Method for controlling a drive train of a hybrid motor vehicle, control unit for said drive train, and motor vehicle

Abstract

The invention relates to a method for controlling a powertrain of a hybrid motor vehicle comprising an internal combustion engine and an electric machine, the method comprising the following step, performed after the internal combustion engine is stopped, of suppressing a start of the internal combustion engine for a determined period of time after the internal combustion engine is stopped. The invention also relates to a control unit configured for implementing said method and to a motor vehicle equipped with such a control unit.

Description

Technical Field

[0001] This invention relates generally to the field of motor vehicles, and more particularly to the field of hybrid motor vehicles.

[0002] The present invention relates more particularly to a method for controlling the powertrain of a hybrid electric vehicle, a control unit configured to implement the method, and a hybrid electric vehicle equipped with such a central control unit. Background Technology

[0003] Hybrid motor vehicles include an internal combustion engine and at least one electric motor, which provide traction and / or propulsion to the vehicle depending on the vehicle's operating conditions. For example, vehicle traction may sometimes be provided solely by the internal combustion engine (e.g., when a large torque needs to be supplied), sometimes by the electric motor (e.g., when a lower torque needs to be supplied), and sometimes by both.

[0004] To reduce fuel consumption and improve passenger comfort, the internal combustion engine can be turned off when there is no need for it.

[0005] One way to improve passenger comfort in hybrid vehicles is to make the driving experience feel closer to that of a fully electric vehicle, which is equivalent to reducing the noise and vibration caused by the internal combustion engine. This is known as improving NVH (noise, vibration, and harshness) performance.

[0006] In hybrid vehicles, the alternation between the electric motor and the internal combustion engine, especially the frequent starting of the internal combustion engine, can impair NVH performance.

[0007] Therefore, it is necessary to improve the NVH performance of hybrid vehicles. Summary of the Invention

[0008] To overcome the aforementioned deficiencies of the prior art, the present invention proposes a method for controlling the powertrain of a hybrid electric vehicle comprising an internal combustion engine and an electric motor. The method includes the following steps performed after the internal combustion engine has stopped: suppressing the restart of the internal combustion engine for a defined time period after the engine has stopped.

[0009] Therefore, this invention reduces the frequency of internal combustion engine restarts. This, in turn, reduces noise and vibration associated with engine starting and operation, thus improving the vehicle's NVH performance. Furthermore, this invention allows for a reduction in the utilization rate of the internal combustion engine, thereby saving fuel and reducing exhaust emissions. Therefore, from both an economic and ecological perspective, this invention is advantageous.

[0010] Furthermore, this method is simple and adaptable to the handling of motor vehicles in real time. It is also applicable to all hybrid architectures that allow for fully electric traction.

[0011] The following are other advantageous and non-limiting features of the method according to the invention, which are implemented individually or in any technically possible combination:

[0012] - In cases where there is a need to start the vehicle during the suppression step, the vehicle's traction is provided solely by the electric motor;

[0013] - The stopping of the internal combustion engine is detected when the internal combustion engine changes from a previous state in which the internal combustion engine produces non-zero torque to a current state in which the internal combustion engine no longer produces torque.

[0014] - In order to determine the previous state of the internal combustion engine, it is stipulated that the control signals to the internal combustion engine issued before the current moment are read.

[0015] - If the powertrain receives a demand higher than a predetermined threshold, the suppression step is interrupted;

[0016] - The predetermined threshold is equal to the maximum demand that the electric motor can meet alone when the internal combustion engine stops;

[0017] - If the vehicle is in drive mode, the predetermined threshold is equal to the first value, and if the vehicle is in reverse mode, the predetermined threshold is equal to the second value;

[0018] - The electric motor is rotatably connected to the internal combustion engine, and detecting the stopping of the internal combustion engine includes detecting that the speed of the electric motor drops below a predetermined threshold;

[0019] - The hybrid vehicle includes another electric motor that is rotatably coupled to the internal combustion engine, and detecting the stopping of the internal combustion engine includes detecting that the speed of the other electric motor drops below a predetermined threshold.

[0020] The present invention also proposes a control unit for a hybrid motor vehicle, the control unit being configured to implement the method according to the invention.

[0021] The present invention further proposes a hybrid electric vehicle including a powertrain, the hybrid electric vehicle including an internal combustion engine and an electric motor, and equipped with a control unit according to the present invention.

[0022] Of course, the various features, variations and embodiments of the present invention can be combined with each other in various combinations, as long as they are not incompatible or mutually exclusive. Detailed Implementation

[0023] The following description, taken with reference to the accompanying drawings which are given by way of non-limiting example, will make it easy to understand the contents of the invention and how it can be practiced.

[0024] In the attached diagram:

[0025] [ Figure 1 A hybrid electric vehicle according to the present invention is depicted;

[0026] [ Figure 2 [ ] is a logic diagram illustrating an embodiment of the control method according to the present invention;

[0027] [ Figure 3 ]yes Figure 2 A more detailed version of the logic diagram.

[0028] The method according to the invention is applicable to hybrid motor vehicles (e.g. Figure 1 The powertrain of the hybrid electric vehicle shown.

[0029] The hybrid motor vehicle 15 is typically a (rear-wheel and / or front-wheel drive) car, but can also be a truck, bus, ship, or even an aircraft.

[0030] The hybrid vehicle includes an internal combustion engine 16 and at least one electric motor 17, both of which are adapted to provide drive for the vehicle 15 independently of each other.

[0031] For this purpose, the powertrain includes a transmission 18 that is coupled to the driven wheels 19 of the vehicle 15 and is capable of transmitting torque generated by the electric motor 17 and the internal combustion engine 16 to these wheels 19.

[0032] The transmission 18 allows the internal combustion engine 16 to be disconnected from the driven wheel 19, enabling the vehicle 15 to be driven in a "fully electric" mode. Preferably, the transmission also allows the electric motor 17 to be disconnected from the driven wheel 19, enabling the vehicle 15 to be driven in a "fully engine" mode. It also allows both the electric motor 17 and the internal combustion engine 16 to be simultaneously connected to the driven wheel 19.

[0033] The method according to the invention advantageously enables the suppression of the start-up of the internal combustion engine within a defined time period Δt after the engine has last stopped. For example, during this defined time period, the vehicle 15 is driven by traction provided by the electric motor 17.

[0034] The time interval Δt is greater than or equal to 2 seconds.

[0035] This method can be implemented, in particular, by a control unit 20 of the motor vehicle 15. For example, the control unit 20 includes a microprocessor and memory, and is configured to receive data from various sensors and control interfaces of the motor vehicle 15. This data includes the speed of each motor (crankshaft rotation speed), the value of the motor control signal selected by the driver, the value of the torque supplied by one or more motors in operation, the value of the torque transmitted to the wheels of the vehicle 15, and so on.

[0036] The following text combines Figure 2 and Figure 3 The described embodiment enables the suppression of the start-up of the internal combustion engine 16 of the vehicle 15 during a defined time period Δt, such that during this defined time period Δt, only the motor 17 provides drive to the vehicle 15 in the form of traction unless the torque requested by the driver is greater than the torque that the motor 17 can supply.

[0037] Figure 2 An algorithm for implementing this embodiment is illustrated schematically, which corresponds, for example, to the execution of program code hosted in the memory of the control unit 20. The algorithm here comprises three functions.

[0038] The first function F1 is configured to detect the stop of the internal combustion engine 16 and issue a corresponding first output signal ENG_OFF_DLY_REQ_SET or a signal indicating that the engine has stopped.

[0039] The second function F2 is configured to determine whether it is appropriate to interrupt the suppression of the start-up of the internal combustion engine 16, whether because the electric motor 17 is unable to supply the torque required by the driver or because the time period Δt has expired. The second function is configured to issue a corresponding second output signal ENG_OFF_DLY_REQ_RST or a signal requesting the interruption of the suppression of engine restart.

[0040] The third function F3 is configured to combine the output signals supplied by the first function F1 and the second function F2. Therefore, the third function F3 determines whether it is appropriate to suppress the starting of the internal combustion engine 16. This third function supplies a corresponding third output signal ENG_OFF_DLY_REQ or a signal for suppressing starting. These three functions will be described and explained in more detail below.

[0041] like Figure 2 and Figure 3 As shown, function F1 is configured to detect a stop of the internal combustion engine 16 when the internal combustion engine 16 transitions from a previous state where the internal combustion engine 16 produces non-zero torque to a current state where the internal combustion engine 16 produces no torque. For this purpose, the first function F1 is configured here to receive and process two input signals, on which the first function supplies a first output signal ENG_OFF_DLY_REQ_SET.

[0042] The first input signal ENG_TQ_SP represents the value of the control signal for the internal combustion engine 16 (a control signal used to calculate the torque requirement that the internal combustion engine 16 needs to apply to the crankshaft at the current moment). Therefore, when the internal combustion engine 16 is detected to have stopped, this signal will represent the value of the power torque requested by the driver before the internal combustion engine 16 stopped.

[0043] The second input signal HSG_SPD provides the engine speed of the internal combustion engine 16.

[0044] For example, consider the case where the internal combustion engine 16 and the electric motor 17 are simultaneously connected to the driven wheel 19. In this case, the output shaft of the electric motor 17 of the motor vehicle 15 is rotatably connected to the crankshaft of the internal combustion engine 16.

[0045] The second input signal HSG_SP under consideration represents the speed of the motor 17, and therefore indirectly represents the speed of the internal combustion engine 16.

[0046] The first input signal ENG_TQ_SP and the second input signal HSG_SPD are delivered, for example, by a function implemented by the computing unit. Here, the first output signal ENG_OFF_DLY_REQ_SET is a logic signal that has a value of TRUE if the internal combustion engine 16 is detected to have stopped, and a value of FALSE if the internal combustion engine 16 is not detected to have stopped.

[0047] like Figure 3 As shown, the first function F1 performs a first operation 4, which is used to determine the current state of the engine, or in other words, to determine whether the internal combustion engine 16 has stopped. Therefore, a first comparison 5 is performed between the value of the second input signal HSG_SPD and a first threshold HSG_SPD_CST, which corresponds to the minimum speed of the electric motor 17; below this minimum speed, the internal combustion engine 16 is considered to have stopped (this minimum speed is typically 125 revolutions per minute). If the value of the second input signal HSG_SPD is lower than the first threshold HSG_SPD_CST, a signal HSG_SPD_DET indicating that the engine has stopped is emitted with a logic value of TRUE. Otherwise, the logic value of the signal HSG_SPD_DET indicating that the engine has stopped is FALSE.

[0048] The first function F1 also performs a second operation 1, which determines the state of the internal combustion engine before detecting that the internal combustion engine 16 has stopped. Therefore, a second comparison 2 is performed between the value of the first input signal ENG_TQ_SP and a second threshold ENG_TQ_SP_CST, which corresponds to the minimum speed of the motor 17. If the speed is higher than this minimum speed, the first input signal ENG_TQ_SP is considered to correspond to substantial engine torque (typically 0 Nm). If the value of the first signal ENG_TQ_SP is higher than the second threshold ENG_TQ_SP_CST, it is considered that the driver actually needs torque before the engine stops. Therefore, the first function F1 delivers a torque detection signal ENG_TQ_DET, which in this example is a logic signal, indicating that torque is needed before the engine stops and provided that the output signal ENG_OFF_DLY_REQ_SET is TRUE (the latter case is...). Figure 1 If the signal is indicated by latch 3, then the value of the logic signal is TRUE.

[0049] As shown in logic AND gate 6, if the values ​​of the torque detection signal ENG_TQ_DET and the engine stop detection signal HSG_SPD_DET are both TRUE, then the logic value of the first output signal ENG_OFF_DLY_REQ_SET becomes TRUE.

[0050] The logic value of the first output signal ENG_OFF_DLY_REQ_SET is specifically transmitted to countdown function 11, which defines a specific time period Δt for which the internal combustion engine 16 is to be suppressed. The first output signal ENG_OFF_DLY_REQ_SET is converted to the logic value TRUE, triggering the start of countdown 12 and the emission of the counter signal ENG_OFF_DLY_TMR_STA corresponding to the countdown value (in this example, the duration in seconds). Upon detecting the end of countdown 13, i.e., when the counter signal ENG_OFF_DLY_TMR_STA reaches a value of 0, the countdown end logic signal ENG_OFF_DLY_TMR_END with a value of TRUE is emitted.

[0051] like Figure 2 and Figure 3 The second function F2 shown is configured to determine whether the motor 17 is able to supply the torque required by the driver. For this purpose, the second function F2 is configured to receive and process three input signals to supply the second output signal ENG_OFF_DLY_REQ_RST.

[0052] The third input signal MAX_AVL_DL_TQ represents an X-dimensional flow, where X is the number of electric drivetrain states existing in the powertrain, i.e., the number of combinations of couplings and reducers that transmit the torque generated by the motor 17 to the driven wheel 19. This third input signal allows determination of the maximum torque that the motor 17 can supply in each drivetrain state. For example, here, the third input signal is a 3-dimensional flow, where the first dimension represents the value of the maximum torque EV1_AVL_DL_TQ in the first state of the drivetrain, which here corresponds to the first gearbox ratio of the vehicle 15; the second dimension represents the value of the maximum torque EV2_AVL_DL_TQ in the second state of the drivetrain, which here corresponds to the second gearbox ratio of the vehicle 15; and the third dimension corresponds to the third state EV_RVR_AVL_DL_TQ of the drivetrain, which here corresponds to the vehicle 15 being in reverse gear.

[0053] The fourth input signal, DRV_TQ_REQ, is a demand signal representing the value of torque requested by the driver. For example, its value depends on how much the accelerator pedal is depressed.

[0054] The fifth input signal GEAR_LEVR_PSN is a logic signal that indicates the position of the gear lever of vehicle 15, which allows it to be determined whether vehicle 15 has been engaged in reverse gear.

[0055] The third, fourth, and fifth input signals are delivered, for example, by functions implemented by the computing unit.

[0056] like Figure 3 As shown, during the third operation 7, the second function F2 selects the electric drive system state that can supply the maximum torque to the driven wheel 19 from the X dimensions of the third input signal, and supplies the value of the maximum torque available for forward gear MAX_EV_AVL_DL_TQ and the value of the maximum torque available for reverse gear EV_RVR_AVL_DL_TQ.

[0057] During the fourth operation 8, the second function F2 determines the difference between the maximum available torque values ​​MAX_EV_AVL_DL_TQ and EV_RVR_AVL_DL_TQ and the fourth input value DRV_TQ_REQ (the torque required by the driver, or demand).

[0058] The fifth operation 9 compares the difference obtained for the forward gear with the third threshold DRV_EV_TQ_DIFF_CST. If the difference is lower than the third threshold, it is assumed that the motor 17 cannot supply the torque required by the driver (e.g., 0 Nm). If the difference is lower than the third threshold DRV_EV_TQ_DIFF_CST, a first motor power deficiency logic signal DRV_EV_AVL_TQ_RST with a value of TRUE is issued.

[0059] The sixth operation 10 compares the difference obtained for reverse gear with the threshold DRV_EV_TQ_DIFF_CST, and if the difference is lower than the third threshold and reverse gear has been engaged (the value of the fifth input signal is TRUE), a second motor power insufficient logic signal RVR_EV_AVL_Q_RST with a value of TRUE is issued.

[0060] Operation 7, step 14, applies a logical OR operator to the first insufficient motor power signal DRV_EV_AVL_TQ_RST, the second insufficient motor power signal RVR_EV_AVL_Q_RST, and the counter end signal ENG_OFF_DLY_TMR_END. The result of this logical operation is the second output signal ENG_OFF_DLY_REQ_RST, which has a value of TRUE if the electric motor cannot supply the torque required by the driver in forward or reverse gear, or if the countdown has expired.

[0061] like Figure 2 and Figure 3 The third function F3 shown is configured to suppress or not suppress the starting of the internal combustion engine 16 based on the values ​​of the first output signal ENG_OFF_DLY_REQ_SET and the second output signal ENG_OFF_DLY_REQ_RST. For this purpose, the third function F3 is configured to receive and process the first output signal ENG_OFF_DLY_REQ_SET and the second output signal ENG_OFF_DLY_REQ_RST to supply a third output signal ENG_OFF_DLY_REQ. If the value of the first output signal ENG_OFF_DLY_REQ_SET is TRUE and the value of the second output signal ENG_OFF_DLY_REQ_RST is FALSE, then the third function F3 issues a third output signal ENG_OFF_DLY_REQ with a logic value of TRUE. The starting of the internal combustion engine 16 is suppressed as long as the value of the third output signal ENG_OFF_DLY_REQ is TRUE.

[0062] This invention is not limited to the references above. Figure 2 and Figure 3 The described embodiments.

[0063] For example, the above describes an electric motor 17 rotatably connected to an internal combustion engine 16, and the rotational speed of the internal combustion engine 16 is determined (function F1) and the ability of the motor to supply the torque required by the driver is evaluated (function F2). The present invention covers embodiments and examples in which the vehicle 15 includes a second electric motor 17 non-rotatably connected to the internal combustion engine 16. The rotational speed of the internal combustion engine 16 is then determined using the first electric motor 17, and the ability of the second electric motor 17 to supply the required torque is evaluated via function F2.

[0064] Furthermore, function F2 compares the difference between the torque requested by the driver and the maximum torque that motor 17 can supply with a third threshold. According to some embodiments, this threshold is zero, or in other words, function F2 simply compares the requested torque with the maximum torque that motor 17 can supply.

[0065] Finally, the interruption suppression step is described when the motor is unable to transmit sufficient torque to the driven wheel. The invention is not limited to this situation, and other interruption suppression steps are conceivable, such as when the battery state of charge is too low, or when the motor and internal combustion engine are connected to different axles of the vehicle and four-wheel drive activation is required (e.g., under poor driving conditions).

Claims

1. A method for controlling the powertrain of a hybrid electric vehicle (15), the hybrid electric vehicle comprising an internal combustion engine (16) and an electric motor (17), characterized in that, The method includes the following steps performed after the internal combustion engine (16) stops: suppressing the starting of the internal combustion engine (16) during a defined time period (Δt) after the internal combustion engine (16) stops.

2. The method as described in claim 1, wherein, If there is a need to start the vehicle (15) during the suppression step (DRV_TQ_REQ), the traction force of the vehicle (15) is supplied only by the motor (17).

3. The method as described in claim 1 or 2, wherein, When the internal combustion engine (16) changes from a previous state where it produces non-zero torque to a current state where it no longer produces torque, the stopping of the internal combustion engine (16) is detected.

4. The method of claim 3, wherein, In order to determine the previous state of the internal combustion engine (16), it is specified to read the control signal (ENG_TQ_SP) issued for the internal combustion engine (16) before the current time.

5. The method according to any one of claims 1 to 4, wherein, If the powertrain receives a demand higher than a predetermined threshold, the suppression step is interrupted.

6. The method of claim 5, wherein, The predetermined threshold is equal to the maximum demand that the motor (17) can meet alone when the internal combustion engine (16) stops.

7. The method of claim 5 or 6, wherein, If the vehicle (15) is in forward gear mode, the predetermined threshold is equal to the first value, and if the vehicle (15) is in reverse gear mode, the predetermined threshold is equal to the second value.

8. The control method according to any one of claims 1 to 6, wherein, The motor is rotatably connected to the internal combustion engine (16), or the hybrid vehicle (15) includes another motor rotatably connected to the internal combustion engine (16), and detecting the stopping of the internal combustion engine (16) includes detecting that the rotational speed (HSG_SPD) of the motor (17) rotatably connected to the internal combustion engine (5) drops below a predetermined threshold (HSF_SPD_CST).

9. A control unit for a hybrid motor vehicle (15), the control unit being configured to implement the method of any one of claims 1 to 8.

10. A hybrid electric vehicle including a powertrain, the hybrid electric vehicle comprising an internal combustion engine (16) and an electric motor (17), characterized in that, The hybrid vehicle is equipped with the control unit (20) as described in claim 9.

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