Brake apparatus

1. A brake apparatus configured to execute a brake assist based on a collision risk representing a risk of a vehicle including the brake apparatus to collide with an obstacle, and an emergency operation level representing an emergency level of a brake operation by a driver, comprising:

a collision risk calculation unit configured to calculate the collision risk;

a detection unit configured to detect the emergency operation level;

a storage unit configured to store the emergency operation level detected by the detection unit when the collision risk is within a predetermined range;

a threshold determination unit configured to determine a threshold for the emergency operation level based on the collision risk; and

a brake assist unit configured to execute the brake assist based on a comparison between (1) the emergency operation level stored by the storage unit at a moment the collision risk was a first value and (2) the threshold for the emergency operation level determined by the threshold determination unit at a moment the collision risk is a second value, wherein

the collision risk becomes the second value after having been the first value, and

the second value is greater than the first value.

2. The brake apparatus as claimed in claim 1 , wherein the storage unit stores the emergency operation level detected by the detection unit at a predetermined moment after the collision risk has reached a value greater than or equal to a predetermined value.

3. The brake apparatus as claimed in claim 1 , wherein the threshold determination unit decreases the threshold for the emergency operation level as the collision risk increases.

4. The brake apparatus as claimed in claim 1 ,

wherein the detection unit detects a brake operation amount by the driver,

wherein the threshold determination unit determines a threshold for the brake operation amount based on the collision risk, and

wherein the brake assist unit executes the brake assist when the emergency operation level stored by the storage unit is greater than or equal to the threshold for the emergency operation level and the brake operation amount is greater than or equal to the threshold for the brake operation amount.

5. The brake apparatus as claimed in claim 4 , further comprising:

a brake assist amount determination unit configured to determine a brake assist amount based on the collision risk,

wherein the threshold determination unit determines the threshold for the emergency operation level and the threshold for the brake operation amount based on the collision risk and the brake assist amount.

6. The brake apparatus as claimed in claim 1 , wherein the storage unit updates the stored emergency operation level with the emergency operation level detected by the detection unit when the emergency operation level detected by the detection unit is higher than the stored emergency operation level.

7. The brake apparatus as claimed in claim 1 , wherein the emergency operation level is an operation speed of the brake operation by the driver.

8. A brake apparatus configured to execute a brake assist based on a collision risk representing a risk of a vehicle including the brake apparatus to collide with an obstacle, and an emergency operation level representing an emergency level of a brake operation by a driver, comprising:

a sensor configured to detect the emergency operation level; and

circuitry configured to:

calculate the collision risk;

store the detected emergency operation level when the collision risk is within a predetermined range;

determine a threshold for the emergency operation level based on the collision risk; and

execute the brake assist based on a comparison between (1) the emergency operation level stored at a moment the collision risk was a first value and (2) the threshold for the emergency operation level determined at a moment the collision risk is a second value, wherein

the collision risk becomes the second value after having been the first value, and

the second value is greater than the first value.

9. The brake apparatus as claimed in claim 8 , wherein the circuitry is configured to store the detected emergency operation level at a predetermined moment after the collision risk has reached a value greater than or equal to a predetermined value.

10. The brake apparatus as claimed in claim 8 , wherein the threshold for the emergency operation level decreases as the collision risk increases.

11. The brake apparatus as claimed in claim 8 , wherein

the sensor is configured to detect a brake operation amount by the driver, and

the circuitry is configured to:

determine a threshold for the brake operation amount based on the collision risk; and

execute the brake assist when the stored emergency operation level is greater than or equal to the threshold for the emergency operation level and the brake operation amount is greater than or equal to the threshold for the brake operation amount.

12. The brake apparatus as claimed in claim 11 , wherein the circuitry is configured to:

determine a brake assist amount based on the collision risk,

determine the threshold for the emergency operation level and the threshold for the brake operation amount based on the collision risk and the brake assist amount.

13. The brake apparatus as claimed in claim 8 , wherein the circuitry is configured to update the stored emergency operation level with the detected emergency operation level when the detected emergency operation level is higher than the stored emergency operation level.

14. The brake apparatus as claimed in claim 8 , wherein the emergency operation level is an operation speed of the brake operation by the driver.