Internal gear pump

Abstract

To provide an internal gear pump which is able to stably ensure the sealing property between a resin casing constituting a trochoid accommodating portion and a cover, to omit the seal ring at the portion, and to stabilize the discharging ability. An internal gear pump 1 has a trochoid 4 in which an inner rotor 3 having a plurality of outer teeth is accommodated in an outer rotor 2 having a plurality of inner teeth in a state in which outer teeth mesh with inner teeth and are eccentric, and a casing 5 having a trochoid accommodating recess 5a formed therein, and a cover 6 which closes the recess 5a. The casing 5 is an injection-molded body of a resin composition. The casing 5 and the cover 6 are fixed with bolts. A metallic bush 7 is provided in the bolt fixing hole portion of the casing 5. In the cross-section of the joining portion between the casing 5 and the cover 6, the position of the end surface 7a of the bush 7 is higher than the bush formation surface 5e around the bush of the casing 5 and lower than the sealing surface 5d around the recess of the casing 5, as viewed from the bottom surface 5c of the recess 5a.

1 . An internal gear pump having a trochoid in which an inner rotor having a plurality of outer teeth is rotatably accommodated inside an outer rotor having a plurality of inner teeth in a state in which the outer teeth mesh with the inner teeth and are eccentric, and an suction side volume chamber configured to suck a liquid, and a discharge side volume chamber configured to discharge the liquid sucked into the suction side volume chamber are formed between the inner teeth and the outer teeth, the internal gear pump comprising:
 a casing having a recess which accommodates the trochoid; and   a cover which closes the recess of the casing,   wherein the casing is an injection-molded body of a resin composition,   the casing and the cover are fixed with bolts, a metallic bush is provided in a bolt fixing hole portion of the casing, and   a position of an end surface of the bush on the cover side in a cross-section of a joining portion between the casing and the cover is higher than a bush formation surface of the casing around the bush, and is the same as or lower than a sealing surface around the recess of the casing, as seen from a bottom surface of the recess.   
     
     
         2 . The internal gear pump according to  claim 1 , wherein the sealing surface is a surface which is continuous from an inner surface of the recess of the casing, and the sealing surface comes into close contact with the surface of the cover to seal the recess. 
     
     
         3 . The internal gear pump according to  claim 1 , wherein a seal ring is not interposed at a joining portion between the casing and the cover. 
     
     
         4 . The internal gear pump according to  claim 1 , wherein an inner surface of the recess of the casing is made of an injection-molded body of the resin composition, and a bottom surface of the recess is made of a metal body. 
     
     
         5 . The internal gear pump according to  claim 1 , wherein the resin composition is a resin composition in which a polyphenylene sulfide resin is used as a base resin, and the base resin is blended with at least one selected from a glass fiber, a carbon fiber, and an inorganic filler. 
     
     
         6 . An internal gear pump having a trochoid in which an inner rotor having a plurality of outer teeth is rotatably accommodated inside an outer rotor having a plurality of inner teeth in a state in which the outer teeth mesh with the inner teeth and are eccentric, and an suction side volume chamber configured to suck a liquid, and a discharge side volume chamber configured to discharge the liquid sucked into the suction side volume chamber are formed between the inner teeth and the outer teeth, the internal gear pump comprising:
 a trochoid accommodating portion made of sintered metal configured to accommodate the trochoid; and   a casing joined to the outside of the trochoid accommodating portion,   wherein the casing is an injection-molded body of a resin composition, and the trochoid accommodating portion and the casing are joined such that a part of the casing enters a sintered pore on the outer surface of the trochoid accommodating portion.   
     
     
         7 . The internal gear pump according to  claim 6 , wherein the trochoid accommodating portion includes a main body portion having a cylindrical inner surface and a flat plate-like inner bottom surface, and a lid portion which closes an opening portion of the main body portion. 
     
     
         8 . The internal gear pump according to  claim 7 , wherein the lid portion is caulked and fixed to the opening portion of the main body portion. 
     
     
         9 . The internal gear pump according to  claim 7 , wherein the trochoid accommodating portion and the casing are joined such that a part of the casing enters the sintered pore of the main body portion and the outer surface of the lid portion.