METHOD FOR CONTROLLING A CLUTCH ACTUATOR

Abstract

A method controls a clutch actuator, comprising a clutch cylinder piston of a clutch cylinder, which clutch cylinder piston moves an actuation element of a friction clutch along an actuation path, and comprising a hydraulic pump, which actuates the clutch cylinder piston by means of a pressure medium pumped along a hydrostatic path and which is operated by means of an electric motor. In order to determine an actuation state of the friction clutch, the operating state along the actuation path is estimated by means of a pressure medium volumetric flow rate produced by the pump and by means of a leakage volumetric flow rate of the pump.

Claims

1. A method for controlling a clutch actuator having a clutch cylinder piston of a clutch cylinder, which clutch cylinder piston actuation element moves an actuation element of a friction clutch along an actuation path, and having a hydraulic pump, which actuates the clutch cylinder piston by a pressure medium pumped along a hydrostatic path and which is operated by an electric motor, wherein an operating state of the friction clutch along the actuation path is estimated using pressure medium volumetric flow rate produced by the pump and a leakage volumetric flow rate of the pump.

2. The method according to claim 1, wherein the pressure medium volumetric flow rate is determined using an angle of rotation of the electric motor and a constant geometric pump factor.

3. The method according to claim 1, wherein a leakage rate forming the leakage volumetric flow rate over time is determined as a function of a pump pressure applied in the hydrostatic path.

4. The method according to claim 3, wherein the pump pressure is determined by a pressure sensor.

5. The method according to claim 3, wherein the leakage rate is continuously adapted.

6. The method according to claim 5, wherein an adaptation of the leakage rate is provided as a function of an actually detected pump pressure and an estimated pump pressure.

7. The method according to claim 6, wherein a pressure deviation of the detected pump pressure from the estimated pump pressure is determined as a function of a clutch characteristic curve of the actuating force over an estimated actuation path.

8. The method according to claim 1, wherein the pressure medium volumetric flow rate is continuously adapted.

9. The method according to claim 1, wherein the pressure medium volumetric flow rate and the leakage volumetric flow rate area adapted in a common model structure.

10. A clutch actuator having a clutch cylinder and an electrically driven pump, acting on it via a hydrostatic path, and having a control device controlling the clutch actuator with software implementing the method of claim 1 and stored in the control device.

11. The method according to claim 2, wherein the pressure medium volumetric flow rate is continuously adapted.

12. The method according to claim 11, wherein a leakage rate forming the leakage volumetric flow rate over time is determined as a function of a pump pressure applied in the hydrostatic path.

13. The method according to claim 12, wherein the pump pressure is determined by a pressure sensor.

14. The method according to claim 12, wherein the leakage rate is continuously adapted.

15. The method according to claim 14, wherein an adaptation of the leakage rate is provided as a function of an actually detected pump pressure and an estimated pump pressure.

16. The method according to claim 15, wherein a pressure deviation of the detected pump pressure from the estimated pump pressure is determined as a function of a clutch characteristic curve of the actuating force over an estimated actuation path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention is explained in more detail with reference to the exemplary embodiment in the single FIGURE. It shows a schematic diagram of a method for controlling a clutch actuator for estimating an operating state of the friction clutch.

DETAILED DESCRIPTION

[0025] The FIGURE schematically shows the estimation of the actuation path s of a clutch cylinder piston of a clutch actuator, wherein the clutch cylinder piston is actuated by means of a pump operated by an electric motor and supplying pressure medium via a hydrostatic path. On the basis of the input variables of the rotational speed n of the pump, determined, for example, from a rotation angle detection of the rotor of the electric motor driving the pump, and the current measured pump pressure p(m) in the hydrostatic section, the actuation path s is determined and adapted using the model structure 3.

[0026] For this purpose, the rotational speed n and the essentially constant pump factor f(p), which reproduces the geometric relationships of the pump, are multiplied in block 2 to determine the pressure medium volumetric flow rate i(d), which generates the pressure medium volume for actuating a clutch cylinder, and an actuation path resulting therefrom.

[0027] To take the leakage of the pump into account, the leakage volumetric flow rate i(e) producing the leakage volume is determined. It is determined from the currently measured pump pressure p(m) and the adapted leakage rate i(l)/dt, determined in the model structure 3, which are combined multiplicatively in block 5.

[0028] An adapted correction factor f(d) for the pressure medium volumetric flow rate i(d) is also determined from the model structure 3. In block 4, the pressure medium volumetric flow rate i(d), the leakage rate i(e), and the pressure medium correction factor f(d) are respectively combined for a predetermined time interval, for example one or more interrupts. The total volumetric flow rate i(g) is integrated in the integrator 6 over a predetermined time of predetermined interrupts and optionally filtered and averaged. In the calculation term 7, the total volume V(g), obtained in the integrator 6 from the leakage volume and the pressure medium volume, is converted into the actuation path s of the clutch cylinder piston or the actuation element of the friction clutch, using the geometric properties of the clutch cylinder.

[0029] The model structure 3 uses the currently set actuation path s and, in block 8, converts it into an estimated pump pressure p(s), which is delayed by an interrupt in block 9, on the basis of a model which is designed to match the real clutch actuator. In block 9, the delayed estimated pump pressure p(s,del) is subtracted from the currently measured pump pressure p(m) and a pump pressure error p(err) is determined. Based on this pump pressure error p(err), the leakage correction factor f(e) and the pressure medium correction factor f(d) are determined in the calculation terms 10, 11. The leakage correction factor f(e) is then used to calculate the adapted leakage rate i(l)/dt in block 12 and converted into the leakage volumetric flow rate i(e), using the measured pump pressure p(m). In addition to the pressure medium volumetric flow rate i(d) and the leakage volumetric flow rate i(e), the pressure medium correction factor f(d), which is continuously corrected during one or more interrupts, is supplied to block 4 so that both the pressure medium volumetric flow rate i(d) and the leakage volumetric flow rate i(e) as well as their volumes are continuously adapted using the model structure 3.

LIST OF REFERENCE SYMBOLS

[0030] 1 Schematic diagram [0031] 2 Block [0032] 3 Model structure [0033] 4 Block [0034] 5 Block [0035] 6 Integrator [0036] 7 Calculation term [0037] 8 Block [0038] 9 Block [0039] 10 Calculation term [0040] 11 Calculation term [0041] 12 Block [0042] f(d) Pressure medium correction factor [0043] f(e) Leakage correction factor [0044] f(p) Pump factor [0045] i(d) Pressure medium volumetric flow rate [0046] i(g) Total volumetric flow rate [0047] i(e) Leakage volumetric flow rate [0048] i(l)/dt Leakage rate [0049] n Rotational speed [0050] p(err) Pump pressure error [0051] p(m) Pump pressure [0052] p(s) Pump pressure [0053] p(s,del) Pump pressure, delayed [0054] s Actuation path [0055] V(g) Total volume