METHOD FOR WHEN NECESSARY AUTOMATICALLY LIMITING A PRESSURE IN A HYDRAULIC SYSTEM DURING OPERATION

• US 20100263735A1
• Filed: 12/12/2007
• Published: 10/21/2010
• Est. Priority Date: 12/12/2007
• Status: Active Grant

• Current Assignee: Volvo Construction Equipment AB (Volvo AB)
• Original Assignee: Volvo Construction Equipment AB (Volvo AB)
• Inventors: Vigholm, Bo, Ekvall, Andreas
• Granted Patent: US 8,695,333 B2
• Time in Patent Office: Days
• US Class Current: 137/14
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2228 including an electronic controller
• CPC Class Codes: E02F 9/2235 including an electronic controller
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: Y10T 137/0396 Involving pressure control

Abstract

A method is provided for, when necessary, automatically limiting a pressure in a hydraulic system during operation. A system is arranged to deliver pressurized hydraulic fluid to at least one fluid actuated device arranged to perform a work function, where the procedure includes sensing a pressure in at least one position of the system, comparing the detected pressure value, or an associated value, with a first predefined pressure limit, and opening a communication of fluid between the fluid actuated device and a reservoir through a first conduit if the sensed pressure value, or an associated value, exceeds the predefined limit.

Claims

1. Method for automatically limiting a pressure generated during operation in a hydraulic system when needed, system being adapted to deliver a pressurized hydraulic fluid to at least one actuator arranged to perform a work function by means of an implement of a working machine, wherein the method comprises the steps of:

detecting a pressure in at least one position in the system;

comparing the detected pressure value, or a value associated with the detected pressure value, with a first predetermined limit value; and

opening a flow communication between the actuator and a tank via a first conduit if the detected pressure value, or the value associated with the detected pressure value/exceeds the predetermined limit value,

detecting an operating parameter which is indicative of a position of the implement and determining the limit value on the basis of the detected operating parameter.

2. Method according to claim 1, wherein the flow communication is opened via a control valve being arranged on the first conduit and having the function to control the supply of the hydraulic fluid to and from, respectively, the actuator with the purpose of performing the work function.

3. Method according to claim 2, comprising the step of opening the control valve via an electrical signal.

4. Method according to claim 1, wherein a first control valve is arranged on a conduit connecting to a first side of the actuator and a second control valve is arranged on a conduit connecting to a second side of the actuator, comprising the step of detecting the pressure on least one of these actuator sides and opening the control valve (207, 223) to tank, which is arranged on the side where increased pressure has been generated.

5. Method according to claim 1, further comprising the step of opening a flow communication between the actuator and the tank via a second conduit via a shock valve.

6. Method according to claim 5, wherein the shock valve is passive.

7. Method according to claim 5, wherein the shock valve is spring-loaded,

8. Method according to claim 5, wherein the first and second conduit are connected to the same side of the actuator,

9. Method according to claim 2, comprising opening a flow communication between the actuator and the tank via a second conduit is a shock valve, wherein the control valve drains a larger flow to tank than the shock valve does.

10. Method according to claim 1, further comprising the steps of detecting the pressure when flow communication between the actuator and the tank via the first conduit has been opened, and closing flow communication between the actuator and the tank via the fist conduit if the pressure value, or the value associated with the detected pressure value, falls short of a second predetermined limit value being lower than the first limit value.

11. Method according to claim 1, comprising the step of detecting the pressure of the actuator.

12. Method according to claim 1, comprising the step of detecting a level of the pressure in position in the system, comparing the pressure level with a first predetermined limit value for the pressure level, and opening the flow communication between the actuator and the tank via the first conduit if the pressure level exceeds the predetermined limit value.

13. Method according to claim 1, comprising the step of determining a derivative of the pressure in position in the system, comparing the pressure derivative with a first predetermined limit value for the pressure derivative, and opening the flow communication between the actuator and the tank via the first conduit if the pressure derivative exceeds the predetermined limit value,

14. Method according to claim 1, comprising the step of determining the limit value on the basis of the actual operating condition,

15. Method according to claim 1, comprising the step of detecting at least one operating parameter and determining the limit value on the basis of the detected operating parameter.

16. Method according to claim 1, comprising the step of detecting at least one operating parameter repeatedly and determining the limit value based upon how the work function is performed.

17. Method according to claim 1, comprising the steps of controlling a plurality of work functions, including lifting and tilting of an implement.

18. Method according to claim 1, wherein different limit values are associated with at least two of the work functions, wherein the method comprises the step of selecting the limit value which is associated with the work function being performed, for comparison.

19. Method according to claim 1, comprising the steps of controlling a working machine, working machine comprising system.

20. Method according to claim 19, comprising the step of detecting an operating parameter which is indicative of the type of implement being actuated via the actuator and determining the limit value on the basis of the detected implement type.

21. Method according to claim 19, comprising the step of detecting an operating parameter which is indicative of the type of handling being performed with the machine and determining the limit value on the basis of the detected type of handling operation.

22. Method according to claim 20, comprising the step of detecting an operating parameter which is indicative of a machine speed and determining the limit value on the basis of the detected machine speed.

23. Method according to claim 1, comprising the step of determining the flow rate to the tank on the basis of the detected pressure.