Method and transmission control unit for operating a hydraulic valve of a motor vehicle

Abstract

Method for operating a hydraulic valve (11) of a motor vehicle, namely a hydraulic valve (11) of a transmission of the motor vehicle, which serves to control the pressure of a switching element (10) of the transmission, wherein the hydraulic valve (11) has a valve tappet (12) actuated by an actuator (15), wherein the position of the valve tappet (12) is influenced by an electrical current to the actuator (15), and depending on the position of the valve tappet (12), the hydraulic pressure applied to the switching element (10) and the torque that can be transmitted by the switching element (10) are influenced, wherein, in order to provide a target position of the valve tappet (12) and, depending on this, in order to provide a target torque that can be transmitted by the switching element (10), the actuator (15) is controlled with an electrical target current to which a dither signal is superimposed.and wherein at least one amplitude of the dither signal is determined depending on the target torque that can be transmitted by the switching element (10).

Description

[0001] The invention relates to a method for operating a hydraulic valve of a motor vehicle, namely a hydraulic valve of a motor vehicle's transmission, which serves to control the pressure of a shift element of the transmission. The invention further relates to a transmission control unit for carrying out the method.

[0002] It is known that a motor vehicle transmission has switching elements that can be opened and closed to perform a gear change. Such a switching element is, in particular, a friction-based switching element, such as a clutch or a brake.

[0003] It is also known to actuate a switching element of a transmission via a hydraulic control system using hydraulic pressure, in order to either close or open the respective switching element depending on the hydraulic pressure. A hydraulic valve serves for the hydraulic actuation of a switching element. A hydraulic valve has a valve stem actuated by an actuator. The actuator can be electrically energized, and the electrical energization of the actuator determines the position of the valve stem and, depending on the position of the valve stem, the hydraulic pressure with which the switching element is actuated. The hydraulic pressure acting on the switching element determines the torque that can be transmitted by the switching element.

[0004] DE 10 2016 211 956 A1 discloses a method for transmitting and damping a mean torque with a superimposed alternating torque.

[0005] There is a need for improved control of a hydraulic valve in a motor vehicle transmission, particularly to reduce breakaway friction and static friction at the hydraulic valve. The object of the present invention is to provide a novel method and control unit for operating a hydraulic valve in a motor vehicle.

[0006] This problem is solved by a method according to claim 1 and by a transmission control unit according to claim 8.

[0007] According to the invention, to provide a target position of the valve tappet and, depending on this, to provide a target torque that can be transmitted by the switching element, the actuator is controlled with an electrical target current to which a dither signal is superimposed, wherein at least one amplitude of the dither signal is determined depending on the target torque that can be transmitted by the switching element.

[0008] The present invention proposes controlling the actuator of a switching element with a target electrical current superimposed with a dither signal. The amplitude of the dither signal is dependent on the target torque that can be transmitted by the switching element. This allows for a particularly advantageous control of a hydraulic valve in a transmission, reducing static and breakaway friction at the valve stem.

[0009] Preferably, the frequency of the dither signal is also determined depending on the target torque that can be transmitted by the switching element. This allows the control of a hydraulic valve in a transmission to be further improved by reducing the static friction or breakaway friction at the valve tappet.

[0010] Preferred embodiments are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows: Fig. 1. A section of a motor vehicle transmission in the area of ​​an actuator, a hydraulic valve and a switching element in partial exploded view. Fig. 2 a block diagram to illustrate a first variant of the invention, Fig. 3 a block diagram to illustrate a second variant of the invention, Fig. 4 A block diagram to illustrate a third variant of the invention.

[0011] Fig. Figure 1 shows a section of a motor vehicle transmission in the area of ​​a switching element 10 designed as a clutch and a hydraulic valve 11, which serves to pressurize the switching element 10.

[0012] The hydraulic valve 11 has a valve tappet 12 arranged in a valve body 13. The valve tappet 12 is acted upon by a spring element 14 and also by an actuator 15. When the actuator 15 is not energized, the spring element 14 pushes the valve tappet 12 into a first position. By energizing the actuator 15, the valve tappet 12 can be moved out of this first position against the spring force of the spring element 14.

[0013] The electrical current applied to the actuator 15 thus determines the position of the valve tappet 12 and, depending on the position of the valve tappet 12, the application of hydraulic pressure to the clutch 10. Depending on the position of the valve tappet 12, hydraulic oil can either be directed towards the clutch 10 in the direction of the dashed arrows 16, or hydraulic oil can be discharged from the clutch 10 towards a collection reservoir in the direction of the solid arrows 17.

[0014] The hydraulic valve 11 of the Fig. The device 1 therefore has a valve tappet 12. The valve tappet 12 is acted upon by the spring element 14 on one side and by the actuator 15 on the other. By applying an electrical current to the actuator 15, the valve tappet 12 can be moved against the spring force of the spring element 14. The position of the valve tappet 12 influences the hydraulic pressure applied to the switching element 10, and the torque that can be transmitted by the switching element 10 depends on this pressure.

[0015] In order to transmit a defined target torque M at the coupling 10, the actuator 15 is energized with a defined electrical target current I in order to provide a defined target position for the valve tappet 12 depending on the target torque M to be transmitted.

[0016] To provide a target position for the valve tappet 12 and, depending on this, to provide a target torque M that can be transmitted by the switching element, the actuator 15 is controlled with a defined target electrical current I. The target current I can be determined based on the characteristic map or characteristic curve, depending on the target torque M.

[0017] A dither signal, characterized by a frequency FD and an amplitude AD, is superimposed on the electrical target current I.

[0018] At least the amplitude AD of the dither signal, and in particular also the frequency FD of the dither signal, is determined depending on the target torque M that can be transmitted by the switching element 10. This will be explained below with reference to Fig. 2 to 4 described.

[0019] In Fig. 2 and Fig. 3. The frequency FD of the dither signal is determined in a block 20, wherein the target current I for the electrical current supplying the actuator 15 and a temperature T are provided as input variables to the block 20. The temperature T can be the temperature of the switching element 10, the temperature of the gearbox, or the ambient temperature. In block 20, the frequency FD of the dither signal is determined according to a characteristic map, depending on the target current I for the electrical current supplying the actuator 15 and the temperature T. In this respect, the following are agreed. Fig. 2 and Fig. 3 match.

[0020] In the exemplary embodiment of the Fig. In block 21, a first frequency A1 is determined depending on the frequency FD of the dither signal, which was determined in block 20, and depending on the target electrical current I for the electrical energizing of the actuator 15, preferably again depending on the characteristic map. In block 22, a factor X is determined depending on the target torque M to be transmitted by the switching element 10, either based on the characteristic map or characteristic curve, using which the first amplitude A1 determined in block 21 is corrected. Preferably, the first amplitude A1 is multiplied by the correction factor X to determine the amplitude AD of the dither signal.

[0021] Fig. Figure 3 shows a modification in which, in a block 23, the amplitude AD of the dither signal is determined depending on the frequency FD of the dither signal determined in block 20 and depending on the target torque M of the switching element 10 to be transmitted or transmissible, preferably depending on the characteristic map.

[0022] Fig. 2 and Fig. 3 is common in that the frequency FD of the dither signal in a block 20 is preferably determined characteristically depending on a temperature T and a target current I for the electrical current supply of the actuator 15, where the temperature T is the temperature of the switching element 10 or the temperature of the gearbox or the outside temperature and the target current I is the target current for the electrical current supply of the actuator 15.

[0023] Furthermore, Fig. 2 and Fig. 3. They have in common that the amplitude AD of the dither signal is determined depending on the transmissible target torque M of the switching element 10, namely in Fig. 2 by a correction of the first frequency A1, which is preferably determined characteristic-map dependent on the frequency FD and the target current I in block 21. In Fig. In block 23, the amplitude AD of the dither signal is preferably determined according to the characteristic map, depending on the transmissible target torque M and the frequency FD.

[0024] Fig. Figure 4 shows a modification of the invention in which, in a block 24, the frequency FD of the dither signal is preferably determined based on a characteristic map, depending on the temperature T and the transmissible target torque M of the switching element 10. In a block 25, the amplitude AD of the dither signal is preferably determined based on a characteristic map, depending on the frequency FD determined in block 24 and again based on the transmissible target torque M.

[0025] The invention allows for a particularly advantageous control of a hydraulic valve 11 of a motor vehicle transmission, reducing breakaway torques by means of a dither signal, wherein at least the amplitude AD of the dither signal is determined depending on the target torque M that can be transmitted by the switching element 10. This allows breakaway torques, also known as the stick-slip effect, to be reduced particularly advantageously.

[0026] The invention further relates to a transmission control unit configured to automate the method described above. To provide a target position for the valve tappet 12 and a target pressure dependent thereon, and thus a target torque M to be transmitted by the switching element, the transmission control unit supplies the actuator 15 with a target electrical current I to which a dither signal is superimposed. The transmission control unit determines at least the amplitude AD and preferably also the frequency FD of the dither signal depending on the target torque M to be transmitted by the switching element 10.

[0027] The transmission control unit is an electronic transmission control unit that has hardware and software means for carrying out the method according to the invention. The hardware means include data interfaces for exchanging data with the assemblies involved in carrying out the method according to the invention, for example, with actuator 15. The hardware means also include memory for data storage and a processor for data processing. The memory contains, in particular, the characteristic maps mentioned above. The software means include program modules that are implemented in the control unit for carrying out the method according to the invention. These program modules are executed by the processor. Reference sign 10 switching element 11 Hydraulic valve 12 valve tappets 13 Valve bodies 14 spring element 15 Actuator 16 Hydraulic oil flow 17 Hydraulic oil 20 blocks Block 21 Block 22 Block 23 24 blocks 25 blocks QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2016 211 956 A1

[0004]

Claims

[1] Method for operating a hydraulic valve (11) of a motor vehicle, namely a hydraulic valve (11) of a transmission of the motor vehicle, which serves to control the pressure of a switching element (10) of the transmission, wherein the hydraulic valve (11) has a valve plunger (12) actuated by an actuator (15), wherein the position of the valve plunger (12) is influenced by an electrical current to the actuator (15) and, depending on the position of the valve plunger (12), the hydraulic pressure applied to the switching element (10) and the torque that can be transmitted by the switching element (10) are influenced. characterized by , that to provide a target position of the valve tappet (12) and, depending on this, to provide a target torque (M) that can be transmitted by the switching element (10), the actuator (15) is controlled with an electrical target current (I) to which a dither signal is superimposed, at least one amplitude (AD) of the dither signal is determined depending on the target torque (M) that can be transmitted by the switching element (10). [2] Method according to claim 1, characterized by , that a first amplitude (A1) is determined depending on a frequency (FD) of the dither signal and the electrical target current (I) of the actuator (15) according to the characteristic map, a correction factor (X) for the first amplitude (A1) is determined depending on the characteristic map and the target torque (M) that can be transmitted by the switching element (10), The amplitude (AD) of the dither signal is determined from the first amplitude (A1) and the correction factor (X). [3] Method according to claim 2, characterized by , that to determine the amplitude (AD) of the dither signal, the first amplitude (A1) and the correction factor (X) are multiplicatively calculated. [4] Method according to claim 1, characterized by, that the amplitude (AD) of the dither signal is determined depending on a frequency (FD) of the dither signal and the target torque (M) that can be transmitted by the switching element (10) according to the characteristic map. [5] Method according to any one of claims 2 to 4, characterized by , that the frequency (FD) of the dither signal is determined depending on the electrical target current (I) of the actuator (15) and a switching element temperature or transmission temperature or outside temperature (T) according to the characteristic map. [6] Method according to claim 1, characterized by , that the frequency (FD) of the dither signal is also determined depending on the target torque (M) that can be transmitted by the switching element (10). [7] Method according to claim 6, characterized by , that The frequency (FD) of the dither signal is determined according to the characteristic map depending on the target torque (M) that can be transmitted by the switching element (10) and a switching element temperature or transmission temperature or outside temperature (T). The amplitude (AD) of the dither signal is determined depending on the frequency (FD) of the dither signal and the target torque (M) that can be transmitted by the switching element (10) according to the characteristic map. [8] Transmission control unit which is configured to supply an actuator (15) of a hydraulic valve (11) of a transmission of a motor vehicle with an electric current, wherein the hydraulic valve (11) has a valve plunger (12) actuated by the actuator (15), wherein the position of the valve plunger (12) is influenced by the electrical current of the actuator (15) and, depending on the position of the valve plunger (12), the hydraulic pressure applied to the switching element (10) and the torque that can be transmitted by the switching element (10) supplied with hydraulic oil by the hydraulic valve (11) are influenced. characterized by , that the transmission control unit, in order to provide a target position of the valve tappet (12) and, depending on this, in order to provide a target torque (M) that can be transmitted by the switching element (10), controls the actuator (15) with an electrical target current (I) to which a dither signal is superimposed, the transmission control unit determines at least an amplitude (AD) of the dither signal depending on the target torque (M) that can be transmitted by the switching element (10). [9] Transmission control unit according to claim 8, characterized by , that the transmission control unit also determines the frequency (FD) of the dither signal depending on the target torque (M) that can be transmitted by the switching element (10). [10] Transmission control unit according to claim 8 or 9, characterized by , that the same is set up to execute the method according to one of claims 1 to 7 automatically on the control side.

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