Energy regeneration system for work machines

• US 20060090461A1
• Filed: 12/12/2005
• Published: 05/04/2006
• Est. Priority Date: 11/14/2003
• Status: Active Grant

• Current Assignee: Caterpillar Sarl (Caterpillar Incorporated)
• Original Assignee: Caterpillar Incorporated, Shin Caterpillar Mitsubishi Ltd. (Caterpillar Incorporated)
• Inventors: Yoshino, Kazunori
• Granted Patent: US 7,401,464 B2
• Time in Patent Office: Days
• US Class Current: 60/468
• CPC Class Codes: E02F 9/2207 for reducing or compensating oscillations
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F15B 11/006 Hydraulic "Wheatstone bridge" circuits, i.e. with four nodes, P-A-T-B, and on-off or proportional valves in each link
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20515 Electric motor
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/26 Power control functions
• CPC Class Codes: F15B 2211/30575 in a Wheatstone Bridge arrangement (also half bridges)
• CPC Class Codes: F15B 2211/31576 having a single pressure source and a single output member
• CPC Class Codes: F15B 2211/327 electrically or electronically
• CPC Class Codes: F15B 2211/45 Control of bleed-off flow, e.g. control of bypass flow to the return line
• CPC Class Codes: F15B 2211/63 Electronic controllers
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/6651 Control of the prime mover, e.g. control of the output torque or rotational speed
• CPC Class Codes: F15B 2211/7053 Double-acting output members
• CPC Class Codes: F15B 2211/88 Control measures for saving energy

Abstract

First and second displacement variable regenerating hydraulic motors are provided in third and fourth flow rate control lines which function as discharge flow paths for oil discharged, respectively, from first and second oil supply and discharge ports of a hydraulic motor, where controlling the displacement of the regenerating hydraulic motors allows the flow rate of discharge oil as well as the pressure of the third and fourth flow rate control lines to be controlled. First and second generators which generate electric power due to the rotation of the first and second regenerating hydraulic motors are further provided.

Claims

1. An energy regeneration system for working machinery comprising:

a fluid pressure actuator adapted to operate by supplying/discharging fluid;

a displacement variable regenerating fluid pressure motor in a discharge flow path for fluid discharged from the fluid pressure actuator such that controlling the displacement of the regenerating fluid pressure motor allows the flow rate of discharge fluid from the fluid pressure actuator as well as the pressure of the discharge flow path to be controlled; and

an energy regeneration device for regenerating the energy of discharge fluid as electrical energy, at least in part by rotating the regenerating fluid pressure motor.

2. The energy regeneration system for working machinery according to claim 1, wherein the displacement of the regenerating fluid pressure motor is controlled so that the flow rate of discharge fluid from the fluid pressure actuator varies from zero to a predetermined maximum value.

3. The energy regeneration system for working machinery according to claim 2 and further comprising:

a relief flow path connected to a supply flow path for fluid to be supplied to the fluid pressure actuator between an intermediate part of the supply flow path and a fluid tank;

a displacement variable regenerating fluid pressure motor in the relief flow path such that controlling the displacement of the regenerating fluid pressure motor allows the pressure of the supply flow path to the fluid pressure actuator to be controlled; and

an energy regeneration device for regenerating the rotational energy of fluid in the relief flow path as electrical energy, at least in part by rotating the regenerating fluid pressure motor.

4. The energy regeneration system for working machinery according to claim 3, wherein the pressure control of the discharge flow path and/or the supply flow path performed by the regenerating fluid pressure motor is a relief control in which fluid in the discharge flow path and/or the supply flow path is to be relieved when the pressure of the discharge flow path and/or the supply flow path reaches a predetermined relief pressure.

5. The energy regeneration system for working machinery according to claim 1, wherein the flow rate of supply fluid to the fluid pressure actuator is controlled by a supplying flow rate control valve.

6. The energy regeneration system for working machinery according to claim 2, wherein:

the fluid pressure actuator is a bi-directional rotary fluid pressure motor having two fluid supply and discharge ports; and

the regenerating fluid pressure motor is a displacement variable fluid pressure motor provided in a discharge flow path for fluid discharged from each of the fluid supply and discharge ports.

7. The energy regeneration system for working machinery according to claim 6 wherein:

a relief flow path is connected to a supply flow path for fluid to be supplied to one of the fluid supply and discharge ports of the bi-directional rotary fluid pressure motor between the intermediate part of the supply flow path and the fluid tank; and

the relief flow path is adapted to function as a discharge flow path for fluid discharged from the one of the fluid supply and discharge ports.

8. The energy regeneration system for working machinery according to claim 7, wherein the working machinery is equipped with a controller operable to receive an operation signal from a fluid pressure actuator operation tool, a detection signal from a pressure detection means for detecting the pressure of the discharge flow path and/or the supply flow path of the fluid pressure actuator, said controller further being operable to output a control command to a displacement control means for the regenerating fluid pressure motor based on the operation and detection signals.

9. The energy regeneration system for working machinery according to claim 1, wherein electrical energy obtained by the energy regeneration device is used as a power supply source for a motor for driving a pump adapted to supply pressurized fluid to the fluid pressure motor.

10. The energy regeneration system for working machinery according to claim 9, wherein the motor is used as an auxiliary power source for the pump.

11. The energy regeneration system for working machinery according to claim 6, wherein the energy regeneration device comprises:

a power generating means which generates electric power due to the rotational driving of the regenerating fluid pressure motor;

a power storage means for storing electric power generated by the power generating means; and

an inverter for converting electric power stored in the power storage means into AC power.

12. A work machine comprising:

a hydraulic actuator having first and second supply/discharge ports;

a flow rate control circuit including first and second flow rate control lines connecting with said first and second supply/discharge ports, respectively;

at least one displacement variable hydraulic motor within said flow rate control circuit;

at least one pressure sensing means disposed within said flow rate control circuit between said at least one displacement variable hydraulic motor and said hydraulic actuator; and

an energy regeneration device coupled with said displacement variable hydraulic motor for regenerating at least a portion of an energy of discharge fluid of said hydraulic actuator as electrical energy.

13. The work machine of claim 12 wherein said first and second flow rate control lines each comprise a supply/discharge line connected with said first and second supply/discharge ports of said hydraulic actuator, respectively;

said at least one displacement variable hydraulic motor comprises a first and a second displacement variable hydraulic motor disposed one within each of said first and second supply/discharge lines.

14. The work machine of claim 13 wherein said hydraulic actuator is a bi-directional rotatable hydraulic motor.

15. The work machine of claim 14 wherein said at least one pressure sensing means comprises a first pressure sensor disposed within said first supply/discharge line and a second pressure sensor disposed within said second supply/discharge line.

16. The work machine of claim 15 further comprising:

a displacement control means coupled with each of said first and second displacement variable hydraulic motors;

an electronic controller operably coupled with each of said first and second pressure sensors and with each said displacement control means, said electronic controller configured to receive a pressure signal from one of said pressure sensors and responsively output a displacement control signal to the corresponding displacement variable hydraulic motor.

17. A method of operating a hydraulic system comprising the steps of:

supplying hydraulic fluid to a hydraulic actuator; and

controlling at least one of flow rate and hydraulic pressure in a discharge flow path of the hydraulic actuator at least in part by adjusting a displacement of a hydraulic energy regeneration motor in a hydraulic control circuit of the system.

18. The method of claim 17 wherein the controlling step comprises adjusting the displacement of the motor responsively to a determined fluid pressure in the hydraulic control circuit in at least one of an upstream and a downstream position relative to the hydraulic actuator.

19. The method of claim 18 wherein the hydraulic actuator is a bi-directional hydraulic motor, the controlling step further comprising controlling rotational motion of the hydraulic actuator.

20. The method of claim 19 wherein the controlling step comprises the step of relieving hydraulic pressure in a discharge flow path of the hydraulic actuator when determined fluid pressure therein exceeds a predetermined maximum pressure.