VARIABLE-DISPLACEMENT PUMP FOR SECURING DESIGN FLEXIBILITY BECAUSE A SUCTION PASSAGE IS NOT ALIGNED INEVITABLY IN THE REAR SIDE OF A SECOND OPERATING CHAMBER

摘要

PURPOSE: A variable-displacement pump is provided to allow design flexibility of the pump while keeping pressure of a second operating chamber low all the time. CONSTITUTION: A variable-displacement pump is composed of a rotor(5) mounted with plural vanes(6) extended radially, and rotated by a driving shaft(1); a cam ring(7) aligned on the main periphery of the rotor to swing about the rotor; a pair of closing members contacted slidably with the cam ring and arranged at both sides of the cam ring, wherein one of the closing members has a section having a suction port(22) on the lateral side of the cam ring; a seal member(11) disposed in a chamber formed between the cam ring and a pump housing(2) to split the chamber into two parts limiting first and second operating chambers(12,13); a spring(15) arranged in the second operating chamber to deviate the cam ring toward the first operating chamber in the direction of increasing volume of the pump chamber defined among the cam ring, the rotor, and the vane; a suction passage(18) sucking in working fluid through the suction port, inducing the working fluid into a suction area in the cam ring, and communicating with a second working fluid chamber while operating the pump; a discharge passage(20) for supplying the fluid from a discharge area in the cam ring to the outside; a communicating passage formed in at least one closing member along the section to communicate the fluid between the suction port and the second operating chamber; an orifice(21) installed at the discharge passage; and a control valve(26) operated by pressure difference between upper and lower sides of the orifice to control pressure of the working fluid inserted into the first operating chamber.