METHOD AND DEVICE FOR DETERMINING THE TRAVEL OF A CLUTCH OR A GEAR ACTUATOR IN A HYDRAULIC CLUTCH ACTUATION SYSTEM OR A HYDRAULIC GEAR ACTUATION SYSTEM

Abstract

A method determines the travel of a clutch in a hydraulic clutch-actuation system. A hydraulic signal which extends between a transmitting end and a receiving end is acted upon by an acoustic signal for the generation of a wave packet. The acoustic signal on the transmitting end of the clutch-actuation system is fed into the hydraulic fluid, a wave packet generated by the acoustic signal on the receiving end is reflected back to the transmitting end, a running time of the transmitted and reflected wave packet on the transmitting end is evaluated to determine the coupling travel.

Claims

1. A method for determining the travel of a slave piston in a hydraulic actuation system, in which a hydraulic fluid extending between a transmitting end and a receiving end is acted upon by an acoustic signal for generating a wave packet such that the acoustic signal on the transmitting end of the actuation system is fed into the hydraulic fluid, a wave packet generated by the acoustic signal on the receiving end is reflected back to the transmitting end, and at the transmitting end a running time of the emitted and reflected wave packet for determining the coupling travel is evaluated.

2. (canceled)

3. The method according to claim 1, wherein a density of the hydraulic fluid is determined to correct the travel measurement.

4. The method according to claim 1, wherein standing waves are generated from a superimposition of the transmitted and the reflected wave packets to check the plausibility of the travel measurement, the travel of the coupling from a travel between the nodes of the standing wave or the gear actuator being closed.

5. The method according to claim 1, wherein the travel determination is carried out at predetermined time intervals or continuously.

6. A device for determining the travel of a slave piston in a hydraulic actuation system, comprising an acoustic transmitting unit for acting upon a hydraulic fluid which extends between a transmitting end and a receiving end of the actuation system having an acoustic signal which is received by an acoustic receiving unit arranged on the transmitting end, the hydraulic fluid for actuating the clutch being pressurized on the receiving end, wherein the acoustic transmitting unit generating the acoustic signal in the hydraulic fluid is arranged on the transmitting end and the acoustic receiving unit receives the signal reflected by the receiving end.

7. (canceled)

8. The device according to claim 6, wherein the acoustic transmitting unit and/or the acoustic receiving unit are positioned in a master cylinder.

9. The device according to claim 8, wherein the acoustic transmitting unit and/or the acoustic receiving unit are positioned in a master cylinder of a clutch actuator.

10. The device according to claim 6, wherein the acoustic transmitting unit and the acoustic receiving unit are arranged in a common module.

11. The device according to claim 6, wherein a pressure sensor and a temperature sensor for determining a density of the hydraulic fluid are arranged on the transmitting end.

12. The device according to claim 11, wherein the pressure sensor forms a structural unit with the acoustic transmitting unit and the acoustic receiving unit.

13. The method of claim 1 wherein the hydraulic actuation system is a clutch actuation system.

14. A hydraulic actuation system comprising: a master cylinder; a slave cylinder fluidly connected to the master cylinder; a slave piston axially movable within the slave cylinder; an acoustic transmitting unit configured to generate an acoustic signal in a fluid; an acoustic receiving unit configured to detect the acoustic signal after the signals has reflected off the slave piston; and a processing unit programmed to calculate an axial position of the slave piston with respect to the slave cylinder based on a time delay between generation of the acoustic signal and detection of the reflected acoustic signal.

15. The actuation system of claim 14 wherein the acoustic transmitting unit and the acoustic receiving unit are both located within the master cylinder.

16. The actuation system of claim 14 wherein the processing unit is further programmed to compensate for changes in a density of the fluid.

17. The actuation system of claim 14 further comprising a temperature sensor and a pressure sensor and wherein the processing unit is further programmed to calculate a density of the fluid based on readings from these sensors.

18. The actuation system of claim 14 wherein the slave cylinder is configured to apply or release a clutch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] An exemplary embodiment will be explained in more detail with reference to the figure shown in the drawing.

[0020] The following is shown:

[0021] Figure: an exemplary embodiment of the device.

DETAILED DESCRIPTION

[0022] The Figure shows an exemplary embodiment of a device as is used in the clutch-actuation system 1 in a motor vehicle. The clutch-actuation system 1 comprises a transmitting end 2 and a receiving end 3. The transmitting end 2 has a clutch actuator 4, which comprises a master cylinder 5. The master piston 6 arranged in the master cylinder 5 is driven by an electric motor 7, the rotational movement of the electric motor 7 being converted into a linear movement of the master piston 6 of the master cylinder 5 via a threaded spindle 8. The master cylinder 5 is connected via a hydraulic travel 10 filled with a hydraulic fluid 9 to a slave cylinder 11 on the receiving end 3, which has a slave piston 12 which, when the volume of the hydraulic fluid 9 is displaced by the master piston 6 in the hydraulic travel 10, actuates the clutch 14 via a release bearing 13.

[0023] An acoustic transmitting unit 16 and an acoustic receiving unit 17 are arranged in a pressure chamber 15 of the master cylinder 5. Both the acoustic transmitting unit 16 and the acoustic receiving unit 17 are connected to an evaluation unit 18 which controls the electric motor 7 or outputs output signals to other motor vehicle modules.

[0024] If the electric motor 7 receives a signal from the evaluation unit 18 to open or close the clutch 14, this electrical signal is converted into a movement of the master piston 6, which moves to the left and thereby displaces the volume of the hydraulic fluid 9. As a result of this displaced volume, the slave piston 12 is moved on the slave cylinder 11 and the clutch 14 is thereby adjusted.

[0025] To precisely measure the disengagement travel D covered by the clutch 14, the acoustic transmission unit 16, for example a sound sensor, sends an acoustic signal to the hydraulic fluid 9 continuously or at predetermined intervals, resulting in a wave packet which is generated by the hydraulic fluid 9 of the hydraulic fluid line 10 (pressure line) that is moved to the slave cylinder 11 and there is reflected on the slave piston 12. The reflected wave packet is transported back to the master cylinder 5 via the hydraulic travel 10, the reflected acoustic wave packet being detected by the acoustic receiving unit 17. The evaluation unit 18 determines the disengagement travel D, which was covered by the clutch 14, from the running time t of the transmitted and received reflected wave packet, where the following applies:

D=c*t/2,

wherein [0026] D Clutch Disengagement travel [0027] c Speed of Sound [0028] t Running Time. [0029] Since the speed of sound c depends on the density of the hydraulic fluid 9, the evaluation unit 18 uses a pressure sensor 19, which also projects into the pressure chamber 15 of the master cylinder 5, and a temperature sensor (not shown) to estimate the density. However, the density can also be determined using a suitable calculation model and its effect on the determination of the disengagement travel D can be compensated for.

[0030] Due to the necessary line connections of the sensors and the evaluation unit, unwanted reflections that falsify the acoustic signal can arise. In an initialization process, these unwanted reflections or their patterns can be determined before the actual running time determination and can be used to compensate for the reflected wave packet when determining the running time t.

[0031] Alternatively, a superimposition of the transmitted and reflected wave packets can be used to generate standing waves in the hydraulic fluid 9. The disengagement travel D of the clutch 14 is determined from the position of a first node of the standing wave and the position of a last node. By increasing the frequency, the first fundamental frequency and the subsequent harmonics can be used to perform a plausibility check on the measurement of the disengagement travel D of the clutch 14.

[0032] To optimally adjust a standing wave or the reflection, it can be necessary to optimize the hydraulic travel 10 forming the sound travel by introducing additional reflection or guide bodies.

[0033] The vibration excitation of the liquid column of the hydraulic fluid 9 by the acoustic transmitting unit 16 enables a transmission of micro vibrations to the moving parts 6, 11 of the clutch-actuation system. Frictions can thereby be reduced, which increases the controllability and regulation capability of the clutch 14. Depending on the operating strategy, the disengagement travel D can be determined continuously or only at certain times. For example, it can be possible that the reduction in friction is sometimes a hindrance to operation, which is the case when predetermined clutch-actuation systems are retained, which is why the travel determination should not be carried out in certain situations.

LIST OF REFERENCE NUMBERS

[0034] 1 clutch-actuation system [0035] 2 Transmitting End [0036] 3 Receiving End [0037] 4 Clutch Actuator [0038] 5 Master Cylinder [0039] 6 Master Piston [0040] 7 Electrical Motor [0041] 8 Threaded Spindle [0042] 9 Hydraulic Fluid [0043] 10 Hydraulic Track [0044] 11 Slave Cylinder [0045] 12 Slave Piston [0046] 13 Release Bearing [0047] 14 Clutch [0048] 15 Pressure Chamber [0049] 16 Acoustic Transmitting Unit [0050] 17 Acoustic Receiving Unit [0051] 18 Evaluation Unit [0052] 19 Pressure Sensor