Method for operating a drive device for a motor vehicle and corresponding drive device

Abstract

A method for operating a drive device for a motor vehicle. The drive device has an internal combustion engine, an output shaft, and a clutch connected between the internal combustion engine and the output shaft. In a coasting operating mode, an idling speed control of the internal combustion engine to an idling speed is carried out and the clutch is opened, and, in an overrun operating mode, the clutch is closed. When shifting from the coasting operating mode to the overrun operating mode, while, at the same time, carrying out the idling speed control of the internal combustion engine to the idling speed, the clutch is closed, so that an entrainment of the internal combustion engine occurs.

Claims

1. A method for operating a drive device for a motor vehicle, wherein the drive device has an internal combustion engine, an output shaft, and a clutch connected between the internal combustion engine and the output shaft, and wherein, in a coasting operating mode, an idling speed control of the internal combustion engine to an idling speed is carried out and the clutch is opened and, in an overrun operating mode, the clutch is closed, wherein the clutch is closed when shifting from the coasting operating mode to the overrun operating mode, while, at the same time, carrying out the idling speed control of the internal combustion engine to the idling speed, so that an entrainment of the internal combustion engine occurs, and wherein the clutch is adjusted to a predetermined clutch torque that is transmitted between the internal combustion engine and the output shaft.

2. The method according to claim 1, wherein the clutch is only partially closed in a first step.

3. The method according to claim 2, wherein, in a second step, the clutch is completely closed when an internal combustion engine speed corresponds to a transmission speed of a transmission of the drive device.

4. The method according to claim 3, wherein the shifting is terminated as soon as the internal combustion engine speed corresponds to the transmission speed.

5. The method according to claim 1, wherein a fuel injection into the internal combustion engine is reduced with increasing internal combustion engine speed.

6. The method according to claim 5, wherein the fuel injection is suspended when the internal combustion engine speed exceeds a threshold speed of the internal combustion engine.

7. The method according to claim 3, wherein the internal combustion engine threshold speed is chosen to be less than the transmission speed.

8. The method according to claim 1, wherein the shifting from the coasting operating mode to the overrun operating mode occurs when an operating brake of the motor vehicle is actuated.

9. The method according to claim 3, wherein the shifting from the overrun operating mode to an idling operating mode occurs when the transmission speed goes below a transmission threshold speed, wherein the clutch is completely opened in the idling operating mode.

10. A drive device for a motor vehicle, comprising: an internal combustion engine, an output shaft, and a clutch connected between the internal combustion engine and the output shaft, wherein, in a coasting operating mode, an idling speed control of the internal combustion engine to an idling speed is carried out and the clutch is opened, and, in an overrun operating mode, the clutch is closed, wherein the drive device is designed to close the clutch when shifting from the coasting operating mode to the overrun operating mode, while, at the same time, carrying out the idling speed control of the internal combustion engine to the idling speed, so that an entrainment of the internal combustion engine occurs, and wherein the clutch is adjusted to a predetermined clutch torque that is transmitted between the internal combustion engine and the output shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in detail below on the basis of the exemplary embodiments illustrated in the drawing, without any limitation of the invention. Shown are:

(2) FIG. 1 a schematic illustration of a section of a motor vehicle, and

(3) FIG. 2 a diagram in which a clutch pressure is plotted over time.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 shows a schematic illustration of a drive device 1 for a motor vehicle, for example, which, in the embodiment illustrated here, is a hybrid drive device. Accordingly, the drive device 1 has at least two drive assemblies, namely, a first drive assembly 2 and a second drive assembly 3. The first drive assembly 2 is present, for example, in the form of an internal combustion engine, the second drive assembly 3 as an electric motor.

(5) The two drive assemblies 2 and 3 can be operatively connected to each other via a shaft 4 in a rigid and/or permanent manner. However, the shaft 4 can also be associated with a separating clutch, by means of which the operative connection between the drive assemblies 2 and 3 can be interrupted. The second drive assembly 3 or the electric motor is actuated by means of a power electronics unit 5, which is actuated on its side, for example, by use of a control unit.

(6) In addition, the drive device 1 has a clutch 6, in particular a starting clutch, as well as a transmission 7, in particular a shift transmission. The transmission 7 is operatively connected or at least can be operatively connected to the internal combustion engine 2 via the clutch 6. It is noted that the illustration chosen here is purely by way of example. The transmission 7 can be designed as a manual transmission, an automatic transmission, or as an automated manual transmission, in particular as a multiple clutch transmission, such as, for example, a dual clutch transmission. In particular, in the case of the automatic transmission or the automated manual transmission, the clutch 6 can be a component of the transmission 7.

(7) Further illustrated is an axle 8, which, in the exemplary embodiment illustrated here, is associated with two wheels 9. The axle 8 or the wheels 9 are preferably operatively connected, in particular rigidly and/or permanently, connected to the transmission 7 via an axle differential gearbox 10. Accordingly, the axle 8 or the wheels 9 can be driven by means of the internal combustion engine 2 and/or the electric motor 3. The drive device 1, together with the axle 8, the wheels 9, and the axle differential gearbox 10, can form a drive train 11 for the motor vehicle.

(8) The drive device 1 can then be operated at least in a coasting operating mode and in an overrun operating mode. In the coasting operating mode, an idling speed control of the internal combustion engine 2 to an idling speed is carried out. At the same time, the clutch 6 is opened. In an overrun operating mode, in contrast, the clutch 6 is closed, in particular completely closed, so that, via the clutch 6 and the transmission 7, a drive torque of the internal combustion engine 2 directed at deceleration of the motor vehicle can be applied to the axle 8 or the wheels 9.

(9) If the coasting operating mode is then to be switched to the overrun operating mode, the clutch 6 is closed, while, at the same time, the idling speed control of the internal combustion engine 2 is carried out. The closing of the clutch 6 results in an entrainment of the internal combustion engine 2. Because the idling speed control attempts to keep the internal combustion engine speed of the internal combustion engine 2 at the idling speed, it will reduce the amount of fuel per unit of time, which serves as the adjusted variable, and is fed to the internal combustion engine 2, with increasing internal combustion engine speed. Consequently, a marked fuel savings results from this procedure.

(10) FIG. 2 shows a diagram in which a clutch pressure p of the shifting clutch 6 is plotted over the time t. For t<t.sub.0, the drive device is in its coasting operating mode. From the point in time t=t.sub.0 on, the shifting from the coasting operating mode to the overrun operating mode occurs, with the latter operating mode being present for t>t.sub.1. The shifting is terminated at the point in time t=t.sub.1, with the overrun operating mode following immediately. The clutch pressure p behaves analogously to a clutch torque, that is, to the maximum torque that can be transmitted via the clutch 6.

(11) It is clear that the clutch pressure for t<t.sub.0 is lowfor example, zero. During shifting, that is, in the period of time t.sub.0tt.sub.1, the clutch pressure p rises steadily. No jump in the clutch pressure p therefore occurs, as would be the case for an abrupt coupling by means of the clutch 6. Such an abrupt coupling could be carried out when the internal combustion engine 2 is brought from its own power to a transmission speed present at the transmission 7. In contrast to this, an entrainment of the internal combustion engine 2 is provided in order to reduce markedly the fuel consumption during shifting from the coasting operating mode to the overrun operating mode.