GB2331792A

GB2331792A - Method and device for controlling a clutch

Info

Publication number: GB2331792A
Application number: GB9904327A
Authority: GB
Inventors: Klaus Kuepper
Original assignee: LuK Getriebe Systeme GmbH
Current assignee: LuK Getriebe Systeme GmbH
Priority date: 1997-07-05
Filing date: 1998-07-03
Publication date: 1999-06-02
Anticipated expiration: 2018-07-03
Also published as: WO1999001312A1; DE19829835A1; GB9904327D0; FR2765644A1; DE19880849D2; FR2765644B1; KR20000068477A; GB2331792B; BR9806019A; AU9251698A

Abstract

The invention relates to a method for controlling the operation of a clutch positioned between a drive engine and a manual gear mechanism in the power train of a motor vehicle. According to said method, any actuation of the gear lever of the gear mechanism is detected and, if certain requirements are met, identified as an intention to change gears, after which the clutch is opened if an intention to change gears has been identified. The conditions determining identification of an intention to change gears are modified when such an intention to change gears is identified for longer than a predetermined period or if more than a predetermined number of intentions to change gears is identified during a predetermined period or if the motor vehicle is travelling on a poor road which results in relative movements between the gear lever and gear mechanism or if a play between the gear lever and gear elements within the gear mechanism changes.

Description

2331792 METHOD AND DEVICE FOR CONTROLLING A CLUTCH The invention relates

to a method and device for controlling the operation of an automated clutch mounted in the drive train of a vehicle having a drive motor and a gearbox.

The automation of clutches in connection with manual gear shifts is becoming increasingly preferred. The automation of the clutch not only improves the operating comfort of a vehicle; it is also a means of reducing fuel consumption since it encourages more frequent gear change and thus more frequent driving in the most economical gear. Likewise an automatically operated clutch with automated shift gears is advantageous wherein manual gear shifts are operated automatically by a controllable actor.

In the case of an automatically operable clutch the driver's wish to change gear has to be recognised in order to open the clutch and thereby facilitate the gear change or indeed only then make it possible. A sensor detects the driver's wish to change gear, for example through a sensor in/on the manual shift lever or gearbox and the control unit of the automated system processes this signal and produces a shift intent signal whereupon the clutch is disengaged by way of example when changing gear. If in the event of this shift intent there results a faulty functioning, more particularly an undesired opening of the clutch then this can have many negative consequences.

These include loss of comfort, high clutch strain, increased load on the clutch actor etc.

The object of the invention is to further develop a method of the type already described so that a shift intent is reliably detected each time. A further task is also to P2350.P3 24 February 1999 1 1 - 2 detect a shift intent when the driver's wish to change gear exists through activation of an element and likewise to recognise that there is no intent to shift gear when this signal is not present. The object of the invention is also to provide a device for implementing the method according to the invention.

The subsidiary claims 1, 2, 12 and 15 are directed to solutions to the part of the inventive task relating to the method.

With the features of claim 1 it is reached that a permanent or unusually long activation of the shift lever or a supposed activation of the shift lever possibly on account of play of the shift lever in the external shift unit which normally leads to a corresponding shift intent identification is established which then leads to suppression of the shift intent identification.

With the features of claim 2 it is reached that an unusually quick succession of identifications of a shift intent which can be due to operating errors or for example vibrations in the drive train or signal breakdowns which are transferred to the shift lever is detected and leads to a suppression of the shift intent.

With the features of claim 3 it is reached that the suppression of the shift intent can advantageously be adapted to the relevant operating conditions of the vehicle and/or drive train, for example to the relevant engaged gear, to the driving speed, to the activation of the brake, engine speed, gearbox speed etc.

P2350.P3 24 February 1999

Claims

Claims 4 to 11 are directed to advantageous examples of changing the

conditions for the identification of the shift intent.

With the features of claim 12 possible influences on the identification of a shift intent through a poor road surface are suppressed.

According to claims 13 or 14 it is advantageous to increase the threshold values which when exceeded are a condition for the identification of a shift intent, i.e. to make the detection of the shift intent more insensitive.

With the features of claim 15 it is reached that Play in the transmission path from the shift lever to the shift members in the gearbox is taken into account and not erroneously identified as a shift intent.

Claims 16, 17 and 18 are each directed to a particularly advantageous practical way of carrying out the method according to the invention.

Claim 19 characterises the basic construction of a device for implementing the method according to the invention. Claims 20 and 21 represent advantageous embodiments.

The invention will now be explained below by way of example and in further detail with reference to the drawings in which:

Figure 1 is a block circuit diagram of a motor vehicle fitted with an automated clutch and manual gear shift; P2350.P3 24 February 1999 4 Figure 2 shows some details of the shift activation according to Figure 1; Figures 3,4 are graphs explaining two examples of implementing the method according to the 5 invention and Figure 5 shows an assembly of a gearbox with operating element such as shift lever.

According to Figure 1 a motor vehicle has an internal combustion engine 2 serving as drive motor and connected by a clutch 4 to the shift transmission 6. A gear or shift lever 7 serves to shift the shift transmission 6. The driven wheels, such as for example the rear wheels 12 or the front wheels or both the rear wheels and the front wheels are driven from the shift transmission 6 through a cardan shaft 6 and a differential 10. A brake unit 14 with brake device 16 operated by a brake pedal 18 is used to brake the vehicle. Preferably all the wheel brakes are operated from the brake device 16 whereby only the lead to the left front wheel is shown.

A drive pedal 20 serves to control the load on the internal combustion engine 2 and the position of the drive pedal is detected by a position sender unit 21 and sent to a control device 22. An actor 23 for operating a throttle valve 24 is controlled by the control device 22.

The clutch 4 is automated and is operated by an actor 25 through a master cylinder 27 and slave cylinder 29. The 30 actor 25 is controlled by the control device 21 which contains in known way a microprocessor with associated memories and whose inputs are connected to different sensors of the drive train, by way of example a sensor 32 for the speed of the internal combustion engine, a sensor 34 for the wheel speed, a sensor 36 for detecting the P2350.P3 24 February 1999 - 5 position of the shift lever 7, a sensor 37 for detecting the shift lever operation, a sensor for detecting the position of the clutch 4, a sensor 40 for the position of the actor, 25, a sensor 42 for detecting the coolant temperature, a sensor 44 for detecting the temperature of the suction intake air as well as where applicable further sensors. The sensors or electronics units can transfer the sensor signals to the control unit also through a data bus such as a CAN bus.

The slave cylinder 29 interacts directly with a clutch lever 48 or indirectly through a rod linkage which is forced by a clutch resetting spring (not shown) such as plate spring into its rest position in which the clutch 4 is completely closed, i.e. can transfer its maximum moment.

The function of the different arrangements is such that during activation of the shift lever 7 which is detected by means of the sensors 36 and/or 37 or further sensors arranged inside/outside the gearbox 6, the control unit 22 determines by means of algorithms recorded/ implemented in same as software or hardware, whether the shift lever activation expresses the wish of the driver or not. if identifying a wish to change gear then the actor 25 is controlled by the control device 22 so that the clutch 4 is opened. The actor 23 for the throttle valve 24 can thereby be controlled at the same time so that despite an activated drive pedal 20 the throttle valve 24 closes during the shift process. If the control device 22 recognises from the sensor 36 and/or further sensors within the manual transmission 6 that a shift process has been completed then the clutch is closed and the throttle valve 24 occupies the position corresponding to the position of the drive pedal 20. A pedal value sender unit P2350.P3 24 February 1999 of the accelerator pedal and/or a brake light switch which detects the activation of a brake can further be used.

The control unit for controlling the automated clutch operation can be in signal connection with other control units. These control units can thereby exchange data for example through a data bus. Such signals can be for example data on the state of the road.

The shif t linkage or members a gearbox and The axial corresponds lever 7 operates indirectly through a rod Bowden cable or directly through transmission shift shaft 52 which is mounted inside the can be swivelled and moved axially to and fro. to and fro movement of the shift shaft 52 to a selection movement; the swivel movement corresponds to a shift movement. The shift shaft 52 has a shift finger 54 which projects into shift forks 56 which are mounted linearly displaceable on the gearbox housing and can be moved to and fro between two end positions wherein the shifting of a gear corresponds with each end position. The end position of the shift forks 56 are detected by micro switches 58 of which only those on the right hand side are shown in Figure 2. The selection movement of the shift shaft is detected by a sensor 60 and the shifting movement is detected by a sensor 62.

The sensor fitting of the gearbox can be very different according to the requirements and sensors selected. By way of example the sensor 37 which is provided directly in 30 the knob of the shift lever 7 according to Figure 1 and which can respond to a mere touch and/or can detect the operating force can be completely omitted and can be replaced by one or more sensors, for example the sensors 60 and 62 which detect the movement of the shift lever 7 or shift shaft 52 whereby from the movement signal a P2350-P3 24 February 1999 signal can be derived which indicates the operating speed of the shift lever 7 or shift shaft 52.

As already explained at the beginning a reliable detection of the shift intent is an absolute prerequirement for a satisfactory operation of the clutch 4. It is thereby in the nature of things that the detection of the shift intent only becomes active each time for the short period of the gear change. As soon as a gear is disengaged (detectable through the signal of the micro switch 58 and/or the signal of the sensor 62) or the driver changes his shift intent, i.e. keeps the old gear, then the shift intent detection no longer responds. Since the clutch does not close so long as a shift intent is detected it is expedient to change the conditions within the control device for identifying a shift intent if a shift intent is identified constantly beyond a predetermined time length. The long duration of a shift intent can be conditioned by a fault in one of the sensors or even in the control device or in that the driver has for example not released the shift lever after executing a gear change and is identified as a shift intent when a force exerted on the gear lever knob exceeds a predetermined value. The length of time which leads to a change of the shift intent can be constant, it can be selected different from gear to gear and depending on the driving situation. it is advantageous to select the length of time short in the event of high load demands by the driver and for example to extend it in the case of coasting since when coasting from experience the shift lever is operated very slowly.

The consequences of a shift intent which exists beyond the predetermined length of time can be different. On the one hand the shift intent can be cancelled if its identification stops beyond the predetermined length of P2350.P3 24 February 1999 t ime. On the other hand a threshold value, for example the level of force with which the shift lever 7 has to be operated to trigger a shift intent, can be increased to prevent or terminate the release.

Figure 3 shows an example of how the threshold S which when exceeded leads to the release of a shift intent, can be dynamically changed. t indicates the time. The solid curve shows how the at first low threshold is increased in stages until it is greater at time point 1 than the operating force so that the shift intent is cancelled. From time point 2 the threshold is lowered in stages in order to keep to the ideal value shown by dotted lines. The associated adaptation methods or programs are laid down in the control device 22.

Another problem case when identifying the shift intent is as follows:

If a driver changes his shift intent for example, i.e. he initially operates the shift lever with a predetermined force or over a predetermined path, in order then however not to change gear, and does this even repeatedly, then this leads each time where applicable to a temporary shift intent detection with associated opening of the clutch. In order to suppress such states which lead to a rapid change between shift intent identification and no existing shift intent, it is advantageous to change the conditions for identifying a shift intent if within a predetermined length of time more than one predetermined number of shift intents were identified. The change in the conditions can exist for example in that after identification of closely following shift intents the shift intent is cancelled over a predetermined length of time. It is also possible to monitor the path of the shift lever or another element of P2350-P3 24 February 1999 - 9 the shift unit, for example the shift shaft 52 and to suppress a shift intent identification if a certain path is covered after (or before) the shift intent.

One possibility which can lead to a faulty shift intent identification is travelling over poor or uneven roads which lead for example to inherent vibrations in the shift lever 7 which can be identified erroneously as a shift intent. In order to rule out such errors travelling over poor roads can be sensed for example in that in a bearing (not shown) of the engine/gearbox unit on the chassis movement amplitudes and frequencies of the bearing are detected and supplied as corresponding signals to the control unit 22. In the control device 22 the threshold values which have to be exceeded to identify a shift intent can be raised and lowered again according to the road surface signals whereby these threshold values can temporarily be raised so far that a shift intent is basically not detected. False identifications of a shift intent can be avoided in this way. It is obvious that the increase in the threshold value can be dependent on the intensity of the interference through the road surface. Furthermore individual shocks, such as through potholes or cambers on the road surface can be detected in order to impede the identification of the shift intent for the short period of time that such disturbances have an effect.

Detecting a poor road surface is possible in various different ways such as for example as described by sensors on the bearings of the engine/gearbox unit on the chassis, or by detecting the relative movements of the wheels relative to the body work, by evaluating irregularities in the wheel speed signals etc.

P2350.P3 24 February 1999 1 - 10 A strategy shown with reference to Figure 4 has proved successful in practice as a criterion for the shift intent detection. The path SW is detected which is covered by the shift lever, and the speed SG is detected with which the shift lever is operated. The shift lever speed SG can be obtained for example from a differentiation of the signals of the path sensors. As apparent with low shift speeds a larger shift path is required to detect a shift intent. As the operating speed of the shift lever increases so the shift lever path SW asymptotically approaches a straight line 0 which is drawn in by dotted lines, which indicates an offset value for the shift lever path which has to be overcome in each case so that a shift intent is detected or is evaluated as being present. In order to rule out a faulty identification of a shift desire the off-set value 0 must in each case lie above the play which the shift lever has relative to the shift forks 56 (Figure 2) since for example on poor roads or as a result of inherent movement of the engine/gearbox assembly in the event of sudden severe torques or fluctuations of the torque it is possible to move over this path without accompanied by a shift intent consciously introduced by the driver.

There are various different possibilities for determining the play which can change during the course of operation:

By way of example the neutral positions can be sensed using the sensor 62 (Figure 2) and their maximum and minimum values detected. The difference from the two values is a measure of the play of the external shift 30 unit, i.e. in the transmission path between the shift lever 7 and shift forks 56. It is obvious that the neutral position is then sensed for example by means of the sensor 62 only when the shift state N exists for a predeterminable length of time At, which can be recognised P2350.P3 24 February 1999 - 11 by means of the sensor 60. The sensed maximum and minimum values are recorded as adaptive parameters in the control device 22 and used in suitable operating phases for the adaptation of the off-set value 0 (Figure 4) The complete solid line curve of Figure 4 is displaced in this way with increasing play, that is upwards with increasing off-set 0. The difference between the maximum value and the minimum value corresponds substantially to the play taking into account where applicable predeterminable factors or summands. If the play changes during operation then the difference between the above signals changes. The control unit can thereby bind the offset value 0 to the changed difference by always taking into account an additional summand and/or factor.

0 = Factor (Maximum value tZ minimum value) + summand.

As a further solution according to the invention it can be proposed that the uncoupling thresholds of the shift intent detection are detected through a difference path method, as difference path between the sensors 104 and 120 of Figure 5 with the operation of the device according to the invention.

Regarded as uncoupling thresholds are those values which arise from the maximum extension or difference path between the sensor data of the sensors 104 and 120, thus 25 at the gearbox and at the shift lever during a shift process. This maximum difference path detected during a shift process can then be converted or processed to an uncoupling threshold. These uncoupling thresholds can be the same for groups of gears such as 1, 3, 5 gear and 2, 4 30 and R gear or can be different for all gears. The changes in the uncoupling thresholds during operation of the device according to the invention are detected and used as a measure for the change in the play or the elasticity in P2350.P3 24 February 1999 the external shift unit. By changing the external shift unit it is possible to adapt the value 0 of the offset.

Furthermore to adapt the value 0 it is possible to detect the extension of the external shift unit, thus the difference path between the sensors 104 and 120 in a predeterminable range, such as the neutral range, whereby an increase in this extension, such as difference path, can be used to increase the value 0.

Figure 5 shows in an assembly 100 a gearbox 101 with a central shift shaft 102 which is in active connection with shift elements 103 inside the gearbox. Through the axial and/or rotary movement of the central shift shaft 102 the gears are shifted within the gearbox 101. The axial movement of the central shift shaft 102 is detected by the sensor 104 whereby the rotary movement of the central shift shaft 102 is detected by the sensor 105. The sensors are connected to the central shift shaft through levers and connecting elements 106, 107, such as rod linkage. The operation or position of the central shift shaft 102 can be detected by the deflection of the sensor elements.

The shift lever 110 is connected to the centralshift shaft through the connection 111, 112 and 113 such as rod linkage or Bowden cable. The central shift shaft 102 is turned about its axis through a swivel movement of the shift lever. Through the longitudinal movement of the shift lever the shift shaft is operated in the axial direction. The longitudinal movement takes place substantially along the shift gates to reach the gear positions or neutral position. The swivel movement is carried out to select the shift gates. In this respect the shift slide gate 119 is shown. The shift slide gate is shown by way of example for a gearbox with five forward P2350.P3 24 February 1999 - 13 gears and one reverse gear. Similarly any other type of gearbox can be used. The sensor 120 detects the longitudinal movement of the shift lever. At least some of the sensors 104, 105 and 120 can be designed as potentiometers, echo sensors and/or other sensors.

Through the movement of the shift lever 110 it is possible to detect shift intent by means of the sensor 120. Likewise a difference path can be detected between the sensors 104 and 120 when the mechanical stretch 111, 113a, 113b and 102 between the sensors 104, 120 has a predeterminable elasticity and this stretch is compressed or stretched during activation of the shift lever 110. If the detected difference exceeds or falls below a threshold value then a shift intent is detected.

Instead of having one rotatable or rotary central shift shaf t the gearbox shown in Figure 5 can also be f itted with more than one shift shaft which are rotatable or axially displaceable.

If a false notification occurs which is generated through faulty sensor signals from the control unit then itis possible to switch over for example into another branch of the program or into an emergency program or replacement strategy whereby the shift intent detection used can be changed. Different methods can thereby be used for example and/or threshold values can be changed. Cancelling of the shift intent can thereby take place until the neutral area of the gearbox is detected. The correction or change to the shift intent thresholds can be carried out individually for each gear or jointly for groups of gears. The change can thereby be dependent on at least one vehicle operating parameter such as can be increased or reduced.

P2350.P3 24 February 1999 11 14 The patent claims filed with the application are proposed wordings without prejudice for obtaining wider patent protection. The applicant retains the right to claim further features disclosed up until now only in the description and/or drawings.

References used in the sub-claims refer to further designs of the subject of the main claim through the features of each relevant sub-claim; they are not to be regarded as dispensing with obtaining an independent subject protection for the features of the sub-claims referred to.

The subjects of these sub-claims however also form independent inventions which have a design independent of the subjects of the preceding claims.

The invention is also not restricted to the embodiments of the description. Rather numerous amendments and modifications are possible within the scope of the invention, particularly those variations, elements and combinations and/or materials which are inventive for example through combination or modification of individual features or elements or process steps contained in the drawings and described in connection with the general description and embodiments and claims and which through combinable features lead to a new subject or to new process steps or sequence of process steps insofar as these refer to manufacturing, test and work processes.

P2350.P3 24 February 1999 - is - PATENT CLAIMS 1. Method for controlling the operation of a clutch mounted in the drive train of a motor vehicle having a drive motor and a manual gear shift wherein activation of an operating element such as for example the shift lever of the gearbox is detected by means of at least one sensor and when certain conditions of the sensor signals are fulfilled is identified as a shift intent and when the shift intent is identified the clutch is opened, characterised in that the conditions for identifying the shift intent are changed when a shift intent is identified constantly over a predetermined length of time.
2. Method for controlling the operation of a clutch mounted in the drive train of a motor vehicle having a drive motor and a manual gear shift wherein activation of an operating element such as for example the shift lever of the gearbox is detected by means of at least one sensor and when certain conditions of the sensor signals are fulfilled is identified as a shift intent and when the shift intent is identified the clutch is opened, characterised in that the conditions for identifying a shift intent are changed when more than a predetermined number of shift intents are identified within a predetermined length of time.
3. Method according to claim 1 or 2 characterised in that the conditions for identifying a shift intent are changed in dependence on the operating state of the drive train or of the vehicle.

P2350.P3 24 February 1999 16
4. Method according to claim 3 characterised in that the predetermined length of time and/or the predetermined number is a function of the gear engaged in the gearbox.
5. Method according to claim 4 characterised in that the predetermined length of time and/or the predetermined number is the same for each gear such as forward drive gear and/or reverse drive gear.
6. Method according to claim 4 characterised in that the predetermined length of time and/or the predetermined number is different for each gear, such as forward drive gear and/or reverse drive gear.
7. Method according to claim 4 characterised in that the predetermined length of time and/or the predetermined number is different for groups of gears.
8. Method according to claim 1 characterised in that the predetermined length of time is shorter when there is a high load on the drive motor than when coasting and/or the predetermined number is less when there is a high load on the motor than when coasting.
9. Method according to claim 1 characterised in that the shift intent is cancelled when its identification stops beyond the predetermined length of time.
10. Method according to claim 1 characterised in that the shift intent is cancelled when its identification exists in a predeterminable time span beyond a predeterminable number.
11. Method according to claim 10 characterised in that the shift intent is cancelled when within a time span of P2350.P3 24 February 1999 0.2 s to 3 s a predeterminable number of shift intent signals is in the range from 2 to 30, preferably 3 to 10 signals in the time span from 0.5 s to 1.5 s.
12. Method for controlling the operation of a clutch mounted in the drive train of a motor vehicle having a drive motor and a manual gear shift wherein activation of an operating element such as for example the shift lever of the gearbox is detected by means of at least one sensor and when certain conditions of the sensor signals are fulfilled is identified as a shift intent and when the shift intent is identified the clutch is opened, characterised in that the conditions for identifying a shift intent are changed in the event of a vehicle driving on an uneven road so that relative movements induced by the road between the shift lever and gearbox in the event of identification of the shift intent are suppressed at least in part.
13. Method according to at least one of claims 1 to 12 characterised in that a threshold value for the activation of the operating element which when exceeded is a condition for the identification of a shift intent is increased.
14. Method according to claim 13 characterised in that the threshold value is an operating path or an operating force or a differential path in the event of activation of the operating element.
15. Method for controlling the operation of a clutch mounted in the drive train of a motor vehicle having a drive motor and a manual gear shift wherein activation of an operating element such as for example the shift lever 35 of the gearbox is detected by means of at least one sensor P2350.P3 24 February 1999 and when certain conditions of the sensor signals are fulfilled is identified as a shift intent and when the shift intent is identified the clutch is opened, characterised in that the operating path of the operating element such as for example shift lever, and a play between the operating element and shift members within the gearbox are detected.
16. Method according to claim 15 characterised in that in the event of detection of a play a shift intent is only then identified if the detected operating path is greater than the play.
17. Method according to claim 15 or 16 characterised in that in addition the operating speed of the operating element such as for example the shift lever is detected and that a shift intent is identified when the operating path is above a threshold value.
18. Method according to claim 17 characterised in that the threshold value increases as the operating speed increases.
19. Device for controlling the operation of a clutch 25 mounted in the drive train of a motor vehicle between a drive motor and a manual gear shift, containing an actor controlled by a control device for operating the clutch, at least one sensor for detecting an operation of a shift lever for shifting the gears, as well as a microprocessor 30 contained in the control device for evaluating the sensor signals and for identifying a wish to shift gear when the sensor signals fulfil predetermined conditions laid down in a program memory, wherein the microprocessor when the intention to change gear is identified produces a control 35 signal for controlling the actor of the clutch, and with a P2350.P3 24 February 1999 19 device for changing the conditions laid down in the program memory for identifying a desire to change gear according to a program of change laid down in the program memory.
20. Device according to claim 19 characterised in that to check that the sensor signals meet predetermined conditions a comparison is carried out between the actual values of the sensor signals and the ideal values stored in the memory.
21. Device according to claim 19 characterised in that to check that the predetermined conditions are met actual values processed previously by the control unit from sensor signals into control signals are compared with ideal values.

P2350.P3 24 February 1999