Pump device

Abstract

A pump device includes: a variable capacity-type pump unit configured to include an inner rotor having a plurality of external teeth , an outer rotor having a plurality of internal teeth meshing with a portion of the plurality of external teeth of the inner rotor, a housing, a suction port and a discharge port, an adjustment member adjusting a discharge pressure of a fluid, a biasing mechanism biasing the adjustment member, a control flow passage causing a fluid pressure from the discharge port to be applied to the adjustment member, a solenoid valve adjusting the fluid pressure applied to the adjustment member, a bypass flow passage, and a relief valve; a rotation speed sensor measuring a rotation speed of a drive source; and a control unit controlling the solenoid valve.

What is claimed is: 
     
         1 . A pump device comprising:
 a variable capacity-type pump unit configured to include
 an inner rotor having a plurality of external teeth and rotatable around a first shaft core, 
 an outer rotor having a plurality of internal teeth meshing with a portion of the plurality of external teeth of the inner rotor and rotatable around a second shaft core, 
 a housing accommodating the inner rotor and the outer rotor, 
 a suction port and a discharge port which are formed in the housing, 
 an adjustment member rotatably supporting the outer rotor and adjusting a discharge pressure of a fluid in the discharge port by changing a positional relationship between the first shaft core and the second shaft core, 
 a biasing mechanism biasing the adjustment member in a direction in which the discharge pressure is increased or decreased, 
 a control flow passage causing a fluid pressure from the discharge port to be applied to the adjustment member to apply a pressure to the adjustment member against a biasing force of the biasing mechanism, 
 a solenoid valve interposed in the control flow passage in order to adjust the fluid pressure to be applied to the adjustment member, 
 a bypass flow passage causing the fluid of the discharge port to flow into the suction port, and 
 a relief valve disposed in the bypass flow passage so as to be brought into an open state when the discharge pressure reaches a predetermined value or more; 
   a rotation speed sensor measuring a rotation speed per unit time of a drive source that drives the inner rotor or the outer rotor; and   a control unit controlling the solenoid valve,   wherein the control unit includes
 a pressure value conversion unit that converts a target discharge pressure into a conversion target discharge pressure serving as position information within a predetermined range in a definition region where a maximum discharge pressure and a minimum discharge pressure which are set based on the rotation speed of the drive source and a temperature of the fluid are respectively defined as a maximum value and a minimum value in the predetermined range, 
 a map data selection unit that stores first map data in which the relief valve is brought into an open state in the maximum discharge pressure and second map data in which the relief valve is brought into a closed state in the maximum discharge pressure, as map data having a data structure represented by an orthogonal coordinate system in which the definition region is denoted in a direction of a target axis and a target current value of the solenoid valve is denoted in a direction of an output axis orthogonal to the target axis, and that selects any one of the first map data and the second map data based on the rotation speed of the drive source measured by the rotation speed sensor and the temperature of the fluid measured by a temperature sensor, and 
 an output current control unit that acquires the target current value corresponding to the conversion target discharge pressure with reference to the selected map data, and that outputs the target current value to the solenoid valve. 
   
     
     
         2 . The pump device according to  claim 1 ,
 wherein the map data selection unit stores a plurality of items of the second map data in accordance with the maximum discharge pressure.   
     
     
         3 . The pump device according to  claim 1 , further comprising:
 a hydraulic pressure sensor measuring the discharge pressure,   wherein the target current value is controlled to be fed back, based on the discharge pressure measured by the hydraulic pressure sensor.