Hydraulic system

• US 8,910,474 B2
• Filed: 10/21/2011
• Issued: 12/16/2014
• Est. Priority Date: 10/21/2011
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Knussman, Michael L., Edler, Brad A., Opdenbosch, Patrick
• Primary Examiner(s): Lazo, Thomas E
• Application Number:
  US13/278,895
• Publication Number:
  US 20130098024A1
• Time in Patent Office: 1,152 Days
• Field of Search: 604/20, 604/21, 604/22, 604/86
• US Class Current: 60/422
• CPC Class Codes: E02F 9/2242 including an electronic controller
• CPC Class Codes: E02F 9/2289 Closed circuit
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/30575 in a Wheatstone Bridge arrangement (also half bridges)
• CPC Class Codes: F15B 2211/30595 with additional valves between the groups of valves for multiple output members
• CPC Class Codes: F15B 2211/613 Feeding circuits
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups
• CPC Class Codes: F15B 2211/785 Compensation of the difference in flow rate in closed fluid circuits using differential actuators
• CPC Class Codes: F15B 7/001 With multiple inputs, e.g. for dual control
• CPC Class Codes: F15B 7/003 with multiple outputs
• CPC Class Codes: F15B 7/006 Rotary pump input
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A hydraulic system includes a first pump, a first actuator fluidly connected to the first pump via a first closed-loop circuit, a second pump, and a second actuator fluidly connected to the second pump via a second closed-loop circuit. The system also includes a third pump, a third actuator fluidly connected to the third pump via a third closed-loop circuit, a fourth pump, and a fourth actuator fluidly connected to the fourth pump via a fourth closed-loop circuit. The system further includes a first combining valve configured to combine fluid from the first and second circuits, a second combining valve configured to combine fluid from the second and third circuits, and a third combining valve configured to combine fluid from the third and fourth circuits. The system also includes a fourth combining valve configured to combine fluid from the first and fourth circuits.

Claims

1. A hydraulic system, comprising:

a variable displacement first pump;

a first actuator fluidly connected to the first pump via a first closed-loop circuit;

a variable displacement second pump;

a second actuator fluidly connected to the second pump via a second closed-loop circuit;

a variable displacement third pump;

a third actuator fluidly connected to the third pump via a third closed-loop circuit;

a variable displacement fourth pump;

a fourth actuator fluidly connected to the fourth pump via a fourth closed-loop circuit;

a first combining valve configured to selectively combine fluid from the first and second circuits;

a second combining valve configured to selectively combine fluid from the second and third circuits;

a third combining valve configured to selectively combine fluid from the third and fourth circuits; and

a fourth combining valve configured to selectively combine fluid from the first and fourth circuits.

2. The system of claim 1, wherein the first and fourth actuators comprise linear actuators, and wherein the second and third actuators comprise rotary actuators.

3. The system of claim 2, wherein the rotary actuators comprise fixed displacement actuators, the system further comprising first, second, third, and fourth switching valves associated with the first, second, third, and fourth actuators, respectively, and configured to selectively switch a flow direction of fluid passing through the respective actuators.

4. The system of claim 3, wherein the first and fourth switching valves comprise a plurality of variable position valves configured to reduce a speed of the first and fourth actuators, respectively, during regeneration of the respective actuators.

5. The system of claim 4, wherein the second and third switching valves comprise variable position four-way valves, and each valve of the plurality of variable position valves comprises a variable position two-way valve.

6. The system of claim 3, wherein the first, second, third, and fourth switching valves are configured to variably restrict flow through the first, second, third, and fourth actuators, respectively, while receiving a combined flow via one or more of the combining valves.

7. The system of claim 3, wherein the fourth combining valve is configured to combine fluid from the first and fourth circuits, during simultaneous operation of the first and fourth actuators, in response to a demand of the first actuator exceeding a capacity of the first pump and in response to a demand of the fourth actuator exceeding a capacity of the fourth pump.

8. The system of claim 7, wherein the first and fourth switching valves are configured to variably restrict flow through the first and fourth actuators, respectively, while fluid from the first and fourth circuits is combined via the fourth combining valve.

9. The system of claim 7, wherein the first switching valve is configured to selectively switch the flow direction of fluid passing through the first actuator independent of the flow direction of fluid passing through the fourth actuator, while fluid from the first and fourth circuits is combined via the fourth combining valve.

10. The system of claim 3, wherein the first combining valve is configured to combine fluid from the first and second circuits, during simultaneous operation of the first and forth actuators, in response to a demand of the first actuator exceeding a capacity of the first pump.

11. The system of claim 10, wherein the second combining valve is configured to combine fluid from the third circuit with fluid from the first and second circuits, during simultaneous operation of the first and forth actuators, in response to a demand of the first actuator exceeding a combined capacity of the first and second pumps.

12. The system of claim 3, wherein during simultaneous operation of the first and fourth actuators the first combining valve is configured to combine fluid from the first and second circuits, the third combining valve is configured to combine fluid from the third and fourth circuits, and the fourth combining valve is configured to combine fluid from the first and fourth circuits, in response to a demand of the first actuator exceeding a combined capacity of the first, second, and third pumps.

13. A hydraulic system, comprising:

a variable displacement first pump;

first and second linear actuators associated with a boom of a machine, the first and second linear actuators being fluidly connected to the first pump via a first closed-loop circuit;

a variable displacement second pump;

a first travel motor associated with a first traction device of the machine, the first travel motor being fluidly connected to the second pump via a second closed-loop circuit;

a variable displacement third pump;

a second travel motor associated with a second traction device of the machine, the second travel motor being fluidly connected to the third pump via a third closed-loop circuit;

a variable displacement fourth pump;

a third linear actuator associated with a machine stick, the third linear actuator being fluidly connected to the fourth pump via a fourth closed loop circuit;

a first combining valve configured to selectively combine fluid from the first and second circuits;

a second combining valve configured to selectively combine fluid from the second and third circuits;

a third combining valve configured to selectively combine fluid from the third and fourth circuits; and

a fourth combining valve configured to selectively combine fluid from the first and fourth circuits, wherein the first, second, and third linear actuators are configured to operate simultaneously while fluid from the first and fourth circuits is combined.

14. The system of claim 13, further comprising a first switching valve associated with the first and second linear actuators, a second switching valve associated with the first travel motor, a third switching valve associated with the second travel motor, and a fourth switching valve associated with the third linear actuator, the first, second, third, and fourth switching valves being configured to selectively switch a flow direction of fluid passing through the respective actuators.

15. The system of claim 14, wherein the first switching valve is configured to variably restrict flow through the first and second linear actuators while the first switching valve receives a combined flow of fluid.

16. The system of claim 14, wherein during simultaneous operation of the first, second, and third linear actuators, the first combining valve is configured to combine fluid from the first and second circuits, the third combining valve is configured to combine fluid from the third and fourth circuits, and the fourth combining valve is configured to combine fluid from the first and fourth circuits, in response to a demand of the first and second linear actuators exceeding a combined capacity of the first, second, and third pumps.

17. The system of claim 16, wherein the first switching valve is configured to variably restrict flow through the first and second linear actuators while the first switching valve receives a combined flow of fluid.

18. The system of claim 17, wherein the switching valve is configured to change a speed of the first and second linear actuators, independent of a speed of the third linear actuator, while the first switching valve receives the combined flow of fluid.

19. The system of claim 14, wherein the first switching valve comprises a plurality of variable position valves configured to reduce a speed of the first and second linear actuators during regeneration of the first and second actuators.

20. The system of claim 13, further comprising

a variable displacement fifth pump,

a third rotary actuator associated with a body of the machine, the third rotary actuator being fluidly connected to the fifth pump via a fifth closed-loop circuit,

a variable displacement sixth pump, and

a fourth linear actuator associated with a work tool of the machine, the fourth linear actuator being fluidly connected to the sixth pump via a sixth closed-loop circuit.