External gear pump

Abstract

To provide an external gear pump capable of obtaining good lubricity between a casing and gears even when liquid to be suctioned / discharged is liquid with low lubricity, such as water.SOLUTION: A drive gear 11 and a driven gear 12 that mesh with each other and form a pair are housed rotatably in a gear housing hole 8 of a casing 1, and liquid is suctioned / discharged by rotation of both gears 11, 12. The casing 1 has a first body member 2 and a second body member 3 that come into sliding contact with both gears 11, 12 and are formed from polyphenylene sulfide resin containing glass fibers. Also, surfaces of both gears 11, 12 are coated with a DLC (Diamond-Like Carbon) coating.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an external gear pump that sucks in and discharges liquid by rotating a meshed pair of drive gears and driven gears, and in particular to an external gear pump that is suitable for sucking in and discharging liquids with low lubricity, such as water. [Background technology]

[0002] This type of external gear pump houses a drive gear and a driven gear that mesh with each other inside a casing, and sucks in liquid through a suction passage and discharges it from a discharge passage when the gears rotate. The sliding surface of the casing where the side surfaces of the gears slide is provided with a recess formed by shot blasting, and the liquid to be sucked in and discharged is guided into this recess to lubricate the space between the casing and the gears. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-169718 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in such conventional external gear pumps, lubrication is achieved by guiding the liquid to be sucked in and discharged into a recess provided on the sliding surface of the casing, so when the liquid to be sucked in and discharged is a liquid with low lubricity, such as water, it is difficult to obtain good lubrication between the casing and the gears.

[0005] An object of the present invention is to provide an external gear pump which can obtain good lubrication between the casing and the gears even when the liquid to be sucked in and discharged is a liquid with low lubricity, such as water. [Means for solving the problem]

[0006] In order to achieve this object, the present invention takes the following measures: This is an external gear pump that houses a drive gear and a driven gear that mesh with each other and form a pair of gears so that they can rotate freely inside a casing, and sucks in and discharges liquid by driving the rotation of both gears, and is characterized in that the parts of the casing that come into sliding contact with the both gears are made of resin material.

[0007] In this case, the gears may be made of a material having solid lubrication such that the parts of the gears that come into sliding contact with the casing are lubricated only by solid matter. The material having solid lubrication may be a DLC coating that covers the surfaces of the gears. Effect of the Invention

[0008] As described above in detail, in the invention described in claim 1, the portion of the casing that comes into sliding contact with both gears is made of a resin material. Therefore, since the portion of the casing that comes into sliding contact with both gears is made of a resin material and can reduce wear and adhesion, good lubrication can be obtained between the casing and the gears even if the liquid to be sucked and discharged is a liquid with low lubricity such as water.

[0009] In the invention described in claim 2, the parts of both gears that slide against the casing are made of a material with solid lubrication that is lubricated only by solids. This reduces wear on the resin material of the casing that slides against the two gears, and therefore reduces wear and adhesion of the parts of the casing that slide against the two gears, providing better lubrication between the casing and the gears. [Brief description of the drawings]

[0010] [Figure 1] FIG. 3 is a cross-sectional view of the external gear pump taken along line BB in FIG. 2, showing one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In Figures 1 and 2, 1 denotes a casing, which is made up of a first body member 2, a second body member 3, a flange member 4, and a cover member 5. The first body member 2 is made of glass fiber-reinforced polyphenylene sulfide resin (commonly known as PPS) as a resin material. 6 denotes a first through hole and 7 denotes a second through hole, both of which are formed through the first body member 2 in parallel to the axial direction and spaced apart in the radial direction. 8 denotes a gear housing hole, which is provided by forming a recess in one axial end face of the first body member 2, and has a cross section formed in a substantially figure eight shape as shown in Figure 2. Both through holes 6 and 7 open to the bottom face of the gear housing hole 8.

[0012] The second body member 3 is made of the same material as the first body member 2, that is, glass fiber-reinforced polyphenylene sulfide resin, and is formed in a plate shape, with the other axial end face of the second body member 3 joined to one axial end face of the first body member 2 to close the gear housing hole 8. The flange member 4 is made of a metal material such as an aluminum alloy, and is joined to the other axial end face opposing the one axial end face of the first body member 2 to close both through holes 6, 7. An insertion hole 9 is formed through the flange member 4 in the axial direction, and the insertion hole 9 is formed with a larger diameter than the first through hole 6 and is connected concentrically with the first through hole 6.

[0013] The cover member 5 is formed from a metal material such as carbon steel for mechanical construction, and is joined to one axial end face opposing the other axial end face of the second body member 3. Reference numeral 10 denotes four bolt members which are inserted through the second body member 3 and the first body member 2 from the outside of the cover member 5 and screwed into the flange member 4, integrally joining the first body member 2, the second body member 3, the flange member 4, and the cover member 5.

[0014] 11 is a driving gear, and 12 is a driven gear, which are identically shaped and have multiple external teeth 11A, 12A that mesh with each other on their outer circumferences, and are housed in the gear housing hole 8, with the tips of the external teeth 11A, 12A slidably contacting the inner circumferential surface of the gear housing hole 8, one axial side of the gears 11, 12 slidably contacting the other axial end surface of the second main body member 3, and the other axial side opposite to the one axial side of the gears 11, 12 slidably contacting the bottom surface of the gear housing hole 8. The surfaces of both gears 11, 12 are coated with DLC (Diamond-Like Carbon) coating, and the parts that slide against the pump housing 1 are made of a material with solid lubrication that is lubricated only by solids. As shown in FIG. 2, 13 is a suction flow passage that draws in liquid, which is formed in the first main body member 2 and connected to one radial side of the gear housing hole 8. Reference numeral 14 denotes a discharge flow path for discharging liquid. The discharge flow path is formed in the first main body member 2 and is connected to the other radial side that is symmetrical to the one radial side via the meshing point where the external teeth 11A, 12A of the two gears 11, 12 in the gear storage hole 8 mesh with each other.

[0015] Reference numeral 15 denotes a drive shaft formed from a metal material, which engages with the drive gear 11 in the direction of rotation via a key 16, passes through the first through hole 6 and the insertion hole 9 to expose its tip to the outside, and this tip is coupled to an electric motor (not shown) to rotate the drive gear 11. Reference numeral 17 denotes a bushing pressed into the first through hole 6, which slidably contacts the drive shaft 15 to rotatably support it. Reference numeral 18 denotes a seal member provided in the insertion hole 9, which slidably contacts the drive shaft 15 to seal the inside of the pump housing 1. Reference numeral 19 denotes a ball bearing provided axially outward of the seal member 18 of the insertion hole 9, which rotatably supports the drive shaft 15. The drive shaft 15 is supported by the bushing 17 and ball bearing 19 on one axial side of the drive gear 11.

[0016] Reference numeral 20 denotes a driven shaft made of a metal material, which engages with driven gear 12 in the rotational direction via a key 21 and is inserted into second through hole 7. Reference numeral 22 denotes a bushing press-fitted into second through hole 7, which slidably contacts and rotatably supports driven shaft 20. Driven shaft 20 is supported by bushing 22 on one axial side of driven gear 12.

[0017] Next, the operation of this configuration will be described. When the drive gear 11 is rotated in the direction of arrow C by the drive shaft 15, the driven gear 12 meshing with the drive gear 11 is rotated in the direction opposite to the direction of arrow C, and the liquid on the low-pressure side flows through the suction passage 13 and is sucked between the external teeth 11A of the drive gear 11 and between the external teeth 12A of the driven gear 12, transported along the inner circumference of the gear housing hole 8 to the discharge side, and then flows through the discharge passage 14 to be discharged.

[0018] In this operation, the first body member 2 and second body member 3 of the casing 1, which come into sliding contact with both gears 11, 12, are made of glass fiber-reinforced polyphenylene sulfide resin. Therefore, the parts of the casing 1 that come into sliding contact with both gears 11, 12 are made of resin, which reduces wear and adhesion, so that good lubrication can be obtained between the casing 1 and the gears 11, 12 even if the liquid being sucked in and discharged is a liquid with low lubricity, such as water.

[0019] In addition, the surfaces of both gears 11, 12 are coated with DLC (Diamond-Like Carbon) coating, and the parts that slide against the casing 1 are made of a material with solid lubricating properties that are lubricated only by solids. This reduces wear on the resin material of the casing 1 that the gears 11, 12 slide against, so that the wear and adhesion of the parts of the casing 1 that slide against the gears 11, 12 can be further reduced, and even better lubrication can be obtained between the casing 1 and the gears 11, 12.

[0020] In the above embodiment, the first body member 2 and the second body member 3 are made of polyphenylene sulfide resin (commonly known as PPS) containing glass fiber as the resin material of the portion of the casing 1 that is in sliding contact with the gears 11 and 12, but polyether ether ketone resin (commonly known as PEEK) or phenol resin may be used. The driving shaft 15 and the driven shaft 20 are supported by the bushes 17 and 22 pressed into the through holes 6 and 7, but the surfaces of the shafts 15 and 20 may be coated with DLC (Diamond-Like Carbon) coating and directly supported by the first body member 2 made of a resin material in which the through holes 6 and 7 are formed. The driving shaft 15 and the driven shaft 20 are supported on one side of the gears 11 and 12 in the axial direction, but it goes without saying that the shafts 15 and 20 may be supported by protruding from both sides of the gears 11 and 12 in the axial direction. [Explanation of symbols]

[0021] 1: Casing 2: First main body member (part that comes into sliding contact with both gears) 3: Second body member (part that comes into sliding contact with both gears) 4: Flange material 5: Lid member 5 11: Drive gear 12: Driven gear

Claims

1. An external gear pump in which a drive gear and a driven gear that mesh with each other are housed rotatably inside a casing and liquid is drawn in and discharged by the rotation of both gears, wherein the parts of the casing that come into sliding contact with the both gears are made of a resin material.

2. 2. The external gear pump according to claim 1, wherein the portions of said gears which come into sliding contact with said casing are made of a material having solid lubricating properties which are lubricated only by solids.

3. 3. The external gear pump according to claim 2, wherein the material having solid lubricating properties is a DLC coating which covers the surfaces of both of the gears.

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