System and method for recovering energy and leveling hydraulic system loads

• US 9,803,338 B2
• Filed: 08/10/2012
• Issued: 10/31/2017
• Est. Priority Date: 08/12/2011
• Status: Active Grant

• Current Assignee: Danfoss A/S
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Jagoda, Aaron Hertzel
• Primary Examiner(s): Lazo, Thomas E
• Assistant Examiner(s): Wiblin, Matthew
• Application Number:
  US13/571,517
• Publication Number:
  US 20130061587A1
• Time in Patent Office: 1,908 Days
• CPC Class Codes: E02F 9/123 Drives or control devices specially adapted therefor E02F9/125 and E02F9/128 take precedence
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: F15B 1/024 used as a supplementary power source, e.g. to store energy in idle periods to balance pump load
• CPC Class Codes: F15B 3/00 Intensifiers or fluid-pressure converters, e.g. pressure exchangers; Conveying pressure from one fluid system to another, without contact between the fluids fluid-driven pumps F04B9/08

Abstract

A hydraulic system including an accumulator and a hydraulic transformer is disclosed. 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 an 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.

Claims

1. A hydraulic system comprising:

an accumulator; and

a hydraulic transformer including first and second variable displacement pump/motor units connected to a rotatable shaft, the rotatable shaft adapted for mechanical connection to an external working load, the first variable displacement pump/motor unit including 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 including a first side that fluidly connects to the accumulator and a second side that fluidly connects with the tank, wherein the hydraulic transformer is part of a first load circuit powered at substantially pump outlet pressure by the hydraulic pump;

at least one control valve fluidly connected to the pump via a pump line, the control valve being configured to control fluid flow between the pump and a second load circuit, wherein the first side of the first variable displacement pump/motor of the hydraulic transformer fluidly connects to the pump line at a point between the control valve and an outlet of the pump, wherein fluid flow can be provided via the pump line to both the second load circuit and the first variable displacement pump/motor simultaneously;

wherein the rotatable shaft includes a first portion that connects the first and second variable displacement pump/motor units and further includes a second portion that forms an output shaft that is adapted for mechanical connection to the external working load; and

wherein the hydraulic system is incorporated into an excavator having an upper structure that pivots about a pivot axis relative to an undercarriage, and wherein the output shaft of the rotatable shaft is used to pivot the upper structure about the pivot axis, wherein the hydraulic transformer can transfer energy corresponding to a deceleration of the external load to the accumulator, and wherein the hydraulic transformer can also transfer energy corresponding to a deceleration of the external load to the second load circuit.

2. The hydraulic system of claim 1, wherein each of the first and second variable displacement pump/motor units includes a rotating group mounted on the rotatable shaft and a swash plate.

3. The hydraulic system of claim 1, further comprising a clutch for engaging the rotatable shaft with the external working load and for disengaging the rotatable shaft from the external working load.

4. The hydraulic system of claim 1, wherein the upper structure carries an excavation boom that is raised and lowered by a boom cylinder.

5. The hydraulic system of claim 4, wherein the first side of the first pump/motor unit is placed in fluid communication with an output port of the boom cylinder when the excavation boom is being lowered by the boom cylinder.

6. The hydraulic system of claim 5, further comprising a valve movable between a first position where the first side of the first pump/motor unit is fluidly connected to the pump and a second position where the first side of the first pump/motor unit is fluidly connected to the output port of the boom cylinder.

7. The hydraulic system of claim 4, wherein the hydraulic transformer includes a third pump/motor unit mounted on the rotatable shaft, wherein the third pump/motor unit includes a first side and a second side, wherein the second side of the third pump/motor unit fluidly connects to the tank, and wherein the first side of the third pump/motor unit is placed in fluid communication with an output port of the boom cylinder when the boom is being lowered by the boom cylinder.

8. The hydraulic system of claim 1, further comprising a hydraulic cylinder for raising and lowering a work item, the hydraulic cylinder being fluidly connected to the pump, the first side of the first pump/motor unit being placed in fluid communication with an output port of the hydraulic cylinder when the work item is being lowered by the hydraulic cylinder.

9. The hydraulic system of claim 8, wherein the work item is a boom.

10. The hydraulic system of claim 1, wherein the hydraulic transformer includes a third pump/motor unit mounted on the rotatable shaft, wherein the third pump/motor unit includes a first side and a second side, and wherein the second side of the third pump/motor unit fluidly connects to the tank.

11. The hydraulic system of claim 10, further comprising a hydraulic cylinder for raising and lowering a work item, wherein the first side of the third pump/motor unit is placed in fluid communication with an output port of the hydraulic cylinder when the work item is being lowered by the hydraulic cylinder.

12. The hydraulic system of claim 11, wherein the work item is a boom.

13. The hydraulic system of claim 1, wherein the hydraulic transformer is adapted to provide a motoring function wherein the rotatable shaft drives the external working load.

14. The hydraulic system of claim 1, wherein the hydraulic transformer is adapted to provide a pumping function wherein the rotatable shaft is driven by the external working load.

15. The hydraulic system of claim 1, wherein the rotatable shaft is adapted for mechanical connection to the external working load via a gear reduction.

16. The hydraulic system of claim 1, wherein the hydraulic transformer is adapted to level hydraulic system loads on a prime mover by:

a) transferring hydraulic energy to the accumulator and simultaneously mechanically transferring torque to the external working load when the hydraulic system load on the prime mover is lower than a target and when a command is received to drive the external working load;

b) transferring hydraulic energy to the accumulator and substantially not mechanically transferring torque to or from the external working load when the hydraulic system load on the prime mover is lower than the target and when no command is received to drive or brake the external working load;

c) transferring hydraulic energy to the accumulator and mechanically transferring torque from the external working load when the hydraulic system load on the prime mover is lower than the target and when a command is received to brake the external working load;

d) transferring substantially no hydraulic energy to the accumulator and mechanically transferring torque to the external working load when the hydraulic system load on the prime mover is at the target and when a command is received to drive the external working load;

e) transferring hydraulic energy to the accumulator and mechanically transferring torque from the external working load when the hydraulic system load on the prime mover is at the target and when a command is received to brake the external working load;

f) transferring hydraulic energy from the accumulator and mechanically transferring torque to the external working load when the hydraulic system load on the prime mover is higher than the target and when a command is received to drive the external working load;

g) transferring hydraulic energy from the accumulator and substantially not mechanically transferring torque to or from the external working load when the hydraulic system load on the prime mover is higher than the target and when no command is received to drive or brake the external working load; and

h) transferring hydraulic energy from the accumulator and simultaneously mechanically transferring torque from the external working load when the hydraulic system load on the prime mover is higher than the target and when a command is received to brake the external working load.

17. The hydraulic system of claim 1, further comprising a negative flow control circuit having a negative flow control orifice valve, the negative flow control circuit allows a negative flow control pump control strategy to be used to control a displacement of the pump.

18. A system comprising:

a prime mover;

a hydraulic pump powered by the prime mover;

at least one control valve fluidly connected to the hydraulic pump via a pump line;

first and second load circuits powered at substantially pump outlet pressure by the hydraulic pump, the first load circuit including a hydraulic transformer having an output shaft adapted for mechanical connection to an external working load, the hydraulic transformer being fluidly connected to a hydraulic pressure accumulator, the hydraulic transformer providing a plurality of operations including;

a) a first operation in which the hydraulic transformer receives energy corresponding to a deceleration of the external working load from the output shaft and uses the energy to charge the hydraulic pressure accumulator;

b) a second operation in which the hydraulic transformer uses energy from the hydraulic pressure accumulator to transfer torque to the external working load through the output shaft;

c) a third operation in which the hydraulic transformer directs energy from the hydraulic pressure accumulator back toward the hydraulic pump for use at the second load circuit; and

d) a fourth operation in which the hydraulic transformer directs energy from the hydraulic pump to the output shaft which transfers the energy to the external working load as torque;

wherein the control valve is configured to control fluid flow between the pump and the second load circuit, and wherein the hydraulic transformer fluidly connects to the pump line at a point between the control line and the pump, and wherein fluid flow can be provided via the pump line to both the second load circuit and the hydraulic transformer simultaneously, wherein the hydraulic system is incorporated into an excavator having an upper structure that pivots about a pivot axis relative to an undercarriage, wherein the output shaft of the hydraulic transformer is used to pivot the upper structure about the pivot axis.

19. The system of claim 18, wherein the hydraulic transformer also provides an operation of using energy from the hydraulic pump to charge the hydraulic pressure accumulator.

20. The system of claim 18, wherein the hydraulic transformer also provides an operation of transferring energy corresponding to a deceleration of the external working load from the output shaft back toward the hydraulic pump for use at the second load circuit.

21. The system of claim 18, further comprising an additional operation in which the hydraulic transformer transfers hydraulic energy to the accumulator and simultaneously mechanically transfers torque to the external working load when a command is received to drive the external working load.

22. The system of claim 18, further comprising an additional operation in which the hydraulic transformer transfers hydraulic energy from the accumulator and simultaneously mechanically transfers torque from the external working load when a command is received to brake the external working load.

23. A hydraulic system comprising:

an accumulator; and

a hydraulic transformer including first and second variable displacement pump/motor units connected to a rotatable shaft, the rotatable shaft adapted for mechanical connection to an external working load, the first variable displacement pump/motor unit including 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 including a first side that fluidly connects to the accumulator and a second side that fluidly connects with the tank;

wherein the rotatable shaft includes a first portion that connects the first and second variable displacement pump/motor units and further includes a second portion that forms an output shaft that is adapted for mechanical connection to the external working load; and

wherein the hydraulic system is incorporated into an excavator having an upper structure that pivots about a pivot axis relative to an undercarriage, and wherein the output shaft of the rotatable shaft is used to pivot the upper structure about the pivot axis, wherein the hydraulic transformer is part of a first load circuit powered at substantially pump outlet pressure by the hydraulic pump, wherein the hydraulic system includes a second load circuit powered by the hydraulic pump, wherein the hydraulic transformer can transfer energy corresponding to a deceleration of the external load to the accumulator, and wherein the hydraulic transformer can also transfer energy corresponding to a deceleration of the external load to the second load circuit;

wherein the hydraulic transformer is adapted to level hydraulic system loads on a prime mover by;

a) transferring hydraulic energy to the accumulator and simultaneously mechanically transferring torque to the external working load when the hydraulic system load on the prime mover is lower than a target and when a command is received to drive the external working load;

b) transferring hydraulic energy to the accumulator and substantially not mechanically transferring torque to or from the external working load when the hydraulic system load on the prime mover is lower than the target and when no command is received to drive or brake the external working load;

c) transferring hydraulic energy to the accumulator and mechanically transferring torque from the external working load when the hydraulic system load on the prime mover is lower than the target and when a command is received to brake the external working load;

d) transferring substantially no hydraulic energy to the accumulator and mechanically transferring torque to the external working load when the hydraulic system load on the prime mover is at the target and when a command is received to drive the external working load;

e) transferring hydraulic energy to the accumulator and mechanically transferring torque from the external working load when the hydraulic system load on the prime mover is at the target and when a command is received to brake the external working load;

f) transferring hydraulic energy from the accumulator and mechanically transferring torque to the external working load when the hydraulic system load on the prime mover is higher than the target and when a command is received to drive the external working load;

g) transferring hydraulic energy from the accumulator and substantially not mechanically transferring torque to or from the external working load when the hydraulic system load on the prime mover is higher than the target and when no command is received to drive or brake the external working load; and

h) transferring hydraulic energy from the accumulator and simultaneously mechanically transferring torque from the external working load when the hydraulic system load on the prime mover is higher than the target and when a command is received to brake the external working load.