Method for controlling a hybrid drive train of a vehicle

Abstract

The invention relates to a method for controlling a hybrid drive train of a vehicle, wherein a hybrid disconnect clutch (4) disconnects or connects an internal combustion engine (2) and an electric motor (3), wherein a torque output by the internal combustion engine (2) and / or the electric motor (3) is transmitted to a drive wheel (10) of the hybrid vehicle. In a method for suppressing noise interference caused by a drive train of a hybrid vehicle, an overpressure of the hybrid disconnect clutch (4) is reduced by torque compensation, wherein the hybrid disconnect clutch (4) operates at a slip limit.

Description

Technical Field

[0001] The invention relates to a method for controlling a hybrid drive system of a vehicle, wherein a hybrid separation clutch separates or connects an internal combustion engine and an electric motor, wherein a torque output by the internal combustion engine and / or the electric motor is transmitted to drive wheels of the hybrid vehicle. Background Art

[0002] A drive train for a hybrid vehicle is known from WO 2016 / 008463 A1, which consists of an internal combustion engine and an electric motor, which are separated by a hybrid separation clutch, wherein the torque generated by the internal combustion engine and / or the electric motor is transmitted to the drive wheels via a transmission.

[0003] It is also known that in order to isolate the transmission system, a dual mass flywheel or a common vibration damping element is connected between the internal combustion engine and the electric motor. The dual mass flywheel is designed for optimal isolation between the transmission system and the internal combustion engine. If the secondary mass of the dual mass flywheel is designed as the input end of the separation clutch, another vibration system with a large inertia is obtained between the hybrid separation clutch and the electric motor, and the vibration system has the potential energy to produce rattles or rattles in the hybrid drive system. In order to prevent this, the clutch plate of the hybrid separation clutch can be coupled to the internal combustion engine, wherein the hybrid separation clutch including the electric motor serves as the secondary mass of the dual mass flywheel. Alternatively, a correspondingly large clutch plate can be used as a damper, which can replace the dual mass flywheel. However, this disc damper has only a limited torsion angle and will be locked from the characteristic torque and therefore does not work. Therefore, sufficient transmission isolation cannot be achieved in all types of drive systems of hybrid vehicles.

[0004] DE 10 2013 214 200 A1 discloses a method for controlling a transmission, in which, in order to reduce or suppress rattling noises in a dual clutch transmission, a clutch of a non-selected transmission branch is engaged for a limited time, so that it operates with slip. Summary of the invention

[0005] The object of the present invention is to specify a method for controlling a hybrid drive train in which noise generated by the hybrid drive train during its operation is avoided.

[0006] According to the invention, the technical problem is solved in that the overpressure of the hybrid isolating clutch is reduced by torque compensation, wherein the hybrid isolating clutch operates at the slip limit. In the following, the slip limit is to be understood as a clutch position at which adhesion of the hybrid isolating clutch just no longer occurs. This torque compensation makes it possible to avoid resonance modes caused by the internal combustion engine in the hybrid drive train. The corresponding noise caused by the high amplitude of the vibration unit formed between the secondary mass of the dual mass flywheel and the electric motor is suppressed. Therefore, the hybrid isolating clutch is only engaged up to a certain maximum transmission capacity, whereby the alternating torque between the dual mass flywheel and the electric motor does not increase further. In the proposed overpressure of the hybrid isolating clutch, there is no macroscopic slip in terms of measurement technology.

[0007] Advantageously, if the hybrid drive train is in resonance mode, the overpressure of the hybrid disconnect clutch is reduced by torque compensation. The proposed solution makes it possible, in particular, to reduce the amplitude in resonance mode and thus to suppress rattling noises in the hybrid drive train. However, the solution can also be used outside of resonance mode, since no negative influence on the noise disturbance occurs.

[0008] In one embodiment, the slip control is stopped during the torque compensation. This is advantageous because the slip control is energetically disadvantageous and the energy loss is reduced due to the slip control being switched off. Since the slip control problem is avoided, the strategy can also be designed more simply for noise suppression and the hybrid disconnect clutch itself. The hybrid disconnect clutch is therefore designed not only as a pure locking clutch but also as a strategy clutch in connection with the noise disturbance of the drive train, since the requirements on the response and accuracy of the hybrid disconnect clutch in this case are lower during the slip avoidance period than during the slip control period.

[0009] In a variant, the torque of the internal combustion engine with a deviation is transmitted by the hybrid disconnect clutch at the slip limit. Outside the resonance mode, the hybrid disconnect clutch remains adhered during the slip avoidance period, so that no unnecessary friction energy is wasted.

[0010] In one specific embodiment, the slip limit is detected using the speed difference between the speed of the internal combustion engine and the speed of the electric motor. This is a computationally simple method that can be performed in real time.

[0011] In one embodiment, the rotation speed of the internal combustion engine is filtered before the rotation speed difference is formed. This makes the filtered rotation speed of the internal combustion engine a straight line about which the rotation speed of the electric motor oscillates, thereby making it possible to identify the slip limit very quickly and easily.

[0012] Advantageously, the speed of the internal combustion engine is filtered during a main excitation period. In a four-cylinder internal combustion engine, the main excitation period is, for example, half the number of crankshaft revolutions. In this case, if the speed signal of the electric motor has a frequently changing sign, a sticking state can be reliably detected.

[0013] In one embodiment, in order to improve the torque accuracy, the friction coefficient is adapted outside the resonance phase and the friction coefficient is kept constant during the resonance phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention has a large number of embodiments, one of which will be further described below in conjunction with the illustrations shown in the accompanying drawings.

[0015] The attached pictures are:

[0016] Figure 1 shows a schematic diagram of a hybrid drive of a motor vehicle,

[0017] Figure 2 A schematic diagram showing the vibration characteristics in a hybrid drive train,

[0018] Figure 3 shows a comparison of the vibration characteristics of a hybrid drive train when the hybrid disconnect clutch is fully engaged and when the hybrid disconnect clutch is operating at the slip limit,

[0019] Figure 4 shows a comparison of the rotational speeds of the internal combustion engine and the electric motor when the hybrid disconnect clutch is engaged and when the hybrid disconnect clutch is operated at the slip limit, and

[0020] Figure 5 An enlarged view of the output signals of the internal combustion engine and the electric motor for determining the state of adhesion is shown. DETAILED DESCRIPTION

[0021] exist Figure 1 , a schematic diagram of a drive train 1 of a hybrid vehicle is shown. The drive train 1 comprises an internal combustion engine 2 and an electric motor 3. A clutch 4 is arranged between the internal combustion engine 2 and the electric motor 3, immediately after the internal combustion engine 2. The internal combustion engine 2 and the clutch 4 are connected to each other via a crankshaft 5. The electric motor 3 has a rotatable rotor 6 and a fixed stator 7. The output shaft 8 of the hybrid separation clutch 4 is connected to a transmission 9, which contains a connecting element (not shown in detail), such as a second clutch or a torque converter, which is arranged between the electric motor 3 and the transmission 9. The transmission 9 transmits the torque generated by the internal combustion engine 2 and / or the electric motor 3 to the drive wheels 10 of the hybrid vehicle. In this case, the electric motor 3 and the transmission 9 form a transmission system 11, which is controlled, for example, by a hydrostatic clutch actuator 12.

[0022] The hybrid separation clutch 4 arranged between the internal combustion engine 2 and the electric motor 3 is engaged in order to start the internal combustion engine 2 or to travel in boost mode with the internal combustion engine 2 and the electric motor 3 driving.

[0023] exist Figure 2 An equivalent diagram of the vibration characteristics of the hybrid drive train 1 is shown in FIG. The internal combustion engine 2 is connected to a dual mass flywheel 13, 14, wherein the secondary side 14 of the dual mass flywheel is coupled to a clutch plate 15 of the hybrid separation clutch 4. Alternatively, the secondary side 14 of the dual mass flywheel can be a disk damper, which is in operative connection with the clutch plate 15 of the hybrid separation clutch 4. The clutch plate 15 is mechanically connected to the electric motor 3, which in turn is coupled to the wheels 10 of the hybrid vehicle. A first rotational speed sensor 16 is arranged opposite the crankshaft 5, and a second rotational speed sensor 17 is arranged opposite the electric motor 3, which transmits their signals to a motor control unit 18, which determines whether the hybrid separation clutch 4 is operating at the slip limit based on the difference between the two rotational speeds.

[0024] In order to prevent noise interference, preferably rattling due to the vibration characteristics of the clutch plate 15 of the hybrid separation clutch 4 and the vibration system of the electric motor 3, the electric motor control unit 18 controls the hybrid separation clutch 4 so that it is no longer in a sticking state. In other words, the hybrid separation clutch 4 is at the slip limit. In order to adjust the slip limit, the hybrid separation clutch 4 is squeezed together to such an extent that the torque of the internal combustion engine 2 can be transmitted through the hybrid separation clutch 4. In this case, the hybrid separation clutch 4 is in a slightly overpressure state, but is not fully engaged. In order to be able to accurately adjust the slip limit, the speed of the internal combustion engine 2 is filtered. When using an internal combustion engine 2 with 4 cylinders, the filtering is performed in the range of half the crankshaft speed.

[0025] In the following diagram, the vibration characteristics of an engaged hybrid separator clutch 4 (column I) are shown in comparison with the vibration characteristics of a hybrid separator clutch operated in a state of slight overpressure (column II). Figure 3In row a, the clutch torque TC_eng (curve 1) of the internal combustion engine 2 is shown in comparison with the clutch torque TC_I (curve 2) of the electric motor 3. Row b shows the rotational speed n_hub (curve 3) of the clutch plate 15 relative to the rotational speed n_Sec (curve 4) of the secondary side 14 of the dual mass flywheel. In row c, the rotational speed n_Sec (curve 5) of the secondary side 14 of the dual mass flywheel and the rotational speed n_Pri (curve 6) of the primary side 13 of the dual mass flywheel 13, 14 are shown in comparison. In row d, the rotational speed n_EM of the electric motor 3 in two clutch states (columns I, II) is shown by curve 7. As is known from column I, when the hybrid decoupling clutch 4 is in the engaged state, the rotational speed of the electric motor 3 oscillates around the filtered rotational speed of the internal combustion engine 2. Correspondingly, in column II, when the hybrid decoupling clutch 4 operates at the slip limit, the torque transmission of the hybrid decoupling clutch 4 is limited. When the hybrid separating clutch 4 is engaged, the clutch plate 15 vibrates approximately sinusoidally according to the curve 3, while in column II, when the hybrid separating clutch 4 is overpressurized at the slip limit, although slip occurs on a microscopic scale, no vibration can be generated on a macroscopic scale. The comparison of row c shows that due to the function of the hybrid separating clutch 4, at the slip limit, the speed of the secondary side 14 of the dual mass flywheel is strongly damped relative to the speed of the primary side 13 of the dual mass flywheel. The transmission of this vibration causes the speed n_EM of the electric motor 3 (column II, row d) to vibrate less.

[0026] For a better understanding, Figure 4 The speed n_EM of the electric motor 3, the speed n_Pri of the primary side 13 of the dual mass flywheel and the speed n_Sec of the secondary side 14 of the dual mass flywheel are more clearly shown in FIG. Figure 4 In a, when the hybrid separating clutch 4 is engaged, the speed n_EM of the electric motor 3 has high resonance in the range between 4 and 6 s at 1.2-1.6 rpm. By applying a lower overpressure of the almost engaged hybrid separating clutch 4, the speed n_EM of the electric motor 3 is almost completely damped.

[0027] Figure 5 The following curve diagram is shown, which can be used to determine whether the hybrid separation clutch 4 is in a sticking state or a slipping state. Figure 5a The unfiltered signal of the speed of the internal combustion engine 2 is shown as curve 8. Curve 9 shows the filter width of the control unit 18, which is half the crankshaft revolution in the case of a predefined condition. As described above, after filtering the output signal of the internal combustion engine 2, an approximately straight line signal is obtained. This straight line is surrounded by periodic vibrations representing the speed of the electric motor 3. Since the speed of the electric motor 3 describes its low-frequency movement that oscillates around the filtered signal of the internal combustion engine 2 (curve 1), it can be determined that the hybrid separation clutch 4 is in a sticking state.

[0028] Due to the above design, if the hybrid separation clutch 4 is engaged until a certain maximum transmission capacity, the resonance between the hybrid separation clutch 4 and the electric motor 3 is reliably suppressed, which is excited by the internal combustion engine 2 within the maximum stroke and causes a high alternating torque between the hybrid separation clutch 4 and the electric motor 3. This prevents the alternating torque between the hybrid separation clutch 4 and the electric motor 3 from further increasing. In addition to the resonance, the hybrid separation clutch 4 remains adhered when avoiding slip and does not use unnecessary friction energy. That is, if no resonance is generated due to additional damping devices, such as on the electric motor 3 or in the transmission 9, there is no disadvantage. In particular, in the case of a dry hybrid separation clutch 4, a disc damper can be omitted or a stop can be constructed more advantageously. This leads to potential cost savings or design freedom, because the structural space of the hybrid separation clutch 4 can be more advantageously utilized. Generally, the hybrid separation clutch 4 can be regarded as a protection for the transmission assembly between the hybrid separation clutch 4 and the electric motor 3. This applies not only to shafts and gears, but also to chains in the case of axially parallel electric motor arrangements or side dampers of the hybrid separation clutch. This provides the option of designing the hybrid disconnect clutch 4 either toward the internal combustion engine 2 or toward the transmission 9. Without such component protection, there is a risk of damaging the shaft or the toothing. The method described can be used in all types of hybrid disconnect clutches and is not limited to what is described in the exemplary embodiment.

[0029] Reference numerals list

[0030] 1 Hybrid drive train

[0031] 2 Internal combustion engine

[0032] 3. Electric Motor

[0033] 4 Hybrid disconnect clutch

[0034] 5 Crankshaft

[0035] 6 Rotor

[0036] 7 Stator

[0037] 8 Driven shaft

[0038] 9 Transmission

[0039] 10. Wheel

[0040] 11 Speed ​​Shifting System

[0041] 12 Clutch actuator

[0042] 13 Primary side of a dual mass flywheel

[0043] 14 Secondary side of a dual mass flywheel

[0044] 15 Clutch disc

[0045] 16 Speed ​​sensor

[0046] 17 Speed ​​sensor

[0047] 18 Motor Controller

Claims

1. A method for controlling a hybrid drive train in a vehicle, wherein: A hybrid decoupling clutch (4) decouples or connects an internal combustion engine (2) and an electric motor (3), wherein the torque output by the internal combustion engine (2) and / or the electric motor (3) is transmitted to the drive wheels (10) of the vehicle, characterized in that the overpressure of the hybrid decoupling clutch (4) is reduced by torque compensation, wherein the hybrid decoupling clutch (4) operates at a slip limit; if the hybrid drive system (1) is in a resonance mode, the overpressure of the hybrid decoupling clutch (4) is reduced by torque compensation, and in order to improve the torque accuracy, a friction coefficient adaptation is performed outside the resonance phase, and the friction coefficient is kept constant during the resonance phase.

2. The method according to claim 1, characterized in that The slip control is stopped during the torque compensation.

3. The method according to claim 1 or 2, characterized in that: At the slip limit, a torque of the internal combustion engine (2) with a deviation is transmitted via the hybrid separator clutch (4).

4. The method according to claim 1 or 2, characterized in that: The slip limit is detected using a speed difference between a speed of the internal combustion engine (2) and a speed of the electric motor (3).

5. The method according to claim 4, characterized in that The rotational speed of the internal combustion engine (2) is filtered before forming the rotational speed difference.

6. The method according to claim 5, characterized in that The rotation speed of the internal combustion engine (2) is filtered during the main excitation cycle.

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