Methods for increasing the safety of a hybrid vehicle

Abstract

A method for increasing the safety of a hybrid vehicle, in which a hybrid disconnect clutch (4) disconnects or connects an internal combustion engine (2) and an electric motor (3) and the torque output by the internal combustion engine (2) and / or the electric motor (3) is transmitted to drive wheels (10) of the hybrid vehicle, wherein, when the electric motor (3) is used as a drive motor, in the event of a fault in the hybrid disconnect clutch (4), the speed (NIce) of the internal combustion engine (2) is limited to the current speed (NEMot) of the electric motor (3), wherein, for monitoring the fault in the hybrid disconnect clutch (4), the speeds of the internal combustion engine (2) and the electric motor (3) are monitored, characterized in that, for monitoring the fault in the hybrid disconnect clutch (4), a modulation signal is applied to the speed (NEMot) of the electric motor (3).where, when the modulation signal occurs at the speed (NIce) of the combustion engine (2), it is concluded that the hybrid disconnect clutch (4) is transmitting a torque (Trq-Cl).

Description

[0001] The invention relates to a method for increasing the safety of a hybrid vehicle, in which a hybrid disconnect clutch separates or connects an internal combustion engine and an electric motor and the torque output by the internal combustion engine and / or the electric motor is transferred to the drive wheels of the hybrid vehicle.

[0002] US 2014 / 0162839A1 discloses a method for controlling a disconnect clutch in a hybrid vehicle.

[0003] DE 10 2006 005 131 A1 discloses a two-plus-two gearbox for electric hybrid transmissions.

[0004] US 2014 / 0194246A1 discloses a method for fault detection on a clutch in a hybrid vehicle.

[0005] In hybrid vehicles that allow various combinations of drive modes, such as electric motor, electric generator, combustion engine in coasting or acceleration mode, combustion engine or electric motor OFF, a mechanical decoupling of the torques of the combustion engine and electric motor is necessary. This decoupling is typically achieved by a hybrid disconnect clutch, which is actuated automatically. This automatic actuation of the hybrid disconnect clutch is controlled by an actuator consisting of a control unit with corresponding software for controlling the electromechanical or electrohydraulic actuator that operates the clutch. However, under predefined operating conditions where the hybrid disconnect clutch must be open, a faulty control signal from the control unit can cause the hybrid disconnect clutch to close, potentially leading to safety issues with the hybrid vehicle's drive system.Known measures to increase the safety of the hybrid vehicle in such a fault situation consist of an additional clutch, which is typically located in a downstream transmission, entering a protective mode by fully or partially opening the downstream clutch.

[0006] The invention is based on the objective of providing a method for increasing the safety of a hybrid vehicle, which is used to prevent safety risks in the event of a faulty opening of the hybrid disconnect clutch.

[0007] According to the invention, the problem is solved by limiting the rotational speed of the combustion engine to the current rotational speed of the electric motor when the electric motor is used as the drive motor in the event of a failure of the hybrid disconnect clutch. Because the rotational speed of the combustion engine does not exceed the rotational speed of the electric motor, acceleration of the hybrid vehicle is prevented, thus reliably preventing safety-critical situations that could be caused by unintended acceleration of the hybrid vehicle.

[0008] Advantageously, the combustion engine's speed is set to less than or equal to the electric motor's current speed when the electric motor's speed is equal to or greater than the combustion engine's idle speed. This has the advantage that the combustion engine continues to operate and can, for example, be used to charge the electric motor's high-voltage battery, but it cannot contribute to propelling the hybrid vehicle.

[0009] Alternatively, ignition of the combustion engine is suppressed if the current speed of the electric motor is below the idle speed of the combustion engine. This ensures that the combustion engine is not activated and therefore does not contribute to the propulsion of the hybrid vehicle.

[0010] In one variant, if the combustion engine's speed is not limited to the current speed of the electric motor, a torque intervention is applied to the combustion engine if it exceeds the electric motor's speed. This torque intervention reduces the combustion engine's speed and thus limits its impact on the hybrid vehicle's propulsion.

[0011] Alternatively, if the combustion engine's speed is not limited to the current speed of the electric motor, an ignition intervention occurs at the combustion engine if the speed exceeds the electric motor's speed. By preventing ignitions of the combustion engine, an increase in its speed can be prevented.

[0012] According to the invention, the rotational speeds of the combustion engine and the electric motor are monitored to detect faults in the hybrid disconnect clutch. This allows a reliable conclusion to be drawn as to whether the hybrid disconnect clutch is transmitting a clutch torque or not, i.e., whether it is engaged or disengaged.

[0013] According to the invention, a modulation signal is superimposed on the rotational speed of the electric motor to monitor for faults in the hybrid disconnect clutch. When this modulation signal occurs at the rotational speed of the combustion engine, it is concluded that the hybrid disconnect clutch is transmitting torque. This monitoring method is particularly advantageous when the hybrid disconnect clutch should actually be open. Upon detection of the modulation signal being transmitted at the rotational speed of the combustion engine, it can be reliably concluded that the hybrid disconnect clutch is in an unintentionally closed state.

[0014] A further development of the invention relates to a method for increasing the safety of a hybrid vehicle, in which a hybrid disconnect clutch separates or connects an internal combustion engine and an electric motor, and the torque output by the internal combustion engine and / or the electric motor is transmitted to the drive wheels of the hybrid vehicle. In a method that increases the safety of the hybrid vehicle, the hybrid disconnect clutch is open when starting with the electric motor. If the battery level of one of the electric motor's batteries is low, the internal combustion engine is started to charge the battery. If the hybrid disconnect clutch closes unintentionally, a method according to at least one feature described in this patent application is initiated.

[0015] The invention allows for numerous embodiments. One of these will be explained in more detail with reference to the figures shown in the drawing.

[0016] They show: Fig. 1. A schematic representation of a hybrid drive system, Fig. 2 an exemplary embodiment of a situation of driving operation of the hybrid vehicle according to the state of the art, Fig. 3 an embodiment of the method according to the invention.

[0017] In Fig. Figure 1 shows a schematic diagram of a powertrain 1 of a hybrid vehicle. This powertrain 1 comprises an internal combustion engine 2 and an electric motor 3. A hybrid disconnect clutch is arranged directly behind the internal combustion engine 2 and the electric motor 3. The internal combustion engine 2 and the hybrid disconnect clutch 4 are connected to each other via a crankshaft 5. The electric motor 3 has a rotatable rotor 6 and a stationary stator 7. The output shaft 8 of the hybrid disconnect clutch 4 is connected to a gearbox 9, which contains a coupling element (not shown), for example, a second clutch or a torque converter, arranged between the electric motor 3 and the gearbox 9. The gearbox 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.The electric motor 3 and the gearbox 9 form a gearbox system 11, which is controlled by a hydrostatic clutch actuator 12.

[0018] The hybrid disconnect clutch 4, located between the combustion engine 2 and the electric motor 3, is closed to start the combustion engine 2 while the hybrid vehicle is driving, using the torque generated by the electric motor 3, or to enable driving with both the combustion engine 2 and the electric motor 3 engaged during boost operation. The hybrid disconnect clutch 4 is actuated by the hydrostatic clutch actuator 12.

[0019] In another operating state, the hybrid vehicle is started from a standstill using the electric motor 3. The combustion engine 2 is off, and the hybrid disconnect clutch 4 is open. Fig. 2a shows the rotational speed NIce of the combustion engine 2 and the rotational speed NEMot of the electric motor 3 over time. Fig. 2b shows the current torque Trq_Cl transmitted by the hybrid disconnect coupling 4, while in Fig. 2c clarifies the requirement B_Res_Ice for starting the combustion engine 2. As shown in section 2c. Fig. As can be seen in Figure 2, the hybrid disconnect clutch 4 is unintentionally closed at time t=10s due to a defect in the hydrostatic clutch actuator 12, and a torque Trq_CI is transmitted. At time t=20s, however, the combustion engine 2 is started due to a low state of charge (SOC) of the electric motor 3's high-voltage battery (not shown). The combustion engine 2 is intended to charge the battery at an increased charging speed NIce of approximately 1500 rpm. For this to occur, the hybrid disconnect clutch 4 must be open. Since the hybrid disconnect clutch 4 is closed due to the defect in the hydrostatic clutch actuator 12, the hybrid vehicle is unintentionally accelerated from a time t>20s onwards, which can lead to a critical driving situation.

[0020] The related to Fig. The dangerous situation described in section 2 can be prevented by using the method according to the invention, as described in Fig. 3 is shown using an exemplary embodiment. Fig. 3 has the same subdiagrams 3a, 3b, 3c as Fig.2. In the event that the hybrid disconnect clutch 4 closes unintentionally at time t=10s, this closure is detected. Detection is achieved by monitoring the rotational speeds of the combustion engine 2 and the electric motor 3. To determine whether the hybrid disconnect clutch 4 is actually transmitting torque, a modulation signal, not relevant to driving comfort, is superimposed on the rotational speed of the electric motor 3. This modulation signal could, for example, be a 30 Hz sine wave with a low torque amplitude. If the hybrid disconnect clutch 4 is closed, as in this case, this modulation will appear on the rotational speed signal of the combustion engine 2. This can be verified using correlation or log-in methods. Based on this evaluation, it is reliably determined that the clutch is not open.

[0021] Since it is known that the hybrid disconnect clutch 4 is not open, a speed mode is set on the combustion engine 2, which limits the speed NIce of the combustion engine 2 to the current speed NEMot of the electric motor 3. In the given case, the speed NIce of the combustion engine 2 may not exceed 800 rpm. This means that at time t=20s, when the demand to charge the battery of the electric motor 3 occurs, the combustion engine 2 cannot reach a higher speed NIce. Thus, unwanted acceleration of the hybrid vehicle by the combustion engine 2 is prevented despite the closed hybrid disconnect clutch 4.

[0022] In cases where the electric motor 3 serves as the drive motor, the described method ensures that the speed NIce of the combustion engine 2 will not be higher than the speed NEMot of the electric motor 3. Reference symbol list 1 Powertrain 2 Internal combustion engine 3 Electric motor 4 Hybrid disconnect coupling 5 Crankshaft 6 Rotor 7 Stator 8 Output shaft 9 gearboxes 10 drive wheels 11 Transmission system 12 Hydrostatic clutch actuator Nice engine speed NEMot Electric motor speed Trq-CI torque of the hybrid disconnect clutch

Claims

[1] Method for increasing the safety of a hybrid vehicle in which a hybrid disconnect clutch (4) disconnects or connects an internal combustion engine (2) and an electric motor (3) and the torque output by the internal combustion engine (2) and / or the electric motor (3) is transmitted to drive wheels (10) of the hybrid vehicle, wherein, when the electric motor (3) is used as a drive motor, in the event of a fault of the hybrid disconnect clutch (4), the speed (NIce) of the internal combustion engine (2) is limited to the current speed (NEMot) of the electric motor (3), wherein, to monitor the fault in the hybrid disconnect clutch (4), the speeds of the internal combustion engine (2) and the electric motor (3) are monitored. characterized by, that to monitor the fault case at the hybrid disconnect clutch (4) a modulation signal is applied to the speed (NEMot) of the electric motor (3), whereby when the modulation signal occurs at the speed (NIce) of the combustion engine (2) it is concluded that the hybrid disconnect clutch (4) is transmitting a torque (Trq-Cl). [2] Method according to claim 1, characterized by , that the speed (NIce) of the internal combustion engine (2) is set to be less than or equal to the current speed (NEMot) of the electric motor (3) when the speed (NEMot) of the electric motor (3) is equal to or greater than the idle speed of the internal combustion engine (2). [3] Method according to claim 1, characterized by , that ignition of the internal combustion engine (2) is suppressed when the current speed (NEMot) of the electric motor (3) is below the idle speed of the internal combustion engine (2). [4] Method according to claim 1, 2 or 3, characterized by, that if the speed (NIce) of the combustion engine (2) is not limited to the current speed (NEMot) of the electric motor (3) above the electric motor speed (NEMot), a torque intervention occurs at the combustion engine (2). [5] Method according to claim 1, 2 or 3, characterized by , that if the speed (NIce) of the combustion engine (2) is not limited to the current speed (NEMot) of the electric motor (3) above the electric motor speed (NEMot), an ignition intervention takes place at the combustion engine (2). [6] Method for increasing the safety of a hybrid vehicle in which a hybrid disconnect clutch (4) disconnects or connects an internal combustion engine (2) and an electric motor (3) and the torque output by the internal combustion engine (2) and / or the electric motor (3) is transmitted to drive wheels (10) of the hybrid vehicle, wherein when starting with the electric motor (3) the hybrid disconnect clutch (4) is open and as a result of a low battery state of one battery of the electric motor (3) the internal combustion engine (2) is started to charge the battery, characterized by , that in the event of an unintentional closing of the hybrid disconnect coupling (4), a method according to one of the preceding claims is initiated.

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