SYSTEM AND METHOD FOR RECOVERING ENERGY AND LEVELING HYDRAULIC SYSTEM LOADS

• US 20130061587A1
• Filed: 08/10/2012
• Published: 03/14/2013
• Est. Priority Date: 08/12/2011
• Status: Active Grant

• Current Assignee: Danfoss A/S
• Original Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Inventors: Jagoda, Aaron Hertzel
• Granted Patent: US 9,803,338 B2
• Time in Patent Office: Days
• US Class Current: 60/414
• 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 connection to an external 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.

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 load and for disengaging the rotatable shaft from the external load.

4. The hydraulic system of claim 1, 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 rotatable shaft is used to pivot the upper structure about the pivot axis.

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

6. The hydraulic system of claim 5, 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.

7. The hydraulic system of claim 6, 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.

8. The hydraulic system of claim 5, 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.

9. 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.

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

11. 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.

12. The hydraulic system of claim 11, further comprising a hydraulic cylinder for raising an 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.

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

14. The hydraulic system of claim 1, wherein the hydraulic transformer is part of a first load circuit powered 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.

15. A system comprising:

a prime mover;

a hydraulic pump powered by the prime mover;

first and second load circuits powered by the hydraulic pump, the first load circuit including a hydraulic transformer having an output shaft adapted for connection to an external 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 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 accumulator is used to transfer torque to the external load through the output shaft;

c) a third operation in which the hydraulic transformer directs energy from the 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 load as torque.

16. The system of claim 15, wherein the hydraulic transformer also provides an operation of using energy from the pump to charge the accumulator.

17. The system of claim 15, wherein the hydraulic transformer also provides the operation of transferring energy corresponding to a deceleration of the external load from the output shaft back toward the hydraulic pump for use at the second load circuit.