Field of the Invention
The present invention relates to wear adjustment indicator in a clutch and more particularly the present invention relates to the stage when the clutch needs wear adjustment.
Background of the Invention
Clutch is a device that enables transmission of power from the engine of a vehicle to the gearbox. It ordinarily comprises of a pressure plate assembly and clutch disc. The clutch disc is sandwiched between the pressure plate and the flywheel. A release sleeve assembly is actuated with the help of clutch pedal at the driver control. The release sleeve assembly releases the pressure plate through levers located in the Retainer slot. A fork at the end opposite to the driver control assists in pulling the release sleeve assembly. When fully engaged, the whole clutch assembly spins at the same speed as the flywheel and when fully disengaged, the pressure plate releases the clutch disc.
The position of release sleeve assembly (setup height of the assembly) is dependant upon the position of the pressure plate, which moves towards flywheel as the clutch disc wears. As the clutch disc wears, the setup height of a pull type assembly reduces. When it falls beyond a certain limit, the clutch would not release properly. So the clutch has to be adjusted proportionately as the wear takes place.
The set up height of a pull type assembly is adjusted by an adjuster comprising of a pinion meshing with the internal gear of the adjusting ring or by a conventional tool hitting the lugs on the surface of the adjusting ring or automatically in case of self-adjusting type clutches. In the process the adjusting ring slides down the threads on the inside of the housing.
As the clutch disc wears the setup height of the clutch reduces and after a certain amount of drop in setup height it becomes hard to operate the clutch. Also the clutch starts slipping generating the excessive heat causing premature wear of the clutch disc friction material. The present invention is addressed at providing a technical solution to indicate that the wear on the disc has reached to a pre-determined level and the clutch has to be readjusted back to its original position.
Related Art
Devices have been configured in the past to assist automobile mechanics in judging whether the clutch disc has completely worn off. The United States Patent No. 5,238,093 to Campbell discloses an arrangement wherein a wear indicator has been devised. The wear indicator is made of Nylon with a spring-loaded pin inserted in it. This construction is fitted in the housing to judge the amount of wear. The pin is locked in the sleeve and is prevented from moving away by using a shoulder each on the pin and the sleeve and is positioned by rotating it with respect to the sleeve. The present invention differs from the Campbell patent both functionally and structurally. The Campbell patent does not give an indication that the clutch has to be adjusted also no visual or sound indication is given to the driver..
The arrangement disclosed in the United States Patent No. 5,181,593 to Flotow et.al discloses an apparatus for automatically sensing the condition when the friction material of the clutch disc has excessively worn and accordingly generates a signal in response thereto. The sensor is mounted in the bearing housing, a part of the clutch assembly adapted to move between engaged and disengaged position, for generating a signal when fingers of the shift assembly are in contact therewith. This signal is used for generating an alarm. The construction of the device disclosed in the above patent is substantially different from the present invention. The sensor is placed at a different location and it senses the distance between the housing face and the sensor, which varies as the clutch wears. The construction is made simpler as there is no timing and comparison circuit.
U.S. Patent No. 5,730,268 to Villata provides for a hydraulic clutch having an indicating member coupled to an actuating piston for an axial straight-line movement. This member projects outside the clutch casing via aperture to mechanically transmit information relating to the displacement of the actuating piston. As the friction liners become worn, the pressure plate moves towards the reaction plate and release bearing coupled to a diaphragm displaces axially according to the inclination of diaphragm. The position of release bearing thus varies according to the wear of friction liner. The wear in friction liners can be measured from the indicating device that projects outside the casing. The construction shown here is different both structurally and principally.
U. S. Patent No. 4, 550, 815 to Gale discloses a clutch having a base fixed to the clutch housing and a microswitch on a carrier. The length of the aperture is such that the clutch lever engages the microswitch when the clutch linings are worn thereby illuminating the warning light. The construction shown here is different both structurally and principally.
A disc clutch with servo mechanism with a cylinder having a signal bore extending from the cylinder working chamber to atmosphere is described in the U. S. Patent No. 4, 084, 671 to Ternehall. A pin seals this bore during the normal operating state. When the clutch is worn the pin extends into the chamber and the piston comes close to the cylinder bottom and pushes the pin outwards. And subsequently the pin opens an air passage from the chamber to the atmosphere, and an acoustic signal indicates clutch wear.
The arrangement disclosed in the Patent DE4414471 to Murase describes a housing being non-rotatably coupled to the clutch counter pressure disc to which an axially movable pressure disc is linked. The clutch disc is fitted between the counter pressure and pressure disc. The pressure is stressed in the direction to the counter pressure disc by a spring. The clutch disc wear causes gap between the pressure disc and the spring and is being detected by an indicator and an adjuster effectively moving the support region of the pressure disc in the direction towards the counter pressure disc such that the gap between the pressure disc and spring is removed.
Summary of the Invention
In accordance with the principal aspect of the present invention, a wear adjustment indicator in a clutch has been developed to indicate the stage to adjust the clutch and recording the number of wear adjustments in a clutch.
In accordance with another aspect of the invention, the wear adjustment indicator in a clutch is configured to indicate the gap between the release bearing cage and the top of the housing when the gap falls a pre-determined dimension. An inductive proximity sensor is screwed on the release bearingassembly. A mounting plate configured to mount the mount the inductive proximity ssensor and when the clutch is in new condition or it has been adjusted after wear, the gap between the sensing surface and the housing top face is such that there in no signal from the sensor. As the clutch disc wears, the distance between the sensing surface, which
moves axially towards flywheel and the top face of the cover which doesn't move axially, decreases and when the gap falls upto the minimum sensing distance of the sensor, it dampens the electromagnetic oscillations produced by the coil of the sensor which in turn starts generating a signal which is suitably transmitted to some indicating device.
It is also an aspect of the present invention to device a method for indicating the time of wear adjustment in a clutch. The method comprises configuring a wear adjustment indicator having a inductive proximity sensor with a housing end and a release bearing end, configuring a mounting plate to mount the inductive proximity sensor and the mounting plate with the inductive snesor screwed to the release bearing assembly thereby as the clutch disc wears, gauging the change in gap between the sensing surface, which moves axially towards flywheel and the top face of the housing which doesn't move axially, and when the gap falls beyond the minimum sensing distance of the sensor it starts generating a signal which is suitably transmitted to some indicating device.
Other features and advantages of the present invention will become apparent from the following detailed description and accompanying drawing figures.
Brief Description of the Accompanying Drawing Figures
Further objects of the present invention together with additional features contributing thereto and advantages accruing therefrom will be apparent from the following description of preferred embodiments of the present invention which are shown in the accompanying drawing figures with like reference numerals indicating like components throughout, wherein:
Fig. 1 is the front view of the clutch assembly showing the position of wear indicator relative to the housing
Fig. 2 is an enlarged view of a portion of the view of clutch of Fig. 1 in new engaged condition.
Fig. 3 is an enlarged view of a portion of the view of clutch of Fig. 1 in disengaged condition.
Fig. 4 is an enlarged view of a portion of the view of clutch of Fig. 1 in worn out condition.
Fig. 5 A, 5B, 5C & 5D are the block diagrams of various types of wear adjustment indicators.
Fig 6 shows the block diagram of the general operation of inductive type proximity switch
Detailed Description of the Preferred Embodiment
Fig. 1 shows a clutch 100 configured in accordance with the present invention, wherein the driven disc 110 is clamped between the Pressure Plate 120 and flywheel 130 when the clutch 100 is engaged. Driven disc 110 has splines on the hub 140, which slides on output shaft 150, which in turn rotates and is used to drive the wheels of a vehicle. The pressure plate 120 is mounted within a housing 160, which is screwed on the flywheel 130. Means are provided to force the pressure plate towards flywheel when the clutch 100 is engaged.
The pressure plate 120 is connected to the release bearing assembly 170 by set of levers. During clutch disengagement, a fork actuates the release bearing assembly 170 to the right. The pressure plate 120 looses its grip on the clutch disc 110 and the clutch is disengaged.
A wear adjustment indicator is located on the release bearing assembly 170 by means of a mounting plate 190 screwed on the release bearing assembly 170 on one side and wear adjustment indicator on other side. The wear adjustment indicator is a conventional inductive proximity sensor. The battery 200 of the vehicle (Voltage 10-30) is used to give power to the wear adjustment indicator.
Lugs 210 are provided on the release bearing assembly 170 to avoid any damage to the wear adjustment indicator. The release bearing assembly 170 is under spring load and hence when the clutch 100 is in free condition that is not fitted on the flywheel 130, the release bearing assembly 170 would try to move inward as much as possible. If not stopped from moving beyond a level, the clutch components might get displaced from their position and clutch becomes unusable. Also, hitting on the face of the housing 160 might damage the sensing face of the wear adjustment indicator.
The gap 220 between the top face of the housing 160 and the sensing surface of the inductive proximity sensorl80 changes during operation of the clutch 100. As the clutch disc 110 wears, the pressure plate 120 moves towards flywheel 130 and the gap 220 reduces. This gap 220 increases when the clutch 100 is disengaged by moving the release bearing assembly 170 to the right.
Referring now to Fig. 2, the portion of the clutch is shown where unworn clutch disc 110 is in engaged condition. The gap 220 is represented by Dl. This is the initial setting of the clutch and the wear adjustment indicator remains off and no signal is generated. The gap Dl in this position is more than the minimum sensing range required by the inductive proximity switch to turn it on.
Fig. 3 shows the portion of the clutch 100 in disengaged condition. The gap 220 increases and is represented by D2. Again, this gap D2 is more than the minimum sensing range required by the inductive proximity switch to turn it on.
Fig. 4 shows the configuration of the portion of the clutch 100 in worn-out condition. The pressure plate 120 along with the release bearing assembly 170 moves towards flywheel 130, such that the gap 220 represented by D3 reduces. As this gap 220 reduces up to the threshold distance D3 required by the wear adjustment indicator to turn it on, inductive proximity switch generates a signal which can be suitable transferred to any suitable indicating device at the drivers cabin indicating that the wear on the driven disc 110 has reached to a maximum level and the clutch 100 needs to be readjusted. If clutch 100 not adjusted at this time, the clutch 100 would work at a reduced performance due to slippage and hard disengagement. This cause the excessive heat generation causing premature wear of the clutch disc friction material.
Fig 5 A, 5B, 5C and 5D shows the block diagrams of various wear adjustment indicators. The variation of the gap 220 between the top face of the housing 160 and the sensing surface of the inductive proximity sensor 180 can be shown by an indicating device. In one aspect, indicating device can be configured to receive the effective output signal from the inductive proximity sensor 180 of the wear adjustment indicator thereby indicating the gaps Dl, D2 and D3 in a digital counter as represented in Fig 5A.
In Fig 5B, the effective output signal from the inductive proximity sensor 180 is fed to an analogue indicator wherein at the various stages, the gaps Dl, D2 and D3 are represented.
The effective output signal from the inductive proximity sensor 180 is converted to a beep or connected to an LED which glows thereby indicating that the driven disc 110 has worn out and the clutch needs to be adjusted as shown in Fig 5C and 5D.
Fig 6 shows the general operation of inductive type proximity switch During operation an oscillating magnetic field is generated by the coil 2 and this field is projected from sensing face of sensor when the clutch is worn and the conductive material object 1 enters the magnetic field it causes damping of oscillations. This change is detected by inbuilt oscillator 3 and this signal is fed to amplifier 4, this amplified signal is fed to the switching circuit to give an effective output signal
The clutch presented here is a pull type manually adjustable type. Suitable provisions are made to adjust the clutch. One such provision is to use an adjusting ring threadably coupled to the housing levers are placed at one end of the adjusting ring. During adjustment this adjusting ring is made to slide down the threads by some mechanical means either using a pinion and gear arrangement or using a conventional hitting tool hitting the lugs on the surface of the adjusting ring.
The method of adjustment may vary but the same wear adjustment can be used on any configuration of manually adjustable pull type clutch.

We Claim:
1. A wear adjustment indicator in a pull type angle spring clutch 100 having a
driven disc 110, a pressure plate 120, a flywheel 130, a hub 140, an output shaft 150, a
housing 160, a release bearing assembly 170, the wear adjustment indicator comprising:
an inductive proximity sensor 180 having a housing end with a sensing surface and a release bearing end configured to gauge the change in gap 220 between the top surface of the housing and the sensing surface of the sensor; and
a mounting plate 190 configured to mount the inductive proximity sensor 180, the mounting plate screwed onto the release bearing assembly 170, wherein the wear adjustment indicator indicates when to adjust the clutch and records the number of wear adjustments in a clutch.
2. The wear adjustment indicator as claimed in claim 1 wherein the gap 220 between the top surface of the housing and the sensing surface of the sensor changes during the operation of the clutch 100.
3. The wear adjustment indicator as claimed in claim 1 wherein in an engaged unworn condition of the driven disc 110, the gap 220 represented by Dl is more than the minimum sensing range required by the sensor to generate any signal.
4. The wear adjustment indicator as claimed in claim 1 wherein in a disengaged condition, the gap 220 represented by D2 is more than the minimum sensing range required by the sensor to generate any signal.
5. The wear adjustment indicator as claimed in claim 1 wherein when the driven disc 110 wears, the pressure plate 120 alongwith the release bearing assembly 170 moves axially towards the flywheel 130, the gap 220 represented by D3 reduces and when it reaches the minimum sensing range required by the sensor, it generates a signal which is suitably transmitted to any indicating device.
6. A method of configuring a wear adjustment indicator in a pull type angle spring clutch 100, the method comprising: configuring a wear adjustment indicator having an
inductive proximity sensor 180 having a housing end with a sensing surface and a release bearing end;
configuring a mounting plate 190 to mount the inductive proximity sensor
screwing the mounting plate 190 with the inductive proximity sensor 180 onto the release bearing assembly 170 whereby when the driven disc 110 wears off, it axially moves towards the flywheel 130;
gauging the change in gap 220 between the axially moving sensing surface and the top face of the static housing by the inductive proximity sensor 180; and
wherein when the gap between said sensing surface and the top face of the static housing falls within the minimum sensing range of the inductive proximity sensor 180 , the inductive proximity sensor 180 generates a signal and the signal thus generated is suitably transmitted to any indicating device.
7. The wear adjustment indicator according to any of the preceding claims wherein the indicating device includes a digital displayer, an analog displayer, a beep indicator, an LED displayer and any means capable of transforming the signal received from the inductive proximity sensor into a visual or sound-based display.