Engine Assist by Recovering Swing Kinetic Energy

• US 20160281329A1
• Filed: 03/25/2015
• Published: 09/29/2016
• Est. Priority Date: 03/25/2015
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Shang, Tonglin, Chen, Dayao, Ma, Pengfei
• Granted Patent: US 9,809,958 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: E02F 9/123 Drives or control devices specially adapted therefor E02F9/125 and E02F9/128 take precedence
• CPC Class Codes: E02F 9/128 Braking systems
• CPC Class Codes: E02F 9/2066 of the type combustion engines
• 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 9/2235 including an electronic controller
• 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 11/161 with sensing of servomotor demand or load
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 13/06 for use with two or more servomotors
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20507 Type of prime mover
• CPC Class Codes: F15B 2211/212 the pressure sources being accumulators
• CPC Class Codes: F15B 2211/30575 in a Wheatstone Bridge arrangement (also half bridges)
• CPC Class Codes: F15B 2211/7058 Rotary output members
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups
• CPC Class Codes: F15B 2211/88 Control measures for saving energy

Abstract

An energy recovery system for a machine having a movable work tool, a swing motor to swing the work tool about a vertical axis, a pump providing pressurized fluid to the swing motor, a power source outputting power to drive the pump, and a controller. The energy recovery system may include a first accumulator, a swing charge valve selectively connecting the swing motor to the first accumulator, an assist motor operatively connected to the power source, and a discharge selectively connecting the first accumulator to the assist motor. The swing charge valve may fluidly connect the swing motor to the first accumulator when fluid pressure from the swing motor is greater than a charge set pressure. The controller may cause the discharge valve to fluidly connect the first accumulator with the assist motor when the power demand on the power source is greater than a minimum assisted power demand.

Claims

1. A machine, comprising:

a work tool movable through a range of motion;

a swing motor configured to swing the work tool about a vertical axis;

a pump selectively fluidly connected to the swing motor to provide pressurized fluid to cause the swing motor to swing the work tool;

a power source operatively connected to the pump to output power to drive the pump;

an energy recovery system comprising;

a first accumulator,

a swing charge valve having a normally closed position, an open position, and a charge set pressure, the swing charge valve being positioned to selectively fluidly connect the swing motor to the first accumulator, wherein the swing charge valve moves from the normally closed position to the open position and fluidly connects the swing motor to the first accumulator when a swing motor fluid pressure communicated to the swing charge valve from the swing motor is greater than the charge set pressure,

an assist motor operatively connected to the power source, and

a discharge valve having a normally closed position and an open position, the discharge valve being positioned to selectively fluidly connect the first accumulator to the assist motor; and

a controller operatively connected to the discharge valve, wherein;

the controller is configured to determine a power demand on the power source for output power, and

the controller is configured to cause the discharge valve to move from the normally closed position to the open position to fluidly connect the first accumulator with the assist motor in response determining that the power demand on the power source for output power is greater than a minimum assisted power demand.

2. The machine of claim 1, wherein the first accumulator has a first accumulator maximum charge pressure, and the charge set pressure of the swing charge valve is less than the first accumulator maximum charge pressure.

3. The machine of claim 1, wherein movement of the discharge valve between the normally closed position and the open position caused by the controller occurs independent of a position of the swing charge valve.

4. The machine of claim 1, wherein the controller is configured to determine a first accumulator charge pressure of the first accumulator, and the controller is configured to cause the discharge valve to move from the normally closed position to the open position to fluidly connect the first accumulator with the assist motor in response determining that the power demand on the power source for output power is greater than the minimum assisted power demand and the first accumulator charge pressure is greater than or equal to a minimum accumulator discharge pressure.

5. The machine of claim 1, wherein the machine comprises a boom hybrid circuit for raising and lowering the work tool, wherein the boom hybrid circuit is selectively fluidly connected to the assist motor to provide pressurized fluid thereto.

6. The machine of claim 1, comprising:

a low-pressure fluid reservoir;

a relief valve having a normally closed position, an open position, and a relief set pressure that is greater than the charge set pressure, the relief valve being positioned to selectively fluidly connect the swing motor to the low-pressure fluid reservoir, wherein the relief valve moves from the normally closed position to the open position and fluidly connects the swing motor to the low-pressure fluid reservoir when the swing motor fluid pressure communicated to the swing charge valve and the relief valve from the swing motor is greater than the relief set pressure.

7. The machine of claim 6, comprising a low-pressure return passage fluidly connecting the relief valve to the low-pressure fluid reservoir, and wherein the energy recovery system comprises:

a second accumulator fluidly connected to the low-pressure return passage; and

a back pressure valve having a normally closed position, an open position, and a maximum back pressure, the back pressure valve being positioned along the low-pressure return passage between the relief valve and the low-pressure fluid reservoir to selectively fluidly connect the relief valve to the low-pressure fluid reservoir, wherein the back pressure valve moves from the normally closed position to the open position and fluidly connects the relief valve to the low-pressure fluid reservoir when a pressure in the low-pressure return passage is greater than the maximum back pressure.

8. A method for recovering swing kinetic energy in a hydraulic system of a machine, comprising:

providing pressurized fluid to a swing motor with a pump of the machine to cause the swing motor to swing a work tool of the machine about a vertical axis;

sensing a fluid pressure from the swing motor at a swing charge valve;

opening the swing charge valve to fluidly connect the swing motor to a first accumulator in response to a sensed fluid pressure from the swing motor being greater than or equal to a charge set pressure of the swing charge valve and causing the swing charge valve to move from a normally closed position toward an open position;

selectively fluidly connecting the first accumulator to an assist motor via a discharge valve, wherein the assist motor is operatively connected to a power source of the machine;

determining a power demand on the power source for output power; and

causing the discharge valve to fluidly connect the first accumulator with the assist motor in response determining that the power demand on the power source for output power is greater than a minimum assisted power demand.

9. The method for recovering swing kinetic energy of claim 8, wherein a first accumulator maximum charge pressure of the first accumulator is greater than the charge set pressure of the swing charge valve.

10. The method for recovering swing kinetic energy of claim 8, wherein causing the discharge valve to fluidly connect the first accumulator with the assist motor occurs independent of a position of the swing charge valve.

11. The method for recovering swing kinetic energy of claim 8, comprising:

determining a first accumulator charge pressure of the first accumulator;

causing the discharge valve to fluidly connect the first accumulator with the assist motor in response determining that the power demand on the power source for output power is greater than the minimum assisted power demand and the first accumulator charge pressure is greater than or equal to a minimum accumulator discharge pressure.

12. The method for recovering swing kinetic energy of claim 8, selectively fluidly connecting a boom hybrid circuit for raising and lowering the work tool to the assist motor to provide pressurized fluid thereto.

13. The method for recovering swing kinetic energy of claim 8, comprising:

providing a relief valve between the swing motor and a low-pressure fluid reservoir to selectively fluidly connect the swing motor to the low-pressure fluid reservoir;

opening the relief valve to fluidly connect the swing motor to the low-pressure fluid reservoir in response to a swing motor fluid pressure communicated to the swing charge valve and the relief valve from the swing motor being greater than a relief set pressure of the relief valve.

14. An energy recovery system for a machine having a work tool movable through segments of an excavation cycle, a swing motor configured to swing the work tool about a vertical axis, a pump selectively fluidly connected to the swing motor to provide pressurized fluid to cause the swing motor to swing the work tool, a power source operatively connected to the pump to output power to drive the pump, and a controller, the energy recovery system comprising:

a first accumulator;

a swing charge valve having a normally closed position, an open position, and a charge set pressure, the swing charge valve being positioned to selectively fluidly connect the swing motor to the first accumulator, wherein the swing charge valve moves from the normally closed position to the open position and fluidly connects the swing motor to the first accumulator when a swing motor fluid pressure communicated to the swing charge valve from the swing motor is greater than the charge set pressure;

an assist motor operatively connected to the power source; and

a discharge valve having a normally closed position and an open position, the discharge valve being positioned to selectively fluidly connect the first accumulator to the assist motor,

wherein the controller is configured to determine a power demand on the power source to output power, and to cause the discharge valve to move from the normally closed position to the open position to fluidly connect the first accumulator with the assist motor in response determining that the power demand on the power source is greater than a minimum assisted power demand.

15. The energy recovery system of claim 14, wherein the first accumulator has a first accumulator maximum charge pressure, and the charge set pressure of the swing charge valve is less than the first accumulator maximum charge pressure.

16. The energy recovery system of claim 14, wherein movement of the discharge valve between the normally closed position and the open position caused by the controller occurs independent of a position of the swing charge valve.

17. The energy recovery system of claim 14, wherein the controller is configured to determine a first accumulator charge pressure of the first accumulator, and the controller is configured to cause the discharge valve to move from the normally closed position to the open position to fluidly connect the first accumulator with the assist motor in response determining that the power demand on the power source for output power is greater than the minimum assisted power demand and the first accumulator charge pressure is greater than or equal to a minimum accumulator discharge pressure.

18. The energy recovery system of claim 14, wherein the machine includes a boom hybrid circuit for raising and lowering the work tool, wherein the boom hybrid circuit is selectively fluidly connected to the assist motor to provide pressurized fluid thereto.

19. The energy recovery system of claim 14, wherein the machine includes a low-pressure fluid reservoir and a relief valve having a normally closed position, an open position, and a relief set pressure that is greater than the charge set pressure, the relief valve being positioned to selectively fluidly connect the swing motor to the low-pressure fluid reservoir, wherein the relief valve moves from the normally closed position to the open position and fluidly connects the swing motor to the low-pressure fluid reservoir when the swing motor fluid pressure communicated to the swing charge valve and the relief valve from the swing motor is greater than the relief set pressure.

20. The energy recovery system of claim 19, wherein the machine comprises a low-pressure return passage fluidly connecting the relief valve to the low-pressure fluid reservoir, the energy recovery system comprising:

a second accumulator fluidly connected to the low-pressure return passage; and

a back pressure valve having a normally closed position, an open position, and a maximum back pressure, the back pressure valve being positioned along the low-pressure return passage between the relief valve and the low-pressure fluid reservoir to selectively fluidly connect the relief valve to the low-pressure fluid reservoir, wherein the back pressure valve moves from the normally closed position to the open position and fluidly connects the relief valve to the low-pressure fluid reservoir when a pressure in the low-pressure return passage is greater than the maximum back pressure.