Method and control device for operating a transmission of a motor vehicle

Abstract

The invention relates to a method for operating a transmission (2) of a motor vehicle, wherein, in order to trigger a gear shift in the transmission (2), a trigger rotational speed is determined with which a gear shift to be carried out is triggered at the control side as a function of a reaction time of the gear shift to be carried out, as a function of a gradient of a rotational speed of the motor vehicle side and as a function of a maximum permissible limit rotational speed for the rotational speed of the motor vehicle side, such that the rotational speed of the motor vehicle side does not exceed the maximum permissible limit rotational speed when the gear shift is carried out, wherein the trigger rotational speed with which the gear shift to be carried out in the transmission (2) is triggered at the control side is adjusted as a function of a driver requested torque. The invention also relates to a control device (6) for operating a transmission (2) of a motor vehicle.

Description

TECHNICAL FIELD

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

[0002] A motor vehicle has a drive assembly and a transmission connected between the drive assembly and a driven device. When a shift is implemented in the transmission, i.e. when a gear is switched, the actual gear of the shift to be implemented is switched to the target gear of the shift to be implemented. The shift is triggered at the control side when a rotational speed at the motor vehicle side, in particular a rotational speed of the drive assembly or a rotational speed of the driven device, reaches a trigger rotational speed. The rotational speed of the driven device is in a defined proportion to the rotational speed of the drive assembly depending on the transmission ratio of the actual gear. BACKGROUND

[0003] From DE 10 2006 016 710 A1 a method for operating a transmission of a motor vehicle, i.e. for triggering a shift in the transmission, is known, in which method a maximum permissible engine rotational speed is predefined on the one hand and a gear switching maximum engine rotational speed, which is smaller than the maximum permissible engine rotational speed, is predefined on the other hand. If the engine rotational speed can exceed the maximum permissible engine rotational speed, the engine rotational speed has to be adjusted. In order to prevent this, the gear switching maximum engine rotational speed is smaller than the maximum permissible engine rotational speed. It is known from DE 10 2006 016 710 A1 to determine a trigger rotational speed from the gear switching maximum engine rotational speed, from a gradient of the engine rotational speed and from a reaction time of the shift to be implemented, at which trigger rotational speed the shift to be implemented is triggered at the control side. The reaction time of the shift to be implemented is the period of time which elapses after the shift is triggered at the control side until the rotational speed conversion device starts to convert the engine rotational speed from a synchronization rotational speed of the actual gear of the shift to be implemented to a synchronization rotational speed of the target gear of the shift to be implemented.

[0004] In order to ensure as sporty a shift as possible, the shift should be triggered as late as possible, in particular at as high a permissible limit rotational speed as possible for the shift to be implemented, which means that the gear switching maximum engine rotational speed should be as close as possible to the maximum permissible engine rotational speed.

[0005] The gradient of the rotational speed at the motor vehicle side, by means of which the trigger rotational speed for triggering the shift is determined, is not precisely known. In the known method, this can lead to the trigger rotational speed for triggering the shift to be implemented being determined incorrectly and, when the limit rotational speed for the shift to be implemented, which is also referred to as the gear switching maximum engine rotational speed, is close to the maximum permissible engine rotational speed, the engine rotational speed exceeds the maximum permissible engine rotational speed when the shift is implemented, so that subsequently the engine rotational speed has to be adjusted. This is disadvantageous.

[0006] There is a need to more precisely determine the trigger rotational speed for a shift to be carried out in a transmission of a motor vehicle, so that on the one hand an acceleration loss can be avoided when carrying out the shift, and on the other hand an intervention of a regulator which regulates the engine rotational speed when carrying out the shift is avoided. SUMMARY

[0007] The object underlying the present application is to provide a novel method for operating a transmission of a motor vehicle. This object is achieved by a method for operating a transmission of a motor vehicle having the features of the present application. According to the present application, the trigger rotational speed with which a shift to be carried out in the transmission is triggered on the control side is adjusted in dependence on a driver requested torque. The trigger rotational speed for a shift to be carried out can advantageously be adjusted in dependence on a driver requested torque. An acceleration loss due to a too low shift point can likewise be avoided as well as an intervention of a regulator which regulates the engine rotational speed.

[0008] According to an advantageous refinement of the present application, the trigger rotational speed for a shift to be carried out is also adjusted in dependence on an actually provided engine actual torque, preferably in dependence on a difference or ratio between a driver requested torque and an actually provided engine actual torque. The trigger rotational speed can also be more advantageously adjusted, in particular in the case of avoiding an acceleration loss as well as an intervention of a regulator, when it is also adjusted in dependence on an actually provided engine actual torque, in particular preferably in dependence on a difference or ratio between a driver requested torque and an actually provided engine actual torque.

[0009] According to an advantageous refinement of the present application, an offset value with which the trigger rotational speed for a shift to be carried out is adjusted is determined in dependence on a driver requested torque and preferably in dependence on a difference or ratio between a driver requested torque and an actually provided engine actual torque, preferably in dependence on a characteristic curve. The determination of an offset value with which the trigger rotational speed is adjusted is particularly preferred.

[0010] Preferably, when the driver requested torque is smaller than a limit value, an offset value is predefined which is identical for all differences or ratios between the driver requested torque and the actually provided engine actual torque. Preferably, when the driver requested torque is greater than a limit value, an offset value is predefined which is greater the greater the difference or ratio between the driver requested torque and the actually provided engine actual torque. This allows the trigger rotational speed for a shift to be carried out to be particularly advantageously adjusted in the case of avoiding an acceleration loss as well as an intervention of a regulator.

[0011] The object of the present application is also achieved by a control device for operating a hybrid vehicle according to the present application. BRIEF DESCRIPTION OF DRAWINGS

[0012] Preferred refinements are given from the preferred embodiments and the following description. Embodiments of the application are explained in detail by means of the drawings, without being restricted thereto. In the drawings:

[0013] Figure 1 A powertrain diagram of a motor vehicle is shown;

[0014] Figure 2 A time diagram with a rotational speed curve and a torque curve is shown when a gear shift is carried out;

[0015] Figure 3 A time diagram with a further torque curve is shown.

[0016] LIST OF REFERENCE SIGNS

[0017] 1 drive assembly

[0018] 2 transmission

[0019] 3 driven device

[0020] 4 shift element

[0021] 5 engine control device

[0022] 6 transmission control device DETAILED DESCRIPTION

[0023] Figure 1 A powertrain diagram of a motor vehicle is shown highly schematically, wherein the motor vehicle comprises a drive assembly 1, a transmission 2 and a driven device 3.

[0024] The drive assembly 1 can be a combustion engine. Furthermore, the drive assembly 1 can be an electric machine. In a hybrid vehicle, the drive assembly 1 comprises a combustion engine and an electric machine.

[0025] The transmission 2 is connected between the drive assembly 1 and the driven device 3. The transmission 2 converts rotational speed and torque and provides a tractive force of the drive assembly 1 on the driven device 3.

[0026] The transmission 2 is an automatic stepless transmission providing a plurality of gears. Thus, the transmission 2 comprises a plurality of shift elements 4, which can be implemented as frictionally engaging shift elements and / or as positively engaging shift elements. Depending on which shift elements 4 of the transmission 2 are closed or open, a defined gear is engaged in the transmission 2.

[0027] If a gear shift or a gear change from an actual gear to a target gear is to be carried out, at least one previously closed shift element 4 is opened and at least one previously open shift element 4 is closed.

[0028] Figure 1 The control-side components are also shown, namely, an engine control unit 5 for controlling and / or regulating the operation of the drive unit 1 and a transmission control unit 6 for controlling and / or regulating the operation of the transmission 2. According to the dashed arrows, the engine control unit 5 exchanges data with the drive unit 1, and the transmission control unit 6 exchanges data with the transmission 2. Furthermore, the engine control unit 5 and the transmission control unit 6 exchange data with each other.

[0029] As already implemented, gear shifting or gear change from the actual gear to the target gear can be performed in the transmission 2. This shift is triggered on the control side, especially by the transmission control device 6 (i.e., when the speed on the motor vehicle side, especially the speed of the driven device 3 or the speed of the drive unit 1, reaches or exceeds the trigger speed).

[0030] The rotational speed of the drive unit 1 depends on the gear ratio of the actual gear engaged in the transmission 2 and is in a limited ratio to the rotational speed at the driven device 3.

[0031] Gear shifts can also be triggered based on the engine speed on the transmission side.

[0032] Figure 2 The curves showing the changes in speed n and torque M over time t are shown; these curves can be generated when upshifting is performed in transmission 2.

[0033] At time t1, the control side requests an upshift in transmission 2. Only at time t2 does the speed change begin from the synchronous speed of the actual gear to be upshifted to the synchronous speed of the target gear to be upshifted. The time interval T between time t2 and t1 is also referred to as the reaction time T of the shift to be performed.

[0034] When upshifting is performed, and drive unit 1 provides a constant torque M1 during the shift, a... Figure 2 The rotational speed curve n1.

[0035] When upshifting in transmission 2, it should be considered that the torque M provided by drive unit 1 is not constant. Therefore, Figure 2 Torque curves M2 and M3 show the torque curves when the torque provided by drive unit 1 is temporarily reduced during gear shifting, thereby subsequently forming speed curves n2 and n3 during gear shifting; that is, speed curve n2 is formed for torque M2 and speed curve n3 is formed for torque M3. Here, Figure 2 As shown, the more the torque provided by drive unit 1 decreases during gear shifting, the lower the speed at the end of the reaction time T.

[0036] The application now relates to optimally determining a triggering rotational speed with which a gear shift, for example an upshift, to be carried out in the transmission 2 is triggered on the control side, in particular to be able to avoid an acceleration loss when carrying out the gear shift and also to be able to avoid a rotational speed adjustment of the drive assembly 1.

[0037] In order to obtain a triggering rotational speed for a gear shift to be carried out in the transmission 2, the triggering rotational speed with which the upshift to be carried out is triggered on the control side, i.e. when the rotational speed of the respective motor vehicle side reaches or exceeds the triggering rotational speed, is determined from the reaction time T known on the control side for the gear shift to be carried out, from the gradient of the rotational speed n of the respective motor vehicle side likewise known on the control side and from the maximum permissible limit rotational speed of the upshift to be carried out, which is the maximum that the rotational speed of the respective motor vehicle side can have at the end of the reaction time T and is predefined on the control side. This determination of the triggering rotational speed is known, for example, from DE 10 2006 016 710 A1.

[0038] It is proposed according to the application that the triggering rotational speed determined from the reaction time T for the gear shift to be carried out, from the gradient of the rotational speed of the respective motor vehicle side and from the maximum permissible limit rotational speed of the rotational speed of the respective motor vehicle side is adjusted, in particular from the driver demand torque and preferably also from the engine actual torque actually provided by the drive assembly 1. In particular, the triggering rotational speed is adjusted from the driver demand torque and from the difference or ratio between the driver demand torque and the engine actual torque actually provided by the drive assembly 1. Reference is subsequently made to the difference between the driver demand torque and the engine actual torque actually provided.

[0039] Figure 3 The torque curves, i.e. the curve of the driver demand torque MFW and the curve of the engine actual torque MIST provided by the drive assembly 1, are shown as a function of time t. Here, at the point in time at which the gear shift is triggered, at the point in time t1, the engine actual torque MIST1 is closer to the driver demand torque MFW than the engine actual torque MIST2.

[0040] The application is based on the recognition that the triggering rotational speed determined from the reaction time T, from the gradient of the rotational speed of the respective motor vehicle side and from the maximum permissible limit rotational speed of the rotational speed of the respective motor vehicle side can advantageously be adjusted from the driver demand torque MFW and preferably from the engine actual torque MIST actually provided by the drive assembly 1 in order to carry out the upshift on the one hand with as little acceleration loss as possible and on the other hand to avoid a rotational speed adjustment of the drive assembly 1. Here, preferably, an offset value with which the triggering rotational speed is adjusted is determined from the driver demand torque and from the difference between the driver demand torque and the engine actual torque actually provided by the drive assembly 1, wherein the offset value is preferably determined from a characteristic curve.

[0041] Here, the offset value is preferably given in advance as follows: when the driver demand torque is less than the limit value, the same offset value is given for all differences between the driver demand torque and the actual engine actual torque provided.

[0042] Conversely, if the driver demand torque is greater than the limit value, the offset value is preferably given in advance as follows: the greater the difference between the driver demand torque and the actual engine actual torque provided, the greater the offset value.

[0043] The following table exemplarily reflects such a characteristic curve.

[0044]

[0045]

[0046] It can thus be taken from the above table that, when the driver demand torque is less than the limit value, in particular less than 400 Nm, a constant offset value of -50 U / min is given for all differences between the driver demand torque and the actual engine actual torque.

[0047] Conversely, if the driver demand torque is greater than the limit value, in particular greater than 400 Nm, the size of the offset value depends not only on the driver demand torque but also on the difference between the driver demand torque and the actual engine actual torque, wherein the greater the difference between the driver demand torque and the actual engine actual torque, the greater the offset value.

[0048] The trigger speed determined from the reaction time T, from the gradient of the rotational speed of the respective motor vehicle side and from the maximum permissible limit rotational speed of the rotational speed of the respective motor vehicle side is compensated with the offset value.

[0049] The method is particularly advantageous for traction upshifts.

[0050] In a hybrid vehicle, the driver demand torque and the actual engine actual torque provided are the total torques of the combustion engine and the electric machine.

[0051] The driver demand torque, the actual engine actual torque provided and the difference or ratio between the driver demand torque and the actual engine actual torque provided can be smoothed in time and dithered using a filter.

[0052] The application also relates to a control device for operating a transmission 2 of a motor vehicle, wherein the control device is a transmission control device 6. The control device is configured to implement the above-described method on the control side. Thus, the control device for implementing a gear shift in the transmission determines a trigger rotational speed for the gear shift depending on a reaction time T of the gear shift to be implemented, depending on a gradient of a rotational speed of the drive assembly 1 or of the driven device 3 and depending on a maximum permissible limit rotational speed of the rotational speed of the drive assembly 1 or of the driven device 3. The trigger rotational speed thus determined is adjusted, in particular depending on a torque requested by the driver and preferably depending on a difference between the torque requested by the driver and an engine actual torque actually provided by the drive assembly 1, more precisely in particular in the case of determining a characteristic curve-dependent offset value.

[0053] The control device 6 comprises means in order to implement the method according to the application on the control side, i.e. by means of hardware-side means and software-side means.

[0054] The hardware-side means comprise a data interface in order to exchange data with components participating in the implementation of the method according to the application. Furthermore, the hardware-side means comprise a processor for data processing and a memory for data storage. The software-side means comprise program modules implemented in the control device 6 in order to implement the method according to the application.

Claims

1. Method for operating a transmission (2) of a motor vehicle, wherein, in order to trigger a gear change in the transmission (2), a trigger rotational speed is determined with which the gear change to be carried out is triggered on the control side, depending on a reaction time of the gear change to be carried out, depending on a gradient of a rotational speed of a motor vehicle side and depending on a maximum permissible limit rotational speed for the rotational speed of the motor vehicle side, so that the rotational speed of the motor vehicle side does not exceed the maximum permissible limit rotational speed when carrying out the gear change, characterized in that the trigger rotational speed with which the gear change to be carried out in the transmission (2) is triggered on the control side is adjusted depending on a driver requested torque.

2. Method according to claim 1, characterized in that the trigger rotational speed for the gear change to be carried out is additionally adjusted depending on an actually provided engine actual torque.

3. Method according to claim 2, characterized in that the trigger rotational speed for the gear change to be carried out is adjusted depending on a difference or a ratio between the driver requested torque and the actually provided engine actual torque.

4. Method according to one of claims 1 to 3, characterized in that an offset value with which the trigger rotational speed for the gear change to be carried out is adjusted is determined depending on the driver requested torque.

5. Method according to claim 4, characterized in that the offset value is additionally determined depending on an actually provided engine actual torque.

6. Method according to claim 4, characterized in that the offset value is determined depending on a characteristic curve.

7. Method according to claim 4, characterized in that when the driver requested torque is smaller than a limit value, an offset value is predefined which is the same for all differences or ratios between the driver requested torque and the actually provided engine actual torque.

8. Method according to claim 4, characterized in that when the driver requested torque is greater than a limit value, an offset value is predefined which is greater the greater the difference or the ratio between the driver requested torque and the actually provided engine actual torque.

9. Method according to claim 5, characterized in that the offset value is determined depending on a difference or a ratio between the driver requested torque and the actually provided engine actual torque.

10. Control device (6) for operating a transmission (2) of a motor vehicle, wherein the control device (6), in order to trigger a gear change in the transmission (2), determines a trigger rotational speed depending on a reaction time of the gear change to be carried out, depending on a gradient of a rotational speed of a motor vehicle side and depending on a maximum permissible limit rotational speed for the rotational speed of the motor vehicle side, according to which the gear change to be carried out is triggered on the control side, so that the rotational speed of the motor vehicle side does not exceed the maximum permissible limit rotational speed when carrying out the gear change, characterized in that the control device (6) adjusts the trigger rotational speed with which the gear change to be carried out in the transmission (2) is triggered on the control side depending on a driver requested torque.

11. The control device of claim 10, wherein The control device is configured to implement the method according to any one of claims 1 to 9 on the control side.

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