Method and control unit for operating a transmission

Abstract

Method for operating a transmission (12) of a motor vehicle which has several switching elements (18), wherein the following steps are carried out to adapt a pressure control for a friction-locked switching element (18) to be opened: During the pressure control for the switching element (18) to be opened, it is monitored at what actual time after the start of the pressure control an amount of the difference between the speed of the input shaft of the transmission (12) and the speed of the drive unit (10) reaches or exceeds a first limit value or at what time the speed of the input shaft of the transmission (12) reaches or exceeds a second limit value, wherein this actual time is compared with a predetermined target time, and wherein a first offset is determined depending on the difference between the actual time and the target time.Furthermore, for a first time interval before the fully opening of the switching element (18), a first mean value is determined for the magnitude of the difference between the rotational speed of the input shaft of the transmission (12) and the rotational speed of the drive unit (10). For a second time interval after the fully opening of the switching element (18), a second mean value is determined for the magnitude of the difference between the rotational speed of the input shaft of the transmission (12) and the rotational speed of the drive unit (10). Depending on the difference between the first mean value and the second mean value, a second offset is determined. The pressure control is adapted depending on the first and second offsets.

Description

[0001] The invention relates to a method and a control unit for operating a transmission of a motor vehicle.

[0002] A motor vehicle's powertrain consists of a drive unit and a transmission positioned between the drive unit and an output shaft. The transmission converts speed and torque, thus providing the tractive force from the drive unit to the output shaft.

[0003] Practical motor vehicle transmissions that provide multiple gears have several shifting elements. These shifting elements can be positive-locking elements, such as dog clutches, and / or friction-locking elements, such as clutches or brakes.

[0004] In each engaged, friction-fit gear of a transmission, a first defined number of the transmission's shift elements are closed, and a second defined number of the transmission's shift elements are open. When a gear change is performed from the current gear to a target gear, at least one previously closed shift element is opened, and at least one other previously open shift element is closed.

[0005] To open a previously closed switching element of the transmission, it is actuated by a first pressure control signal specified by the control unit. To close the previously opened switching element, it is actuated by a second pressure control signal specified by the control unit. As explained, these pressure control signals are specified by the control unit and implemented in a control unit of the transmission. To compensate for component tolerances and wear, the pressure control signals are adapted. The present invention relates to details that serve to adapt a control-specified pressure control signal for a previously closed and to be opened friction-fit switching element.

[0006] The object of the present invention is to provide a method for operating a motor vehicle transmission by means of which a predetermined pressure control can be advantageously adapted for a friction-fit switching element to be opened for a gear change to be performed.

[0007] This problem is solved by a method according to claim 1 and by a control unit according to claim 10.

[0008] According to the invention, the following steps are performed to adapt the first predetermined pressure control for the friction-fit switching element to be opened for the gear change to be performed: During the first pressure control for the friction-fit switching element to be opened for the gear change to be performed, it is monitored at what actual time after the start of the first pressure control the amount of the difference between the speed of the input shaft of the transmission and the speed of the drive unit reaches or exceeds a first limit value, or at what actual time after the start of the first pressure control the speed of the input shaft of the transmission reaches or exceeds a second limit value, wherein this actual time is compared with a predetermined target time, and wherein a first offset for the adaptation of the first predetermined pressure control is determined depending on the difference between the actual time and the target time.Furthermore, for the friction-fit switching element to be opened for the gear change, a first mean value for the difference between the speed of the transmission input shaft and the speed of the drive unit is determined for a first time period before the friction-fit switching element is fully opened, and a second mean value for the difference between the speed of the transmission input shaft and the speed of the drive unit is determined for a second time period after the friction-fit switching element is fully opened. Depending on the difference between the first mean value and the second mean value, a second offset for adapting the first predetermined pressure control is determined. The first predetermined pressure control is adapted depending on the first offset and the second offset.

[0009] The invention allows for an advantageous adaptation of a pressure control for a friction-fit switching element to be opened in the transmission of the motor vehicle for a gear change to be carried out, and therefore a particularly advantageous switching design.

[0010] Preferably, the first predetermined pressure control for the friction-fit switching element to be opened for the gear change to be performed is characterized by time intervals with temporal gradients of the pressure profile over time, wherein, depending on the first offset and the second offset, the first predetermined pressure control for the friction-fit switching element to be opened for the gear change to be performed is adapted such that the level of the pressure profile over time between the beginning of the first pressure control and the end thereof is adjusted, wherein, depending on the first offset and the second offset, the first predetermined pressure control for the friction-fit switching element to be opened for the gear change to be performed is adapted such thatthat, while maintaining the length of the time intervals of the pressure curve, the magnitude of the respective time gradient of the pressure curve is adjusted for at least some time intervals. This allows for a particularly advantageous adaptation of the pressure control for the friction-fit switching element to be opened, and thus a particularly advantageous circuit design.

[0011] Preferably, depending on the first offset, the level of the pressure profile over time for the friction-fit switching element to be opened for the gear change is adjusted such that, between the start of the first pressure application and a fixed first point in time of a change in the temporal gradient of the pressure profile, the temporal gradient is changed, and subsequently, while maintaining the temporal gradient, the level of the pressure profile is shifted by the first offset. This allows for a particularly advantageous adaptation of the pressure control for the friction-fit switching element to be opened and thus a particularly advantageous circuit design.

[0012] Preferably, depending on the second offset, the level of the pressure profile over time of the first pressure control for the friction-locked switching element to be opened for the gear change to be performed, which has the same level when the switching element to be opened is fully open or at a time that is a defined time period before the switching element to be opened is shifted by the second offset.Furthermore, depending on the second offset, the level of the pressure curve over time of the first pressure control is adjusted between the time at which the amount of the difference between the speed of the input shaft of the gearbox and the speed of the drive unit reaches or exceeds the first limit value, or at which the speed of the input shaft of the gearbox reaches or exceeds the second limit value, or a time that lies a defined time interval after this time, and the time at which the switching element to be opened is fully open.In particular, a second point in time of a change in the temporal gradient of the pressure control between the point in time at which the amount of the difference between the speed of the input shaft of the transmission and the speed of the drive unit reaches or exceeds the first limit value or at which the speed of the input shaft of the transmission reaches or exceeds the second limit value, and the point in time at which the switching element to be opened is fully open, remains unchanged; however, the respective temporal gradient of the temporal pressure profile before and after the second point in time is adjusted depending on the second offset.

[0013] 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 diagram of a motor vehicle's drivetrain, Fig. 2 a time diagram to illustrate the invention, Fig. 3 a time diagram to further illustrate the invention, Fig. 4. An excerpt from a time diagram analogous to the time diagram of the Fig. 3 to illustrate a modification of the invention.

[0014] Fig. Figure 1 shows the basic structure of a motor vehicle's powertrain. Thus, it shows Fig. 1. A drive unit 10 and an output 11. Between the drive unit 10 and the output 11 are in Fig. 1. A transmission 12 and a hydrodynamic starting element 13 are engaged. The hydrodynamic starting element 13 is optional, wherein the hydrodynamic starting element 13 is in Fig. Figure 1 comprises a converter 14 and a converter lock-up clutch 15. A turbine wheel 16 and a pump wheel 17 of the converter 14 are shown. As already stated, the hydrodynamic starting element 13 is an optional assembly.

[0015] The gearbox 12 has several switching elements 18. Fig. Figure 1 shows an example of a switching element 18, which is designed as a friction-fit switching element, namely as a clutch or brake. In each engaged gear of the transmission 12, a first number of switching elements 18 are closed and a second number of switching elements 18 are open.

[0016] If a gear change from an actual gear to a target gear is to be carried out, a switching element 18 that is closed in the actual gear is opened via a first predetermined pressure control and a switching element 18 that is open in the actual gear is closed via a second predetermined pressure control.

[0017] Furthermore, it shows Fig. 1 an engine control unit 19 to control and / or regulate the operation of the drive unit 10, and a transmission control unit 20 to control the operation of the transmission 12 and in Fig. 1 also to control and / or regulate the operation of the hydrodynamic starting element 13.

[0018] According to Fig. 1. The respective control unit 19, 20 exchanges data with the component group to be controlled and / or regulated by the respective control unit 19, 20. Furthermore, the engine control unit 19 and the transmission control unit 20 exchange data with each other.

[0019] The invention now relates to a method and a control unit for operating the transmission 12, namely for performing a gear change from an actual gear to a target gear, wherein the switching element 18 to be opened for the gear change is a friction-locking switching element, the predetermined pressure control of which is to be adapted.

[0020] The following steps are performed to adapt the specified initial pressure control for the friction-fit switching element to be opened for the gear change to be executed: During the pressure control for the friction-locked switching element 18 to be opened for the gear change to be performed, it is monitored at what actual time after the start of the pressure control an amount of the difference between the speed of the input shaft of the transmission 12 and the speed of the drive unit 10 reaches a first limit value or at what actual time after the start of the first pressure control the speed of the input shaft of the transmission reaches or exceeds a second limit value.

[0021] In the Fig. In the embodiment shown in Figure 1, in which the hydrodynamic starting element 19 is connected between the transmission 12 and the drive unit 10, the difference between the speed of the input shaft of the transmission 12 and the speed of the drive unit 10 corresponds to the difference between the speed of the pump wheel 17 and the speed of the turbine wheel 16 or a speed difference at the converter lock-up clutch 15.

[0022] This actual time, at which, after the start of the pressure control for the friction-locking switching element 18 to be opened, the difference between the speed of the input shaft of the transmission and the speed of the drive unit reaches or exceeds the first limit value, or at which, after the start of the first pressure control, the speed of the input shaft of the transmission reaches or exceeds a second limit value, is compared with a predetermined target time, whereby, depending on the difference between the actual time and the target time, a first offset for the adaptation of the predetermined pressure control is determined.

[0023] In particular, in the area of ​​one end of the first pressure control for the friction-fit switching element 18 to be opened for the gear change to be performed, a first mean value for the amount of the difference between the rotational speed of the input shaft of the transmission 12 and the rotational speed of the drive unit 10 is determined for a first time period before the switching element 18 to be opened is completely opened, and a second mean value for the amount of the difference between the rotational speed of the input shaft of the transmission 12 and the rotational speed of the drive unit 10 is determined for a second time period after the switching element 18 to be opened is completely opened, whereby a second offset for the adaptation of the pressure control of the friction-fit switching element 18 to be opened is determined depending on the difference between the first mean value and the second mean value.

[0024] The specified initial pressure control for the friction-locked switching element to be opened is then adapted depending on the first and second offsets.

[0025] Further details of the invention are described below with reference to the time diagrams of the Fig. 2, Fig. 3 and Fig. 4 described. Fig. 2 and Fig. Figure 3 shows several time-dependent curves over time t, such as curve 21 showing the speed of the drive unit 10, curve 22 showing the speed of the gearbox input speed, and curve 23 showing the first pressure control for the friction-fit switching element 18 to be opened. Fig. Figure 4 shows a section of a curve 23 and thus a section of a time course of the first pressure control for the friction-locked switching element 18 to be opened.

[0026] According to Fig. 2 and Fig. The first pressure control 23 for the friction-fit switching element to be opened is characterized by time intervals Δt1, Δt2, and Δt3 with temporal gradients of the pressure profile. Thus, the pressure control 23 for the friction-fit switching element 18 to be opened begins at time t0, whereby in the first time interval Δt1 between times t0 and t1, the pressure profile exhibits a first temporal gradient.

[0027] At time t1, the temporal gradient changes, remaining unchanged until time t2, i.e., constant during the time interval Δt2. The second time interval Δt2, which ends at time t2, is followed by the third time interval Δt3, extending to time t3. During this third time interval Δt3, the temporal gradient of the pressure profile is also constant, but differs from the temporal gradient of the first time interval Δt1 and the gradient of the second time interval Δt2.

[0028] Starting with the pressure control at time t0, the system monitors at what actual time after the start of the first pressure control the difference between the speed of the input shaft of the gearbox 12 and the speed of the drive unit 10 reaches or exceeds a first limit value, or at what actual time after the start of the first pressure control the speed of the input shaft of the gearbox 12 reaches or exceeds a second limit value. This actual time is compared with a target time. Fig. Figure 2 shows the target time tSOLL and, as examples, two actual times tIST1 and tISZ2. Depending on the difference between the respective actual time tIST1, tIST2 and the target time tSOLL, a first offset for the adaptation of the print control 23 is determined.

[0029] According to the dashed curve, the Fig. If the actual time tIST2 is after the target time tSOLL, a first offset is determined, as a result of which the level of the print control 23 is lowered. If, on the other hand, the actual time tIST1 is according to the dashed curve of the Fig. 2 before the target time tSOLL, then according to Fig. 2. The pressure level of the print gradient is raised via a corresponding first offset.

[0030] Depending on the first offset, the level of the pressure curve over time of the first pressure control is adjusted such that the actual time at which the amount of the difference between the speed of the input shaft of the gearbox 12 and the speed of the drive unit 10 reaches or exceeds the first limit value, or at which, after the start of the first pressure control, the speed of the input shaft of the gearbox reaches or exceeds a second limit value, is approximated to the specified target time tSOLL.

[0031] How Fig. 2, depending on the first offset, the level of the temporal pressure profile of the first pressure control for the friction-locking switching element 18 to be opened is adjusted such that in the time interval Δt1 both the temporal gradient of the first pressure control and the level of the pressure profile of the pressure control are adjusted, whereas in the time interval Δt2 the temporal gradient of the pressure control remains unchanged, but the pressure level of the first pressure control is changed by parallel shift of the temporal pressure profile.

[0032] Time t1 and time t2, i.e., the time intervals Δt1 and Δt2, remain unchanged. The first time t1, at which the time gradient of the pressure profile changes after time t0, therefore remains unchanged.

[0033] As already explained, in addition to the first offset, according to which the temporal gradient of the pressure profile of the first pressure control is adjusted during the first time interval Δt1 and the level of the temporal pressure profile of the first pressure control is adjusted during the time interval Δt2 by parallel shifting of the temporal gradient, a second offset is determined. This will be explained below with reference to Fig. 3 described.

[0034] To determine the second offset, a first mean value for the difference between the rotational speed of the input shaft of the gearbox 12 and the rotational speed of the drive unit 10 is determined, particularly towards the end of the pressure control phase, for the friction-locking switching element 18 to be opened. This first mean value is determined for a first time interval Δt4 before the friction-locking switching element 18 is fully opened. A second mean value for the difference between the rotational speed of the input shaft of the gearbox 12 and the rotational speed of the drive unit 10 is determined for a second time interval Δt5 after the friction-locking switching element 18 is fully opened. At time t3, the friction-locking switching element 18 is fully open.

[0035] Furthermore, a difference is determined between the first mean value calculated for the first time interval Δt4 and the second mean value calculated for the second time interval Δt5. Depending on this difference between the first and second mean values, a second offset is determined for adapting the pressure control of the switching element to be opened.

[0036] In Fig. 3. To adapt the pressure control, depending on the second offset, the level of the pressure curve over time, which the pressure control has when the switching element to be opened is fully opened at time t3, is shifted by the second offset.

[0037] This is in Fig. Figure 3 shows two different cases using the dashed line and the dash-dotted line, where, according to the dashed line, the pressure level of the time-dependent pressure profile is lowered at time t3, and according to the dash-dotted line, the time-dependent pressure level of the time-dependent pressure profile is raised at time t3.

[0038] When adjusting the pressure control for the friction-locked switching element 18 to be opened depending on the second offset, the temporal profile of the pressure control between the target time tSOLL and the time t3 is also adjusted, whereby the times tSOLL, t2 and t3 remain unchanged, but the temporal gradient of the pressure profile between the times tSOLL and t2 as well as between the times t2 and t3 is adjusted depending on the second offset.

[0039] For example, if time t2 lies in the middle between times tSOLL and t3, the pressure level at time t2 will be shifted by 50% of the second offset by which the pressure level at time t3 is shifted.

[0040] If time t2 is closer to time t3, the shift in the pressure level at time t2 is greater than 50%; if time t2 is closer to time tSOLL, the shift in the pressure level at time t2 is less than 50%.

[0041] Alternatively, as in Fig. As shown in Figure 4, the level of the pressure profile over time during the first pressure control is shifted by the second offset at time t7, which is a defined time interval Δt7 before the fully opening of the switching element 18 at time t3. In this case, the level of the pressure profile is then subsequently shifted by the second offset from time t7 to time t3, when the switching element 18 is fully opening, while maintaining the time gradient. Time t7 is before time t3 and after time t2.

[0042] Furthermore, it shows Fig. 4. Depending on the second offset, the level of the pressure profile over time for the first pressure control can also be adjusted between time t6, which lies a defined time interval Δt6 after time tSOLL, and time t3. Time tSOLL corresponds to the time at which the magnitude of the difference between the rotational speed of the input shaft of the gearbox 12 and the rotational speed of the drive unit 10 reaches or exceeds the first limit value, or at which the rotational speed of the input shaft of the gearbox 12 reaches or exceeds the second limit value. Time t3 corresponds to the time at which the switching element 18 to be opened is fully open. Time t6 lies before time t2 and after time tSOLL.

[0043] Is as in Fig. As shown in Figure 4, if the time interval Δt7 is greater than zero, meaning that time t7 precedes time t3, the pressure profile is adjusted between times t7 and t3 as described above, maintaining the time gradient by a parallel shift of the second offset. Between times t6 and t7, the pressure profile is adjusted analogously to the adjustment according to Figure 4. Fig. 3, i.e., while maintaining time t2 by adjusting the respective temporal gradient of the pressure profile before and after time t2, i.e., between times t6 and t2 and times t2 and t7.

[0044] The invention further relates to a control unit configured to automatically execute the above-described method. This control unit is preferably the transmission control unit 20, which is designed as an electronic control unit. It 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 the engine control unit 19, which provides the drive unit speed 21, with the transmission 12, which provides the transmission input speed 22, and with the transmission 12 to provide it with the pressure control 23. The hardware means also include a processor for data processing and a memory for data storage.The software-related means include program modules that are implemented in the control unit for carrying out the method according to the invention.

[0045] The invention allows for an advantageous adaptation of a friction-locked switching element 18 that is to be opened during a gear change, namely the adaptation of the pressure control stored in the transmission control unit 20 for the same. In this way, the switching element 18 can be opened more precisely, thus improving the shifting performance. Reference sign 10 Drive unit 11 Drive 12 gearboxes 13 hydrodynamic starting element 14 converters 15 Torque converter lock-up clutch 16 Turbine wheel 17 Pump wheel 18 switching element 19 Engine control unit 20 Transmission control unit 21 Drive unit speed 22 Gearbox input speed 23 Pressure control

Claims

[1] Method for operating a transmission (12) of a motor vehicle which has several switching elements (18), wherein, to execute a gear change from an actual gear to a target gear, a switching element (18) closed in the actual gear is opened via a first predetermined pressure control and a switching element (18) open in the actual gear is closed via a second predetermined pressure control, characterized by , that The following steps are carried out to adapt the first specified pressure control for a friction-fit switching element (18) to be opened for the gear change to be performed: During the first pressure actuation for the switching element (18) to be opened for the gear change to be performed, the system monitors at what actual time after the start of the first pressure actuation the amount of the difference between the speed of the input shaft of the transmission (12) and the speed of the drive unit (10) reaches or exceeds a first limit value, or the speed of the input shaft of the transmission (12) reaches or exceeds a second limit value, whereby this actual time is compared with a predetermined target time, and whereby, depending on the difference between the actual time and the target time, a first offset for the adaptation of the first predetermined pressure actuation is determined. Furthermore, for a first time period before the fully opening of the switching element (18) to be opened, a first mean value for the amount of the difference between the rotational speed of the input shaft of the transmission (12) and the rotational speed of the drive unit (10) is determined, and for a second time period after the fully opening of the switching element (18) to be opened, a second mean value for the amount of the difference between the rotational speed of the input shaft of the transmission (12) and the rotational speed of the drive unit (10) is determined, whereby, depending on the difference between the first mean value and the second mean value, a second offset for the adaptation of the first predetermined pressure control is determined. The first predefined print control is adapted depending on the first offset and the second offset. [2] Method according to claim 1, characterized by, that the first predetermined pressure control is characterized by time intervals with temporal gradients of the temporal pressure profile, whereby, depending on the first offset and the second offset, the first predetermined pressure control is adapted in such a way that the level of the temporal pressure profile between the beginning of the first pressure control and the end of the same is adjusted. [3] Method according to claim 2, characterized by , that depending on the first offset and the second offset, the first specified pressure control is adapted in such a way that, while maintaining the length of the time intervals for at least some time intervals, the amount of the respective temporal gradient of the temporal pressure profile is adjusted. [4] Method according to any one of claims 1 to 3, characterized by, that depending on the first offset, the level of the pressure curve over time of the first pressure control is adjusted in such a way that the actual time at which the amount of the difference between the speed of the input shaft of the gearbox (12) and the speed of the drive unit (10) reaches or exceeds the first limit value or at which the speed of the input shaft of the gearbox (12) reaches or exceeds the second limit value, is approximated to the specified target time. [5] Method according to any one of claims 1 to 4, characterized by, that depending on the first offset, the level of the temporal pressure profile of the first pressure control is adjusted such that between a start of the first pressure control and an unchanging first time point of a change in the temporal gradient of the temporal pressure profile, the temporal gradient is changed and subsequently, while maintaining the temporal gradient, the level of the temporal pressure profile is shifted by the first offset. [6] Method according to any one of claims 1 to 5, characterized by , that depending on the second offset, the level of the temporal pressure profile of the first pressure control, which it exhibits when the switching element (18) to be opened is fully opened or at a time that is a defined time period before the switching element (18) to be opened is shifted by the second offset. [7] Method according to claim 6, characterized by, that if, depending on the second offset, the level of the temporal pressure profile at the time which is a defined time interval before the complete opening of the switching element (18) to be opened is shifted by the second offset, the level of the temporal pressure profile is subsequently shifted by the second offset until the time of complete opening while maintaining the temporal gradient. [8] Method according to any one of claims 1 to 7, characterized by, that depending on the second offset, the level of the pressure profile over time of the first pressure control is adjusted between the time at which the amount of the difference between the speed of the input shaft of the gearbox (12) and the speed of the drive unit (10) reaches or exceeds the first limit value or at which the speed of the input shaft of the gearbox (12) reaches or exceeds the second limit value, or a time that lies a defined time interval after this time, and the time at which the switching element (18) to be opened is fully opened. [9] Method according to claim 8, characterized by, that a second point in time of a change in the temporal gradient of the pressure control between the point in time at which the amount of the difference between the speed of the input shaft of the transmission (12) and the speed of the drive unit (10) reaches or exceeds the first limit value or at which the speed of the input shaft of the transmission (12) reaches or exceeds the second limit value, and the point in time at which the switching element (18) to be opened is fully open remains unchanged, but the respective temporal gradient of the temporal pressure profile before and after the second point in time is adjusted depending on the second offset. [10] Control unit (20) for operating a transmission (12) of a motor vehicle, characterized by , that the same is set up to execute the method according to one of claims 1 to 9 on the control side.

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