Brake apparatus

1. A brake apparatus comprising:

a master cylinder configured to be activated according to a brake operation performed by a driver;

a reservoir tank divided into at least a first chamber connected to a wheel cylinder via the master cylinder and a second chamber connected to a hydraulic source configured to increase a pressure of brake fluid and transmit the brake fluid to the wheel cylinder;

a brake control unit configured to perform brake control of transmitting the brake fluid to the wheel cylinder; and

a fluid level detection unit configured to detect a fluid level of the brake fluid in the reservoir tank, wherein

the brake control unit is provided so as to be able to perform first brake control of transmitting the brake fluid from the first chamber to the wheel cylinder with use of the master cylinder, thereby increasing a pressure in the wheel cylinder, and second brake control of transmitting the brake fluid in the second chamber to the wheel cylinder with use of the hydraulic source, thereby increasing a pressure in the wheel cylinder,

the brake control unit switches brake control between the first brake control and the second brake control according to the fluid level detected by the fluid level detection unit,

the brake control unit performs the second brake control if the fluid level detected by the fluid level detection unit is detected to fall below a first fluid level,

the brake control unit performs the first brake control if the fluid level in the second chamber that is detected by the fluid level detection unit is detected to fall below a second fluid level which is lower than the first fluid level

the brake control unit performs the first brake control if the brake operation is detected to be performed by the driver, and

while the brake operation is detected to be performed by the driver, the brake control unit stops the first brake control if the fluid level detected by the fluid level detection unit is detected to fall below the first fluid level.

2. The brake apparatus according to claim 1 , wherein the hydraulic source is a pump.

3. The brake apparatus according to claim 1 , wherein the hydraulic source introduces the brake fluid therein via a fluid pool having a predetermined volume, the fluid pool being provided between the reservoir tank and the hydraulic source.

4. The brake apparatus according to claim 1 , wherein the first chamber is connected to a primary system oil passage, which supplies the pressure to a predetermined wheel cylinder, and a secondary system oil passage, which supplies the pressure to another wheel cylinder, via the master cylinder, and

wherein the brake control unit includes a fluid leak estimation unit configured to estimate in which system the fluid leaks, the primary system oil passage or the secondary system oil passage, if the fluid level detected by the fluid level detection unit is detected to fall below the first fluid level.

5. The brake apparatus according to claim 4 , wherein the first chamber is further divided into two chambers, and the individual chambers are connected to the primary system oil passage and the secondary system oil passage via the master cylinder, respectively, and

wherein the brake control unit stops the second brake control using the system oil passage where the fluid leak estimation unit estimates that the fluid leaks, and continues the second brake control using the other system oil passage.

6. The brake apparatus according to claim 1 , wherein an inside of the reservoir tank is divided into the first chamber and the second chamber by a partition wall provided so as to protrude by a predetermined length upwardly from an inner wall of the reservoir tank that would become a lower surface when the reservoir tank is mounted on a vehicle,

wherein the first fluid level is set to a position equal to or higher than the predetermined length upwardly from the inner wall, and

wherein the second fluid level is set to a position in the second chamber.

7. The brake apparatus according to claim 6 , wherein the first chamber is further divided into two chambers, and the individual chambers are connected to a primary system oil passage, which supplies the pressure to a predetermined wheel cylinder, and a secondary system oil passage, which supplies the pressure to another wheel cylinder, via the master cylinder, respectively.

8. The brake apparatus according to claim 1 , wherein the fluid level detection unit detects the fluid level in the second chamber.

9. A brake apparatus comprising:

a master cylinder configured to increase a pressure in a wheel cylinder by being activated according to a brake operation performed by a driver;

a reservoir tank divided into at least a first chamber connected to the wheel cylinder via the master cylinder and a second chamber connected to a hydraulic source configured to increase a pressure of brake fluid and transmit the brake fluid to the wheel cylinder; and

a fluid level detection unit configured to detect whether an amount of the brake fluid in the reservoir tank falls below a plurality of fluid levels preset in the reservoir tank, wherein

if the amount of the brake fluid in the reservoir tank is detected to fall below the fluid level by the fluid level detection unit, the brake apparatus changes a method for increasing the pressure in the wheel cylinder between a method of increasing the pressure by the hydraulic source with use of the brake fluid in the second chamber and between a method of increasing the pressure by the master cylinder according to the brake operation performed by the driver with use of the brake fluid in the first chamber, according to the fluid level that the amount of the brake fluid in the reservoir tank falls below,

upon detecting that the brake operation is performed by the driver, the brake apparatus increases the pressure in the wheel cylinder with use of the brake fluid in the first chamber by a hydraulic pressure in the master cylinder that is generated according to an amount of the brake operation, and

the brake apparatus stops increasing the pressure in the wheel cylinder with use of the brake fluid in the first chamber, if the amount of the brake fluid in the reservoir tank is detected to match or fall below the first fluid level by the fluid level detection unit while the driver is performing the brake operation.

10. The brake apparatus according to claim 9 , wherein the brake apparatus increases the pressure in the wheel cylinder by the hydraulic source with use of the brake fluid in the second chamber, if the amount of the brake fluid in the reservoir tank is detected to match or fall below a preset first fluid level by the fluid level detection unit, and

wherein the brake apparatus stops increasing the pressure in the wheel cylinder by the hydraulic source with use of the brake fluid in the second chamber, and increases the pressure in the wheel cylinder by the master cylinder with use of the brake fluid in the first chamber according to the brake operation performed by the driver, if the amount of the brake fluid in the second chamber is detected to match or fall below a second fluid level, which is lower than the first fluid level, by the fluid level detection unit.

11. The brake apparatus according to claim 9 , wherein the hydraulic source is a pump, and the brake apparatus is configured to increase the pressure in the wheel cylinder by the pump with use of the brake fluid in the second chamber.

12. The brake apparatus according to claim 11 , wherein the first chamber is connected to a primary system oil passage, which supplies the pressure to a predetermined wheel cylinder, and a secondary system oil passage, which supplies the pressure to another wheel cylinder, via the master cylinder, and

wherein the brake apparatus includes a fluid leak estimation unit configured to estimate in which system the fluid leaks, the primary system oil passage or the secondary system oil passage, if the amount of the brake fluid in the reservoir tank is detected to match or fall below the preset first fluid level by the fluid level detection unit.

13. The brake apparatus according to claim 12 , wherein the first chamber is further divided into two chambers, and the individual chambers are connected to the primary system oil passage and the secondary system oil passage via the master cylinder, respectively, and

wherein the brake apparatus stops increasing the pressure in the wheel cylinder by the hydraulic source with use of the brake fluid in the second chamber with respect to the system oil passage where the fluid leak estimation unit estimates that the fluid leaks, and continues increasing the pressure in the wheel cylinder by the hydraulic source with use of the brake fluid in the second chamber with respect to the other system oil passage.