Power plants – Pressure fluid source and motor – Methods of operation
Reexamination Certificate
1999-09-23
2001-01-16
Lopez, F. Daniel (Department: 3745)
Power plants
Pressure fluid source and motor
Methods of operation
C060S445000, C060S468000
Reexamination Certificate
active
06173572
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a fluid circuit, and more particularly, to a method and apparatus for controlling the fluid flow in a fluid circuit.
BACKGROUND ART
Some hydraulic systems include a positive flow control system by combining an electronically actuated valve, e.g., a closed center control valve, with an electronically actuated displacement control pump. A positive flow control system may maximize efficiency while eliminating the mechanical complexity associated with traditional load sensing systems. In one embodiment, a positive flow control system provides improved system response, in part, by providing control commands to the pump and valves that are proportional to the operators inputs. Improved system response may be provided if the desired pressure may be quickly provided to the system, via the pump and the valves, when it is requested. However, unless the movement of the valves is accurately timed to the pump displacement, pressure spikes in the system will result. For example, if the valves close before the pump destrokes, then the remaining pump flow has nowhere to go but over the relief valve, which has several undesirable effects including increasing the pump motor work load.
Some approaches to this problem have attempted to add time delays to the pump or valve commands to insure, for example, that the control valves open before the pump is stroked up while the implement was accelerating, and the pump destroked before the valves where closed while the implement was decelerating. The nonlinear nature of the time delays makes the approach of adding time delays an ineffective solution.
The present invention is directed to overcoming one or more of the problems identified above.
DISCLOSURE OF THE INVENTION
In one embodiment of the present invention, an apparatus adapted to control the fluid flow in a fluid circuit is disclosed. The apparatus comprises a variable displacement pump adapted to receive a pump displacement command, and responsively deliver an actual fluid flow to the fluid circuit, a control valve connected to the pump, the control valve adapted to receive a control valve command signal and responsively control a position of said control valve, a bypass control valve connected between the pump and a tank, the bypass control valve adapted to receive a bypass valve command signal and responsively control a position of the bypass valve, and a controller adapted to establish a desired fluid flow, determine an expected fluid flow from the pump, and compare the desired fluid flow and the expected fluid flow.
In yet another embodiment, a method for controlling the fluid flow in a fluid circuit is disclosed. The fluid circuit includes a pump, a control valve connected to the pump, and a bypass control valve connected between the pump and a tank. The method includes the steps of establishing a desired fluid flow to be delivered by the pump, determining an expected fluid flow to be delivered by the pump in response to the desired fluid flow, and comparing the expected fluid flow and the desired fluid flow.
REFERENCES:
patent: 4938022 (1990-07-01), Hirata et al.
patent: 4945723 (1990-08-01), Izumi et al.
patent: 5267440 (1993-12-01), Nakamura et al.
patent: 5361211 (1994-11-01), Lee et al.
patent: 5394697 (1995-03-01), Hirata
patent: 5499503 (1996-03-01), Stoychoff
patent: 5540049 (1996-07-01), Lunzman
patent: 5609088 (1997-03-01), Park
patent: 5680760 (1997-10-01), Lunzman
Cobo Michael A.
Koehler Douglas W.
Caterpillar Inc.
Lopez F. Daniel
McPherson W. Bryan
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