CN117597515A

CN117597515A - Internal gear pump

Info

Publication number: CN117597515A
Application number: CN202380011294.5A
Authority: CN
Inventors: 石夏氷; 大西孝明; 竹田博昭
Original assignee: Sumitomo Precision Products Co Ltd
Current assignee: Sumitomo Precision Products Co Ltd
Priority date: 2022-06-16
Filing date: 2023-06-14
Publication date: 2024-02-23
Also published as: JP2023183867A; WO2023243665A1

Abstract

The internal gear pump (1) comprises a pinion (3), a ring gear (4), a housing (10) and a crescent (54), wherein the crescent (54) is provided with a first arc wall (541) for the external teeth (31) to abut against and a second arc wall (542) for the internal teeth (41) to abut against, the first arc wall and the second arc wall are both fixed walls which do not move towards the external teeth and the internal teeth, and in the housing, a pressure transmission oil path (91) extending from the ejection path is formed only in the region on the pinion side and the region on the ring gear side of the crescent, and the pressure transmission oil path enables the space between the ejection path and the teeth of the ring gear to communicate.

Description

Internal gear pump

Technical Field

The technology disclosed herein relates to a crescent gear pump.

Background

Patent document 1 describes a crescent gear pump 1. The internal gear pump 1 has a separating member 7 (so-called crescent-shaped member). The tooth tips of the internal gear 2 and the tooth tips of the pinion 3 are respectively abutted against the separating member 7.

The separating member 7 has an inner portion 13, an outer portion 14 and a spring 16. The spring 16 pushes the inner part 13 against the tooth top of the pinion 3 and the outer part 14 against the tooth top of the internal gear 2. The separating member 7 has a movable construction. The movable separation member 7 can suppress fluid leakage in the internal gear pump 1 and improve pump efficiency.

The separating member 7 also has an intermediate space 17 between the inner part 13 and the outer part 14. The intermediate space 17 communicates with the pressurizing region 9 of the internal gear pump 1. The inner portion 13 and the outer portion 14 have a penetration 19. The penetration portion 19 penetrates the inner portion 13 and the outer portion 14 in the radial direction, respectively, and communicates the intermediate space 17 with spaces between the teeth of the pinion 3 and the internal gear 2. When the internal gear pump 1 is operated, the pressure in the intermediate space 17 is the same as the pressure in the pressurizing region 9, and therefore, the pressure in the space between the pinion 3 and the teeth of the internal gear 2 rises through the penetration portion 19. The high pressure in the space between the teeth suppresses abrupt pressure change at the pump discharge portion, thereby suppressing noise of the internal gear pump 1.

Patent document 1: japanese patent No. 6297277

Disclosure of Invention

Technical problem to be solved by the invention

In order to suppress noise, the penetration portion 19 of the internal gear pump 1 of patent document 1 supplies liquid from the pump discharge portion to between the separating member 7 and the pinion 3 and between the separating member 7 and the internal gear 2. However, the supply of the liquid described above increases the leakage of the fluid in the internal gear pump 1. Although the conventional internal gear pump can suppress noise, the pump efficiency is lowered.

The technology disclosed herein can suppress both noise of the internal gear pump and degradation of pump efficiency.

Technical solution for solving the technical problems

The crescent of the internal gear pump 1 described in patent document 1 has a movable structure. In contrast, a crescent gear pump is also known, which has a crescent-shaped part of an immovable design.

The inventor of the application obtains new findings through research: in the case of a crescent having an immovable configuration, the pressure of the spaces between the teeth of the pinion is relatively high. The reason for this is that the wall of the crescent is not pressed by the external teeth of the pinion, and therefore there is a slight gap between the teeth of the pinion and the wall of the crescent. The minute gap allows fluid from the ejection passage to leak, which increases the pressure of the space between the teeth of the pinion.

Even if a structure is added to the internal gear pump to supply the working oil from the discharge passage to the space between the teeth of the pinion gear in order to suppress noise, only the fluid leakage is increased, the pump efficiency is reduced, and the noise suppressing effect of the internal gear pump is not substantially improved.

In the internal gear pump having the crescent member of the immovable structure, the present inventors formed only the pressure transmission oil passage extending from the discharge passage to the space between the teeth of the ring gear in the housing.

In particular, the technology disclosed herein relates to a crescent gear pump. The internal gear pump comprises a pinion, a gear ring, a shell and a crescent part,

the pinion gear has an external tooth that is externally toothed,

the ring gear has internal teeth engaged with the external teeth,

the housing has a suction passage and a discharge passage, houses the pinion and the ring gear, is rotatable,

the crescent part is positioned at the meshing and separating position of the pinion and the gear ring and is provided with a first arc wall for the external teeth to abut and a second arc wall for the internal teeth to abut,

the first circular arc wall and the second circular arc wall are both fixed walls which do not move towards the external teeth and the internal teeth,

in the case, a pressure transmission oil passage extending from the discharge passage is formed only in the ring gear side region out of the pinion side region and the ring gear side region sandwiching the crescent,

the pressure transmission oil passage communicates the ejection passage with a space between teeth of the ring gear.

The space between the teeth of the ring gear is a space between adjacent teeth in the ring gear.

The internal gear pump has a configuration in which the crescent is not movable. As previously mentioned, the pressure in the spaces between the teeth of the pinion is relatively high.

In the case, a pressure transmission oil passage is formed only in a region on the ring gear side out of a region on the pinion side and a region on the ring gear side sandwiching the crescent. The pressure transmission oil passage extending from the discharge passage flows a part of the hydraulic oil from the discharge passage to the low pressure side. Since the pressure transmission oil passage communicates the discharge passage with the space between the teeth of the ring gear, a part of the high-pressure hydraulic oil in the discharge passage flows to the space between the teeth of the ring gear. The pressure of the space between the teeth of the ring gear increases. The higher pressure of the spaces between the teeth suppresses abrupt pressure changes at the ejection path.

Even without the pressure transmission oil passage, the pressure of the space between the teeth of the pinion is high. On the pinion side, abrupt pressure changes in the ejection passage can be suppressed.

Since the pressure transmission oil passage is formed only in the region on the ring gear side of the crescent member sandwiching the immovable structure, abrupt pressure changes at the discharge passage can be suppressed on the ring gear side and the pinion side, respectively, and thus noise of the internal gear pump can be suppressed.

Although the pressure transmission oil passage promotes fluid leakage of the internal gear pump, the pressure transmission oil passage is formed only in the region on the ring gear side and is not formed in the region on the pinion side. The increase in fluid leakage of the internal gear pump is suppressed. Therefore, a decrease in pump efficiency can be suppressed.

Therefore, the internal gear pump can suppress noise and can suppress a decrease in pump efficiency.

It may also be: the housing has a sliding surface for sliding an outer peripheral surface of the ring gear,

the internal gear pump includes a high-pressure oil supply unit that supplies high-pressure hydraulic oil between the outer peripheral surface and the sliding surface through an introduction port that opens in the sliding surface,

the introduction port is located on the opposite side of the crescent member from the ring gear.

The high-pressure oil supply unit supplies high-pressure hydraulic oil between the outer peripheral surface of the ring gear and the sliding surface of the housing. The supplied high-pressure working oil pushes the ring gear toward the rotation shaft of the ring gear. Since the introduction port is located on the opposite side of the crescent from the sandwiching ring gear, the internal teeth of the ring gear are pressed against the second circular arc wall of the crescent. The leakage of the working oil from between the internal teeth and the second circular arc wall can be suppressed. The high-pressure oil supply portion increases the pump efficiency of the internal gear pump.

The internal teeth of the ring gear are pressed against the second circular arc wall of the crescent, which on the one hand increases the pump efficiency and on the other hand suppresses the pressure rise in the spaces between the teeth of the ring gear caused by the leakage of fluid from the ejection passage. The lower pressure in the spaces between the teeth of the ring gear increases the noise of the internal gear pump.

The internal gear pump has a pressure transmission oil passage formed in a housing in a region on a ring gear side. As described above, the pressure transmitting oil passage increases the pressure of the space between the teeth of the ring gear. The combination of the high-pressure oil supply portion and the pressure transmission oil passage on the ring gear side can suppress noise of the internal gear pump at a high level and suppress a decrease in pump efficiency at a high level.

It may also be: the housing has a first bearing surface and a second bearing surface, which respectively support the side surfaces of the ring gear, i.e., the two side surfaces orthogonal to the rotation axis of the ring gear,

the ejection passages are formed on the first support surface and the second support surface, respectively,

the pressure transmitting oil passage is formed to be recessed from the first bearing surface, the second bearing surface or the first bearing surface and the second bearing surface,

when viewed along the direction of the rotation axis, the pressure transmission oil path coincides with the space between the teeth of the ring gear.

When viewed in the direction of the rotation axis, the pressure transmission oil passage formed in the first support surface and/or the second support surface overlaps with the space between the teeth of the ring gear, and therefore, the hydraulic oil can be supplied from the discharge passage to the space between the teeth of the ring gear. The pressure of the space between the teeth of the ring gear increases.

It may also be: the pressure transmitting oil passage formed on the first bearing surface and/or the second bearing surface has a triangular cross section. It may also be: the pressure transmitting oil passage formed on the first bearing surface and/or the second bearing surface has a quadrangular cross section.

It may also be: the pressure transmitting oil passage is a groove formed on the first bearing surface and/or the second bearing surface.

It may also be: the pressure transmission oil path is in a straight line. It may also be: the pressure transmission oil path is in a curve shape.

It may also be: the pressure transmission oil passage is formed recessed from the second circular arc wall of the crescent member.

It may also be: the pressure transmission oil passage is formed by cutting a notch in a surface of the crescent.

The pressure transmission oil passage formed on the second circular arc wall of the crescent communicates with the space between the teeth of the ring gear. The pressure transmission oil passage can supply hydraulic oil from the discharge passage to the space between the teeth of the ring gear. The pressure of the space between the teeth of the ring gear increases.

It may also be: the depth of the pressure transmission oil passage becomes gradually shallower as it is farther from the discharge passage. It may also be: the depth of the pressure transmission oil path is constant. It may also be: the pressure transmission oil passage gradually narrows in width as it is farther from the discharge passage. It may also be: the width of the pressure transmission oil path is a constant width.

It may also be: the tip end of the pressure transmission oil passage is located within a range of an angle θ1 or more and an angle θ2 or less from an edge of the discharge passage, the angle θ1 corresponding to a tooth width of the ring gear, and the angle θ2 being an angle between an edge of the discharge passage and an intermediate position of the crescent extending from the discharge passage to the suction passage, the range being centered on a rotation axis of the ring gear.

The pressure transmission oil passage with a proper length can inhibit noise of the internal gear pump and inhibit pump efficiency from decreasing.

In the case where the tip end of the pressure transmission oil passage is located at a position smaller than θ1, the pressure transmission oil passage is excessively short. That is, the excessively short pressure transmission oil passage cannot raise the pressure of the space between the teeth of the ring gear before the space opens to the discharge passage.

Even if the tip of the pressure transmission oil passage is located at a position exceeding θ2, the noise suppression effect is substantially the same as that at θ2 or less. On the other hand, too long a pressure transmission oil passage increases the leakage of the working oil, which results in a decrease in pump efficiency.

When the tip of the pressure transmission oil passage is located in the range of the angle θ1 or more and the angle θ2 or less, the noise can be suppressed and the pump efficiency can be suppressed from decreasing.

Effects of the invention

The internal gear pump can suppress noise and can suppress a decrease in pump efficiency.

Drawings

FIG. 1 is an exploded view of a crescent gear pump;

FIG. 2 is a cross-sectional view of the internal gear pump;

fig. 3 shows an example of the pressure transmission oil passage;

fig. 4 is a modification of the pressure transmission oil passage;

fig. 5 is a modification of the pressure transmission oil passage.

Detailed Description

Embodiments of the internal gear pump will be described below with reference to the drawings. The internal gear pump described herein is merely exemplary.

(integral construction of internal Gear Pump)

Fig. 1 and 2 show an example of a crescent gear pump 1. The internal gear pump 1 includes a shaft 2, a pinion 3, a ring gear 4, a gear housing 5, and a front cover 6. The gear housing 5 and the front cover 6 are housings 10 of the internal gear pump 1. Fig. 1 is an exploded view of the front cover 6 after being detached from the gear housing 5.

The shaft 2 extends in the left-right direction of the paper surface of fig. 2. The shaft 2 is constituted by a first shaft 21 and a second shaft 22. The first shaft 21 and the second shaft 22 are combined to be coaxial and integrally rotated. The second shaft 22 protrudes from the housing 10 and is connected to a prime mover, not shown. The prime mover is, for example, an electric motor.

The pinion 3 is integrally formed at an intermediate position of the first shaft 21. Pinion 3 is coaxial with shaft 2. Pinion 3 rotates with shaft 2. Pinion 3 has external teeth 31.

The ring gear 4 meshes with the pinion 3. The ring gear 4 is arranged eccentrically with respect to the shaft 2. C1 in fig. 1 is the rotation axis of the pinion 3, and C2 is the rotation axis of the ring gear 4. On the inner peripheral surface of the ring gear 4, internal teeth 41 are formed. In the right view of fig. 1, in the region on the right side of the paper, a part of the external teeth 31 of the pinion 3 meshes with a part of the internal teeth 41 of the ring gear 4.

The gear housing 5 houses the pinion 3 and the ring gear 4. An inner hole 53 is formed in the gear housing 5. The end of the first shaft 21 is located within the bore 53.

The pinion 3 and the ring gear 4 are rotatably accommodated in the gear housing 5. The gear housing 5 has a sliding surface 51 on which the outer peripheral surface 42 of the ring gear 4 slides. The outer peripheral surface 42 of the ring gear 4 has a circular cross-sectional shape. The sliding surface 51 of the gear housing 5 also has a circular cross-sectional shape. The sliding surface 51 is eccentric with respect to the shaft 2.

The gear housing 5 has a first bearing surface 52 orthogonal to the sliding surface 51. The sliding surface 51 and the first support surface 52 form a space 50 for accommodating the pinion 3 and the ring gear 4. The space 50 is open to the left of the paper surface in fig. 2. The first side surface 32 of the pinion 3 and the first side surface 43 of the ring gear 4 are supported by the first support surface 52 of the gear housing 5, respectively, and slide on the first support surface 52. The first side surface 32 of the pinion 3 is a surface orthogonal to the rotation axis C1 of the pinion 3, that is, a right side surface in fig. 2. The first side surface 43 of the ring gear 4 is a surface orthogonal to the rotation axis C2 of the ring gear 4, i.e., a side surface on the right side of fig. 2.

The front cover 6 is provided adjacent to the gear housing 5. The front cover 6 and the gear housing 5 are integrated by being fixed to each other. The front cover 6 has a second bearing surface 61 which contacts the gear housing 5 and closes the space 50. The second side surface 33 of the pinion 3 and the second side surface 44 of the ring gear 4 are supported by the second support surface 61 of the front cover 6, respectively, and slide on the second support surface 61. The second side surface 33 of the pinion 3 is a surface orthogonal to the rotation axis C1 of the pinion 3, that is, a left side surface in fig. 2. The second side surface 44 of the ring gear 4 is a surface orthogonal to the rotation axis C2 of the ring gear 4, i.e., a left side surface in fig. 2.

The front cover 6 is formed with a support hole 62 through which the shaft 2 passes. The shaft 2 is rotatably supported by the front cover 6 and the gear housing 5 via a bearing 63 and a bearing member 64. The opening of the supporting hole 62 is closed by a sealing member 621.

The front cover 6 and the gear housing 5 are provided with a suction passage 11. The suction passage 11 is a passage for sucking the working oil into the space 50 inside the housing 10. As shown in fig. 2, an inlet of the suction passage 11 opens on the outer peripheral surface of the front cover 6. As shown in fig. 1 and 2, the outlet of the suction passage 11 opens on the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5, respectively. The outlet of the suction passage 11 also extends circumferentially along the direction of rotation of the shaft 2.

The front cover 6 and the gear housing 5 are further provided with a discharge passage 12. The discharge passage 12 is a passage through which the working oil is discharged from the space 50 inside the casing 10. As shown in fig. 2, the outlet of the ejection passage 12 opens on the outer peripheral surface of the gear housing 5. The direction of the inlet of the suction passage 11 and the direction of the outlet of the discharge passage 12 may be different from each other as shown in fig. 2, or may be the same direction, and they are not shown.

The inlet of the ejection passage 12 opens on the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5, respectively. As shown in fig. 1, the inlet of the discharge passage 12 extends circumferentially along the rotation direction of the shaft 2 on the opposite side of the shaft 2 from the suction passage 11.

A crescent 54 is provided on the gear housing 5. The crescent 54 is provided at a position where the pinion 3 is engaged with and disengaged from the ring gear 4. The crescent 54 separates a second region from a first region, which will be described later.

The crescent 54 extends circumferentially over a prescribed angular range along the direction of rotation of the shaft 2. As shown in fig. 1, the crescent 54 is crescent-shaped when viewed in the axial direction of the shaft 2. The crescent 54 has two arcuate walls, i.e., a first arcuate wall 541 and a second arcuate wall 542, and the first arcuate wall 541 and the second arcuate wall 542 are provided upright on the first support surface 52 of the gear housing 5.

The tooth tip of the external tooth 31 of the pinion 3 substantially abuts against the first circular arc wall 541 of the crescent 54. The tooth tops of the internal teeth 41 of the ring gear 4 substantially abut against the second circular arc wall 542 of the crescent 54. The first circular arc wall 541 and the second circular arc wall 542 are fixed walls that do not move toward the external teeth 31 and the internal teeth 41.

The casing 10 can be circumferentially divided into three regions, i.e., a first region in which the suction passage 11 is opened, a second region in which the discharge passage 12 is opened, and a third region between the first region and the second region in which the crescent 54 is provided, around the rotation axis C2 of the ring gear 4. The first region is a low pressure region and the second region is a high pressure region.

The operation of the internal gear pump 1 will be briefly described below. When the shaft 2 is driven by the prime mover to rotate clockwise in the right view of fig. 1, the pinion 3 and the ring gear 4 rotate in directions from the first region to the second region through the third region, respectively.

In the first region in the housing 10, as the external teeth 31 of the engaged pinion 3 are separated from the internal teeth 41 of the ring gear 4, the working oil is sucked from the suction passage 11 between the external teeth 31 and the internal teeth 41. The sucked hydraulic oil is transported from the first region to the second region through the third region as the pinion 3 and the ring gear 4 rotate.

In a second region within the housing 10, the external teeth 31 of the separated pinion 3 come closer to and mesh with the internal teeth 41 of the ring gear 4. Thus, the hydraulic oil is discharged from between the external teeth 31 and the internal teeth 41 through the discharge passage 12.

(Structure for improving Pump efficiency)

The internal gear pump 1 includes a high-pressure oil supply portion 8. The high-pressure oil supply portion 8 supplies high-pressure hydraulic oil between the outer peripheral surface 42 of the ring gear 4 and the sliding surface 51 of the gear housing 5. The high-pressure oil supply portion 8 is shown only in fig. 1.

The high-pressure oil supply portion 8 pushes the ring gear 4 from the outer periphery of the third region toward the rotary shaft C2 by the high-pressure working oil. Since the tooth tip of the ring gear 4 is pushed against the second circular arc wall 542 of the crescent 54, the leakage of the working oil from the high pressure side to the low pressure side can be suppressed in the housing 10.

The high-pressure oil supply portion 8 includes an inlet 81 that opens on the sliding surface 51, and a supply passage 82 that connects the discharge passage 12 and the inlet 81.

As shown in fig. 1, the introduction port 81 is located in the third region. In more detail, the introduction port 81 is opposed to the crescent 54 in the radial direction across the ring gear 4. The introduction port 81 introduces a part of the high-pressure hydraulic oil discharged from the discharge passage 12 into the housing 10. In order to efficiently press the tooth tip of the ring gear 4 against the crescent 54, the introduction port 81 is preferably located opposite to the crescent 54. In order to suppress the flow of the high-pressure working oil introduced into the housing 10 to the low-pressure first region, the introduction port 81 is preferably located in the high-pressure side region among the third region bisected into the low-pressure side region and the high-pressure side region.

The supply path 82 is formed in the gear housing 5. The supply passage 82 connects the discharge passage 12, which opens on the first support surface 52 of the gear housing 5, with the introduction port 81. The supply path may be formed in the front cover 6 and the gear housing 5 to connect the discharge path 12 opened in the second support surface 61 of the front cover 6 to the inlet 81. The supply path may connect the discharge passage 12 opened in the first support surface 52 to the inlet 81, and may connect the discharge passage 12 opened in the second support surface 61 to the inlet 81.

As described above, during operation of the internal gear pump 1, a part of the high-pressure hydraulic oil in the discharge passage 12 is introduced between the outer peripheral surface of the ring gear 4 and the sliding surface 51 of the gear housing 5 through the supply passage 82 and the introduction port 81. The high-pressure working oil pushes the ring gear 4 from the outer periphery of the third region toward the rotary shaft C2. The tooth tip of the ring gear 4 is pressed against the second circular arc wall 542 of the crescent 54. In the third region, the working oil is prevented from leaking from the high pressure side to the low pressure side by passing between the tooth tip of the ring gear 4 and the second circular arc wall 542 of the crescent 54. By suppressing the fluid leakage in the housing 10, the pump efficiency of the internal gear pump 1 is improved.

The high-pressure oil supply portion 8 may have a flow restrictor in the middle of the supply passage 82. The flow restrictor regulates the pressure of the working oil introduced between the outer peripheral surface of the ring gear 4 and the sliding surface 51 of the gear housing 5.

In the internal gear pump 1, the high-pressure oil supply portion 8 may be omitted. In the internal gear pump 1, the high-pressure oil supply portion 8 is not an essential element.

(noise suppressing Structure)

In the internal gear pump 1, when the space between the teeth of the pinion 3 and the space between the teeth of the ring gear 4 are opened to the discharge passage 12 by the third region, noise is generated due to a pressure difference between the pressure of the discharge passage 12 and the pressure of the space between the teeth. The larger the pressure difference between the pressure of the discharge passage 12 and the pressure of the space between the teeth, the larger the pressure variation when the space between the teeth opens to the discharge passage 12, and thus the larger the noise of the internal gear pump. The internal gear pump 1 has a pressure transmission oil passage 91 that suppresses noise.

The pressure transmission oil passage 91 increases the pressure of the hydraulic oil in the space between the teeth in the third region in advance by the high pressure of the discharge passage 12, and thus, the pressure difference between the pressure of the discharge passage 12 and the pressure of the space between the teeth is small. When the pressure difference is small, the pressure fluctuation when the space between the teeth opens to the discharge passage 12 becomes small, and therefore noise of the internal gear pump can be suppressed.

In the internal gear pump 1 shown in fig. 1 and 3, the pressure transmission oil passage 91 is formed recessed from the second support surface 61 of the front cover 6. In the right view of fig. 1 and fig. 3, the pressure transmission oil passage 91 formed in the front cover 6 is projected onto the gear housing 5 in order to clearly show the positional relationship among the pressure transmission oil passage 91, the ring gear 4, and the crescent 54, with respect to the pressure transmission oil passage 91 shown by the two-dot chain line.

The pressure transmitting oil passage 91 is a groove formed on the second bearing surface 61. As shown in fig. 3, the pressure transmission oil passage 91 has a triangular cross-sectional shape. The shape of the cross section of the pressure transmission oil passage 91 is not limited to a triangle. The cross section may be, for example, a quadrilateral.

The pressure transmission oil passage 91 extends straight from the edge of the discharge passage 12 toward the low pressure side of the third region. As shown in fig. 3, the depth of the pressure transmission oil passage 91 becomes gradually shallower as it gets farther from the discharge passage 12, and the width of the pressure transmission oil passage 91 becomes gradually narrower as it gets farther from the discharge passage 12. The depth of the pressure transmission oil passage may be a constant depth, and the width of the pressure transmission oil passage may be a constant width.

In other words, in the right view of fig. 1 or fig. 3, the pressure transmission oil passage 91 coincides with the space between the teeth of the ring gear 4 when viewed in the direction of the rotation axis C2 of the ring gear 4. Since the pressure transmission oil passage 91 is linear and the crescent 54 is crescent-shaped, the base end of the pressure transmission oil passage 91 (i.e., the connection end of the pressure transmission oil passage 91 and the discharge passage 12) is located near the radially outermost edge of the discharge passage 12, the middle portion of the pressure transmission oil passage 91 is located near the second circular arc wall 542 of the crescent 54, and the tip end of the pressure transmission oil passage 91 is located at a position distant from the second circular arc wall 542 of the crescent 54. The pressure transmission oil passage 91 can extend while avoiding interference with the crescent 54.

In the third region, the tooth tips of the ring gear 4 are pressed against the second circular arc wall 542 of the crescent 54, so that the spaces between the teeth of the ring gear 4 are closed. The pressure transmission oil passage 91 communicates with the space between the teeth of the ring gear 4 in the direction orthogonal to the paper surface of fig. 1 or 3. A part of the high-pressure hydraulic oil in the discharge passage 12 flows into the space between the teeth of the ring gear 4 through the pressure transmission oil passage 91, and increases the pressure in the space. The present inventors can confirm, from the result obtained by actually measuring the pressure in the housing 10: if the pressure transmission oil passage 91 is not formed, the pressure in the space between the teeth of the ring gear 4 is reduced with respect to the discharge pressure on the ring gear 4 side of the crescent 54 in the third region, and on the other hand, the pressure in the space is increased due to the formation of the pressure transmission oil passage 91. Since the pressure of the space between the teeth of the ring gear 4 increases in advance in the third region, the pressure difference between the pressure of the ejection passage 12 and the pressure of the space between the teeth decreases. Since pressure fluctuation when the space is opened to the discharge passage 12 is suppressed, noise of the internal gear pump 1 is suppressed. As is clear from the study of the present inventors, it was confirmed that the higher the discharge pressure of the internal gear pump 1, the better the noise level improving effect was due to the reduction in noise level caused by the formation of the pressure transmission oil passage 91.

In the internal gear pump 1, a pressure transmission oil passage is formed in the housing 10 only in the region on the pinion 3 side and the region on the ring gear 4 side of the crescent 54 in the third region. In the region on the pinion 3 side, no pressure transmission oil passage is formed.

As is apparent from the study of the inventors of the present application, even if there is no pressure transmission oil passage, the pressure of the space between the teeth of the pinion 3 is relatively high, which is equal to or higher than the pressure on the ring gear 4 side in the case where the pressure transmission oil passage 91 is formed. The pressure fluctuation when the space between the teeth of the pinion 3 opens to the ejection passage 12 is relatively small. This is because the crescent 54 has a structure in which the first arcuate wall 541 and the second arcuate wall 542 are immovable, and a slight gap exists between the tooth tip of the pinion 3 and the first arcuate wall 541. On the pinion 3 side, fluid leakage occurs from the ejection passage 12 through the gap to the space between the teeth of the pinion 3. As a result, in the third region, the pressure of the space between the teeth of the pinion 3 is relatively high.

Since the pressure of the space between the teeth of the pinion 3 is relatively high, the pressure of the space does not rise further even if a pressure transmission oil passage is formed in the area on the pinion 3 side. The noise suppression effect of the internal gear pump 1 is hardly improved. On the other hand, if the pressure transmitting oil passage is formed, the fluid leakage increases accordingly. The pump efficiency of the internal gear pump 1 may be lowered.

In the internal gear pump 1, the pressure transmission oil passage 91 is formed only in the region on the ring gear 4 side and the pressure transmission oil passage is not formed in the region on the pinion 3 side in the housing. The noise of the internal gear pump 1 can be suppressed, and the pump efficiency can be improved.

The preferred length of the pressure transmission oil passage 91 will be discussed below. Here, the length of the pressure transmission oil passage 91 is determined according to which position of the third region in the housing 10 the tip end of the pressure transmission oil passage 91 is located. The length of the pressure transmission oil passage 91 referred to herein is not a length extending along the linear pressure transmission oil passage 91.

As described above, the pressure transmission oil passage 91 has the following functions: before the space between the teeth of the ring gear 4 communicates with the ejection passage 12, the pressure of the space is increased. If the pressure transmission oil passage 91 is too short, it is difficult to raise the pressure of the space between the teeth of the ring gear 4 in advance before the space communicates with the ejection passage 12. There is one shortest length of the pressure transmission oil passage 91 for the pressure transmission oil passage 91 to function.

Specifically, as shown in fig. 3, the tip end of the pressure transmission oil passage 91 is located at a position at an angle θ1 or more from the edge of the discharge passage 12 with the rotation axis C2 of the ring gear 4 as the center, and the angle θ1 corresponds to the tooth width TW of the ring gear 4. If the pressure transmission oil passage 91 extends to a position at or above the angle θ1, the pressure transmission oil passage 91 can pass over at least one tooth of the ring gear 4, causing the space between the discharge passage 12 and the tooth to communicate with each other. The pressure transmission oil passage 91 can supply high-pressure hydraulic oil to the space between the teeth before the space reaches the discharge passage 12. That is, the pressure transmission oil passage 91 can raise the pressure of the space between the teeth of the ring gear 4 in advance before the space communicates with the discharge passage 12.

Making the pressure transmitting oil passage 91 longer is advantageous in increasing the pressure of the space between the teeth of the ring gear 4. However, when the pressure transmission oil passage 91 is long to some extent, the pressure transmission oil passage 91 continues to be lengthened, and the pressure of the space between the teeth does not rise. On the other hand, the longer the pressure transmission oil passage 91, the more fluid in the casing 10 leaks. Then, the tip end of the pressure transmission oil passage 91 is located in a range of an angle θ2 or less from the edge of the discharge passage 12 to the intermediate position of the crescent 54. The tip of the illustrated pressure transmission oil passage 91 is located at the intermediate position of the crescent 54. The intermediate position of the crescent 54 is a circumferentially intermediate position of the crescent 54 extending circumferentially from the discharge passage 12 to the suction passage 11. By preventing the pressure transmission oil passage 91 from becoming excessively long, the pressure in the space between the teeth of the ring gear 4 can be sufficiently increased, and an increase in fluid leakage can be suppressed.

(variant of pressure-transmitting oil passage)

In the internal gear pump 1 shown in fig. 1, the pressure transmission oil passage 91 is formed on the second support surface 61 of the front cover 6. The pressure transmitting oil passage 91 may also be formed recessed from the first support surface 52 of the gear housing 5. The pressure transmitting oil passage 91 may also be formed on the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5, respectively.

The pressure transmission oil passage is not limited to a straight line. Fig. 4 shows a curved pressure transmission oil passage 92. As with the pressure transmission oil passage 91, a pressure transmission oil passage 92 is formed on the second support surface 61 of the front cover 6. The pressure transmission oil passage 92 of fig. 4 is also shown by projecting the pressure transmission oil passage 92 formed in the front cover 6 onto the gear housing 5, as in fig. 3.

The pressure transmission oil passage 92 extends in an arc shape along the curve of the second arc wall 542 of the crescent 54. When viewed in the direction of the rotation axis C2 of the ring gear 4, the pressure transmission oil passage 92 coincides with the space between the teeth of the ring gear 4. The pressure transmitting oil passage 92 communicates with the spaces between the teeth of the ring gear 4. Since the pressure of the space between the teeth of the ring gear 4 increases in the third region, the pressure difference between the pressure of the ejection passage 12 and the pressure of the space between the teeth is small when the space is opened to the ejection passage 12. Noise of the internal gear pump 1 is suppressed.

The circular arc shape of the pressure transmission oil passage 92 shown in fig. 4 is only an example. The curved pressure transmission oil passage 92 is not limited to the circular arc shape. The depth of the pressure transmission oil passage 92 may be gradually reduced as it is farther from the discharge passage 12, or may be constant. The width of the pressure transmission oil passage 92 may be gradually narrowed as it is farther from the discharge passage 12, or may be constant. The position of the tip end of the pressure transmission oil passage 92 can be arbitrarily set within the range of θ1 to θ2. The pressure transmitting oil passage 92 may be formed on the first support surface 52 of the gear housing 5 instead of being formed on the second support surface 61 of the front cover 6, or on the first support surface 52 of the gear housing 5 on the basis of being formed on the second support surface 61.

In addition, the pressure transmitting oil passage formed on the first support surface 52 and/or the second support surface 61 may also be bent in the middle thereof.

The pressure transmitting oil passage is not limited to being formed on the first support surface 52 and/or the second support surface 61. Fig. 5 is a perspective view of the internal gear pump 1 with the front cover 6 removed. The internal gear pump 1 has a pressure transmission oil passage 93 formed in the crescent 54.

The pressure transmission oil passage 93 is formed at the upper end of the second circular arc wall 542 of the crescent 54. The pressure transmission oil passage 93 is formed by cutting a notch in the surface of the crescent 54. The upper end here is an end of a crescent 54 provided upright from the first support surface 52 of the gear housing 5 on the opposite side of the first support surface 52. The upper end of the second circular arc wall 542 is an end portion that abuts against the second support surface 61 of the front cover 6.

The pressure transmission oil passage 93 extends from the high-pressure side end portion (i.e., the left end in fig. 5) of the crescent 54 to the intermediate position of the crescent 54. The pressure transmission oil passage 93 communicates with the discharge passage 12 that opens on the second support surface 61 of the front cover 6. The length of the pressure transmission oil passage 93 may be arbitrarily set within the range of θ1 to θ2. In the configuration example of fig. 5, the width/depth of the pressure transmission oil passage 93 becomes gradually narrower/shallower as it gets farther from the ejection passage 12. The width/depth of the pressure transmission oil passage 93 may also be constant.

As with the pressure transmission oil passages 91, 92, the pressure transmission oil passage 93 formed in the crescent 54 also communicates the space between the teeth of the ring gear 4 with the discharge passage 12. Since the pressure of the space between the teeth of the ring gear 4 increases in the third region, the pressure difference between the pressure of the ejection passage 12 and the pressure of the space between the teeth is small when the space is opened to the ejection passage 12. Since the pressure fluctuation is suppressed, noise of the internal gear pump 1 is suppressed.

The pressure transmission oil passage formed in the crescent 54 is not limited to the one formed in the upper end of the crescent 54. The pressure transmission oil passage may be formed at an intermediate position in the up-down direction of the second circular arc wall 542 of the crescent 54. The pressure transmission oil passage may be formed at the lower end of the crescent 54.

Symbol description-

1 internal gear pump

10. Shell body

11. Suction passage

12. Ejection passage

3 pinion gear

31 external teeth

4 gear ring

41. Internal teeth

42. An outer peripheral surface

43. First side surface

44. Second side surface

5 Gear case (Shell)

51. Sliding surface

52. A first bearing surface

54. Crescent member

541. First circular arc wall

542. Second circular arc wall

Front cover 6 (Shell)

61 second bearing surface

8 high-pressure oil supply part

81. Introduction port

91. Pressure transmission oil circuit

92. Pressure transmission oil circuit

93. Pressure transmission oil circuit

C2 axis of rotation.

Claims

1. An internal gear pump, characterized in that:

the internal gear pump comprises a pinion, a gear ring, a shell and a crescent part,

the pinion gear has an external tooth that is externally toothed,

the ring gear has internal teeth engaged with the external teeth,

2. The internal gear pump of claim 1, wherein:

the housing has a sliding surface for sliding an outer peripheral surface of the ring gear,

3. The crescent gear pump of claim 1 or 2, wherein:

the shell is provided with a first supporting surface and a second supporting surface,

the first bearing surface and the second bearing surface respectively support the side surfaces of the gear ring, namely, two side surfaces orthogonal to the rotation axis of the gear ring,

4. The crescent gear pump of claim 1 or 2, wherein:

the pressure transmission oil passage is formed recessed from the second circular arc wall of the crescent member.

5. The crescent gear pump of claim 1 or 2, wherein:

the tip end of the pressure transmission oil passage is located within a range of an angle θ1 or more and an angle θ2 or less from an edge of the discharge passage, the angle θ1 corresponding to a tooth width of the ring gear, and the angle θ2 being an angle between an edge of the discharge passage and an intermediate position of the crescent extending from the discharge passage to the suction passage, the range being centered on a rotation axis of the ring gear.