Method and device for detecting a clutch-bite point
Disclosed is a method for detecting a clutch bite-point of a clutch that is connected to a driving motor. A rotational speed of the driving motor and the wheel rotational speed values of the wheels driven by the driving motor are determined. The invention further relates to a device for implementing the method. As the exact clutch bite-point is required as a release criterion for an automatic release operation of an electric parking brake in a motor vehicle, a transmission ratio (f) is determined, which is produced from a quotient of the wheel rotational speed values (vwheel) and the rotational speed (n) of the driving motor, and that the clutch bite-point is established when the transmission ratio (f) and the rotational speed (n) of the driving motor have a local minimum.
The present invention relates to a method for detecting a clutch bite-point of a clutch that is connected to a driving motor, wherein the rotational speed of the driving motor and the wheel rotational speed values of the wheels driven by the driving motor are determined. The invention further relates to a device for implementing the method.
The exact clutch bite-point is required, for example, as a release criterion for an automatic release operation of an electric parking brake in a motor vehicle. However, the problem is encountered that each clutch is subject to wear, which changes the position of the bite-point.
DE 10 2005 011 032 A1 discloses a method for detecting the point of time of engagement of a clutch that is connected to a driving motor, when a check is made as to whether a torque provided by a driving motor is within a predetermined range and when clutch engagement is detected as soon as a rate of change of the rotational speed falls below a predetermined first threshold value. In the prior art method, the torque provided by the driving motor is required as an input variable, the torque being different in individual internal combustion engines. The torque provided by the driving motor is not measured directly, but is calculated from the rate of injection, the rotational speed of the engine, air quantity, etc. Therefore, the torque is not always available in a sufficient quantity, as is the case after a cold start of the internal combustion engine, for example.
In view of the above, an object of the invention is to improve upon a method in such a way that the clutch bite-point is determined in a reliable manner with a higher rate of precision.
According to the method, this object is achieved in that a transmission ratio is determined, which is produced from a quotient of the wheel rotational speed values and the rotational speed of the driving motor, and in that the clutch bite-point is established when the transmission ratio and the rotational speed of the driving motor have a local minimum. The required rotational speed of the driving motor and the wheel rotational speed values are available with higher precision than the value for the torque of the driving motor, since they are sensed directly by sensors. The effort of application is considerably lower for different internal combustion engines, since the method of the invention does not require the torque that is different for each internal combustion engine.
It is arranged that a clutch pedal travel sensor senses the position of a clutch pedal and that the position of the clutch pedal at the clutch bite-point is saved.
In a particularly favorable improvement, the position of the accelerator pedal is sensed, and the detection of the clutch bite-point is performed exclusively when the accelerator pedal is not applied.
In this respect, the wheel rotational speed values are determined by means of wheel rotational speed sensors, and the accelerator pedal position is determined by means of an accelerator pedal travel sensor.
In a particularly favorable improvement of the method of the invention, the position of the clutch pedal, which corresponds to the clutch bite-point, is used as a criterion for the automatic release of an electric parking brake in a motor vehicle.
The object is achieved in addition in that a means is provided determining a transmission ratio, which is produced from a quotient of the wheel rotational speed values and the rotational speed of the driving motor, and detecting the clutch bite-point when the transmission ratio and the rotational speed of the driving motor have a local minimum.
There is provision of a clutch pedal travel sensor for determining the clutch pedal position, wheel rotational speed sensors for determining the wheel rotational speed values, and an accelerator pedal travel sensor for determining the accelerator pedal position.
The invention will be explained in detail in the following by way of an embodiment making reference to the accompanying drawings. In the drawings:
As has been mentioned already by way of introduction, the exact clutch bite-point is required as a release criterion for an automatic release operation of the electromechanically operable parking brake. After starting of the motor vehicle has been detected, the control unit 6 associated with the parking brake activates the adjusting unit 1 in the sense of a release operation of the parking brake. To detect a starting maneuver, it is initially checked, whether the ignition of the motor vehicle is activated. If this is the case, it is assumed that the motor vehicle shall be moved. For this purpose, an additional check is made, whether the driving motor is in the operating mode. It is found out by evaluation of the signals of the clutch pedal travel sensor 18, whether the operator has depressed the clutch pedal. If the operator releases the clutch pedal 14 from the above-mentioned depressed position, a starting maneuver of the motor vehicle is identified, and the control unit 6 mentioned with respect to
The method of the invention for detecting the clutch bite-point is explained in more detail in the following by way of
The time variation designated by reference numeral 21 represents the position of the clutch pedal 14. The clutch pedal position s can likewise adopt values between 0% and 100%, and the position Sbite of the clutch pedal 14 at the clutch bite-point is saved.
To detect the clutch bite-point, a transmission ratio f is determined, which is produced from a quotient of the wheel rotational speed values vwheel and the rotational speed of the driving motor and is designated by reference numeral 22 in
The operator applies the clutch pedal during gearshift, that means the operator moves the clutch pedal 14 from the non-applied position into an almost fully applied position, as is illustrated in the positions 25 and 26. When the clutch is engaged again after the gearshift in the downshifting maneuver, the torque transmitted by the clutch will speed up the driving motor. The rotational speed n of the driving motor and the transmission ratio f will rise, as becomes apparent from positions 27 to 30. The clutch pedal position Sbite, at which the rotational speed n and the transmission ratio f, respectively, begin to rise, is saved as the bite-point, that means when the transmission ratio f and the rotational speed n of the driving motor have a local minimum. The total ratio stabilizes itself after clutch engagement at a higher level than before the gearshift. The clutch bite-point is detected by way of rise of the rotational speed n of the driving motor during downshifting.
The values of rotational speed n of the driving motor and wheel rotational speed values vwheel required for the method of the invention are at disposal with a high rate of precision, since they are directly sensed by means of sensors. This allows detecting the clutch bite-point also in a precise fashion. The effort of application of the method at topic to different motor vehicle models is comparatively low.
The method of the invention does not have to be limited to the downshifting maneuver. When the operator disengages the clutch for a very long time in an upshifting maneuver, the driving motor will adjust itself at the level of an idling speed and accelerates when engaging the clutch without depression of the accelerator pedal 16. It is this way possible to extend the scope of application.
Claims
1-8. (canceled)
9. A method for detecting a clutch bite-point of a clutch that is connected to a driving motor, the method comprising:
- determining rotational speed (n) of a driving motor;
- determining wheel rotational speed values (vwheel) of wheels driven by the driving motor;
- determining a transmission ratio (f), wherein the transmission ratio is determined from a quotient of the wheel rotational speed values (vwheel) and the rotational speed (n) of the driving motor; and
- establishing a clutch bite-point the transmission ratio (f) and the rotational speed (n) of the driving motor have a local minimum.
10. The method of claim 9, wherein a clutch pedal travel sensor (18) senses the position of a clutch pedal (14), and in that the position of the clutch pedal (14) at the clutch bite-point is saved.
11. The method of claim 9, wherein a position of an accelerator pedal (16) is sensed, and the detection of the clutch bite-point is performed exclusively when the accelerator pedal (16) is not applied.
12. The method of claim 10, wherein the accelerator pedal position is determined by means of an accelerator pedal travel sensor.
13. The method of claim 9, wherein the wheel rotational speed values (vwheel) are determined by means of wheel rotational speed sensors (12, 13).
14. The method of claim 9, wherein the position of the clutch pedal (18), which corresponds to the clutch bite-point, is used as a criterion for the automatic release of an electric parking brake in a motor vehicle.
15. A device for detecting a clutch bite-point of a clutch that is connected to a driving motor, the device comprising:
- a device for determining rotational speed (n) of the driving motor and wheel rotational speed values (vwheel) of wheels driven by the driving motor;
- a device for determining a transmission ratio (f), which is produced from a quotient of the wheel rotational speed values (fwheel) and the rotational speed (n) of the driving motor, and detecting the clutch bite-point when the transmission ratio (f) and the rotational speed (n) of the driving motor have a local minimum.
16. The device of claim 15, further comprising a clutch pedal travel sensor (18) for determining the clutch pedal position, wheel rotational speed sensors (12, 13) for determining the wheel rotational speed values, and an accelerator pedal travel sensor for determining the accelerator pedal position.
Type: Application
Filed: Apr 26, 2006
Publication Date: May 21, 2009
Inventor: James Roberts Kulbe (Emeraude)
Application Number: 11/919,152
International Classification: B60W 10/02 (20060101);