Vehicle braking control device

Abstract

To prevent drivability from deteriorating so that wheel locking and hunting of a restoration of locking do not occur.SOLUTION: A braking control device 100 of a vehicle controls the vehicle equipped with a regenerative braking device (a motor generator) 2 that generates regenerative braking force, which comprises: an inertial travelling determination part 101 that determines whether the vehicle is inertially travelling or not; a wheel locking determination part 102 that determines whether a wheel is locked or not; and a control part 103 that suppresses regenerative braking force that is generated by the regenerative braking device 2, after the inertial travelling determination part 101 determines that the vehicle is inertially travelling and the wheel locking determination part 102 determines that the wheel is locked, until the inertial travelling determination part 101 determines that the vehicle is not inertially travelling and the wheel locking determination part 102 determines that the wheel is not locked.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a braking control device for a vehicle. [Background technology]

[0002] Regarding a vehicle braking control device, Patent Document 1 discloses a technology for quickly eliminating slippage by performing vehicle stability control that adjusts the regenerative braking force applied to the front wheels based on an estimated road surface μ value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-103917 Summary of the Invention [Problem to be solved by the invention]

[0004] In vehicles equipped with a regenerative braking device that generates regenerative braking force, the wheels may lock due to the regenerative braking force when coasting onto a low-friction road. Coasting refers to driving without the driver pressing the accelerator or brake pedal. In the conventional technology disclosed in Patent Document 1, when a wheel locks during coasting, the regenerative braking force is suppressed to recover from the locked wheel. However, if coasting continues in this case, the wheels may recover from locking and the suppression of regenerative braking force may be released, causing the wheels to lock again. This may result in hunting of the wheels locking and recovering from locking, and deteriorating drivability.

[0005] The present invention has been made in view of the above circumstances, and has as its object to prevent deterioration of drivability by preventing hunting due to wheel locking and recovery from locking. [Means for solving the problem]

[0006] The vehicle braking control device of the present invention is a vehicle braking control device for controlling a vehicle equipped with a regenerative braking device that generates regenerative braking force, and includes: coasting determination means for determining whether or not the vehicle is coasting; wheel lock determination means for determining whether or not a wheel is locked; and control means for suppressing the regenerative braking force generated by the regenerative braking device from the time when the coasting determination means determines that the vehicle is coasting and the wheel lock determination means determines that the wheel is locked, until the coasting determination means determines that the vehicle is not coasting and the wheel lock determination means determines that the wheel is not locked. The coasting determination means determines whether the vehicle is coasting based on the driver's intention to decelerate, and the driver's intention to decelerate is determined based on a deceleration operation by depressing a brake pedal. It is characterized by: [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent hunting due to wheel locking and recovery from locking, thereby preventing deterioration of drivability. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a main part of an automobile according to an embodiment; [Figure 2] 1 is a diagram showing a functional configuration of a braking control device for a vehicle according to an embodiment; [Figure 3] 3 is a flowchart showing a process executed by a braking control device for a vehicle according to an embodiment. [Figure 4] 4 is a time chart showing time series changes in wheel speed and regenerative braking force during coasting; DETAILED DESCRIPTION OF THE INVENTION

[0009] A vehicle braking control device according to one embodiment of the present invention is a vehicle braking control device that controls a vehicle equipped with a regenerative braking device that generates regenerative braking force, and is characterized by comprising: a coasting determination means that determines whether the vehicle is coasting; a wheel lock determination means that determines whether the wheels are locked; and a control means that suppresses the regenerative braking force generated by the regenerative braking device from the time the coasting determination means determines that the vehicle is coasting and the wheel lock determination means determines that the wheels are locked until the time the coasting determination means determines that the vehicle is not coasting and the wheel lock determination means determines that the wheels are not locked. This prevents hunting due to wheel locking and recovery from locking, thereby preventing deterioration of drivability. [Example]

[0010] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. [Example 1] FIG. 1 shows a schematic configuration of the main parts of an automobile, which is a vehicle according to the embodiment. The automobile according to the embodiment is a hybrid vehicle equipped with an engine 1, which is an internal combustion engine, and a motor generator 2 that functions as an electric motor and a generator. The automobile includes a transmission 5 connected to a crankshaft 3 of an engine 1 and driving a driveshaft 4, and drive wheels 6 to which driving force is transmitted via the driveshaft 4. A wheel speed sensor 7 is installed on the driveshaft 4. The transmission 5 is an AMT (Automated Manual Transmission) and includes a clutch 8 connected to the crankshaft 3, a gearbox 9 to which the output of the clutch 8 is transmitted, and a differential 10 that transmits the output of the gearbox 9 to the driveshaft 4. The clutch 8 is switched between engagement and disengagement by an actuator 11. The transmission 9 also switches between gear positions by an actuator 12.

[0011] Furthermore, the motor generator 2 is connected to the transmission 5 downstream of the gearbox 9 via a power transmission mechanism 13. An inverter 14 and a battery (not shown) are connected to the motor generator 2. When the motor generator 2 is made to function as an electric motor, the driving force output from the motor generator 2 is input to the drive wheels 6. On the other hand, when the motor generator 2 is made to function as a generator, the motor generator 2 generates electricity according to the rotational speed of the drive wheels 6. At this time, a regenerative braking force (regenerative brake torque) can be generated and applied to the drive wheels 6. In this way, the motor generator 2 constitutes a regenerative braking device that generates a regenerative braking force.

[0012] The automobile includes an HCU (Hybrid Control Unit) 15 that controls the hybrid system, an ECU (Engine Control Unit) (not shown) that controls the engine 1 , and a TCM (Transmission Control Module) 16 that controls the transmission 5 . The HCU 15 controls the motor generator 2 via the inverter 14. The HCU 15 receives detection information from the wheel speed sensor 7 and various sensors 17. The TCM 16 controls the transmission 5. Specifically, the TCM 16 issues a command to the actuator 11 to control switching between engagement and disengagement of the clutch 8. The TCM 16 also issues a command to the actuator 12 to control switching of the gear positions of the transmission 9. Detection information is input to the TCM 16 from the wheel speed sensor 7 and various sensors 17. The various sensors 17 include pre-selected ones from among an accelerator pedal switch (accelerator pedal sensor), an accelerator opening sensor, a brake pedal switch (brake pedal sensor), a brake stroke sensor, a master pressure sensor, and a G sensor, as will be described later.

[0013] FIG. 2 shows a functional configuration of a vehicle braking control device 100 according to this embodiment. The vehicle braking control device 100 includes a coasting determination unit 101 that determines whether the vehicle is coasting or not, a wheel lock determination unit 102 that determines whether the wheels are locked or not, and a control unit 103 that controls the motor generator 2 that constitutes the regenerative braking device.

[0014] The coasting determination unit 101 determines whether the vehicle is coasting based on the driver's intention to accelerate, the driver's intention to decelerate, and the vehicle's stopped state. The presence or absence of the driver's intention to accelerate can be determined based on detection information from an accelerator pedal switch or detection information from an accelerator opening sensor. The intention to accelerate refers to the driver's acceleration operation by depressing the accelerator pedal. The presence or absence of the driver's intention to decelerate can be determined based on detection information from a brake pedal switch, detection information from a brake stroke sensor, or detection information from a master pressure sensor. The intention to decelerate refers to the driver's deceleration operation by depressing the brake pedal. The vehicle's stopped state can be determined based on detection information from the wheel speed sensor 7 or detection information from a G sensor.

[0015] The wheel lock determination unit 102 determines whether or not the wheels are locked based on the detection information of the wheel speed sensor 7 or the detection information of the G sensor.

[0016] The control unit 103 sets the regenerative braking force generated by the motor generator 2 to 0 after the coasting determination unit 101 determines that the vehicle is coasting and the wheel lock determination unit 102 determines that the wheels are locked, until the coasting determination unit 101 determines that the vehicle is not coasting and the wheel lock determination unit 102 determines that the wheels are not locked.

[0017] In the first embodiment, the vehicle braking control device 100 is realized by, for example, the HCU 15, but is not limited to this. For example, the function of the control unit 103 is realized by the HCU 15, but the functions of the coasting determination unit 101 and the wheel lock determination unit 102 may be realized by a unit other than the HCU 15 (for example, an ECU).

[0018] FIG. 3 is a flowchart showing the processing executed by the vehicle braking control device according to this embodiment. 3 starts when the coasting determination unit 101 determines that the vehicle is coasting and the wheel lock determination unit 102 determines that the wheels are locked. For example, when the vehicle enters a low μ road while coasting, the regenerative braking force generated by the motor generator 2 may lock the wheels. In step S1, the control unit 103 sets the regenerative braking force generated by the motor generator 2 to zero. In step S2, the control unit 103 maintains the process of step S1 until the wheel lock determination unit 102 determines that the wheels have recovered from lock, and if it is determined that the wheels have recovered from lock, the control unit 103 proceeds to step S3. In step S3, the control unit 103 maintains the process of step S1 until the coasting determination unit 101 determines that the vehicle is not coasting, and if it determines that the vehicle is not coasting, the control unit 103 advances the process to step S4. In step S4, the control unit 103 sets the regenerative braking force generated by the motor generator 2 to the normal regenerative braking force. As described above, after the coasting determination unit 101 determines that the vehicle is coasting and the wheel lock determination unit 102 determines that the wheels are locked, the regenerative braking force generated by the motor generator 2 is set to 0 until the coasting determination unit 101 determines that the vehicle is not coasting and the wheel lock determination unit 102 determines that the wheels are not locked.

[0019] Figure 4 shows the time series changes in wheel speed and regenerative braking force during coasting. FIG. 4(b) is a timing chart of the conventional technique. If the wheels lock while coasting (t1), the wheel speed will decrease. At this time, the regenerative braking force generated by the motor generator is set to zero (t2), the wheels are released from the locked state (t3), and then the suppression of the regenerative braking force is released (t4). In this case, because coasting continues, there is a risk that the wheels will lock again due to the regenerative braking force generated by the motor generator (t5). This can result in hunting as the wheels lock and then release the lock.

[0020] FIG. 4(a) is a timing chart in this embodiment. If the wheels lock during coasting (t1), the wheel speed decreases. At this time, the regenerative braking force generated by motor generator 2 is set to zero (t2), thereby recovering the locked wheels (t3). After that, the regenerative braking force is maintained at zero while coasting continues. As a result, it is possible to prevent hunting caused by the wheels locking and recovering from the locked state.

[0021] In this embodiment, an example has been described in which the regenerative braking force generated by the motor generator 2 is set to 0, but the regenerative braking force generated by the motor generator 2 may also be suppressed. Suppressing the regenerative braking force means making it lower than the regenerative braking force under normal conditions, and in the example of FIG. 4, it is made lower than the regenerative braking force indicated by characteristic line 401.

[0022] As described above, it is possible to prevent hunting due to wheel locking and recovery from locking, thereby preventing deterioration of drivability. Also, by suppressing regenerative braking, it is possible to suppress a decrease in the amount of power generated by the motor generator 2. Furthermore, torque-up control that drives the motor generator 2 to recover from wheel lock is also minimized, so power consumption by the motor generator 2 can be reduced. Wheel locking is not an issue during vehicle acceleration or when the vehicle is stopped, and wheel locking caused by brake pedal depression is controlled by a conventional anti-lock braking system (ABS).

[0023] [Example 2] Next, a description will be given of Example 2. In Example 2, the hybrid vehicle shown in Fig. 1 will also be described as an example, and the same components as those in Example 1 will be assigned the same reference numerals and their description will be omitted, while the description will focus on the differences from Example 1. In the first embodiment, braking control for the regenerative braking force generated by the motor generator 2 has been described, but similar braking control can also be performed for the braking force (engine brake torque) generated by resistance in the engine 1.

[0024] In the second embodiment, the vehicle braking control device 100 controls a braking force transmission mechanism that transmits braking force generated by the engine 1 to the wheels, such as the clutch 8 in FIG. 1. That is, in FIG. 2, the regenerative braking device (motor generator) 2 may be replaced with the braking force transmission mechanism. The control unit 103 suppresses the braking force transmitted by the clutch 8 from the time when the coasting determination unit 101 determines that the vehicle is coasting and the wheel lock determination unit 102 determines that the wheels are locked, until the time when the coasting determination unit 101 determines that the vehicle is not coasting and the wheel lock determination unit 102 determines that the wheels are not locked. For example, the clutch 8 is switched to a disengaged state so that the braking force is not transmitted.

[0025] Although the example has been given in which the clutch 8 is controlled as a braking force transmission mechanism, the transmission 9 may also be controlled. In this case, the control unit 103 suppresses the braking force transmitted by the transmission 9 from the time when the coasting determination unit 101 determines that the vehicle is coasting and the wheel lock determination unit 102 determines that the wheels are locked, until the time when the coasting determination unit 101 determines that the vehicle is not coasting and the wheel lock determination unit 102 determines that the wheels are not locked. For example, the transmission 9 is switched to a neutral gear position so that the braking force is not transmitted.

[0026] In the second embodiment, the vehicle braking control device 100 is realized by, for example, the TCM 16, but is not limited to this. For example, the function of the control unit 103 is realized by the TCM 16, but the functions of the coasting determination unit 101 and the wheel lock determination unit 102 may be realized by a unit other than the TCM 16 (for example, an ECU).

[0027] As described above, it is possible to prevent hunting due to wheel locking and recovery from locking, thereby preventing deterioration of drivability. Alternatively, the engine may be returned from the fuel cut and placed in an idling state to suppress the braking force (engine braking torque). These methods can suppress wheel lock caused by the braking force (engine braking torque), and therefore torque-up control that drives the engine 1 to recover from wheel lock can be minimized, thereby reducing fuel consumption by the engine 1.

[0028] In a hybrid vehicle such as that shown in FIG. 1, the first and second embodiments may be combined, that is, both the suppression of the regenerative braking force and the suppression of the braking force (engine brake torque) may be executed. Furthermore, although hybrid vehicles have been described in the first and second embodiments, as is clear from the first embodiment, the present invention can also be applied to electric vehicles, and as is clear from the second embodiment, the present invention can also be applied to engine vehicles.

[0029] Although the embodiments of the present invention have been described in detail above with reference to the drawings, each embodiment merely shows a specific example of how the present invention can be implemented. The technical scope of the present invention is not limited to each embodiment. Various modifications of the present invention are possible within the scope of the gist of the present invention, and these modifications are also included within the technical scope of the present invention. A vehicle braking control device to which the present invention is applied is configured by a computer device equipped with, for example, a CPU, a ROM, a RAM, etc., and the functions of each means are realized by the CPU executing a predetermined program stored in, for example, the ROM. Also, a vehicle braking control device to which the present invention is applied may be configured by a plurality of computers working together. [Explanation of symbols]

[0030] 1: engine, 2: motor generator, 5: transmission, 7: wheel speed sensor, 8: clutch, 9: transmission, 15: HCU, 16: TCM, 17: sensor, 100: vehicle braking control device, 101: coasting determination unit, 102: wheel lock determination unit, 103: control unit

Claims

1. A vehicle braking control device for controlling a vehicle equipped with a regenerative braking device that generates a regenerative braking force, a coasting determination means for determining whether the vehicle is coasting; a wheel lock determination means for determining whether or not a wheel is locked; a control means for suppressing a regenerative braking force generated by the regenerative braking device from the time when the coasting determination means determines that the vehicle is coasting and the wheel lock determination means determines that the wheels are locked, until the time when the coasting determination means determines that the vehicle is not coasting and the wheel lock determination means determines that the wheels are not locked, The vehicle braking control device is characterized in that the coasting determination means determines whether the vehicle is coasting based on the driver's intention to decelerate, and the driver's intention to decelerate is determined based on a deceleration operation by depressing the brake pedal.

2. 2. The vehicle brake control device according to claim 1, wherein the control means sets the regenerative braking force generated by the regenerative braking device to zero from the time when the coasting determination means determines that the vehicle is coasting and the wheel lock determination means determines that the wheels are locked, until the time when the coasting determination means determines that the vehicle is not coasting and the wheel lock determination means determines that the wheels are not locked.

3. A braking control device for a vehicle that controls a vehicle equipped with an engine that generates a braking force by resistance and a braking force transmission mechanism that transmits the braking force generated by the engine to wheels, comprising: a wheel lock determination means for determining whether or not a wheel is locked; a coasting determination means for determining whether the vehicle is coasting; a control means for suppressing the braking force transmitted by the braking force transmission mechanism from the time when the coasting determination means determines that the vehicle is coasting and the wheel lock determination means determines that the wheels are locked, until the time when the coasting determination means determines that the vehicle is not coasting and the wheel lock determination means determines that the wheels are not locked, The vehicle braking control device is characterized in that the coasting determination means determines whether the vehicle is coasting based on the driver's intention to decelerate, and the driver's intention to decelerate is determined based on a deceleration operation by depressing the brake pedal.

4. 4. The vehicle brake control device according to claim 3, wherein the control means prevents the braking force from being transmitted by the braking force transmission mechanism from being transmitted after the coasting determination means determines that the vehicle is coasting and the wheel lock determination means determines that the wheels are locked, until the coasting determination means determines that the vehicle is not coasting and the wheel lock determination means determines that the wheels are not locked.

5. 5. The vehicle braking control device according to claim 1, wherein the coasting determination means determines whether the vehicle is coasting or not based on the driver's intention to accelerate and the vehicle's stopped state.

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