the hydraulic pressure cavity and the air pressure cavity are made from aluminum alloy materials, the external side surface of the air pressure cylinder is provided with a sensor and wear indicator installation hole and an air taking opening. The spring forms a self-adjusted clutch booster at one side of the piston rod. The spring forms a non-self-adjusted clutch booster at one side of the piston rod.

US 5,337,564 A clutch-servo for vehicles which constitutes a working device arranged for fluid connection with a master cylinder to be operated by the vehicle's driver. The servo comprises a working cylinder unit (50) with a piston (5) arranged in a working cylinder (1), which piston is connected to the clutch's engaging mechanism, and a control valve unit (60) for the working cylinder unit (50), with a valve body arranged in the valve housing (44). The master cylinder has a fluid connection with the working cylinder unit (50) and the control valve unit (60), so that the fluid in the master cylinder simultaneously exerts a force on the piston (5) and the valve body , in order to try to release the clutch and to move the valve body in order to connect the working cylinder unit (50) to a servo pressure fluid source when the driver operates the master cylinder.

US 4,967,644A pneumatic boost device includes a booster input including a manually actuatable upstream pusher and a downstream pusher positioned such that the movement of the upstream pusher towards the piston causes the upstream pusher to contact and move the downstream pusher toward the piston. A compressed gas is supplied to the cylinder such that the piston is moved in a direction away from the booster input by a system including a gas flow path having a first check valve, the first check valve being seatable on a seat moving with the downstream pusher. Movement of the downstream pusher thus applies a gas pressure to the piston which moves by an amount corresponding to that of the upstream pusher. The downstream pusher has a piston in the additional cylinder. Another gas flow path has a second check valve, the second check valve being seatable on a seat moving with the upstream pusher by movement of the upstream pusher toward the piston. As a result, further movement of the upstream pusher toward the piston beyond a position where the second check valve seats on the seat moving with the upstream pusher causes the downstream pusher to move toward the piston independently of the upstream pusher. According to the invention the valve unit is constituted by a slide valve. Furthermore, the connection between the working cylinder unit (50) and the valve unit (60) is not dependent on mechanical function.

4,773,222 A pneumatic-hydraulic booster for vehicle includes a master cylinder part; a pneumatic cylinder part combined with the master cylinder part which includes a power piston slid able fitted to a cylindrical casing and an output rod fixed to the power piston, extending to the master cylinder part; a partition wall body fitted to the cylindrical casing; and a relay valve part arranged at the opposite side of the partition wall body from the power piston in the cylindrical casing. The relay valve supplies compressed air into an air pressure chamber formed between the partition wall body and the power piston and discharges the compressed air from the air pressure chamber to the atmosphere. When compressed air is supplied into the air pressure chamber through the relay valve part the power piston and the output rod are moved forwards to generate hydraulic pressure in the master cylinder. The hydraulic pressure is applied to a wheel cylinder for braking. The cylindrical casing is open at the side of the partition wall body opposite to the power piston, and a cover member is fixed to the cylindrical casing by a fixing member bolt. The relay valve part sits between the cover member and the partition wall body.

4,955,198 The present invention relates to an improved clutch booster equipped with a power piston and a control valve unit, and more particularly to a clutch booster where in the control valve is operatively connected to a clutch pedal by mechanical link means and there is employed at least one pivot lever as an essential element of the link means, and wherein the pivot lever is pivotally connected to an output rod in such a manner that a manual force rendered upon the clutch pedal of a vehicle may be relayed in the directions of the output rod, thereby enabling the manual clutch operation even in the non-servo operation state where the clutch booster is left not supplied with any operating fluid pressure, and thereby eliminating the need for such complicated mechanical installation as a master cylinder, fluid pipings, etc. incorporated in the connection between the clutch pedal and the clutch booster.

CN201875021 A vehicle clutch booster comprises a cylinder body, a push rod , a plunger, a piston assembly and a valve body, wherein the valve body is provided with an oil boosting cavity, a compressed air input port and a pressure oil input port; the end face of the cylinder body is fixedly connected with a cover plate; the push rod is connected with the plunger; the compressed air input port is communicated with an air boosting cavity of the cylinder body through a valve and a passage; a backflow cavity of the cylinder body is connected with an external breathing device; the external breathing device comprises a respiratory tube and a ventilation plug assembly; the cylinder body is connected with a respiratory tube joint; one end of the respiratory tube is connected with the respiratory tube joint and the other end of the respiratory tube is connected with the ventilation plug assembly; the ventilation plug assembly is internally provided with a filter screen; and the fixed connection position of the cover plate and the end face of the cylinder body is provided with a sealing ring. As the vehicle clutch booster adopts an external breathing structure, the impurities, dust and rainwater generated in severe working conditions are not easy to enter the cylinder. The vehicle clutch booster has the advantages of simple and reasonable structure, good sealing performance, and long service life and meanwhile, is stable and reliable in use performance, and particularly applicable to medium and heavy duty cars and engineering vehicles.

KR2009007896 The present invention relates to a clutch controller for a vehicle; in particular, because this can easily be installed in a hydraulic pressure line connected with a conventional booster cylinder in a short time without changing the vehicle structure, and the clutch petal does not operate automatically if its clutch pedal is manipulated due to operator mistake, it can effectively prevent accidents.

CN201705838 A clutch booster relates to the technical field of external control of clutches and provides a pneumatic cylinder and a hydraulic cylinder which are connected along the same axis. A piston is disposed in the pneumatic cylinder, one side of the piston is connected with an actuating rod while the other side of the piston is connected with a piston rod, a spring is disposed between one side of the piston and the pneumatic cylinder, the piston rod is inserted in the hydraulic cylinder, a control valve is perpendicular to the axis of the hydraulic cylinder, one end of a control valve isolating blow hole is communicated between two sealing rings of the control valve while the other end is communicated with the atmosphere via an exhaust opening, and one end of a hydraulic cavity and pneumatic cavity insolating blow hole is communicated between two sealing rings of the piston rod of the hydraulic cylinder while the other end is communicated to the atmosphere. Outer sides of the two sealing rings of the piston rod of the hydraulic cylinder are respectively provided with a protective pad. The clutch booster is used for heavy and light trucks, large and medium sized coaches and engineering machines adopting hydraulic-operated pneumatic-boosted type clutch systems.

CN101532542 The invention discloses a debugging-free multifunctional clutch booster, which increases a set of electrical control mechanism in parallel on the basis of a hydraulic control mechanism for realizing the diversity of the gear shifting process of the vehicle. The booster further comprises a boosting piston (2), a hydraulic piston and a spacing post (16); wherein the boosting piston (2) and the hydraulic piston form a split structure; the boosting piston (2) is fixedly connected with the spacing post (16); the spacing post (16) is arranged in an inner cavity of the hydraulic piston. When the electrical control mechanism is used for controlling, the boosting piston (2) drives the spacing post (16) to move in a certain limit (L1) of the hydraulic piston without moving the hydraulic piston (a), so as to protect a clutch hydraulic system to the greatest extent.; The booster can effectively judge the separation and reunion states of the clutch through an angular displacement sensor. The booster further comprises a clutch friction plate abrasion alarm device (32).

DESCRIPTION OF INVENTION
The general arrangement is illustrated in Fig.1. The components of essence are marked in Fig. 2-11. Part numbers are detailed below :

Fig 1 illustrates general arrangement of clutch booster

Fig 2 illustrate air cylinder (booster unit)

Fig 3, 3A illustrate cross sectional views of clutch booster

Fig 4 illustrate hydraulic actuation

Fig 5 illustrate balancing of air actuation

Fig 6, 6A illustrate the return stroke more specifically the part nos. 18 and 19.

Fig 7 illustrate single seal with double side sealing arrangement for relay piston

Fig 8 illustrate conventional seal arrangement

Fig 9 illustrate hydraulic and air pressure balancing

Fig 10 illustrate air cylinder to control valve body fastening arrangement

Fig 11 illustrate clamping set up of air cylinder

GENERAL ARRANGEMENT
It is a simple design. It is suitable generally for higher stroke requirements (85mm). It can be made available in two variants i.e. 76mm (3") and 102 mm (4") dia Pneumatic cylinders except for the pneumatic cylinder and piston, all other hydraulic actuation system remains same between the two variants. With this arrangement there is reduced pedal effort and noise level. Further no operating adjustment is needed. Smooth and gradual output force delivery is made available.

The construction details of the parts / components are detailed herein.

The Clutch booster assembly consists of three groups:
a. Hydraulic cylinder
b. Relay piston sub assembly (air control unit)
c. Air cylinder (Booster unit)

Hydraulic Cylinder:
It is the main part of clutch booster assembly which connects to the master cylinder and receives pressurized brake fluid from it. Hydraulic cylinder is acting as slave cylinder and actuate clutch even without air assistance.

Relay Piston Sub Assembly (Air Control Unit)
Poppet valve, where the entry of pressurized air takes place is actuated by means of relay piston sub assembly. The relay piston sub assembly controls the gradual opening and closing of pneumatic supply for the air cylinder assembly and there by acting as a control unit for the booster. Refer. Fig.2

Air Cylinder (Booster Unit)
Air cylinder constitutes air piston and push rod. The compressed air from the air control unit acts on the air piston area and generate boosting power for the clutch actuation. Refer Fig 2.

The invention in one aspect discloses a pneumatic assisted hydraulic booster clutch for vehicle comprising a hydraulic cylinder means for generating a hydraulic pressure said hydraulic means having within a hydraulic piston (a) slidably fitted in a cylindrical casing and a push rod (b) for actuating of clutch against a bias clutch spring of a clutch assembly. It has a pneumatic booster support cylinder means for generating pneumatic pressure said cylinder means disposed on the same axis as of hydraulic cylinder means, having within an air piston and the said hydraulic piston (a) of hydraulic cylinder extending into said pneumatic cylinder and fixed to the air piston, and also an air control relay valve means being arranged for supplying compressed air into pneumatic booster means and discharging air from booster means to atmosphere wherein when compressed oil is supplied into said hydraulic pressure chamber during a clutch operation the push rod (b) is pushed by the hydraulic piston (a) which motion is resisted by bias clutch spring of clutch assembly, thereby generating a brake fluid pressure in the hydraulic means, said generated hydraulic pressure is applied to operate the air control relay valve to a state of supplying compressed air into pneumatic cylinder means, which compressed air acts on the air piston thereby generating a boosting force which additional force is applied on the push rod (b).

Operation:
The operation of clutch booster assembly comprises three stages refer Fig 3
a. Hydraulic actuation
b. Balancing of air actuation
c. Return stroke

When the clutch pedal is pressed by the driver, The hydraulic oil in the master cylinder get pressurized and transferred to the hydraulic cylinder of the clutch booster assembly through oil inlet.

a. Hydraulic piston
b. Push rod (yoke)
c. Poppet valve
d. Air cylinder
e. Air breather tube
f. Relay piston
g. Air breather
h. Conical spring (Relay) i. Conical spring j. Air piston

Hydraulic actuation:
The oil in the hydraulic cylinder is pressurised by the master cylinder and the hydraulic piston (a) tries to move the push rod (b) for the actuation of clutch - Ref Fig 4. When the push rod (b) gets resistance from the clutch spring (not shown in the fig), the brake fluid pressure increases and lifts the relay piston (f) upwards. Refer Fig 5.

Relay piston sub assembly moves up due to hydraulic pressure increase and touches the poppet valve (c). and lifts it up. The opening of poppet valve admits the pneumatic pressure into the air cylinder (d). The pressurized air acts on the air piston (j) and generates the boosting force to actuate clutch assembly. Since the opening of poppet valve (c) is solely dependent on increase in hydraulic pressure, the clutch actuation is gradual. Refer Fig 5.

Return stroke:
When the clutch pedal is released gradually by the driver, the pressure in the hydraulic system drops. As the hydraulic pressure drops, the conical spring moves the relay piston sub assembly back to its original position.

During the return stroke, the poppet valve (c) and relay piston (f) get separated and air get escaped through relay piston hole and breather (g) also it enters into air cylinder from top side through air breather tube (e). Thus the clutch is engaged gradually. Refer Fig 6.

The novelty of the invention lies in the sealing arrangement for the relay piston. A single seal with double side sealing arrangement for relay piston is disclosed herein and illustrated in Fig. 7, wherein side A is Hydraulic pressure side and side B is Pneumatic pressure side and side C is the relay piston seal. This can be compared with the conventional seal arrangement as known in prior art and illustrated in Fig. 8.

In the invention the relay piston seal is designed in such a way that it reduces one more lip seal or O ring used conventionally in other clutch boosters. The main hydraulic pressure sealing is done by the lip type seal arrangement effectively while the low pressure exhaust air pressure is sealed by the O ring arrangement on the rear side of the same seal. This new seal design reduces number of parts and also the mass of the moving relay piston assembly. Conventional seal arrangement with two seal arrangement is illustrated in Fig. 8 (marked I)

A clutch booster typically and ideally demands a precise and novel hydraulic and air pressure balancing to achieve the object of invention.

Clutch booster output force is responsive to the pedal force. This responsiveness is achieved by the balancing act of the relay piston. When the clutch pedal is pressed, the hydraulic pressure increases and the relay piston is pushed vertically. The relay piston opens the poppet valve and thus air pressure is let inside the system to give output force. Now the relay piston is subjected to hydraulic pressure one side and air pressure on the other side and hence would reach an equilibrium position. At this equilibrium position, the further air pressure entry is cut-off and hence output force will remain constant. This is called hydraulic and air pressure balancing. Any further pedal pressing will increase the hydraulic pressure and hence disturb the relay piston equilibrium and it opens the poppet valve again to allow more air pressure to enter and correspondingly increases output force of the clutch booster. The direction of hydraulic pressure is marked as D and direction of pneumatic pressure is marked as E.

In one of the embodiment the surface area of the relay piston where hydraulic pressure acts: 2.02 Sq. CM and the surface area of the relay piston where air pressure acts: 4.08 Sq. CM. The ratio of hydraulic pressure to air pressure: 0.495 or 0.5.

This lower ratio allows fine balancing of relay piston to take place for every change in the hydraulic pressure or in other words, clutch pedal force. Hence the clutch booster output force is proportional or responsive to the pedal force.

The invention also discloses the Air cylinder to control valve body fastening arrangement. The hydraulic pressure in the control valve body goes upto 25 bar during clutch operation. This pressure produces 210 kgf and coupled with that air pressure acts from the cylinder side. These forces against the load will result in reaction force acting at the joint between air cylinder and control valve body and tries to separate them apart resulting in air leakage. The fastener screws used to clamp the air cylinder and control valve body should be capable of withstanding this reaction forces. Refer Fig. 10, F is the air cylinder, G is the control valve body and H is the potential air leak path.

In one of the embodiments, the clutch booster design, six M6 screws are used to clamp the air cylinder and control valve body. Additionally, the six M6 screws are positioned at the maximum pitch circle diameter possible with the configuration to provide adequate clamping load. This design will provide improved clamping without air leak complaint in operation. The clamping screws (6nos.) are marked as J in Fig. 11.

The objects of the invention have been achieved by providing in the above described pressure boosting device.

The advantage of the arrangement and the single seal with double side sealing arrangement for Relay piston has been disclosed sufficiently for a skilled person to understand the invention.

Many variation and modifications of the present invention are possible in light of the above teachings. Therefore the invention may be practical otherwise than as specifically described herein and all these fall within the scope of the claims of the invention.

WE CLAIM:

1. A pneumatic assisted hydraulic booster clutch for vehicle comprising :-

a. a hydraulic cylinder means for generating a hydraulic pressure said hydraulic means having within a hydraulic piston (a) slidably fitted in a cylindrical casing and a push rod (b) for actuating of clutch against a bias clutch spring of a clutch assembly,

b. a pneumatic booster support cylinder means for generating pneumatic pressure said cylinder means disposed on the same axis as of hydraulic cylinder means, having within an air piston and the said hydraulic piston (a) of hydraulic cylinder extending into said pneumatic cylinder and fixed to the air piston, and

c. an air control relay valve means being arranged for supplying compressed air into pneumatic booster means and discharging air from booster means to atmosphere wherein when compressed oil is supplied into said hydraulic pressure chamber during a clutch operation the push rod (b) is pushed by the hydraulic piston (a) which motion is resisted by bias clutch spring of clutch assembly, thereby generating a brake fluid pressure in the hydraulic means, said generated hydraulic pressure is applied to operate the air control relay vafve to a state of supplying compressed air into pneumatic cylinder means, which compressed air acts on the air piston thereby generating a boosting force which additional force is applied on the push rod (b).

2. The booster clutch as claimed in claim 1 wherein the valve means includes a relay piston subassembly and a poppet valve, wherein the motion of relay piston towards the poppet valve, opens the poppet valve to admit pneumatic pressure i.e. pressurized air into the pneumatic cylinder means.

3. The booster clutch as claimed in claim 2 wherein the relay piston subassembly is reset with a biased conical spring.

4. The booster clutch as claimed in claim2 wherein the valve means further includes relay piston hole and breather (g) for escape of air to atmosphere

5. The booster clutch as claimed in claim 2 wherein the valve means includes breather tube (e) for entry of air into pneumatic booster cylinder means.

6. The booster clutch as claimed in claim 1 wherein the opening of poppet valve (c) is solely dependant on the increase in the hydraulic pressure in the hydraulic cylinder means.

7. The booster clutch as claimed in claim 1 wherein the air control valve communicates with hydraulic means and pressure means with a single seal, the said seal characterized having a lip type seal arrangement at hydraulic means end and an O ring seal type arrangement at pneumatic means end

8. The booster clutch as claimed in claim 1 wherein the control valve is subjected to hydraulic pressure at one end and pneumatic pressure at other end.

9. The booster clutch as claimed in claim 1 wherein the surface area of control valve subjected to hydraulic pressure is 2.02 sq.cm.

10. The booster clutch as claimed in claim 1 wherein the surface area of control valve subjected to pneumatic pressure is 4.08 sq.cm.

11. The booster clutch as claimed in claim 1 wherein the ratio of hydraulic pressure to pneumatic pressure generated is 0.495 to 0.50 :1.