Control system for recovering swing motor kinetic energy

• US 7,908,852 B2
• Filed: 02/28/2008
• Issued: 03/22/2011
• Est. Priority Date: 02/28/2008
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated, Shin Caterpillar Mitsubishi Ltd. (Caterpillar Incorporated)
• Original Assignee: Caterpillar Incorporated, Caterpillar Sarl (Caterpillar Incorporated)
• Inventors: Ma, Pengfei, Schwab, Michael R., Zhang, Jiao, Shang, Tonglin, Patel, Kalpesh N.
• Primary Examiner(s): LESLIE, MICHAEL S
• Application Number:
  US12/039,426
• Publication Number:
  US 20090217653A1
• Time in Patent Office: 1,118 Days
• Field of Search: 604/13, 604/14, 604/64, 604/68, 604/93, 914/54, 914/57
• US Class Current: 60/414
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2228 including an electronic controller
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• 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 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/212 the pressure sources being accumulators
• CPC Class Codes: F15B 2211/3144 the positions being continuously variable, e.g. as realised by proportional valves
• CPC Class Codes: F15B 2211/31529 having a single pressure source and a single output member
• CPC Class Codes: F15B 2211/31558 having a single output member
• CPC Class Codes: F15B 2211/50527 using cross-pressure relief valves
• CPC Class Codes: F15B 2211/6306 representing a pressure
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/7058 Rotary output members
• CPC Class Codes: F15B 2211/88 Control measures for saving energy

Abstract

This disclosure relates to a hydraulic system and method that converts the kinetic energy generated by the operation of a swing motor into hydraulic potential energy and reuses the hydraulic potential energy for swing motor acceleration. An accumulator can be provided for storing exit oil from the swing motor that is pressurized by the inertia torque applied on the moving motor via movement of an upper structure of a machine. The pressurized oil in the accumulator can be reused to accelerate the swing motor by supplying pressurized oil to the swing motor.

Claims

1. A control circuit comprising:

a swing motor, the swing motor having a first port and a second port, the swing motor moving in a first direction when a flow of hydraulic fluid flows into the swing motor through the first port, the swing motor moving in a second direction when a flow of hydraulic fluid flows into the swing motor through the second port, the second direction being opposite to the first direction;

first and second motor conduits, the first motor conduit connected to the first port of the motor, the second motor conduit connected to the second port of the motor;

a pump adapted to selectively provide a flow of hydraulic fluid to the swing motor through the first and second motor conduits;

an accumulator system including a pressure-controlled selection valve and an accumulator, the selection valve hydraulically connected to the first and second motor conduits and to the accumulator and being movable between a first open position, wherein a flow path between the first port of the swing motor and the accumulator is defined, and a second open position, wherein a flow path between the second port of the swing motor and the accumulator is defined, the selection valve being disposed in the first open position when the pressure in the first motor conduit is greater than the pressure in the second motor conduit, and the selection valve being disposed in the second open position when the pressure in the second motor conduit is greater than the pressure in the first motor conduit; and

an accumulator charge valve in series between the selection valve, the accumulator charge valve being movable between a first open position, wherein a one-way flow path towards the accumulator is defined, and a second open position, wherein a one-way flow path towards the selection valve is defined.

2. The control circuit according to claim 1, further comprising:

a control valve, the control valve hydraulically connected to the pump and to the first and second motor conduits, the control valve movable between a first open position, wherein a flow path between the pump and the first port of the swing motor is defined, a second open position, wherein a flow path between the pump and the second port of the swing motor is defined, and a closed position, wherein the pump and the swing motor are hydraulically blocked from each other.

3. The control circuit according to claim 2, wherein the control valve includes an inlet hydraulically connected to the pump, a first outlet hydraulically connected to the first motor conduit, a second outlet hydraulically connected to the second motor conduit, a first variable restrictor disposed between the inlet and the first outlet and a second variable restrictor disposed between the inlet and the second outlet.

4. The control circuit according to claim 3, further comprising:

a tank;

wherein the control valve includes a third variable restrictor hydraulically connected to the first motor conduit and to the tank, a one-way check valve connected in parallel relationship with the third variable restrictor and connected to the first motor conduit and the tank to define a one-way fluid flow path from the tank through the check valve to the swing motor via the first motor conduit, and a fourth variable restrictor hydraulically connected to the second motor conduit and to the tank, a one-way check valve connected in parallel relationship with the fourth variable restrictor and connected to the second motor conduit and the tank to define a one-way fluid flow path from the tank through the check valve to the swing motor via the second motor conduit.

5. The control circuit according to claim 1, wherein the accumulator charge valve includes a solenoid and a spring, the solenoid and the spring of the accumulator charge valve adapted to move the accumulator charge valve between the first open position and the second open position, the control circuit further comprising:

an operator input mechanism adapted to selectively indicate the direction and degree of swing motor operation, wherein the direction includes the first and second directions of the swing motor, and wherein the degree comprises a range between a lower limit and an upper limit of swing motor operation; and

a controller electrically connected to the operator input mechanism and the solenoid of the accumulator charge valve, the controller adapted to receive a variable signal from the operator input mechanism, the signal variable to indicate the direction and degree of swing motor operation selected by the operator, and to operate the solenoid of the accumulator charge valve to place the accumulator charge valve in one of the first open position and the second open position based on the signal from the operator input mechanism.

6. The control circuit according to claim 5, wherein the controller places the accumulator charge valve in the second open position when the operator input mechanism indicates a clockwise direction with a predetermined percentage or more of the range of motor operation or a counterclockwise direction with a predetermined percentage or more of the range of motor operation.

7. The control circuit according to claim 1, further comprising:

a pressure transducer operably arranged with the accumulator; and

a modulation valve hydraulically connected to the selection valve and the accumulator, the modulation valve being in series between the selection valve and the accumulator, the modulation valve being variably movable over a range of travel between a fully open position, wherein a flow path from the selection valve to the accumulator is defined, and a fully closed position, wherein the selection valve and the accumulator are hydraulically blocked from each other;

wherein the position of the modulation valve is based upon the pressure detected by the pressure transducer.

8. The control circuit according to claim 7, wherein the modulation valve includes a solenoid and a spring adapted to move the modulation valve over the range of travel between the fully open position and the fully closed position, the control circuit further comprising:

a controller electrically connected to the pressure transducer and the solenoid of the modulation valve, and adapted to receive a variable signal from the pressure transducer to indicate the pressure in the accumulator sensed by the pressure transducer, and to operate the solenoid of the modulation valve, the controller positioning the modulation valve based on the pressure sensed by the pressure transducer.

9. The control circuit according to claim 1, further comprising:

a pressure transducer, the pressure transducer operably arranged with the accumulator; and

a modulation valve hydraulically connected to the selection valve and the accumulator and being in series between the selection valve and the accumulator, and being variably movable over a range of travel between a fully open position, wherein a flow path from the selection valve to the accumulator is defined, and a fully closed position, wherein the selection valve and the accumulator are hydraulically blocked from each other;

wherein the position of the modulation valve is based upon the pressure detected by the pressure transducer.

10. The control circuit according to claim 9, wherein the modulation valve includes a solenoid and a spring, the solenoid and the spring of the modulation valve adapted to move the modulation valve over the range of travel between the fully open position and the fully closed position, and wherein the accumulator charge valve includes a solenoid and a spring, the solenoid and the spring of the accumulator charge valve adapted to move the accumulator charge valve between the first open position and the second open position, the control circuit further comprising:

an operator input mechanism adapted to selectively indicate the direction and degree of swing motor operation, wherein the direction includes the first and second directions of the swing motor, and wherein the degree comprises a range between a lower limit and an upper limit of swing motor operation; and

a controller electrically connected to the operator input mechanism, the pressure transducer, the solenoid of the modulation valve, and the solenoid of the accumulator charge valve, the controller adapted to receive a variable signal from the pressure transducer to indicate the pressure sensed by the pressure transducer, and to operate the solenoid of the modulation valve to place the modulation valve in a position based on the pressure sensed by the pressure transducer, the controller being further adapted to receive a variable signal from the operator input mechanism, the variable signal to indicate the direction and degree of swing motor operation selected by the operator, and to operate the solenoid of the accumulator charge valve to place the accumulator charge valve in one of the first open position and the second open position based on the signal from the operator input mechanism.

11. A method for controlling a swing motor comprising:

directing a flow of hydraulic fluid through a first motor conduit into a first port of the swing motor and out of a second port of the swing motor into a second motor conduit to move the swing motor in a first direction;

decelerating the flow of hydraulic fluid through the swing motor into the first port and out the second port;

providing a flow path from the second port of the swing motor to an accumulator such that at least a portion of the flow of hydraulic fluid exiting the swing motor from the second port is directed to be stored in the accumulator;

sensing a pressure of the hydraulic fluid stored in the accumulator; and

restricting the flow path from the second port of the swing motor to the accumulator when the pressure in the accumulator exceeds a first predetermined pressure.

12. The method for controlling a swing motor according to claim 11, further comprising:

accelerating by a predetermined amount the flow of hydraulic fluid through the swing motor into the first port and out the second port;

blocking the flow path from the second port of the swing motor to the accumulator; and

providing a flow path from the accumulator to the first port of the swing motor such that at least a portion of the flow of hydraulic fluid stored in the accumulator flows through the swing motor into the first port and out the second port.

13. The method for controlling a swing motor according to claim 12, further comprising:

providing a flow path from the pump to the swing motor.

14. The method for controlling a swing motor according to claim 11, further comprising:

accelerating by a predetermined amount the flow of hydraulic fluid through the swing motor into the first port and out the second port;

sensing the pressure of the hydraulic fluid stored in the accumulator;

blocking the flow path from the second port of the swing motor to the accumulator;

providing a flow path from the accumulator to the first port of the swing motor such that at least a portion of the flow of hydraulic fluid stored in the accumulator flows through the swing motor into the first port and out the second port when the pressure in the accumulator exceeds a first predetermined pressure; and

blocking the flow path from the accumulator to the first port of the swing motor when the pressure in the accumulator is less than a second predetermined pressure, the second predetermined pressure being less than the first predetermined pressure.

15. The method for controlling a swing motor according to claim 11, further comprising:

blocking the flow path from the second port of the swing motor to the accumulator when the pressure in the accumulator exceeds a second predetermined pressure, the second predetermined pressure being higher than the first predetermined pressure.

16. The method for controlling a swing motor according to claim 11, further comprising:

blocking the flow of hydraulic fluid into the first port of the swing motor and out the second port thereof;

directing a flow of hydraulic fluid through the second motor conduit into the second port of the swing motor and out of the first port of the swing motor through the first motor conduit to move the swing motor in a second direction, the second direction being in opposing relationship to the first direction;

accelerating by a predetermined amount the flow of hydraulic fluid into the second port of the swing motor and out the first port; and

providing a flow path from the accumulator to the second port of the swing motor such that at least a portion of the flow of hydraulic fluid stored in the accumulator flows through the swing motor into the second port and out the first port.

17. The method for controlling a swing motor according to claim 16, further comprising:

providing a flow path from the pump to the swing motor.

18. The method for controlling a swing motor according to claim 16, further comprising:

decelerating the flow of hydraulic fluid into the second port of the swing motor;

blocking the flow path from the accumulator to the second port of the swing motor; and

providing a flow path from the first port of the swing motor to the accumulator such that at least a portion of the flow of hydraulic fluid exiting the swing motor from the first port is directed into the accumulator.

19. The method for controlling a swing motor according to claim 18, further comprising:

accelerating by a predetermined amount the flow of hydraulic fluid into the second port of the swing motor and out the first port thereof;

blocking the flow path from the first port of the swing motor to the accumulator; and

providing a flow path from the accumulator to the second port of the swing motor such that at least a portion of the flow of hydraulic fluid stored in the accumulator flows through the swing motor into the second port and out the first port.