Method for controlling a hybrid powertrain

Abstract

The invention relates to a method for controlling a hybrid powertrain (1) comprising a first partial powertrain (2) having an internal combustion engine (4) with a crankshaft (6) and a first device (8) for detecting a rotational characteristic value of the crankshaft (6) in order to control the internal combustion engine (4), and comprising a second partial powertrain (3) which is separated from the first partial powertrain by a torsional elastic body (7) for torsional oscillation isolation from torsional oscillations of the internal combustion engine (4), the second partial powertrain having an electric machine (9) with a rotor (10) and a second device (11) for detecting a rotational characteristic value of the rotor (10) in order to control the electric machine (9). In order to protect the torsional elastic body (7) and the remainder of the hybrid powertrain (1) from rotational oscillations of the internal combustion engine (4), a quality indicator related to the efficiency, the comfort and / or the damage of the torsional elastic body (7) is determined by means of an analysis of the rotational characteristic values of both devices (8, 11), and the electric machine (9) is controlled in order to optimize the quality indicator.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for controlling a hybrid powertrain having a first powertrain section and a second powertrain section, the first powertrain section having an internal combustion engine with a crankshaft and a first device for detecting a rotational characteristic value of the crankshaft for controlling the internal combustion engine, the second powertrain section being separated from the first powertrain section by a torsional elastic body for torsional oscillation isolation from torsional oscillations from the internal combustion engine, the second powertrain section having an electric machine with a rotor and a second device for detecting a rotational characteristic value of the rotor for controlling the electric machine. BACKGROUND

[0002] Hybrid powertrains with an internal combustion engine and an electric machine that are subject to torsional oscillations are sufficiently known from the prior art. For torsional oscillation isolation of the torsional oscillations, a torsional elastic body, for example a torsional oscillation damper, can be arranged between the internal combustion engine and the electric machine. In addition, the internal combustion engine can misfire, which puts stress on components of the hybrid powertrain and can lead to an increase in the torsional elasticity.

[0003] From WO 2012 / 025434 A2 a hybrid powertrain is known in which an internal combustion engine is connected to a generator in a torsionally rigid manner. In this case, a misfire of the internal combustion engine is identified by evaluating a current and / or voltage curve at the output of the generator.

[0004] DE 102 27 528 A1 discloses a hybrid powertrain having an internal combustion engine and an electric machine, which is connected to the internal combustion engine in a torsionally rigid manner by means of a friction clutch, in which hybrid powertrain interruptions and rough running of the internal combustion engine are detected by means of a rotary encoder of the electric machine.

[0005] From WO 2008 / 080378 A1 a non-hybrid powertrain of a motor vehicle is known, which has an internal combustion engine and a torsional oscillation damper connected to the crankshaft, in which non-hybrid powertrain a faulty engine torque, for example due to a combustion interruption, is identified and the internal combustion engine is controlled to compensate for the fault. SUMMARY

[0006] It is an object of the present invention to propose a method for improving the quality of transmission of drive torques of a hybrid powertrain. In particular, it is an object of the present invention to propose a method for improving comfort, efficiency and reducing damage to the hybrid powertrain.

[0007] This object is achieved by the subject matter of claim 1. The claims dependent on claim 1 represent advantageous embodiments of the subject matter of claim 1. This object is achieved by the subject matter of claim 1. The claims dependent on claim 1 represent advantageous embodiments of the subject matter of claim 1.

[0008] The proposed method serves to determine and eliminate rotational irregularities caused, for example, by misfires, interruptions and the like in an internal combustion engine of a hybrid powertrain that is subject to torsional oscillations. The hybrid powertrain comprises a first partial powertrain having an internal combustion engine and a first device for detecting a rotational characteristic value of the first partial powertrain for controlling the internal combustion engine.

[0009] The second partial powertrain comprises an electric machine and a second device for detecting a rotational characteristic value of the rotor for controlling the electric machine.

[0010] The two partial powertrains are connected to one another by means of a torsional elastic body for damping torsional oscillations of the internal combustion engine. The torsional elastic body can be designed as a torsional oscillation damper. The torsional elastic body is, for example, in the form of a spring device acting in the circumferential direction, for example, arc springs arranged and distributed on the circumference, and the first partial powertrain can thus be assigned to a primary flywheel mass and the second partial powertrain can be assigned to a secondary flywheel mass, for example, a rotor mass, and / or the like, in order to achieve a double-mass flywheel effect. At least one of the two partial powertrains, in particular the second partial powertrain, can be assigned a centrifugal pendulum for a speed-adaptive torsional vibration absorption.

[0011] In order to be able to reliably and quickly, if possible in real time, identify and eliminate losses in comfort, losses in efficiency and / or damage to the torsional elastic body and the rest of the hybrid powertrain caused, for example, by misfires and other irregularities such as interruptions in the internal combustion engine, these losses and damage are measured by comparing the rotational characteristic values determined by the two devices.

[0012] By evaluating, for example, the signals of the two devices about the time offset of the rotational characteristic values of the two devices and their changes, i.e., the changes in the rotational characteristic values of the internal combustion engine and the electric machine, it can be identified which torque acts on which mass of the partial powertrain. For example, it can be evaluated whether torque fluctuations are caused by the internal combustion engine or by the output of the hybrid powertrain.

[0013] A comparison of these curves, for example, with target values based on the control of the internal combustion engine, or with actual values of previous and subsequent working strokes of the cylinders of the internal combustion engine, can provide important signals for misfires or interruptions in real time.

[0014] For example, the comparison can be made on the basis of a change in the rotational characteristic value due to at least two ignition processes in different cylinders directly succeeding one another. For example, three ignition processes can be detected in succession in a sliding manner, and the average ignition process can be compared with the preceding and subsequent ignition processes in order to detect misfires in the event of a significant deviation. Alternatively, the ignition curves of the same cylinder can be compared with one another in succession with a short time delay in order to be able to detect cylinder-specific misfires in an improved manner in the event of a significant change in the ignition curve.

[0015] Alternatively or additionally, a comparison can be made with a change in the rotational characteristic value due to an ignition curve of at least one cylinder and a stored ignition curve for the at least one cylinder. Such an ignition curve can be continuously adjusted and evaluated in dependence on the control of the internal combustion engine, for example in dependence on control variables of the internal combustion engine such as throttle valve position, valve setting, etc.

[0016] Alternatively or additionally, a comparison can be made on the basis of a change in the torsional angle of the two partial drive trains in the event of unchanged control intervention of the internal combustion engine. If there is no control intervention on the changing torque, the change in the torsional angle at the torsional elastic body can be assumed to be attributable to a misfire.

[0017] For example, a state estimator can be used to detect and determine the change in the rotational characteristic value.

[0018] The rotational characteristic value can be detected by the device, for example, as a speed, rotational speed, rotational acceleration and / or rotational angle. From these detected rotational characteristic values, the present kinetic and / or potential energy, the transmitted torque and / or speed and / or rotational acceleration can be determined in the two partial drive trains and / or in the torsional elastic body with further system-inherent variables such as effective lever, transmission ratio, mass, etc.

[0019] A sensor device can be used to detect and determine the rotational characteristic value of the second partial drive train for controlling the electrically commutated electric machine.

[0020] For example, a rotational encoder for the crankshaft can be used as the first device. To this end, a sensor ring can be provided on the torsional elastic body, for example the torsional oscillation damper, the increments of which are detected by fixed sensors. One or more Hall sensors for detecting the increments of the rotor for the electrical commutation of the electric machine or one of the sensor devices arranged at another location can be used as the second device. Alternatively, a state observer can be used as the second device, which determines the rotational characteristic value of the rotor and thus of the second partial drive train without a sensor by means of electrical variables induced in the stator of the electric machine, such as induced current, induced voltage, etc., and thus controls the electric machine.

[0021] In contrast to methods known in the prior art, the destructive or damaging torsional oscillations are eliminated by means of the electric machine. In this case, an efficiency, a comfort and / or a damage-related quality indicator of the torsional elastic body is determined by analyzing the rotational eigenvalues of the two devices, and the electric machine is controlled in order to optimize the quality indicator. The speed of the hybrid powertrain can be influenced by the controlled intervention of the electric machine, so that the quality of the torque transmission, for example the efficiency, the comfort or the damage that can be caused over a longer period of time, is kept within the resonance range of the torsional elastic body.

[0022] For example, the vibration amplitude can be determined by means of the device, and the vibration amplitude can be reduced by controlling the electric machine. For example, vibration energy can be extracted from the torsional elastic body by means of a corresponding control of the electric machine, for example by exerting a predetermined rotational irregularity on the electric machine. The targeted exertion of the rotational irregularity at a predetermined frequency and a corresponding phase angle of the electric machine can effectively avoid or counteract the influence of a strong input of rotational irregularities, for example due to an impact caused by a misfire of the internal combustion engine.

[0023] For example, an existing resonance of the torsional elastic body can be determined by means of the device, and this resonance can be eliminated by means of a control of the electric machine. For example, the current speed can be changed by means of an intervention in the electric machine, so that the resonance critical speed range of the torsional elastic body is preserved if the current speed can be changed. If this cannot be changed, the occurring resonance frequency can be modified by controlling the electric machine, for example by effectively simulating a mass change or a mass moment of inertia change of the effective mass, for example the primary centrifugal mass and / or the secondary centrifugal mass of the torsional elastic body. For example, vibration energy can be extracted from the vibration system of the torsional elastic body by means of an intervention in the electric machine, in particular when the vibration amplitude present at the torsional elastic body has reached a critical level and the energy should be extracted from the torsional elastic body immediately.

[0024] For example, the quality indicator can be determined from the relative torsional angle, the relative torsional speed and / or the relative acceleration between the input part and the output part of the torsional elastic body.

[0025] For example, the electric machine can be actuated by means of a control unit for controlling the internal combustion engine or a higher-level vehicle control unit or the like after the quality indicator has been determined. For example, the determined quality indicator can be interpreted as a cause of a misfire, and the control unit detecting the quality indicator can transmit a misfire signal to another control unit, such as a control device, for example a control device of the internal combustion engine. For example, a control unit different from the control unit of the electric machine can detect the misfire and control the actuation of the electric machine, for example the extraction of vibration energy from the vibration system. For example, the electric machine can be directly controlled in accordance with the quality indicator determined by the device. This means that the electric machine is controlled by a control unit that detects and evaluates the rotational eigenvalues of the device.

[0026] The electric machine can be controlled to minimize the difference of the rotational characteristic values of the device. For example, a minimization of the amplitude between the peaks of the detected signals of the device, for example the difference angle, over time can be provided. For example, the electric machine can be controlled to minimize the rotational characteristic values to a predefined or predeterminable value close to zero.

[0027] For example, the electric machine can be controlled such that a predetermined value of the rotational characteristic value is not exceeded within the stop of the torsional elastic body. This means that, in particular in the case of a multi-stage adjustment, a maximum limit of the torsional angle of the torsional elastic body is adjusted before the stop is reached. If the stop cannot be avoided due to the present vibration energy, the electric machine can be controlled such that the stop is reached with a minimum torsional speed.

[0028] For example, in the case of a rigid connection between the electric machine and the drive wheel and in the case that a decoupling clutch is arranged between the electric machine and the drive wheel, it can be advantageous if the decoupling clutch is at least partially opened when the electric machine is controlled due to a mass loss, i.e. a value that exceeds a predetermined mass indicator. In this case, the remaining hybrid powertrain can be completely decoupled, for example, from the downstream transmission, differential and drive wheels or can only have a slip. BRIEF DESCRIPTION OF DRAWINGS

[0029] The application is explained in more detail with reference to the exemplary embodiments in the individual figures.

[0030] Figure 1 A schematic diagram of a hybrid powertrain is shown. DETAILED DESCRIPTION

[0031] The schematically shown hybrid powertrain 1 comprises partial powertrains 2, 3. The partial powertrain 2 comprises an internal combustion engine 4, which here has four cylinders 5 and a crankshaft 6 driven in rotation thereby. A torsional elastic body 7, which here is a torsional oscillation damper such as a dual-mass flywheel, is accommodated on the crankshaft 6 and separates the partial powertrain 2 from the partial powertrain 3. A device 8 for detecting a rotational characteristic value of the crankshaft 6 and thus for controlling the internal combustion engine is assigned to the first partial powertrain 2. To this end, a sensor ring is arranged on the input portion of the torsional elastic body 7, from which the sensor detects a measurement signal from the incremental detection of the sensor ring and from which the corresponding rotational characteristic value, for example the speed, the rotational angle, the rotational acceleration and / or the like, is determined.

[0032] The output section of the torsional elastic body is connected to the rotor 10 of the electric machine 9 in a rotationally locked manner. The electric machine 9 is assigned to the partial drive train 3. The electric machine 9 is controlled by means of a device 11 for determining a rotational characteristic value. For example, the device 11 can be formed by one or more Hall sensors which are arranged in a rotationally locked manner on the rotor or on a component connected to the rotor in order to detect increments distributed around the circumference of the rotor and to use these increments to determine the rotational characteristic value of the rotor 10 and to control the commutation of the electric machine and to determine the position of the rotor as a function of time. Alternatively, the electric machine 9 can be controlled by means of the device 11 without sensors, wherein electrical variables of the stator 12 are detected and evaluated by means of a state observer.

[0033] In order to determine a misfire of the internal combustion engine 4 quickly and reliably in the proposed method and in order to control the electric machine 9 such that the vibrational energy is extracted from the torsional elastic body or brought out of the resonance range if a quality indicator determined from the detected measured values of the devices 8, 11 is exceeded, and the signals of the devices 8, 11 are evaluated together by a control unit not shown. As a result, the rotational characteristic value of the drive train section 2, 3 can be determined or at least estimated, and with the knowledge or modeling of the system properties of the hybrid drive train it is possible to determine or at least estimate influencing variables on the drive train section 2, 3 and the torsional elastic body 7, such as applied torque, rotational acceleration, mass moment of inertia, etc., and from this to determine a quality indicator.

[0034] For example, by comparing the rotational characteristic values of the devices 8, 11, the effect of the ignition process before and after the torsional elastic body 7 can be detected, and the influence of a misfire on both partial drive trains 2, 3 can be recognized, and a quality indicator can be determined, which is, for example, a measure of the efficiency of the hybrid drive train, of the comfort acting on the vehicle and / or of the damage to the hybrid drive train 1, in particular to the torsional elastic body 7. For example, the shape of the successive ignition processes of the cylinders 5 can be compared with one another, and interruptions can be recognized in real time from changes in the shape. Alternatively or additionally, by observing the torsional angle between the crankshaft 6 and the rotor 10 under otherwise constant conditions, for example without engine interventions in the internal combustion engine 4 and without changing the control of the electric machine 9, a misfire can be recognized as a result of a change in the torsional angle.

[0035] List of reference signs

[0036] 1 hybrid drive train

[0037] 2 partial drive train

[0038] 3 partial drive train

[0039] 4 internal combustion engine

[0040] 5 cylinder

[0041] 6 crankshaft

[0042] 7 torsional elastic body

[0043] 8 device

[0044] 9 electric machine

[0045] 10 rotor

[0046] 11 device

[0047] 12 stator

Claims

1. A method for controlling a hybrid powertrain (1), the hybrid powertrain having a first part of the powertrain (2) and a second part of the powertrain (3), the first part of the powertrain having an internal combustion engine (4) with a crankshaft (6) and a first device (8) for detecting rotational characteristic values ​​of the crankshaft (6) to control the internal combustion engine (4), the second part of the powertrain being separated from the first part of the powertrain by a torsional elastomer (7) for torsional oscillation isolation from torsional oscillations of the internal combustion engine (4), the second part of the powertrain having a motor (9) with a rotor (10) and a second device (11) for detecting rotational characteristic values ​​of the rotor (10) to control the motor (9), characterized in that, The efficiency, comfort and / or damage-related quality indicators of the torsional elastomer (7) are determined by analyzing the rotational characteristic values ​​of the two devices (8, 11), and the motor (9) is controlled to optimize the quality indicators. Downstream of the motor (9) is a disengaged clutch that is controlled to be at least partially opened by the motor (9) due to mass loss.

2. The method according to claim 1, characterized in that, The vibration amplitude is determined by means of the device (8, 11) and the vibration amplitude is reduced by controlling the motor (9).

3. The method according to claim 1, characterized in that, The devices (8, 11) are used to determine the existing resonance of the torsional elastomer (7) and to eliminate the resonance by controlling the motor (9).

4. The method according to claim 1, characterized in that, The quality index is determined based on the relative torsional angle, relative torsional speed and / or relative acceleration between the input and output portions of the torsional elastomer (7).

5. The method according to claim 1, characterized in that, After the quality indicators have been determined, the motor (9) is controlled by means of the control unit used to control the internal combustion engine (4).

6. The method according to claim 1, characterized in that, The motor (9) is controlled according to the quality index determined by the device (8, 11).

7. The method according to claim 2, characterized in that, The motor (9) is controlled to minimize the difference in rotational characteristic values ​​of the device (8, 11).

8. The method according to claim 2, characterized in that, Vibrational energy is extracted from the torsional elastomer (7) by means of controlling the application of a predetermined rotational nonuniformity on the motor (9).

9. The method according to claim 2, characterized in that, The motor (9) is controlled such that the rotational characteristic value is not exceeded within the stop of the torsional elastomer (7).

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