ELECTROHYDRAULIC TRANSMISSION CLUTCH OF A MOTOR VEHICLE

Abstract

A method for operating an electrohydraulic transmission clutch of a motor vehicle, wherein, for a clutch operation, a hydraulic pressure is set by way of a regulating device of a controller as a function of a clutch signal, and, through the pressure, a disengagement element of the transmission clutch is moved through a soft region into a rigid region via a rigid point, or vice versa. The soft region is to be compensated for. Further, as a function of the clutch signal, the regulating device generates a preliminary target value signal for the pressure and a time derivative of the preliminary target value signal is generated as a movement signal, and a pilot control generates a pilot control signal as a function of the movement signal, and the preliminary target value signal and the pilot control signal are combined to give a final actuating value signal for the pressure.

Claims

1-8. (canceled)

9. A method for operating an electrohydraulic transmission clutch of a motor vehicle, comprising: for a clutch operation, a hydraulic pressure is set by way of a regulating device of a controller as a function of a clutch signal and, through the pressure, a disengagement element of the transmission clutch is moved through a soft region into a rigid region via a rigid point, or vice versa, wherein, as a function of the clutch signal, the regulating device generates a preliminary target value signal for the pressure, and a time derivative of the preliminary target value signal is generated as a movement signal, and a pilot control generates a pilot control signal as a function of the movement signal, and the preliminary target value signal and the pilot control signal are combined to give a final actuating value signal for the pressure.

10. The method according to claim 9, wherein, by way of the pilot control, the movement signal is scaled with a pilot control factor and the pilot control factor is set as a function of at least one operating variable of the motor vehicle.

11. The method according to claim 10, wherein, as the at least one operating variable, at least one temperature is recorded.

12. The method according to claim 10, wherein the pilot control factor is determined as a function of the at least one operating variable by means of an assignment device, and the assignment device is adapted in the operation of the motor vehicle, as a function of a time constant with which a time signal of the pressure follows the preliminary target value signal or the final actuating value signal.

13. The method according to claim 10, wherein the pilot control factor is set as a function of a difference between the actual pressure and a pressure that is obtained in the rigid point.

14. The method according to claim 9, wherein the pilot control is active only in the soft region.

15. A controller for an electrohydraulic transmission clutch of a motor vehicle, comprising: an actuating output for adjusting an electric actuator for setting a hydraulic pressure for moving a disengagement element of the transmission clutch, wherein the controller is equipped for the purpose of carrying out the method according to claim 9.

16. A motor vehicle with an electrohydraulic transmission clutch, wherein a controller according to claim 15 is coupled to an electric actuator for setting a hydraulic pressure for moving a disengagement element of the transmission clutch.

Description

[0028] In the following, an exemplary embodiment of the invention is described. Shown are:

[0029] FIG. 1 a schematic illustration of a motor vehicle, in which an electrohydraulic transmission clutch with a controller is provided;

[0030] FIG. 2 a diagram with time courses of pressure signals;

[0031] FIG. 3 a diagram with time courses of pressure signals in the rigid region during a periodic movement of a clutch pedal;

[0032] FIG. 4 a diagram with time courses of pressure signals in the soft region during the periodic movement of the clutch signal;

[0033] FIG. 5 a schematic illustration of one embodiment of the controller according to the invention,

[0034] FIG. 6 the controller of FIG. 5 in a specific configuration;

[0035] FIG. 7 a schematic illustration of a time course of a pressure signal;

[0036] FIG. 8 a schematic illustration of a characteristic curve for a pilot control factor;

[0037] FIG. 9 a diagram with time courses of pressure signals and of a pilot control signal;

[0038] FIG. 10 a diagram with time courses of pressure signals and the pilot control signal for a periodic movement of a clutch pedal.

[0039] In the exemplary embodiment explained in the following, what is involved is a preferred embodiment of the invention. In the exemplary embodiment, the described components of the embodiment each represent individual features of the invention that are to be regarded independently of one another and that each further develop the invention independently of one another and hence are also to be regarded, individually or in a combination different from that shown, as a component of the invention. Furthermore, the described embodiment can also be augmented by additional features of the already described features of the invention.

[0040] In the figures, functionally identical elements are furnished with the same reference numbers.

[0041] In the following, it is assumed then that FIG. 1 represents an embodiment of the motor vehicle 1 according to the invention. For the explanation of the elements illustrated in FIG. 1, therefore, reference is made to the introduction of the description. A difference from the introductory description is that the motor vehicle 1 according to the invention has one embodiment of the controller 7 according to the invention.

[0042] For this purpose, FIG. 5 shows the controller 7, as it is connected at the control loop that is formed from the actuator 10 and the hydraulic drive 11. The controller 7 can receive an actual value Pist [Pactual] of the pressure P for a control. The control can be effected in the known way by a regulating device 22. By means of the regulating device 22, a simple control can occurfor example, by simple scaling of the clutch signal 6. The controller 7 additionally has a pilot control 23. A preliminary target value signal Psoll of the regulating device 22 is combined with a pilot control signal V by a summing unit 24 to give a final actuating value signal Psoll*. The final actuating value signal Psoll* is then provided as a control signal 9 at the signal output 8. It is possible in this way, for example, to provide an impedance matching. In the described way, the preliminary target value signal Psoll can be generated as a function of the clutch signal 6, which continuously describes the pedal position of the clutch pedal 3 during the movement 4.

[0043] The pilot control 23 generates a derivative signal 26 from the preliminary target value signal Psoll by means of a derivative 25. Accordingly, the derivative signal 26 then always has a value different from 0 when the position of the clutch pedal 3 changes. The derivative signal 26 is multiplied by a pilot control factor F by means of a multiplier 27, with the resulting product giving the pilot control signal V. The pilot control factor F is set as a function of at least one operating variable of the motor vehicle 1. In the example, an operating variable is a temperature Temp that can be recorded at a measurement input 28 by a temperature sensor 28, for example. The temperature Temp describes, in particular, the temperature of a hydraulic oil.

[0044] The pilot control factor F can be formed on the basis of a characteristic field 29, from which, as a function of the temperature Temp, a characteristic curve can be chosen. Another operating variable can be, for example, the actual pressure value Pist, which indicates how far away the actual pressure Pist is from the rigid point 21. For this purpose, a difference P can be calculated as the difference between the rigid point 21 and the actual pressure Pist.

[0045] FIG. 6 shows how the derivative 25 in one configuration of the controller 7 can be realized on the basis of a filter, with it being possible to determine a suitable value for the time constant Tv by simple trials.

[0046] FIG. 7 illustrates how, when the pilot control 23 (indicated as V=0) is switched off, the actual pressure value Pist in the soft region 17 responds to a jump or a rectangular course of the target value signal Psoll. On the basis of the course of the actual pressure Pist, it can be seen that subsystems are important for the pressure buildup in the soft region 17. Said subsystems are the clutch with the movement of the clutch cylinder (PT2 element, time constant approximately 2 milliseconds), the valve movement with its translational movement for setting the pressure (PT2 element, time constant approximately 8 to 13 milliseconds), and the pressure buildup behavior of the transmission clutch with the volume flow pressure amplification (PT1 element with time constant in the range of 220 milliseconds to 280 milliseconds). The volume flow describes the quantity of hydraulic fluid that is needed for a change in the pressure P.

[0047] On the basis of the time constants of the different subsystems, it can be seen that, in comparison, the pressure buildup is especially slow or dominant. For this purpose, the physical interpretation is that, for attaining a delta pressure in the soft region 17, a markedly higher volume flow is needed than in the rigid region 18. In the soft region 17, therefore, a volume flow pressure amplification is less than in the rigid region 18. Accordingly, it is possible, through compensation of said dynamics, to optimize the pressure response behavior. There is a reduction in the dominant dynamics of the pressure buildup; that is, the PT1 element (first-order time element) with its exponential behavior 30 is to be reduced by the tracking error 20. On the basis of the time course of the exponential rise 30, it can be determined that, for the specific transmission clutch 2, a time constant of T=280 milliseconds applies for the PT1 behavior. On the basis of the time constant T, the pilot control factor F can be determined. Thus, by way of this simple measure, it is possible, for different transmission clutches to generate a suitable characteristic field 29 in each case in order to be able to compensate for the respective tracking error 20.

[0048] FIG. 8 illustrates how, in an advantageous way, not only the nonlinearity of the PT1 behavior can be combined, but it is also possible to retract the compensation when the rigid point is approached. When the pressure P declines, the pressure difference P declines and the pilot control factor F is hereby gradually reduced to 0 for a threshold value S of the pilot control factor F. The threshold value S can lie in a range from 0 bar to 0.2 bar, for example at 0.1 bar.

[0049] FIG. 9 illustrates how, with the described configuration, a time course of the actual pressure Pist that is similar in the soft region 17 and the rigid region 18 can be obtained. For this purpose, it is further illustrated how the time course of the final actuating value signal Psoll* progresses in distinction to the target value signal Psoll. It can be seen that the final actuating value signal Psoll* causes a greater volume flow of the hydraulic fluid in the hydraulic drive 11. As a further reference, the original course 31 of the actual pressure Pist is illustrated, as has already been explained in connection with FIG. 2.

[0050] Overall, during an entire disengagement operation 32 going from an engaged state 33 via the gripping point 16 through the soft region 17 via the rigid point 21 into the rigid region 18 up to the engaged state 34, a constant behavior of the transmission clutch 2 thus ensues for the user of the motor vehicle.

[0051] FIG. 10 illustrates, once again in comparison to FIG. 4, the behavior of the transmission clutch 2 in the case of periodic actuation. Illustrated is the final actuating value signal Psoll* and the resulting actual pressure signal Pist, which now, similarly to the case in the rigid region 18, also follows the preliminary target value signal Psoll in the soft region 17 with a smaller tracking error 20. Through the targeted pilot control of the dominant dynamics, it is then possible, in the soft region 17, to ensure a markedly greater pressure response behavior, so that a bandwidth increase for periodic movements of 1 Hertz up to 10 Hertz, for example, can be achieved. What thus results is an increased robustness in the shifting quality over the scatter width of the soft regions 17 of different transmission clutches. The typical resulting pressure antinode 35 during applications, such as, for example, approach ramps, startups, or intersections, is avoided.

[0052] Overall, the example shows how, by means of the invention, an adaptive pilot control can be provided for compensation of a soft region of a clutch.