ROTARY PUMP

TECHNICAL FIELD

The present disclosure relates to a rotary pump.

BACKGROUND ART

A rotary pump described in PATENT LITERATURE 1 has been known as a rotary pump that performs suction and discharge of fluid by rotating a pump rotor. The rotary pump described in PATENT LITERATURE 1 includes a pump rotor, and a housing that rotatably houses the pump rotor.

Generally, a clearance for allowing rotation of the pump rotor is set between sliding surfaces of the housing and the pump rotor. If this clearance is large, a leakage amount of fluid increases and a discharge amount of a pump decreases. Therefore, the clearance between the sliding surfaces of the housing and the pump rotor is preferably small. However, if the clearance is too small, seizure is likely to occur between the housing and the pump rotor. Therefore, the clearance between the sliding surfaces of the housing and the pump rotor is usually set to several tens of micrometers or more.

The inventors of the present application have developed a rotary pump in which a clearance between sliding surfaces of a housing and a pump rotor can be set to be extremely small while avoiding seizure between the housing and the pump rotor, and proposed a rotary pump disclosed in PATENT LITERATURE 2.

The rotary pump disclosed in PATENT LITERATURE 2 includes a pump rotor, and a housing that rotatably houses the pump rotor. One or both of the housing and the pump rotor are coated with crosslinked fluororesin. Since crosslinked fluororesin has a low coefficient of friction and a high wear resistance, if one or both of the housing and the pump rotor are coated with crosslinked fluororesin, seizure between the housing and the pump rotor can be avoided over a long period of time even when the clearance between the sliding surfaces of the housing and the pump rotor is set to be extremely small.

CITATION LIST
Patent Literature

PATENT LITERATURE 1: Japanese Laid-Open Patent Publication No. 2014-47751

PATENT LITERATURE 2: Japanese Laid-Open Patent Publication No. 2014-173513

SUMMARY OF THE INVENTION
Solution to Problem

A rotary pump according to an aspect of the present disclosure is a rotary pump including:

- a pump rotor having a flat rotor side surface facing in an axial direction;
- a housing body having an opening in the axial direction and a flat flange surface formed around the opening, the housing body rotatably housing the pump rotor in the opening such that the rotor side surface is flush with the flange surface; and
- a cover member having a flat mating surface that is fixed while being pressed against the flange surface by fastening of a bolt, and a flat sliding/guiding surface that slides and guides the rotor side surface, wherein
- the cover member is formed of a crosslinked fluororesin and a metal body,
- the metal body is provided with the mating surface, and a recess formed by recessing an area, of the metal body, corresponding to the sliding/guiding surface, in the axial direction with respect to the mating surface, and
- the crosslinked fluororesin is filled in the recess so as to form the sliding/guiding surface flush with the mating surface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view of a rotary pump according to a first embodiment of the present disclosure.

FIG. 2 is a front view of the rotary pump shown in FIG. 1.

FIG. 3 is a cross-sectional view taken along a III-III line in FIG. 2.

FIG. 4 is a cross-sectional view take along a IV-IV line in FIG. 3.

FIG. 5 is an enlarged view around the pump rotor shown in FIG. 3.

FIG. 6 is a cross-sectional view taken along a VI-VI line in FIG. 2.

FIG. 7 illustrates a process of manufacturing a side cover shown in FIG. 5.

FIG. 8 is an exploded perspective view of a rotary pump according to a second embodiment of the present disclosure.

FIG. 9 is an enlarged cross-sectional view showing the rotary pump of FIG. 8 corresponding to FIG. 5.

FIG. 10 is an exploded perspective view of a rotary pump according to a third embodiment of the present disclosure.

FIG. 11 is an enlarged cross-sectional view showing the rotary pump of FIG. 10 corresponding to FIG. 5.

FIG. 12 shows a rotary pump according to a fourth embodiment of the present disclosure corresponding to FIG. 4.

FIG. 13 is a cross-sectional view taken along an line in FIG. 12.

FIG. 14 is an enlarged view around a pump rotor shown in FIG. 13.

DETAILED DESCRIPTION
Problems to be Solved by the Present Disclosure

The inventors of the present application have advanced in-house development of the rotary pump in which at least one of the housing and the pump rotor is coated with crosslinked fluororesin as described in PATENT LITERATURE 2, and considered mass production of a rotary pump in which a housing is coated with crosslinked fluororesin.

The housing is composed of a housing body, and a cover member fixed to the housing body by a bolt. The housing body has an opening in the axial direction, and a fiat flange surface formed around the opening. The housing body rotatably houses the pump rotor in the opening. The cover member has a flat mating surface that is fixed while being pressed against the flange surface around the opening of the housing body, by fastening of a bolt; and a flat sliding/guiding surface that slides and guides a flat side surface (rotor side surface) in the axial direction of the pump rotor. The mating surface and the sliding/guiding surface are a contiguous flat surface.

The inventors have produced an in-house prototype in which one surface of the cover member made of a metal (i.e., the contiguous flat surface including the mating surface to the housing body and the sliding/guiding surface that slides and guides the rotor side surface of the pump rotor) is coated with a crosslinked fluororesin coating, and evaluated pump performance, with the cover member of the prototype being fixed by a bolt to the housing body housing the pump rotor. Then, the inventors have found that a torque for rotationally driving the pump rotor sometimes becomes larger than expected.

The inventors have investigated the cause of the torque, for rotationally driving the pump rotor, becoming larger than expected, and found the following. That is, when the cover member is fixed to the housing body by the bolt, the crosslinked fluororesin coating formed on the mating surface, to the housing body, of the cover member is compressed and deformed due to bolt fastening force, and the compressive deformation causes the thickness of the crosslinked fluororesin coating to be reduced by about 1 μm to about 10 μm, whereby the position of the sliding/guiding surface of the cover member is slightly shifted in the axial direction. As a result, a clearance in the axial direction between the cover member and the pump rotor becomes slightly smaller than a design value, and the torque for rotationally driving the pump rotor is more likely to be larger than expected, particularly when the clearance is set to an extremely small size not larger than 20 μm.

Therefore, an object of the present disclosure is to provide a rotary pump which allows accurate control of a clearance in the axial direction between a cover member and a pump rotor, when a sliding/guiding surface, of the cover member, for the pump rotor is formed of crosslinked fluororesin and the cover member is fixed to a housing body by a bolt.

Effects of the Present Disclosure

According to the present disclosure, it is possible to accurately control a clearance in the axial direction between a cover member and a pump rotor, when a sliding/guiding surface, of the cover member, for the pump rotor is formed of crosslinked fluororesin and the cover member is fixed to a housing body by a bolt.

Description of Embodiment of the Present Disclosure

(1) A rotary pump according to an aspect of the present disclosure is a rotary pump including:

- a pump rotor having a flat rotor side surface facing in an axial direction
- a housing body having an opening in the axial direction and a flat flange surface formed around the opening, the housing body rotatably housing the pump rotor in the opening such that the rotor side surface is flush with the flange surface; and
- a cover member having a flat mating surface that is fixed while being pressed against the flange surface by fastening of a bolt, and a flat sliding/guiding surface that slides and guides the rotor side surface, wherein
- the cover member is formed of a crosslinked fluororesin and a metal body,
- the metal body is provided with the mating surface, and a recess obtained by recessing an area corresponding to the sliding/guiding surface, in the axial direction with respect to the mating surface, and
- the crosslinked fluororesin is filled in the recess so as to form the sliding/guiding surface flush with the mating surface.

In the above configuration, since the sliding/guiding surface, of the cover member, for the pump rotor is formed of the crosslinked fluororesin, even when a clearance between the cover member and the pump rotor is set to be extremely small, seizure between the cover member and the pump rotor can be avoided over a long period of time. Moreover, since the mating surface, of the cover member, to the housing body is formed on the metal body as a component of the cover member, fastening force of the bolt can be supported with rigidity by the metal body, thereby preventing the positions of the sliding/guiding surface of the cover member from being shifted in the axial direction due to the fastening force of the bolt. Therefore, when the cover member is fixed to the housing body by the bolt, a clearance in the axial direction between the cover member and the pump rotor can be accurately controlled.

(2) The cover member is preferably a plate-shaped side cover that is fixed by being sandwiched between the housing body and a cover body disposed so as to oppose the flange surface of the housing body.

With the above configuration, the rotary pump according to the aspect of the present disclosure can be obtained by additionally incorporating the plate-shaped side cover between a housing body and a cover member of an existing rotary pump.

(3) The recess preferably has a shape obtained by recessing, in the axial direction, also an area corresponding to a part of the mating surface such that the crosslinked fluororesin filled in the recess is in contact with the flange surface in an annular area contiguous, without a break, around the opening.

In the above configuration, since the crosslinked fluororesin filled in the recess is in contact with the flange surface in the annular area contiguous, without a break, around the opening of the housing body, the contact surfaces of the cover member and the housing body can be sealed with the crosslinked fluororesin, thereby avoiding leakage of fluid. Moreover, since the crosslinked fluororesin forming the mating surface is contiguous with the crosslinked fluororesin forming the sliding/guiding surface, production cost can be suppressed.

(4) The mating surface and the sliding/guiding surface may be a contiguous machined surface having a surface roughness not greater than a ten-point average roughness Rz_JISof 6.3 μm.

In the above configuration, since the mating surface and the sliding/guiding surface can be simultaneously subjected to finish machining, cost reduction is achieved. Moreover, since the surface roughness of the mating surface and the sliding/guiding surface is not greater than Rz_JISof 6.3 μm, a clearance in the axial direction between the cover member and the pump rotor can be controlled extremely accurately.

(5) The pump rotor may be composed of: an inner rotor having, at an outer periphery thereof, a plurality of outer teeth; and an annular outer rotor supported to be rotatable around a position eccentric from a center of the inner rotor, the outer rotor having, at an inner periphery thereof, a plurality of inner teeth meshing with the outer teeth.

(6) The pump rotor may be composed of: a rotor body having, at an outer periphery thereof, a plurality of vane-containing grooves; and a plurality of vanes contained in the respective vane-containing grooves so as to be slidable in a radial direction.

Details of Embodiment of the Present Disclosure

Hereinafter specific examples of rotary pumps according to embodiments of the present disclosure will be described with reference to the drawings. The present invention is not limited to these examples and is indicated by the claims, and is intended to include meaning equivalent to the claims and all modifications within the scope of the claims.

FIG. 1 to FIG. 6 show a rotary pump according to a first embodiment of the present disclosure. The rotary pump includes: a pump rotor 2 rotationally driven by a rotation shaft 1; a housing body 3 that houses the pump rotor 2; a first cover body 4a and a first side cover 5a disposed on one side in the axial direction of the housing body 3; and a second cover body 4b and a second side cover 5b disposed on the other side in the axial direction of the housing body 3.

As shown in FIG. 1 and FIG. 4, the pump rotor 2 is composed of: an inner rotor 7 having, at an outer periphery thereof, a plurality of outer teeth 6; and an annular outer rotor 9 haying, at an inner periphery thereof, a plurality of inner teeth 8 that mesh with the outer teeth 6. The inner rotor 7 and the outer rotor 9 are rotatably housed in an opening 10, in the axial direction, formed in the housing body 3.

As shown in FIG. 3, the inner rotor 7 has an axial hole 11 into which the rotation shaft 1 is inserted. The rotation shaft 1 and the axial hole 11 are fitted to each other such that the rotation shaft 1 and the inner rotor 7 integrally rotate. Fitting of the rotation shaft 1 and the axial hole 11 is not limited to width-across-flat fitting shown in FIG. 3. Spline fitting, key groove fitting, or a fitting with an interference between cylindrical surfaces (shrinkage fitting or press fitting) may be adopted.

As shown in FIG. 4, the outer rotor 9 has an outer peripheral cylindrical surface 12. The outer peripheral cylindrical surface 12 is fitted to an inner periphery of the opening 10 of the housing body 3 with a gap therebetween, and this fitting rotatably supports the outer rotor 9, The outer rotor 9 is supported to be rotatable around a position eccentric from a center position of the inner rotor 7 (i.e., a rotation center position of the rotation shaft 1). When the inner rotor 7 is rotated, the outer rotor 9 rotates together with the inner rotor 7 due to meshing of the inner teeth 8 with the outer teeth 6. The rotation direction of the inner rotor 7 is the clockwise direction in FIG. 4.

The number of the inner teeth 8 of the outer rotor 9 is larger by one than the number of the outer teeth 6 of the inner rotor 7. A plurality of chambers 13 (spaces for containing fluid) demarcated by the respective outer teeth 6 and the respective inner teeth 8 are formed between the outer periphery of the inner rotor 7 and the inner periphery of the outer rotor 9. The plurality of chambers 13 are configured such that the volume of each chamber 13 changes with rotation of the inner rotor 7 and the outer rotor 9. That is, the volume of each chamber 13 is maximum at an angular position (upper position in FIG. 4) at which the center of the inner rotor 7 and the center of the outer rotor 9 are most distant from each other, and gradually decreases as the chamber 13 approaches an angular position (lower position in FIG. 4) at which the center of the inner rotor 7 and the center of the outer rotor 9 are closest to each other. Therefore, when the inner rotor 7 and the outer rotor 9 rotate, on a side (right side in FIG. 4) where the chamber 13 moves from the angular position at which the center of the inner rotor 7 and the center of the outer rotor 9 are most distant from each other, toward the angular position at which the center of the inner rotor 7 and the center of the outer rotor 9 are closest to each other, the volume of the chamber 13 is reduced and thereby a fluid discharge effect occurs. Meanwhile, on a side (left side in FIG. 4) where the chamber 13 moves from the angular position at which the center of the inner rotor 7 and the center of the outer rotor 9 are closest to each other, toward the angular position at which the center of the inner rotor 7 and the center of the outer rotor 9 are most distant from each other, the volume of the chamber 13 gradually increases and thereby a fluid suction effect occurs.

As shown in FIG. 5, the inner rotor 7 has: a flat first inner rotor side surface 14a facing one side (left side in FIG. 5) in the axial direction; and a flat second inner rotor side surface 14b facing the other side (right side in FIG. 5) in the axial direction. The first inner rotor side surface 14a and the second inner rotor side surface 14b are parallel flat surfaces facing opposite to each other in the axial direction. The outer rotor 9 has a flat first outer rotor side surface 15a facing one side in the axial direction, and a fiat second outer rotor side surface 15b facing the other side in the axial direction. The first outer rotor side surface 15a and the second outer rotor side surface 15b are parallel flat surfaces facing opposite to each other in the axial direction.

A width dimension in the axial direction of the inner rotor 7 from the first inner rotor side surface 14a to the second inner rotor side surface 14b is equal to a width dimension in the axial direction of the outer rotor 9 from the first outer rotor side surface 15a to the second outer rotor side surface 15b. The first inner rotor side surface 14a and the first outer rotor side surface 15a are flush with each other, and the second inner rotor side surface 14b and the second outer rotor side surface 15b are also flush with each other. Both the inner rotor 7 and the outer rotor 9 are formed of a sintered parts. The sintered parts is a member obtained by compression-molding an iron-base powder material by using a mold to form a powder molded body, and heating the powder molded body at a high temperature equal to or lower than a melting point.

As shown in FIG. 3, the axial hole 11 into which the rotation shaft 1 is inserted is a through-hole penetrating through the inner rotor 7 in the axial direction. The rotation shaft 1 is inserted into the axial hole 11 so as to have a portion protruding from the inner rotor 7 to one side (left side in FIG. 3) in the axial direction, and a portion protruding from the inner rotor 7 to the other side (right side in FIG. 3) in the axial direction. The portion, of the rotation shaft 1, protruding to one side in the axial direction of the inner rotor 7 is rotatably supported by a first bearing 16a mounted to the first cover body 4a, and the portion, of the rotation shaft 1, protruding to the other side in the axial direction from the inner rotor 7 is rotatably supported by a second bearing 16b mounted to the second cover body 4b. The portion, of the rotation shaft 1, protruding to the other side in the axial direction from the inner rotor 7 (portion supported by the second bearing 16b) is connected to a rotation driving device (electric motor or the like) which is not shown.

As shown in FIG. 5, the first cover body 4a, the first side cover 5a, the housing body 3, the second side cover 5b, and the second cover body 4b are fixed to each other while being fastened in the axial direction by a common bolt 18 inserted through bolt insertion holes 17 formed in the respective components. Moreover, the first cover body 4a, the first side cover 5a, the housing body 3, the second side cover 5b, and the second cover body 4b are positioned in a direction perpendicular to the axial direction by a common knock pin 20 being inserted through knock-pin insertion holes 19 formed in the respective components.

The housing body 3 has: an opening 10 that is opened at one side (left side in FIG. 5) and the other side (right side in FIG. 5) in the axial direction; a flat first flange surface 21a formed around the one side in the axial direction of the opening 10; and a flat second flange surface 21b formed around the other side in the axial direction of the opening 10. The first flange surface 21a and the second flange surface 21b are parallel flat surfaces facing opposite to each other in the axial direction.

The first cover body 4a is disposed so as to oppose the first flange surface 21a of the housing body 3, and the first side cover 5a is sandwiched between the first cover body 4a and the housing body 3. Likewise, the second cover body 4b is disposed so as to oppose the second flange surface 21b of the housing body 3, and the second side cover 5b is sandwiched between the second cover body 4b and the housing body 3.

The first flange surface 21a is flush with the first inner rotor side surface 14a and the first outer rotor side surface 15a. The second flange surface 21b is flush with the second inner rotor side surface 14b and the second outer rotor side surface 15b. A width dimension in the axial direction of the inner rotor 7 and the outer rotor 9 is slightly smaller than a width dimension in the axial direction of the housing body 3, and a difference therebetween is set to be not larger than 20 μm (preferably, not larger than 15 μm, and more preferably, not larger than 10 μm).

The first side cover 5a and the second side cover 5b are symmetrical with each other across the housing body 3. Therefore, only the first side cover 5a will be described, and description of the second side cover 5b will be omitted while the corresponding components are denoted by the same reference signs or reference signs having the alphabetical suffix “b” instead of “a”.

The first side cover 5a is a plate-shaped member having a uniform thickness not larger than 5 mm (preferably, not larger than 4 mm). The first side cover 5a is formed of a crosslinked fluororesin 24 and a metal body 25. As a material of the metal body 25, steel or an aluminum alloy can be adopted. The metal body 25 includes: the mating surface 22 formed of a metal; and a recess 26 obtained by recessing an area corresponding to the sliding/guiding surface 23, in the axial direction with respect to the mating surface 22. The recess 26 is a flat recess having a uniform depth throughout. The depth of the recess 26 can be set to be not larger than 0.5 mm (preferably, not larger than 0.3 mm, and more preferably, not larger than 0.2 mm). The recess 26 has a contour within which a contour of the opening 10 of the housing body 3 is included (in FIG. 5, a circular contour having a larger diameter than a circle forming the contour of the opening 10). The recess 26 is filled with the crosslinked fluororesin 24, and the crosslinked fluororesin 24 forms the sliding/guiding surface 23 that is flush with the mating surface 22. The mating surface 22 and the sliding/guiding surface 23 are a contiguous machined surface having a surface roughness not greater than a ten-point average roughness Rz_JISof 6.3 μm (preferably, not greater than Rz_JISof 3.2 μm).

The ten-point average roughness Rz_JISis a parameter defined in “Appendix JA (reference) for ten-point average roughness” of Japanese Industrial Standard JISB0601:2013 “Geometrical Product Specifications (GPS)—Surface texture: Profile method—Terms, definitions and surface texture parameters”. The ten-point average roughness Rz_JISis defined as follows. That is, a reference length is extracted from a roughness curve in a direction of an average line thereof, and, in the extracted portion, a sum of an average height of five profile peaks from the highest one and an average depth of five profile valleys from the deepest one is calculated as the ten-point average roughness Rz_JIS.

The crosslinked fluororesin 24 is obtained by crosslinking molecules of chain polymers forming a fluororesin. The crosslinked fluororesin has extremely high wear resistance as compared to general fluororesin (non-crosslinked fluororesin) while having a coefficient of friction as low as that of general fluororesin.

As a fluororesin to be crosslinked, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or the like can be adopted. It is preferable to adopt crosslinked PTFE as the crosslinked fluororesin 24. When the crosslinked PTFE is adopted, pump efficiency can be effectively improved because the crosslinked PTFE has a particularly low coefficient of friction among the above fluororesins and is excellent in wear resistance, and therefore, is hardly worn.

The first side cover 5a can be formed as follows, for example.

As shown in an upper portion of FIG. 7, first, a recess 26 is formed at a surface of a plate-shaped metal body 25 having a uniform thickness. Next, as shown in an intermediate portion of FIG. 7, a coating of the crosslinked fluororesin 24 is formed at the surface, of the metal body 25, on the recess 26 side. At this time, the recess 26 is filled with the crosslinked fluororesin 24, and the periphery of the recess 26 is covered with the crosslinked fluororesin 24. Thereafter, as shown in a lower portion of FIG. 7, the crosslinked fluororesin 24 is ground until the metal around the recess 26 is exposed. Furthermore, the metal around the recess 26 and the crosslinked fluororesin 24 in the recess 26 are ground. The surface of the metal around the recess 26 corresponds to the mating surface 22, and the surface of the crosslinked fluororesin 24 in the recess 26 corresponds to the sliding/guiding surface 23. The mating surface 22 and the sliding/guiding surface 23 formed as described above are a contiguous machined surface having the same surface roughness.

The coating of the crosslinked fluororesin 24 shown in the intermediate portion of FIG. 7 can be formed as follows, for example. First, a dispersion liquid obtained by dispersing fine particles of a fluororesin (e.g., PTFE) in water is applied to the surface, of the metal body 25, on the recess 26 side. Next, the applied dispersion liquid is dried to form a layer of the tine particles of the fluororesin on the surface, of the metal body 25, on the recess 26 side, Subsequently, the metal body 25 and the layer of the fine particles of the fluororesin are heated to a temperature equal to or higher than the melting point of the fluororesin to bake the fine particles of the fluororesin, whereby the fine particles of the fluororesin are fused to each other. Thereafter, radiation e.g., electron beam) is applied under a predetermined high-temperature, oxygen-free atmosphere to cause covalent bonding between the chain polymers forming the fluororesin, thereby crosslinking the molecules of the chain polymers. The radiation applied at this time also causes chemical bonding between the surface of the metal body 25 and the molecules of the chain polymers forming the fluororesin, and the chemical bonding causes the coating of the crosslinked fluororesin 24 to be adhered to the metal body 25 with extremely high adhesion. Thus, the coating of the crosslinked fluororesin 24 shown in the intermediate portion of FIG. 7 is formed.

As shown in FIG. 6, the first side cover 5a is provided with: a first suction port 30a opened at a surface opposing the first inner rotor side surface 14a and the first outer rotor side surface 15a; and a first discharge port 31a opened at a distance in the circumferential direction from the first suction port 30a.

Likewise, the second side cover 5b is provided with: a second suction port 30b opened at a surface opposing the second inner rotor side surface 141) and the second outer rotor side surface 15b; and a second discharge port 31b opened at a distance in the circumferential direction from the second suction port 30b.

As shown in FIG. 1, each of the first suction port 30a and the first discharge port 31a is opened in an arc shape centered around the rotation shaft 1. Likewise, each of the second suction port 30b and the second discharge port 31b is opened in an arc shape centered around the rotation shaft 1.

The first suction port 30a and the second suction port 30b are opened in the same shape at symmetrical positions with the inner rotor 7 and the outer rotor 9 sandwiched therebetween. Thus, a pressure that the first inner rotor side surface 14a and the first outer rotor side surface 15a receive from the fluid in the first suction port 30a is balanced with a pressure that the second inner rotor side surface 14b and the second outer rotor side surface 15b receive from the fluid in the second suction port 30b, thereby preventing the inner rotor 7 and the outer rotor 9 from being inclined.

Likewise, the first discharge port 31a and the second discharge port 31b are opened in the same shape at symmetrical positions with the inner rotor 7 and the outer rotor 9 sandwiched therebetween. Thus, a pressure that the first inner rotor side surface 14a and the first outer rotor side surface 15a receive from the fluid in the first discharge port 31a is balanced with a pressure that the second inner rotor side surface 14b and the second outer rotor side surface 15b receive from the fluid in the second discharge port 31b, thereby preventing the inner rotor 7 and the outer rotor 9 from being inclined.

As shown in FIG. 4 and FIG. 6, the first suction port 30a and the second suction port 30b are in communication with each other via a communication path 32 formed at a position spaced apart from the opening 10, of the housing body 3, which houses the pump rotor 2. As shown in FIG. 2 and FIG. 6, the first suction port 30a is in communication with a suction port 33 opened at an outer surface of the first cover body 4a, and the first discharge port 31a is in communication with a discharge port 34 opened at an outer surface of the first cover body 4a.

As shown in FIG. 5, in the aforementioned rotary pump, the sliding/guiding surfaces 23 of the first side cover 5a. and the second side cover 5b are formed of the crosslinked fluororesin 24. Therefore, even when a clearance between the pump rotor 2 and each of the first side cover 5a and the second side cover 5b (i.e., a difference between an inner width dimension between the sliding guiding surface 23 of the first side cover 5a and the sliding/guiding surface 23 of the second side cover 5b, and a width dimension in the axial direction of the inner rotor 7 or the outer rotor 9) is set to an extremely small size (not larger than 20 μm, preferably, not larger than 15 μm, and more preferably, not larder than 10 μm), seizure between the pump rotor 2, and the first side cover 5a and the second side cover 5b can be avoided over a long period of time.

Moreover, in this rotary pump, when the first side cover 5a and the second side cover 5b are fixed to the housing body 3 by the bolt 18, positional shift of the sliding/guiding surfaces 23 due to fastening of the bolt 18 hardly occurs. Thus, the clearance in the axial direction between the pump rotor 2 (the inner rotor 7 or the outer rotor 9) and each of the first side cover 5a and the second side cover 5b can be accurately controlled.

It is assumed that each of the first side cover 5a and the second side cover 5b shown in FIG. 5 is replaced with a side cover in which the entirety of one surface of the metal body 25 (i.e., the entirety of a contiguous fiat surface, of the metal body 25 having no recess 26, which includes the mating surface 22 to the housing body 3 and the sliding/guiding surface 23 for the pump rotor 2) is coated with crosslinked fluororesin. In this case, when the side cover is fixed to the housing body 3 by the bolt 18, the coating of the crosslinked fluororesin formed on the mating surface 22, of the side cover, to the housing body 3 is compressed and deformed by fastening force of the bolt 18, and the compressive deformation causes the thickness of the crosslinked fluororesin coating to be reduced by about 1 μm to about 10 μm, whereby the position of the sliding/guiding surface 23 of the side cover is slightly shifted in the axial direction. For example, in a case where four bolts 18 are fastened each by a torque of 11 Nm, a 50 μm thick crosslinked fluororesin coating is reduced in thickness by about 1.6 μm, a 150 μm thick crosslinked fluororesin coating is reduced in thickness by about 4.8 μm, and a 250 μm thick crosslinked fluororesin coating is reduced in thickness by about 8.0 μm due to compressive deformation caused by fastening force of the bolts 18. As a result, a clearance in the axial direction between the side cover and the pump rotor 2 becomes slightly smaller than a design value, which may cause a problem that, particularly when the clearance is set to an extremely small size not larger than 20 μm, a torque for rotationally driving the pump rotor 2 becomes larger than expected.

Regarding the above problem, in the rotary pump according to the embodiment of the present disclosure, the mating surfaces 22, to the housing body 3, of the first side cover 5a and the second side cover 5b are formed on the metal bodies 25 of the first side cover 5a and the second side cover 5b. Therefore, the fastening force of the bolt 18 can be supported with rigidity by the metal bodies 25, thereby preventing the positions of the sliding/guiding surfaces 23 of the first side cover 5a and the second side cover 5b from being shifted in the axial direction due to the fastening force of the bolt 18. Therefore, when the first side cover 5a and the second side cover 5b are fixed to the housing body 3 by the bolt 18, the clearance in the axial direction between the pump rotor 2 and each of the first side cover 5a and the second side cover 5b can be accurately controlled.

Moreover, the rotary pump according to the embodiment can be obtained by additionally incorporating the first side cover 5a and the second side cover 5b into an existing rotary pump, which realizes cost reduction.

Moreover, in this rotary pump, since the recess 26 to be filled with the crosslinked fluororesin 24 is formed not in the first cover body 4a to which the first bearing 16a is mounted but in the metal body 25 which is a member separate from the first cover body 4a, machining of the recess 26 and filling of the recess 26 with the crosslinked fluororesin 24 are facilitated as compared to the case where the recess 26 is directly formed at the surface of the first cover body 4a and filled with the crosslinked fluororesin 24. Likewise, since the recess 26 to be filled with the crosslinked fluororesin 24 is formed not in the second cover body 4b to which the second bearing 16b is mounted but in the metal body 25 which is a member separate from the second cover body 4b, machining of the recess 26 and filling of the recess 26 with the crosslinked fluororesin 24 are facilitated as compared to the case where the recess 26 is directly formed at the surface of the second cover body 4b and filled with the crosslinked fluororesin 24.

Moreover, in the rotary pump, since the mating surface 22 and the sliding/guiding surface 23 are simultaneously subjected to finish machining, the mating surface 22 and the sliding/guiding surface 23 are formed as a contiguous machined surface having a surface roughness not greater than a ten-point average roughness Rz_JISof 6.3 μm (preferably, not greater than Rz_JISof 3.2 μm), which realizes cost reduction. Since the surface roughness of the mating surface 22 and the sliding/guiding surface 23 is not larger than Rz_JISof 6.3 μm (preferably, not larger than Rz_JISof 3.2 μm), a clearance between the pump rotor 2 and each of the first side cover 5a and the second side cover 5b (i.e., a difference between the inner width dimension between the sliding/guiding surface 23 of the first side cover 5a and the sliding/guiding surface 23 of the second side cover 5b, and the width dimension in the axial direction of the inner rotor 7 or the outer rotor 9) can be controlled with extreme accuracy.

FIG. 8 and FIG. 9 show a rotary pump according to a second embodiment of the present disclosure. The second embodiment is different from the first embodiment only in the configurations of the first side cover 5a and the second side cover 5b, and the other components are the same as those of the first embodiment. Therefore, the parts corresponding to those of the first embodiment are denoted by the same reference signs, and description thereof is omitted.

The first side cover 5a has: a flat mating surface 22 that is fixed while being pressed against the first flange surface 21a by fastening of the bolt 18; and a flat sliding/guiding surface 23 that slides and guides the first inner rotor side surface 14a and the first outer rotor side surface 15a, The metal body 25 includes: the mating surface 22 formed of a metal; and a recess 26 obtained by recessing an area corresponding to the sliding/guiding surface 23, in the axial direction with respect to the mating surface 22. The recess 26 has a shape obtained by recessing, in the axial direction, also an area corresponding to a part of the mating surface 22 such that the crosslinked fluororesin 24 filled in the recess 26 is in contact with the first flange surface 21a in an annular area contiguous, without a break, around the opening 10 of the housing body 3. That is, the first side cover 5a is formed such that a part of the mating surface 22 (a part surrounding the periphery of the bolt insertion hole) is formed on the metal body 25 while a remaining portion of the mating surface 22 is formed of the crosslinked fluororesin 24 filled in the recess 26. The second side cover 5b is configured similarly to the first side cover 5a.

In this rotary pump, since the crosslinked fluororesin 24 filled in the recess 26 is in contact with the first flange surface 21a and the second flange surface 21b in the annular area contiguous, without a break, around the opening 10 of the housing body 3, the contact surfaces of the first side cover 5a and the second side cover 5b with the housing body 3 can be sealed with the crosslinked fluororesin 24, thereby avoiding leakage of fluid. Moreover, since the crosslinked fluororesin 24 forming the mating surface 22 is contiguous with the crosslinked fluororesin 24 forming the sliding/guiding surface 23, production cost can be suppressed.

FIG. 10 and FIG. 11 show a rotary pump according to a third embodiment of the present disclosure. The parts corresponding to those of the aforementioned embodiments are denoted by the same reference signs, and description thereof is omitted.

The rotary pump includes: a pump rotor 2 rotationally driven by a rotation shaft 1; a housing body 3 that houses the pump rotor 2; a first cover body 4a disposed on one side (left side in FIG. 11) in the axial direction of the housing body 3; and a second cover body 4b disposed on the other side (right side in FIG. 11) in the axial direction of the housing body 3.

As shown in FIG. 11, the first cover body 4a, the housing body 3, and the second cover body 4b are fixed to each other while being fastened in the axial direction by a common bolt 18 inserted through bolt insertion holes 17 formed in the respective components. Moreover, the first cover body 4a, the housing body 3, and the second cover body 4b are positioned in the direction perpendicular to the axial direction by a common knock pin 20 inserted through knock-pin insertion holes 19 formed in the respective components.

The first cover body 4a has: a flat mating surface 22 that is fixed while being pressed against the first flange surface 21a by fastening of the bolt 18; and a flat sliding/guiding surface 23 that slides and guides the first inner rotor side surface 14a and the first outer rotor side surface 15a.

The first cover body 4a is formed of a crosslinked fluororesin 24 and a metal body 25. As a material of the metal body 25, steel or an aluminum alloy can be adopted. The metal body 25 includes: the mating surface 22 formed of a metal; and a recess 26 obtained by recessing an area corresponding to the sliding/guiding surface 23, in the axial direction with respect to the mating surface 22. The recess 26 is filled with the crosslinked fluororesin 24, and the crosslinked fluororesin 24 also forms the sliding/guiding surface 23 that is flush with the mating surface 22. The second cover body 4b is configured similarly to the first cover body 4a.

In this rotary pump, as in the aforementioned embodiments, the sliding/guiding surfaces 23 of the first cover body 4a and the second cover body 4b are formed of the crosslinked fluororesin 24. Therefore, when a clearance between the pump rotor 2 and each of the first cover body 4a and the second cover body 4b (i.e., a difference between the inner width dimension between the sliding/guiding surface 23 of the first cover body 4a and the sliding/guiding surface 23 of the second cover body 4b, and the width dimension in the axial direction of the inner rotor 7 or the outer rotor 9) is set to an extremely small size (not larger than 20 μm, preferably, not larger than 15 μm, and more preferably, not larger than 10 μm), seizure between the pump rotor 2, and the first cover body 4a and the second cover body 4b can be avoided over a long period of time.

Moreover, in this rotary pump, the mating surfaces 22, to the housing body 3, of the first cover body 4a and the second cover body 4b are formed on the metal bodies 25 of the first cover body 4a and the second cover body 4b. Therefore, the fastening force of the bolt 18 can be supported with rigidity by the metal bodies 25, thereby preventing the positions of the sliding/guiding surfaces 23 of the first cover body 4a and the second cover body 4b from being shifted in the axial direction due to the fastening force of the bolt 18. Therefore, when the first cover body 4a and the second cover body 4b are fixed to the housing body 3 by the bolt 18, the clearance in the axial direction between the pump rotor 2 and each of the first cover body 4a and the second cover body 4b can be accurately controlled.

FIG. 12 to FIG. 14 show a rotary pump according to a fourth embodiment of the present disclosure. The fourth embodiment is different from the first embodiment only in the configuration of the pump rotor 2, and the other components are the same as those of the first embodiment. Therefore, the parts corresponding to those of the first embodiment are denoted by the same reference signs, and description thereof is omitted.

As shown in FIG. 12 and FIG. 13. the pump rotor 2 is composed of: a rotor body 36 having, at an outer periphery thereof, a plurality of vane-containing grooves 35; and a plurality of vanes 37 contained in the respective vane-containing grooves 35 so as to be slidable in the radial direction. A radially outer end of each vane 37 is slidably in contact with an inner periphery of a cam ring 38 disposed on the housing body 3. An opening 10 that rotatably houses the pump rotor 2 is formed inside the cam ring 38. A plurality of chambers 39 (spaces for containing fluid) demarcated by the vanes 37 are formed between the outer periphery of the rotor body 36 and the inner periphery of the cam ring 38. The inner periphery of the cam ring 38 is configured such that the volume of each chamber 39 changes with rotation of the rotor body 36, and a fluid discharge effect is caused by reduction in the volume of the chamber 39 while a fluid suction effect is caused by gradual increase in the volume of the chamber 39.

As shown in FIG. 14, the first side cover 5a has: a flat mating surface 22 that is fixed while being pressed against the first flange surface 21a by fastening of a bolt 18 (see FIG. 12); and a flat sliding/guiding surface 23 that slides and guides flat side surfaces, facing in the axial direction, of the rotor body 36 and the vanes 37. The second side cover 5b is configured similarly to the first side cover 5a.

The inner periphery of the cam ring 38 is coated with a crosslinked fluororesin coating 40. A width dimension in the axial direction of the rotor body 36 is equal to a width dimension in the axial direction of each vane 37.

In this rotary pump, as shown in FIG. 12, the sliding/guiding surfaces 23 of the first side cover 5a and the second side cover 5b are formed of the crosslinked fluororesin 24. Therefore, even when a clearance between the pump rotor 2 and each of the first side cover 5a and the second side cover 5b (i.e., a difference between the inner width dimension between the sliding/guiding surface 23 of the first side cover 5a and the sliding/guiding surface 23 of the second side cover 5b, and the width dimension in the axial direction of the rotor body 36 and each vane 37) is set to an extremely small size (not larger than 20 μm, preferably, not larger than 15 μm, and more preferably, not larger than 10 μm), seizure between the pump rotor 2, and the first side cover 5a and the second side cover 5b can be avoided over a long period of time.

Moreover, in this rotary pump. the mating surfaces 22, to the housing body 3, of the first side cover 5a and the second side cover 5b are formed on the metal bodies 25 of the first side cover 5a and the second side cover 5b. Therefore, the fastening force of the bolt 18 can be supported with rigidity by the metal bodies 25, thereby preventing the positions of the sliding/guiding surfaces 23 of the first side cover 5a and the second side cover 5b from being shifted in the axial direction due to the fastening force of the bolt 18. Therefore, when the first side cover 5a and the second side cover 5b are fixed to the housing body 3 by the bolt 18, the clearance in the axial direction between the pump rotor 2 and each of the first side cover 5a and the second side cover 5b can be accurately controlled.

REFERENCE SIGNS LIST

1 rotation shaft

2 pump rotor

3 housing body

4
a first cover body

4
b second cover body

5
a first side cover

5
b second side cover

6 outer teeth

7 inner rotor

8 inner teeth

9 outer rotor

10 opening

11 axial hole

12 outer peripheral cylindrical surface

13 chamber

14
a first inner rotor side surface

14
b second inner rotor side surface

15
a first outer rotor side surface

15
b second outer rotor side surface

16
a first bearing

16
b second bearing

17 bolt insertion hole

18 bolt

19 knock pin insertion hole

20 knock pin

21
a first flange surface

21
b second flange surface

22 mating surface

23 sliding/guiding surface

24 crosslinked fluororesin

25 metal body

26 recess

30
a first suction port

30
b second suction port

31
a first discharge port

31
b second discharge port

32 communication path

33 suction port

34 discharge port

35 vane-containing groove

36 rotor body

37 vane

38 cam ring

39 chamber

40 crosslinked fluororesin coating

ROTARY PUMP

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CPC

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