Pressure control valve with reduced pilot flow and hydraulic control system with the same

A pressure control valve, comprising:

• a body, the body defining an axial bore, a supply port, a work port, and a tank port, each of the supply port, the work port, and the tank port being in fluid communication with the axial bore;
• a spool, the spool being disposed within the axial bore of the body and axially movable over a range of travel between:
• (i) a neutral position, in which the supply port and the work port are in fluid isolation from each other and the work port and the tank port are in fluid communication with each other, and (ii) a shifted position, in which the supply port and the work port are in fluid communication with each other and the work port and the tank port are in fluid isolation from each other;
• at least one of the spool and the body defining a pilot flow passage in fluid communication with the supply port and the tank port when the spool is in the neutral position;
• a biasing element, the biasing element operatively arranged with the spool to bias the spool to the neutral position;
• a pilot flow valve assembly, the pilot flow valve assembly configured to selectively occlude the pilot flow passage, the pilot flow valve assembly including a closure element movable between an open position in which the pilot flow passage is open and a closed position in which the pilot flow passage is occluded;
• means for restricting pilot flow through the pilot flow passage, the means for restricting pilot flow defining, when the spool is in the neutral position, a restricted pilot flow path along the pilot flow passage including a restriction, the restriction being configured to variably restrict flow of hydraulic fluid through the pilot flow passage, the restriction varying as a function of the spool position over the range of travel.

A hydraulic control system comprising:

• a pump, the pump adapted to provide a source of pressurized fluid;
• a tank, the tank adapted to hold a reservoir of fluid, the tank in fluid communication with the pump;
• an actuator, the actuator in selective fluid communication with the pump, the actuator defining a chamber therein adapted to receive pressurized fluid;
• a pressure control valve, the pressure control valve in fluid communication with the pump, the tank, and the actuator with the pressure control valve interposed between the pump and the actuator and between the actuator and the tank, the pressure control valve including:
• a body, the body defining an axial bore, a supply port, a work port, and a tank port, each of the supply port, the work port, and the tank port being in fluid communication with the axial bore, the supply port being in fluid communication with the pump, the work port being in fluid communication with the chamber of the actuator, the tank port being in fluid communication with the tank,
• a spool, the spool being disposed within the axial bore of the body and axially movable over a range of travel between (i) a neutral position, in which the supply port and the work port are in fluid isolation from each other and the work port and the tank port are in fluid communication with each other to thereby fluidly connect the chamber of the actuator to the tank, and (ii) a shifted position, in which the supply port and the work port are in fluid communication with each other to thereby fluidly connect the pump to the chamber of the actuator and the work port and the tank port are in fluid isolation from each other,
• at least one of the spool and the body defining a pilot flow passage, the pilot flow passage in fluid communication with the supply port and the tank port when the spool is in the neutral position,
• a biasing element, the biasing element operatively arranged with the spool to bias the spool to the neutral position,
• a pilot flow valve assembly, the pilot flow valve assembly configured to selectively occlude the pilot flow passage, the pilot flow valve assembly including a closure element movable between an open position in which the pilot flow passage is open and a closed position in which the pilot flow passage is occluded,
• a pilot flow control assembly, the pilot flow control assembly disposed in the pilot flow passage, the pilot flow control assembly including a first control element and a second control element, the first control element secured relative to the spool and the second control element secured relative to the body such that the first control element is axially movable with respect to the second control element upon axial movement of the spool, the first control element and the second control element defining, when the spool is in the neutral position, a restricted pilot flow path along the pilot flow passage including a restriction, the restriction varying as a function of the spool position over the range of travel such that the flow of hydraulic fluid through the pilot flow passage is variably restricted along the range of travel of the spool.