Hydraulic System and Work Machine Comprising Such a System

• US 20070234718A1
• Filed: 06/22/2005
• Published: 10/11/2007
• Est. Priority Date: 07/28/2004
• Status: Active Grant

• Current Assignee: Volvo Construction Equipment Holding Sweden AB
• Original Assignee: Volvo Construction Equipment Holding Sweden AB
• Inventors: Vigholm, Bo
• Granted Patent: US 7,464,545 B2
• Time in Patent Office: Days
• US Class Current: 60/468
• CPC Class Codes: B62D 5/07 Supply of pressurised fluid for steering also supplying other consumers ; control thereof
• CPC Class Codes: E02F 9/2239 using two or more pumps with cross-assistance
• 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 11/165 for adjusting the pump output or bypass in response to demand
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20592 Combinations of pumps for supplying high and low pressure
• CPC Class Codes: F15B 2211/251 High pressure control
• CPC Class Codes: F15B 2211/30505 Non-return valves, i.e. check valves
• CPC Class Codes: F15B 2211/30525 Directional control valves, e.g. 4/3-directional control valve
• CPC Class Codes: F15B 2211/31576 having a single pressure source and a single output member
• CPC Class Codes: F15B 2211/31594 having multiple pressure sources and multiple output members
• CPC Class Codes: F15B 2211/45 Control of bleed-off flow, e.g. control of bypass flow to the return line
• CPC Class Codes: F15B 2211/6054 using shuttle valves
• CPC Class Codes: F15B 2211/781 one or more output members having priority

Abstract

A hydraulic system includes a first pump that delivers hydraulic fluid to a first load outlet point and to a second load outlet point, a second pump that delivers hydraulic fluid to the second load outlet point, but not to the first load outlet point, a pressure detector for detecting the load pressure at the first load outlet point and a pressure detector for detecting the load pressure at the second load outlet point. The system includes a controller for controlling the first pump on the basis of the detected load pressure at the first load outlet point and the detected load pressure at the second load outlet point, and a controller for controlling the second pump on the basis of the detected load pressure at the second load outlet point but not on the basis of the detected load pressure at the first load outlet point.

Claims

1. A hydraulic system, comprising

a first pump that delivers hydraulic fluid to a first load outlet point and to a second load outlet point,

a second pump that delivers hydraulic fluid to the second load outlet point but not to the first load outlet point,

a pressure detector for detecting load pressure at the first load outlet point,

a pressure detector for detecting load pressure at the second load outlet point,

a control arrangement for controlling the first pump based on a detected load pressure at the first load outlet point and the detected load pressure at the second load outlet point, and

a control arrangement for controlling the second pump based on a detected load pressure at the second load outlet point but not based on the detected load pressure at the first load outlet point.

2. The hydraulic system as claimed in claim 1, comprising a non-return valve arranged on the second pump, with the non-return valve being arranged to prevent a flow in the direction towards the second pump and through this to the tank.

3. The hydraulic system as claimed in claim 1, comprising a priority valve that controls flow of hydraulic fluid from the first pump to the first load outlet point and the second load outlet point, with the priority valve being arranged to prioritize the flow to the first load outlet point.

4. The hydraulic system as claimed in claim 1, wherein the first pump has a higher control pressure than the second pump.

5. A work machine, comprising a hydraulic system as claimed in claim 1.

6. A work machine as claimed in claim 5, wherein the first load outlet point is associated with a steering function of the work machine.

7. The work machine as claimed in claim 5, wherein the second load outlet point is associated with a work function of the work machine.

8. The work machine as claimed in claim 7, wherein the working machine has a lifting unit and the work function is a raising, lowering or tilting function of the lifting unit.

9. The work machine as claimed in claim 5, comprising a motor for propulsion of the work machine and for driving the hydraulic system.

10. The work machine as claimed in claim 6, wherein the second load outlet point is associated with a work function of the work machine.

11. The work machine as claimed in claim 10, wherein the working machine has a lifting unit and the work function is a raising, lowering or tilting function of the lifting unit.

12. The work machine as claimed in claim 6, comprising a motor for propulsion of the work machine and for driving the hydraulic system.

13. The hydraulic system as claimed in claim 2, comprising a priority valve that controls the flow of hydraulic fluid from the first pump to the first load outlet point and the second load outlet point, with the priority valve being arranged to prioritize the flow to the first load outlet point.

14. The hydraulic system as claimed in claim 13, wherein the first pump has a higher control pressure than the second pump.

15. The hydraulic system as claimed in claim 3, wherein the first pump has a higher control pressure than the second pump.

16. A work machine, comprising a hydraulic system as claimed in claim 2.

17. A work machine, comprising a hydraulic system as claimed in claim 3.

18. A work machine, comprising a hydraulic system as claimed in claim 4.