Dual mode hydraulic circuit control and method
AssigneeCaterpillar Inc.
InventorsHong-Chin Lin, Salem Haggag
Life of this patent
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Abstract
A dual mode control system for a hydraulic circuit (200) having a variable displacement pump (216) includes at least two actuators, each controlled by a respective valve. The valves are connected in series with a pressure sensor (250) measuring a pressure of fluid between the first valve (224) and the second valve (234) and relaying a signal to the electronic controller (202). The electronic controller (202) operates in a first mode, varying the displacement of the pump (216) based on a command signal operating at least one of the valves, and operates in a standby mode, varying the displacement of the pump (216) based on the signal from the sensor, when both valves are in their respective neutral positions.
Claims20
A hydraulic circuit operably associated with a vehicle, the hydraulic circuit including a variable displacement pump operated by an engine, the hydraulic circuit comprising:
- a first hydraulic actuator controlled by a first valve responsive to a first command signal, the first valve fluidly connected to an outlet of the pump;
- a second hydraulic actuator controlled by a second valve responsive to a second command signal, the second valve fluidly connected in series with the first valve, the first valve disposed between the second valve and the outlet of the pump;
- a sensor disposed in fluid communication with an intermediate conduit fluidly connecting the first valve with the second valve and measuring a pressure, the sensor relaying a signal to the electronic controller;
- the electronic controller disposed to operate in a first mode of operation when at least one of the first and second command signals is active;
- and
- the electronic controller disposed to operate in a standby mode of operation when the first and second command signals are inactive, the controller varying the displacement of the pump based on the signal.
A hydrostatically operated vehicle having a variable displacement hydraulic pump operably connected to an engine, the vehicle comprising:
- an implement operated by a first and second hydraulic pistons, the first and second hydraulic pistons disposed to selectively receive a flow of hydraulic fluid from the pump;
- a first valve disposed to receive the flow of hydraulic fluid from the pump and control the flow of fluid operating the first hydraulic piston;
- a second valve disposed to receive the flow of hydraulic fluid from the pump and control the flow of fluid operating the second hydraulic piston;
- a supply conduit fluidly connecting the pump with the first valve;
- an intermediate conduit fluidly connecting the first valve with the second valve;
- a pressure sensor disposed to measure fluid pressure in the intermediate conduit, the pressure sensor yielding a pressure signal;
- an electronic controller disposed to control the first and second valves, vary the displacement of the pump, and receive the pressure signal;
- the electronic controller operating in a first mode when at least one of the first and second valves is not in a neutral position;
- the electronic controller operating in a standby mode when the first valve and the second valve are in the neutral position, the controller varying the displacement of the pump based on the pressure signal.
A method of operating a hydraulic system, the system including a variable displacement pump fluidly connected to a first valve via a supply conduit, the first valve operating to control a flow of fluid operating a first actuator, the first valve fluidly connected to a second valve operating to control the flow of fluid operating a second actuator, the first valve responsive to a first command signal, the second valve responsive to a second command signal, the method comprising:
- determining whether at least one of the first and second command signal is inactive;
- when the first and second command signals are inactive;
- sensing a pressure of fluid disposed between the first valve and the second valve, and
- setting a displacement of the pump based on the pressure.
Dependencies are inferred from the claim text.