Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Reexamination Certificate
1999-05-26
2001-04-03
Fox, John (Department: 3753)
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
C361S160000
Reexamination Certificate
active
06209566
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to hydraulic control systems such as those used in the control of vehicle active suspension systems.
BACKGROUND OF THE INVENTION
It is known to provide closed loop pressure control in a hydraulic system by monitoring the hydraulic pressure at a point in a hydraulic circuit, comparing the measured pressure with a desired pressure, and controlling the electrical current to an electrically operated valve, such as a solenoid valve, to open or close the valve to adjust the pressure in the system towards the desired pressure.
It can be a problem with such systems that known pressure transducers have a temperature dependent characteristic, so the exact hydraulic pressure cannot be accurately measured.
SUMMARY OF THE INVENTION
The present invention provides a control system for a hydraulic valve block including an electrically operated valve, the system including an electronic control means arranged to supply an electric control current to the valve, the control current having a temperature dependent parameter, and the control means being further arranged to monitor said parameter thereby to measure the temperature of the valve.
The present invention further provides a hydraulic control system comprising a hydraulic circuit containing fluid and including a source of fluid pressure, an electrically operated valve for controlling the fluid pressure in a part of the hydraulic circuit, a pressure transducer for producing a pressure signal indicative of the fluid pressure in said part of the hydraulic circuit, and an electronic control means arranged to supply an electric control current to the valve to control the valve in response to signals from the pressure transducer, the control current having a temperature dependent parameter wherein the control unit is also arranged to monitor said parameter of the control current thereby to monitor the temperature of the valve, and to compensate accordingly for the effect of temperature changes on the pressure signal.
Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings.
REFERENCES:
patent: 4083001 (1978-04-01), Paice
patent: 5645352 (1997-07-01), Menten
patent: 2 165 649 (1986-04-01), None
Davis and Bujold
Fox John
Rover Group Limited
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