Hydraulic brake system for an off-road vehicle

• US 5,368,372 A
• Filed: 03/10/1993
• Issued: 11/29/1994
• Est. Priority Date: 10/30/1992
• Status: Expired due to Fees

• Current Assignee: Total Quality Enterprises, Inc.
• Original Assignee: Total Quality Enterprises, Inc.
• Inventors: Cords, Frederick W., Frye, David
• Primary Examiner(s): Oberleitner, Robert J.
• Assistant Examiner(s): Muratori, Alfred
• Application Number:
  US08/029,142
• Time in Patent Office: 629 Days
• Field of Search: 188/109, 137/115, 137/901, 303/10, 303/11, 303/20, 303/122.8, 180/272, 180/273
• US Class Current: 303/11
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60T 13/08 Overrun brakes
• CPC Class Codes: B60T 13/167 In combination with distributor valve
• CPC Class Codes: B60T 13/18 with control of pump output delivery , e.g. by distributor valves B60T13/167 takes precedence
• CPC Class Codes: B60T 13/745 acting on a hydraulic system, e.g. a master cylinder
• CPC Class Codes: B60T 7/12 for automatic initiation; for initiation not subject to will of driver or passenger limiting speed of vehicles other than rail vehicles B60K31/00
• CPC Class Codes: B60T 7/20 specially for trailers, e.g. in case of uncoupling of or overrunning by trailer inertia-actuated overrun brakes B60T13/08

Abstract

A brake system for off-road vehicles of the type including an operator seat, a brake pedal and a hydraulic brake responsive to operator actuation on the brake pedal. The brake system includes a tank for hydraulic fluid, an electric pump hydraulically connected to the tank, a pressure modulating valve actuated by the brake pedal and a flow control valve for controlling the flow of pressurized hydraulic fluid between the pump, pressure modulating valve and brake. During normal braking operation, a switch responsive to operator actuation of the brake pedal causes to provide pressurized hydraulic fluid to the brake through the flow control valve. The return flow of pressurized fluid to the tank is modulated by the pressure modulating valve in response to operator actuation of the brake pedal to control the braking pressure. The flow control valve is responsive to the presence of an operator in the operator compartment, and is coupled to a switch. In the event an unoccupied seat condition is sensed, the switch actuates the pump, and the flow control valve is switched to a flow path which routes all the pressurized fluid to the brake. The brake is thereby automatically actuated when an unoccupied seat condition is sensed. The pressure modulating valve also includes a secondary fail-safe chamber which is actuated by the brake pedal to supply hydraulic fluid to the brake during a fail-safe mode when the pump is not operating.

Claims

1. A hydraulic brake system for a vehicle of the type including an operator seat, a brake pedal and a hydraulic brake responsive to operator actuation of the brake pedal, including:

a tank for hydraulic fluid;

an electric pump hydraulically connected between the tank and brake for providing pressurized hydraulic fluid to the brake; and

a seat condition switch responsive to the presence of an operator in the operator seat, for actuating the pump when an unoccupied seat condition is sensed, and thereby causing pressurized hydraulic fluid to be applied to the brake.

2. The hydraulic brake system of claim 1 and further including:

a flow control valve including an input port hydraulically connected to the electric pump, a first output port hydraulically connected to the brake, a second output port, and a plunger responsive to the presence of operator in the operator seat for switching the valve between first and second flow paths, the first flow path hydraulically coupling the input port to both the first and second output ports when an occupied seat condition is sensed, and the second flow path hydraulically coupling the input port to the first output port and decoupling the second output port from the input port when an unoccupied seat condition is sensed; and

a pressure modulating valve including an input port hydraulically connected to the second output port of the flow control valve, an output port hydraulically coupled to the tank, a modulating fluid flow path between the input and output ports, and a modulator piston responsive to operator actuation of the brake pedal for modulating the flow of pressurized fluid through the modulating fluid flow path and thereby restricting the flow of pressurized hydraulic fluid to the tank and causing the brake to be actuated when the flow control valve is switched to the first flow path.

3. The hydraulic brake system of claim 2 and further including a brake switch coupled to the pump, for actuating the pump in response to operator actuation of the brake pedal.

4. The hydraulic brake system of claim 3 and further including a mechanical linkage coupling the plunger of the flow control valve to the operator seat.

5. The hydraulic brake system of claim 4 wherein the flow control valve includes a biasing mechanism for biasing the plunger so the valve is switched to the second flow path when the unoccupied seat condition is sensed.

6. The hydraulic brake system of claim 3 and further including a mechanical linkage coupling the seat condition switch to the flow control valve plunger.

7. The hydraulic brake system of claim 6 wherein the seat condition switch is mounted to the flow control valve.

8. The hydraulic brake system of claim 3 and further including a solenoid coupled to the seat condition switch for actuating the plunger and switching the flow control valve to its second flow path when the unoccupied seat condition is sensed.

9. The hydraulic brake system of claim 8 wherein the flow control valve is mounted to the pressure modulating valve.

10. The hydraulic brake system of claim 3 wherein:

the system further includes a reverse flow check valve for preventing the flow of hydraulic fluid from the flow control valve to the pump; and

the modulating valve further includes;

a primary piston responsive to operator actuation of the brake pedal;

a fail-safe fluid chamber between the primary piston and the modulator piston; and

a fail-safe fluid flow path and reverse flow check valve in the modulator piston between the fail-safe fluid chamber and the modulating fluid flow path, the pressure modulating valve operating in a modulating mode with the fail-safe chamber acting as a pressure lock and enabling the modulator piston to restrict the flow of pressurized fluid to the tank and actuate the brake in response to operator actuation of the brake pedal when the pump is operating, and the modulating valve operating in a fail-safe mode with the primary piston forcing fluid from the fail-safe chamber through the reverse flow check valve in the modulator piston and out of the modulating valve input port to actuate the brake in response to operator actuation of the brake pedal when the pump is not operating.

11. The hydraulic brake system of claim 10 wherein the modulating valve further includes a replenishing port coupling the modulating fluid flow path to the fail-safe fluid chamber, the replenishing port being closed by the primary piston to provide the pressure lock in response to operator actuation of the brake pedal.

12. The hydraulic brake system of claim 10 wherein the pressure modulating valve further includes a seal for coupling the fail-safe fluid flow path to the pressure modulating valve input port when the pressure modulating valve is operating in the fail-safe mode.

13. A hydraulic brake system for a vehicle of the type including an operator seat, a brake pedal and a hydraulic brake responsive to operator actuation of the brake pedal, including

a tank for hydraulic fluid;

an electric pump hydraulically connected between the tank and brake for providing pressurized hydraulic fluid; and

a pressure modulating valve having a modulating fluid flow path hydraulically connected between the electric pump and the tank, and a modulator piston responsive operator actuation of the brake pedal for modulating the flow of pressurized fluid through the modulating fluid flow path and thereby restricting the flow of pressurized hydraulic fluid to the tank and causing the brake to be actuated.

14. The hydraulic brake system of claim 13 and further including a brake switch coupled to the electric pump, for actuating the pump in response to operator actuation of the brake pedal.

15. The hydraulic brake system of claim 13 wherein:

the system further includes a reverse flow check valve between the electric pump and brake; and

the pressure modulating valve further includes;

a primary piston responsive to operator actuation of the brake pedal;

a fail-safe fluid chamber between the primary piston and the modulator piston; and

a fail-safe fluid flow path and reverse flow check valve in the modulator piston between the fail-safe fluid chamber and the modulating fluid flow path, the pressure modulating valve operating in a modulating mode with the fail-safe chamber acting pressure lock and enabling the modulator piston restrict the flow of pressurized fluid to the flank and actuate the brake in response to operator actuation of the brake pedal when the pump is operating, and the modulating valve operating in a fail-safe mode with the primary piston forcing fluid from the fail-safe chamber through the reverse flow check valve in the modulator piston and out of the modulating valve to the brake, actuate the brake in response to operator actuation of the brake pedal when the pump is not operating.

16. The hydraulic brake system of claim 15 and further including a fluid flow member coupling the brake, pressure modulating valve and pump, the fluid flow member including an input port hydraulically connected to the pump, a first output port hydraulically connected to the brake, and a second output hydraulically connected to an input port of the pressure modulating valve.

17. The hydraulic brake system of claim 16 wherein:

the system further includes a seat condition switch responsive to the presence of an operator in the operator seal and coupled to the pump, for actuating the pump when an unoccupied seat condition is sensed; and

the fluid flow member further includes a plunger responsive the presence of an operator in the operator seat for switching the member between first and second flow paths, the first flow path hydraulically coupling the input to both the first and second output ports when an occupied seat condition is sensed, and the second path hydraulically coupling the input port to the first output port and decoupling the second output port from the input port when an unoccupied seat condition is sensed,

18. The hydraulic brake system of claim 17 and further including a mechanical linkage coupling the plunger of the fluid flow member to the operator seat,

19. The hydraulic brake system of claim 18 wherein the fluid flow member includes a biasing mechanism for biasing the plunger so the member is switched to the second flow path when the unoccupied seat condition is sensed.

20. The hydraulic brake system of claim 17 and further including a mechanical linkage coupling the seat condition switch to the fluid flow member plunger.

21. The hydraulic brake system of claim 20 wherein the seat condition switch is mounted to the fluid flow member.

22. The hydraulic brake system of claim 17 and further including a solenoid coupled to the seat condition switch for actuating the plunger and switching the fluid flow member to its second flow path when the unoccupied seat condition is sensed.

23. The hydraulic brake system of claim 22 wherein the fluid flow member is mounted to the pressure modulating valve.

24. The hydraulic brake system of claim 13 wherein the modulating valve further includes a replenishing port coupling the modulating fluid flow path to the fail-safe fluid chamber, the replenishing port being closed by the primary piston to provide the pressure lock in response to operator actuation of the brake pedal.

25. The hydraulic brake system of claim 13 wherein the pressure modulating valve further includes a seal for coupling the fail-safe fluid flow path to an input port of the pressure modulating valve when the pressure modulating valve is operating in the fail-safe mode.

26. A hydraulic brake system for a vehicle of the type including an operator seat, a brake pedal and a hydraulic brake responsive to operator actuation of the brake pedal, including:

a tank for hydraulic fluid;

an electric pump hydraulically connected to the tank for providing pressurized hydraulic fluid;

a flow control valve including an input port hydraulically connected to the electric pump, a first output pore hydraulically connected to the brake, a second output port, and a plunger responsive to the presence of an operator in the operator seat for switching the valve between first and second flow paths, the first flow path hydraulically coupling the input port to both the first and second output ports when an occupied seat condition is sensed, and the second flow path hydraulically coupling the input port to the first output port and decoupling the second output port from the input port when an unoccupied seat condition is sensed;

a seat condition switch responsive to the presence of an operator in the operator seat, for actuating the pump and causing pressurized hydraulic fluid to be applied to the brake when an unoccupied seat condition is sensed;

a reverse flow check valve between the pump and the second output port of the flow control valve;

a brake switch for actuating the pump in response to operator actuation of the brake pedal; and

a pressure modulating valve including;

an input port hydraulically connected to the second output port of the flow control valve;

an output port hydraulically coupled to the tank;

a modulating fluid flow path between the input and output ports;

a primary piston responsive to operator actuation of the brake pedal;

a modulator piston for modulating the flow of pressurized fluid through the modulating fluid flow path;

a fail-safe fluid chamber between the primary piston and the modulator piston; and

a fail-safe fluid flow path and reverse flow check valve in the modulator piston between the fail-safe fluid chamber and the modulating fluid flow path, the pressure modulating valve operating in a modulating mode with the fail-safe chamber acting as a pressure lock and enabling the modulator piston to restrict the flow of pressurized fluid to the tank and actuate the brake in response to operator actuation of the brake pedal when the pump is operating, and the modulating valve operating in a fail-safe mode with the primary piston forcing fluid from the fail-safe chamber through the reverse flow check valve in the modulator piston and out of the input port of the modulating valve to the brake, to actuate the brake in response to operator actuation of the brake pedal when the pump is not operating.

27. The hydraulic brake system of claim 26 and further including a mechanical linkage coupling the plunger of the flow control valve to the operator seat.

28. The hydraulic brake system of claim 27 wherein the flow control valve includes a biasing mechanism for biasing the plunger so the valve is switched to the second flow path when the unoccupied seat condition is sensed.

29. The hydraulic brake system of claim 27 and further including a mechanical linkage coupling the seat condition switch to the flow control valve plunger.

30. The hydraulic brake system of claim 29 wherein the seat condition switch is mounted to the flow control valve.

31. The hydraulic brake system of claim 26 and further including a solenoid coupled to the seat condition switch for actuating the plunger and switching the flow control valve to its second flow path when the unoccupied seat condition is sensed.

32. The hydraulic brake system of claim 31 wherein the flow control valve is mounted to the pressure modulating valve.

33. The hydraulic brake system of claim 26 wherein the modulating valve further includes a replenishing port coupling the modulating fluid flow path to the fail-safe fluid chamber, the replenishing port being closed by the primary piston to provide the pressure lock in response to operator actuation of the brake pedal.

34. The hydraulic brake system of claim 26 wherein the pressure modulating valve further includes a seal for coupling the fail-safe fluid flow path to the pressure modulating valve input port when the pressure modulating valve is operating in the fail-safe mode.