Method and control unit for operating a transmission

Abstract

The invention relates to a method for operating a transmission (12) of a motor vehicle, the transmission comprising at least a plurality of frictionally engaging shifting elements (18), wherein, to carry out a defined gear change from an actual gear to a target gear, a previously closed frictionally engaging shifting element (18) is opened and a previously open frictionally engaging shifting element (18) is closed, and wherein, when the transmission capability of the frictionally engaging shifting element (18) to be opened for the gear change reaches a defined value, the frictionally engaging shifting element (18) to be opened for the gear change and / or an additional frictionally engaging shifting element (18) is operated with slip such that each said shifting element (18) transmits a respective defined torque, until the frictionally engaging shifting element (18) to be closed for the gear change is also operated with slip.

Description

[0001] Method and control unit for operating a transmission

[0002] The invention relates to a method and a control device for operating a transmission of a motor vehicle.

[0003] A motor vehicle's drivetrain consists of a drive unit and a transmission connected between the drive unit and an output. The transmission converts speeds and torques, thus providing the drive unit's tractive power to the output.

[0004] Motor vehicle transmissions that provide multiple gears are known to have multiple shifting elements. These shifting elements can be positive-locking shifting elements, such as claws, and / or friction-locking shifting elements, such as clutches or brakes.

[0005] In each engaged, non-positive gear of a transmission, a first defined number of transmission shift elements is closed, and a second defined number of transmission shift elements is open. When performing a gearshift from an actual gear to a target gear of the transmission, at least one previously closed transmission shift element is opened, and at least one other previously open transmission shift element is closed.

[0006] The present invention relates to a method and control device for operating a transmission, specifically when carrying out a gear change, wherein a previously closed frictional shift element is opened and a previously opened frictional shift element is closed for the gear change.

[0007] A frictional shift element has two halves. In a frictional shift element designed as a clutch, both halves are rotatable. In a frictional shift element designed as a brake, one half of the shift element is rotatable, while the other half is fixed to the housing. When a frictional shift element is closed, uneven surface pressure can develop between the two halves.

[0008] This can then lead to a resulting force that causes vibrations in the transmission. For example, the so-called plate carriers of a friction-locked shifting element can be excited to vibrate, and the transmission housing can also be excited to vibrate. This impairs the achievable shifting quality. Such vibrations also cause noise and can lead to damage or increased wear.

[0009] There is a need to reduce or even eliminate vibrations in the transmission caused by uneven surface pressure in order to improve the achievable shift quality. Furthermore, noise, damage, and increased wear caused by such vibrations should be reduced or even completely eliminated.

[0010] WO 2019 / 122638 A1 discloses a torque transmission device for damping torsional vibrations, wherein the torque transmission device is connected between a crankshaft and a transmission of a motor vehicle. The torque transmission device has a first torque path with a first damper, a second torque path with a second damper, and an actuator that acts on the second damper to compensate for torsional vibrations.

[0011] US 2005 / 0 000 774 A1 discloses a multiple clutch unit for a transmission with a first clutch and a second clutch arranged coaxially to the first clutch, wherein a piston-cylinder unit comprises a substantially pot-shaped cylinder which is non-rotatably but axially connected to a shaft.

[0012] The object of the present invention is to provide a method and a control unit for operating a transmission that at least largely avoids vibrations in the transmission caused by different or unequal surface pressures when closing a friction-locking shift element. This object is achieved by a method according to claim 1 and by a control unit according to claim 6.

[0013] According to the invention, when the transmission capacity of the frictional shifting element to be opened for the gear change reaches a defined value, the frictional shifting element to be opened for the gear change and / or another frictional shifting element is operated in a slipping manner such that the respective shifting element transmits a respective defined torque, namely until the frictional shifting element to be closed for the gear change is still operated in a slipping manner.

[0014] The invention makes it possible to reduce or even completely eliminate vibrations in the transmission caused by uneven surface pressure on a frictionally engaged shifting element and the rotating force resulting from such uneven surface pressure. This can improve shifting quality. Unwanted noise, damage, and increased wear can also be reduced or even completely eliminated.

[0015] Preferably, the frictional shifting element to be opened for the gear change and / or the additional frictional shifting element are operated with slipping such that the respective shifting element transmits the respective defined torque until the frictional shifting element to be closed for the gear change is completely closed, preferably until the frictional shifting element to be closed for the gear change begins to be operated with excessive contact pressure. This also serves to advantageously reduce vibrations in the transmission caused by uneven surface pressure of a frictional shifting element to be closed.

[0016] Preferred developments emerge from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being limited thereto. Herein:

[0017] Fig. 1 is a diagram of a drive train of a motor vehicle,

[0018] Fig. 2 is a timing diagram illustrating the state of the art,

[0019] Fig. 3 is a timing diagram to illustrate a first variant of the invention,

[0020] Fig. 4 is a timing diagram illustrating a second variant of the invention,

[0021] Fig. 5 is a timing diagram to illustrate a third variant of the invention.

[0022] Fig. 1 shows the basic structure of a motor vehicle drive train. Fig. 1 shows a drive unit 10 and an output 11. A transmission 12 and a hydrodynamic starting element 13 are connected between the drive unit 10 and the output 11 in Fig. 1. The hydrodynamic starting element 13 is optional, with the hydrodynamic starting element 13 in Fig. 1 comprising 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 explained, the hydrodynamic starting element 13 is an optional assembly.

[0023] The transmission 12 comprises a plurality of shift elements 18. Five shift elements 18 are shown as an example in Fig. 2. This number of shift elements 18 is purely exemplary. The transmission 12 can also have fewer than five or more than five shift elements 18.

[0024] Furthermore, Fig. 1 shows an engine control unit 19 for controlling and / or regulating the operation of the drive unit 10, as well as a transmission control unit 20 for controlling and / or regulating the operation of the transmission 12 and, in Fig. 1, also the operation of the hydrodynamic starting element 13. According to Fig. 1, the respective control unit 19, 20 exchanges data with the assembly 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.

[0025] The shifting elements 18 of the transmission 12 can be frictionally engaged or positively engaged shifting elements. A frictionally engaged shifting element can be embodied as a clutch or brake. The present invention relates to a method and a control unit for operating a transmission 12 of a motor vehicle, which has at least several frictionally engaged shifting elements 18 and may optionally also include at least one positively engaged shifting element 18.

[0026] For the purposes of the invention, it is assumed that in order to carry out a defined gear change in the transmission 12 from an actual gear to a target gear, a previously closed frictional engagement switching element 18 is opened and a previously opened frictional engagement switching element 18 is closed.

[0027] Fig. 2 illustrates the procedure known from the prior art for executing a gear change, in which a previously closed frictional shift element 18 is opened and a previously opened frictional shift element 18 is closed. Thus, in Fig. 2, two pressure controls 21, 22 are shown over time t, namely a first pressure control 21 for the previously opened shift element 18 to be closed for executing the gear change, and a second pressure control 22 for the previously closed shift element 18 of the transmission 12 to be opened for executing the gear change.

[0028] Before time t1, the actual gear is engaged in transmission 12. It is assumed that at time t1, a request to execute a gearshift from the actual gear to the target gear exists. Starting at time t1, the gearshift from the actual gear to the target gear is to be executed. For this purpose, the shift element closed before time t1 is to be opened via pressure control 22, and the shift element opened before time t1 is to be opened via pressure control 21.

[0029] Between times t1 and t2, a rapid filling takes place first and between times t2 and t3, a filling equalization takes place for the frictional switching element 18 to be closed for the gear change to be carried out.

[0030] Between times t3 and t5, the switching element 18 to be closed for executing the gear change is subsequently closed in a slipping manner, whereby starting at time t4, the switching element 18 to be opened for executing the gear change is opened in a slipping manner in parallel thereto.

[0031] At time t5, the previously closed frictional switching element 18 is completely open, so that it subsequently no longer transmits any torque.

[0032] At time t5, the frictional shift element 18 to be closed for the gear change to be carried out is still in slip mode.

[0033] Between times t5 and t6, the frictional switching element 18 to be closed for executing the gear change continues to be closed in a slipping manner until the previously opened frictional switching element 18 is completely closed at time t6.

[0034] Following time t6, the now closed frictional switching element is operated with overpressure.

[0035] Between times t4 and t5, both switching elements, namely the switching element to be closed and the switching element to be opened, are each operated with slip in order to transfer the torque from the switching element to be opened to the switching element to be closed.

[0036] If an uneven surface pressure develops on the frictional shift element 18, which is to be closed to execute the gear change, due, for example, to a misalignment between the shift element halves of the frictional shift element 18, this can lead to a rotating force on the shift element 18, which can, for example, cause the disk carrier thereof or a transmission housing to vibrate. This is what the present invention aims to prevent.

[0037] In the variant according to the invention of Fig. 3, in order to avoid or eliminate such vibrations based on an uneven surface pressure on the frictional switching element 18 to be closed, when the transmission capacity of the frictional switching element 18 to be opened for the gear change has reached a defined value, the frictional switching element 18 to be opened for the gear change is subsequently operated in a slipping manner.

[0038] The slipping operation of the frictional shift element 18, which is to be opened for the gear change, occurs in Fig. 3 in such a way that it transmits a defined torque, namely until the frictional shift element 18, which is to be closed for the gear change, is still operated in a slipping manner. This defined torque, which serves to avoid or eliminate vibrations resulting from uneven surface pressure on the frictional shift element 18, which is to be closed, is applied or specified by the control system and, in Fig. 3, is transmitted exclusively by the frictional shift element 18, which is to be opened for the gear change.

[0039] Thus, Fig. 3 shows that at time t7, which occurs before time t5, the transmission capacity of the frictional shift element to be opened for the gear change has reached a defined value according to pressure control 22' that is greater than zero. This defined value can be, for example, between 10 and 30 Nm or between 15 and 20 Nm.

[0040] Then, when the transmission capacity of the frictionally engaged switching element 18 to be opened has been reduced via the pressure control 22' to such an extent that at time t7 the transmission capacity of the frictionally engaged switching element 18 to be opened corresponds to the defined torque, the pressure control for the frictionally engaged switching element 18 to be opened is preferably kept constant according to the pressure control 22' following time t7 until time t6, in such a way that the same subsequently transmits the defined torque in a slipping manner, namely until at time t6 the frictionally engaged switching element 18 to be closed is completely closed according to the pressure control 21 and is then operated with overpressure at time t6.

[0041] The defined torque which the frictional switching element 18 to be opened for the gear change transmits from time t7 to time t6 preferably corresponds to the defined value of the transmission capacity which the frictional switching element 18 to be opened for the gear change has reached at time t7.

[0042] This allows vibrations caused by uneven surface pressure on the frictionally engaged switching element 18 to be closed to be largely avoided or even completely eliminated. This can improve switching quality. Unwanted noise, damage, and increased wear can also be reduced or even completely avoided.

[0043] Fig. 4 shows a variant of the invention in which, when the transmission capacity of the frictional shift element 18 to be opened for the gear change has reached the defined value at time t7, the frictional shift element to be opened is further opened according to the pressure control 22. Alternatively, according to the pressure control 23, another frictional shift element, which in itself is neither to be opened nor closed for the execution of the gear change, is operated in a slipping manner. This additional frictional shift element transmits the defined torque in Fig. 4, again until the frictional shift element to be closed for the gear change is still operated in a slipping manner.

[0044] This occurs in Fig. 4 again until time t6, at which time the frictional switching element 18 to be closed for the gear change is fully closed via the pressure control 21 and subsequently operated with overpressure at time t6. The defined torque, which in the variant of Fig. 4 the further frictional switching element 18 transmits from time t7 to time t6, preferably corresponds to the defined value of the transmission capacity that the frictional switching element 18 to be opened for the gear change has reached at time t7.

[0045] The defined torque, which serves to avoid or eliminate vibrations based on an uneven surface pressure on the frictional switching element 18 to be closed, is applied or specified on the control side and is transmitted in Fig. 4 exclusively by the further frictional switching element 18, which in itself can neither be opened nor closed for the gear change.

[0046] Fig. 5 shows a variant of the invention which combines the measures of Figs. 3 and 4. In the variant of Fig. 5, when the transmission capacity of the frictional switching element to be opened for the gear change has been reduced to a defined value at time t7 via the pressure control 22', both the frictional switching element 18 to be opened for the gear change and the further frictional switching element 18 are each operated in a slipping manner. This again continues until the frictional switching element to be closed for the gear change is still operated in a slipping manner via its pressure control 21, i.e. in Fig. 5 until time t6. At time t6, the frictional switching element to be closed is fully closed and is subsequently operated with overpressure after time t6.

[0047] The respective defined torques, which in the variant of Fig. 5 the two shift elements 18 transmit from time t7 to time t6, preferably correspond in sum to the defined value of the transmission capacity that the frictional shift element 18 to be opened for the gear change has reached at time t7. The respective defined torques, which serve to avoid or eliminate vibrations due to uneven surface pressure on the frictional shift element 18 to be closed, are applied or specified by the control system.

[0048] The invention further relates to a control unit configured to automatically execute the method described above. This control unit is preferably the transmission control unit 20, which is designed as an electronic control unit and has both hardware and software means for implementing the method according to the invention. The hardware means include a processor for data processing, a memory for data storage, and at least one interface for exchanging data with the modules involved in executing the method according to the invention. The software means include program modules implemented in the control unit for implementing the method according to the invention.

[0049] To carry out a defined gear change from an actual gear to a target gear, the control unit controls a previously closed frictional switching element 18 to open and a previously opened frictional switching element 18 to close.

[0050] Then, when the transmission capacity of the frictional switching element 18 to be opened for the gear change has reached a defined value, the control unit 20 controls the frictional switching element 18 to be opened for the gear change and / or another frictional switching element 18 to slipping operation in such a way that the respective switching element transmits a defined torque, namely until the frictional switching element to be closed for the gear change is still operated in slipping operation.

[0051] With the invention, vibrations in the transmission, which are caused by an unequal surface pressure between the shift element halves of a frictionally engaged shift element to be closed for a gear change, can be largely avoided or completely eliminated.

[0052] Reference symbol

[0053] drive unit

[0054] downforce

[0055] Gearbox hydrodynamic starting element

[0056] converter

[0057] torque converter lock-up clutch

[0058] turbine wheel

[0059] pump wheel

[0060] switching element

[0061] Engine control unit

[0062] Transmission control unit

[0063] Pressure control, 22' pressure control, 23' pressure control

Claims

Patent claims 1. A method for operating a transmission (12) of a motor vehicle having at least a plurality of frictionally engaged shifting elements (18), wherein, in order to carry out a defined gear change from an actual gear to a target gear, a previously closed frictionally engaged shifting element (18) is opened and a previously opened frictionally engaged shifting element (18) is closed, characterized in that when the transmission capacity of the frictionally engaged shifting element (18) to be opened for the gear change reaches a defined value, the frictionally engaged shifting element (18) to be opened for the gear change and / or a further frictionally engaged shifting element (18) is operated in a slipping manner such that the respective shifting element (18) transmits a respective defined torque, specifically until the frictionally engaged shifting element (18) to be closed for the gear change is still operated in a slipping manner.

2. Method according to claim 1, characterized in that when the transmission capacity of the frictional switching element (18) to be opened for the gear change reaches a defined value, the frictional switching element (18) to be opened for the gear change is operated in a slipping manner such that it transmits the defined torque, specifically until the frictional switching element (18) to be closed for the gear change is still operated in a slipping manner.

3. Method according to claim 1 or 2, characterized in that when the transmission capacity of the frictional switching element (18) to be opened for the gear change reaches a defined value, a further frictional switching element (18) is operated in a slipping manner such that it transmits the defined torque, namely until the frictional switching element (18) to be closed for the gear change is still operated in a slipping manner.

4. Method according to one of claims 1 to 3, characterized in that the frictional switching element (18) to be opened for the gear change and / or the further frictional switching element (18) is operated in a slipping manner such that the respective switching element (18) transmits the respective defined torque, namely until the frictional switching element (18) to be closed for the gear change is completely closed.

5. Method according to claim 4, characterized in that the frictional switching element (18) to be opened for the gear change and / or the further frictional switching element (18) is operated in a slipping manner such that the respective switching element (18) transmits the respective defined torque, namely until the frictional switching element (18) to be closed for the gear change begins to be operated with overpressure.

6. A control unit (20) for operating a transmission (12) of a motor vehicle, which has at least a plurality of frictional shifting elements (18), wherein the control unit (20) controls a previously closed frictional shifting element (18) to open and a previously opened frictional shifting element (18) to close in order to execute a defined gear change from an actual gear to a target gear, characterized in that when the transmission capacity of the frictional shifting element (18) to be opened for the gear change reaches a defined value, the control unit (20) controls the frictional shifting element (18) to be opened for the gear change and / or another frictional shifting element (18) to slipping operation in such a way that the respective shifting element (18) transmits a respective defined torque, namely until the frictional shifting element (18) to be closed for the gear change is still operated in a slipping manner,。 7. Control device (20) according to claim 6, characterized in that the same is set up to carry out the method according to one of claims 1 to 5 on the control side.

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