Hybrid vehicle driving control device

Abstract

To provide a travel control device of a hybrid vehicle which achieves both of improvement of fuel consumption performance and followability to a preceding vehicle in an ACC function.SOLUTION: A travel control device of a hybrid vehicle (1) has an ACC function in which the vehicle travels at a constant speed according to a target vehicle speed when there is no preceding vehicle on an own vehicle line and follows the preceding vehicle in accordance with target inter-vehicle time when there is the preceding vehicle on the own vehicle line. When the preceding vehicle during follow-up is accelerated, the travel control device is configured (i) to execute acceleration control by a first torque request (T1) determined according to acceleration of the preceding vehicle in an engine travel mode or a HEV travel mode, and (ii) to execute acceleration control by a second torque request (T2) determined according to acceleration of the preceding vehicle in an EV travel mode. The second torque request (T2) rises with inclination larger than that of the first torque request.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a driving control device for a hybrid vehicle, and more particularly to a driving control device for a hybrid vehicle having an ACC function.

Background Art

[0002] In a hybrid vehicle equipped with an engine and a motor in the drive system, by switching between an engine running mode in which the vehicle runs only with the driving force of the engine, an EV running mode in which the vehicle runs only with the driving force of the motor, and an HEV running mode in which the vehicle runs with the driving forces of the engine and the motor, control is required to obtain running performance and fuel consumption performance according to the situation.

[0003] For example, in Patent Document 1, in a hybrid vehicle having an inter-vehicle distance control function, in order to increase the acceleration response by utilizing the control responsiveness of the motor and improve the followability to the preceding vehicle, the higher the driving force distribution ratio of the motor to the required driving force as the inter-vehicle distance to the preceding vehicle becomes shorter is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in a full hybrid vehicle as well as in a mild hybrid vehicle that uses the power of the motor supplementarily, it is advantageous for improving fuel consumption performance to shift to the EV running mode in the low speed range. That is, it shifts to the EV running mode in a decelerating state to perform regenerative braking, and the EV running mode is maintained even when it stops after deceleration. It starts in the EV running mode at the time of starting, but shifts to the HEV running mode when the accelerator is turned on.

[0006] However, in a vehicle or a full hybrid vehicle with a small motor output as described above, when starting to follow a preceding vehicle by means of an ACC (Adaptive Cruise Control) function, the torque of the motor alone is insufficient, and sufficient acceleration cannot be obtained immediately after starting, resulting in a problem in the followability to the preceding vehicle.

[0007] The present invention has been made in view of the above actual situation, and an object thereof is to provide a driving control device for a hybrid vehicle that achieves both improved fuel consumption performance and followability to a preceding vehicle in an ACC function.

Means for Solving the Problem

[0008] In order to solve the above problems, the present invention is provided with an engine and a motor in a drive system, and is provided with a control system for controlling the driving forces of the engine and the motor, an engine driving mode in which the vehicle runs only with the driving force of the engine, an EV driving mode in which the vehicle runs only with the driving force of the motor, a HEV driving mode in which the vehicle runs with the driving forces of the engine and the motor, and is a driving control device for a hybrid vehicle capable of selectively executing In a case where there is no preceding vehicle in the own lane, the vehicle performs constant-speed driving according to a target vehicle speed, and in a case where there is a preceding vehicle in the own lane, the vehicle has an ACC function of following the preceding vehicle according to a target inter-vehicle time. When the preceding vehicle being followed accelerates by means of the ACC function, in the engine driving mode or the HEV driving mode, acceleration control is executed according to a first torque request determined according to the acceleration of the preceding vehicle, and in the EV driving mode, it is configured to execute acceleration control according to a second torque request determined according to the acceleration of the preceding vehicle, wherein the second torque request rises with a slope greater than that of the first torque request.

Effects of the Invention

[0009] As described above, when the preceding vehicle being followed accelerates by the ACC function, the driving control device for a hybrid vehicle according to the present invention executes acceleration control with a torque request that rises with a steeper slope in the EV driving mode than in the engine driving mode and the HEV driving mode. Therefore, the timing of switching from the EV driving mode to the HEV driving mode is advanced, which is advantageous for improving the followability to the preceding vehicle from the EV driving mode.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, a vehicle 1 is a hybrid vehicle equipped with an internal combustion engine 2 and a motor 3 in a drive system, and includes an engine controller 20 that controls the engine 2 and an HEV controller 30 that controls the motor 3 in cooperation with the engine controller 20.

[0012] Vehicle 1 is a mild hybrid vehicle equipped with an ISG (Integrated Starter Generator) that can be directly connected to the crankshaft of engine 2 or transmit driving force via a belt as motor 3. In addition to restarting engine 2 and regenerative power generation by motor 3, it can run in an engine running mode where it runs only with the driving force of engine 2, an HEV running mode where it runs with the driving force of engine 2 and the driving force of motor 3, and an EV running mode where it runs only with the driving force of motor 3 by deactivating the cylinders of engine 2.

[0013] Vehicle 1 is equipped with a brake controller 40 that controls the braking force of the brake 4 of each wheel via a brake actuator, and a wheel speed sensor 14 that can individually detect the speed of each wheel, and is equipped with a brake system that constitutes an ABS / vehicle behavior stabilization device.

[0014] Furthermore, vehicle 1 is equipped with an ACC controller 10 that comprehensively controls the engine controller 20, the HEV controller 30, and the brake controller 40, and is equipped with a preceding vehicle detection means 11 that constitutes an ACC system together with this ACC controller 10.

[0015] The preceding vehicle detection means 11 has a function of detecting the presence of a preceding vehicle or an object (obstacle, structure) in front of the host vehicle, such as a millimeter-wave radar, a stereo camera, or a LIDAR, and can use one or more detection means capable of measuring the relative distance between the preceding vehicle or obstacle and the host vehicle. The measurement of the relative distance is dynamically executed at a predetermined time rate, and the relative speed of the preceding vehicle with respect to the host vehicle is obtained as the change in the relative distance per unit time, and the acceleration / deceleration of the preceding vehicle is obtained.

[0016] Note that the engine controller 20, HEV controller 30, brake controller 40, and ACC controller 10 are all composed of a microcomputer (MCU) or an electronic control unit (ECU) including a ROM that stores control programs and setting data, a RAM that temporarily stores arithmetic processing results, a CPU that performs arithmetic processing, a communication I / F, etc., and are connected to be mutually communicable via a vehicle-mounted network (such as CAN) together with a sensor group including the preceding vehicle detection means 11 and the wheel speed sensor 14.

[0017] Based on the detection information of the preceding vehicle detection means 11 and the vehicle speed calculated from the detection value of the wheel speed sensor 14, the ACC controller 10 issues acceleration / deceleration commands to the engine controller 20, HEV controller 30, and brake controller 40 instead of the driver's accelerator / brake operation, and can execute full vehicle speed range adaptive cruise control (constant speed driving / following driving control / deceleration stop and restart control).

[0018] That is, during the operation of the ACC function, the vehicle 1 drives at a constant speed according to the target vehicle speed when there is no preceding vehicle in its own lane, follows the preceding vehicle according to the target inter-vehicle time when there is a preceding vehicle in its own lane, decelerates and stops while maintaining the set inter-vehicle distance when the preceding vehicle decelerates and stops, and restarts when the preceding vehicle starts, according to the acceleration / deceleration commands from the ACC controller 10.

[0019] Even during the operation of the ACC function, the vehicle 1 drives in the EV driving mode as much as possible to improve fuel consumption performance, and switches to the HEV driving mode when the torque of the motor 3 is insufficient for the acceleration command from the ACC controller 10.

[0020] For example, during following driving in the EV driving mode, when an acceleration command (torque request) is issued from the ACC controller 10 due to the acceleration of the preceding vehicle, the HEV controller 30 operates the motor 3 according to the requested torque to accelerate the vehicle 1. When the torque request value from the ACC controller 10 exceeds the threshold value, the HEV controller 30 switches from the EV driving mode to the HEV driving mode, starts the engine 2 by the engine controller 20, and accelerates the vehicle 1 by the driving force of the engine 2.

[0021] Also, during driving in the HEV driving mode, when a deceleration command (brake request) is issued from the ACC controller 10 due to the deceleration of the preceding vehicle or the like, the HEV controller 30 switches the motor 3 to the regeneration mode to perform regenerative braking. For a brake request exceeding the regenerative braking, the brake controller 40 decelerates the vehicle 1 by generating the braking force of the brake 4 by the brake actuator.

[0022] Furthermore, the HEV controller 30 switches from the HEV driving mode to the EV driving mode in the deceleration state, and the engine controller 20 stops the operation of the engine 2. After that, when stopping from the deceleration state due to the stop of the preceding vehicle, the engine 2 is maintained in the stopped state, and the EV driving mode is maintained even during parking.

[0023] When the preceding vehicle starts from such a stopped state, an acceleration command is issued from the ACC controller 10, and the HEV controller 30 starts the vehicle 1 by the driving force of the motor 3. In such a situation, during normal driving, it shifts to the HEV driving mode by turning on the accelerator and the engine 2 starts. However, when the ACC function is operating, the HEV controller 30 switches from the EV driving mode to the HEV driving mode and starts the engine 2 when the actual torque (current value) by the driving of the motor 3 exceeds the threshold value. Therefore, in a mild hybrid vehicle that supplementarily uses the driving force of the motor 3, there has been a problem that the acceleration immediately after restarting is delayed only by the driving force of the motor 3.

[0024] Therefore, when the preceding vehicle being followed by the ACC function accelerates, the ACC controller 10 according to the present invention executes acceleration control with a first torque request T1 if the vehicle 1 is in (i) the engine running mode or the HEV running mode, and executes acceleration control with a second torque request T2 if the vehicle 1 is in (ii) the EV running mode.

[0025] Both the first and second torque requests T1 and T2 are given by a torque map that is dynamically determined according to the acceleration (relative speed) of the preceding vehicle. However, as shown in FIG. 5(a), (i) In the first torque request T1, an upper limit value is provided for the slope in order to suppress rapid torque fluctuations, whereas (ii) The second torque request T2 has a torque map including a first section T2a that rises with a slope greater than that of the first torque request T1 and a second section T2b that rises with a slope smaller than that of the first torque request T1 and transitions to the same torque request value as the first torque request T1.

[0026] It is more preferable that, as shown in FIG. 5(a), the second section T2b further includes a section T2c that transitions to the same torque request value as the first torque request T1 with a negative slope.

[0027] By executing acceleration control with the second torque request T2 as described above, in the control of the HEV controller 30 described above, the switching timing from the EV running mode to the HEV running mode is advanced, and by quickly shifting to running mainly with the driving force of the engine 2, the followability to the preceding vehicle is improved.

[0028] In particular, by issuing a torque request greater than a predetermined torque request value (the same as the first torque request T1) at the start of control, once raising the actual torque above the predetermined torque request value and then transitioning to the predetermined value, it is possible to further improve the followability to the preceding vehicle while preventing sudden acceleration that would make the driver feel uncomfortable.

[0029] (First Embodiment) Figure 2 is a flowchart corresponding to the control in the first embodiment of the present invention. In Figure 2, during the operation of the ACC function (step 100), the acceleration of the preceding vehicle being followed by the ACC function, that is, the increase rate of the inter-vehicle time, is constantly monitored (step 111). When it is detected that the acceleration of the preceding vehicle (increase rate of the inter-vehicle time) has become equal to or greater than the threshold value a0, (i) If vehicle 1 is in a mode other than the EV driving mode (step 112, NO), acceleration control is executed by the first torque request T1 (step 121), (ii) If vehicle 1 is in the EV driving mode (step 112, YES), acceleration control is executed by the second torque request T2 (step 122).

[0030] After any of the above steps is executed, if the respective end conditions are satisfied, one flow ends (step 130). However, during the operation of the ACC function, this flow is constantly executed.

[0031] Note that the above threshold value a0 can simply be a positive value (a0 > 0), but from the viewpoint of control stability, it is preferably a significant value. Also, the threshold value a0 may be dynamically set according to the vehicle speed. In particular, when the vehicle speed is zero, that is, at the time of restart, it is preferably set to a value that excludes the case where the acceleration of the preceding vehicle is small.

[0032] (Second Embodiment) Figure 3 is a flowchart corresponding to the control in the second embodiment of the present invention, showing a mode in which different controls are executed when restarting from a state of decelerating and stopping while following a preceding vehicle and when re-accelerating while following a preceding vehicle and driving. In Figure 3, during the operation of the ACC function (step 100), the acceleration of the preceding vehicle being followed by the ACC function, that is, the increase rate of the inter-vehicle time, is constantly monitored (step 111). When it is detected that the acceleration (increase rate of the inter-vehicle time) of the preceding vehicle has become equal to or greater than the threshold value a0, (i) If the vehicle 1 is not in the EV driving mode (step 112, NO), or if the vehicle speed of the vehicle 1 > 0 km / h, i.e., it is in motion (step 113, NO), acceleration control is executed by the first torque demand T1 (step 121). (ii) If the vehicle 1 is in the EV driving mode (step 112, YES), and if the vehicle speed of the vehicle 1 is 0 km / h, i.e., it is stopped, at the time when the acceleration of the preceding vehicle is detected (step 113, YES), acceleration control is executed by the second torque demand T2 (step 122).

[0033] In step 122, after starting from a stopped state in the EV driving mode (step 140), when the actual torque reaches the predetermined threshold value T3 (step 141), the HEV controller 30 switches to the HEV driving mode (step 142), and the engine controller 20 starts the engine 2, thereby ending the EV driving mode (step 143).

[0034] After either of steps 121 and 122 is executed, if the respective end conditions are satisfied, one cycle of the flow ends (step 130). However, while the ACC function is operating, this flow is continuously executed.

[0035] Note that the threshold value (0 km / h) for determining the stopped state of the vehicle 1 can also be a value (for example, 1 to 3 km / h) that can be regarded as a substantially stopped state.

[0036] In the acceleration control according to this second embodiment, when the vehicle is stopped in the EV driving mode and an acceleration command is issued from the ACC controller 10 due to the start of the preceding vehicle, and when following the preceding vehicle and restarting, acceleration control is executed by the second torque demand T2. As a result, as indicated by reference numeral T2' in FIG. 5(a), the switching timing from the EV driving mode to the HEV driving mode is advanced, and an early transition is made to acceleration by the driving force of the engine 2, so that the rise of the actual torque T2' becomes faster. As a result, as indicated by reference numeral A2 in FIG. 5(b), the rise of the acceleration also becomes faster, and the followability to the preceding vehicle is improved.

[0037] On the other hand, when the vehicle is running in the EV driving mode and an acceleration command is issued from the ACC controller 10 due to the re-acceleration of the preceding vehicle or the like and the vehicle needs to re-accelerate, since it can follow the preceding vehicle with a lower torque compared to the case of restarting from a stopped state, the process of rapidly increasing the torque demand value is not performed, and by switching from the EV driving mode to the HEV driving mode at the normal timing, control that prioritizes fuel efficiency performance and ride comfort can be executed.

[0038] (Third Embodiment) FIG. 4 shows a flowchart corresponding to the control in the third embodiment of the present invention. This third embodiment is the same as the second embodiment in that different controls are executed depending on whether the vehicle restarts from a state of decelerating and stopping while following the preceding vehicle or re-accelerates while running while following the preceding vehicle, but is different in that acceleration control is executed in consideration of the target inter-vehicle time TG in the ACC function.

[0039] When the ACC controller 10 can selectively set the target inter-vehicle time (TG = inter-vehicle distance / vehicle speed) when following the preceding vehicle in multiple steps, for example, in three steps of short (TG1), medium (TG2), and long (TG3), as shown in FIG. 4, when the target inter-vehicle time TG is set to the short side "short (TG1)" within its set range when the ACC function is activated (step 100) (step 101, YES), the control below step 111 is executed.

[0040] That is, when it is detected that the acceleration of the preceding vehicle (the increase rate of the inter-vehicle time) has become equal to or greater than the threshold value a0 (step 111, YES), (i) If the vehicle 1 is not in the EV driving mode (step 112, NO), or if the vehicle speed of the vehicle 1 > 0 km / h, that is, if it is running (step 113, NO), acceleration control is executed by the first torque demand T1 (step 121), (ii) When the vehicle 1 is in the EV driving mode (step 112, YES), and the vehicle speed of the vehicle 1 is 0 km / h, that is, the vehicle is stopped, when the acceleration of the preceding vehicle is detected (step 113, YES), acceleration control is executed by the second torque request T2 (step 122).

[0041] And, if after a predetermined time (for example, 2 to 3 seconds) has elapsed since the second torque request T2 is issued, the acceleration A0 (the increase rate of the inter-vehicle time) of the preceding vehicle is equal to or greater than a predetermined threshold value a1 (step 123, YES), the acceleration control by the second torque request T2 is continued (step 124). However, if the acceleration A0 of the preceding vehicle does not reach the predetermined threshold value a1 even after the predetermined time has elapsed (step 123, NO), the acceleration control switches to the acceleration control by the first torque request T1.

[0042] After that, one cycle of the flow ends when the end conditions of each acceleration control (T1, T2) are satisfied (step 130). However, during the operation of the ACC function, the fact that this flow is continuously executed is the same as in the previous embodiment.

[0043] In the acceleration control according to this third embodiment, when a short target inter-vehicle time TG1 is set within the set range of the target inter-vehicle time (target inter-vehicle distance), it can be considered that the driver intends to emphasize followability. Therefore, in such a case, the switching timing from the EV driving mode to the HEV driving mode is advanced, and control is performed to shift to acceleration by the driving force of the engine 2 at an early stage, and by improving the acceleration performance and the followability to the preceding vehicle, driving that suits the driver's preference can be realized.

[0044] Also, when the acceleration A0 (the increase rate of the inter-vehicle time) of the preceding vehicle does not reach the predetermined threshold value a1 even after the predetermined time has elapsed, by switching to the acceleration control by the first torque request T1, over-approaching and unnecessary braking in a situation where a short target inter-vehicle time TG1 is set can be suppressed.

[0045] In the above-described embodiment, the case where the vehicle 1 is a mild hybrid vehicle has been described. However, the control device according to the present invention can also be implemented in a full hybrid vehicle that obtains the maximum output in the HEV running mode in which the vehicle runs with the driving forces of the engine 2 and the motor 3.

[0046] As described above, some embodiments of the present invention have been described. It should be noted that the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.

Explanation of Reference Numerals

[0047] 1 Vehicle 2 Engine 3 Motor 4 Brake 10 ACC Controller 11 Preceding Vehicle Detection Means 14 Wheel Speed Sensor 20 Engine Controller 30 HEV Controller 40 Brake Controller

Claims

1. A hybrid vehicle travel control device that includes an engine and a motor in a drive system, and includes a control system for controlling the driving force of the engine and the motor, and has an engine travel mode in which the vehicle travels only with the driving force of the engine, an EV travel mode in which the vehicle travels only with the driving force of the motor, and an HEV travel mode in which the vehicle travels with the driving force of the engine and the driving force of the motor, and is selectively executable, and has an ACC function that performs constant-speed travel according to a target vehicle speed when there is no preceding vehicle in the own lane, and follows the preceding vehicle according to a target inter-vehicle time when there is a preceding vehicle in the own lane. In this case, when the preceding vehicle being followed by the ACC function accelerates, in the engine travel mode or the HEV travel mode, acceleration control is executed according to a first torque request determined according to the acceleration of the preceding vehicle, and in the EV travel mode, it is configured to execute acceleration control according to a second torque request determined according to the acceleration of the preceding vehicle, wherein the second torque request rises with a slope greater than that of the first torque request. Hybrid vehicle travel control device.

2. The control system is capable of executing control to shift to the EV travel mode when the actual torque becomes less than a predetermined threshold value, and to shift to the HEV travel mode when the actual torque becomes greater than or equal to the predetermined threshold value during travel in the EV travel mode. The hybrid vehicle travel control device according to claim 1, characterized in that.

3. The acceleration control according to the second torque request is executed when the preceding vehicle being followed by the ACC function accelerates and the preceding vehicle starts moving while the own vehicle has stopped in the EV travel mode due to the stop of the preceding vehicle. The hybrid vehicle travel control device according to claim 2, characterized in that.

4. The acceleration control in the EV travel mode according to the second torque request is executed when the target inter-vehicle time in the ACC function is less than or equal to a predetermined value within its set range. The hybrid vehicle travel control device according to any one of claims 1 to 3, characterized in that.

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