Method for operating a hybrid drive apparatus for a motor vehicle as well as a corresponding hybrid drive apparatus

Abstract

A method for operating a hybrid drive apparatus for a motor vehicle, having an exhaust-gas-producing internal combustion engine and an electric motor. The internal combustion engine and the electric motor, respectively alone or at least sometimes jointly, provide a drive torque, wherein, when a start threshold value is exceeded by a demand variable. The internal combustion engine is started and the drive torque is at least partially generated by the internal combustion engine, and, when a stop threshold value is not met by the demand variable, the internal combustion engine is stopped and the drive torque is generated solely by means of the electric motor.

Claims

1. A method for operating a hybrid drive apparatus for a motor vehicle, having an exhaust-gas-producing internal combustion engine and an electric motor, wherein the internal combustion engine and the electric motor, respectively alone or at least sometimes jointly, provide a drive torque, comprising: when a start threshold value is exceeded by a demand variable, the internal combustion engine is started and the drive torque is at least partially generated by the internal combustion engine, and when a stop threshold value is not met by the demand variable, the internal combustion engine is stopped and the drive torque is generated solely by the electric motor, wherein the hybrid drive apparatus has a particulate filter for filtering the exhaust gas of the internal combustion engine, wherein the start threshold value and/or the stop threshold value are variably selected to reduce soot generation within the internal combustion engine as a function of an operating variable describing a temperature of the internal combustion engine, and wherein, when a first setpoint is not reached by the operating variable, the start threshold value is reduced by a first start threshold differential value, starting from a start threshold output value, and/or when the first setpoint is not reached by the operating variable, the stop threshold value is reduced by a first stop threshold differential value, starting from a stop threshold output value.

2. The method according to claim 1, wherein an output of the hybrid drive apparatus, a rotational speed of the hybrid drive apparatus, a torque of the hybrid drive apparatus, and/or a speed of the motor vehicle are used as the demand variable.

3. The method according to claim 1, wherein a coolant temperature, a lubricant temperature, a cylinder wall temperature, a piston temperature, and/or a fresh gas throughput of the internal combustion engine are used as the operating variable.

4. The method according to claim 1, wherein the selection of the start threshold value and/or of the stop threshold value takes place continuously or discreetly.

5. The method according to claim 1, wherein the start threshold value and/or the stop threshold value is determined, with continuous selection, by a mathematical function which has the operating variable as the input variable.

6. The method according to claim 1, wherein when a second setpoint is not reached by the operating variable, the start threshold value is reduced by a second start threshold differential value, starting from the start threshold output value, and/or when the second setpoint is not reached by the operating variable, the stop threshold value is reduced by a second stop threshold differential value, starting from a stop threshold output value.

7. The method according to claim 6, wherein when the first setpoint and/or the second setpoint is not reached by the operating variable, the start threshold value and/or the stop threshold value are selected such that the drive torque is generated solely by the internal combustion engine.

8. The method according to claim 1, wherein a gasoline internal combustion engine is used as the internal combustion engine.

9. A hybrid drive apparatus for a motor vehicle, comprising: an exhaust-gas-producing internal combustion engine and an electric motor, wherein the internal combustion engine and the electric motor, respectively alone or at least sometimes jointly, provide a drive torque, wherein the hybrid drive apparatus is formed to start the internal combustion engine when a start threshold value is exceeded by a demand variable and to at least partially generate the drive torque by the internal combustion engine and to stop the internal combustion engine when a stop threshold value is not met by the demand variable and to generate the drive torque solely by the electric motor, wherein the hybrid drive apparatus has a particulate filter for filtering the exhaust gas of the internal combustion engine, wherein the hybrid drive apparatus is further formed to variably select the start threshold value and/or the stop threshold value in order to reduce soot generation within the internal combustion engine as a function of an operating variable describing a temperature of the internal combustion engine, and wherein, when a first setpoint is not reached by the operating variable, the start threshold value is reduced by a first start threshold differential value, starting from a start threshold output value, and/or when the first setpoint is not reached by the operating variable, the stop threshold value is reduced by a first stop threshold differential value, starting from a stop threshold output value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail in the following by means of exemplary embodiments, without limiting the invention. In doing so, the only

(2) FIGURE shows a diagram, in which curves for a speed of a motor vehicle as well as an output of a hybrid drive apparatus are entered over time as examples.

DETAILED DESCRIPTION

(3) The FIGURE shows a diagram in which a curve 1 and a curve 2 are shown over time t purely schematically and as an example. Curve 1 in this case describes an output of a hybrid drive apparatus and curve 2 describes the speed of a motor vehicle, which is driven by means of the hybrid drive apparatus. The hybrid drive apparatus has an internal combustion engine and an electric motor, which respectively alone or at least sometimes jointly provide a drive torque of the hybrid drive apparatus for driving the motor vehicle.

(4) The internal combustion engine is at least sometimes switched off and/or stopped during hybrid operation of the hybrid drive apparatus. In particular, it is provided to start the internal combustion engine and to generate at least a portion of the drive torque by means of the internal combustion engine when a demand variable is greater than a start threshold value or exceeds it. In the reverse, if the demand variable is less than a stop threshold value or fails to reach it, the internal combustion engine is stopped and the drive torque is generated solely by means of the electric motor.

(5) In order to keep soot development within the engine as low as possible when starting the internal combustion engine, the start threshold value and/or the stop threshold value are variably selected as a function of an operating variable, wherein said operating variable describes a temperature of the internal combustion engine. The selection of the start threshold value and/or of the stop threshold value may take place continuously. In the exemplary embodiment shown here, discrete selection is implemented. To this end, a first setpoint u.sub.1, a second setpoint u.sub.2, and a third setpoint u.sub.3 are provided, which are present at different points in time t.sub.1, t.sub.2, and t.sub.3.

(6) In the exemplary embodiment shown here, the driving speed of the motor vehicle is used as the operating variable; accordingly, setpoints u.sub.1, u.sub.2, and u.sub.3 likewise describe driving speeds. If the operating variable, that is the driving speed, fails to reach the first setpoint u.sub.1, the start threshold value is reduced by a first start threshold differential value, starting from a start threshold output value. In addition or as an alternative, the stop threshold value is reduced by a first stop threshold differential value, starting from a stop threshold output value.

(7) If the operating variable fails to meet the second setpoint u.sub.2, the start threshold value is reduced by a second start threshold differential value, starting from the start threshold output value, and/or the stop threshold value is reduced by a second stop threshold differential value, starting from the stop threshold output value. In addition, it may be provided that when the third setpoint u.sub.3 is not met by the operating variable, the start threshold value is reduced by a third start threshold differential value, starting from the start threshold output value, and/or the stop threshold value is reduced by a third stop threshold differential value, starting from the stop threshold output value.

(8) In this case, the third start threshold differential value is less than the second start threshold differential value, which, in turn, is less than the first start threshold differential value. In addition or as an alternative, the third stop threshold differential value is less than the second stop threshold differential value, which, in turn, is less than the first stop threshold differential value. Finally, this means that the start threshold value and/or the stop threshold value are selected to be lower, the lower the operating variable and/or its value. In this manner, the soot development within the engine can be significantly reduced, because the internal combustion engine is started more frequently and/or remains in operation longer after a start.