Control system for hybrid vehicles

Abstract

This invention provides a control device for hybrid vehicles that can reduce torsional vibrations affecting NVH performance while simultaneously achieving good driving performance and fuel efficiency. [Solution] The disengagement clutch control unit 104 connects the drive motor MG to the propeller shaft 16 when torque from the drive motor MG is required, satisfying the required drive torque. On the other hand, when torque from the drive motor MG is not required and it is not necessary for the rotor inertia of the drive motor MG to contribute to the vehicle's NV performance, the disengagement clutch 26 is disengaged to improve driving performance and fuel efficiency. On the other hand, when it is necessary for the rotor inertia of the drive motor MG to contribute to the vehicle's NV performance, the disengagement clutch 26 is engaged, and rotor inertia is added, improving NV performance. This makes it possible to reduce torsional vibrations that affect the vehicle's NV performance while simultaneously improving the vehicle's driving performance and fuel efficiency.

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle having an engine, an automatic transmission, and an electric motor, in which the electric motor is provided between the automatic transmission and a differential gear device.

Background Art

[0002] [[ID=I12]]Patent Document 1 discloses a control device for a hybrid vehicle having an auxiliary electric motor, a clutch, an automatic transmission, a main electric motor, and a differential gear device in this order in a power transmission path from an engine to drive wheels.

[0003] In such a hybrid vehicle, due to the rotor inertia of the main electric motor provided between the automatic transmission and the differential gear device, there is an advantage that torsional vibration of the power transmission system that affects the NV performance of the vehicle can be reduced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, even when the torque of the main electric motor does not occur, since the rotor inertia of the main electric motor is always connected to the drive system, there is a disadvantage that the running performance and fuel consumption performance are suppressed when accelerating by engine torque. Such a disadvantage also occurs in vehicles without an auxiliary electric motor and a clutch, and is a common problem of hybrid vehicles in which the main electric motor is provided between the automatic transmission and the drive wheels.

[0006] This invention was made against the above-mentioned background, and its objective is to provide a control device for a hybrid vehicle that can reduce torsional vibrations affecting NVH performance while simultaneously achieving driving performance and fuel efficiency. [Means for solving the problem]

[0007] In other words, the gist of the present invention is a control device for a hybrid vehicle which is equipped with an automatic transmission and a drive motor in order in a power transmission path from the engine to the drive wheels, the control device comprising: (a) a disconnection clutch that disconnects and connects the drive motor and the power transmission path; and (c) a disconnection clutch control unit which, when torque from the drive motor is required, engages the disconnection clutch to connect the drive motor to the power transmission path, while when torque from the drive motor is not required and it is not necessary for the rotor inertia of the drive motor to contribute to the vehicle's NVH performance, it disconnects the disconnection clutch to disconnect the drive motor from the power transmission path, but when it is necessary for the rotor inertia of the drive motor to contribute to the vehicle's NVH performance, it engages the disconnection clutch to connect the drive motor to the power transmission path. [Effects of the Invention]

[0008] According to the hybrid vehicle control device of the present invention, when torque from the drive motor is required, the clutch is engaged by the clutch control unit, connecting the drive motor to the power transmission path and satisfying the required drive torque. On the other hand, when torque from the drive motor is not required and it is not necessary for the rotor inertia of the drive motor to contribute to the vehicle's NV performance, the clutch is disengaged and the drive motor is disconnected from the power transmission path. However, when it is necessary for the rotor inertia of the drive motor to contribute to the vehicle's NV performance, the clutch is engaged and the drive motor is connected to the power transmission path, and rotor inertia is added, thereby improving NV performance. This makes it possible to reduce torsional vibrations that affect the vehicle's NV performance while simultaneously improving the vehicle's driving performance and fuel efficiency. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows a schematic configuration of a hybrid vehicle to which the present invention is applied, along with an electronic control unit. [Figure 2] Figure 1 illustrates the relationship between the gear stages of the automatic transmission and the equivalent inertia of the engine shaft in the power transmission system shown. [Figure 3] Figure 1 illustrates the relationship between engine speed and drive shaft torque fluctuations in the power transmission system shown in Figure 1. [Figure 4] Figure 5 illustrates the engagement and disengagement regions of the clutch control unit, which operates in relation to the relationship between engine speed and engine torque in the power transmission system shown in Figure 1. [Figure 5] Figure 1 is a flowchart illustrating the key aspects of the control operation of the electronic control unit. [Modes for carrying out the invention]

[0010] In the present invention, a drive unit having an engine and a first electric motor may be provided in place of the engine. In this case, the drive electric motor may be referred to as a second electric motor.

[0011] Furthermore, the drive motor may be installed on the output shaft of the automatic transmission, the propeller shaft, the input shaft (drive pinion) of the differential gear unit, or the pair of output shafts (drive shafts) of the differential gear unit. When installed on the pair of output shafts of the differential gear unit, the drive motor consists of a pair of motors, one for each of the pair of output shafts of the differential gear unit.

[0012] The hybrid vehicle of the present invention is a hybrid vehicle based on a front-engine, rear-wheel-drive (FR) system, but it may also be a vehicle based on a front-engine, front-wheel-drive (FF) system, or a four-wheel-drive vehicle equipped with a transfer case after the automatic transmission. [Examples]

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a diagram illustrating the drive system of a hybrid vehicle 10 to which the present invention is applied, and also shows the main parts of the control functions for various controls in the hybrid vehicle 10.

[0014] The hybrid vehicle 10 is equipped with, in order, an engine 12, an automatic transmission 14, a propeller shaft 16, a differential gear 18, a pair of drive shafts 20, and drive wheels (rear wheels) 22. The propeller shaft 16, which connects the automatic transmission 14 and the differential gear 18, is connected to a drive motor MG via a reduction gear pair 24 and a disengagement clutch 26. The reduction gear pair 24 consists of a large-diameter gear 24a fixed to the propeller shaft 16 and a small-diameter gear 24b that meshes with the large-diameter gear 24a. The disengagement clutch 26 is, for example, a meshing clutch or a friction clutch, and is provided between the small-diameter gear 24b and the drive motor MG.

[0015] The automatic transmission 14 is a stepped transmission configured to selectively switch between, for example, a gear ratio ρ1 for 1st gear and a gear ratio ρ10 for 10th gear by different combinations of the differentials of the friction engagement devices. The gear ratio ρ is Nin / Nout, where Nin is the input rotational speed and Nout is the output rotational speed of the automatic transmission 14.

[0016] The drive motor MG is a rotating electric machine, and is composed of a well-known motor-generator that functions as both an electric motor and a generator. The inertia of the rotor of the drive motor MG, when converted to the engine shaft of the engine 12, increases as the gear stage of the automatic transmission 14 is a high gear stage, that is, as the gear ratio ρ is small, and this affects the driving performance and fuel efficiency when accelerating with engine torque Te, which tends to decrease.

[0017] In the hybrid vehicle 10, the equivalent inertia J1 can be expressed by the following formula (1), where I1 is the inertia of the gear shaft system on the engine 12 side including the automatic transmission 14, and I2 is the inertia of the driven side including the inertia of the rotor of the driving electric motor MG. Figure 2 shows the relationship between the gear stage of the automatic transmission 14 and the equivalent inertia J1. When the disconnect clutch 26 is in the off (motor disengaged) state, it is shown as a zero value, and when the disconnect clutch 26 is in the on (motor engaged) state, it is shown as a curve. J1 = I1 + (1 / ρ 2 )I2 ···(1)

[0018] Also, the magnitude of the equivalent inertia J1 affects the NV performance of the hybrid vehicle 10. Figure 3 shows the DS torque fluctuation (dB) of the drive shaft 20 with respect to the engine speed Ne when the hybrid vehicle 10 is running with the engine at the 8-speed gear stage. When the disconnect clutch 26 is in the off (motor disengaged) state, it is shown as a dashed line, and when the disconnect clutch 26 is in the on (motor engaged) state, it is shown as a solid line. The target value L in Figure 3 indicates the maximum value (allowable value) of the DS torque fluctuation (dB) that can tolerably satisfy the NV (noise / vibration) performance. In Figure 3, in the range where the engine speed Ne is 1000 to 1330 (rpm), the DS torque fluctuation (dB) in the off (motor disengaged) state of the disconnect clutch 26 exceeds the target value L, but when the disconnect clutch 26 is in the on (motor engaged) state, it becomes below the target value L, indicating the motor engagement region (NV performance, the rotation region where it is necessary to set the disconnect clutch 26 in the on (motor engaged) state) MC. In this rotation region, it shows that satisfactory NV performance can be obtained when the disconnect clutch 26 is in the on (motor engaged) state during engine running when the torque of the driving electric motor MG does not occur.

[0019] In contrast, in FIG. 3, in the range where the engine speed Ne is high starting from 1330 (rpm), the DS torque fluctuation (dB) in the disengaged (motor disengaged) state of the on-off clutch 26 does not exceed the target value L, and a rotational region (motor disengaged region MD) where it is possible to set the on-off clutch 26 to the disengaged (motor disengaged) state is shown. In this rotational region, during engine running when the torque of the drive motor MG does not occur, by setting the on-off clutch 26 to the disengaged (motor disengaged) state, the equivalent inertia J1 can be reduced, and the running (acceleration) performance and fuel consumption performance of the hybrid vehicle 10 can be improved.

[0020] FIG. 4 shows a relationship obtained experimentally in advance. In the two-dimensional coordinates of the engine torque Te with respect to the engine speed Ne when the hybrid vehicle 10 is running with the engine in the 8-speed gear position, the motor engaged region MC and the motor disengaged region MD are shown two-dimensionally. The motor engaged region MC and the motor disengaged region MD are set in the region where the engine speed Ne of the engine 12 is Ne1 or higher. As the engine torque Te increases, the ratio of the motor engaged region MC increases and the ratio of the motor disengaged region MD decreases. By setting the relationship as shown in FIG. 4 for each gear position and storing it in advance, it becomes possible to determine the engagement and disengagement of the on-off clutch 26 based on the engine speed Ne, the engine torque Te, and the gear position of the automatic transmission 14.

[0021] The hybrid vehicle 10 includes an electronic control unit 100 as a control device for controlling the operations of each part such as the engine 12, the automatic transmission 14, the drive motor MG, and the on-off clutch 26. The electronic control unit 100 includes a so-called microcomputer and performs various controls by performing signal processing according to a program stored in advance.

[0022] The electronic control unit 100 is supplied with various information necessary for control from various sensors installed in the hybrid vehicle 10. For example, signals are supplied that represent the engine speed Ne (rpm) of the engine 12, the MG speed Nmg (rpm) of the drive motor MG, the input speed Nin (rpm) of the automatic transmission 14, the AT output speed Nout (vehicle speed V) of the automatic transmission 14, the accelerator opening θacc (%) corresponding to the amount of accelerator pedal depression, and the throttle valve opening θth (%) of the electronic throttle valve of the engine 12.

[0023] The electronic control unit 100 calculates the required drive torque based on, for example, the accelerator opening θacc and the vehicle speed V, and determines an engine driving mode or an electric motor driving mode based on the required drive torque from a pre-stored driving mode map so that the required drive torque is obtained with minimum fuel consumption. It then controls the engine torque Te and MG torque Tmg for engine driving, or the MG torque Tmg for electric motor driving. Through this control, the engine 12 of the hybrid vehicle 10 is operated intermittently. The electronic control unit 100 also performs gear shift control of the automatic transmission 14 according to a predetermined gear shift map. In the electric motor driving mode, the automatic transmission 14 is set to neutral, and electric motor driving is performed using only the drive electric motor MG as the drive source.

[0024] The electronic control device 100 functionally includes a disengagement determination unit 102 that determines the disengagement of the disengagement clutch 26 based on the engine speed Ne, engine torque Te, and gear position of the automatic transmission 14, using pre-stored relationships for each gear as shown in Figure 3, and a disengagement clutch control unit 104 that controls the disengagement state of the disengagement clutch 26 so that the disengagement state of the disengagement clutch 26 determined by the disengagement determination unit 102 is obtained.

[0025] The engagement / disengagement determination unit 102 determines that the engagement / disengagement clutch 26 is in the engaged state when torque from the drive motor MG is required for driving, while determining that the engagement / disengagement clutch 26 is in the disengaged state when torque from the drive motor MG is not required and there is no need for the rotor inertia of the drive motor MG to contribute to the vehicle's NV performance, for example, when the engine speed Ne etc. is within the motor non-engagement region MD in Figure 4 and the engine is running at high speed. The engagement / disengagement determination unit 102 determines that the engagement / disengagement clutch 26 is in the engaged state when there is a need for the rotor inertia of the drive motor MG to contribute to the vehicle's NV performance, for example, when the engine speed Ne etc. is within the motor engagement region MC in Figure 4.

[0026] As a result, the disengagement clutch control unit 104 connects the drive motor MG to the propeller shaft (power transmission path) 16 by engaging the disengagement clutch 26 when torque from the drive motor MG is required, thereby satisfying the required drive torque. On the other hand, when torque from the drive motor MG is not required and it is not necessary for the rotor inertia of the drive motor MG to contribute to the vehicle's NV performance, the disengagement clutch 26 is disengaged, disconnecting the drive motor MG from the propeller shaft (power transmission path) 16 to improve driving (acceleration) performance and fuel efficiency. However, when it is necessary for the rotor inertia of the drive motor MG to contribute to the vehicle's NV performance, the disengagement clutch 26 is engaged, connecting the drive motor MG to the propeller shaft (power transmission path) 16, thereby improving NV performance.

[0027] Figure 5 is a flowchart illustrating the key parts of the control operation of the electronic control unit 100. In the control operation of Figure 5, step S1 (hereinafter, steps will be omitted), which corresponds to the function of the disconnection / disconnection determination unit 102, determines whether or not the output torque of the drive motor MG is required. If the determination in S1 is negative, then in S2, which corresponds to the function of the disconnection / disconnection determination unit 102, it is determined whether or not NV performance is required. If the determination in S1 is positive, in S3, which corresponds to the function of the disconnection / disconnection clutch control unit 104, the disconnection / disconnection clutch 26 is set to the connected state and the drive motor MG is connected to the propeller shaft 16. If the determination in S2 is positive, in S3, the disconnection / disconnection clutch 26 is set to the connected state and the drive motor MG is connected to the propeller shaft 16. However, if the determination in S2 is negative, in S4, which corresponds to the function of the disconnection / disconnection clutch control unit 104, the disconnection / disconnection clutch 26 is set to the disconnected state and the drive motor MG is disconnected from the propeller shaft 16.

[0028] As described above, according to the electronic control device (control device) 100 of the hybrid vehicle 10 of this embodiment, the disengagement clutch control unit 104 engages the disengagement clutch 26 when torque from the drive motor MG is required, connecting the drive motor MG to the propeller shaft (power transmission path) 16 and satisfying the required drive torque. On the other hand, when torque from the drive motor MG is not required and it is not necessary for the rotor inertia of the drive motor MG to contribute to the vehicle's NV performance, the disengagement clutch 26 is disengaged, disconnecting the drive motor MG from the propeller shaft (power transmission path) 16 and improving driving (acceleration) performance and fuel efficiency. However, when it is necessary for the rotor inertia of the drive motor MG to contribute to the vehicle's NV performance, the disengagement clutch 26 is engaged, connecting the drive motor MG to the propeller shaft (power transmission path) 16, and the rotor inertia is added, improving NV performance. This makes it possible to reduce torsional vibrations that affect the vehicle's NV performance while simultaneously improving the vehicle's driving performance and fuel efficiency.

[0029] Although embodiments of the present invention have been described in detail above with reference to the drawings, these are merely examples, and the invention can be implemented in various modified and improved forms. [Explanation of Symbols]

[0030] 10: Hybrid vehicle, 12: Engine, 14: Automatic transmission, 16: Propeller shaft (power transmission path), 22: Drive wheels, 26: Disconnecting clutch, 100: Electronic control unit (control unit), 104: Disconnecting clutch control unit, MG: Drive motor

Claims

[Claim 1] A control device for a hybrid vehicle that sequentially includes an automatic transmission and a drive motor in the power transmission path from the engine to the drive wheels, A disconnection clutch that connects and disconnects the drive motor and the power transmission path, The system includes a clutch control unit that, when torque from the drive motor is required, engages the clutch to connect the drive motor to the power transmission path, while disengaging the clutch to disconnect the drive motor from the power transmission path when torque from the drive motor is not required and the rotor inertia of the drive motor does not need to contribute to the vehicle's NV performance, but engaging the clutch to connect the drive motor to the power transmission path when the rotor inertia of the drive motor does need to contribute to the vehicle's NV performance. A control device for a hybrid vehicle characterized by the following features.

Images