Hydraulic system having priority based flow control

• US 7,146,808 B2
• Filed: 10/29/2004
• Issued: 12/12/2006
• Est. Priority Date: 10/29/2004
• Status: Active Grant

• Current Assignee: Caterpillar Sarl (Caterpillar Incorporated)
• Original Assignee: Caterpillar Incorporated, Shin Caterpillar Mitsubishi Ltd. (Caterpillar Incorporated)
• Inventors: Tozawa, Shoji, Verkuilen, Michael T., Devier, Lonnie J.
• Primary Examiner(s): Lazo, Thomas E.
• Application Number:
  US10/975,418
• Publication Number:
  US 20060090459A1
• Time in Patent Office: 774 Days
• Field of Search: 604/22, 604/59, 604/45
• US Class Current: 60/422
• CPC Class Codes: E02F 9/2246 Control of prime movers, e.g. depending on the hydraulic load of work tools
• CPC Class Codes: F15B 11/162 for giving priority to particular servomotors or users
• CPC Class Codes: F15B 11/163 for sharing the pump output equally amongst users or groups of users, e.g. using anti-saturation, pressure compensation
• CPC Class Codes: F15B 2211/255 Flow control functions
• CPC Class Codes: F15B 2211/40515 with variable throttles or orifices
• CPC Class Codes: F15B 2211/41527 being connected to an output member and a directional control valve
• CPC Class Codes: F15B 2211/455 Control of flow in the feed line, i.e. meter-in control
• CPC Class Codes: F15B 2211/6323 the flow rate being a pressure source flow rate
• CPC Class Codes: F15B 2211/6326 the flow rate being an output member flow rate
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/6654 Flow rate control
• CPC Class Codes: F15B 2211/71 Multiple output members, e.g. multiple hydraulic motors or cylinders
• CPC Class Codes: F15B 2211/75 Control of speed of the output member

Abstract

A hydraulic system has a source, a plurality of fluid actuators, and a controller. The controller is configured to receive an input indicative of which of the plurality of fluid actuators are a first and a second type of fluid actuator, to receive an input indicative of a desired flow rate for the plurality of fluid actuators, and to determine a current flow rate of the source. The controller is further configured to demand the desired flow rate for the first type of fluid actuator and to demand a scaled down desired flow rate for the second type of fluid actuator when a total desired flow rate exceeds the current flow rate of the source, and to demand a scaled down desired flow rate for all of the plurality of fluid actuators when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source.

Claims

1. A hydraulic system, comprising:

a tank configured to hold a supply of fluid;

a source configured to pressurize the fluid;

a plurality of fluid actuators configured to receive the pressurized fluid; and

a controller configured to;

receive an input indicative of which of the plurality of fluid actuators are a first type of fluid actuator and which of the plurality of fluid actuators are a second type of fluid actuator;

receive an input indicative of a desired flow rate for the plurality of fluid actuators;

determine a current flow rate of the source;

demand the desired flow rate for the first type of fluid actuator and demand a scaled down desired flow rate for the second type of fluid actuator when a total desired flow rate for the plurality of fluid actuators exceeds the current flow rate of the source; and

demand a scaled down desired flow rate for all of the plurality of fluid actuators when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source.

2. The hydraulic system of claim 1, wherein the controller is configured to receive an input indicative of a priority for each of the second type of fluid actuators and to scale down the desired flow rate for the second type of fluid actuator according to the priority when the total desired flow rate for the plurality of fluid actuators exceeds the current flow rate of the source.

3. The hydraulic system of claim 1, wherein the controller is configured to determine a priority for each of the plurality of fluid actuators when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source.

4. The hydraulic system of claim 3, wherein the priority for each of the first type of fluid actuator is the same.

5. The hydraulic system of claim 3, wherein the controller is configured to receive an input indicative of desired priorities for the second type of fluid actuator and the determined priorities are calculated based on the desired priorities.

6. The hydraulic system of claim 5, wherein the determined priorities for the first type of fluid actuator are greater than the determined priorities for the second type of fluid actuator.

7. The hydraulic system of claim 1, wherein the controller is further configured to adjust operation of the source when the current flow rate is not within a predetermined range of the desired flow rate.

8. The hydraulic system of claim 1, wherein the controller is further configured to increase the current flow rate of the source when the current flow rate is less than the desired flow rate and less than a predetermined maximum flow rate.

9. A method of operating a hydraulic system, comprising:

pressurizing a fluid;

selectively directing the pressurized fluid to a plurality of fluid actuators;

receiving an input indicative of which of the plurality of fluid actuators are a first type of fluid actuator and which of the plurality of fluid actuators are a second type of fluid actuator;

receiving an input indicative of a desired flow rate for the plurality of fluid actuators;

determining a current flow rate of a source in fluid communication with the plurality of fluid actuators;

demanding the desired flow rate for the first type of fluid actuator and demanding a scaled down desired flow rate for the second type of fluid actuator when a total desired flow rate for the plurality of fluid actuators exceeds the current flow rate of the source; and

demanding a scaled down desired flow rate for all of the plurality of fluid actuators when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source.

10. The method of claim 9, further including:

receiving an input indicative of a desired priority for each of the second type of fluid actuator; and

scaling down the demanded flow rates of the second type of fluid actuators according to the desired priority when the total demanded flow rate for the plurality of fluid actuators exceeds the current flow rate of the source.

11. The method of claim 9, further including determining a priority for each of the plurality of fluid actuators when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source.

12. The method of claim 11, wherein the priority for each of the first type of fluid actuator is the same.

13. The method of claim 11, further including receiving an input indicative of desired priorities for the second type of fluid actuator, the determined priorities being calculated based on the desired priorities.

14. The hydraulic system of claim 13, wherein the determined priorities for the first type of fluid actuator are greater than the determined priorities for the second type of fluid actuators.

15. The method of claim 9, further including:

determining a current flow rate of the source; and

adjusting operation of the source when the current flow rate is not within a predetermined range of the desired flow rate.

16. The method of claim 15, further including increasing the current flow rate of the source when the current flow rate is less than the desired flow rate and less than a predetermined maximum flow rate.

17. A work machine, comprising:

a power source;

at least one work implement;

at least one traction device; and

a hydraulic system configured to actuate at least one of the at least one work implement and the at least one traction device, the hydraulic system including;

a tank configured to hold a supply of fluid;

a source configured to pressurize the fluid;

a plurality of fluid actuators configured to receive the pressurized fluid;

a controller configured to;

receive an input indicative of which of the plurality of fluid actuators are a first type of fluid actuator and which of the plurality of fluid actuators are a second type of fluid actuator;

receive an input indicative of a desired flow rate for the plurality of fluid actuators;

determine a current flow rate of the source,

demand the desired flow rate for the first type of fluid actuator and to demand a scaled down desired flow rate for the second type of fluid actuator when a total desired flow rate for the plurality of fluid actuators exceeds the current flow rate of the source;

demand a scaled down desired flow rate for all of the plurality of fluid actuators when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source; and

adjust operation of the source when the current flow rate is not within a predetermined range of the desired flow rate.

18. The work machine of claim 17, wherein the controller is configured to receive an input indicative of a desired priority for each of the second type of fluid actuator and to scale down the desired flow rate for the second type of fluid actuator according to the desired priority when a total desired flow rate for the plurality of fluid actuators exceeds the current flow rate of the source.

19. The work machine of claim 17, wherein the controller is configured to receive an input indicative of desired priorities for the second type of fluid actuator and to determine a priority for each of the plurality of fluid actuators based on the input when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source.

20. The work machine of claim 18, wherein the determined priority for each of the first type of fluid actuators is the same.

21. The work machine of claim 18, wherein the determined priorities for the first type of fluid actuators are greater than the determined priorities for the second type of fluid actuators.

22. The work machine of claim 17, wherein the controller is further configured to increase the current flow rate of the source when the current flow rate is less than the desired flow rate and less than a predetermined maximum flow rate.

23. A hydraulic system, comprising:

a tank configured to hold a supply of fluid;

a source configured to pressurize the fluid;

a plurality of fluid actuators configured to receive the pressurized fluid; and

a controller configured to;

receive an input indicative of which of the plurality of fluid actuators are a first type of fluid actuator and which of the plurality of fluid actuators are a second type of fluid actuator;

receive an input indicative of a desired priority of the second type of fluid actuator;

receive an input indicative of a desired flow rate for the plurality of fluid actuators;

determine a current flow rate of the source; and

demand the desired flow rate for the first type of fluid actuator and demand a scaled down desired flow rate for the second type of fluid actuator according to the desired priority when a total desired flow rate for the plurality of fluid actuators exceeds the current flow rate of the source.

24. The hydraulic system of claim 23, wherein the controller is configured to determine a priority for each of the plurality of fluid actuators when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source.

25. The hydraulic system of claim 24, wherein the determined priorities for the second type of actuator are calculated based on the desired priorities.

26. A method of operating a hydraulic system, comprising:

pressurizing a fluid;

directing the pressurized fluid to a plurality of fluid actuators;

receiving an input indicative of which of the plurality of fluid actuators are a first type of fluid actuator and which of the plurality of fluid actuators are a second type of fluid actuator;

receiving an input indicative of a desired priority of the second type of fluid actuators;

receiving an input indicative of a desired flow rate for the plurality of fluid actuators;

determining a current flow rate of a source in fluid communication with the plurality of fluid actuators; and

demanding the desired flow rate for the first type of fluid actuator and demanding a scaled down desired flow rate for the second type of fluid actuator according to the desired priority when a total desired flow rate for the plurality of fluid actuators exceeds the current flow rate of the source.

27. The method of claim 26, further including determining a priority for each of the plurality of fluid actuators when the desired flow rate for the first type of fluid actuator exceeds the current flow rate of the source.

28. The method of claim 27, wherein the determined priorities for the second type of fluid actuators are calculated based on the desired priorities.

29. A work machine, comprising:

a power source;

at least one work implement;

at least one traction device; and

a hydraulic system configured to actuate at least one of the at least one work implement and the at least one traction device, the hydraulic system including;

a tank configured to hold a supply of fluid;

a source configured to pressurize the fluid;

a plurality of fluid actuators configured to receive the pressurized fluid;

a controller configured to;

receive an input indicative of which of the plurality of fluid actuators are a first type of fluid actuator and which of the plurality of fluid actuators are a second type of fluid actuator;

receive an input indicative of a desired priority for each of the second type of fluid actuators;

receive an input indicative of a desired flow rate for the plurality of fluid actuators;

determine a current flow rate of the source; and

demand the desired flow rate for the first type of fluid actuator and demand a scaled down desired flow rate for the second type of fluid actuator according to the desired priority when a total desired flow rate for the plurality of fluid actuators exceeds the current flow rate of the source.