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Hydraulic control unit with ambient temperature compensation during fluid pressure delivery

  • US 5,971,503 A
  • Filed: 02/03/1998
  • Issued: 10/26/1999
  • Est. Priority Date: 02/03/1998
  • Status: Expired due to Term
First Claim
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1. A hydraulic control system having a fluid pressure pump with a high pressure outlet side and a low pressure inlet side and having at least one fluid pressure operated member;

  • hydraulic pressure distributor conduits in a hydraulic circuit on said low pressure inlet side and between said pump and said pressure operated member;

    pressure distributor valve means including one solenoid valve actuator for controlling distribution of fluid pressure to said pressure operated member from said pump outlet and another solenoid valve actuator for controlling distribution of hydraulic fluid to said pump inlet; and

    electronic control circuit means for energizing said solenoid valve actuators at an energy level less than a threshold level at which said actuators will be activated to a changed state and for selectively energizing said solenoid valve actuators at an energy level above said threshold level to activate said actuators;

    said solenoid valve actuators being disposed in proximity to said hydraulic fluid whereby electrical energy distributed by said electronic control circuit means to said solenoid valve actuators develops heat that increases temperature at the low pressure inlet side of said pump, thereby decreasing hydraulic fluid viscosity when said actuators are energized at said energy level less than said threshold level.

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