GB2339866A

GB2339866A - Transmission with erroneous shift intent detection

Info

Publication number: GB2339866A
Application number: GB9913591A
Authority: GB
Inventors: Mario Jung
Original assignee: LuK Getriebe Systeme GmbH
Current assignee: LuK Getriebe Systeme GmbH
Priority date: 1998-06-17
Filing date: 1999-06-14
Publication date: 2000-02-09
Anticipated expiration: 2019-06-14
Also published as: KR20000005745A; BR9902281A; ITMI991344A1; ITMI991344A0; GB9913591D0; GB2339866B; IT1312409B1; FR2780124A1; DE19915566A1

Description

2339866 MOTOR VEHICLE The invention relates to a motor vehicle having a

drive unit, such as for example a motor or an internal combustion engine, a gearbox and an automated torque transfer system such as for example clutch, friction clutch or magnetic powder clutch, wherein the transmission ratio can be selected by means of an operating element such as for example a shift lever, wherein at least one sensor detects the activation of the operating element and a control signal can be produced by a control device when the operating element is activated whereupon the torque transfer system is disengaged.

In the case of motor vehicles of this kind having automated torque transfer systems it is known from DE 17 55 528 that a shift process is only permitted through an activation of the operating element when the throttle valve is not activated.

In the case of technical systems such as in the case of the motor vehicles considered above even slight irregularities or faults can develop to have a critical effect on function or safety and which are unacceptable for reasons of functional reliability or for reasons of safety.

In a motor vehicle which has an automated torque transfer system which only permits a shift in the transmission when the accelerator pedal is not activated, i.e. with an activated idling switch which detects whether the accelerator pedal is in its rest position, a situation can occur which has a critical effect on function or safety if for example a defect appears in the area of the connection between the accelerator and engine, so that for example 2 the accelerator jams and the defect does not permit, even though the accelerator is not activated, the accelerator pedal to reset and activate the idling switch. in such an event the automated torque transfer system proceeds on the basis of the existing sensor values from the fact that the accelerator pedal has been intentionally activated for example by the driver and shifting of the transmission or changing of the gears is possible only with difficulty as a result of the torque transfer system which is not opening.

In a motor vehicle having an automated torque transfer system it is necessary if an activation of an operating element such as for example a shift lever, can lead to opening of the torque transfer system, if it appears plausible as a result of the sensor signals evaluated by a control unit, that this is also desired by the driver. However opening of the torque transfer system is not to take place in any situation, thus unintended interruption of the vehicle acceleration does not take place, if a shift process is not desired, such as for example at high engine speeds when a hand is placed on the operating element. This is achieved in DE 17 55 528 in that disengagement of the torque transfer system only takes place with a minimal throttle valve position.

In DE OS 196 50 450 an operating system is described by way of example wherein a sensor is provided for detecting the movement of the shift lever which thus detects a shift intent of the driver. The sensor signal of this sensor is evaluated in a control unit and if a shift intent is detected then the torque transfer system is disengaged and the driver can undertake a gear change by means of moving the shift lever. The subsequent engagement of the torque transfer system takes place like disengagement through an actor controlled by the control unit.

Operating systems of the type described where one or more sensors are provided for detecting the shift intent have the drawback that the shift intent is often detected although the driver does not have this intention, for example where the driver rests his hand on the shift lever and/or the shift lever is moved and/or loaded with forces through the acceleration and/or deceleration processes of the motor vehicle. Such situations where the torque transfer system disengages unintended arise particularly in the case of sudden changes of speed and/or immediately after shift processes if these are connected with corresponding accelerations or decelerations since the shift lever - particularly when the hand is resting thereon experiences relative acceleration which simulates a shift intent.

The object of the invention is therefore to provide a motor vehicle having a device previously described for operating a torque transfer system which permits reliable detection of the shift intent independent of the acceleration and deceleration processes of the motor vehicle. Furthermore it is the object of the invention to improve the functional reliability of the vehicles mentioned above and to provide such vehicles which are at the same time where appropriate capable of cost-effective manufacture.

This is achieved according to the invention in that in the corresponding operating states the signal coming from the sensor for detecting the shift intent is suppressed in a predetermined time interval. These operating states can 4 occur for example at high accelerations or decelerations of the motor vehicle.

Furthermore such operating states can arise in particular immediately after the engagement of the torque transfer system. According to the invention after engagement of the torque transfer system the control signal is suppressed and the operating element of the gearbox can execute during the predetermined time interval relative movements relative to the motor vehicle - for example when the hand on the operating lever is accelerated as well without the sensor signal for detecting the shift intent initiating the immediate disengagement of the torque transfer system. The length of the time interval can be predetermined as fixed and can stretch for example over two seconds, preferably 500 ms.

In an embodiment according to the invention the sensor for detecting the shift intent can be a path sensor which detects the path of the operating element through a change in the electrical resistance, or for example a force sensor which takes up the force required for moving the operating element. Adjusting the sensor signal can take place advantageously by the sensor adopting a measured value, as least in the starting or end position of the operating element, which (measured value) lies within its measuring range and not at the limits of the measuring range so that the measured stretch can be monitored by a plausibility check on the measured value to see whether it is understepped and/or overstepped or these measured values can be monitored for functioning. The evaluation area of a functionable shift intent detection is formed by sensor signals within these adjusted measured values which can be digitalized for easier processing in conventional computer memory units in the motor vehicle.

Advantageously the shift intent detection can then be recognised as given if the sensor signal thereby deviates by a value to be predetermined f rom the mean value of the sensor signal formed over a longer time and updated for example in the millisecond range. The computer unit then issues the control signal for disengaging the torque transfer system which is engaged again after completion of the gear change. From this moment in time the suppression of the shift intent signal is introduced, that is for example that for the predetermined time span the sensor signal can be set equal to the mean value of the sensor signals and thus the triggering of a control signal does not take place. A further advantageous way can be for example the zero setting of the control signal itself if the conditions for suppressing the disengagement process are present whereby the sensor signal remains in its original form and the shift intent detection remains during the suppression.

A further advantageous design is the choice of a variable time interval for the suppression of the shift intent signal wherein different influencing factors can determine the duration of the interval. Thus for example the length of the time interval suppressing the shift process when a shift intent detection exists, can be selected in dependence on the starting and/or target transmission ratio of the gearbox so that for example a longer time interval is predetermined for shift processes with a more powerful deceleration since here the operating element is subjected to longer lasting decelerations and therefore for example the operating element and the associated sensor experience higher deceleration forces and greater displacement paths. Also in the event of accelerations with different transmission ratios it is advantageous to set the time interval in dependence thereon. Also it can be advantageous to provide the suppression of the shift intent signal only for specific transmission ratios, such as for example for high transmission ratios in the gears at slow speed.

Furthermore the combination of a constant and variable predetermined time interval is advantageous insofar as a constant time interval can be provided to which is added an additional variable time interval which can be dependent on a further measured value, for example one permitting conclusions to be made on the vehicle movement.

This measuring system can be fitted in embodiments according to the invention with an acceleration sensor which can measure the accelerations in all vehicle directions. Also the detection and processing of measured signals relating to driving and relative speeds, for example by a tachometer or by the sensors detecting the wheel speed of driven or non-driven wheels. Also relative speeds-and/or engine speeds before and after the change of transmission ratio during a shift process can be advantageous as the measured value for choosing the length of the time interval.

Furthermore taking into account the throttle valve position and/or the speed of the throttle valve displacement can be a measure for the duration of the time interval to be preset for suppressing an existing (erroneous) shift intent.

The invention will now be explained in further detail with reference to the drawings in which:

Figure 1 shows a diagrammatic view of a vehicle; I Figure 2 shows a shift gate; and Figure 3 is a diagram.

Figure 1 shows a vehicle 1 in a diagrammatic view with a drive unit 2, a torque transfer system 3 and a gearbox 4. On the output side of the gearbox 4 is a drive shaft 5 and a differential G as well as the driven axles 7a and 7b wherein the wheels Ba, 8b are driven by means of the driven axles 7a and 7b. The vehicle can also be provided with a four wheel drive. This is however not shown in Figure 1.

The torque transfer system 3, such as for example the friction clutch, magnetic powder clutch or torque converter with converter lock-up clutch is shown in Figure 1 as a torque transfer system 3 mounted in the drive train between the engine 2 and gearbox 4 wherein the torque transfer system can also be mounted on the output side after the gearbox 4, as can be expedient for example in the case of continuously variable transmissions (CVT).

The torque transfer system 3 consists in the illustration of Figure 1 of a clutch disc with friction linings 3b, a pressure plate 3c as well as a clutch cover 3d and a plate spring 3e. These parts of the torque transfer system can be mounted on a flywheel 3a wherein these can also be installed together with the flywheel 3a as a pre-fitted unit. The flywheel can also be a so-called twin-mass flywheel which provides a torsion damper between the primary and secondary mass. The plate spring 3e is biased by means of the disengagement bearing 3f for engaging or disengaging the clutch whereby through the biasing of the plate spring tongues by means of the disengagement bearing 3f the clutch can be moved or set into a state which is for example the fully engaged or fully disengaged state or a state between these two boundary states. The torque transferable by the torque transfer system 3 can thereby be adjusted and fixed anywhere in the range between 5 neutral and the maximum value.

The disengagement bearing is operated in the embodiment of Figure 1 by means of a disengagement lever 9 wherein the disengagement lever is activated through a hydraulic stretch having a slave cylinder 10, hydraulic lead 11 and actor 12. The actor 12 contains a setting device 12a which in the event of using a hydraulic stretch contains a master cylinder and a drive unit for operating the master cylinder. Furthermore the actor 12 contains an electronic device 12b, such as control unit, which processes the incoming signals from for example sensor devices, sensors or other electronics units, and which produces control signals in order to govern the drive unit of the actor, for engaging or disengaging the torque transfer system.

The gearbox 4 is a gearbox where it is possible to differentiate between different transmission ratios, such as gears, by means of an operating element 13. To select one transmission ratio from a number of transmission ratios the operating element 13 is brought into the position provided for same or is activated in a manner and way proposed for same. This activation can take place manually or automated.

The device for disengaging the torque transfer system can take place as illustrated above by means of a pressure medium system wherein the pressure medium system can be a hydraulic system, pneumatic system or another fluidoperated system. The disengagement member can in these cases also be a central disengagement member operated by pressure medium. Furthermore the activation can also take place through mechanical means such as for example through a rod linkage.

A sensor device 14 can be attached or mounted on the operating element 13 whereby activation of the operating element is detected through this sensor unit 14. The detection of an activation can take place through measuring an acting force or through measuring a position change or a speed or acceleration change. Furthermore the activation can be detected on exceeding a boundary or threshold value in the event of movement or activation of the operating element.

The sensor or sensor device 14 can be a path- or speed- or accelerationor force-dependent sensor which detects or can detect a movement of the operating element or of an element connected thereto, or a force on the operating element or on an element connected thereto.

Furthermore a sensor 15 can be mounted on the gearbox 4 to detect the position of the engaged gear by detecting for example the position of shift elements inside the gearbox.

The sensors, such as throttle valve sensor 16, such as wheel speed or velocity sensor 17 (vehicle speed sensor), engine speed sensor 18 and further sensors can be provided in or on the vehicle and can be connected to the control unit through signal leads. A door sensor which detects whether a door is opened can likewise be mounted on the vehicle. Likewise a sensor for detecting the throttle valve angle is expedient. The control unit can also calculate from the data of the sensors gradients which are used to evaluate the shift intent. These gradients can be calculated for example through numerical methods. The - control unit 12 determines from these sensor data and other data as well as from system input values the driving state and generates a control signal for activating the torque transfer system 3 if a shift intent is evaluated as 5 being present.

If the operating element of the gearbox is activated by the driver, then the torque transfer system is disengaged by means of the control unit in that a control signal is generated for opening the torque transfer system. This generally takes place however only when the calculated or determined engine moment is less than or equal to a predeterminable torque value. Furthermore the shift intent is suppressed or evaluated as not given if through the evaluation of the designated measuring signals a shift intent is detected as erroneous. Then for a selected predetermined time interval the shift intent is suppressed or the control signal is suppressed.

The motor vehicle 1 has an accelerator pedal 20 such as a load lever, as well as an operating element of a brake 21, such as operating brake, as well as an operating element 22 for a brake such as parking brake.

A brake switch 24 can be mounted on the operating element of the operating brake 21 such as brake pedal, and detects whether the brake is activated. A brake switch of this kind can likewise be mounted on the operating element 22 for the parking brake wherein the sensor 25 detects whether the parking brake is activated.

A sensor 23 detects the position of the load lever 20 and can furthermore be in signal connection with the engine electronics 30 so that by operating the accelerator pedal the engine speeds and the engine moment are correspondingly controlled by the engine electronics 30. The engine moment applied can be determined from the signals entering the control unit 12, such as the measured data or system input values. Climate control or vibration accumulator can be mentioned by way of example as a secondary assembly. Furthermore drag moments can be taken into account.

It is furthermore possible to determine whether there is any activation of the operating element 13 and it can be determined whether a brake 21, 22 is activated, and whether the accelerator pedal, such as load lever is activated. The control unit 12 detects the shift intent through an activation of the operating element 13 from the incoming signals of the sensors 14 and/or 15. Whether the shift intent is evaluated or accepted by the control unit as a desire to shift, and a control signal is produced to open the clutch depends on, in addition to the system parameters, whether a suppression of the shift intent in a predetermined time interval is active or not.

According to the idea of the invention it is not expedient -in every situation that a shift intent signal is also evaluated so that a shift process is initiated. Thus in the event of severe changes in the acceleration of the vehicle, particularly after a gear change has just been carried out, for a defined time period of two seconds maximum the possibility of a shift process is to be suppressed for the said reasons.

Figure 2 shows a typical shift gate for a shift transmission for moving the shift lever. The operating element or the shift lever is moved along the shift gates 100 from neutral position N for shifting gears 1, 2, 3, 4, 5, R wherein it is possible to change between the shift gates 100 by means of the selector gates 101. To shif t from a higher gear, for example third gear 3 into second gear 2, the shift lever is guided for example from point 102 to point 103. This causes a deceleration of the vehicle so that if the driver leaves his hand on the shift lever the shift lever is moved in the drive direction by the deceleration process and the mass of the hand, which is interpreted by the shift intent sensor as an erroneous shift intent into first, third or fifth gear.

This erroneous shift intent detection is suppressed as described above through the inventive idea whereby the duration of the suppression is not to be longer than the shortest advisable stay in the corresponding gear just engaged.

Figure 3 shows in this respect an example of the signal behaviour of a sensor for shift intent detection. Illustrated is a signal 200 which a sensor supplies over the time to the control unit. The dashed line 201 indicates by way of example the position of the shift intent threshold for the forward gears - viewed in the driving direction - and the line 202 for reverse gears. If for example the sensor signal 200 drops beneath the shift intent threshold 201 then a control signal is issued by the control unit after an optional plausibility check to disengage the clutch. In the illustrated diagram, the shift intent is detected at time point t, the torque transfer system is disengaged whilst the shift lever is activated, as appears from the descent of the signal 200.

The torque transfer system engages again and decelerates the vehicle during changing down. As a result of this the shift lever is again accelerated in the other direction which leads to a new signal rise above the shift intent threshold 202 whereby a new shift intent is detected until the deceleration has finally subsided. The path of the sensor characteristic line in the illustrated embodiment is therefore corrected to the effect that between the time points t, and t, which define the time interval 205, the signal 200 is frozen at its minimum value and thus the sensor signal 206 is generated. The time interval 205 can be predetermined variable or fixed. In a further development of the signal 200 a further shift process is shown, for example into third gear, at time point t3 wherein it is not possible to detect any significant acceleration change which leads to an erroneous shift intent detection.

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 5 these refer to manufacturing, test and work processes.

Claims

1 Motor vehicle having a drive unit, a gearbox and an automated torque transfer system, such as for example a clutch, wherein the transmission ratio can be selected by means of an operating element, such as for example a shift lever, wherein at least one sensor detects the activation of the operating element and in the event of activation of the operating element a control signal can be produced by a control unit so that the torque transfer system is disengaged and is engaged again after a new transmission ratio has been selected, characterised in that in selected operating states of the motor vehicle the control signal for disengaging the torque transfer system can be suppressed for a predetermined time interval.

2. Motor vehicle according to claim 1 characterised in that the selected operating state is a driving situation with high acceleration or deceleration.

3. Motor vehicle more particularly according to claim 1 and/or 2 characterised in that the selected operating state is given immediately after engagement of the torque transfer system

4. Motor vehicle more particularly according to one of the preceding claims characterised in that the time interval is predetermined as constant.

5. Motor vehicle more particularly according to one of the preceding claims characterised in that the time interval is predetermined as variable.

6. Motor vehicle more particularly according to one of the preceding claims characterised in that the time interval is comprised of a combination of a fixed time interval and a variable time interval.

7. Motor vehicle more particularly according to one of the preceding claims, characterised in that the predetermined time interval is less than 2 seconds.

8. Motor vehicle more particularly according to one of the preceding claims characterised in that the predetermined time interval is in the range of 500 ms.

9. Motor vehicle more particularly according to one of the preceding claims characterised in that the time interval is predetermined in dependence on the selected transmission ratio.

10. Motor vehicle more particularly according to one of the preceding claims characterised in that the predetermined time interval is longer in the case of greater transmission ratios than in the case of smaller transmission ratios.

11. Motor vehicle more particularly according to one of the preceding claims characterised in that the predetermined time interval is only active in the case of certain, more particularly large, transmission ratios.

12. Motor vehicle more particularly according to one of the preceding claims characterised in that the time interval is predetermined in dependence on a measuring system which allows conclusions to be made about the vehicle movement.

13. Motor vehicle more particularly according to one of the preceding claims characterised in that the measuring system detects the acceleration, the deceleration, the driving speed and/or the relative speed before and after a change of transmission ratio.

14. Motor vehicle more particularly according one of the preceding claims characterised in that the time interval is predetermined in dependence on the throttle valve position and/or the speed of the throttle valve change.

15. Motor vehicle more particularly according to one of the preceding claims characterised in that the at least one sensor is a path length sensor.

16. Motor vehicle more particularly according to one of the preceding claims characterised in that at least one sensor is a force sensor.

17. Motor vehicle substantially as herein described with reference to the accompanying drawings.