EP3482107A1

EP3482107A1 - Method for operating a motor vehicle, and transmission control unit

Info

Publication number: EP3482107A1
Application number: EP17728544.2A
Authority: EP
Inventors: Reinhard Vollmar
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2016-07-08
Filing date: 2017-06-08
Publication date: 2019-05-15
Also published as: DE102016212522A1; US10723343B2; WO2018007088A1; CN109416120A; US20190299965A1

Abstract

A method for operating a motor vehicle having a drive assembly (1), having a transmission (2) and having a drive output (3), wherein the transmission (2) is formed as an automatic shift transmission, is connected between the drive output (3) and the drive assembly (1), and has multiple shift elements (4), wherein, to execute a gear change in the transmission (2), at least one previously closed shift element (4) is opened, and at least one previously open shift element (4) is closed. When, proceeding from overrun operation of the motor vehicle, a downshift from a current gear to a target gear is executed in the transmission (2), a braking torque is applied to the drive output (3) by means of a vehicle brake (5), which braking torque is dependent on the overrun torque prevailing at the drive output (3) before the execution of the downshift.

Description

Method for operating a motor vehicle and transmission control unit

The invention relates to a method for operating a motor vehicle. Furthermore, the invention relates to a transmission control unit.

Motor vehicles with a drive unit, an output and a switched between the drive unit and the output gearbox are well known in practice. The operation of the drive unit is controlled and / or regulated by an engine control unit. The operation of the transmission is controlled and / or regulated by a transmission control unit.

A trained as a manual transmission has several switching elements. The switching elements may be frictional switching elements, such as clutches and brakes, as well as form-locking switching elements, such as claws, act. To execute a shift or a gear change in a manual transmission at least one previously closed switching element is opened and closed at least one previously opened switching element to convert the gear from an actual gear in a target gear to perform the circuit or the gear change. In particular, when a form-fitting switching element is involved in the execution of a circuit as to be closed and thus zuzuschaltendes switching element, the same must be synchronized to close, via an engagement of the drive unit. Only after appropriate synchronization can then be closed to be closed switching element. It can then be transmitted from the transmission no moment. In particular, when starting from a coasting operation of the motor vehicle to perform a downshift, the elimination of the thrust torque at the output by the driver is perceived as unpleasant, since the braking effect of the drive unit is omitted during the circuit. Then, when in a downhill driving the driver deliberately, for example, in a jogging causes a downshift, the elimination of the drive unit side thrust torque at the output is felt to be particularly disadvantageous. The same applies to hybrid vehicles in which in overrun the thrust torque used for recuperation is relatively high. There is therefore a need for a method for operating a motor vehicle and at a transmission control unit, by means of which, starting from a coasting operation of the motor vehicle downshifts can be made more comfortable. On this basis, the present invention seeks to provide a corresponding method for operating a motor vehicle and a transmission control unit for carrying out the method.

This object is achieved by a method according to claim 1. With the invention, when starting from a coasting operation of the motor vehicle in the transmission a downshift from an actual gear is executed in a target gear, applied via the vehicle brake of the motor vehicle at the output a braking torque. This braking torque applied by the vehicle brake is dependent on the thrust torque applied to the output prior to the execution of the circuit.

With the invention, it can be avoided that, when a downshift is executed, starting from a pushing operation at the output, no braking effect is available any more. The intervention via the vehicle brake thus compensates for the omission of the drive unit-side thrust torque at the output.

According to a development of the invention brings in execution of the downshift, the vehicle brake on the output to a braking torque, which is also dependent on an applied after execution of the downshift in the target gear at the output thrust torque. Hereby, the engagement of the vehicle brake on the output via the braking torque can be made particularly advantageous.

According to one variant, the vehicle brake on the output brings a braking torque, which simulates a thrust torque curve of a non-shear-force downshift on execution of the shear force interrupted downshift on the output. According to this variant of the invention, a torque curve is simulated via the brake on the output, which corresponds to the shear torque curve of a non-thrust-interrupted downshift. According to a further variant, the vehicle brake at the output brings a braking torque, which ramps and thus runs continuously and steadily between the applied before the execution of the downshift in the actual gear on the output thrust torque and after applying the downshift in the target gear at the output thrust torque. This variant of the invention is particularly preferred in order to provide a braking torque at the output via the vehicle brake.

When performing the downshift either a positive switching element is closed and this synchronized via a drive unit engagement or it is a frictional switching element closed and synchronized for this purpose before closing via a drive unit engagement.

The invention can be used both when the switching element to be closed is a form-fitting switching element and when the switching element to be closed is a frictional-type switching element. Then, when it is the closing element to be closed by a frictional switching element, the invention is then used when the frictional engagement element to be closed is closed only after synchronization.

The transmission control unit according to the invention is defined in claim 7.

Preferred developments emerge from the subclaims and the following description. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

1 shows a first drive train diagram of a motor vehicle;

Fig. 2 is a diagram for illustrating the method for operating a

Motor vehicle.

The invention relates to a method for operating a motor vehicle and a transmission control unit. 1 shows a drive train diagram of a motor vehicle, which comprises a drive unit 1, a transmission 2 and an output 3. The transmission 2 is designed as an automatic transmission and includes switching elements 4, wherein FIG. 1 shows an example of such a switching element 4. The transmission 2 is connected between the drive unit 1 and the output 3 and converts speeds and torques and provides the traction power supply of the drive unit 1 at the output 3 ready. Furthermore, FIG. 5 shows a motor vehicle brake, via which a braking torque can be applied to the output 3. The operation of the transmission 2 is controlled and / or regulated by a transmission control device 6, for which purpose the transmission control device 6 exchanges data with the transmission 2. The operation of the drive unit 1 is controlled and / or regulated by an engine control unit 7, for which purpose the engine control unit 7 exchanges data with the drive unit 1. Furthermore, the transmission control device 6 and the motor control device 7 exchange data with each other.

Then, when a gear is engaged in the gearbox 2 designed as a transmission, a first defined number of switching elements 4 is closed and a second defined number of switching elements 4 is opened. To perform a gear change and thus a circuit in the transmission 2, at least one previously closed switching element 4 is opened and at least one previously closed switching element 4 is closed. Upshifts and downshifts can be performed as circuits, both starting from a coasting operation of the motor vehicle and starting from a train operation thereof. The present invention relates to details of a method for operating a motor vehicle, in which, starting from a pushing operation of the motor vehicle in the transmission 2, a downshift from an actual gear is executed in a target gear, said to be closed and thus zuzuschaltende switching element of the transmission. 2 is closed only after completion of the synchronization, so that therefore during the actual circuit execution of the transmission 2 no thrust torque of the drive unit 1 can be transmitted in the direction of the output 3, that accordingly no drive-unit side thrust torque is present in the output 3. With the invention, when starting from an overrun operation of the motor vehicle in the transmission 2, a downshift from an actual gear to a target gear is executed, in which the circuit element to be closed switching element 4 is closed only after synchronization, via the vehicle brake 5 applied to the output 3 a braking torque, which depends on the thrust torque applied to the output 3 prior to execution of the downshift.

Accordingly, a thrust torque of the drive unit 1 is at least partially compensated for via the service brake 5 of the motor vehicle in order to provide a corresponding braking effect on the output 3, even when the transmission 2 can not transmit thrust torque in the direction of the output 3 when the downshift is executed.

The applied during the downshift of the vehicle brake 5 on the output 3 braking torque is preferably both of the applied prior to execution of the downshift in the actual gear on the output 3 thrust torque and in addition from the after-execution of the downshift on the output 3 in the target gear thrust torque dependent.

Further details of the invention will be described with reference to FIG. 2, wherein in FIG. 2 over the time t several curves are shown. Curve 8 visualizes a circuit request. The curve 9 visualizes the voltage applied to the output 3 moment. The curve 10 visualizes a torque curve of the drive unit. 1 The curve 1 1 visualizes the activation of a switching element 4 to be closed for the gear change. The curve 12 visualizes the activation of a switching element 4 to be opened for the execution of the shift. The curve 13 visualizes the brake engagement via the vehicle brake 5.

In Fig. 2, an actual gear is engaged before the time tO in the transmission 2, wherein the motor vehicle is operated in overrun mode. Accordingly, before the time t0, a thrust torque is applied to the output 3 in accordance with the curve 9. At the time t0, a control-side request for a shift or a gear change takes place in accordance with the signal course 8, wherein the switching element 4 to be opened from the actual gear to the target gear is opened starting at the time t0. According to the course of the curve 12, the pressure control is initially reduced stepwise and then ramped between the times t0 and t1 at the time t0 for this switching element 4 to be opened.

Beginning with the time t1 takes place according to the curve 10 via a corresponding engagement of the drive unit 1 is a synchronization of the circuit to be executed for the circuit to be closed switching element 4. This switching element 4 is in particular a positive switching element such as a claw. Since the switching element 4 to be synchronized for the circuit to be executed is completely open during synchronization and no torque can transmit in the direction of the output 3, according to the invention a corresponding control of the service brake 5 takes place via the service brake 5 on the output 3 Apply braking torque. Starting at the time t1, the braking torque provided by the vehicle brake 5 at the output is initially ramped up to the time t2, it remains constant between the times t2 and t3 and again ramps between the times t3 and t4 after the synchronization of the switching element 4 to be closed reduced.

Accordingly, between the times t1 and t3, the synchronization of the switching element 4 to be closed for the execution of the circuit takes place, this synchronization being completed at time t3, so that the switching element 4 to be closed is actually closed at time t3 in accordance with curve 1 1.

In the execution of the downshift in the transmission 2, therefore, a braking torque is applied by the vehicle brake 5 on the output 3. This braking torque is at least of the prior to the execution of the downshift in the actual gear on the output 3 thrust torque and preferably also depends on the applied after execution of the downshift in the target gear at the output 3 thrust torque. In solid lines of Fig. 2, the curve 9 shows a torque prevailing at the output 3, which simulated by a corresponding engagement of the service brake 5 by providing a braking torque at the output 3 in execution of the shear force interrupted downshift on the output 3 a thrust torque curve corresponding to a non-thrust interrupted downshift how it would set in conventional use of a frictional, zuzuschaltenden switching element. In contrast, in dashed lines Fig. 2 shows a curve 9 ', which is characterized in that the vehicle brake 5 at the output 3 such a braking torque applies that the output torque ramp-like and thus continuously and steadily between before the execution of the downshift in the actual gear at the output 3 adjacent thrust torque and after applying the downshift in the target gear at the output 3 thrust torque runs.

About the intervention of the vehicle brake or service brake 5 is therefore applied to the output 3 torque during the circuit execution of the voltage applied before the execution of the downshift in the actual gear on the output 3 thrust moment on after running the downshift in the target gear on the output 3 in the future Shear moment defined. The thrust torque present in the target gear at the output 3 in the future can be calculated as a function of the thrust torque present in the actual gear on the output 3 and the gear ratios of the actual gear and the target gear.

Particularly preferably, the invention finds use when a form-fitting switching element is to be synchronized in advance in the execution of the circuit or the gear change in the transmission 2 as switching or to be closed switching element 4.

However, the invention can also be used when the switching element 4 to be closed or closed is a frictional switching element which is actually closed only after synchronization has taken place. With the invention, a torque curve or a braking torque can be provided via a corresponding engagement of the Bet ebsbremse 5 at the output, which compensates or simulates the thrust torque of the drive unit 1, which can not be further transmitted from the transmission 2 to the output 3. As a result, the comfort of the circuit design can be increased.

Particularly advantageously, the invention can also be used in motor vehicles, the drive unit 1 is designed as a hybrid drive, the drive unit 1 so on the one hand comprises an internal combustion engine and on the other hand, an electric machine.

In such hybrid vehicles, recuperation takes place in coasting mode, as a result of which the thrust torque applied to the output 3 before the downshift in overrun mode is typically relatively high. Therefore, the elimination of the thrust torque at the output 3 would make particularly noticeable. Here, by appropriate engagement, the service brake 5 at the output 3 a braking torque can be provided, which at least partially compensates for the omission of the drive unit side thrust torque at the output 3.

The invention further relates to a transmission control unit 6 for carrying out the method. The transmission control unit 6 controls in circuit design, the switching elements 4 of the transmission 2, namely the involved in the execution of the circuit switching elements for closing or opening. When, starting from a coasting operation of the motor vehicle in the transmission 2, a downshift from an actual gear to a target gear is executed, which requires a synchronization of the zuzuschaltenden or to be closed switching element 4 before it can be closed, is from the transmission control unit. 6 the vehicle brake 5 is controlled, in such a way that the vehicle brake 5 at the output 3 applies a braking torque, which at least of the applied before performing the downshift at the output 3 thrust torque and preferably also after the execution of the downshift in the target gear on the output. 3 adjacent thrust torque is dependent. To carry out the method, the transmission control unit 6 has corresponding means, these being hardware-side means and software-side means. The hardware-side means are data interfaces in order to exchange data with the modules involved in the execution of the method according to the invention, for example with the vehicle brake 5. Further, these hardware resources are a processor for data processing and a memory for data storage. The software-side means include program blocks for carrying out the method according to the invention.

reference numeral

power unit

transmission

output

switching element

vehicle brake

Transmission Control Module

Engine control unit

Curve Circuit Request

Curve course Moment at the output

Curve curve momentum drive unit

Curve control Control to be closed switching element

Curve control Control to open switching element

Curve course braking intervention

Claims

claims

1 . Method for operating a motor vehicle with a drive unit (1), with a transmission (2) and with an output (3), wherein the transmission (2) is designed as an automatic transmission, between the output (3) and the drive unit (1) is connected and has a plurality of switching elements (4), wherein the execution of a gear change in the transmission (2) at least one previously closed switching element (4) is opened and at least one previously opened switching element (4) is closed, characterized in that when starting from a deceleration of the motor vehicle in the transmission (2) a downshift from an actual gear is executed in a target gear, via a vehicle brake (5) on the output (3) a braking torque is applied, which of the before execution of the downshift on the output ( 3) applied thrust torque is dependent.

2. The method according to claim 1, characterized in that when performing the downshift, the vehicle brake (5) at the output (3) applies a braking torque, which is also dependent on a after execution of the downshift in the target gear on the output (3) thrust torque ,

3. The method according to claim 1 or 2, characterized in that the vehicle brake (5) at the output (3) applies a braking torque, which simulates a Schubmomentverlauf a not shear force interrupted downshift on execution of the shear force interrupted downshift on the output (3).

4. The method according to claim 1 or 2, characterized in that the vehicle brake (5) at the output (3) applies a braking torque, which ramps between that of the prior to execution of the downshift on the output (3) applied thrust moment and after execution of the downshift in the target gear on the output (3) applied thrust torque runs.

5. The method according to any one of claims 1 to 4, characterized in that when executing the downshift a positive switching element is closed and synchronized thereto via a drive unit engagement.

6. The method according to any one of claims 1 to 4, characterized in that when executing the downshift a frictional switching element is closed and synchronized for this purpose before closing via a drive unit engagement.

7. Transmission control unit (6) for operating a transmission designed as an automatic transmission of a motor vehicle, wherein the transmission control unit for executing a gear change at least one previously closed switching element (4) for opening and at least one previously opened switching element (4) to close, characterized that the transmission control unit, when starting from a pushing operation of the motor vehicle in the transmission (2) a downshift from an actual gear is executed in a target gear, a vehicle brake (5) such that the vehicle brake (5) at the output (3 ) applies a braking torque, which is dependent on the thrust torque applied before the execution of the downshift on the output (3).

8. Transmission control device according to claim 7, the same performs the method according to one of claims 1 to 6 control side.