Hydraulic pump

Abstract

A hydraulic pump includes a cylinder block having a cylinder, a rotor rotatable in the cylinder, and a vane movable in a radial direction of the rotor and biased to the rotor. The vane, the cylinder, and the rotor thereamong define an operation chamber. The rotor draws fluid into the operation chamber and sends the fluid outside the operation chamber. The vane is urged to the rotor according to differential pressure between pressure of fluid at high-pressure in the operation chamber and pressure of fluid at low-pressure in the operation chamber. The vane and the rotor define a hardness ratio being calculated by dividing hardness of the vane by hardness of the rotor, and the hardness ratio is greater than or equal to 1.6.

1 . A hydraulic pump comprising:
 a cylinder block having a cylinder;   a rotor rotatable in the cylinder; and   a vane movable substantially in a radial direction of the rotor and configured to be biased to the rotor;   wherein the vane, the cylinder, and the rotor thereamong define an operation chamber,   the rotor is configured to draw fluid into the operation chamber and configured to send the fluid outside the operation chamber,   the vane is configured to be urged to the rotor according to differential pressure between pressure of fluid at high-pressure in the operation chamber and pressure of fluid at low-pressure in the operation chamber,   the vane and the rotor define a hardness ratio being calculated by dividing hardness of the vane by hardness of the rotor, and   the hardness ratio is greater than or equal to 1.6.   
   
   
       2 . The hydraulic pump according to  claim 1 , wherein the hardness ratio is less than or equal to 2.5. 
   
   
       3 . The hydraulic pump according to  claim 1 ,
 wherein the vane is formed from tool steel being quenched and tempered, and   the rotor is formed from case-hardened steel being carburized, quenched, and tempered.   
   
   
       4 . The hydraulic pump according to  claim 3 , wherein the vane is formed from the tool steel nitrided after being carburized, quenched, and tempered. 
   
   
       5 . The hydraulic pump according to  claim 1 , wherein the vane and the rotor therebetween define a sliding portion, in which:
 a surface roughness Rz of the vane is equal to or less than 0.3, and   a surface roughness Rz of the rotor is equal to or less than 0.1.   
   
   
       6 . The hydraulic pump according to  claim 1 , the hydraulic pump being used for a vehicle. 
   
   
       7 . The hydraulic pump according to  claim 6 , the hydraulic pump being used for a waste heat recovery cycle for the vehicle. 
   
   
       8 . The hydraulic pump according to  claim 7 , wherein the waste heat recovery cycle is a Rankine cycle.