대표
청구항
▼
What is claimed is: 1. An electronic brake system including: a brake pedal operable according to a requisite braking force; a failsafe cylinder for generating a brake fluid pressure in conjunction with operation of the brake pedal; wheel cylinders equipped at respective vehicle wheels, for generating respective braking forces at the respective vehicle wheels; a master cylinder for generating brake fluid pressure and applying the brake fluid pressure to the wheel cylinders to generate the respective wheel pressures; and a motor for controlling the brak...
What is claimed is: 1. An electronic brake system including: a brake pedal operable according to a requisite braking force; a failsafe cylinder for generating a brake fluid pressure in conjunction with operation of the brake pedal; wheel cylinders equipped at respective vehicle wheels, for generating respective braking forces at the respective vehicle wheels; a master cylinder for generating brake fluid pressure and applying the brake fluid pressure to the wheel cylinders to generate the respective wheel pressures; and a motor for controlling the brake fluid pressure in the master cylinder; wherein the electronic brake system is operative in a first operational mode and a second operational mode is operative, in the first operational mode, brake fluid pressures in the wheel cylinders are generated based on the brake fluid pressure in the master cylinder with driving of the motor, and in the second operational mode, the brake fluid pressures in the wheel cylinders are generated based on the brake fluid pressure generated in the failsafe cylinder without driving the motor; and, in the second operational mode, the brake fluid pressure in the master cylinder is controlled by the brake fluid pressure generated in the failsafe cylinder, and the controlled brake fluid pressure in the master cylinder is provided to the wheel cylinders to control the respective brake fluid pressures in the wheel cylinders. 2. The electronic brake system according to claim 1, further comprising: a pedal operation amount detection portion for detecting an operation amount of the brake pedal; wherein, in the first operational mode, the motor is driven based on the pedal operation amount detected by the pedal operation amount detection portion and then controls the brake fluid pressure in the master cylinder and the wheel cylinders. 3. The electronic brake system according to claim 1, wherein the failsafe cylinder includes a piston for being driven by the operation of the brake pedal and a cylinder portion for accommodating the piston, and the failsafe cylinder generates the brake fluid pressure based on a movement of the piston, the master cylinder includes first and second master pistons, a cylinder portion for accommodating the first and second master pistons, first and second chambers formed by the first and second master pistons and the cylinder portion, a failsafe piston, and failsafe pressurizing chamber formed by the failsafe piston and the cylinder portion thereof and connected to the cylinder portion of the failsafe cylinder, wherein brake fluid pressures in the first and second chambers are controlled by movements of the first and second master pistons and are provided to the wheel cylinders, and the first and second master pistons are moved in conjunction with movement of the failsafe piston, in the first operational mode, brake fluid pressures in the first and second chambers of the master cylinder are controlled based on the movement of the first and second master pistons by driving of the motor, in the second operational mode, the brake fluid pressures in the first and second chambers of the master cylinder are controlled based on the movement of the failsafe piston by a brake fluid pressure in the failsafe pressurizing chamber that is increased based on the brake fluid pressure in the failsafe cylinder. 4. The electronic brake system according to claim 3, further comprising: a valve located between the failsafe cylinder and the master cylinder; wherein the piston of the failsafe cylinder includes first and second pistons, and the cylinder portion of the fail safe cylinder includes a first chamber formed between the first and second pistons and a second chamber formed between the second piston and a bottom portion of the cylinder portion, wherein the first and second chambers of the failsafe cylinder are connected to the failsafe pressurizing chamber of the master cylinder via a conduit opened and closed by the valve, the valve is controlled to close the conduit in the first operational mode and controlled to open the conduit in the second operational mode. 5. The electronic brake system according to claim 3, wherein the master cylinder includes a piston rod formed with the first master piston and for being driven by the motor, wherein the piston rod is inserted in a hole formed in the failsafe piston, has a flange portion located on a side of the failsafe piston to the first master piston, and moves with the flange portion independent of the failsafe piston. 6. The electronic brake system according to claim 1, further comprising: a gear unit for converting rotational power generated by the motor to linear motion, wherein a piston rod equipped in the master cylinder is driven by the motor through the gear unit. 7. The electronic brake system according to claim 1, wherein the brake fluid pressure to be generated by the master cylinder is defined based on a pedal pressure or a pedal stroke as the pedal operation amount, and the motor is driven to generate the brake fluid pressure defined based on the pedal pressure or the pedal stroke. 8. The electronic brake system according to claim 1, wherein the brake fluid pressure to be generated by the master cylinder is defined based on a pressure value equal to a pressure calculated based on a pedal pressure or a pedal stroke as the pedal operation amount minus a pressure calculated based on a regenerative braking force, and the motor is driven to generate the brake fluid pressure defined based on the pressure value. 9. The electronic brake system according to claim 1, wherein the brake fluid pressure to be generated by the master cylinder is defined based on a distance between the vehicle and a vehicle in front of the vehicle, and the motor is driven to generate the defined brake fluid pressure. 10. The electronic brake system according to claim 1, further comprising: a vehicle condition detection portion for detecting a vehicle condition; wherein the brake fluid pressure generated by the master cylinder is defined based on the vehicle condition detected by the vehicle condition detection portion and the pedal operation amount detected by the pedal operation amount detection portion, and the motor is driven to generate the defined brake fluid pressure. 11. The electronic brake system according to claim 10, wherein wheel slippage caused by vehicle acceleration is determined based on the vehicle condition detected by the vehicle condition detection portion, and the brake fluid pressure generated by the master cylinder is defined based on the wheel slippage. 12. The electronic brake system according to claim 10, wherein vehicle wheel side skidding is determined based on the vehicle condition detected by the vehicle condition detection portion, and the brake fluid pressure generated by the master cylinder is defined based on the vehicle wheel side skidding. 13. An electronic brake system comprising: a brake pedal operable according to a requisite braking force; a failsafe cylinder for generating a brake fluid pressure in conjunction with operation of the brake pedal; wheel cylinders equipped at respective vehicle wheels, for generating respective braking forces at the respective vehicle wheels; a master cylinder for generating brake fluid pressure and applying the brake fluid pressure to the wheel cylinders to generate the respective wheel pressures; and a motor for controlling the brake fluid pressure in the master cylinder; wherein the electronic brake system is operative in a first operational made and a second operational mode is operative, in the first operational mode, brake fluid pressure in the wheel cylinders are generated based on the brake fluid pressure in the master cylinder with driving of the motor, and in the second operational mode, the brake fluid pressures in the wheel cylinders are generated based on the brake fluid pressure generated in the failsafe cylinder without driving the motor, a gear unit for converting rotational power generated by the motor to linear motion, wherein a piston rod equipped in the master cylinder is driven by the motor through the gear unit, wherein the piston rod includes a first portion connected to a first master piston and a second portion jointed to the gear unit, the first portion and the second portion are separable from each other. 14. An electronic brake system comprising: a brake pedal operable according to a requisite braking force; a failsafe cylinder for generating a brake fluid pressure in conjunction with operation of the brake pedal; wheel cylinders equipped at respective vehicle wheels, for generating respective braking faces at the respective vehicle wheels; a master cylinder far generating brake fluid pressure and applying the brake fluid pressure to the wheel cylinders to generate the respective wheel pressures; and a motor for controlling the brake fluid pressure in the master cylinder; wherein the electronic brake system acts in a first operational mode and a second operational mode, in the first operational mode, brake fluid pressure in the wheel cylinders are generated based on the brake fluid pressure in the master cylinder by driving of the motor, and in the second operational mode, the brake fluid pressure generated in the failsafe cylinder is provided to the brake fluid pressures in the wheel cylinders without driving of the motor, a change valve for selecting the master cylinder the failsafe cylinder as a brake fluid pressure provision resource to the wheel cylinders; wherein the failsafe cylinder includes a piston for being driven by the operation of the brake pedal and a cylinder portion for accommodating piston, the failsafe cylinder generates the brake fluid pressure based on a movement of the piston, the master cylinder includes first and second master pistons, a cylinder portion for accommodating the first and second master pistons, and first and second chambers formed by the first and second master pistons and the cylinder portion, in the first operational mode, the brake fluid pressure in the first and second chambers of the master cylinder are controlled based on the movement of the first and second master pistons by driving of the motor, and the change valve selects the master cylinder as the brake fluid pressure provision resource to the wheel cylinders, and in the second operational mode, the change valve selects the failsafe cylinder as a brake fluid pressure provision resource to the wheel cylinders. 15. The electronic brake system according to claim 14, wherein the change valve comprises: a change valve cylinder having a piston that is moved based on the brake fluid pressure in the failsafe cylinder to generate brake fluid pressure in the wheel cylinders; and a two-position valve for controlling brake fluid flow between the master cylinder and the wheel cylinder based on a movement of the piston of the change valve. 16. The electronic brake system according to claim 14, further comprising: a failsafe valve located between the failsafe cylinder and the change valve for opening or closing communication between the failsafe cylinder and the change valve, wherein failsafe valve opens between the failsafe cylinder and the change valve in the first operational mode, and opens between the failsafe cylinder and the change valve in the second operational mode. 17. The electronic brake system according to claim 15, wherein a two-position valve is located between the master cylinder and the change valve cylinder to allow brake fluid flow between the master cylinder and the wheel cylinder in the first operational mode, and to inhibit the brake fluid flow between the master cylinder and the wheel cylinder in the second operational mode. 18. The electronic brake system according to claim 16, further comprising: a stroke simulator located between the failsafe valve and the failsafe cylinder and having a piston for being moved by the brake fluid pressure generated in the failsafe cylinder and a spring for pushing the piston; and a cut valve for controlling open and close between the failsafe valve and the stroke simulator; wherein the cut valve opens between the failsafe cylinder and the stroke simulator in the first operational mode, and closes between the failsafe cylinder and the stroke simulator in the second operational mode, and the stroke simulator provides a reactive force to the brake pedal at the first operational mode. 19. The electronic brake system according to claim 14, wherein the brake fluid pressure to be generated by the master cylinder is defined based on a pedal pressure or a pedal stroke as the pedal operation amount, and the motor is driven to generate the brake fluid pressure defined based on the pedal pressure or the pedal stroke. 20. The electronic brake system according to claim 14, wherein the brake fluid pressure to be generated by the master cylinder is defined based on pressure value equal to a pressure calculated based on a pedal pressure or a pedal stroke as the pedal operation amount minus a pressure calculated based on a regenerative braking force, and the motor is driven to generate the brake fluid pressure defined based on the pressure value. 21. The electronic brake system according to claim 14, wherein the brake fluid pressure to be generated by the master cylinder is defined based on a distance between the vehicle and a vehicle in front of the vehicle, and the motor is driven to generate the defined brake fluid pressure. 22. The electronic brake system according to claim 14, further comprising: a vehicle condition detection portion for detecting a vehicle condition; wherein the brake fluid pressure generated by the master cylinder is defined based on the vehicle condition detected by the vehicle condition detection portion and the pedal operation amount detected by the pedal operation amount detection portion, and the motor is driven to generate the defined brake fluid pressure. 23. The electronic brake system according to claim 22, wherein wheel slippage caused by vehicle acceleration is determined based on the vehicle condition detected by the vehicle condition detection portion, and the brake fluid pressure generated by the master cylinder is defined based on the wheel slippage. 24. The electronic brake system according to claim 22, wherein vehicle wheel side skidding is determined based on the vehicle condition detected by the vehicle condition detection portion, and the brake fluid pressure generated by the master cylinder is defined based on the vehicle wheel side skidding.
