Method for operating a frictionally engaging shift element and control device

Abstract

A method for operating a frictionally engaged shift element of a motor vehicle, the shift element being connected between a drive assembly (2) of the motor vehicle and a driven device (4) of the motor vehicle, wherein it is monitored whether an undesired slip is formed at the frictionally engaged shift element (5), wherein, when it is determined that an undesired slip is formed at the frictionally engaged shift element (5), the torque provided by the drive assembly (2) is reduced in order to reduce the slip at the frictionally engaged shift element (5), namely in such a way that the torque provided by the drive assembly (2) is reduced in steps to a value which is related to the maximum transmittable torque of the frictionally engaged shift element (5).

Description

Technical Field

[0001] This invention relates to a method for operating a friction-fitting shifting element. Furthermore, this invention relates to a control device for operating a friction-fitting shifting element. Background Technology

[0002] Motor vehicles have a drive unit and a transmission, wherein the transmission connects the drive unit and the driven device. The transmission changes speed and torque and prepares to provide traction force from the drive unit at the driven device. The transmission has multiple shift elements. In each force-fit gear of the transmission, a first number of shift elements are closed and a second number of shift elements are disengaged. To perform a gear change, previously closed shift elements must be disengaged and previously disengaged shift elements must be closed. The shift elements of the transmission can be friction-fitting shift elements, such as clutches and brakes, and form-fitting shift elements, such as claws. Additional friction-fitting shift elements, referred to as starting clutches or disengaging clutches, can be connected between the drive unit and the transmission. Starting clutches or disengaging clutches can also be provided by friction-fitting shift elements within the transmission. This invention relates here to the operation of friction-fitting shift elements in motor vehicles.

[0003] When the drive unit of a motor vehicle provides a driving torque greater than that transmitted by a friction-fitted shift element, slippage occurs in the friction-fitted shift element. As known from DE 198 06 497 A1, it is monitored whether slippage has occurred at the friction-fitted shift element. When slippage is detected, the torque provided by the drive unit is reduced to decrease the slippage at the friction-fitted shift element. This reduction of the torque provided by the drive unit is achieved through slip adjustment, more precisely, continuously and preferably along a slope. This requires a relatively long period of time to reduce the slippage at the friction-fitted shift element.

[0004] A method for operating a friction-fitting shift element is known from DE 10 200 7 027 702 A1, wherein a learning process is used to determine the clutch disengagement point (Kupplungswegpunkte). Parameters are derived for different clutch disengagement points and the resulting positions of the friction-fitting shift element. The disengagement point or position of the friction-fitting shift element for which these parameters are derived also includes the contact point, creep point, and slip point.

[0005] It is known from DE 10 201 5 218 884 A1 that the clamping force of the friction-fitted shifting element is obtained at its different positions.

[0006] Another method for operating a friction-fitting shifting element is known from DE 10 201 5 218 994 A1. The torque transmitted by the friction-fitting shifting element can be determined based on its position. Summary of the Invention

[0007] There is a need to reduce unwanted slippage more quickly at friction-fitting shift elements. The object of this invention is to provide a novel method and control device for operating friction-fitting shift elements. This object is achieved by a method for operating friction-fitting shift elements. According to the invention, when unwanted slippage is determined to occur at the friction-fitting shift element, the torque provided by the drive unit is reduced in a stepwise manner to a value related to the maximum transmittable torque of the friction-fitting shift element. Therefore, it is proposed that when unwanted slippage is identified at the friction-fitting shift element to be operated, the torque provided by the drive unit is reduced in a stepwise manner, more precisely, reduced to a value related to the maximum transmittable torque of the friction-fitting shift element. This allows slippage at the friction-fitting shift element to be reduced in the shortest possible time.

[0008] Preferably, the value to which the torque provided by the drive unit is reduced in a stepwise manner corresponds to the maximum transmittable torque of the friction-fitted shift element minus or plus the offset. It is preferable to offset the maximum transmittable torque of the friction-fitted shift element with the offset to arrive at a value to which the torque provided by the drive unit is reduced in a stepwise manner, thereby reducing undesirable slippage. The sign and value of the offset can be used to achieve the desired driving behavior.

[0009] According to an advantageous improvement of the invention, the maximum transmittable torque of the friction-fitting shift element is obtained as follows: The clamping force of the friction-fitting shift element is determined for at least one position of the friction-fitting shift element. The torque transmitted by the friction-fitting shift element is determined for at least one position of the friction-fitting shift element. The quotient of the clamping force of the friction-fitting shift element and the torque transmitted by the friction-fitting shift element is calculated for at least one position where the clamping force and the transmitted torque are present. The maximum transmittable torque of the friction-fitting shift element is calculated from the calculated quotient and the clamping force at the engagement point (Zupunkt) of the friction-fitting shift element. In this manner, the maximum transmittable torque of the friction-fitting shift element can be advantageously obtained.

[0010] According to another advantageous improvement of the invention, when an undesirable slippage is determined to occur at the friction-fitted shift element, the following additional step is performed: calculating the difference between the current torque provided by the drive unit that determines the slippage and the torque currently transmitted by the friction-fitted shift element, the currently transmitted torque being derived from the separation force characteristic curve of the friction-fitted shift element based on the current position of the friction-fitted shift element or based on the current operation of the friction-fitted shift element. When the difference is greater than a limit value, adaptation of the separation force characteristic curve of the friction-fitted shift element is triggered. The improvement is based on the understanding that when the difference between the current torque provided by the drive unit that determines the undesirable slippage and the torque currently transmittable by the friction-fitted shift element is too large, the separation force characteristic curve of the friction-fitted shift element should be adapted or adjusted so that the friction-fitted shift element can be operated with higher precision.

[0011] A control device for operating a friction-fitting shifting element according to the present invention is also provided. Attached Figure Description

[0012] Embodiments of the invention are illustrated in detail with the aid of the accompanying drawings, but are not limited thereto. In the drawings:

[0013] Figure 1 A simplified diagram of the drive system of a motor vehicle is shown;

[0014] Figure 2 A timeline is shown illustrating a method for operating a friction-fitting shifting element according to the present invention;

[0015] Figure 3 A signal flow diagram is shown to further illustrate an improved method for operating a friction-fitting shifting element according to the present invention. Detailed Implementation

[0016] Figure 1 The drive system 1 of a motor vehicle is shown schematically. The drive system 1 has a drive unit 2, a transmission 3, and a driven device 4. The transmission 3 converts speed and torque and provides traction force to the drive unit 2 via the driven device 3.

[0017] The transmission 3 includes multiple shift elements 5, among which, Figure 1 Such a shift element 5 is illustrated exemplarily. The transmission 3 has a plurality of friction-engaged shift elements 5, which may be clutches or brakes. In each force-engaged gear of the transmission 3, a first number of shift elements 5 are closed and a second number of shift elements are disengaged.

[0018] Figure 1The shift element 5 shown is a shift element inside the transmission. It is also possible that another friction-fitting shift element is connected between the drive unit 2 and the transmission 3, and this shift element is thus designed as a disengagement clutch or a starting clutch.

[0019] The operation of the drive unit 2 is controlled and / or regulated by the engine control unit 6. For this purpose, the engine control unit 6 exchanges data with the drive unit 2 in the sense of the double arrows shown. The operation of the transmission 3 is controlled and / or regulated by the transmission control unit 7. For this purpose, the transmission control unit 7 exchanges data with the transmission 3 in the sense of the double arrows shown. Furthermore, the engine control unit 6 and the transmission control unit 7 exchange data with each other.

[0020] In order to operate the friction-fitting shift element 5, it is necessary to monitor whether undesirable slippage occurs at the friction-fitting shift element 5. In the clutch, this is done by calculating the difference between the rotational speed of the driving-side clutch half and the rotational speed of the driven-side clutch half.

[0021] exist Figure 2 In the diagram, two speed curves 8 and 9 are shown for the clutch to be operated at time t. Speed ​​curve 8 represents the speed of the clutch half on the driving side of the clutch to be operated, and speed curve 9 represents the speed of the clutch half on the driven side of the clutch to be operated. At time point t1, it is determined that an undesirable slip occurs at the shifting element 5 of the friction engagement to be operated (i.e., at the clutch). Therefore, the difference between speeds 8 and 9 exceeds the defined limit value.

[0022] In order to reduce unwanted slippage at the friction-fitting shift element 5 to be operated in the shortest possible time, when it is determined that unwanted slippage is formed at the friction-fitting shift element 5, the torque provided by the drive unit 2 is reduced stepwise to a predetermined value, more precisely, to a value related to the maximum torque that can be transmitted by the friction-fitting shift element 5.

[0023] therefore, Figure 2 The curve of torque 10 provided by drive unit 2 is also shown with respect to time t. The time point t1 at which undesirable slippage is identified at the friction-fitting shift element 5 to be operated causes the torque 10 provided by drive unit 2 to be reduced stepwise, or more precisely, reduced to a value related to the maximum torque that can be transmitted by the friction-fitting shift element 5.

[0024] This stepwise reduction in torque 10 provided by drive unit 2 can provide pre-control or pre-control component for reducing slip at shift element 5 in frictional engagement. Regular slip reduction adjustment can then be performed after this pre-control. In regular slip reduction adjustment, the torque of drive unit 2 is further adapted to reduce slip.

[0025] In a first implementation of the invention, it can be proposed that the torque provided by the drive unit 2 decreases stepwise to a value corresponding to the maximum transmittable torque of the friction-fitted shifting element 5.

[0026] In a second implementation of the invention, the torque provided by the drive unit 2 is reduced in a stepwise manner to a value corresponding to the maximum transmittable torque of the friction-fitted shifting element 5 minus or plus an offset, wherein this offset is freely applicable. This allows for the application of desired driving behavior.

[0027] As has been implemented, when an undesirable slippage is determined at the friction-fitted shift element 5, the torque provided by the drive unit 2 is reduced in a stepwise manner to a value related to the maximum torque that can be transmitted by the friction-fitted shift element 5.

[0028] The maximum transmittable torque can preferably be obtained as follows:

[0029] The clamping force of the friction-fitting shift element is determined for at least one location of the shift element, preferably for multiple locations of the friction-fitting shift element 5. The clamping force can be obtained by means of methods known from DE 10 201 5 218 884 A1.

[0030] The torque that can be transmitted by the friction-fitted shift element is determined for at least one position of the shift element, preferably for a subset of multiple positions of the shift element. The torque transmitted by the friction-fitted shift element can be derived here as is known from DE 10201 5 218 994 A1.

[0031] Next, for at least one location where the shift element 5 has a clamping force and transmits torque, the quotient of the clamping force of the friction-fitted shift element and the torque transmitted by the friction-fitted shift element 5 is calculated. If the quotient can be obtained for multiple locations, an average of the multiple quotients can be achieved.

[0032] Subsequently, the maximum torque that can be transmitted by the friction-fitted shift element is calculated. This is achieved by multiplying the calculated quotient or the calculated average of multiple quotients by the previously obtained clamping force at the engagement point of the shift element.

[0033] The above method allows for a simple and reliable determination of the maximum transmittable torque of a friction-fitted shifting element, which can then be used to reduce unwanted slippage.

[0034] In an advantageous improvement of the invention, it is proposed that when undesirable slippage is determined to occur at the shifting element 5 of the friction-fitted system to be operated, additional method steps are performed. This is referred to hereinafter. Figure 3 To describe.

[0035] exist Figure 3 In box 11, it is monitored whether undesirable slippage has formed at the shifting element of the friction fit to be operated. If this is not the case, the branch returns to box 11. Conversely, if undesirable slippage is determined to exist at the shifting element of the friction fit to be operated in box 11, the branch from box 11 goes to box 12.

[0036] In box 12, the difference between the current torque provided by drive unit 2, indicating the presence of undesirable slippage, and the torque currently transmittable by the friction-fitted shift element 5 is calculated. The torque currently transmittable by the friction-fitted shift element 5 is related to the current position or location of the friction-fitted shift element 5 or the current operation of the friction-fitted shift element 5, and can be derived from the separation force characteristic curve of the friction-fitted shift element 5 based on the position or operation.

[0037] In box 12, check if the difference is greater than the limit. If not, branch back to box 11 from box 12. Conversely, if in box 12, it is determined that the difference between the current torque provided by drive unit 2 that causes undesirable slippage and the torque currently transmittable by friction-fitted shift element 5 is greater than the limit, then branch from box 12 to box 13.

[0038] In block 13, the adaptation of the separation force characteristic curve of the corresponding friction-fitting shift element 5 of the transmission 3 is performed, wherein the adaptation is either triggered directly or triggered at a later time point at a staggered time. The original adaptation of the separation force characteristic curve is not the subject of this invention and is well known to those skilled in the art.

[0039] The present invention also relates to a control device for operating a friction-fitting shifting element, the control device being configured to implement the above-described method on the control side.

[0040] Therefore, the control device monitors whether an undesirable slippage occurs at the friction-fitted shift element 5 to be operated. When the control device determines that an undesirable slippage occurs at the friction-fitted shift element 5 to be operated, the control device reduces the torque provided by the drive unit 2 in a stepwise manner on the control side to a value related to the maximum torque that can be transmitted by the friction-fitted shift element 5.

[0041] The control device according to the invention is preferably a transmission control device 7. The transmission control device 7 can reduce the torque provided by the drive unit 2 on the control side by transmitting a corresponding control signal for reducing the torque provided by the drive unit 2 to the engine control device 6, which then ultimately reduces the torque provided by the drive unit 2.

[0042] The control device according to the invention is preferably an electronic control device, which has a data interface for exchanging data with components involved in implementing the method according to the invention. For this purpose, it includes, for example, a speed sensor that monitors the rotational speed at the friction-fitted shift element 5 to be operated, in order to determine slippage. Furthermore, these data interfaces include an interface for the transmission control device 7 to communicate with the engine control device 6. In addition, the control device has a processor for data processing and a memory for data storage. Besides these hardware components, the control device also includes software components, i.e., program modules, which are implemented in the control device 7 to implement the method according to the invention.

[0043] List of reference numerals

[0044] 1. Drive System

[0045] 2 Drive Unit

[0046] 3. Transmission

[0047] 4 Driven device

[0048] 5. Shifting components

[0049] 6. Engine control unit

[0050] 7. Transmission control unit

[0051] 8. Drive-side speed

[0052] 9 Driven side speed

[0053] 10. Drive unit torque

[0054] 11 Box - Check Slip

[0055] 12 Boxes - Calculate the Difference

[0056] 13 boxes - Trigger adaptation

Claims

1. A method for operating a friction-fitting shifting element (5) of a motor vehicle, said shifting element being connected between a drive unit (2) of the motor vehicle and a driven device (4) of the motor vehicle, in, Monitor whether undesirable slippage occurs at the friction-fitted shifting element (5). Specifically, when it is determined that undesirable slippage occurs at the friction-fitted shifting element (5), the torque provided by the drive unit (2) is reduced in order to decrease the slippage at the friction-fitted shifting element (5). Its features are, When it is determined that an undesirable slippage occurs at the friction-fitted shift element (5), the torque provided by the drive unit (2) is reduced in a stepwise manner to a value related to the maximum transmittable torque of the friction-fitted shift element (5), and the following additional steps are performed: The difference between the current torque provided by the drive unit (2) that indicates the existence of slippage and the torque currently transmitted by the friction-fitting shift element (5), the currently transmitted torque being derived from the separation force characteristic curve of the friction-fitting shift element (5) based on the current position of the friction-fitting shift element (5) or based on the current operation of the friction-fitting shift element (5), is calculated. When the difference exceeds the limit value, the adaptation of the separation force characteristic curve of the friction-fitted shifting element is triggered.

2. The method according to claim 1, characterized in that, The torque provided by the drive unit (2) decreases stepwise to the value corresponding to the maximum torque that can be transmitted by the friction-fitted shifting element (5).

3. The method according to claim 1, characterized in that, The torque provided by the drive unit (2) is reduced stepwise to the value corresponding to the maximum torque that can be transmitted by the friction-fitted shifting element (5) minus or plus the offset.

4. The method according to any one of claims 1 to 3, characterized in that, As the torque provided by the drive unit (2) decreases in a stepwise manner, the torque of the drive unit (2) is further adapted by sliding down adjustment.

5. The method according to any one of claims 1 to 3, characterized in that, The maximum torque that can be transmitted by the friction-fitted shifting element (5) is as follows: The clamping force of the friction-fitting shift element (5) is determined for at least one position of the shift element. The torque transmitted by the friction-fitting shift element (5) is determined at at least one position of the shift element. For at least one location where the friction-fitting shift element has a clamping force and transmits torque, calculate the quotient of the clamping force of the friction-fitting shift element (5) and the torque transmitted by the friction-fitting shift element (5). The maximum torque that the friction-fitting shift element (5) can transmit is calculated from the calculated quotient and the clamping force at the engagement point of the friction-fitting shift element (5).

6. The method according to claim 1, characterized in that, When the difference is greater than the limit value, the adaptation of the separation force characteristic curve of the friction-fitted shifting element is triggered either directly or at a later time point.

7. A control device for operating a friction-fitted shifting element in a motor vehicle. in, The control device monitors whether undesirable slippage occurs at the friction-fitting shift element (5). When the control device determines that an undesirable slippage occurs at the friction-fitting shift element (5), the control device reduces the torque provided by the drive unit (2) on the control side in order to reduce the slippage at the friction-fitting shift element (5). Its features are, When the control device determines that an undesirable slippage is formed at the friction-fitting shift element (5), the control device, on the control side, reduces the torque provided by the drive unit (2) in a stepwise manner to a value related to the maximum transmittable torque of the friction-fitting shift element (5) and performs the following additional steps: The difference between the current torque provided by the drive unit (2) that indicates the existence of slippage and the torque currently transmitted by the friction-fitting shift element (5), the currently transmitted torque being derived from the separation force characteristic curve of the friction-fitting shift element (5) based on the current position of the friction-fitting shift element (5) or based on the current operation of the friction-fitting shift element (5), is calculated. When the difference exceeds the limit value, the adaptation of the separation force characteristic curve of the friction-fitted shifting element is triggered.

8. The control device according to claim 7, characterized in that, The control device is configured to implement the method according to any one of claims 1 to 6 on the control side.

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