HK1094022B - An oil pump - Google Patents

Description

Oil pump

Technical Field

The present invention relates to an internal gear pump of an internal gear type, which minimizes and alleviates pressure fluctuations of a fluid sealed in each of interdental spaces formed by an inner rotor and an outer rotor while the fluid is transferred from a suction port to a discharge port, prevents erosion of the inside of the pump due to cavitation and erosion, and has a very simple structure.

Background

In such a pump, in the course of conveying fluid from the intake port to the discharge port, the volume of the inter-tooth chamber gradually changes due to the structure of the trochoid tooth profile, that is, the volume of the inter-tooth chamber increases and decreases during movement from the intake port to the discharge port, and the pressure of the fluid in the inter-tooth chamber also fluctuates.

In order to prevent such a problem that the fluid rapidly flows into the discharge port, there is a pump disclosed in patent document 1 in which a small port is formed on the discharge port side, and the small port is a shallow groove formed from the start end of the discharge port toward the suction port side.

Further, the inter-tooth chamber intersects with the small port and communicates with the discharge port via the small port, whereby the high-pressure fluid in the inter-tooth chamber is discharged to the discharge port via the small port little by little from before reaching the discharge port, and when the inter-tooth chamber reaches the discharge port, the fluid in the inter-tooth chamber does not rapidly flow into the discharge port, thereby preventing noise of the pump.

[ patent document 1 ] patent No. 2842450

However, as described above, in the inter-tooth chamber, the volume of the inter-tooth space increases and decreases and the pressure of the fluid sealed inside also fluctuates in the process of transferring the fluid from the suction port to the discharge port.

Further, the small port as disclosed in patent document 1 directly intersects with the interdental chamber moving toward the discharge port side, and at a moment when the small port communicates with the interdental chamber, a pressure variation occurs at the small port, and bubbles accumulated at the tooth bottom portion of the inner rotor are likely to be directly collapsed (burst), and at this time, the small port cannot completely cope with the hydraulic pressure variation, and an erosion phenomenon in which bubbles generated by cavitation are instantaneously collapsed (burst) may occur.

Although the fluid in the inter-tooth chamber for transferring the fluid to the discharge port can be prevented from rapidly flowing into the discharge port, the erosion phenomenon cannot be prevented, and therefore, there is a possibility that erosion (corrosion) occurs.

Disclosure of Invention

The present invention is directed to a structure for suppressing rapid pressure fluctuation in an interdental chamber for transferring a fluid from a suction port to a discharge port, thereby preventing erosion from occurring, and to a simple structure.

The invention of claim 1 solves the above problems by designing an oil pump including: an internal rotor, an external rotor which forms a small chamber together with the internal rotor and rotates, a suction port, a discharge port, a transfer side partition portion formed between an end portion of the suction port and a start end portion of the discharge port, and a shallow groove formed in the transfer side partition portion and communicating with the discharge port but not communicating with the suction port, the shallow groove not intersecting the small chamber at the transfer side partition portion and being located on an inner side than a locus circle of a tooth bottom portion of the internal rotor, a side surface gap being provided between the transfer side partition portion and rotor side surfaces of the internal rotor and the external rotor, and the shallow groove and the small chamber communicating via the side surface gap.

The invention according to claim 2 solves the above-described problems by designing an oil pump in which, in the above-described configuration, the interval between the outer edge of the shallow groove in the groove width direction and the locus circle of the tooth bottom portion caused by the rotation of the inner rotor is about 1mm or less, and the invention according to claim 3 solves the above-described problems by designing an oil pump in which, in the above-described configuration, an outer shallow groove that communicates with the discharge port but does not communicate with the suction port is formed in the transfer side partition portion at a position further outside than the formation position of the shallow groove from the rotation center of the inner rotor, and the outer shallow groove intersects and communicates with the small chamber.

The invention of claim 4 solves the above problems by designing an oil pump in which the length of the outer shallow groove in the longitudinal direction is formed shorter than the shallow groove in the above configuration, and the invention of claim 5 solves the above problems by designing an oil pump in which the transfer side partition portion in which the shallow groove is formed is provided on both surfaces of the inner rotor and the outer rotor in the above configuration.

The invention according to claim 1 is an oil pump in which the inside of a chamber moving from a suction port to a discharge port at an inter-transfer-side partition portion communicates with a shallow groove via a side gap, wherein the volume of the chamber increases and the pressure of a fluid decreases to generate bubbles caused by cavitation in the process of the chamber moving from the suction port to the discharge port at the inter-transfer-side partition portion, and at this time, the fluid is replenished from the shallow groove through the side gap, whereby the inflow of the fluid into the chamber can be made gradually and slowly minute by minute amounts, and the pressure in the chamber also slowly and gently rises, so that the generated bubbles do not instantaneously collapse (burst) and the bubbles gradually disappear by the pressure of the gentle rise, and thus, the bubbles caused by cavitation are not instantaneously collapse (burst) due to pressure fluctuation, and the occurrence of erosion can be prevented, further, the durability of the pump can be improved and the life can be prolonged.

According to the invention of claim 2, since the distance between the outer edge of the shallow groove in the groove width direction and the trajectory circle of the tooth bottom portion caused by the rotation of the inner rotor is about 1mm or less, the flow of the fluid from the shallow groove to the cell becomes good, and the fluid can be easily replenished into the cell, and the invention of claim 3 is provided with the outer shallow groove in addition to the shallow groove, whereby bubbles generated in the fluid in the cell can be more reliably eliminated.

According to the invention of claim 4, from the initial stage to the middle stage of the transfer of the cell at the transfer-side partition, the pressure fluctuation due to the shallow grooves is reduced to eliminate the generated bubbles, and the fluid is gradually discharged to the discharge port side through the outer shallow grooves from the late stage of the transfer of the cell, whereby a very good pump operation can be realized, and next, according to the invention of claim 5, the supplemented fluid flows into the cell relatively quickly and in good balance by the side surface gap between the cell and the transfer-side partitions on both sides and the shallow grooves on both sides, whereby the bubbles can be eliminated, and a stable pump operation can be realized.

Drawings

FIG. 1A is a plan view of an embodiment of the present invention, and FIG. 1B is X of FIG. 1A₁-X₁To a cross-sectional view.

FIG. 2A is an enlarged plan view of the essential part of the present invention, and FIG. 2B is X of FIG. 2A₂-X₂To a cross-sectional view.

FIG. 3A is a plan view of a rotor chamber of a housing main body, and FIG. 3B is X of FIG. 3A₃-X₃To a cross-sectional view.

Fig. 4 is an enlarged plan view of the transfer-side partition portion of the case body portion.

Fig. 5A is a diagram showing a state where bubbles are generated in the cell at the transfer-side partition portion, fig. 5B is a diagram showing a state where the bubbles are gradually reduced by feeding the fluid from the shallow groove into the cell through the side surface gap, and fig. 5C is a diagram showing a state where the bubbles in the cell are eliminated.

Fig. 6A is a longitudinal sectional view of a main portion of a state in which bubbles are generated in the cell at the transfer-side partition portion and the fluid is fed into the cell from the shallow groove through the side gap, and fig. 6B is a longitudinal sectional view of a main portion of a state in which the pressure is gradually increased by the fluid fed into the cell and the bubbles are gradually reduced.

Fig. 7A is a plan view of an embodiment in which the shallow groove is separated from the locus circle as approaching the leading end portion of the discharge port, fig. 7B is a plan view of an embodiment in which the shallow groove is separated from the locus circle as approaching the leading end portion of the discharge port and the separated portion is linear, and fig. 7C is a plan view of an embodiment in which the shallow groove is separated from the locus circle as approaching the leading end portion of the discharge port and the separated portion is short.

Fig. 8 is a graph showing the pump characteristics of the present invention.

Fig. 9 is a longitudinal sectional view of a main portion of an embodiment in which a shallow groove is formed in the transfer side partition on the lid portion side.

Fig. 10A is a schematic cross-sectional view showing the positional relationship between the cell and the shallow groove of the present invention, fig. 10B is a vertical cross-sectional view of the cell, the shallow groove, and the main part of the side gap, and fig. 10C is a view showing a state where the air bubbles disappear.

Fig. 11A is a schematic cross-sectional view showing a positional relationship between a cell and a shallow groove in the conventional technology, fig. 11B is a longitudinal cross-sectional view of a main part of the cell, the shallow groove and a side gap, and fig. 11C is a view showing a state where a bubble is collapsed (burst).

Detailed Description

Next, an embodiment of the present invention will be described based on the drawings, and the oil pump of the present invention is, as shown in fig. 1A, an inner rotor 7 and an outer rotor 8 having trochoid tooth profiles are built in a rotor chamber 1 formed in a housing a, and fig. 2A is a housing body portion a of the housing a₁As shown in fig. 2A, the rotor chamber 1 has a suction port 2 and a discharge port 3 formed on its substantially outer periphery in its circumferential direction. The suction port 2 and the discharge port 3 are formed in the rotor chamber 1 in a left-right asymmetrical manner, or the suction port 2 and the discharge port 3 may be in a left-right symmetrical form.

As shown in fig. 1A, the number of teeth of the inner rotor 7 is one less than that of the outer rotor 8, and the outer rotor 8 rotates more slowly than the inner rotor 7 rotates once. As described above, the inner rotor 7 has the tooth profile portion 7a protruding outward and the tooth bottom portion 7b recessed inward, and similarly, the outer rotor 8 has the tooth profile portion 8a protruding toward the center side from the inner peripheral side and the concave tooth bottom portion 8 b. By the rotation of the inner rotor 7 and the outer rotor 8, tooth spaces called cells S are formed by the tooth portions 7a and 8a and the tooth bottoms 7b and 8 b.

In the suction port 2, the chamber S formed by the rotation of the inner rotor 7 and the outer rotor 8 moves, and the end portion when the chamber S first reaches the suction port 2 becomes the start end portion 2a of the suction port 2, and the end portion when the chamber S separates from the suction port 2 by the rotation becomes the end portion 2 b. Similarly, the discharge port 3 is moved by the rotation of the inner rotor 7 and the outer rotor 8, and the end of the cell S which first reaches the discharge port 3 becomes the start end 3A of the discharge port 3, and the end of the cell S which leaves the discharge port 3 by the rotation becomes the end 3B (see fig. 3A and 3B).

As shown in fig. 2A, 3A, and 4, a transfer-side partition portion 4 that partitions the suction port 2 and the discharge port 3 is formed between the terminal end portion 2b of the suction port 2 and the start end portion 3A of the discharge port 3. The transfer-side partition 4 is a region surrounded by a two-dot chain line in fig. 2A, and a region indicated by a two-dot chain line in fig. 3A, 3B, and 4. The transfer-side partition portion 4 is formed in a flat surface, and the transfer-side partition portion 4 functions to form a closed compartment (see fig. 1B) while the small chamber S formed by the inner rotor 7 and the outer rotor 8 transfers the fluid sucked through the suction port 2 to the discharge port 3, and the rotation direction of the inner rotor 7 and the outer rotor 8 is clockwise. In addition, when the formation positions of the suction port 2 and the discharge port 3 are arranged upside down, the rotation directions of the inner rotor 7 and the outer rotor 8 are counterclockwise.

The shell A comprises a shell main body part A₁And a cover part A₂The rotor chamber 1 is formed in the housing body A₁Middle (see fig. 3A). The case body A is provided with₁And a cover part A₂Both of them are formed with the transfer side partition 4 (see fig. 1B and 2B). accordingly, the small chamber S formed by the inner rotor 7 and the outer rotor 8 mounted in the rotor chamber 1 has both rotor side surfaces surrounded by the transfer side partition 4 and is substantially closed.

A side gap c may be provided between the rotor side surface 7s of the inner rotor 7 and the transfer-side partition 4, and a side gap c may be provided between the rotor side surface 8s of the outer rotor 8 and the transfer-side partition 4, in which case the rotor side surface 7s of the inner rotor 7 and the rotor side surface 8s of the outer rotor 8 are surfaces perpendicular to the outer peripheral surfaces thereof.

Therefore, when the inner rotor 7 and the outer rotor 8 are trochoid-tooth rotors, the outer peripheral surface of the inner rotor 7 is a tooth surface, and the outer peripheral surface of the outer rotor 8 is a circumferential side surface, and the side surface clearance C allows fluid to move between the small chamber S located in the transfer-side partition 4 and the shallow groove 5 described below. The width of the side surface clearance C is appropriately set according to the width and depth of the shallow groove 5 described below, and the respective dimensions are not limited.

Therefore, as the side surface clearance C, a clearance is usually provided in the housing a (housing body portion a) in order to smoothly rotate the inner rotor 7 and the outer rotor 8 in the rotor chamber 1 of the housing a, and this clearance is used as the side surface clearance C₁And a cover part A₂) And a gap between the inner portion and the inner side surface 7s of the inner rotor 7 and the rotor side surface 8s of the outer rotor 8. Further, the side surface clearance C may be designed to have a clearance dimension larger than the normal clearance.

In fact, the difference between the normal clearance and the clearance having a large clearance dimension is small, and the side clearance C needs to be fed into the small chamber S little by little and slowly although the fluid is to be circulated from the shallow groove 5 described later. This normal clearance is a clearance necessary for smooth rotation of the rotor.

Next, as shown in fig. 3A, 3B, 4, and the like, the transfer-side partition 4 is formed with a shallow groove 5. The shallow groove 5 is formed in the transfer-side partition 4 in a substantially linear or substantially rib-like shape from the start end 3a of the discharge port 3 toward the end 2b of the suction port 2. The shallow groove 5 communicates with the discharge port 3 but does not communicate with the suction port 2. The shallow grooves 5 are formed so as to be located inside a locus circle Q drawn by the tooth bottom portions 7B during the rotation of the inner rotor 7, and so as not to extend outside the locus circle Q, and the shallow grooves 5 are formed so as to be substantially parallel to the arc of the locus circle Q inside the locus circle Q (see fig. 2A, 3B, 4, and the like).

Here, the locus circle Q means the deepest part 7b of the tooth bottom 7b by the rotation of the inner rotor 7₁A circular trajectory formed by the movement (see fig. 1A and 2A), the shallow groove 5 does not intersect the cell S moving on the transfer-side partition 4 (see fig. 1A and 1B, and fig. 2A and 2B), that is, the shallow groove 5 does not enter the region of the transfer-side partition 4 where the cell S is formed, the center of the trajectory circle Q is the center of the boss hole portion 1A of the drive shaft 9 that pivotally supports the inner rotor 7, and the boss hole portion 1A is formed in the housing a.

Thus, as described above, as shown in FIG. 2B, the cell S and the shallow groove 5 communicate with each other only through the side surface clearance C, and fluid can flow from the shallow groove 5 into the cell S through the side surface clearance C, and the outer edge 5a, which is the outer edge in the groove width direction of the shallow groove 5, is formed at a position inside the locus circle Q and close to the locus circle Q (see FIG. 2A). therefore, the outer edge 5a is formed along the longitudinal direction of the shallow groove 5 (the direction from the starting end 3a of the discharge port 3 to the terminal end 2B of the suction port 2) and the deepest portion 7B of the tooth bottom portion 7B of the inner rotor 7₁The interval therebetween is set very small.

Specifically, the interval is preferably about several millimeters, and preferably within about 1mm, and therefore, even if the gap size of the side surface gap C is minimized, for example, a gap having a minimum gap width that can be designed is usually designed, since the interval between the shallow groove 5 and the locus circle Q of the tooth bottom of the inner rotor 7 constituting the chamber S is extremely short, the fluid can reach the chamber S relatively quickly and be replenished.

The distance between the locus circle Q and the outer edge 5a of the shallow groove 5 in the groove width direction is not limited to the above-mentioned value, and may be appropriately set by designing to 1mm or more depending on the size of the inner rotor 7 and the outer rotor 8 or the gap size of the side gap C, and the shape of the shallow groove 5 in the longitudinal direction may be formed in a circular arc shape, but may be designed in a straight line shape.

The longitudinal end of the shallow groove 5 is very close to the terminal end 2b of the suction port 2, and the cell S communicates with the shallow groove 5 through the side surface clearance C from the state where it reaches the transfer side partition 4 and the side surface of the cell S is surrounded by the transfer side partition 4. The side surface clearance C is a clearance between the inner rotor 7 and the outer rotor 8 and the transfer side partition 4, and the interval therebetween is very small, so that the flow rate of the fluid flowing from the side surface clearance C into the chamber S through the shallow groove 5 is small, but the fluid fed into the shallow groove 5 flows into the chamber S substantially uniformly and substantially simultaneously in the longitudinal direction of the shallow groove 5, and is a proper amount for smoothly increasing the pressure of the fluid in the chamber S (see fig. 5A to 5C and 6A to 6B).

In addition, since the fluid is gradually and slowly fed from the shallow groove 5 into the chamber S while the chamber S moves from the suction port 2 side to the discharge port 3 side at the transfer-side partition 4, the fluid in the discharge port 3 is replenished from the shallow groove 5 in accordance with the pressure of the fluid which fluctuates in pressure with the increase and decrease in volume of the chamber S moving at the transfer-side partition 4, and the replenishment is gradually and slowly performed little by little, the pressure rise is smooth, and many bubbles v generated in the fluid are not instantaneously collapsed (broken), and can be gradually reduced and eliminated.

This prevents the occurrence of erosion, and prevents erosion of the housing a, the inner rotor 7, and the outer rotor 8. as described above, the volume of the small chamber S gradually increases to reach the maximum volume and then gradually decreases while the transfer side partition 4 moves from the suction port 2 side to the discharge port 3 side, but the small chamber S is gradually replenished with fluid flowing through the shallow groove 5 and the side clearance C from the time when the internal fluid is in a negative pressure state before reaching the maximum volume (see fig. 5A to 5C).

The shallow groove 5 is usually formed in the case body a₁The side transfer side partition part 4 may be formed on the lid part A as required₂The shallow grooves 5 are also formed in the transfer-side partition 4, that is, the following structure is obtained: are respectively formed on the shell body part A₁The lid section A₂The upper transfer-side partitions 4 and 4 are formed with shallow grooves 5 and 5, respectively, and fluid flows into the chamber S from both side surfaces thereof through the shallow grooves 5 and the side surface gap C, C (see fig. 9). Further, the case body a may be₁The lid portion A is formed without forming the shallow groove 5 in the side transfer side partition portion 4₂The side transfer side partition 4 is formed with a shallow groove 5.

Next, as shown in fig. 3A, 3B and 4, the transfer side partition 4 is formed with an outer shallow groove 6, the outer shallow groove 6 is formed from the start end portion 3A of the discharge port 3 toward the end portion 2B of the suction port 2 in the transfer side partition 4, the outer shallow groove 6 communicates with the discharge port 3 and does not communicate with the suction port 2 at a position further outside the rotation center of the inner rotor than the formation position of the shallow groove 5, and the outer shallow groove 6 communicates with the formation region of the cell S as the cell S approaches the discharge port 3 in the transfer side partition 4 (see fig. 5C).

Further, the chamber S moves from the suction port 2 side to the discharge port 3 side at the transfer side partition 4, the volume of the chamber S decreases, the pressure of the fluid sealed inside increases, and the fluid is discharged from the outer shallow groove 6 to the discharge port 3 in accordance with the increase in the pressure, whereby the fluid in the chamber S does not rapidly flow into the discharge port 3 when the chamber S reaches the discharge port 3.

The outer shallow grooves 6 are formed to have a length in the longitudinal direction toward the intake port 2 side different from that of the shallow grooves 5 and shorter than the length in the longitudinal direction of the shallow grooves 5 (see fig. 1A, 3A, 4, and the like), that is, are configured as follows: the time when the shallow grooves 5 and the outer shallow grooves 6 start to operate differs, and the chamber S moving on the transfer-side partition 4 first enters a state where the fluid flows from the shallow grooves 5 through the side surface gaps C, and then gradually discharges the fluid in the chamber S from the outer shallow grooves 6 at a later time.

Next, a process of smoothly increasing the fluid pressure in the negative pressure state in the chamber S moving from the suction port 2 side to the discharge port 3 side in the transfer side partition 4 will be described with reference to fig. 5A to 5C, 6A, and 6B. First, the appropriate cell S reaches the transfer-side partition 4, and the periphery of both side surfaces of the cell S is closed by the transfer-side partition 4, and the pressure of the fluid at the discharge port 3 side is lower, and the fluid inside becomes a negative pressure, and bubbles v formed by cavitation are generated and accumulated in the tooth bottom 7b of the inner rotor 7 constituting the cell S (see fig. 5A and 6A). Since the fluid pressure in the chamber S is negative pressure, the fluid in the shallow grooves 5 enters the chamber S through the side surface gaps C (see fig. 5B), and then the pressure of the fluid in the chamber S at the negative pressure gradually increases with the movement of the chamber S toward the discharge port 3, and the air bubbles v gradually decrease and disappear without collapsing (bursting) (see fig. 5C and 6B).

First, the curve (1) is a negative pressure P obtained by sealing both sides of the cell S at the transfer-side partition 4₁In the section (1), the shallow groove 5 and the small chamber S communicate with each other via the side surface clearance C, and the fluid gradually flows into the small chamber S from the shallow groove 5 via the side surface clearance C, so that the pressure of the fluid in the small chamber S smoothly rises to reach the appropriate pressure P₂(see the thick line with a gentle angle).

Next, the position of (3) is a position where the cell S closed by the transfer-side partition 4 starts to communicate with the shallow outer tank 6, and the bubble v gradually disappears (instead of instantaneously collapsing (bursting)) due to the smooth pressure rise [ (1) to (3)), so that the breaking force of the bubble v due to cavitation (impact due to bursting) can be reduced. Further, many air bubbles v remaining in the vicinity of the tooth bottom of the inner rotor 7 disappear between the positions (1) to (3).

The broken line in the figure indicates the pressure fluctuation generated by the shallow groove 5 and the outer shallow groove 6, and at (2), the cell S communicating with the shallow groove 5 through the side surface clearance C at the transfer-side partitioning portion 4 starts communicating with the outer shallow groove 6 through the side surface clearance C when approaching the outer shallow groove 6. At this time, since the fluid pressure in the chamber S is communicated with the outer shallow grooves 6 in a state of gradually increasing due to the shallow grooves 5, the chamber S can be kept in a state of not rapidly changing the pressure (P) at the position (3)₃) The lower part is communicated with the outer shallow groove 6.

The present invention provides a shallow groove 5 for alleviating a rapid rise in fluid pressure, thereby preventing collapse (burst) of cavitation and improving the durability of a pump, and even if only the shallow groove 5 is provided, the present invention can eliminate the bubbles v generated by cavitation, and further, by providing the shallow groove 5 and the outer shallow groove 6 at the same time, the bubbles v generated in the fluid in the chamber S can be eliminated more reliably.

Further, it is preferable that the outer shallow grooves 6 intersect with the tooth bottom portions of the outer rotor 8 at the transfer side partition 4, and are formed so as to be spaced as far as possible from the locus circle Q, which is the position of the tooth bottom portions of the inner rotor 7, to the outer side thereof, and that, when the cell S communicates with the outer shallow grooves 6, the fluid is not required to be replenished from the shallow grooves 5, so that the shallow grooves 5 do not need to be present at the position of the tooth bottom circle of the inner rotor 7 near the movement path of the cell S.

As described above, the shape of the shallow groove 5 may be designed so as to be slightly apart from the locus circle Q as the shallow groove 5 approaches the start end portion 3a of the discharge port 3, first, as shown in fig. 7A. Fig. 7B shows an embodiment in which the shallow groove 5 is separated from the locus circle Q as it approaches the start end portion 3a of the discharge port 3 and the separated portion is linear, and fig. 7C shows an embodiment in which the shallow groove 5 is separated from the locus circle Q as it approaches the start end portion 3a of the discharge port 3 and the separated portion is particularly short.

In the present invention, although the transfer-side partition 4 is provided at a position corresponding to the lag angle, the present invention is not limited to this, and the shallow grooves 5 communicate with each other through the side surface clearance C when the small chamber S is closed by the transfer-side partition 4, but this includes a case where the shallow grooves 5 communicate with each other when the small chamber S reaches the maximum partition volume.

A comparison of the present invention with the prior art is shown in fig. 10A to 10C and fig. 11A to 11C, fig. 10A to 10C are the present invention, and fig. 11A to 11C are the prior art, in the present invention, as shown in fig. 10A, the case where the aforementioned cell S does not intersect with the aforementioned shallow groove 5 is shown, on the other hand, in the prior art, as shown in fig. 11A, the inside of the cell intersects with the shallow groove to directly communicate. In the present invention, as shown in fig. 10B, since the shallow grooves 5 communicate with the inside of the cell S through the side surface gaps C, the pressure fluid in the negative pressure state gradually flows from the shallow grooves 5 to the inside of the discharge port 3 through the side surface gaps C.

In addition, the negative pressure (-P) of the internal fluid slowly and smoothly changes to the positive pressure (+ P). Therefore, as shown in fig. 10C, the bubbles v receive pressure little by little from the surrounding fluid and are shrunk and gradually disappear, and in the conventional technique, as shown in fig. 11B, at the moment when the cell and the shallow groove intersect, pressure fluctuation occurs at the portion, and the negative pressure (-P) of the internal fluid rapidly changes to the positive pressure (+ P).

Therefore, as shown in FIG. 11C, the bubbles v are rapidly pressurized by the fluid and burst (burst), and the impact thereof causes erosion which causes impact damage to the rotor and the inside of the housing.

Claims (5)

1. An oil pump, comprising: an inner rotor, an outer rotor which forms a cell together with the inner rotor and rotates, an intake port, a discharge port, a transfer-side partition portion formed between an end portion of the intake port and a start end portion of the discharge port, and a shallow groove which is formed in the transfer-side partition portion, communicates with the start end portion of the discharge port, and does not communicate with the intake port, a longitudinal end of the shallow groove being close to the end portion of the intake port, does not intersect with the cell in the transfer-side partition portion, is located on an inner side than a locus circle of a tooth bottom portion of the inner rotor, is formed at a position close to the locus circle, side surface gaps are provided between the transfer-side partition portion and rotor side surfaces of the inner rotor and the outer rotor, and the shallow groove and the cell reach the transfer-side partition portion from the cell, Fluid flows into the small chamber through the side surface gap in a state where the side surface of the small chamber is surrounded by the transfer side partition.

2. An oil pump, comprising: an inner rotor, an outer rotor which forms a cell together with the inner rotor and rotates, a suction port, a discharge port, a transfer side partition portion formed between an end portion of the suction port and a start end portion of the discharge port, and a shallow groove formed in the transfer side partition portion and communicating with the discharge port but not communicating with the suction port, wherein an outer edge in a groove width direction of the shallow groove does not intersect with the cell at the transfer side partition portion and is located on an inner side of a trajectory circle of a tooth bottom portion of the inner rotor by about 1mm or less, a side surface gap is provided between the transfer side partition portion and rotor side surfaces of the inner rotor and the outer rotor, and the shallow groove and the cell communicate with each other through the side surface gap.

3. The oil pump according to claim 1 or 2, wherein an outer shallow groove communicating with the discharge port but not with the suction port is formed in the transfer side partition at a position further outside a position where the shallow groove is formed from a rotation center of the inner rotor, and the outer shallow groove intersects with and communicates with the small chamber.

4. The oil pump according to claim 3, characterized in that the length of the outer shallow groove in the longitudinal direction is formed shorter than the shallow groove.

5. The oil pump according to claim 1 or 2, wherein the transfer side partition portion forming the shallow groove is provided on both surfaces of the inner rotor and the outer rotor.