FR2674303A1 - Method and device for measuring and diagnosing wear of clutch linings - Google Patents

Abstract

Method for measuring and diagnosing wear of the linings of a clutch of the type including a plate (6) pressing, in the clutch-engaged position, a disc (3) equipped with linings (3') against an engine flywheel (2) under the action of a diaphragm (4), the said diaphragm (4) releasing the disc (3) under the action of a thrust bearing (22), itself controlled by a clutch release fork (11), the method relying on indirect measurement of the wear of the linings (3') using elements of the clutch which are not subject to rotation, and characterised in that the information picked up is transmitted to the driver via a signal on his instrument panel (dashboard).

Description

MEASUREMENT AND DIAGNOSIS METHOD AND DEVICES
CLUTCH LINING WEAR
The invention relates to friction disc clutches. Clutches of this type generally include a massive pressure plate participating in particular in the thermal capacity function, a drive disc on which a friction lining is glued or riveted, and a second friction surface constituted by the flywheel .

In such clutches, an elastic washer called a diaphragm presses the plate, the flywheel and the disc against each other in the engaged position. Torque transmission is thus ensured by the clutch, between the engine and the gearbox. When the clutch is disengaged, for example during a gear change, the force applied to the plate by the diaphragm is taken up by a clutch release bearing with mechanical or hydraulic control.

More specifically, the invention relates to the problem of wear of the linings and to the possibilities of measurement and diagnosis thereof. The assembly. Constituted by the steering wheel, the linings and the disc, being subjected to rotation, it is difficult to install, without excessive cost, elements directly controlling the operation of these organs, such as rotary manifolds. However, during the life cycle of a clutch, under the effect of wear, a certain number of organs and mechanical phenomena, such as the position of the diaphragm nozzles and of the elements which are linked to them (stop, fork and cable), the forces to be exerted on the stop to disengage ("force at the stop"), and the position of the stop at the end of coupling, change.

The difficulty of installing detection members on elements subjected to rotation has led manufacturers to design systems making it possible to assess the wear of the clutch linings on non-rotating members. This is the case of the clutch lining measurement device described in publication FR-2,517,401. This device relates to a clutch with hydraulic control and takes into account the evolution of the position occupied by the piston receiving the control under the effect of the retraction of the diaphragm nozzles. With such a device, it is necessary to initialize the system by defining a limit position of the piston at the end of the stroke before the risk of slipping occurs; these risks are detected when the displacement dimension of the piston, measured relative to its initial position, corresponds to the wear stroke. The application of the device which is the subject of this publication, limited in fact to a hydraulic control of clutch, presupposes direct observation of the control inside the engine compartment.

The invention goes beyond the limits of use imposed by the devices known to date by proposing a method for measuring and diagnosing wear of clutch linings, offering numerous possibilities of implementation. It also offers a certain number of devices specially designed for the implementation of this process.

The invention relates to a method for measuring and diagnosing the wear of the linings of a clutch of the type comprising a plate pressing in the engaged position a disc provided with linings against a flywheel under the action of a diaphragm, said diaphragm. releasing the disc under the action of a stop, itself controlled by a clutch release fork. This process is based on the indirect measurement of the wear of the linings from elements of the clutch not subjected to rotation. It is characterized in that the information collected is transmitted to the driver by means of a signal on the dashboard.

According to one embodiment of the invention, the method takes into account the displacement of the diaphragm nozzles under the effect of the wear of the linings.

According to one embodiment of the invention, the method is characterized in that it takes into account the forces to be exerted on the stopper to disengage.

According to one embodiment of the invention, the method is characterized in that it takes into account the position of the clutch stop at the end of coupling of the linings.

The invention also relates to a cable clutch control device with initial adjustment specially designed for implementing the method of the invention, this device comprising a control cable housed inside a crimped and adjustable end piece. by means of a threaded adjustment nut, pressing against the fork during disengagement, and a self-locking ring initially placed at a certain distance from the nut; this device is characterized in that the diagnosis is established on the basis of the progressive disappearance of the initial clearance separating the ring from the nut in the engaged position.

The invention also relates to a cable clutch control device without adjustment specially designed for implementing the method of the invention, consisting of a fixed housing relative to the clutch housing traversed right through the control cable and housing an elastic stop, as well as a ring integral with the cable and movable in this housing, the stop being coupled to an electrical contactor. This device is characterized in that the wear wear diagnosis is established when the ring comes into contact with the contactor, following the reduction in the clearance initially provided between these two elements in the engaged position.

The invention also relates to a cable clutch control device specially designed for implementing the method of the invention, comprising a first stop fitted with a contactor, integral with the casing, adjustable in position and mounted on a spring, and a second stop integral with the fork. This device is characterized in that the wear diagnosis is established when the two stops come into contact in the engaged position.

The invention also relates to a cable clutch control device housed in a sheath and adjustable in position, specially designed for implementing the method according to the invention. This device comprises a housing integral with the cable and freely traversed by the sheath, and a ring whose initial position is determined by its immobilization on the sheath at a certain defined distance from the housing when adopting new fittings on the clutch. This device is characterized. in that the measurement of the dimension of the displacement of the ring relative to the housing linked to the wear of the linings, makes it possible to evaluate the degree of wear of the latter.

The invention also relates to a cable or hydraulic clutch control device specially designed for implementing the method of the invention, comprising a force sensor bearing on the sheath stop element.

This device is characterized in that the exceeding of a preset effort threshold received by the sensor, triggers a signal on the dashboard.

The invention also relates to a cable or hydraulic clutch control device specially designed for implementing the method of the invention comprising a force sensor fixed on the cable; this device is characterized in that the exceeding of a pre-established effort threshold received by the sensor, triggers a signal on the dashboard.

The invention also relates to a hydraulic clutch control device specially designed for implementing the method of the invention. This device comprises a force sensor secured to a push rod associated with the fork. It is characterized in that the exceeding of a preset effort threshold received by the sensor, triggers a signal on the dashboard.

 The invention also relates to a hydraulic clutch control device specially designed for implementing the method of the invention. This device includes a pressure sensor installed in the hydraulic circuit. It is characterized in that the detection of the exceeding of a preset pressure threshold, inside the circuit, triggers a signal on the dashboard.

According to one embodiment of the invention, the method is characterized in that it implements a displacement sensor and in that it is based on the memorization of the position of the declutching fork at the end of the slipping phase .

The invention will be better understood on reading the following description of an embodiment of the invention, in conjunction with the appended drawings in which: - Figures 1 to 6 schematically represent
devices specially designed for implementing the
method of the invention.

- Figure 7 graphically illustrates the evolution of
displacement of a clutch control according to the
time.

The clutch I shown in Figure 1 is in the engaged position. li conventionally comprises a flywheel 2 on which is exerted, in this position, the pressure of the plate 6, via the disc 3 provided with linings 3 '. When disengaging, the traction exerted on the pedal (not shown) by the driver rotates the fork 11 so that the stop 22 moves along the guide tube 5 by pressing on the nozzles 4 'of the diaphragm 4 and making pivot the latter around its articulation point 4 "; the pivoting of the diaphragm 4 has the effect of separating the plate 6 from the flywheel 2.

The measurement and diagnostic device highlighted in this figure applies to an adjustable cable clutch control. This device takes advantage of the adjusting screw 7 of the cable 8, and of the adjusting nut 9 'pressing against the fork 11 during disengagement. The cable 8 is housed inside a crimped end 9 and is adjusted by means of the threaded nut 9 '. The device also takes advantage of a self-braking ring 10 engaged on the screw 7. When mounting new linings 3 ', the self-braking ring 10 is placed at a distance x from the adjusting nut 9'. The wear of the linings 3 'causes a progressive displacement of the lower end of the fork 11 in the engaged position, resulting in each adjustment by a reduction in the clearance x. The disappearance of the clearance x indicates the total wear of the lining d 'clutch. It is possible to appropriately place a switch 12, for example on the self-braking ring 10, making it possible to warn the driver on his dashboard of the disappearance of play.

The measurement and diagnostic device shown in FIG. 2 applies to a cable clutch control without adjustment. This device consists of a housing 13 secured to a sheath stop 14. Inside this housing 13 is housed a ring 15 secured to the cable 8, and a stop 16 mounted on a spring 17 bearing against one end of the housing 13. As in the previous example, when assembling new linings, the ring 15 and the stop 16 are arranged at a distance x from one another, for example by means of an appropriate gauge (not The residual distance x between the ring 15 and the stop can be measured from the outside, but the stop 16 will advantageously be coupled to a contactor 12 making it possible to directly warn the driver of the disappearance of the clearance x, this is that is, the need to change the linings 3 '. The spring 17 also allows the driver to benefit from an additional wear stroke, after contact with the ring 15 and the stop 16.

FIG. 3 relates to another measurement and diagnostic device applicable to cable controls. This device comprises a first stop 18 secured to the clutch release fork 11 and a second stop 19 provided with a contactor 12. As in the previous examples, a gauge makes it possible, when mounting new linings 3 ′, to position the adjustable stop 19 at a determined distance x, from the movable stop 18, in the engaged position. The wear of the linings 3 'leads to the gradual approximation of the two stops 18, 19 in this position. Here again, one of the stops, for example the adjustable stop 19, can be coupled to a contactor 12 serving as an alarm. The spring 17 fulfills the same function as in the previous example.

FIG. 4 shows a device for measuring and diagnosing wear applicable to a clutch control by cable with sheath adjustment. This device comprises a housing 20 and a ring 21, the initial position of which can be fixed by immobilizing it on the sheath 9 at a defined distance x from the housing 20 in the engaged position, with new fittings. The cable 8 runs inside the housing 20 during the operation of the clutch and the clutch. The distance x separating the ring 21 from the housing 20 varies with the degree of wear of the linings 3 '. This game can be evaluated from the outside, or. his disappearance sanctioned by the excitement of a contactor 12.

The device of FIG. 5 also makes it possible to detect whether the clutch is close to slippage due to the wear of the linings 3 '. This device is applicable to a cable or hydraulic control. Its implementation is based on taking into account the relationship between the increase in "force at the stop" felt by the driver, and the different positioning of the diaphragm 4 linked to the wear of the linings 3 '. This device uses a force sensor bearing on the sheath stop 24, the fork 11, or even secured to the cable 8. These three potential locations of the sensor (23) are shown respectively in FIG. 5 in solid lines, in long dashed lines, and in dashed lines. Here again, when the force captured exceeds a predetermined threshold, corresponding information is transmitted inside the vehicle, for example on the dashboard, so as to preven. i driver that his clutch is worn.

The measurement and diagnostic device of FIG. 6 applies to a hydraulic clutch control 26. Like that of FIG. 5, its implementation is based on taking into account the relationship existing between the increase in the force at the stop and that of the travel of the diaphragm 4, due to the wear of the linings 3 '. This device comprises either a force sensor 23 secured to the push rod 25, or a pressure sensor 27 installed in the hydraulic control circuit 26. The exceeding of a preset pressure threshold is felt by the sensor 23 or 27 , which triggers a signal on the dashboard, as in the previous examples.

It appears from the description which has just been made,. that all the devices mentioned are devices for indirectly measuring the wear of the linings, reflecting this development from the behavior of elements of the clutch not subjected to rotation. Each of these devices makes it possible, thanks to the judicious adaptation of a sensor or a contactor, to inform the driver of the wear of the linings.

 More specifically, the devices corresponding to Figures 1,2,3,4 take into account the displacement of the diaphragm nozzles under the effect of wear, resulting in a displacement of the end of the fork in the engaged position. On the other hand, the devices of FIGS. 4 and 5, applicable respectively in the case of a cable control and that of a hydraulic control, take into account the increase in the force at the stop when the parts are worn.

Without departing from the scope of the invention, it is possible to produce other devices based for example on taking into account the loss of capacity of the diaphragm to provide torque during its wear. The latter solution, applicable both in the case of a mechanical control than that of a hydraulic control, can in particular be based on memorizing the movement of the fork during the start-up phase. Indeed, with the wear of the linings, the effort of the plate at rest (engaged position) decreases: the reserve in torque transmission capacity of the clutch decreases, and a reduced effort, exerted on the pedal, is enough to make slip the clutch. This phenomenon is illustrated by the graph in FIG. 7, representing the evolution of the displacement of the clutch control as a function of time, over which:
A corresponds to the skating phase,
B corresponds to the engaged position, 1 corresponds to the coupling position with seals
new, 2 corresponds to the coupling position with seals
worn.

A method of measuring and diagnosing the wear of the clutch linings based on the evolution of the torque capacity of the diaphragm may for example consist in detecting the evolution of the slip position of the clutch release fork at the end of skating phase, thanks to the adaptation on it of a displacement sensor making it possible to memorize this position.

Claims (7)

CLAIMS [1] Method for measuring and diagnosing the wear of the linings of a clutch of the type comprising a plate (6) pressing in disconnected position a disc (3) provided with linings (3 ') against a flywheel (2) under the action of a diaphragm (4), said diaphragm (4) releasing the disc (3) under the action of a stop (22) itself controlled by a clutch release fork (11), process based on the indirect measurement of the wear of the linings (3 ') from elements of the clutch not subjected to rotation, and characterized in that the information collected is transmitted to the driver by means of a signal on his dashboard. 2 Measuring and diagnostic method according to the  claim 1 characterized in that it takes into account  the displacement of the nozzles (4 ') of the diaphragm (4) under  the effect of wear on the linings (3 '). 31 Measuring and diagnostic method according to the  claim 1 characterized in that it takes into account  the forces to be exerted on the stop (22) to disengage. [4] Measuring and diagnostic method according to the  claim 1 characterized in that it takes into account  the position of the clutch bearing (22) at the end of  coupling of fittings (3 '). 5 Cable clutch control device with  initial setting, specially designed for setting  implementation of the process according to claim 2,  comprising a control cable (8) housed inside  a crimped end (9) and adjustable by means of a nut  adjustment (9 ') pressing against the fork (11) when  of the clutch, and a self-braking ring (10), placed at  a distance x from the nut (9 '), characterized in that  the diagnosis is established on the basis of the disappearance  progressive of the initial clearance x separating the ring (10) from  the nut (9 ') in the engaged position. 6 Cable clutch control device without  adjustment specially designed for implementing the  process according to claim 2, consisting of  fixed housing (13) relative to the housing (14) of  the clutch, traversed right through by the cable (8)  and accommodating an elastic stop (16) as well  a ring (15) integral with the cable (8) and movable in  the housing (13), the stop (16) being coupled to a  electrical contactor (12), characterized in that the  wear wear diagnosis (3 ') is established during  the coming into contact of the ring (15) with the  contactor (12), following the reduction in clearance x  initially planned between the two elements (15, 16) in  engaged position. [7] Cable clutch control device  specially designed for carrying out the process  according to claim 2, comprising a first  stop (19) provided with a contactor (12) integral with the  casing (14) adjustable in position and spring-mounted  (17), and a second stop (18) integral with the  fork (11), characterized in that the diagnosis  wear is established when the stops (18, 19) come  in contact in the engaged position. 8 Cable clutch control device (8) housed  in a sheath (9) and adjustable in position,  specially designed for carrying out the process  according to claim 2, comprising a housing  (20) integral with the cable (8) and freely traversed by  the sheath (9), as well as a ring (21) whose position  initial is determined by its immobilization on the  sheath (9) at a certain distance defined relative to  to the housing (20) when adopting fittings (3 ')  new on the clutch, characterized in that the measurement  of the displacement side of the ring (21) relative  the housing (20) linked to the wear of the linings (3 '),  allows to assess the degree of wear of these.  [9] Cable clutch control device or  hydraulics specially designed for implementation  of the process according to claim 3, comprising a  force sensor (23) pressing on the stop element  the sheath (24), characterized in that the protrusion  a preset effort threshold, collected by the sensor,  (23) triggers a signal on the dashboard. 10 Cable clutch control device or  hydraulics specially designed for implementation  of the process according to claim 3, comprising a  force sensor (23) integral with the fork (11),  characterized in that exceeding a threshold  pre-established effort, collected by the sensor (23),  triggers a signal on the dashboard. 11 Cable clutch control device or  hydraulics specially designed for implementation  of the process according to claim 3, comprising a  force sensor (23) fixed on the cable (8),  characterized in that exceeding a threshold  of preset effort, collected by the sensor 23,  triggers a signal on the dashboard.  [12] Hydraulic clutch control device  specially designed for carrying out the process  according to claim 3, comprising a  pressure (27) installed in the hydraulic circuit  (26), characterized in that the detection of the overshoot  a preset pressure threshold, inside the  circuit (26), triggers a signal on the control panel  edge. [13] Measuring and diagnostic method according to the  claim 1, characterized in that it implements  a displacement sensor, and in that it rests on the  memorization of the position of the range of  declutching at the end of the skating phase.