Method and device for operating a motor vehicle

Abstract

Method for performing a diagnosis of an internal combustion engine (10) of a motor vehicle, wherein during the diagnosis at least partially a further drive machine (20), in particular an electric machine (20), generates a torque and thereby changes an operating point of the internal combustion engine (10), wherein the further drive machine (20) is motor-operable, and the torque supports a rotational movement of the internal combustion engine (10), wherein the diagnosis is performed at least partially in a passive operation of the internal combustion engine (10), wherein during the passive operation - a mechanical coupling (30) of the internal combustion engine to the wheels (50) of the motor vehicle is opened - the additional drive motor (20) drives the internal combustion engine (10), whereby the internal combustion engine (10) is switched to an active mode when the diagnosis is completed.

Description

[0001] The invention relates to a method for operating the drive system of a motor vehicle. In further aspects, the invention relates to a computer program for carrying out this method, an electronic storage medium and a control unit, as well as program code with instructions for generating the computer program. State of the art

[0002] From DE 10 2012 211 024 A1 a method for operating a vehicle is known, comprising specifying a target power requirement for the vehicle to an internal combustion engine over a certain period, wherein the target power requirement over a certain period depends on a diagnosis to be carried out on the internal combustion engine;and wherein an auxiliary unit is connected to the internal combustion engine when the actual power demand of the vehicle to the internal combustion engine deviates from the target power demand, and wherein the actual power demand of the internal combustion engine is estimated on a route to be driven by the vehicle, and wherein the diagnostic procedure to be carried out is planned based on a probability that a difference between the actual power demand and the target power demand can be compensated for by connecting the auxiliary unit to the internal combustion engine, and wherein the diagnostic procedure is prohibited if the probability falls below a predetermined threshold.

[0003] DE 10 2009 028 374 A1 discloses a diagnostic procedure for hybrid vehicles in which the electric motor selectively drives or brakes the combustion engine in order to enable different load points for extended diagnostics, for example for misfire detection or air system testing, also in workshop operation.

[0004] DE 10 2007 043 607 A1 discloses a method for compression testing of an internal combustion engine in which the torque applied by an electric machine in generator or towing operation is analyzed and compared with target values ​​in order to diagnose the condition of the engine during operation. Disclosure of the invention

[0005] The present invention aims to provide a method for diagnosing the internal combustion engine of a motor vehicle with increased practical benefits. This objective is achieved by the features of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0006] According to the invention, it was recognized that such diagnoses can be carried out particularly advantageously during sailing phases of a sailing motor vehicle.

[0007] If, during a procedure for diagnosing the internal combustion engine of a motor vehicle, at least partially another drive motor generates a torque, thus changing an operating point of the internal combustion engine, this has the advantage that the diagnosis can be carried out even if it would otherwise not be possible due to the route topology and / or the driving profile.

[0008] The additional drive unit is, for example, an electric machine, but it can also be, for example, a pneumatic or hydraulic auxiliary unit.

[0009] According to the invention, the additional drive machine is motor-driven, and the torque supports a rotational movement of the internal combustion engine.

[0010] According to the invention, the diagnosis is carried out at least partially in passive operation of the internal combustion engine, wherein during passive operation a mechanical coupling, for example a clutch, of the internal combustion engine to the wheels of the vehicle is open and the other drive motor drives the internal combustion engine. This allows the operating point of the internal combustion engine to be set particularly flexibly.

[0011] In particular, in one embodiment it is possible that the combustion engine is operated in passive mode in such a way that it does not generate a drive torque by burning a fuel / air mixture.

[0012] Such operation is possible, for example, by switching off injection and / or ignition; however, it is also possible for injection and / or ignition to be switched on, as long as no drive torque is generated.

[0013] According to another aspect, it may be provided that the additional drive motor changes the operating point of the combustion engine in such a way that the diagnosis can be carried out.

[0014] According to another aspect, it may be provided that air is supplied to the combustion engine during the diagnosis, for example by opening a throttle valve.

[0015] Alternatively or additionally, it is possible to inject fuel into the combustion engine during the diagnosis.

[0016] In particular, it is also possible that a fuel / air mixture will be ignited in the combustion engine during the diagnosis.

[0017] These measures can support the diagnostic process.

[0018] According to the invention, the internal combustion engine is switched to an active mode when the diagnostic process is complete. This means that a fuel-air mixture is ignited in the internal combustion engine in such a way that a drive torque is generated, in particular that the internal combustion engine runs without support from the other drive motor.

[0019] It can also be provided that the combustion engine is switched to active mode when a driver request to start the combustion engine is detected.

[0020] In particular, it can be provided that, during the transition of the combustion engine to active mode, the driving torque generated by the other drive motor is reduced in such a way that the total torque transmitted to the wheels by the combustion engine and the other drive motor remains constant. This makes switching to active mode particularly convenient.

[0021] In a further aspect, the invention relates to program code together with processing instructions for creating a computer program executable on a control unit, in particular source code with compilation and / or linking instructions, wherein the program code results in the computer program for executing all steps of one of the described methods when it is converted into an executable computer program according to the processing instructions, i.e., in particular compiled and / or linked. This program code can, in particular, be provided by source code which, for example, can be downloaded from a server on the Internet.

[0022] The figures show particularly advantageous embodiments of the invention. They show: Fig. 1. Schematic representation of the structure of a motor vehicle's drivetrain; Fig. 2 a flowchart of an embodiment of the invention. Description of the exemplary implementations

[0023] Fig. Figure 1 schematically shows the drivetrain of a motor vehicle. The internal combustion engine 10 is mechanically coupled to the drive shaft 40, which drives the wheels 50, via the clutch 30. The internal combustion engine 10 and clutch 30 are controlled by the control unit 100. Of course, it is also possible for the internal combustion engine 10 and clutch 30 to be controlled by separate control units.

[0024] In the exemplary embodiment, the further drive machine is provided by an electric machine 20, for example a belt-driven starter-generator.

[0025] Fig.Figure 2 shows a flowchart of a possible embodiment of the invention. In step 1000, the motor vehicle is in a sailing mode, i.e., the clutch 30 is open and the internal combustion engine 10 is switched off or is not generating any driving torque. Initiating a sailing mode is generally known in the prior art and requires no further explanation.

[0026] In the subsequent step 1010, it is checked whether a diagnostic request is pending. If this is not the case, the procedure ends in step 1100.

[0027] The query in step 1010 can also be limited to whether there is a diagnostic request that cannot be postponed or that cannot be carried out at other operating points of the combustion engine 10.

[0028] Otherwise, step 1020 follows, in which the internal combustion engine 10 is driven by the electric machine 20. Depending on the design of the electric machine 20, it may be necessary to engage a disconnect clutch between the electric machine 20 and the internal combustion engine 20, and / or to engage neutral.

[0029] The following step, optionally 1030, involves bringing the combustion engine 10 into an operating point where the diagnosis can be performed. For example, this step might involve accelerating the combustion engine 10 to a predetermined speed, interrupting injections and / or ignitions, or similar actions. The actual diagnosis is then performed in step 1040.

[0030] In optional step 1050, after the diagnosis is complete, the internal combustion engine 10 is brought to a standstill, i.e., the electric machine 20 no longer drives the internal combustion engine 10. However, it is also possible that the internal combustion engine 10 is instead switched to active mode, i.e., the electric machine 20 no longer drives the internal combustion engine 10 on its own, but rather ignition and / or injection ensure the generation of driving torque in the internal combustion engine 10.

[0031] It is also possible that step 1040 includes determining whether the driver has requested to start the combustion engine 10. If so, the combustion engine 10 is also switched to active mode.

[0032] The transition of the combustion engine 10 into active mode can be torque-neutral as described above, possibly with transient transitions. 10 Internal combustion engine 20 Electric Machine 30 Clutch 40 Drive shaft 50 wheels 100 control unit

Claims

Method for performing a diagnosis of an internal combustion engine (10) of a motor vehicle, wherein during the diagnosis at least partially a further drive machine (20), in particular an electric machine (20), generates a torque and thereby changes an operating point of the internal combustion engine (10), wherein the further drive machine (20) is capable of being driven, and the torque supports a rotational movement of the internal combustion engine (10), wherein the diagnosis is performed at least partially in a passive operation of the internal combustion engine (10), wherein during the passive operation - a mechanical coupling (30) of the internal combustion engine to wheels (50) of the motor vehicle is open - the further drive machine (20) drives the internal combustion engine (10), wherein the internal combustion engine (10) is switched to an active mode when the diagnosis is completed. Method according to claim 1, wherein the further drive machine (20) changes the operating point of the internal combustion engine (10) so that the diagnosis can be carried out. Method according to one of claims 1 or 2, wherein air is supplied to the internal combustion engine (10) during the diagnosis. Method according to one of the preceding claims, wherein fuel is injected into the internal combustion engine (10) during the diagnosis. Method according to one of the preceding claims, wherein a fuel / air mixture is ignited in the internal combustion engine (10) during the diagnosis. Method according to any one of claims 1 to 5, wherein the internal combustion engine (10) is switched to active mode (10) when a driver request to start the internal combustion engine (10) is detected. Method according to one of the preceding claims, wherein during the transition of the internal combustion engine (10) into active mode a driving torque generated by the further drive machine (20) is reduced in such a way that a total torque which is transmitted from the internal combustion engine (10) and the further drive machine (20) to the wheels (50) is constant. Computer program that is trained to perform all steps of one of the methods according to any one of claims 1 to 7. Machine-readable storage medium on which the computer program according to claim 8 is stored. Control unit that is configured to perform all steps of one of the methods according to any one of claims 1 to 7. Program code together with processing instructions for creating a computer program executable on a control unit, wherein the program code yields the computer program according to claim 8 when it is converted into an executable computer program in accordance with the processing instructions.

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