Internal gear pump

Abstract

To provide an internal gear pump capable of suppressing a liquid discharge amount during a high-speed rotation by controlling discharge pressure while achieving reduction in size, weight, cost, and the like. An internal gear pump 1 includes: a trochoid 4 in which an inner rotor 3 having a plurality of external teeth is accommodated inside an outer rotor 2 having a plurality of internal teeth in an eccentrically rotatable manner with the external teeth and the internal teeth interdigitated with each other, and a suction-side volume chamber for sucking liquid and a discharge-side volume chamber for discharging the liquid sucked into the suction-side volume chamber are formed between the internal teeth and the external teeth; a casing formed with a recessed part 8 for accommodating the trochoid 4 ; and a cover 6 that closes the recessed part 8 . An ejector 9 is provided to communicate with a flow passage of the liquid formed on a bottom surface of the recessed part 8 and to partially discharge the liquid in an accommodation space of the trochoid formed by the casing and the cover 6.

1 . An internal gear pump including a trochoid in which an inner rotor having a plurality of external teeth is accommodated inside an outer rotor having a plurality of internal teeth in an eccentrically rotatable manner with the external teeth and the internal teeth interdigitated with each other, and a suction-side volume chamber for sucking liquid and a discharge-side volume chamber for discharging the liquid sucked into the suction-side volume chamber are formed between the internal teeth and the external teeth, the internal gear pump comprising:
 a casing formed with a recessed part for accommodating the trochoid; and   a cover that closes the recessed part of the casing,   wherein an ejector is provided to communicate with a flow passage of the liquid formed on a bottom surface of the recessed part and to partially discharge the liquid in an accommodation space of the trochoid formed by the casing and the cover.   
     
     
         2 . The internal gear pump according to  claim 1 , wherein the ejector comprises:
 a housing;   a cylindrical body provided in the housing; and   an elastic body that presses the cylindrical body in a direction opposite to pressure of the liquid in the flow passage of the liquid,   wherein the liquid is partially discharged from a discharge flow passage between the cylindrical body and the housing formed when the elastic body is contracted in a direction opposite to the pressing direction by the pressure of the liquid via the cylindrical body, and   the housing and the cylindrical body include a resin body.   
     
     
         3 . The internal gear pump according to  claim 2 , wherein a through hole communicating with the ejector is provided in a part of the flow passage of the liquid formed on the bottom surface of the recessed part, and a chamfered portion of an end portion of the cylindrical body is pressed to a chamfered portion of the through hole facing a side of the ejector. 
     
     
         4 . The internal gear pump according to  claim 1 , wherein an inner side surface of the recessed part of the casing includes a resin body, the bottom surface of the recessed part includes a metal body, and the ejector is fixed to the metal body. 
     
     
         5 . The internal gear pump according to  claim 1 , wherein the casing includes a liquid suction part forming a part of a flow passage to the suction-side volume chamber of the liquid, and in the casing, a part including the recessed part and a part including the liquid suction part are configured separately from each other. 
     
     
         6 . The internal gear pump according to  claim 1 , wherein the internal gear pump includes a suction port for introducing the liquid inside the accommodation space of the trochoid and the ejector on the bottom surface of the recessed part, and
 the ejector is configured to partially discharge the liquid from the suction port through a discharge flow passage by forming the discharge flow passage communicating the flow passage and the suction port in accordance with pressure of the liquid.   
     
     
         7 . The internal gear pump according to  claim 6 , wherein the inner side surface of the recessed part of the casing includes a resin body, the bottom surface of the recessed part includes a metal plate embedded in the resin body of the casing, and the ejector is installed within a thickness of the metal plate. 
     
     
         8 . The internal gear pump according to  claim 6 , wherein the ejector comprises:
 a cylindrical body; and   an elastic body that presses the cylindrical body in a direction opposite to the pressure of the liquid in the flow passage of the liquid and is a horizontal direction of the metal plate,   wherein the elastic body is deformed by the pressure of the liquid via the cylindrical body, so that the pressing is released and the discharge flow passage is formed.   
     
     
         9 . The internal gear pump according to  claim 8 , wherein the elastic body includes a coil spring, a torsion spring, a leaf spring, or a tension spring. 
     
     
         10 . The internal gear pump according to  claim 8 , wherein the cylindrical body is made of a resin and the elastic body does not come into contact with the outer rotor and the inner rotor. 
     
     
         11 . The internal gear pump according to  claim 8 , wherein a through hole communicating with the ejector is provided in a part of the flow passage of the liquid formed on the bottom surface of the recessed part, and in a state in which the pressing is not released, a tapered portion of the cylindrical body is pressed to an inclined portion of the through hole facing a side of the ejector, so that the flow passage is sealed by surface contact. 
     
     
         12 . The internal gear pump according to  claim 1 , wherein at least one member of the casing and the cover includes a molded body of a resin composition, and
 the casing and the cover are fixed by fitting a plurality of protrusion parts protruding from one member to another member.   
     
     
         13 . The internal gear pump according to  claim 12 , wherein the casing and the cover are integrated with each other by a fixing member passing through a metal bush across the casing and the cover, and
 at least one of the protrusion parts is a protrusion part of the metal bush protruding from one member of the casing and the cover and fixed to the one member.   
     
     
         14 . The internal gear pump according to  claim 12 , wherein at least one of the protrusion parts is a claw part protruding as a part of the molded body in one member of the casing and the cover. 
     
     
         15 . The internal gear pump according to  claim 12 , wherein the resin composition is a resin composition in which a polyphenylene sulfide resin is used as a base resin, and at least one selected from a glass fiber, a carbon fiber, and an inorganic filler is blended in the polyphenylene sulfide resin.