Brake control system in vehicle

1. A brake control system in a vehicle which executes anti-lock brake control for controlling a braking force applied to a wheel to prevent the wheel from being locked during braking of the vehicle, the system including one or more control units comprising:

an initiation determiner section configured to:

receive a signal from one or more wheel speed sensors;

determine whether or not an initiation condition used to initiate the anti-lock brake control is met, the initiation condition including a condition in which a decrease rate of a wheel speed which is a rotational speed of the wheel is not less than a predetermined threshold; and

generate output indicating whether the initiation condition is met;

a brake control section configured to:

receive the output from the initiation determiner section indicating whether the initiation condition is met; and

initiate control of the braking force applied to the wheel in the anti-lock brake control, if the initiation determiner section determines that the initiation condition is met; and

a driving state detector section configured to:

receive a signal from one or more brake sensors;

detect a brake amount command value of a driver's brake operation during braking; and

generate output indicating the brake amount command value,

wherein the initiation determiner section changes the threshold used to determine whether or not to initiate the anti-lock brake control, such that the threshold is smaller as the detected brake amount command value is smaller, and

wherein the detected brake amount command value includes one or more of a hydraulic brake pressure, a displacement amount of a brake lever, a displacement amount of a brake pedal, or a displacement amount of a brake pad.

2. The brake control system in the vehicle according to claim 1 ,

wherein the vehicle includes an accelerator operation member operated by a driver; and

wherein the initiation determiner section does not determine whether or not the initiation condition is met, during a predetermined time period which passes after the accelerator operation member has been operated quickly to decelerate the vehicle.

3. The brake control system in the vehicle according to claim 2 ,

wherein the vehicle includes a clutch between a drive wheel and a driving power source; and

wherein the initiation determiner section determines whether or not the initiation condition is met within the predetermined time period which passes after the accelerator operation member has been operated quickly to decelerate the vehicle, if the clutch is disengaged.

4. The brake control system in the vehicle according to claim 1 , comprising:

a braking characteristic memory for storing as a braking characteristic of the wheel, a relation between the brake amount command value and the decrease rate of the wheel speed in a range in which the vehicle is not locked such that the decrease rate increases with an increase in the brake amount command value;

wherein the initiation determiner section changes the threshold used to determine whether or not to initiate the anti-lock brake control based on the braking characteristic such that the threshold is smaller as the value of the brake amount command value detected by the driving state detector section is smaller.

5. The brake control system in the vehicle according to claim 4 ,

wherein the braking characteristic memory contains a standard value of a rate of a decrease in a wheel speed of the wheel which is caused by the brake amount command value; and

wherein the initiation determiner section identifies a standard value of the decrease rate of the wheel speed based on the value of the brake amount command value detected by the driving state detector section, with reference to the braking characteristic; and

wherein the initiation determiner section changes the threshold used to determine whether or not to initiate the anti-lock brake control such that the threshold is smaller as a difference between the standard value and the decrease rate is greater if the decrease rate is greater than the standard value.

6. The brake control system in the vehicle according to claim 1 ,

wherein the initiation determiner section changes the threshold used to determine whether or not to initiate the anti-lock brake control such that the threshold is smaller as a change rate of the brake amount command value detected by the driving state detector section is greater.

7. The brake control system in the vehicle according to claim 1 ,

wherein the initiation condition includes a first condition based on the decrease rate of the wheel speed and a second condition based on a parameter other than the decrease rate of the wheel speed; and

wherein the initiation determiner section determines that the initiation condition is met, if both of the first and second conditions are met.

8. The brake control system in the vehicle according to claim 1 ,

wherein the initiation condition includes a first condition based on the decrease rate of the wheel speed and a second condition based on a parameter other than the decrease rate of the wheel speed; and

wherein the initiation determiner section determines that the initiation condition is met, if one of the first and second conditions is met.

9. The brake control system in the vehicle according to claim 1 ,

wherein the initiation determiner section and the brake control section may be included in separate ECUs, respectively.

10. The brake control system in the vehicle according to claim 1 ,

wherein the vehicle includes a setting operation member operated by a driver to set the initiation condition of the anti-lock brake control; and

wherein the initiation determiner section changes the threshold used to determine whether or not to initiate the anti-lock brake control, according to the driver's operation of the setting operation member.

11. The brake control system in the vehicle according to claim 1 ,

wherein the threshold is set larger than a braking characteristic line indicating a relation between the brake amount command value of the braking force applied to the wheel, and the decrease rate of the wheel speed in a range in which the vehicle is not locked such that the decrease rate increases with an increase in the brake amount command value.

12. The brake control system in the vehicle according to claim 1 ,

wherein the initiation determiner section determines whether or not the initiation condition of the anti-lock brake control is met, based on the decrease rate of the wheel speed of a front wheel.

13. The brake control system in the vehicle according to claim 12 ,

wherein the initiation determiner section determines whether or not the initiation condition of the anti-lock brake control is met, based on the decrease rate of the wheel speed of the front wheel, and a caliper pressure of a front wheel brake.

14. The brake control system in the vehicle according to claim 1 ,

wherein the initiation determiner section determines whether or not the initiation condition of the anti-lock brake control is met, based on the decrease rate of the wheel speed of a rear wheel.

15. The brake control system in the vehicle according to claim 14 ,

wherein the initiation determiner section determines whether or not the initiation condition of the anti-lock brake control is met, based on the decrease rate of the wheel speed of the rear wheel, and a caliper pressure of a rear wheel brake.

16. A brake control system in a vehicle which executes anti-lock brake control for controlling a braking force applied to a wheel to prevent the wheel from being locked during braking of the vehicle, the system including one or more control units comprising: an initiation determiner section configured to:

receive a signal from one or more wheel speed sensors;

determine whether or not an initiation condition used to initiate the anti-lock brake control is met, the initiation condition including a condition in which a decrease rate of a wheel speed which is a rotational speed of the wheel is not less than a predetermined threshold; and

generate output indicating whether the initiation condition is met;

a brake control section configured to:

receive the output from the initiation determiner section indicating whether the initiation condition is met; and

initiate control of the braking force applied to the wheel in the anti-lock brake control, if the initiation determiner section determines that the initiation condition is met; and

a driving state detector section configured to:

receive a signal from one or more brake sensors;

detect a brake amount command value of a driver's brake operation during braking; and

generate output indicating the brake amount command value, wherein the initiation determiner section changes the threshold used to determine whether or not to initiate the anti-lock brake control, such that the threshold is smaller as the detected brake amount command value is smaller, and

wherein the detected brake amount command value includes a caliper pressure of a front wheel brake or a rear wheel brake.