JP2004028006A - Internal gear-type oil pump and automatic transmission comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the abrasion between a driven gear of an internal gear-type oil pump and an inner peripheral face of a storage recessed part for storing the driven gear, and the failure in operating the oil pump. <P>SOLUTION: A driving gear 30 of external teeth and a driven gear 31 of internal teeth engaged with each other, are mounted in a gear chamber G defined in a casing H, and the operating oil is sucked from suction ports 20a, 20b and discharged from a discharge port 25a. Two communication passages 28 are formed separately from each other in the circumferential direction of an inner peripheral face of the gear chamber for introducing the discharge pressure in the discharging port to a recessed groove 27 formed at a discharging port side of the inner peripheral face of the gear chamber, and the communication passages are respectively formed at both end parts in the circumferential direction of the recessed groove to allow the operating oil to flow through the recessed groove. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an internal gear oil pump that supplies hydraulic oil to an automatic transmission of an automobile.
[0002]
[Prior art]
As shown in FIGS. 5 and 6, this type of internal gear type oil pump includes a pump body 1 having a housing recess 2 and a pump chamber 3 formed by a pump cover 3 which covers the pump body 1 in a liquid-tight manner. There is a drive gear 30 that houses a drive gear 30 and a driven gear 31 having internal teeth that mesh with the drive gear 30. The inner surfaces of the pump body 1 and the pump cover 3 are positioned at positions corresponding to a suction area in which the volume of the working chamber R formed between the teeth as the gears 30 and 31 mesh with each other rotates gradually increases. A pair of suction ports 4a and 4b facing each other are opened, and a discharge port 6a and a balance groove 6b facing each other are opened at positions corresponding to a discharge region where the volume of the working chamber R gradually decreases. The suction passage 5 and the discharge passage 7 are provided in the discharge port 4b and the discharge port 6a, respectively. The drive gear 30 is supported at the tip of the input shaft 8 supported by the center hole of the pump body 1 via the bearing bush 9, and has a key 30 a protruding from the inner surface of the drive gear 30 formed at the tip of the input shaft 8. The driven gear 31 engaged with and engaged with the key groove 8 a is rotatably supported by the inner peripheral surface of the housing recess 2.
[0003]
In this internal gear oil pump, when both gears 30 and 31 are driven to rotate by the input shaft 8, the hydraulic oil in the suction ports 4a and 4b is sucked into the working chamber R in the suction area, and the hydraulic oil in the discharge area. It is discharged from a certain working chamber R into the discharge port 6a. Although the pressure of the hydraulic oil in the suction ports 4a and 4b is atmospheric pressure, the pressure in the discharge port 6a becomes a considerable discharge pressure, so that the range corresponding to the discharge port 6a of the driven gear 31 is radially outward. The force P1 acts, and there is a problem that the force P1 causes frictional resistance between the outer peripheral surface of the driven gear 31 and the inner peripheral surface of the housing recess 2, resulting in power loss. In order to cope with this, an arc-shaped concave groove 2a (see a two-dot chain line in FIG. 6) is formed in a range corresponding to the discharge port 6a on the inner peripheral surface of the accommodation recess 2, and the discharge port is formed by one communication passage 2b. A technique is known in which the discharge pressure within 6a is introduced to generate a force P3 having the same magnitude in the opposite direction to the force P1 and canceling the force P1 to eliminate power loss (for example, Japanese Utility Model Application Laid-Open No. 63-182). Reference).
[0004]
[Problems to be solved by the invention]
In the internal gear type oil pump disclosed in Japanese Utility Model Laid-Open Publication No. 63-182, the number of communication passages 2b for introducing discharge pressure into the concave groove 2a formed on the inner peripheral surface of the housing concave portion 2 is one. There is no flow of the hydraulic oil flowing through the inside of the groove 2a, so that foreign matter such as dust entering the groove 2a is not collected and removed inside. For this reason, such foreign matter enters between the inner peripheral surface of the housing recess 2 and the outer peripheral surface of the driven gear 31 which slide with each other, and wears both peripheral surfaces, and also causes malfunction of the internal gear oil pump, In the worst case, there is a problem that gear seizure may occur.
[0005]
An object of the present invention is to solve each of these problems by forming a communication path for introducing discharge pressure at a plurality of locations apart from each other in a groove so that hydraulic oil flows through the groove. .
[0006]
[Means for Solving the Problems]
The internal gear oil pump according to the present invention is provided with a casing in which a gear chamber having a suction port and a discharge port is formed, and is disposed in the gear chamber so as to mesh with each other. The external gear drive gear and the internal gear driven gear discharged from the port, and the inner peripheral surface of the gear chamber that slides on the outer peripheral surface of the driven gear at a position on the discharge port side along the circumferential direction of the inner peripheral surface. An internal gear oil pump having a concave groove formed and configured to receive a discharge pressure in a discharge port, wherein a plurality of communication paths for introducing the discharge pressure in the discharge port into the concave groove are formed. It is assumed that.
[0007]
In the internal gear oil pump described in the preceding paragraph, it is preferable that the communication passage is formed at two places.
[0008]
In the internal gear type oil pump described in the preceding paragraph, it is preferable that the communication passage is formed at two places separated from each other by a predetermined distance in a circumferential direction of the inner peripheral surface of the gear chamber.
[0009]
In the internal gear type oil pump described in the preceding two paragraphs, it is preferable that each communication passage is formed at both circumferential ends of the concave groove.
[0010]
The internal gear type oil pump described in the preceding paragraphs is characterized in that the casing comprises a pump body having a housing recess forming a gear chamber, and a pump cover fixedly connected to the pump body. The pump and the cover are made of different materials, and the communication passage is preferably formed on the inner surface of the pump body and the pump cover which has lower wear resistance, cavitation resistance or cavitation erosion resistance.
[0011]
In the internal gear oil pump described in the preceding paragraph, the pump body is preferably made of iron, the pump cover is made of a light alloy, and the communication passage is preferably formed on the inner surface of the pump cover.
[0012]
In the internal gear oil pump described in each of the claims except for the preceding two items, it is preferable that a part of the communication passage is formed on the inner surface of the pump body 10 and the remaining communication passage is formed on the inner surface of the pump cover 15.
[0013]
An automatic transmission according to the present invention includes the internal gear oil pump described in each of the preceding items.
[0014]
Function and Effect of the Invention
According to the internal gear type oil pump of the present invention, since the communication path for introducing the discharge pressure in the discharge port into the concave groove is formed at a plurality of locations, the hydraulic oil from the discharge port is supplied from some of the communication paths to the concave groove. , And comes out of a part of the communication path remaining through the inside of the concave groove, and the possibility that foreign matters are accumulated in the concave groove is reduced. Therefore, the risk of such foreign matter entering between the inner peripheral surface of the accommodating concave portion and the outer peripheral surface of the driven gear and causing the outer peripheral surface of the driven gear to wear, and causing malfunction of the internal gear oil pump is reduced. I do.
[0015]
According to the internal gear type oil pump in which the communication passage is formed at two locations, the hydraulic oil from the discharge port enters the groove from one communication passage and exits from the other communication passage through the groove. As in the case of the internal gear oil pump described in the preceding paragraph, foreign matter enters between the inner peripheral surface of the housing recess and the outer peripheral surface of the driven gear and wears both peripheral surfaces, and may cause malfunction of the internal gear oil pump. It decreases.
[0016]
According to the internal gear type oil pump in which the communication passage is formed at two locations spaced apart from each other by a predetermined distance in the circumferential direction of the inner peripheral surface of the gear chamber, a part or the other of the part or the other that enters from the one or one of the communication passages Since the distance through which the hydraulic oil from the communication passage passes through the concave groove is increased, the possibility that foreign matter is accumulated in the concave groove is greatly reduced. Therefore, the risk of foreign matter entering between the inner peripheral surface of the housing recess and the outer peripheral surface of the driven gear to wear the two peripheral surfaces and causing malfunction of the internal gear oil pump is greatly reduced.
[0017]
According to the internal gear type oil pump in which each communication path is formed at both ends in the circumferential direction of the groove, the hydraulic oil that enters from one communication path and exits from the other communication path flows through almost the entire length in the groove. Therefore, there is almost no possibility that foreign matter is accumulated in the concave groove. Therefore, there is almost no possibility that foreign matter enters between the inner peripheral surface of the accommodation concave portion and the outer peripheral surface of the driven gear to wear the two peripheral surfaces or to cause malfunction of the internal gear oil pump.
[0018]
A pump body for accommodating recess which forms a casing gear chamber is formed, with which shall become the pump cover coupled fixed to the pump body, and that different materials of the pump body and the pump cover together, communication passage wear resistance of the Po Npubode and pump cover, according to the internal gear oil pump which is formed on the inner surface having the lower cavitation resistance or resistance to cavitation erosion resistance, the driven gear is communication passage formed by the discharge pressure in the communicating passage The pump body or the pump cover, which is pressed against the pump body or the pump cover side that is not formed and forms the communication path, does not need to consider the above-described tolerances, and thus the material can be easily selected.
[0019]
The pump body is made of iron, the pump cover is made of light alloy, and the communication passage is formed by the internal gear type oil pump formed on the inner surface of the pump cover.The driven gear is driven by the discharge pressure in the communication passage formed on the inner surface of the pump cover. Since the force pressed against the pump body side and the pressure pressed against the pump cover side decreases, erosion due to wear and cavitation of the light alloy pump cover is prevented.
[0020]
According to the internal gear type oil pump formed on the inner surface of the pump body, some of the communication passages are formed on the inner surface of the pump body. According to the internal gear type oil pump formed on the inner surface of the pump cover, the force due to the discharge pressure in each communication passage is applied to the driven gear from both sides. Therefore, the inclination of the driven gear due to the discharge pressure in the communication passage is reduced as compared with the case where each communication passage is formed only on one side. Therefore, it is possible to prevent an increase in frictional resistance and uneven wear due to such an inclination.
[0021]
According to the automatic transmission provided with each of the internal gear type oil pumps described above, the effects described above can be obtained also as an automatic transmission.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described below with reference to the embodiment shown in FIGS. The internal gear oil pump according to this embodiment supplies hydraulic oil to an automatic transmission of an automobile. The internal gear oil pump mainly includes a drive gear 30, a driven gear 31 having internal teeth meshed with the drive gear 30, and both gears 30, 31. The housing H includes a housing H in which a rotatable gear chamber G is formed. The housing H is formed by a pump body 10 and a pump cover 15 joined to each other. The automatic transmission is composed of a torque converter 35 having a pump impeller 36, a turbine runner 37 and a stator 38, and a planetary gear type multi-stage transmission mechanism, but the description of the multi-stage transmission mechanism is omitted except for the input shaft 40. It is.
[0023]
As shown mainly in FIG. 1, a circular recessed recess 11 having a constant depth is formed on one flat side surface of a pump body 10 made of cast iron for rotatably housing both gears 30, 31. A center hole 12 is formed in the inner bottom surface of the pump body 10 so as to be eccentric with respect to the center of the housing recess 11 by the same amount as the amount of eccentricity between the gears 30 and 31. The pump cover 15 made of aluminum is bolted to the pump body 10 so as to liquid-tightly cover the housing recess 11 in which the two gears 30 and 31 are housed by one flat side surface. A gear chamber G for accommodating both gears 30 and 31 is formed by 11.
[0024]
A tubular stator shaft 17 press-fitted and fixed to a center hole 16 formed in the pump cover 15 coaxially with the center hole 12 of the pump body 10 passes through the inside of the pump body 10 with a gap therebetween. I have. An impeller hub 36a of a pump impeller 36 of a torque converter 35 to which power of an engine (not shown) as a driving source is transmitted has a central tubular portion inserted between the stator shaft 17 and the central hole 12, and the center of the pump body 10 The bearing bush 13 fixed to the inner peripheral surface of the hole 12 is rotatably supported, and the space between the impeller hub 36 a and the pump body 10 is sealed by an oil seal 39. The input shaft 40 of the multi-stage transmission mechanism is rotatably supported by a bearing bush 18 fixed to the inner peripheral surface of the tip end of the stator shaft 17, and the turbine runner 37 is spline-fitted and attached to the tip of the input shaft 40. . Further, the stator 38 is supported at the tip end of the stator shaft 17 via a one-way clutch 38a.
[0025]
The external gear drive gear 30 and the internal gear driven gear 31 having one more tooth than this have the same thickness and have trochoid tooth teeth meshing with each other, and both sides thereof and the pump body 10 and Both inner surfaces of the gear chamber G formed by the pump cover 15 are relatively slidable and rotatable with a small gap that does not substantially leak the hydraulic oil. The drive gear 30 is fitted and supported on the distal end of the impeller hub 36a such that a pair of keys 30a protruding from the inner peripheral surface thereof engage with a pair of key grooves 36b formed at the distal end of the impeller hub 36a. It is designed to be driven to rotate. The outer peripheral surface of the driven gear 31 is rotatably fitted and supported on the inner peripheral surface of the housing recess 11. Note that the tooth profile between the two gears 30 and 31 is not limited to a trochoid, and an arbitrary one such as an involute or a cycloid can be used.
[0026]
As shown mainly in FIG. 2, the space between the gears 30, 31 and the inner surface of the gear chamber G is partitioned into a number of working chambers R along the outer periphery of the drive gear 30 by teeth that mesh with each other. The volume of the chamber R increases and decreases while moving with the rotation of the gears 30 and 31. A suction area in which the volume of the working chamber R gradually increases with the rotation is formed in a range extending from the contact position of the pitch lines of the gears 30 and 31 to 180 degrees in the rotation direction of the gears 30 and 31. A discharge region in which the volume of the working chamber R gradually decreases with rotation is formed in a range extending from the contact position to 180 degrees in a direction opposite to the rotation direction.
[0027]
As shown in FIGS. 1 and 2, the inner bottom surface of the housing recess 11 of the pump body 10 and the corresponding inner surface of the pump cover 15 have the shape and shape of the opening along a considerable angular range corresponding to the suction area. A pair of suction ports 20a, 20b having the same area are formed to face each other, and the inner and outer edges of each of the suction ports 20a, 20b substantially coincide with the root circles of the gears 30, 31 respectively. ing. Each of the suction ports 20a and 20b is connected to a suction passage 21 formed in the pump body 10 and the pump cover 15 for introducing hydraulic oil from a reservoir (not shown).
[0028]
Also, as shown in FIGS. 2 and 3, the inner bottom surface of the housing recess 11 and the corresponding inner surface of the pump cover 15 have the same opening shape and area along a considerable angle range corresponding to the discharge region. Discharge port 25a and balance groove 25b are formed to face each other. The inner and outer edges of the discharge port 25a and the balance groove 25b substantially coincide with the root circles of the gears 30, 31, respectively. The discharge port 25a communicates with a discharge passage 26 formed in the pump body 10 and the pump cover 15 to supply hydraulic oil to a supply destination. However, the balance groove 25b is made shallower than the discharge port 25a to avoid a fluid passage (not shown) formed in the pump cover 15, and is not communicated with the discharge passage 26.
[0029]
In this embodiment, a pair of suction ports 20a and 20b are provided in the pump body 10 and the pump cover 15, the discharge port 25a is provided only in the pump body 10, and a balance groove 25b facing the discharge port 25a is provided in the pump cover 15. However, the suction port may be provided in only one of the pump body 10 and the pump cover 15, and the discharge port may be provided in the pump cover 15 or the pump body 10 and the pump cover 15. It may be provided in both (in this case, the balance groove is not necessary).
[0030]
As shown in FIGS. 2 and 3, the inner circumferential surface of the housing recess 11 has a width in the axial direction of the housing recess 11 within a range substantially coincident with the discharge port 25 a and the balance groove 25 b along the circumferential direction. An arc-shaped concave groove 27 smaller than the depth is formed. At a position corresponding to both ends in the circumferential direction of the concave groove 27, the discharge pressure in the discharge port 25 a and the balance groove 25 b is introduced by a pair of communication passages 28 formed on the inner surface of the pump cover 15. It has become.
[0031]
In a state where the drive gear 30 is driven to rotate by the impeller hub 36a of the torque converter 35 and the internal gear oil pump is operated, the operating oil in the discharge port 25a which has reached the discharge pressure depends on the rotation direction of the two gears 30 and 31. It flows in the same direction, enters the concave groove 27 from one of the communication passages 28 on the downstream side through the working chamber R and the balance groove 25b, flows through the concave groove 27, and flows from the other communication passage 28 to the balance groove 25b and It returns to the upstream side in the discharge port 25a through the working chamber R. Since the hydraulic oil flows through the inside of the concave groove 27 in this manner, foreign matter does not accumulate in the concave groove 27, so that such foreign matter slides between the inner peripheral surface of the housing recess and the outer peripheral surface of the driven gear. As a result, there is no danger that these two peripheral surfaces will be worn away and the internal gear type oil pump will not operate properly. Further, a force P3 having the same magnitude in a direction opposite to the force P1 is applied to the driven gear 31 by the discharge pressure introduced into the concave groove 27, and the force P1 is also canceled out. Is also gone.
[0032]
In the embodiment described above, the communication paths 28 for introducing the discharge pressure in the discharge port 25a into the concave groove 27 via the working chamber R and the balance groove 25b are provided at both ends in the circumferential direction of the concave groove 27. In this way, the hydraulic oil that has entered from one of the communication passages 28 flows through substantially the entire length of the groove 27 in the circumferential direction and exits from the other communication passage 28, so that foreign matter may accumulate in the groove 27. This is extremely small, and there is a very small possibility that such foreign matter causes the inner peripheral surface of the housing concave portion and the outer peripheral surface of the driven gear 31 that are slid with each other to be worn and that the internal gear type oil pump malfunctions. However, the present invention is not limited to this, and each communication passage 28 for introducing the discharge pressure in the discharge port 25a into the concave groove 27 may be formed at two places spaced apart from each other by a predetermined distance in the circumferential direction. Even so, since the flow of the hydraulic oil flowing through at least a part of the groove 27 is obtained, the possibility that foreign matter accumulates in the groove 27 is greatly reduced as compared with the prior art having only one communication passage. The possibility that the inner peripheral surface of the housing recess and the outer peripheral surface of the driven gear 31 will be worn or that the operation of the internal gear oil pump will be poorly reduced is greatly reduced. Here, the predetermined interval is such an interval that the discharge pressure generated in the discharge port 25a causes a flow to occur in the concave groove 27 so that foreign matter does not accumulate. The concave groove 27 may be provided at three or more places.
[0033]
Further, in the above-described embodiment, the pump cover 15 that covers the cast iron pump body 10 in which the housing recess 11 is formed is made of aluminum in order to reduce the weight, and the pump cover 15 inside the discharge port 25a is provided via the working chamber R and the balance groove 25b. A communication passage 28 for introducing the discharge pressure into the groove 27 is formed on the inner surface of the pump cover 15. In this case, the driven gear 31 is configured to have abrasion resistance, cavitation resistance and resistance to resistance due to the discharge pressure in the communication passage 28. The force of pressing against the pump body 10 made of cast iron having high cavitation erosion properties and pressing against the aluminum pump cover 15 having low resistance described above is reduced, so that wear of the pump cover 15 and erosion due to cavitation are prevented. . However, the present invention is not limited to such materials, and the material composition of the pump body 10 and the pump cover 15 (usually a metal) is made different from each other, so that the wear resistance, cavitation resistance, and A communication passage 28 is formed on the inner surface of the pump body 10 or the pump cover 15 made of the material having the lower cavitation erosion property, and the driven gear 31 is formed on the pump body 10 or the pump cover 15 made of the material having the higher resistance. The same effect can be obtained by pressing.
[0034]
Conversely, the pump body 10 and the pump cover 15 may be made of the same material. In this case, a communication path may be formed on the pump body 10 side as shown by a two-dot chain line 28a in FIG. It may be provided on both the body 10 side and the pump cover 15 side. Alternatively, some of the communication passages 28 may be formed on the inner surface of the pump body 10, and the remaining communication passages 28 may be formed on the inner surface of the pump cover 15. According to the configuration in which the communication passages 28 are formed on the inner surfaces of both the pump body 10 and the pump cover 15 in this manner, the force due to the discharge pressure in each communication passage 28 is applied to the driven gear 31 from both sides, so that each communication passage 28 The inclination of the driven gear 31 due to the discharge pressure in the communication passage 28 is reduced as compared with the case where the driven gear 31 is formed on only one side, and it is possible to prevent an increase in frictional resistance and uneven wear due to such an inclination.
[0035]
In the above-described embodiment, in order to cancel the force P1 that pushes the driven gear 31 outward in the radial direction due to the discharge pressure applied to each working chamber R between the discharge port 25a and the balance groove 25b, the discharge port 25a Also, the case where the concave groove 27 is formed in a range substantially coincident with the balance groove 25b to introduce the discharge pressure has been described. However, as shown in FIG. 4, in addition to the force P1, the driven gear 31 has the ends of the suction ports 20a and 20b (ends on the rotation direction side of both gears 30 and 31) and the start of the discharge port 25a. A radially outwardly varying force Q1 is also applied therebetween. That is, the working oil sucked into each working chamber R between the teeth of the two gears 30 and 31 is substantially separated from the working chamber R between the end portions of the suction ports 20a and 20b and the start end of the discharge port 25a. In the range cut off from the ports, the pump body 1 and the pump cover 3 are confined between the teeth of the two gears 30, 31 and are compressed and the pressure rises sharply, so that the end portions of the suction ports 20a, 20b and the discharge port A radially outward force Q1 that periodically increases and decreases acts on a portion of the driven gear 31 between the start ends of the gears 25a. In order to also cancel the force Q1, the circumferential center of the concave groove 27 is closer to the center between the ends of the suction ports 20a and 20b and the start of the 251 than the center of the discharge port 25a in the circumferential direction. The direction of the resultant force Q2 between the force for pushing the driven gear 31 outward in the radial direction by the discharge pressure of the discharge port 25a and the force for pushing the driven gear 31 inward in the radial direction by the discharge pressure introduced into the concave groove 27 is determined as described above. What is necessary is just to turn to cancel the force Q1. The communication passages 28 formed at both ends in the circumferential direction of the groove 27 in the present invention can be applied to the case of the groove 27 as shown in FIG. Note that the magnitude of the resultant force Q2 is larger than the maximum value of the increasing / decreasing force Q1 so that the driven gear 31 is always pressed against the inner peripheral surface of the housing recess 11 by the resultant force Q2 regardless of the fluctuation of the force Q1. Is good.
[0036]
In the above-described embodiment, an example is described in which the present invention is applied to an internal gear oil pump that supplies hydraulic oil to an automatic transmission of an automobile. However, the present invention is not limited to this. It can be used as a supply source of hydraulic oil used in machines and various other devices.
[0037]
Further, in the above-described embodiment, the pump cover 15 that covers the cast iron pump body 10 in which the housing recess 11 is formed is made of aluminum in order to reduce the weight, and the pump cover 15 inside the discharge port 25a is provided via the working chamber R and the balance groove 25b. A communication passage 28 for introducing the discharge pressure into the groove 27 is formed on the inner surface of the pump cover 15. In this case, the driven gear 31 is configured to have abrasion resistance, cavitation resistance and resistance to resistance due to the discharge pressure in the communication passage 28. The force of pressing against the pump body 10 made of cast iron having high cavitation erosion properties and pressing against the aluminum pump cover 15 having low resistance described above is reduced, so that wear of the pump cover 15 and erosion due to cavitation are prevented. . However, the present invention is not limited to such materials, and both the pump body 10 and the pump cover 15 may be made of cast iron or iron, or may be made of aluminum if an appropriate composition is selected. It is also possible to implement as.
[Brief description of the drawings]
FIG. 1 is a sectional view showing the overall structure of an embodiment of an internal gear oil pump according to the present invention.
FIG. 2 is a sectional view taken along line 2-2 of FIG.
FIG. 3 is a partial sectional view taken along line 3-3 in FIG. 2;
FIG. 4 is a cross-sectional view corresponding to FIG. 2, showing a modified example of the groove of the embodiment shown in FIG. 1;
FIG. 5 is a sectional view corresponding to FIG. 1 of an example of an internal gear oil pump according to the related art.
FIG. 6 is a sectional view taken along line 6-6 in FIG. 5;
[Explanation of symbols]
10 pump body, 11 accommodation recess, 15 pump cover, 20a, 20b suction port, 25a discharge port, 27 groove, 28 communication path, 30 drive gear, 31 driven gear, G gear chamber , H ... casing.

Claims (8)

A casing in which a gear chamber having a suction port and a discharge port is formed; and a drive of external teeth that meshes with each other and is disposed in the gear chamber and that rotates to suck hydraulic oil from the suction port and discharge from the discharge port. A gear and a driven gear having internal teeth, and the discharge port formed along a circumferential direction of the inner peripheral surface at a position on the inner peripheral surface of the gear chamber that slides on the outer peripheral surface of the driven gear on the discharge port side. An internal gear oil pump comprising a concave groove into which the discharge pressure is introduced,
An internal gear oil pump, wherein a communication passage for introducing a discharge pressure in the discharge port is formed at a plurality of locations in the concave groove. 2. The internal gear oil pump according to claim 1, wherein the communication passage is formed at two positions. 3. The internal gear type oil pump according to claim 2, wherein the communication passage is formed at two locations spaced apart from each other by a predetermined distance in a circumferential direction of an inner peripheral surface of the gear chamber. Oil pump. 4. The internal gear oil pump according to claim 2, wherein the communication passages are formed at both circumferential ends of the concave groove. 5. The internal gear oil pump according to any one of claims 1 to 4,
The casing includes a pump body having a housing recess forming the gear chamber, and a pump cover coupled and fixed to the pump body, wherein the pump body and the pump cover are made of different materials.
The internal gear oil pump according to claim 1, wherein the communication passage is formed on an inner surface of the pump body and the pump cover which has lower wear resistance, cavitation resistance, or cavitation erosion resistance. The internal gear oil pump according to claim 5,
The pump body is made of iron, and the pump cover is made of light alloy,
The internal gear type oil pump, wherein the communication passage is formed on an inner surface of the pump cover. 5. The internal gear oil pump according to claim 1, wherein the part of the communication passage is formed on the inner surface of the pump body 10, and the remaining communication passage is formed on the inner surface of the pump cover 15. An internal gear oil pump characterized in that it is formed as follows. An automatic transmission comprising the internal gear oil pump according to any one of claims 1 to 7.

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