Meterless hydraulic system having load-holding bypass

• US 8,863,509 B2
• Filed: 08/31/2011
• Issued: 10/21/2014
• Est. Priority Date: 08/31/2011
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Opdenbosch, Patrick, Knussman, Michael L., Dierking, Joshua
• Primary Examiner(s): Lazo, Thomas E
• Application Number:
  US13/222,990
• Publication Number:
  US 20130047599A1
• Time in Patent Office: 1,147 Days
• Field of Search: 604/64, 604/66, 914/45, 914/47
• US Class Current: 60/466
• CPC Class Codes: E02F 9/2228 including an electronic controller
• CPC Class Codes: E02F 9/2267 Valves or distributors position of valves arrangements on upper-structures E02F9/0875
• 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 2211/20523 Internal combustion engine
• CPC Class Codes: F15B 2211/20553 with pilot circuit, e.g. for controlling a swash plate
• CPC Class Codes: F15B 2211/20561 reversible
• CPC Class Codes: F15B 2211/20569 capable of working as pump and motor
• CPC Class Codes: F15B 2211/27 Directional control by means of the pressure source
• CPC Class Codes: F15B 2211/30515 Load holding valves
• CPC Class Codes: F15B 2211/50527 using cross-pressure relief valves
• CPC Class Codes: F15B 2211/613 Feeding circuits
• CPC Class Codes: F15B 2211/7053 Double-acting output members
• CPC Class Codes: F15B 7/006 Rotary pump input
• CPC Class Codes: F16D 48/02 Control by fluid pressure
• CPC Class Codes: Y10T 137/7858 With means for selecting area of valve or seat

Abstract

A hydraulic system is disclosed. The hydraulic system may have a pump, a hydraulic actuator, and first and second passages fluidly connecting the pump to the hydraulic actuator in a closed-loop. The hydraulic system may also have a control valve, and a load-holding valve configured to selectively lock movement of the hydraulic actuator. The load-holding valve may include a valve block at least partially defining a pump passage, an actuator passage, a control passage, a restricted passage connecting the actuator passage and the control passage, and a bypass passage connecting the actuator passage and the control passage. The load-holding valve may also include a valve element movable between a first position at which flow between the pump and the hydraulic actuator is blocked, and a second position at which fluid is allowed to flow between the pump and the hydraulic actuator, the valve element being spring-biased toward the first position.

Claims

1. A load-holding valve, comprising:

a valve block at least partially defining;

a pump passage;

an actuator passage;

a control passage;

a restricted passage connecting the actuator passage and the control passage; and

a bypass passage connecting the actuator passage and the control passage; and

a valve element disposed within the valve block and movable between a first position at which fluid flow between the pump passage and actuator passage is blocked, and a second position at which fluid is allowed to flow between the pump passage and the actuator passage.

2. The load-holding valve of claim 1, further including a check element disposed within the bypass passage and configured to allow fluid to flow in one direction from only the control passage to the actuator passage.

3. The load-holding valve of claim 1, wherein the valve element is spring-biased toward the first position.

4. The load-holding valve of claim 1, wherein the valve element is a poppet type element.

5. The load-holding valve of claim 4, wherein the valve element includes:

a nose portion always in fluid communication with the actuator passage; and

a base portion always in fluid communication with the control passage.

6. The load-holding valve of claim 5, wherein the valve element also includes a shoulder portion always in fluid communication with the pump passage.

7. The load-holding valve of claim 6, wherein:

fluid acting on the base portion creates a force urging the valve element toward the first position; and

fluid acting on the nose portion and the shoulder portion together creates a force urging the valve element toward the second position.

8. The load-holding valve of claim 7, wherein a pressure area of the base portion is greater than a pressure area of the nose portion.

9. The load-holding valve of claim 7, wherein when the control passage is connected with a low-pressure tank, the valve element is allowed to move toward the second position.

10. The load-holding valve of claim 9, wherein when the control passage is blocked from the low-pressure tank, fluid from the actuator passage is allowed to build pressure at the base portion and urge the valve element toward the first position.

11. A hydraulic system, comprising:

a pump;

a hydraulic actuator;

first and second passages fluidly connecting the pump to the hydraulic actuator in a closed-loop manner;

a control valve; and

a load-holding valve associated with at least one of the first and second passages and configured to selectively lock movement of the hydraulic actuator, the load-holding valve comprising;

a valve block at least partially defining;

a pump passage in fluid communication with the pump;

an actuator passage in fluid communication with the hydraulic actuator via the one of the first and second passages;

a control passage in fluid communication with the control valve;

a restricted passage fluidly connecting the actuator passage and the control passage;

a bypass passage connecting the actuator passage and the control passage; and

a valve element disposed within the valve block and movable between a first position at which fluid flow between the pump and the hydraulic actuator is blocked, and a second position at which fluid is allowed to flow between the pump and the hydraulic actuator, wherein the valve element is spring-biased toward the first position.

12. The hydraulic system of claim 11, wherein the load-holding valve further includes a check element disposed within the bypass passage and configured to allow fluid to flow in one direction from only the control passage to the actuator passage.

13. The hydraulic system of claim 11, wherein the valve element is a poppet type element having:

a nose portion always in fluid communication with the actuator passage;

a base portion always in fluid communication with the control passage; and

a shoulder portion always in fluid communication with the pump passage.

14. The hydraulic system of claim 13, wherein:

fluid acting on the base portion of the valve element creates a force urging the valve element toward the first position; and

fluid acting on the nose and shoulder portions of the valve element together creates a force urging the valve element toward the second position.

15. The hydraulic system of claim 14, wherein a pressure area of the base portion is greater than a pressure area of the nose portion.

16. The hydraulic system of claim 11, further including:

a tank; and

a controller in communication with the control valve and configured to selectively cause the control valve to move between a first position at which the control passage is fluidly communicated with the tank, and a second position at which the control passage is blocked from the tank,

wherein;

when the control passage is fluidly communicated with the tank, the valve element of the load-holding valve is allowed to move to the second position; and

when the control passage is blocked from the tank, the valve element of the load-holding valve is urged toward the second position.

17. The hydraulic system of claim 16, further including an operator interface device, wherein the controller is configured to selectively cause the control valve to move based on input from the operator interface device.

18. The hydraulic system of claim 17, wherein the control valve is caused to move to the first position when an operator stops requesting movement of the hydraulic actuator via the operator interface device.

19. The hydraulic system of claim 11, wherein:

the load-holding valve is a first load-holding valve associated with the first passage; and

the hydraulic system includes a second load holding valve substantially identical to the first load-holding valve and associated with the second passage.

20. The hydraulic system of claim 11, further including a pressure relief valve configured to selectively relieve a pressure of fluid from a location between the load-holding valve and the hydraulic actuator.

21. The hydraulic system of claim 20, further including a resolver configured to selectively direct fluid from between the pump and the load-holding valve and fluid from between the load-holding valve and the hydraulic actuator to the pressure relief valve based on a pressure of the fluid.

22. A hydraulic system, comprising:

a tank;

a pump;

a hydraulic actuator;

first and second passages fluidly connecting the pump to the hydraulic actuator in a closed-loop manner;

a control valve;

an operator interface device;

a controller in communication with the control valve and the operator interface device; and

first and second load-holding valves associated with the first and second passages, respectively, and configured to selectively lock movement of the hydraulic actuator, each of the first and second load-holding valves comprising;

a valve block at least partially defining;

a pump passage in fluid communication with the pump;

an actuator passage in fluid communication with the hydraulic actuator via the first or second passages;

a control passage in fluid communication with the control valve;

a restricted passage fluidly connecting the actuator passage and the control passage; and

a bypass passage connecting the actuator passage and the control passage;

a check element disposed within the bypass passage and configured to allow fluid to flow in one direction from only the control passage to the actuator passage; and

a valve element disposed within the valve block and movable between a first position at which fluid flow between the pump and the hydraulic actuator is blocked, and a second position at which fluid is allowed to flow between the pump and the hydraulic actuator, wherein the valve element is spring-biased toward the first position,

wherein;

the controller is configured to selectively cause the control valve to move between a first position at which the control passage is fluidly communicated with the tank, and a second position at which the control passage is blocked from the tank based on input from the operator interface device;

when the control passage is fluidly communicated with the tank, the valve element of each of the first and second load-holding valves is allowed to move to the second position; and

when the control passage is blocked from the tank, the valve element of each of the first and second load-holding valves is urged toward the second position.