Control system for hydraulic system and method for recovering energy and leveling hydraulic system loads

• US 9,765,501 B2
• Filed: 12/19/2013
• Issued: 09/19/2017
• Est. Priority Date: 12/19/2012
• Status: Active Grant

• Current Assignee: Danfoss Power Solutions II Technology A/S
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Wang, Meng (Rachel), Jagoda, Aaron Hertzel, Larish, Chad Anthony, Piyabongkarn, Damrongrit, Danzl, Per William, Mahulkar, Vishal Vijay
• Primary Examiner(s): Lazo, Thomas E
• Assistant Examiner(s): COLLINS, DANIEL S.
• Application Number:
  US14/134,545
• Publication Number:
  US 20140166114A1
• Time in Patent Office: 1,370 Days
• Field of Search: 60458-460
• CPC Class Codes: E02F 9/2075 of the hybrid type for vehicles in general B60W20/00
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2232 using one or more variable displacement pumps
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20569 capable of working as pump and motor
• CPC Class Codes: F15B 2211/212 the pressure sources being accumulators
• CPC Class Codes: F15B 2211/214 the pressure sources being hydrotransformers
• CPC Class Codes: F15B 2211/2654 one or more pressure sources having priority
• CPC Class Codes: F15B 2211/3059 having multiple valves for multiple output members
• CPC Class Codes: F15B 2211/6306 representing a pressure
• CPC Class Codes: F15B 2211/633 representing a state of the prime mover, e.g. torque or rotational speed
• CPC Class Codes: F15B 2211/6336 representing a state of the output member, e.g. position, speed or acceleration
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/6652 Control of the pressure source, e.g. control of the swash plate angle
• CPC Class Codes: F15B 2211/7058 Rotary output members
• CPC Class Codes: F15B 2211/7135 Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
• CPC Class Codes: F15B 2211/761 Control of a negative load, i.e. of a load generating hydraulic energy
• CPC Class Codes: F15B 2211/88 Control measures for saving energy
• CPC Class Codes: Y10T 137/0379 : By fluid pressure

Abstract

A control system for a hydraulic system including an accumulator and a hydraulic transformer coordinates flow sharing within the hydraulic system. The hydraulic transformer includes first and second variable displacement pump/motor units mounted on a rotatable shaft. The rotatable shaft has an end adapted for connection to a first external load. The first variable displacement pump/motor unit includes a first side that fluidly connects to a pump and a second side that fluidly connects to a tank. The second variable displacement pump/motor unit includes a first side that fluidly connects to the accumulator and a second side that fluidly connects with the tank. A second external load may be hydraulically connected to the hydraulic system. Energy may be transferred to/from the pump, the accumulator, the first external load, and/or the second external load, as directed by the control system.

Claims

1. A method of delivering power in a hybrid work machine, the method comprising:

determining engine power of an engine;

determining accumulator pressure of an accumulator;

determining a first target power flow to/from a first work machine component;

determining a second target power flow to/from a second work machine component;

setting an operating mode to a first mode if the second target power flow is substantially zero;

setting the operating mode to a second mode if the first target power flow is substantially zero;

setting the operating mode to a third mode if the first and second target power flows are both substantially non-zero;

flow sharing a first power flow from a main pump mechanically connected to the engine and from a transformer fluidly connected to the accumulator when the accumulator pressure is below a first threshold value and the operating mode is set to the first mode and the accumulator is available for discharge;

supplying the first power flow from the transformer when the accumulator pressure is above the first threshold value and the operating mode is set to the first mode;

supplying the first power flow from the main pump when the operating mode is set to the first mode and the accumulator is unavailable for discharge;

flow sharing a second power flow from the main pump and from the transformer when the accumulator pressure is below a second threshold value and the operating mode is set to the second mode and the accumulator is available for discharge;

supplying the second power flow from the transformer when the accumulator pressure is above the second threshold value and the operating mode is set to the second mode; and

supplying the second power flow from the main pump when the operating mode is set to the second mode and the accumulator is unavailable for discharge.

2. The method of claim 1, further comprising flow sharing the first power flow from the main pump and from the transformer when the accumulator pressure is below a third threshold value and the operating mode is set to the third mode thereby powering the first work machine component.

3. The method of claim 2, wherein the second work machine component is powered by the main pump that is mechanically connected to the engine.

4. The method of claim 1, wherein the hybrid work machine is an excavator, the first work machine component is a swing actuator, and the second work machine component is a boom actuator.

5. The method of claim 1, further comprising supplying the first power flow to the transformer from the first work machine component and thereby charging the accumulator when the accumulator is available for charging and the first work machine component is receiving mechanical power.

6. The method of claim 5, wherein the first power flow is directly supplied to the transformer by a shaft.

7. The method of claim 1, further comprising supplying the second power flow to the transformer from the second work machine component and thereby charging the accumulator when the accumulator is available for charging and the second work machine component is receiving mechanical power.

8. The method of claim 7, wherein the second power flow is fluidly supplied to the transformer by a fluid line.

9. The method of claim 1, further comprising supplying a third power flow to/from the first work machine component from/to the second work machine component via the transformer when the operating mode is set to the third mode.

10. The method of claim 1, further comprising flow sharing a third power flow to the first work machine component from the second work machine component and the accumulator when the operating mode is set to the third mode.

11. The method of claim 1, further comprising flow sharing a third power flow to the first work machine component from the engine and the accumulator when the operating mode is set to the third mode.

12. The method of claim 1, further comprising flow sharing a third power flow to the second work machine component from the main pump and the accumulator when the operating mode is set to the third mode.

13. The method of claim 1, further comprising flow sharing a third power flow to the accumulator from the second work machine component and the main pump thereby charging the accumulator when the accumulator is available for charging and the second work machine component is receiving mechanical power.

14. A method of delivering power in a hybrid work machine, the method comprising:

determining engine power of an engine;

determining accumulator pressure of an accumulator;

determining a target power flow to/from a work machine component;

flow sharing a power flow to the work machine component from a main pump mechanically connected to the engine and from a transformer fluidly connected to the accumulator when the accumulator pressure is below a threshold value, the accumulator is available for discharge, and the target power flow is to the work machine component;

supplying the power flow to the work machine component from the transformer when the accumulator pressure is above the threshold value and the target power flow is to the work machine component; and

supplying the power flow to the work machine component from the main pump when the accumulator is unavailable for discharge and the target power flow is to the work machine component.

15. The method of claim 14, wherein the hybrid work machine is an excavator and wherein the work machine component is a swing actuator or a boom actuator.

16. The method of claim 14, wherein the transformer and the work machine component are mechanically connected by a power transfer shaft.

17. The method of claim 14, further comprising supplying the power flow to the transformer from the work machine component and thereby charging the accumulator when the accumulator is available for charging and the target power flow is from the work machine component.

18. The method of claim 17, wherein the power flow is directly supplied to the transformer from the work machine component by a power transfer shaft when the accumulator is available for charging and the target power flow is from the work machine component.

19. The method of claim 17, wherein the power flow is fluidly supplied to the transformer by a fluid line when the accumulator is available for charging and the target power flow is from the work machine component.

20. The method of claim 14, wherein the threshold value is a variable threshold value.

21. The method of claim 20, wherein the threshold value is determined prior to determining if the accumulator is available for discharge.

22. A method of delivering power in a hybrid excavator, the method comprising:

determining engine power of an engine;

determining accumulator pressure of an accumulator;

determining a swing target power flow to/from a swing actuator;

determining a boom target power flow to/from a boom actuator;

determining a transformer flow capacity of a transformer;

flow sharing a first power flow from the boom actuator and from the accumulator to the swing actuator when the boom actuator is over-running and moving down, the accumulator is available for discharge, and the boom target power flow is above a threshold value from the boom actuator; and

flow sharing a second power flow from the swing actuator and from the accumulator to the boom actuator when the swing actuator is decelerating, the accumulator is available for discharge, and the swing target power flow is above a threshold value from the swing actuator.

23. A method of delivering power in a hybrid work machine, the method comprising:

determining accumulator pressure of an accumulator;

determining a target power flow to/from a work machine component;

flow sharing a power flow to the work machine component from a first power source and from a second power source when the second power source has available energy below a threshold value, and the target power flow is to the work machine component;

supplying the power flow to the work machine component from the second power source when the second power source has the available energy above the threshold value and the target power flow is to the work machine component; and

supplying the power flow to the work machine component from the first power source when the second power source has no available energy and the target power flow is to the work machine component.

24. The method of claim 23, further comprising determining engine power of an engine, wherein the first power source is a main pump mechanically connected to the engine and wherein the second power source is a transformer fluidly connected to the accumulator at least when the accumulator has the available energy.

25. The method of claim 23, further comprising determining engine power of an engine, wherein the work machine component is a first work machine component, wherein the first power source is a main pump mechanically connected to the engine, and wherein the second power source is a transformer fluidly connected to a second work machine component at least when the second work machine component has the available energy.

26. The method of claim 23, further comprising determining a target power flow to/from a second work machine component;

wherein the work machine component is a first work machine component, wherein the first power source is the second work machine component, and wherein the second power source is a transformer fluidly connected to the accumulator at least when the accumulator has the available energy.

27. A method of delivering power in a hybrid work machine, the method comprising:

determining engine power of an engine;

determining accumulator pressure of an accumulator;

determining a target power flow to/from a work machine component;

flow sharing a power flow to the accumulator from a main pump mechanically connected to the engine and from a transformer mechanically connected to the work machine component when the accumulator pressure is below a threshold value, when the accumulator is available for charging, and when the target power flow is from the work machine component;

supplying the power flow to the accumulator from the transformer mechanically connected to the work machine component when the accumulator pressure is above the threshold value, when the accumulator is available for charging, and when the target power flow is from the work machine component; and

supplying the power flow to the accumulator from the transformer fluidly connected to the main pump when the work machine component has no available energy.