Pressure compensated hydraulic system having differential pressure control

Patent metadata

Field	Value
Publication number	US-9429175-B2
Application number	US-201113697473-A
Country	US
Kind code	B2
Filing date	May 11, 2011
Priority date	May 11, 2010
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

A hydraulic control valve assembly ( 10 ), method and system, characterized by control valves ( 26 ) each having a variable metering orifice; a compensator ( 28 ) that controls flow of fluid from the variable metering orifice to a work port (A,B) in response to a differential in pressures acting on opposite first and second sides of the compensator, wherein a first side receives a pressure at the downstream side of the variable metering orifice; a load sense passage ( 34 ) providing a load sense pressure; and a differential pressure controller ( 40 ) having a first inlet connected to a pump supply port and a second inlet connected to the load sense passage, the controller having a first operational mode in which load sense pressure at the second inlet is supplied to an outlet of the controller and a second operational mode in which flow from the first inlet is metered to the outlet of the controller to provide a differential control output pressure, and wherein an outlet of the differential pressure controller is connected to a pump control port and/or to the second side of the pressure compensating valve of at least one of the control valves.

First claim

The invention claimed is:

1. A hydraulic control valve assembly comprising
plural control valves each having a variable metering orifice through which hydraulic fluid flows between an inlet port providing for connection to a load sense margin pressure source and a respective work port providing for connection to a respective actuator;
a compensator that receives flow of fluid from the variable metering orifice and directs it to the work port of each control valve in response to a differential in pressures acting on opposite first and second sides of the compensator, wherein the first side receives a pressure at the downstream side of the variable metering orifice;
a load sense passage connected to the control valves to provide a load sense pressure corresponding to the greatest pressure amongst the work ports; and
a differential pressure controller having a first inlet connected to the inlet port and a second inlet connected to the load sense passage, the differential pressure controller having a first operational mode in which load sense pressure at the second inlet is supplied to an outlet of the differential pressure controller and a second operational mode in which flow from the first inlet is metered to the outlet of the differential pressure controller to provide a differential control output pressure at the outlet of the differential pressure controller, and
wherein the outlet of the differential pressure controller is connected to (a) a control port to which can be connected the control port of the load sense margin pressure source that produces an output pressure of the source that is a predefined amount greater than the pressure supplied to the control port of the source, and/or (b) the second side of the pressure compensating valve of at least one of the plural control valves.

2. The hydraulic control valve assembly according to claim 1 , wherein each control valve has a respective compensator, and each compensator that is not connected to the outlet of the differential pressure controller, has the second side connected to load sense passage.

3. The hydraulic control valve assembly according to claim 1 , wherein differential pressure controller is configured to provide a differential control output pressure that is greater than the load sense pressure.

4. The hydraulic control valve assembly according to claim 1 , wherein the differential pressure controller includes a controller valve that in the second operational mode provides a pressure drop corresponding to a control force applied to the controller valve.

5. The hydraulic control valve assembly according to claim 1 , wherein the control force is selected to provide a predetermined pressure difference between the differential control output pressure and the load sense pressure.

6. The hydraulic control valve assembly according to claim 1 , including a control device for providing the control force.

7. The hydraulic control valve assembly according to claim 6 , wherein the control device is a solenoid, proportional solenoid, hydraulic or pneumatic pressure source, adjustable spring mechanism, stepper motor, bi-directional pilot valve, or similar device.

8. The hydraulic control valve assembly according to claim 1 , wherein the control device is configured to provide different control forces during shifting of the differential pressure controller between its first and second operation modes.

9. The hydraulic control valve assembly according to claim 1 , wherein the controller valve is biased to a position corresponding the first operation mode.

10. The hydraulic control valve assembly according to claim 1 , wherein the outlet of the differential pressure controller is connected to the control port via a pressure gain mechanism that operates in one position to restrict flow greater than in a second position.

11. The hydraulic control valve assembly according to claim 1 , wherein the differential pressure controller in the second operational mode supplies to its outlet a pressure higher than the load sense pressure, whereby the control valves that have the compensators thereof receiving the outlet pressure of the differential pressure controller will have the flow output reduced.

12. The hydraulic control valve assembly according to claim 1 , wherein the differential pressure controller in the second operation mode increases pressure on the second side of the pressure compensating valve while the inlet port pressure is unchanged to stop output flow of is used to deactivate one or more work sections respectively associated with the control valves.

13. The hydraulic control valve assembly according to claim 1 , wherein the differential pressure controller in the second operation mode increases the inlet port pressure while pressure on the second side of the pressure compensating valve is unchanged is used to boost output flow of one or more work sections respectively associated with the control valves.

14. The hydraulic control valve assembly according to claim 1 , wherein the differential pressure controller in the second operation mode increases pressure on the second side of the pressure compensating valve while the inlet port pressure is unchanged is used to reduce output flow of one or more work sections respectively associated with the control valves.

15. The hydraulic control valve assembly according to claim 1 , wherein the differential pressure controller is used to reduce the responsiveness of one or more work sections respectively associated with the control valves.

16. A hydraulic control system comprising a hydraulic control valve assembly according to claim 1 , a pump connected to the inlet port, and an actuator connected to the work port of a respective control valve.

17. An excavator comprising a hydraulic control system according to claim 16 .

18. A method of controlling a hydraulic system wherein plural control valves each have a variable metering orifice through which hydraulic fluid flows between an inlet port providing for connection to a pump and a respective work port providing for connection to a respective actuator, comprising the steps of:
using a compensator to control flow of fluid from the variable metering orifice to the work port of each control valve in response to a differential in pressures acting on opposite first and second sides of the compensator, wherein the first side receives a pressure at the downstream side of the variable metering orifice;
providing a load sense pressure corresponding to the greatest pressure amongst the work ports; and
using a differential pressure controller having a first inlet connected to the pump supply port and a second inlet connected to the load sense passage, the differential pressure controller having a first operational mode in which load sense pressure at the second inlet is supplied to an outlet of the differential pressure controller and a second operational mode in which flow from the first inlet is metered to the outlet of the differential pressure controller to provide a differential control output pressure at the outlet of the differential pressure controller, and
wherein the outlet of the differential pressure controller is connected to (a) a pump control port to which can be connected the control port of a variable displacement pump that produces an output pressure of the pump that is a predefined amount greater than the pressure supplied to the control port of the pump, and/or (b) the second side of the pressure compensating valve of at least one of the plural control valves.

19. A valve assembly comprisin

Assignees

• Coolidge Gregory T
• Parker Hannifin Corp

Inventors

• Coolidge Gregory T

Classifications

• Y10T137/85986

  Pumped fluid control · CPC title

• F15B2211/20553

  with pilot circuit, e.g. for controlling a swash plate · CPC title

• F15B2211/30555

  Inlet and outlet of the pressure compensating valve being connected to the directional control valve · CPC title

• F15B21/06 Primary

  Use of special fluids, e.g. liquid metal; Special adaptations of fluid-pressure systems, or control of elements therefor, to the use of such fluids · CPC title

• F15B2211/653

  the load sensing pressure being higher than the load pressure · CPC title