Hydraulic control apparatus

Details Hydraulic control apparatus Hydraulic control apparatus

1989-11-29

1990-10-02

Michalsky, Gerald A

Pumps

Condition responsive control of drive transmission or pump...

Adjustable cam or linkage

137330, 13762564, 13762565, 25112905, F15B 13043, F15B 13044

Patent

active

049603655

ABSTRACT:
A hydraulic control apparatus has a transistor which is changed over by a control signal inputted to an input terminal thereof; and a solenoid controlled valve having a spool actuated by a DC solenoid to be driven by exciting current whose pulse duration has been controlled by the transistor. The hydraulic control apparatus is characterized by having an adder for adding a command signal and an AC signal having a dither frequency; an oscillator for generating a signal having a constant frequency higher than the maximum frequency of the command signal; a subtractor for subtracting a signal representing pulse duration of the exciting current and inputted through a low-pass filter from a signal outputted from the adder; and a comparator for comparing a signal outputted from the subtractor with a signal outputted from the oscillator, outputting a pulse width-modulated control signal to the input terminal of the transistor so as to control the ON and OFF of the transistor, so that the solenoid controlled valve can be controlled with a fast response and high gain and a small amount of phase delay.

REFERENCES:
patent: 4456434 (1984-06-01), El Ibiary

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