Brake control apparatus

1. A brake control apparatus which performs a brake assist control for assisting a brake operation by a driver of a vehicle when an obstacle exists anterior to the vehicle, the brake control apparatus comprising:

a controller configured to:

calculate a contact possibility of the vehicle contacting the obstacle;

change, on the basis of the contact possibility, a decreasing rate of a deceleration of the vehicle caused by the brake assist control, when the deceleration of the vehicle decreases as time passes regardless of the brake operation by the driver; and

change the decreasing rate of the deceleration such that the higher the contact possibility is, the smaller the decreasing rate of the deceleration is.

2. The brake control apparatus according to claim 1 , wherein the controller changes, on the basis of the contact possibility, the decreasing rate of the deceleration when the brake assist control is performed such that the deceleration decreases as time passes.

3. The brake control apparatus according to claim 1 , wherein

the controller changes, on the basis of the contact possibility, an increasing rate of the deceleration when the brake assist control is performed such that the deceleration increases as time passes, and

the controller (i) changes the increasing rate of the deceleration such that the higher the contact possibility is, the larger the increasing rate of the deceleration is, if the contact possibility is equal to or more than a predetermined threshold value, and (ii) fixes the increasing rate of the deceleration, if the contact possibility is not equal to or more than the predetermined threshold value.

4. The brake control apparatus according to claim 1 , wherein

the controller changes at least one of a decreasing rate of a first deceleration and the increasing rate of a second deceleration such that the higher the contact possibility is, the larger an absolute value of a difference between the decreasing rate of the first deceleration and the increasing rate of the second deceleration is,

the first deceleration is the deceleration when the brake assist control is performed such that the deceleration decreases as time passes, and

the second deceleration is the deceleration when the brake assist control is performed such that the deceleration increases as time passes.

5. The brake control apparatus according to claim 1 , wherein the controller calculates, as the contact possibility, a collision prediction time until the vehicle collides with the obstacle.

6. The brake control apparatus according to claim 5 , wherein the controller changes, on the basis of the collision prediction time, the decreasing rate of the deceleration when the brake assist control is performed such that the deceleration decreases as time passes.

7. The brake control apparatus according to claim 5 , wherein the controller changes the decreasing rate of the deceleration such that the shorter the collision prediction time is, the smaller the decreasing rate of the deceleration is.

8. The brake control apparatus according to claim 5 , wherein

the controller changes, on the basis of the collision prediction time, an increasing rate of the deceleration when the brake assist control is performed such that the deceleration increases as time passes, and

the controller (i) changes the increasing rate of the deceleration such that the shorter the collision prediction time is, the larger the increasing rate of the deceleration is, if the collision prediction time is equal to or less than a predetermined threshold value, and (ii) fixes the increasing rate of the deceleration, if the collision prediction time is not equal to or less than the predetermined threshold value.

9. The brake control apparatus according to claim 5 , wherein

the controller changes at least one of a decreasing rate of a first deceleration and an increasing rate of a second deceleration such that the shorter the collision prediction time is, the larger an absolute value of a difference between the decreasing rate of the first deceleration and the increasing rate of the second deceleration is,

the first deceleration is the deceleration when the brake assist control is performed such that the deceleration decreases as time passes, and

the second deceleration is the deceleration when the brake assist control is performed such that the deceleration increases as time passes.

10. A brake control apparatus which performs a brake assist control for assisting a brake operation by a driver of a vehicle when an obstacle exists anterior to the vehicle, the brake control apparatus comprising:

a controller being configured to:

calculate a contact possibility of the vehicle contacting the obstacle; and

change at least one of a decreasing rate of a first deceleration and an increasing rate of a second deceleration such that the higher the contact possibility is, the larger an absolute value of a difference between the decreasing rate of the first deceleration and the increasing rate of the second deceleration, when the deceleration of the vehicle changes as time passes regardless of the brake operation by the driver, wherein

the first deceleration is a deceleration of the vehicle when the brake assist control is performed such that the deceleration decreases as time passes, the second deceleration is a deceleration when the brake assist control is performed such that the deceleration increases as time passes.

11. The brake control apparatus according to claim 10 , wherein the controller changes the decreasing rate of the first deceleration such that the higher the contact possibility is, the smaller the decreasing rate of the first deceleration is.

12. The brake control apparatus according to claim 10 , wherein the controller changes the increasing rate of the second deceleration such that the higher the contact possibility is, the larger the increasing rate of the second deceleration is.

13. The brake control apparatus according to claim 10 , wherein the controller calculates, as the contact possibility, a reach time until the vehicle reaches the obstacle.

14. The brake control apparatus according to claim 13 , wherein the controller changes the decreasing rate of the first deceleration such that the shorter the reach time is, the smaller the decreasing rate of the first deceleration is.

15. The brake control apparatus according to claim 13 , wherein the controller changes the increasing rate of the second deceleration such that the shorter the reach time is, the larger the increasing rate of the second deceleration is.