Electro-hydraulic system for recovering and reusing potential energy

• US 9,279,236 B2
• Filed: 06/04/2012
• Issued: 03/08/2016
• Est. Priority Date: 06/04/2012
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Zhang, Jiao, Ma, Pengfei, Shang, Tonglin, Wen, Gang Victor, Nelson, Bryan Edward, Chen, Dayao
• Primary Examiner(s): White, Dwayne J
• Assistant Examiner(s): Kraft, Logan
• Application Number:
  US13/487,983
• Publication Number:
  US 20130318955A1
• Time in Patent Office: 1,373 Days
• Field of Search: 604/13, 604/14, 604/16, 604/18
• US Class Current: 1/1
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F15B 1/033 with electrical control means
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20507 Type of prime mover
• 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 2211/20576 with multiple pumps
• 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 2211/30575 in a Wheatstone Bridge arrangement (also half bridges)
• CPC Class Codes: F15B 2211/3058 having additional valves for interconnecting the fluid chambers of a double-acting actuator, e.g. for regeneration mode or for floating mode
• CPC Class Codes: F15B 2211/6306 representing a pressure
• CPC Class Codes: F15B 2211/6336 representing a state of the output member, e.g. position, speed or acceleration
• CPC Class Codes: F15B 2211/6343 representing a temperature
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/7053 Double-acting output members
• CPC Class Codes: F15B 2211/7128 the chambers being connected in parallel
• 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

Abstract

A hydraulic system includes a hydraulic actuator, a pump configured to supply fluid to the hydraulic actuator, and a first accumulator fluidly connected to the hydraulic actuator. The first accumulator is configured to store fluid received from the hydraulic actuator. The hydraulic system also includes a motor drivingly connected to the pump and fluidly connected to the first accumulator. The motor is configured to receive the stored fluid from the first accumulator to drive the pump. The hydraulic system further includes a first discharge valve fluidly connected between the first accumulator and the hydraulic actuator. The first discharge valve is configured to supply the stored fluid from the first accumulator to the hydraulic actuator without the stored fluid from the first accumulator circulating through the pump.

Claims

1. A hydraulic system comprising:

a hydraulic actuator;

a pump configured to supply fluid to the hydraulic actuator;

a first accumulator fluidly connected to the hydraulic actuator and configured to store fluid received from the hydraulic actuator;

a motor drivingly connected to the pump and fluidly connected to the first accumulator, the motor being configured to receive the stored fluid from the first accumulator to drive the pump; and

a first discharge valve fluidly connected between the first accumulator and the hydraulic actuator, the first discharge valve being configured to supply the stored fluid from the first accumulator to the hydraulic actuator without the stored fluid from the first accumulator circulating through the pump when an actuator pressure associated with the fluid supplied to the hydraulic actuator is less than an accumulator pressure associated with the stored fluid in the first accumulator, and a difference between the accumulator and actuator pressures is smaller than a threshold.

2. The hydraulic system of claim 1, further including a controller connected to the first discharge valve, the controller being configured to receive a command to provide fluid to the hydraulic actuator, and in response to the command, open the first discharge valve to direct the stored fluid from the first accumulator to the hydraulic actuator without the stored fluid from the first accumulator circulating through the pump.

3. The hydraulic system of claim 1, further including a second discharge valve fluidly connected between the first accumulator and the motor, the second discharge valve being configured to supply the stored fluid from the first accumulator to the motor.

4. The hydraulic system of claim 3, further including a controller connected to the second discharge valve and the motor, the controller being configured to receive a command to provide fluid to the hydraulic actuator, and in response to the command, open the second discharge valve to direct the stored fluid from the first accumulator to the motor so that the motor drives the pump.

5. The hydraulic system of claim 3, further including:

an accumulator pressure sensor configured to determine the accumulator pressure;

an actuator pressure sensor configured to determine the actuator pressure; and

a controller connected to the first discharge valve, the second discharge valve, the accumulator pressure sensor, and the actuator pressure sensor, the controller being configured to;

open the first discharge valve, and

open the second discharge valve when a condition associated with the accumulator pressure and the actuator pressure is satisfied.

6. The hydraulic system of claim 5, wherein the condition includes the actuator pressure being less than the accumulator pressure and a difference between the accumulator and actuator pressures being greater than the threshold.

7. The hydraulic system of claim 5, wherein the second condition includes the actuator pressure being greater than the accumulator pressure.

8. The hydraulic system of claim 5, wherein the controller is further configured to determine a first difference between the actuator pressure and the accumulator pressure and a second difference between the actuator pressure and a pump pressure associated with the fluid supplied by the pump, and open the first discharge valve when the first difference is less than the second difference.

9. The hydraulic system of claim 5, wherein the controller is further configured to determine a first difference between the actuator pressure and the accumulator pressure and a second difference between the actuator pressure and a pump pressure associated with the fluid supplied by the pump, the condition including the second difference being less than the first difference.

10. The hydraulic system of claim 1, wherein the pump is configured to convert mechanical power from a power source to hydraulic power for pressurizing the fluid supplied to the hydraulic actuator.

11. The hydraulic system of claim 1, wherein:

the hydraulic actuator is a hydraulic cylinder configured to move a boom that is movably connected to a body of a machine, the hydraulic cylinder being one of a plurality of hydraulic cylinders,

the pump is selectively configured to supply fluid to a plurality of first chambers of the plurality of hydraulic actuators in parallel and supply fluid to a plurality of second chambers of the plurality of hydraulic actuators in parallel;

in an overrunning load condition, the first accumulator is configured to store fluid received from the plurality of first chambers; and

in a non-overrunning load condition, the motor is configured to receive the stored fluid from the first accumulator to drive the pump to supply fluid to the plurality of first chambers.

12. The hydraulic system of claim 11, further including a second accumulator fluidly connected between the hydraulic actuator and a tank, the second accumulator being configured to store fluid received from the plurality of second chambers, the motor being configured to receive the stored fluid from the second accumulator to drive the pump.

13. A method of recovering and reusing energy with a hydraulic system, the method comprising:

directing fluid from a hydraulic actuator to a first accumulator to store fluid in the first accumulator;

determining an accumulator pressure associated with the fluid stored in the first accumulator;

determining an actuator pressure associated with fluid supplied to the hydraulic actuator;

directing the stored fluid from the first accumulator to the hydraulic actuator without circulating the stored fluid from the first accumulator through a pump when the actuator pressure is less than the accumulator pressure, and a difference between the accumulator and actuator pressures is smaller than a threshold; and

directing the stored fluid from the first accumulator to a motor driving the pump when a condition associated with the accumulator and actuator pressures is satisfied.

14. The method of claim 13, wherein the difference is a first difference, and the stored fluid is directed from the first accumulator to the hydraulic actuator when

a second difference between the actuator pressure and the accumulator pressure is less than a third difference between the actuator pressure and a pump pressure associated with fluid supplied by the pump.

15. The method of claim 13, wherein the hydraulic actuator is a first hydraulic actuator, the difference is a first difference, and the condition includes at least one of:

a second difference between the actuator pressure and the accumulator pressure being greater than a third difference between the actuator pressure and a pump pressure associated with fluid supplied by the pump; and

the pump delivering pressurized fluid to a second hydraulic actuator separately from the first hydraulic actuator.

16. A hydraulic system comprising:

a hydraulic actuator;

a first pump configured to supply fluid to the hydraulic actuator;

a power source configured to supply power to drive the first pump;

a first accumulator fluidly connected to the hydraulic actuator and configured to store fluid received from the hydraulic actuator;

a device drivingly connected to the first pump, the device being configured to operate in a first mode as a motor to receive the stored fluid from the first accumulator to drive the first pump, and configured to operate in a second mode as a second pump to supply pressurized fluid to the first accumulator; and

a first discharge valve fluidly connected between the first accumulator and the hydraulic actuator, the first discharge valve being configured to supply the stored fluid from the first accumulator to the hydraulic actuator without the stored fluid from the first accumulator circulating through the first pump when an actuator pressure associated with the fluid supplied to the hydraulic actuator is less than an accumulator pressure associated with the stored fluid in the first accumulator, and a difference between the accumulator and actuator pressures is smaller than a threshold.

17. The hydraulic system of claim 16, wherein the threshold is a first threshold and the device is configured to operate in the second mode when at least one of:

a power requirement for the power source is below a threshold,

the power requirement is below a power output of the power source,

the power source is idling, and

the pressure in the first accumulator is below a second threshold.

18. The hydraulic system of claim 16, further including a switching valve fluidly connected between the first accumulator and the device, the switching valve being configured to control the direction of flow between the first accumulator and the device.