JP3602275B2 - Gear pump - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gear pump that performs a pumping operation by rotating a pair of gears that mesh with each other.
[0002]
[Prior Art and Problems to be Solved by the Invention]
BACKGROUND ART Conventionally, gear pumps have been used in various industrial fields because their capacity can be increased while having a simple structure.
As a structure of this kind of gear pump, a pair of side plates are fitted into a cavity inside the housing to define a gear chamber, and a pair of gears meshing with each other are housed inside the gear chamber, and a support shaft of each gear is formed. In general, a type in which a working fluid suction chamber and a discharge chamber are formed inside the gear chamber with a meshing position between both gears being fitted and supported by support holes formed in each side plate.
[0003]
An aluminum alloy is used for the housing and the side plate for workability and weight reduction, while an iron-based material such as cast iron is used because each gear requires wear resistance. Things are generalizing. However, when the support shaft of the gear is directly supported by the sliding surface of the support hole of the aluminum alloy side plate, there is a problem in that the support hole is severely worn, leading to a reduction in pump efficiency and a short life.
[0004]
In particular, in recent years, there has been a demand for increasing the pressure of the gear pump. However, as the pressure increases, the load increases, and the portion receiving the support shaft tends to wear. Then, as a cause of the occurrence of damage such as seizure in the portion receiving the support shaft, it can be supposed that a partial oil film rupture in the boundary lubrication region is the cause.
Therefore, an object of the present invention is to provide a gear pump that can prevent wear of a portion that receives a support shaft and can achieve high pump efficiency and long life.
[0005]
[Means for Solving the Problems]
In order to solve the above problem, in the gear pump according to the first aspect, a pair of side plates are fitted into a cavity inside the housing to define a gear chamber, and a pair of gears meshing with each other are housed inside the gear chamber. In a gear pump in which a suction chamber and a discharge chamber of a working fluid are formed with a meshing position of both gears interposed therebetween, a metal support shaft of each gear is inserted through a ceramic bush fitted into a support hole of each side plate. The bushing is supported so that the bearing clearance at the lowest operating temperature is 0.1% or more of the diameter of the support shaft, and the bush is press-fitted or sintered into the support hole so as to receive a predetermined compressive stress in the operating temperature range. It is characterized by being fitted .
[0006]
A ceramic bush can support the support shaft with little wear even under severe use conditions, thus improving durability. In addition, since the ceramic has a low coefficient of thermal expansion, the fitting gap between the ceramic and the support shaft can be reduced when the temperature is raised, so that the pump efficiency can be improved. Ceramics used for the bush include alumina, silicon carbide, silicon nitride, titania, mullite, and zirconia.
[0007]
Further, since the bush is press-fitted or shrink-fitted into the support hole so as to receive a predetermined compressive stress in a use temperature range, the following operation is achieved. That is, since the radial expansion of the bush is suppressed in the operating temperature range, the fitting gap between the bush and the support shaft can be reduced, and leakage of the working fluid through the fitting gap can be suppressed. As a result, the pump efficiency can be maintained high.
[0008]
In the gear pump according to the second aspect , a pair of side plates are fitted into the cavity inside the housing to define a gear chamber, and a pair of gears meshing with each other are housed inside the gear chamber, and the meshing positions of the two gears are sandwiched. In the gear pump in which the suction chamber and the discharge chamber of the working fluid are formed, the support shaft of each gear is supported via a ceramic bush fitted in the support hole of each side plate, and the bush is used in the operating temperature range. And is arranged in a floating manner between the support hole and the support shaft.
In this case, in the operating temperature range, the bush is in a state of both the support shaft and the support hole, and the bush rotates relative to both the support shaft and the support hole. Therefore, there are two sliding contact surfaces inside and outside the bush, and local wear can be reduced.
[0009]
According to a third aspect of the present invention, in the gear pump according to the first or second aspect , the bush is made of a porous ceramic coated with a solid lubricant.
In this case, even if the working fluid film breaks, lubrication can be assisted by the solid lubricant, so that wear can be prevented. In addition, since the ceramic is porous, the solid lubricant can be held for a long time, and the durability can be improved. Here, the solid lubricant includes PTFE, graphite, and molybdenum disulfide.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a sectional view of a gear pump according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line II-II of FIG. FIG. 3 is a sectional view taken along the line III-III in FIG. 1, and FIG. 4 is a sectional view taken along the line IV-IV in FIG.
[0011]
Referring to FIG. 1, the present gear pump has a body cylinder 10 having a cavity having an oval cross section penetrating a central portion thereof, and is closed on both sides by a pair of lid plates 11 screwed so as to cover the entire surface thereof. The housing 1 is provided. Inside the housing 1, a gear chamber 14 is defined between a pair of aluminum alloy side plates 12 inserted from both sides of the hollow part. , A driving gear 3 and a driven gear 4 are arranged. Reference numeral 19 denotes an O-ring that is housed in the annular groove of the cover plate 11 and is interposed between the cover plate 11 and the side plate 12 to seal the gear chamber 14. Reference numeral 13 denotes a seal that is housed in the housing groove of the side plate 12 and that partitions the space between the facing side plate 12 and the cover plate 11 in the gear chamber 14 into a low-pressure side and a high-pressure side.
[0012]
The driving gear 3 and the supporting shafts 30 and 40 of the driven gear are respectively located on the axes of the semicircular portions on both sides of the gear chamber 14 having an oval cross section, and are bridged in parallel with each other. That is, the ceramic bush 18 is fitted into the pair of support holes 31 and 41 formed in each side plate 12, and the support shafts 30 and 40 are supported by the support holes 31 and 41 via the bushes. Supported. The support shafts 30 and 40 are made of an iron-based material such as cast iron.
[0013]
One support shaft 30 supported by a pair of support holes 31 via a ceramic bush 18 extends through one cover plate 11 to the outside, and is transmitted to the extended end from a motor (not shown). It constitutes a drive shaft that is rotationally driven by the driving force. The drive gear 3 is mounted on the support shaft 30 so as to be integrally rotatable inside the gear chamber 14. An oil seal 17 is disposed at a portion where the support shaft 30 penetrates the cover plate 11.
[0014]
The other support shaft 40 supported by the pair of support holes 41 via the ceramic bush 18 constitutes a driven shaft having a shaft end in the support hole 41 of each side plate 12. The driven gear 4 is mounted on the support shaft 40 inside the gear chamber 14. When the driven gear 4 is mounted on the support shaft 40, rotation around the axis may be restricted or rotation around the axis may be allowed. The driven gear 4 meshes with the drive gear 3 in a plane including the axes of the two support shafts 30 and 40, and together with the support shaft 40 (or of the support shaft 40) with the rotation of the drive gear 3 driven by the support shaft 30. It is driven (without rotation).
[0015]
The bush 18 is press-fitted or shrink-fitted into each of the support holes 31 and 41, and the relative rotation of the bush 18 with respect to the support holes 31 and 41 is restricted. It is preferable to set the fitting accuracy so that a compressive stress of 5 kgf / mm ² or more is applied to the bush 18 at the maximum operating temperature. Ceramics constituting the bush 18 include alumina, silicon carbide, silicon nitride, titania, mullite, and zirconia. As the bush 18, porous ceramics coated with a solid lubricant may be used. In this case, even if the working fluid film breaks, lubrication can be assisted by the solid lubricant, so that wear can be prevented. In addition, since the ceramic is porous, there is an advantage that the solid lubricant can be retained for a long period of time and the durability can be improved. Here, examples of the solid lubricant include PTFE, graphite, molybdenum disulfide, and the like, and other known solid lubricants can be used.
[0016]
Further, the shape of the bush 18 is not particularly limited, but may be a straight cylinder as shown in FIG. 1, or in order to prevent local abrasion due to one end of the support shafts 30 and 40. As shown in FIG. 6A, the inner peripheral surface 18a of the bush 18 may be crowned so that the central portion expands along the axial direction (to increase the diameter of the central portion). Further, as shown in FIG. 6 (b), the outer diameter may be tapered so that the outer diameter becomes farther from the gears 3 and 4, or a flange having a flange 18d may be used as shown in FIG. 6 (c). In each of the examples, a spiral groove 18c is formed on the inner peripheral surface 18a of the bush 18 for axially sending the working fluid with the rotation of the support shafts 30, 40. Instead of 18c, a linear groove along the axial direction may be used. In each example, the bush 18 may be of a split type. The surface roughness of the inner peripheral surface 18a of the bush 18 and the gear-side end surface 18b of the bush 18 is preferably 0.8z or less. Note that the support shafts 30 and 40 may be crowned along the axial direction so that the central portions in the axial direction relatively swell.
[0017]
In FIG. 2, the rotation direction of the drive gear 3 and the driven gear 4 interlocked with the drive gear 3 are indicated by arrows, and on both sides of the meshing position of the two gears 3, 4, the suction port chamber is provided on the rotation direction side. 5, a discharge chamber 6 is formed on the side opposite to the rotation direction. The suction chamber 5 and the discharge chamber 6 are connected to a suction destination and a discharge destination (not shown) outside the housing 1 via a suction port 15 and a discharge port 16 that open at corresponding positions of the main body cylinder 10. .
[0018]
In FIG. 3, a relief groove 63 extending toward the suction chamber 5 and a relief groove 64 extending toward the discharge chamber 6 are formed on the gear side surface 12a of the side plate 12 from the meshing position of the two gears 3, 4. These escape grooves 63 and 64 are used to prevent so-called confinement in which fluid is confined in a closed area formed by each side plate 12 and each meshing gear tooth at a meshing position of the two gears 3 and 4. Things. The escape grooves 63 and 64 are provided so as to avoid the center position where the gears 3 and 4 mesh with each other, and a predetermined distance is secured between them. This is because if the escape grooves 63 and 64 are communicated, the suction chamber 5 and the discharge chamber 6 communicate with each other and the pump function cannot be performed. In addition, a communication groove 65 is formed in the gear side surface 12a to communicate each of the support holes 31, 41 and the suction chamber 5 side.
[0019]
On the other hand, in FIG. 4, the above-mentioned seal 13 is accommodated in a substantially W-shaped seal groove on the opposite gear side surface 12b of the side plate 12, and the side plate 12 and the opposing side plate 12 are The space between the cover plate 11 is partitioned into a low pressure side space communicating with the suction chamber 5 side and a high pressure side space communicating with the discharge chamber 6 side. In this manner, the low-pressure working fluid and the high-pressure working fluid act as back pressure on the non-gear side surface 12b, which is the back surface of the side plate 12, in a state partitioned by the seal 13, and this acts on the side plate 12. Since the load is applied in accordance with the discharge pressure, the gap between the side plate 12 and the two gears 3 and 4 is maintained with high precision, so that the pump efficiency at high pressure can be maintained at a high level. Further, a pair of communication grooves 65 are formed in the anti-gear side surface 12b to communicate the support holes 31 and 41 with the suction chamber 5 side in the low pressure side space.
[0020]
With such a configuration, the working fluid introduced into the suction chamber 5 through the suction port 15 is received between the teeth of the driving gear 3 and the driven gear 4 facing the suction chamber 5, and the rotation of the gears 3, 4 causes the working fluid to flow. Is conveyed in a state of being sealed between the respective teeth and the inner peripheral surface of the main body cylinder 10 and sent out to the discharge chamber 6. The drive gear 3 and the driven gear 4 which have finished sending out to the discharge chamber 6 face the suction chamber 5 side through the meshing position of the two gears 3 and 4, receive the working fluid in the suction chamber 5 again, and discharge the discharge chamber. It works to send out to the 6 side.
[0021]
On the other hand, with reference to FIG. 5 which is a partially broken exploded perspective view of a main part of the gear pump, the working fluid from the suction chamber 5 on the low pressure side is on the sliding surface between the bush 18 and each of the support shafts 30 and 40. It is being circulated. That is, since the above-mentioned spiral groove 18c is formed on the inner peripheral surface 18a of the bush 18, it is formed on one side surface 12a or 12b of the side plate 12 by rotating the support shafts 30, 40. The working fluid on the suction chamber 5 side is introduced into the bush 18 through the communication groove 65, and is returned to the suction chamber 5 through the communication groove 65 formed on the other side surface 12 b or 12 a of the side plate 12. ing. In order to make parts common, the spiral grooves 18c of the inner peripheral surface 18a of the bush 18 are all formed in the same direction, and both gears 3 and 4 rotate in opposite directions. The working fluid is introduced into the upper left and lower right bushes 18 from the side opposite to the gear side of the side plate 12 (indicated by black arrows in FIG. 5), and into the lower right and upper left bushes 18. The working fluid is introduced from the gear side surface (indicated by white arrows in FIG. 5).
[0022]
In the present embodiment, since the bush 18 made of ceramics is used, the spindles 30 and 40 can be supported with little wear even under severe use conditions. As a result, the durability can be improved and the wear caused by the wear can be improved. A decrease in pump efficiency can be prevented. Further, since the ceramic has a low coefficient of thermal expansion, the fitting gap between the support shaft 30 made of an iron-based material and the bush 18 made of ceramic can be reduced when the temperature is raised, so that the pump efficiency at high temperatures can be improved.
[0023]
In particular, since the bush 18 is press-fitted or shrink-fitted into the support holes 31 and 41 of the side plate 12, radial expansion of the bush 18 is suppressed in the operating temperature range. Therefore, the fitting gap between the bush 18 and the support shaft 30 can be reduced, and the leakage of the working fluid through the fitting gap can be suppressed. As a result, the pump efficiency can be maintained high.
Further, when the bush 18 is made of ceramics having excellent wear resistance, there is a possibility that uneven wear due to one-sided contact may occur on the metal support shafts 30 and 40, as shown in FIG. 6 (a). Thus, it can be avoided by crowning the inner peripheral surface 18a of the bush 18. In addition, from the viewpoint of preventing uneven wear, it is preferable that the bearing clearance at the lowest operating temperature is 0.1% or more of the diameter of the support shafts 30 and 40. Further, the support shafts 30 and 40 may be made of ceramics, or both the support shafts 30 and 40 and the gears 3 and 4 may be made of ceramics. In this case, besides improving the durability of the gear pump, reduction of the initial rotational torque (starting torque) can be expected because the inertial force can be reduced.
[0024]
In the above-described embodiment, the bush 18 is fixed by press-fitting or shrink-fitting the support holes 31 and 41. However, as shown in FIG. The support shafts 30 and 40 may be in a state of clearance with respect to both so that the support shafts 30 and 40 can relatively rotate. In this case, the sliding contact surface is provided at two locations inside and outside the bush 18 and local wear can be reduced, so that the durability and reliability of the gear pump can be improved. On the high temperature side in the operating temperature range, the fitting gap S1 between the support shafts 30, 40 and the bush 18 is relatively loose, while on the low temperature side in the operating temperature range, the bush 18 and the support holes 31, Although the fitting gap S2 with the bushing 41 is relatively loose, the total gap amount (S1 + S2) related to the bush 18 is substantially unchanged, so that the pump efficiency at high temperatures does not decrease.
[0025]
The present invention is not limited to the above embodiments, and various changes can be made within the scope of the present invention.
[0026]
【The invention's effect】
According to the first aspect of the present invention, since the bush made of ceramics is used, the spindle can be supported with little wear even under severe use conditions, so that the durability can be improved and the pump caused by wear can be improved. A decrease in efficiency can be prevented. In addition, since the ceramic has a low coefficient of thermal expansion, the fitting gap between the ceramic and the support shaft can be reduced when the temperature is raised, so that the pump efficiency at high temperatures can be improved.
[0027]
Further , since the radial expansion of the bush is suppressed in the operating temperature range, the fitting gap between the bush and the support shaft can be reduced, and the leakage of the working fluid through the fitting gap can be suppressed. As a result, the pump efficiency can be maintained high.
According to the second aspect of the present invention, in the operating temperature range, the bush is in a state of both the support shaft and the support hole, and the bush rotates relative to both the support shaft and the support hole. Therefore, there are two sliding contact surfaces inside and outside the bush, and local wear can be reduced.
[0028]
According to the third aspect of the invention, even if the working fluid film breaks, lubrication can be assisted by the solid lubricant, so that wear can be prevented. In addition, since the ceramic is porous, the solid lubricant can be held for a long time, and the durability can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view of a gear pump according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, with hatching omitted.
FIG. 3 is a sectional view taken along the line III-III in FIG. 1;
FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;
FIG. 5 is a partially exploded perspective view of a main part of the gear pump.
FIGS. 6A to 6C are cross-sectional views each showing a modified form of a bush.
FIG. 7 is a schematic sectional view showing a fitted state of a bush according to another embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 housing 3 drive gear 4 driven gear 5 suction chamber 6 discharge chamber 12 side plate 12a gear side surface 12b non-gear side surface 14 gear chamber 18 bush 18a inner peripheral surface 18b gear side end surface 18c spiral groove 30, 40 41 Support hole

Claims (3)

A gear chamber is defined by fitting a pair of side plates into a cavity inside the housing, and a pair of gears meshing with each other are housed inside the gear chamber, and a suction chamber and a discharge chamber for the working fluid interpose the meshing position of both gears. In a gear pump that forms a chamber,
The metal support shaft of each gear is passed through a ceramic bush fitted into the support hole of each side plate so that the bearing clearance at the minimum operating temperature is 0.1% or more of the support shaft diameter. It has been supported by,
A gear pump, wherein the bush is press-fitted or shrink-fitted into the support hole so as to receive a predetermined compressive stress in an operating temperature range . A gear chamber is defined by fitting a pair of side plates into a cavity inside the housing, and a pair of gears meshing with each other are housed inside the gear chamber, and a suction chamber and a discharge chamber for the working fluid interpose the meshing position of both gears. In a gear pump that forms a chamber,
The support shaft of each gear is supported via a ceramic bush fitted into the support hole of each side plate,
2. The gear pump according to claim 1, wherein the bush is disposed so as to float between the support hole and the support shaft in an operating temperature range . 3. The gear pump according to claim 1, wherein the bush is made of a porous ceramic coated with a solid lubricant .

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