Braking force control apparatus for a vehicle

Patent metadata

Field	Value
Publication number	US-10046643-B2
Application number	US-201514953582-A
Country	US
Kind code	B2
Filing date	Nov 30, 2015
Priority date	Dec 4, 2014
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

In order to enable satisfactory vehicle motion control to be carried out while wheels (10) are being braked, on a vehicle in which each of the wheels (10) is braked by a regenerative braking force by a motor (30) and a friction braking force by a friction brake mechanism (40), a brake ECU (53) acquires at least one parameter out of a steering angle, a steering velocity, a lateral acceleration of a vehicle body, a yaw rate of the vehicle body, a sprung vertical acceleration, and an unsprung vertical acceleration, and when a magnitude of the parameter is more than a threshold, decreases a ratio of the regenerative braking force out of a driver-requested braking force, and increases a ratio of the friction braking force.

First claim

What is claimed is:

1. A braking force control apparatus for a vehicle, comprising:
a motor configured to transmit a drive torque and a regenerative braking torque to a wheel to thereby generate a braking/driving force on the wheel;
a mechanical brake device configured to apply a mechanical resistance to the wheel to thereby generate a braking force on the wheel; and
an electronic control unit (ECU) configured to determine a total requested braking force, and distribute, based on the total requested braking force and in accordance with a distribution characteristic, a first distribution of a requested regenerative braking force to be generated by the motor, and a second distribution of a requested mechanical braking force to be generated by the mechanical brake device in order to decelerate the vehicle,
wherein the ECU is further configured to calculate a target braking/driving force for the wheel to be generated by the motor based on the first distribution of the requested regenerative braking force distributed by the ECU and a control braking/driving force required for vehicle motion control, and control an operation of the motor based on the target braking/driving force,
wherein the ECU is further configured to control an operation of the mechanical brake device based on the requested mechanical braking force,
wherein the ECU is further configured to determine whether a specific state, in which a control braking/driving force that is generatable by the motor is insufficient for the control braking/driving force required for the vehicle motion control, has occurred,
wherein, when the specific state is determined to have occurred under a state in which the total requested braking force is generated, the ECU is further configured to change the distribution characteristic such that the first distribution of the requested regenerative braking force decreases and the second distribution of the requested mechanical braking force determined by the distribution characteristic increases as compared with a state in which the specific state is not determined to have occurred,
wherein the ECU is further configured to acquire a margin degree based on a margin of the regenerative braking torque that is additionally generatable by the motor,
wherein the ECU is further configured to acquire an index for predicting the occurrence of the specific state, and determine, based on the index, whether or not the specific state has occurred,
wherein the ECU is further configured to acquire, as the index, a vehicle state parameter representing a motion state of the vehicle or affecting the motion state, and
wherein, when the margin degree is less than a margin degree threshold, the ECU is further configured to change the distribution characteristic of the total requested braking force such that the first distribution of the requested regenerative braking force decreases and the second distribution of the requested mechanical braking force increases.

2. The braking force control apparatus for a vehicle according to claim 1 ,
wherein the ECU is further configured to acquire, as the vehicle state parameter, at least one of a steering angle, a steering velocity, a lateral acceleration of a vehicle body, a yaw rate of the vehicle body, a sprung vertical acceleration, or an unsprung vertical acceleration, and determine that the specific state has occurred when a magnitude of the acquired vehicle state parameter is greater than a determination threshold.

3. The braking force control apparatus for a vehicle according to claim 2 ,
wherein the vehicle motion control includes at least one of sprung vibration suppression control of suppressing a vibration in a vertical direction of the vehicle body, roll motion control of suppressing a motion in a roll direction of the vehicle body, yaw motion control of controlling a motion in a yaw direction of the vehicle body, or pitch motion control of controlling a motion in a pitch direction of the vehicle body.

4. The braking force control apparatus for a vehicle according to claim 2 ,
wherein the ECU is further configured to acquire at least the steering angle as the vehicle state parameter, and determine that the specific state has occurred when the steering angle is greater than a first threshold that corresponds to the determination threshold; and
wherein, when the steering angle is equal to or less than a second threshold set to be a value less than the first threshold, the ECU is further configured to wait, after the specific state is determined to have occurred, for at least a set delay period and until a state in which the steering angle is less than the first threshold continues after the steering angle becomes equal to or less than the second threshold, and start an increase in the first distribution of the requested regenerative braking force and a decrease in the second distribution of the requested mechanical braking force such that the distribution characteristic is equal to the distribution characteristic before a change in the distribution characteristic.

5. The braking force control apparatus for a vehicle according to claim 1 ,
wherein the ECU is further configured to acquire, as the index, a magnitude of the control braking/driving force required for the vehicle motion control, and determine that the specific state has occurred when the magnitude of the control braking/driving force is greater than a determination threshold.

6. The braking force control apparatus for a vehicle according to claim 2 ,
wherein the ECU is further configured to change the distribution characteristic such that, as the index increases, the first distribution of the requested regenerative braking force decreases, and the second distribution of the requested mechanical braking force increases.

7. The braking force control apparatus for a vehicle according to claim 1 ,
wherein the ECU is further configured to detect a lock state representing a state in which the wheel is estimated to be locked; and
wherein the ECU is further configured to start, under a state in which the distribution characteristic is changed by the ECU and when the lock state is detected by the ECU, an increase in the first distribution of the requested regenerative braking force, and a decrease in the second distribution of the requested mechanical braking force.

8. The braking force control apparatus for a vehicle according to claim 1 ,
wherein the motor is provided so as to transmit the driving torque and the regenerative braking torque independently to each of a front left wheel, a front right wheel, a rear left wheel, and a rear right wheel.

Assignees

• Toyota Motor Co Ltd

Inventors

• Nakatsu Masatoshi

Classifications

• B60L7/26 Primary

  Controlling the braking effect · CPC title

• B60T1/10

  by utilising wheel movement for accumulating energy, e.g. driving air compressors · CPC title

• B60L2240/24

  Steering angle · CPC title

• B60T2270/604

  Merging friction therewith; Adjusting their repartition · CPC title

• B60L15/2009

  for braking · CPC title