JP6329411B2 - Internal gear pump - Google Patents

Description

  The present invention relates to an internal gear pump (trochoid pump) that pumps a liquid such as oil, water, or a chemical solution.

  An internal gear pump (trochoid pump) contains an outer rotor and an inner rotor having a trochoidal tooth shape sealed in a casing, and an inner rotor and an outer rotor fixed to the drive shaft rotate as the drive shaft rotates. It is a pump which acts to inhale and discharge. For example, Patent Document 1 has been proposed as this type of pump.

  An example of a conventional internal gear pump is shown based on FIGS. 7 is an assembled perspective view of a conventional internal gear pump, FIG. 8 (a) is a cross-sectional view of the internal gear pump of FIG. 7, and FIG. 8 (b) is a cross-sectional view of another form of internal gear pump. Respectively. As shown in FIG. 7, the pump 21 is mainly composed of a trochoid 24 in which an inner rotor 23 having a plurality of external teeth is accommodated in an annular outer rotor 22 having a plurality of internal teeth. The trochoid 24 is rotatably accommodated in a circular trochoid accommodating recess 25a formed in a cylindrical casing 25 with a flange. A cover 26 that closes the trochoid-containing recess 25 a is fixed to the casing 25. As shown in FIG. 8A, the casing 25 and the cover 26 are fastened and fixed to a fixing plate 28 of the apparatus main body by a fixing screw 30. The mating surface of the casing 25 and the cover 26 is a machined surface and is surface-sealed.

  The trochoid 24 is configured such that the inner rotor 23 is rotatably accommodated in the outer rotor 22 with the outer teeth of the inner rotor 23 meshing with the inner teeth of the outer rotor 22 and is eccentric. Between the partition points where the rotors contact each other, the suction-side and discharge-side volume chambers are formed according to the rotational direction of the trochoid 24. A drive shaft 31 (not shown in FIG. 7) that is rotated by a drive source such as a motor (not shown) is fixed through the shaft center of the inner rotor 23. A bearing 32 is press-fitted into the cover 26 and supports the drive shaft 31. When the drive shaft 31 rotates and the inner rotor 23 rotates, the outer teeth mesh with the inner teeth of the outer rotor 22 so that the outer rotor 22 rotates in the same direction. Liquid is sucked into the chamber from the inlet. The suction-side volume chamber is changed to a discharge-side volume chamber in which the volume is reduced and the internal pressure is increased by the rotation of the trochoid 24, from which the sucked liquid is discharged to the discharge port.

  A liquid suction nozzle 27 extending from the casing 25 is provided at the suction port communicating with the suction side volume chamber (FIG. 8B). A metal or resin mesh filter 29 for removing foreign matter in the sucked liquid is attached to an arbitrary position of the liquid suction path including the nozzle 27 to the suction side volume chamber. The mesh filter 29 is physically fixed by spot welding or a C ring. Further, the mesh filter 29 and the liquid suction nozzle 27 are attached with rubber seals interposed therebetween while ensuring sealing performance.

  As the bearing 32, a sliding bearing such as a rolling bearing, a metal bush (alloy such as copper, tin, lead) or a polytetrafluoroethylene (hereinafter referred to as PTFE) resin-wound bush can be used. Of these, inexpensive sliding bearings are frequently used.

Patent No. 4215160

  In the case of an internal gear pump that aims to send lubricating oil to a sliding part such as a sliding bearing that supports a compression part or a drive shaft, like a scroll compressor, the lubrication state of the sliding part is higher than that of high-speed rotation. However, since the oil film is less likely to be formed in the low-speed rotation, it is designed to ensure the necessary discharge flow rate in the low-speed rotation. In the internal gear pump, the flow rate of the liquid to be discharged with the rotation of the drive shaft is almost proportional to the rotation speed. Therefore, due to the above design, the flow rate increases at high speed rotation and the oil is excessively supplied. On the contrary, it is not preferable in terms of efficiency.

  The present invention has been made to cope with such problems, and an object of the present invention is to provide an internal gear pump that suppresses the liquid discharge flow rate when the drive shaft rotates at a high speed.

  In the internal gear pump of the present invention, an inner rotor having a plurality of external teeth is rotatably accommodated in an outer rotor having a plurality of internal teeth in a state where the external teeth mesh with the internal teeth and are eccentric. An internal gear pump having a trochoid in which a suction side volume chamber for sucking liquid and a discharge side volume chamber for discharging liquid sucked into the suction side volume chamber are formed between the inner teeth and the outer teeth And having a drive shaft fixed to the inner rotor, a casing formed with a recess for accommodating the trochoid, and a cover for closing the recess of the casing, and at least selected from the cover and the casing One member has a slide bearing that rotatably supports the drive shaft, and a sliding portion between the drive shaft and the slide bearing is provided in the trochoid housing space (simply And having a liquid discharge groove for discharging part of the liquid in the pump interior, "also referred to).

  The slide bearing has a radial slide bearing that supports an outer peripheral surface of the drive shaft, and the liquid discharge groove is at least one of the outer peripheral surface of the drive shaft and the inner peripheral surface of the radial slide bearing. It is characterized by being formed. Further, the liquid discharge groove on the radial sliding surface is a groove communicating with both axial ends of the sliding surface.

  The sliding bearing includes a thrust sliding bearing that supports an end surface of the drive shaft, and the liquid discharge groove is formed on at least one thrust sliding surface of the driving shaft and the bearing surface of the thrust sliding bearing. It is characterized by being. The liquid sliding groove on the thrust sliding surface is a groove communicating with the inner and outer diameters of the sliding surface.

  The drive shaft is inserted and fixed to the inner rotor, and a through groove that penetrates the fixed portion in the axial direction is formed in a fixed portion between the drive shaft and the inner rotor.

  The internal gear pump is a pump for supplying the liquid to the sliding portion of the scroll compressor.

  The internal gear pump of the present invention has a sliding bearing in which at least one member of a casing in which a recess for accommodating a trochoid is formed and a cover for closing the recess of the casing rotatably supports a drive shaft, Since the liquid discharge groove is provided in the sliding portion between the drive shaft and the slide bearing, a part of the liquid inside the pump can be discharged through the liquid discharge groove during driving, and excessive supply of liquid during high-speed rotation can be suppressed. Further, when the drive shaft rotates, the liquid discharge groove generates a force for sucking the liquid, and the slope of the discharge flow rate with respect to the rotation speed can be made gentle. Further, since a large amount of liquid is also supplied to the bearing sliding surface, low friction and low wear characteristics can be obtained by improving the cooling effect of the sliding surface and the lubrication state.

  The liquid discharge groove on the radial sliding surface is a groove communicating with both axial ends of the sliding surface, and the liquid discharge groove on the thrust sliding surface is a groove communicating the inner and outer diameters of the sliding surface. Therefore, the liquid discharge performance is excellent, and the above effect is further improved.

  The drive shaft is inserted and fixed to the inner rotor, and a through groove is formed in the fixed portion between the drive shaft and the inner rotor so as to penetrate the fixed portion in the axial direction. It becomes the flow path which discharges.

  With the above specifications, the internal gear pump of the present invention can be suitably used as a pump for supplying liquid to the sliding portion of the scroll compressor for an air conditioner.

It is an axial sectional view showing an example of the internal gear pump of the present invention. It is a figure which shows the liquid discharge groove | channel formed in the radial sliding surface. It is a figure which shows the cross-sectional shape of a liquid discharge groove | channel. It is a figure which shows the liquid discharge groove | channel formed in the thrust sliding surface. It is a figure which shows the through-groove formed in the inner periphery of an inner rotor. It is a conceptual diagram which shows the relationship between rotation speed and discharge flow volume. It is an assembly perspective view of the conventional internal gear pump. It is an axial sectional view of a conventional internal gear pump.

  One embodiment of the internal gear pump of the present invention will be described with reference to FIG. FIG. 1 is an axial sectional view of an internal gear pump used in a scroll compressor. As shown in FIG. 1, the internal gear pump 1 includes a trochoid 4 in which an inner rotor 3 is accommodated in an annular outer rotor 2, and a circular recess (trochoid accommodating recess) 5a in which the trochoid 4 is rotatably accommodated. And a cover 6 that closes the trochoid-receiving recess 5a of the casing 5. The cover 6 has a shape that matches the outer shape of the upper surface of the casing 5 in which the trochoid-containing recess 5a is opened. The casing 5 and the cover 6 are fastened and fixed to a fixing plate 10 of the apparatus main body by fixing screws 8. In addition, the drive shaft 9 is coaxially fixed to the rotation center of the inner rotor 3.

  The outer teeth of the inner rotor 3 are one less than the inner teeth of the outer rotor 2, and the inner rotor 3 is housed in the outer rotor 2 in an eccentric state in which the outer teeth are inscribed and meshed with the inner teeth. Between the partition points where the rotors are in contact with each other, the suction-side and discharge-side volume chambers are formed according to the rotational direction of the trochoid 4. A suction port communicating with the volume chamber on the suction side is formed on the bottom surface 5 b of the trochoid-accommodating recess 5 a of the casing 5. From the discharge port communicating with the discharge-side volume chamber at the lower part of the rotor, the liquid is pumped to the upper compression portion (not shown) in the drawing through the discharge passage 9a in the center of the drive shaft 9 (two-dot chain line in the drawing). Arrow).

  In the internal gear pump 1, the trochoid 4 is rotated by the drive shaft 9, whereby liquid is sucked into the pump from the suction port into the suction-side volume chamber where the volume increases and becomes negative pressure. The suction-side volume chamber changes to a discharge-side volume chamber in which the volume decreases and the internal pressure increases as the trochoid 4 rotates, and the sucked liquid is discharged from the discharge-side volume chamber to the discharge port. The above pumping action is continuously performed by the rotation of the trochoid 4, and the liquid is continuously pumped. Furthermore, due to the liquid sealing effect in which the sealing performance of each volume chamber is enhanced by the sucked liquid, the differential pressure generated between the volume chambers is increased, and a large pumping action is obtained.

  The drive shaft 9 is rotatably supported by a radial slide bearing 11 and a thrust slide bearing 12 provided on the cover 6. A cylindrical radial sliding bearing 11 receives a radial load of the drive shaft 9, and a disc-shaped thrust sliding bearing 12 receives a thrust load of the driving shaft 9. The drive shaft 9 is a stepped shaft having a main body portion 9 b and a tip portion 9 c having a smaller diameter than the main body portion 9 b, and the tip portion 9 c is fixed to the inner rotor 3. The radial plain bearing 11 rotatably supports the outer peripheral surface of the tip end portion 9c of the drive shaft 9 on its inner peripheral surface. The thrust slide bearing 12 supports the end surface of the main body portion 9b of the drive shaft 9 with its bearing surface (disk surface on the drive shaft side). In FIG. 1, the cover 6 is provided with the sliding bearing, but may be provided on the casing 5. Further, the cover and the casing may be used as a slide bearing as they are. In FIG. 1, both the radial sliding bearing and the thrust sliding bearing are provided, but only one of them may be provided.

  The internal gear pump 1 has a liquid discharge groove for discharging a part of the liquid in the trochoid accommodating space at a sliding portion between the drive shaft 9 and the slide bearings 11 and 12. A part of the liquid in the trochoid accommodating space (inside the pump) can be discharged to the outside of the space through the liquid discharge groove during driving (the dashed line arrow in the figure). The sliding portion is a radial sliding portion between the driving shaft 9 and the radial sliding bearing 11 and a thrust sliding portion between the driving shaft 9 and the thrust sliding bearing 12, and either one or both of these sliding portions are used. Forming the liquid discharge groove. Since it is excellent in the liquid discharge effect, it is preferable to form both. Note that a small amount of liquid is also present on the sliding surface even in the sliding portion where the liquid discharge groove is not formed.

  As a radial sliding bearing 11, if a liquid discharge groove can be formed on the sliding surface (inner peripheral surface), a metal bush (alloy such as copper, tin, lead), a sintered bearing (iron, copper-based, etc.), A sliding bearing of any material such as a polytetrafluoroethylene resin-wound bush, a polyether ether ketone resin or a polyphenylene sulfide resin resin bearing can be used. Further, as the thrust slide bearing 12, a slide bearing made of the same material as the radial slide bearing described above can be used. Each plain bearing is fixed by press fitting or the like.

  When the liquid discharge groove is formed in the radial sliding portion, the groove can be formed on at least one radial sliding surface of the outer peripheral surface of the drive shaft 9 and the inner peripheral surface of the radial slide bearing 11. In FIG. 1, the radial plain bearing 11 supports the outer peripheral surface of the tip end portion 9 c of the drive shaft 9, but the radial slide bearing position is not limited to this, and supports the outer peripheral surface of the main body portion 9 b of the drive shaft 9. It is good also as a form to do. Further, when the liquid discharge groove is formed in the thrust sliding portion, the groove can be formed in at least one of the thrust sliding surfaces of the end surface of the drive shaft 9 and the bearing surface of the thrust slide bearing 12. In FIG. 1, although the end surface of the main-body part 9b of the drive shaft 9 is supported, a thrust bearing position is not limited to this.

  The shape of the liquid discharge groove formed on the radial sliding surface is not particularly limited, but it may be a groove having an action of sucking and discharging the liquid inside the pump when the drive shaft and the slide bearing rotate relative to each other. preferable. As the planar shape of the liquid discharge groove formed on the radial sliding surface, for example, as shown in FIG. 2, a linear groove (FIG. 2A) or a spiral groove (FIG. 2B) parallel to the axial direction is used. Can be mentioned. Black portions in the figure are liquid discharge grooves. In FIG. 2, the liquid discharge groove 11 a is formed on the inner peripheral surface of the radial sliding bearing 11. In particular, it is preferable to make the spiral rotation direction the same as the rotation direction of the drive shaft in the spiral groove because the liquid inside the pump is sucked and discharged to the outside when the drive shaft rotates. In addition, the liquid discharge groove on the radial sliding surface is preferably a groove that communicates (penetrates) with both axial ends of the sliding surface. By using such a communication groove, the liquid can be easily discharged, and the liquid can be discharged more smoothly.

  Since the liquid passes through the liquid discharge groove, the radial sliding surface is cooled and the liquid is supplied to the sliding surface, so that the frictional wear characteristic of the radial sliding bearing is improved. The groove width and groove depth are wide at the inlet (inner side of the pump for suction) in the liquid flow direction and narrowed at the outlet (discharge side) to generate dynamic pressure, and the liquid is pushed into the closed sliding surface. Therefore, the friction coefficient can be lowered.

  In the radial sliding bearing 11, the cross-sectional shape of the liquid discharge groove 11a formed on the radial sliding surface is, for example, a square groove (FIGS. 3A and 3D), an R groove (see FIG. 3). 3 (b)), V-groove (FIG. 3 (c)), and the like. The load capacity of the liquid film due to the dynamic pressure effect is small compared to the load applied to the radial slide bearing, and it is difficult to completely make no contact between the radial slide bearing and the drive shaft. Accordingly, the radial slide bearing and the drive shaft slide in contact with each other, and a mixed lubrication state is obtained. In this way, when the liquid film cannot be supported completely in a non-contact manner, the V-groove and the R-groove having a wedge shape (narrowed shape) in the groove cross-sectional shape are more likely to generate dynamic pressure due to the wedge effect than the square groove. V grooves and R grooves are preferable to square grooves. Furthermore, since the pressure of the liquid filled in the wedge-shaped space increases as the gap becomes smaller, a V-groove having a large area with a small gap as a cross-sectional shape is preferable to the R-groove. The angle of the V groove is not particularly limited, and the groove need not be a symmetric groove with respect to the axial rotation direction. As shown in FIG. 3 (f), the sliding surface on the side where the liquid flows into the sliding surface by rotation, It is preferable that the groove has an acute angle. The same applies to the R groove, and as shown in FIG. 3 (e), it is preferable that the inclination on the side where the liquid flows into the sliding surface by rotation is gentle. The greater the number of liquid discharge grooves, the easier it is to generate dynamic pressure, but the surface pressure of the sliding surface increases, so it may be set in consideration of the use conditions.

  The shape of the liquid discharge groove formed on the thrust sliding surface is not particularly limited, but as described above, the liquid discharge groove has a function of sucking and discharging the liquid inside the pump when the drive shaft and the slide bearing rotate relative to each other. It is preferable that As a specific planar shape of the liquid discharge groove formed on the thrust sliding surface, for example, as shown in FIG. 4, herringbone (FIGS. 4A to 4C and 4E), radial (FIG. 4). (D)), spiral (FIG. 4 (f)) and the like. Black portions in the figure are liquid discharge grooves. In FIG. 4, a liquid discharge groove 12a is formed on the bearing surface of the thrust slide bearing 12 (the disk surface on the drive shaft side). Moreover, the shape which has a suction effect | action may be sufficient by complicating a flow path. In any of the shapes, the liquid inside the pump is sucked from the gap between the inner diameter surface and the outer peripheral surface of the drive shaft and introduced into the thrust sliding surface according to the shape shown in the figure and the bearing rotation direction. Can be pumped. The liquid can be discharged to the outside directly from the outer diameter side or through a liquid discharge groove of a radial sliding bearing depending on the bearing type of the pump. These shapes may be used alone or in combination. As the planar shape, a spiral capable of generating dynamic pressure and smoothly discharging liquid is preferable. The liquid discharge groove on the thrust sliding surface is preferably a groove that communicates (penetrates) the inner and outer diameters of the sliding surface. By using the communication groove, the liquid can be easily discharged from the inner diameter to the outer diameter, and the liquid can be discharged more smoothly.

  The return position of the groove in the herringbone as shown in FIGS. 4A to 4C can be set as appropriate. In the shape and the bearing rotation direction shown in FIGS. 4A to 4C, the force from the inner diameter side toward the outer diameter side increases as the folding position goes to the outer circumferential side. 4 (d) and 4 (e) are such that the groove flow path from the inner diameter to the outer diameter is longer than the case where the inner diameter and the outer diameter are connected by a radial straight line or curve from the center. Forming. Specifically, a circumferential groove concentric with the disk is provided at a substantially central position in the radial direction of the disk bearing surface of the thrust slide bearing, and an inner diameter side groove from the inner diameter to the circumferential groove, and from the circumferential groove to the outer diameter. The outer diameter side groove has a shape connected to the circumferential groove at a circumferential position that does not overlap the circumferential groove. Furthermore, the connection position of the inner diameter side groove and the circumferential groove and the connection position of the outer diameter side groove and the circumferential groove are arranged alternately at substantially equal intervals in the circumferential direction.

  Since the liquid passes through the liquid discharge groove, the thrust sliding surface is cooled and the liquid is supplied to the sliding surface, so that the frictional wear characteristic of the thrust sliding bearing is improved. The groove width, groove depth, and cross-sectional shape of the groove are the same as those in the above-described radial sliding surface.

  In the internal gear pump used in the scroll compressor, as described above, the liquid sucked by the rotation of the inner rotor and the outer rotor is pumped from the lower part of the rotor to the upper part through the discharge passage in the center of the drive shaft. At this time, since the gap between the inner rotor and the drive shaft is small, a large amount of liquid cannot pass during high-speed rotation. Therefore, it is preferable to form a through-groove that penetrates the fixed portion in the axial direction in the fixed portion between the drive shaft and the inner rotor as a flow path for sending the liquid inside the pump to the sliding surface of the slide bearing. Since the drive shaft is inserted and fixed in the central portion of the inner rotor, for example, a through groove penetrating the fixed width of both is formed in either the inner periphery of the inner rotor or the outer periphery of the drive shaft. In the example shown in FIG. 5, a through groove 3 a is formed on the inner periphery (drive shaft fixed side) of the inner rotor 3. The through groove 3a is a groove penetrating along the axial direction from the upper surface to the lower surface of the inner rotor, and its axial length is equal to the axial thickness of the inner rotor.

  In the internal gear pump of the present invention, the cover and casing are made of metal (iron, stainless steel, sintered metal, aluminum alloy, etc.), resin (polyphenylene sulfide resin, polybutylene terephthalate resin, and resin in which a filler is blended). Composition etc.) can be used, and the composite molded article of a metal and resin may be sufficient. In addition, it is preferable to use a sintered metal (iron-based, copper-iron-based, copper-based, stainless-based, etc.) for the outer rotor and inner rotor, and iron is particularly preferable from the viewpoint of price. However, a trochoid pump that pumps water, chemicals, or the like may employ a stainless steel type that has a high rust prevention capability.

  FIG. 6 is a conceptual diagram showing the relationship between the rotational speed and the discharge flow rate in the internal gear pump. A sliding bearing in an internal gear pump having a conventional structure (for example, see FIG. 8A) is lubricated by liquid leaking from the inside of the trochoid housing space through a gap around the drive shaft. Since the bearing is oil-sealed, liquid leakage to the outside is very small. In addition, internal gear pumps such as scroll compressors are designed to ensure the required discharge flow rate at low speed rotation. Therefore, with the conventional structure described above, the flow rate increases at high speed rotation, and oil is excessively supplied. It is easy to be in a state (comparative example in FIG. 6). On the other hand, in the internal gear pump of the present invention, since the liquid discharge groove is provided in the sliding portion between the slide bearing and the drive shaft, the liquid discharge groove sucks the liquid when the drive shaft rotates. A force is generated according to the rotational speed, and a part of the liquid inside the pump can be discharged to the outside through the liquid discharge groove. Thereby, the gradient of the discharge flow rate with respect to the rotation speed can be made gentle, and the excessive supply of liquid at the time of high-speed rotation can be suppressed (the embodiment of FIG. 6).

  The internal gear pump of the present invention suppresses the liquid flow rate at high speed rotation and is stable in terms of function by improving the cooling effect and lubrication state. It can be used as a contact gear pump (trochoid pump). In particular, it can be suitably used as a pump for supplying a liquid to a sliding part of a scroll compressor for electric water heaters, room air conditioners, and car air conditioners that use alternative chlorofluorocarbon or carbon dioxide as a refrigerant.

DESCRIPTION OF SYMBOLS 1 Internal gear pump 2 Outer rotor 3 Inner rotor 4 Trochoid 5 Casing 6 Cover 7 Metal filter 8 Fixing screw 9 Drive shaft 10 Fixing plate of an apparatus main body 11 Radial slide bearing 12 Thrust slide bearing

Claims (7)

An inner rotor having a plurality of external teeth is rotatably accommodated in an outer rotor having a plurality of internal teeth in a state where the external teeth mesh with the internal teeth and is eccentric. An internal gear pump having a trochoid in which a suction side volume chamber for sucking liquid and a discharge side volume chamber for discharging liquid sucked into the suction side volume chamber are formed,
A drive shaft fixed to the inner rotor, a casing formed with a recess for accommodating the trochoid, and a cover for closing the recess of the casing;
At least one member selected from the cover and the casing has a sliding bearing that rotatably supports the driving shaft, and the sliding portion between the driving shaft and the sliding bearing has the sliding space in the trochoid accommodating space. An internal gear pump comprising a liquid discharge groove for partially discharging liquid to the outside of the internal gear pump.   The slide bearing includes a radial slide bearing that supports an outer peripheral surface of the drive shaft, and the liquid discharge groove is at least one radial slide selected from an outer peripheral surface of the drive shaft and an inner peripheral surface of the radial slide bearing. The internal gear pump according to claim 1, wherein the internal gear pump is formed on a moving surface.   3. The internal gear pump according to claim 2, wherein the liquid discharge groove on the radial sliding surface is a groove communicating with both axial ends of the sliding surface. The drive shaft is a stepped shaft having a main body portion and a tip portion having a smaller diameter than the main body portion, and the tip portion is fixed to the inner rotor,
The slide bearing includes a thrust slide bearing that supports a step surface of the main body portion of the drive shaft, and the liquid discharge groove is selected from a step surface of the main body portion of the drive shaft and a bearing surface of the thrust slide bearing. 4. The internal gear pump according to claim 1, wherein the internal gear pump is formed on at least one thrust sliding surface.   5. The internal gear pump according to claim 4, wherein the liquid discharge groove on the thrust sliding surface is a groove communicating with the inner and outer diameters of the sliding surface.   2. The drive shaft is inserted and fixed to the inner rotor, and a through groove that penetrates the fixed portion in the axial direction is formed in a fixed portion between the drive shaft and the inner rotor. The internal gear pump according to claim 5.   The internal gear pump according to any one of claims 1 to 6, wherein the internal gear pump is a pump for supplying the liquid to a sliding portion of a scroll compressor.

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