GB2372330A

GB2372330A - An arrangement and method for monitoring the state of wear of a motor vehicle friction clutch

Info

Publication number: GB2372330A
Application number: GB0209121A
Authority: GB
Inventors: Hans-Jurgen Drexl
Original assignee: ZF Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1998-03-09
Filing date: 1999-03-08
Publication date: 2002-08-21
Anticipated expiration: 2019-03-08
Also published as: GB2372330B; GB0209121D0

Abstract

An arrangement for monitoring the wear of a friction clutch in the driving line of a motor vehicle comprises a wear detection unit 1c and a memory 13c. The wear detection unit supplies clutch load information as a measurement of the load on the clutch at starting-off operation, and this load value is stored in the memory in association with one or more supplemental vehicle condition values. This further information is derived from a gear position detector 29, a vehicle weight sensor 33, an inclination sensor 35 and an accelerometer 37. The clutch load may be calculated using clutch torque information. A method is also disclosed. The values stored in the memory 13c may be used to establish the reasons for the occurrence of clutch wear.

Description

AN ARRANGEMENT FOR AND A METHOD OF MONITORING THE STATE OF WEAR OF A MOTOR VEHICLE FRICTION CLUTCH The invention relates to an arrangement for, and a method of, monitoring the state of wear of a friction clutch in the driving line of a motor vehicle driven by an internal combustion engine.

DE-OS 36 01 708 discloses an arrangement for monitoring the state of wear of a friction clutch, in which a wear-detection circuit determines the friction load dissipated in the friction clutch by ascertaining the instantaneous clutch slippage. The slippage is itself determined from the difference between the instantaneous output speed of the clutch detected by a second tachometer. This speed difference is multiplied by the value of the torque instantaneously present at the clutch. The torque value is determined from the clutch position ascertained by a clutch position sensor or with the assistance of engine data from the quantity of fuel instantaneously supplied to the internal combustion engine. The monitoring arrangement integrates the friction load values occurring during a clutching process, adds the friction load value integrals associated with successive clutching operations, taking into account the clutch-actuating rate and compares the resulting total value with a limit value. If the total value exceeds the limit value, then the arrangement indicates this by the actuation of an indicator.

The load information supplied by the indicator of the known arrangement is quite suitable for indicating an instantaneous overload of the friction clutch, however it characterises the state of wear of the friction clutch in a manner which is too undifferentiated in order to be able to give the driver of the vehicle an indication as to how, during normal driving, when no overload of the friction clutch occurs, by possibly changing the method of operation of the clutch, i. e. by changing his manner of driving the vehicle, he could reduce the wear on the friction clutch.

It is thus an object of the invention to provide a monitoring arrangement having a simple construction and a monitoring method which supplies load information better characterising the wear of the friction clutch.

According to the invention there is provided an arrangement for monitoring the state of wear of a friction clutch in the driving line of a motor vehicle driven by an internal combustion engine, comprising a wear-detection unit supplying load information as a measurement of the load on the friction clutch at the time of a starting-off operation and a memory for memorising a plurality of values indicating the wear on the friction clutch, which values are determined from load information associated with starting-off operations, wherein the memory memorises values indicating wear in association with at least one information regarding condition from a quantity of information, which comprises: gear position information from a gear-monitoring device representing the gear position of a gear-change mechanism of the motor vehicle engaged at the time of the starting-off operation and/or weight information from a weight sensor representing the instantaneous weight of the motor vehicle and/or inclination information from an inclination sensor representing the inclination of the motor vehicle with respect to the horizontal in the direction of travel at the time of the starting-off operation and/or acceleration information from an acceleration-monitoring circuit representing the acceleration of the motor vehicle at the time of the starting-off operation.

The invention is based on the assumption that at the time of typical operation of a motor vehicle, a major part of the wear occurring on the clutch results from starting-off operations.

The load on the friction clutch at the time of a starting-off operation is all the greater the higher the input speed of the friction clutch at the time of the starting-off operation.

An indicator is preferably provided, which indicates the value of the load information supplied by the wear-detection unit, so that a driver of the vehicle may recognise in particular the wear of the friction clutch characterised by the value of the load information in the past starting-off operation and can optimise his manner of driving with regard to reduced, future wear of the clutch. An analysis of the values memorised in the memory enables conclusions to be drawn as regards the driver's manner of driving and the information obtained therefrom can be used with regard to an optimisation of his manner of driving.

Memorising information about the condition in association with the values indicating the wear, improves the characterisation of the state of wear of the friction clutch and thus the information which can be obtained from a later analysis of the starting-off operations.

If, for example, the gear position of the gear-change mechanism set at the time of individual starting-off operations is memorised in association with the values indicating wear, determined from load information associated with past starting up operations, then it is possible in an analysis of the values memorised, to ascertain at a later date that for example increased wear of the friction clutch is the result of a frequently incorrect choice of the gear position at the time of starting-off operations. If, for example, the instantaneous weight of the motor vehicle or the inclination of the motor vehicle with respect to the horizontal is memorised in association with values indicating the wear, then for example it can be ascertained that increased wear of the clutch is not attributable to incorrect operation by the driver of the vehicle, but due to frequently high loading of the motor vehicle or by frequent hill-starts. Furthermore, if the acceleration of the motor vehicle at the time of the starting-off operation is memorised in association with the values indicating wear, then it is possible to exclude for example that increased wear on the clutch is attributable to excessive accelerations at the time of starting-off operations.

The memory may comprise a plurality of storage locations, one storage location being associated with each starting-off operation, in which the value indicating wear as well as at least one piece of information about the condition and possibly also the clock time, at which the respective starting-off operation took place, are memorised, which facilitates the retrospective analysis of individual starting-off operations.

Preferably the memory comprises a plurality of storage locations, of which each associated with a predetermined range of values of load information and a value or range of values at least one of the pieces of information regarding condition. In this case, at the time of each starting-off operation, the memory increments that storage location which in its association corresponds to the value of the at least one piece of information regarding condition and the value of the load information. Thus, each storage location represents the number of starting-off operations, at which the values of the load information associated therewith lay in the predetermined range of the value of the load information associated with the storage location and at the same time the individual values of the pieces of information regarding condition were equal to the value of the corresponding piece of information regarding condition associated with the storage location or lay in the range of values of the corresponding piece of information regarding condition associated with this storage location. The entire memory thus memorises a frequency distribution, from which it is possible to ascertain the proportion of starting-off operations, in which classified values of the load information and of the at least one piece of condition information occurred.

For a particularly accurate determination of the load information, the wear-detection

unit also preferably uses clutch torque information, which represents the torque instantaneously occurring on the input side of the friction clutch. For example the load information can be determined in that the value of the torque applied to the friction clutch is multiplied by the slippage of the friction clutch, i. e. by the difference between the speed of the output side of the friction clutch and the speed of the input side of the friction clutch. In order to determine the clutch torque information, the wear-detection unit uses engine torque information representing the torque produced instantaneously by the internal combustion engine, which information is supplied by a circuit for determining engine torque. A sensor for determining engine torque may determine the engine torque information from the value of the engine speed and the quantity of fuel supplied instantaneously to the engine, with the assistance of engine data. In this case, the sensor for determining engine torque may also furthermore use information about for example air pressure prevailing on the vehicle and the air temperature.

The engine torque information generally corresponds only approximately to the clutch torque information representing the torque instantaneously applied to the input side of the friction clutch, at the time of acceleration operations. Therefore, for determining the clutch torque information, the wear-detection unit corrects the engine torque information with a value which is determined from acceleration information representing the instantaneous rotary acceleration of the input side of the friction clutch and a predetermined value essentially representing the moment of inertia of the internal combustion engine and of the input side of the friction clutch. The acceleration information can be calculated from the time dependence of the first speed information supplied by the first tachometer or can be supplied by a separate acceleration sensor provided on the internal combustion engine or at the input side of the friction clutch.

The invention may be understood more readily, and various other aspects and features of the invention may become apparent, from consideration of the following description.

An embodiment of the invention will now be described in detail hereafter and by way of example, with reference to the accompanying drawing, in which: Figure 1 is a block schematic diagram representing a first embodiment of an arrangement for monitoring the state of wear of a friction clutch constructed in accordance with the invention and Figure 2 shows a memory correlation of a memory used in the embodiment shown in Figure 1.

In the arrangement illustrated in Figure 1, a wear-detection unit Ic determines load information representing the wear on the friction clutch in the driving line of a motor vehicle driven by an internal combustion engine at the time of the starting-off operation, from the torque instantaneously present on the input side of the friction clutch and the slippage occurring between the output side and the input side of the friction clutch. For this purpose, the wear-detection unit Ic reads-in the value of the torque instantaneously produced by the internal combustion engine, which value is supplied by a device 25 for determining torque. The device 25 for determining torque determines the engine torque value from the position of the throttle valve of the internal combustion engine, supplied by a throttle valve sensor 23, and a value of the engine speed supplied by the engine tachometer 3c. Since the throttle valve position represents the quantity of fuel supplied to the internal combustion engine at a given engine speed, the device 25 for determining engine torque, with the assistance of a data memory 27, the engine data of which it interrogates depending on the values of the throttle valve position and the engine speed, can determine the value of the torque produced by the internal combustion engine and supply it to the wear-detection unit Ic.

The torque value supplied by the device 25 for determining engine torque reproduces only approximately the torque value instantaneously present at the input side of the friction clutch, since acceleration effects of the internal combustion engine and of the input side of the friction clutch cannot be taken into consideration by the device 25. In order to determine more accurately the torque value present at the input side of the friction clutch, the wear-detection unit Ic corrects the engine torque value supplied by the device 25, with a value which depends on the rotary acceleration, i. e. on the change in the rotary speed of the input shaft of the friction clutch. The instantaneous engine speed value supplied by an engine tachometer 3c and an engine speed value preceding it by a predetermined time interval. This calculated rotary acceleration value is multiplied by a predetermined value, taking into consideration a factor, which depends for example on the time difference existing between the engine speed values used for the formation of the difference, which essentially represents the moment of inertia of the rotating parts of the internal combustion engine and of the input side of the friction clutch and for example can be determined empirically. This value is added to the engine torque value supplied by the device 25 or is subtracted from the latter, so that in the case of a positive rotary acceleration of the engine, i. e. of an increasing speed of rotation of the engine, the engine torque value is reduced an din the case of a negative rotary acceleration, this value is increased. The wear-detection unit Ic uses the result of this calculation as the torque value instantaneously present on the input side of the friction clutch and multiplies it by the instantaneous slippage of the friction clutch, which it calculated from the difference between the value of the output speed of the friction clutch supplied by a tachometer 21c and the value of the input speed of the friction clutch supplied by the engine tachometer 3c. The result of this calculation represents the energy instantaneously consumed in the friction clutch. The wear-detection unit I c integrates these energy values, beginning with the beginning of the starting-off operation and up to the end of the clutching operation, in order to supply the result as load information representing the wear at the time of the associated starting-off operation, to an indicating device/memory 13c.

The device 13c memorises a plurality of values indicating the wear of the friction clutch, which values are determined from the load information associated with part starting-off operations, in which case the values indicating wear are memorised in associated with gear position information, which is supplied by a gear detection device 29 as a gear position value. The gear detection device 29 can determine the instantaneously engaged gear either by comparison of the instantaneous travelling speed value with the engine speed value or by way of a gear position sensor provided separately on the gear-change mechanism of the motor vehicle.

The memory of the device 13c comprises a plurality of storage locations 31, depicted schematically in Figure 2 whereof each is associated with a predetermined range of values of the load information and a value of the gear position information. The memory 13c has sixteen storage locations, which, as shown in Figure 2, can be arranged in the form of a matrix. Each row of this matrix with respectively four storage locations 31 is in this case associated with a range of values of the load information, and each column of the matrix with respectively four storage location is associated with a value of the gear position of four possible gear positions of the gear-change mechanism. The ranges of values of the load information are in this case four adjoining partial ranges of a range on a scale of numerical values between 0 and 100, of the load information supplied by the wear-detection unit 1 c.

If, at the time of a starting-off operation, the load information adopts for example a value B in the range of values 25 < B 50 and the third gear is selected at the time of the starting-off operation, the storage location designated by the reference numeral 31'is incremented, i. e. the value 1 is added to its storage contents. Thus, as the values indicating wear, the individual storage locations 31 respectively contain the number of the starting-off operations, at which the load information lay in the range of values of the load information associated with the respective storage location and the gear position engaged is equal to the gear position value associated with the corresponding storage location 31.

On the occasion of interruptions for the maintenance of the motor vehicle, the contents of the memory can be read out and analysed and conclusions can be drawn as to the occurrence of for example conspicuously increased wear on the clutch. If it becomes apparent from the analysis for example that starting-off was undertaken comparatively frequently with a high gear, thus in third and fourth gear, then the driver of the vehicle can be urged as far as possible to start off in a lower gear, in the future.

To supplement the gear position information, or as an alternative thereto, the memory of the device 13c may memorise the values indicating wear also in association with further values or ranges of values of additional information. The latter may be ranges of values of weight information supplied by a weight sensor 33 and representing the instantaneous weight of the motor vehicle, ranges of values of inclination information supplied by an inclination sensor 35 and representing the instantaneous inclination of the motor vehicle in the direction of travel, at the time of the starting-off operation, and/or ranges of values of acceleration information supplied by an acceleration monitoring device 37, representing the acceleration of the motor vehicle at the time of the starting-off operation. This additional information is in this case, like the gear position information, information about features of the starting-off operation, which are particularly relevant for wear on the friction clutch. Thus, for example, the choice of a high gear position or a high vehicle weight caused by too high a load, or a great inclination of the motor vehicle with respect to the horizontal, occurring at the time of a hill start, or a great acceleration of the motor vehicle at the time of the starting-off operation, leads to increased wear on the clutch.

If more than one piece of additional information is associated with the values indicating wear, then the arrangement of the storage locations in an illustration as a matrix according to Figure 2 may be supplemented to form an array of storage locations of higher dimension, for example an at least cubic array.

Apart from the additional information indicated in the description of Figure 1, it is conceivable to memorise further additional information, such as for example an identification representing a certain vehicle driver from a plurality of vehicle drivers or a characterisation representing the connected state of a trailer, in association with values indicating the wear.

Claims

Claims 1. Arrangement for monitoring the state of wear of a friction clutch in the driving line of a motor vehicle driven by an internal combustion engine, comprising a weardetection unit (lu) supplying load information as a measurement of the load on the friction clutch at the time of a starting-off operation and a memory (13c) for memorising a plurality of values indicating the wear on the friction clutch, which values are determined from load information associated with starting-off operations, wherein the memory (13c) memorises values indicating wear in association with at least one information regarding condition from a quantity of information, which comprises: gear position information from a gear-monitoring device (29) representing the gear position of a gear-change mechanism of the motor vehicle engaged at the time of the starting-off operation and/or weight information from a weight sensor (33) representing the instantaneous weight of the motor vehicle and/or inclination information from an inclination sensor (35) representing the inclination of the motor vehicle with respect to the horizontal in the direction of travel at the time of the starting-off operation and/or acceleration information from an acceleration-monitoring circuit (37) representing the acceleration of the motor vehicle at the time of the starting-off operation.
2. Arrangement according to claim 1, wherein the memory comprises a plurality of storage locations (31), each of which is associated with a predetermined range of values of the load information and a value or range of values of at least one of the pieces of information regarding condition whereby at the time of each starting-off operation, the memory (13c) increments that storage location (31) which corresponds in its association with the value of the at least one piece of information regarding condition and the value of the load information.
3. Arrangement according to claim 1 or 2, wherein the wear-detection unit (Ic) also determines the load information from clutch torque information representing the torque instantaneously present on the input side of the friction clutch, the engine torque information being supplied by a device (25) for determining engine torque and representing the torque instantaneously produced by the internal combustion engine, and the wear-detection unit (Ic) corrects the engine torque information by a value which is determined from acceleration information representing the instantaneous rotary acceleration of the input side of the friction clutch and a predetermined value essentially representing the moment of inertia of the internal combustion engine and of the input side of the friction clutch.
4. Arrangement for monitoring the state of wear of a friction clutch substantially as described with reference to and as illustrated in the accompanying drawings.
5. A method of monitoring the state of wear of a friction clutch of a motor vehicle utilising a wear-detection unit (Ic) to supply load information as a measurement of the load on the friction clutch storing successive load values in a memory and storing further information in the memory during the vehicle start-off based on one or more of : i) the gear position of a gear-change mechanism engagement; ii) the weight of the motor vehicle; iii) the inclination of the motor vehicle with respect to the horizontal and iv) the acceleration of the motor vehicle.
6. A method according to any one of claims 1 to 5 and further comprising providing a load signal based on the evaluation operation to an indicator.
7. A method of monitoring the state of wear of a friction clutch of a motor vehicle substantially as described with reference to and as illustrated in the accompanying drawings.

7. A method of monitoring the state of wear of a friction clutch of a motor vehicle substantially as described with reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows I, Claims

1. Arrangement for monitoring the state of wear of a friction clutch in the driving line of a motor vehicle driven by an internal combustion engine, comprising a weardetection unit (Ic) supplying load information as a measurement of the load on the friction clutch at the time of a starting-off operation and a memory (13c) for memorising a plurality of values indicating the wear on the friction clutch, which values are determined from load information associated with starting-off operations, wherein the memory (13c) memorises values indicating wear in association with at least one information regarding condition from a quantity of information, which comprises: gear position information from a gear-monitoring device (29) representing the gear position of a gear-change mechanism of the motor vehicle engaged at the time of the starting-off operation and/or weight information from a weight sensor (33) representing the instantaneous weight of the motor vehicle and/or inclination information from an inclination sensor (35) representing the inclination of the motor vehicle with respect to the horizontal in the direction of travel at the time of the starting-off operation and/or acceleration information from an acceleration-monitoring circuit (37) representing the acceleration of the motor vehicle at the time of the starting-off operation. 2. Arrangement according to claim 1, wherein the memory comprises a plurality of storage locations (31), each of which is associated with a predetermined range of values of the load information and a value or range of values of at least one of the pieces of information regarding condition whereby at the time of each starting-off operation, the memory (13c) increments that storage location (31) which corresponds in its association with the value of the at least one piece of information regarding condition and the value of the load information.

3. Arrangement according to claim I or 2, wherein the wear-detection unit (Ie) determines the load information from engine torque information supplied by a device (25) for determining the engine torque and representing the torque instantaneously produced by the internal combustion engine, and the wear-detection unit (Ic) corrects the engine torque information by a value which is determined from acceleration information representing the instantaneous rotary acceleration of the input side of the friction clutch and a predetermined value essentially representing the moment of inertia of the internal combustion engine and of the input side of the friction clutch.

4. Arrangement for monitoring the state of wear of a friction clutch substantially as described with reference to and as illustrated in the accompanying drawings. 5. A method of monitoring the state of wear of a friction clutch of a motor vehicle utilising a wear-detection unit (Ic) to supply load information as a measurement of the load on the friction clutch storing successive load values in a memory and storing further information in the memory during the vehicle start-off based on one or more of : i) the gear position of a gear-change mechanism engagement ; ii) the weight of the motor vehicle ; iii) the inclination of the motor vehicle with respect to the horizontal and iv) the acceleration of the motor vehicle.

6. A method according to claim 5 and further comprising utilizing an indicator to display the value of the load information.