System and method for hydraulic energy recovery

Patent metadata

Field	Value
Publication number	US-9932993-B2
Application number	US-201514936137-A
Country	US
Kind code	B2
Filing date	Nov 9, 2015
Priority date	Nov 9, 2015
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

A hydraulic control system for a machine is provided. The hydraulic control system includes a fluid reservoir, a pump motor and an accumulator. The pump motor is configured to provide pressurized fluid and to receive fluid to provide a power output. The hydraulic control system further includes a hydraulic actuator having a first and a second chamber, a first valve, a regenerative valve, and a controller. The controller is in communication with the first valve and the regenerative valve to selectively actuate the regenerative valve to allow flow of a first portion of the fluid from the first chamber to the second chamber. The controller is further configured to selectively actuate the first valve to allow flow of a second portion of the fluid from the first chamber through the pump motor to provide the power output to a shaft of a power source.

First claim

What is claimed is:

1. A hydraulic control system for a machine, the hydraulic control system comprising:
a fluid reservoir;
a pump motor coupled to a power source via a shaft, the pump motor fluidly coupled to the fluid reservoir, the pump motor configured to provide pressurized fluid and to receive fluid to provide a power output to the shaft;
a hydraulic actuator having a first chamber and a second chamber, each of the chambers being fluidly coupled to the pump motor;
an accumulator fluidly coupled to one of the chambers of the hydraulic actuator to receive fluid from the hydraulic actuator for storage and to the pump motor, wherein in a first mode the accumulator is configured to provide stored fluid to the pump motor and in a second mode the pump motor is configured to provide pressurized fluid to the accumulator;
a first valve fluidly coupled between the first chamber of the hydraulic actuator and the pump motor, the first valve movable between an open position and a closed position;
a regenerative valve fluidly coupled between the first chamber of the hydraulic actuator and the second chamber of the hydraulic actuator, the regenerative valve movable between an open position and a closed position; and
a controller in communication with the first valve and the regenerative valve, the controller configured to:
selectively actuate the regenerative valve to allow flow of a first portion of the fluid from the first chamber of the hydraulic actuator to the second chamber of the hydraulic actuator, and
selectively actuate the first valve to allow flow of a second portion of the fluid from the first chamber of the hydraulic actuator through the pump motor to provide the power output to the shaft and reduce a power needed from the power source.

2. The hydraulic control system of claim 1 comprising:
a shaft speed sensor and a shaft torque sensor coupled to the shaft and in communication with the controller to indicate the shaft speed and the shaft torque of the shaft; and
an accumulator charge valve fluidly coupled between the first chamber of the hydraulic actuator and the accumulator, the accumulator charge valve movable between an open position and a closed position;
wherein the controller is configured to:
calculate the power demand of the power source based on the shaft speed and shaft torque, and when the power demand is greater than a power threshold, the controller is configured to,
move the first valve from the open position to the closed position;
move the accumulator charge valve to the open position to allow fluid to be communicated from the first chamber of the actuator to the accumulator for storage.

3. The hydraulic control system of claim 2 , further comprising:
a second valve fluidly coupled between the hydraulic actuator and the fluid reservoir, the second valve movable between an open position and a closed position,
wherein the controller is configured to:
receive an input signal indicative of a pressure at the accumulator;
receive an input signal indicative of a pressure at the first chamber of the hydraulic actuator;
receive an input signal indicative of an operator input to lower an implement system connected to the hydraulic actuators at a predetermined rate; and
move the second valve to the open position to allow at least a portion of the fluid to be communicated from the first chamber of the actuator to the fluid reservoir when the accumulator pressure is greater than a threshold pressure and the actuator pressure is greater than a threshold pressure.

4. The hydraulic control system of claim 3 , further comprising an accumulator discharge valve fluidly coupled between the accumulator and the pump motor, the accumulator discharge valve movable between an open position and a closed position, wherein the controller is configured to:
change a displacement of the pump motor to increase pressure output, when the pressure at the hydraulic actuator is beyond greater than a predetermined threshold, and the power demand of the power source is greater than a second power threshold;
move the regenerative valve and the accumulator charge valve to the open position; and
move the second valve from the open position to the closed position and the accumulator discharge valve to the closed position.

5. The hydraulic control system of claim 2 , further comprising an accumulator discharge valve fluidly coupled between the accumulator and the pump motor, the accumulator discharge valve movable between an open position and a closed position, wherein the controller is configured to:
move the accumulator charge valve to the closed position when the respective pressures of the accumulator and the hydraulic actuator are greater than respective predetermined thresholds; and
move the accumulator discharge valve to the open position to allow fluid to be communicated from the accumulator to an auxiliary hydraulic circuit that is in fluid communication with the accumulator.

6. The hydraulic control system of claim 2 , further comprising an accumulator discharge valve fluidly coupled between the accumulator and the pump motor, the accumulator discharge valve movable between an open position and a closed position, wherein the controller is configured to:
move the accumulator discharge valve to the open position; and
move the accumulator charge valve, the second valve and the first valve to the closed position to supply fluid from the accumulator through the pump motor to provide the power output to the shaft.

7. The hydraulic control system of claim 2 , further comprising an accumulator discharge valve fluidly coupled between the accumulator and the first chamber of the actuator, the accumulator discharge valve movable between an open position and a closed position, wherein the controller is configured to:
move the accumulator discharge valve to the open position to supply fluid from the accumulator to the first chamber of the hydraulic actuator when the operators input is detected to raise the implement system and the pressure in the accumulator is greater than a predetermined threshold.

8. A method of operating a hydraulic control system having an implement system movable through a range of motion, the method comprising:
detecting movement of an implement system in a descending direction;
actuating a regenerative valve to allow flow of a first portion of a fluid from a first chamber of a hydraulic actuator to a second chamber of the hydraulic actuator;
actuating a first valve to allow flow of a second portion of the fluid from the first chamber of the hydraulic actuator through a pump motor to provide a power output to a shaft coupled between the pump motor and a power source.

9. The method of claim 8 further comprising:
determining a power source power output based on a shaft speed and a shaft torque of a shaft coupling the power source and the pump motor; when the power source power output is greater than a power threshold, the method further comprises:
moving the first valve from an open position to a closed position;
moving an accumulator charge valve to an open position to allow fluid to be communicated from the first chamber of the actuator to an accumulator for charging the accumulator.

10. The method of claim 9 further comprising:
determining a pressure of the accumulator;
determining a pressure of the first chamber of the hydraulic actuator;
determining an operator input in a position to lower the implement system connected to the hydraulic actuators at a predetermined rate; and
moving a second valve to an open position to allow fluid to be communicated from the first chamber of the actuator to the fluid reservoir while keeping each of the regenerative valve

Assignees

• Caterpillar Inc

Inventors

• Zhang Jiao
• Chen Dayao
• Peterson Jeremy T
• Knussman Michael L

Classifications

• F15B2211/3058

  having additional valves for interconnecting the fluid chambers of a double-acting actuator, e.g. for regeneration mode or for floating mode · CPC title

• F15B2211/3133

  Regenerative position connecting the working ports or connecting the working ports to the pump, e.g. for high-speed approach stroke · CPC title

• F15B2211/88

  Control measures for saving energy · CPC title

• F15B1/024

  used as a supplementary power source, e.g. to store energy in idle periods to balance pump load · CPC title

• F15B11/024 Primary

  by means of differential connection of the servomotor lines, e.g. regenerative circuits · CPC title