Internal gear pump

Abstract

The internal gear pump 100A includes the pump portion 10 configured to discharge the oil when the drive shaft 1 is rotated, and the housing 20A that accommodates the pump portion 10. The pump portion 10 has: the inner rotor 11 having the plurality of external teeth 11a and connected to the drive shaft 1; and the outer rotor 12 having the plurality of internal teeth 12a in sliding contact with the external teeth 11a, the outer rotor 12 being arranged outside the inner rotor 11. The internal gear pump 100A has: the first volume chamber R1 facing the outer circumference of the outer rotor 12 in the discharge region 66, the first volume chamber R1 having the restriction portion T formed to extend along the outer circumference, the first volume chamber R1 being configured such that the pressurized oil discharged from the pump portion 10 is guided to the first volume chamber R1; and the drain passage 50 configured to drain, from the first volume chamber R1, the oil passed through the restriction portion T.

Description

TECHNICAL FIELD

[0001] The present invention relates to an internal gear pump.BACKGROUND ART

[0002] JP6096545B discloses an oil pump including an oil guide groove that is formed at the same position in the circumferential direction as a discharge port in an inner peripheral surface of a portion of a housing facing an outer peripheral surface of an outer rotor and that communicates with a discharge passage. JP2008-1251A discloses a pump device in which an introduction groove for introducing pump discharge pressure is formed over a predetermined angular range in an inner peripheral surface of a cam ring. JP7-145785A discloses a trochoidal refrigerant compressor in which an oil groove for guiding pressurized lubricating oil is formed between a cylindrical bearing surface of a front housing and a sliding surface of an outer circumference of an outer rotor.SUMMARY OF INVENTION

[0003] In a discharge region of an internal gear pump, pump chambers partitioned by an inner rotor and an outer rotor pressurize liquid as they are contracted. Therefore, in the discharge region, an unbalanced load acts on the inner rotor and the outer rotor in directions in which the rotors move away from each other. As a result, the gear clearance between external teeth gears of the inner rotor and internal teeth gears of the outer rotor in a suction region may become smaller, causing a deterioration in sliding characteristics or an increase in torque.

[0004] The present invention has been made in view of such issue, and an object thereof is to suitably reduce an influence of the unbalanced load generated in the discharge region.

[0005] According to one aspect of the present invention, an internal gear pump is provided that includes a pump portion configured to discharge liquid when a drive shaft is rotated, and a housing accommodating the pump portion, the pump portion having: an inner rotor having a plurality of external teeth and connected to the drive shaft; and an outer rotor having a plurality of internal teeth in sliding contact with the external teeth, the outer rotor being arranged outside the inner rotor, wherein the internal gear pump has: a volume chamber facing an outer circumference of the outer rotor in a discharge region, the volume chamber having a restriction portion formed to extend along the outer circumference, the volume chamber being configured such that the liquid discharged from the pump portion is guided to the volume chamber; and a drain passage configured to drain, from the volume chamber, the liquid passed through the restriction portion.BRIEF DESCRIPTION OF DRAWINGS

[0006] [FIG. 1] FIG. 1 is a plan view of a pump portion of an internal gear pump according to an embodiment of the present invention. [FIG. 2] FIG. 2 is a plan view of the pump portion with a cover portion removed. [FIG. 3] FIG. 3 is a plan view showing a back surface of the cover portion. [FIG. 4] FIG. 4 is an enlarged view of a volume chamber. [FIG. 5] FIG. 5 is a plan view showing the back surface of the cover portion in a first modification. [FIG. 6] FIG. 6 is a plan view of the pump portion and a body portion in the first modification. [FIG. 7] FIG. 7 is a sectional view of the pump portion and the body portion in a second modification. [FIG. 8] FIG. 8 is an enlarged view of one modification of the volume chamber. [FIG. 9] FIG. 9 is an enlarged view of another modification of the volume chamber. [FIG. 10] FIG. 10 is a view showing one modification of a drain passage. DESCRIPTION OF EMBODIMENTS

[0007] Hereinafter, an internal gear pump according to an embodiment of the present invention will be described with reference to the drawings. The internal gear pump according to the embodiment of the present invention is mounted on, for example, a vehicle, and discharges coolant (liquid) for cooling an electric motor mounted on the vehicle or discharges oil (liquid) for lubricating gears mounted on the vehicle. The internal gear pump may be used as a fluid pressure source that discharges working fluid (liquid) for driving equipment. In addition, the internal gear pump may be mounted on industrial machinery other than vehicles. In this embodiment, a case in which oil serving as a viscous fluid is used as the liquid discharged by the internal gear pump will be described, but instead of oil, for example, an aqueous alternative fluid or the like may also be used.

[0008] An internal gear pump 100A according to this embodiment will be described with reference to FIGs. 1 to 4. FIGs. 1 and 2 are plan views of a pump portion 10 of the internal gear pump 100A, and FIG. 2 shows a plan view with a cover portion 40A removed (a plan view of the pump portion 10 and a body portion 30A of a housing 20A). FIG. 3 is a plan view showing a back surface of the cover portion 40A that covers the pump portion 10.

[0009] The internal gear pump 100A includes the pump portion 10 that discharges the oil when a drive shaft 1 is rotated, and the housing 20A that accommodates the pump portion 10. The arrow in FIG. 2 indicates the rotational direction of the drive shaft 1.

[0010] As shown in FIG. 2, the pump portion 10 has an inner rotor 11 to which the drive shaft 1 is coupled, and an outer rotor 12 that is arranged outside the inner rotor 11. The inner rotor 11 and the outer rotor 12 are accommodated in the housing 20A (specifically, in the body portion 30A described later), are provided eccentrically relative to each other, and are covered by the cover portion 40A of the housing 20A. Specifically, the inner rotor 11 is provided such that its center coincides with the center of the drive shaft 1, and the outer rotor 12 is provided such that its center is shifted downward from the drive shaft 1 in FIGs. 1 and 2. The inner rotor 11 has a plurality of external teeth 11a on an outer peripheral surface, and the outer rotor 12 has a plurality of internal teeth 12a, which are in sliding contact with the external teeth 11a, on an inner peripheral surface. The external teeth 11a and the internal teeth 12a are formed with different numbers of teeth, and each of pump chambers 13 is partitioned by adjacent external teeth 11a of the inner rotor 11 and the internal teeth 12a of the outer rotor 12. A plurality of pump chambers 13 are formed in the pump portion 10. Note that trochoidal curve tooth profiles are applied to the external teeth 11a of the inner rotor 11 and the internal teeth 12a of the outer rotor 12, but the invention is not limited thereto, and curve tooth profiles such as involute curves, cycloid curves, or the like may also be used.

[0011] As shown in FIGs. 1 and 3, the cover portion 40A is formed with a suction port 42 and a suction inlet 43 that guide the oil from outside to the pump chambers 13, and a discharge port 44 and a discharge outlet 45 that guide pressurized oil (liquid, pressurized liquid) discharged from the pump chambers 13 to outside. When the drive shaft 1 is rotated by a motor 15, the inner rotor 11 and the outer rotor 12 are rotated while the external teeth 11a of the inner rotor 11 slide against the internal teeth 12a of the outer rotor 12. As the inner rotor 11 and the outer rotor 12 are rotated, the volume of each pump chamber 13 is repeatedly expanded and contracted. In an expansion region where the pump chambers 13 are expanded (a suction region 65 described later), the oil is sucked through the suction port 42 and the suction inlet 43, and in a contraction region where the pump chambers 13 are contracted (a discharge region 66 described later), the oil is discharged and guided to outside through the discharge port 44 and the discharge outlet 45.

[0012] As shown in FIGs. 1 and 2, the housing 20A has the body portion 30A that accommodates the pump portion 10, and the cover portion 40A that is attached to the body portion 30A and covers the pump portion 10. The body portion 30A and the cover portion 40A are provided side by side in the axial direction of the drive shaft 1 (hereinafter also simply referred to as "the axial direction").

[0013] As shown in FIG. 2, the body portion 30A has a pump accommodating recessed portion 31 in which the pump portion 10 is accommodated. The pump accommodating recessed portion 31 is a recessed portion with a circular bottom surface, and the inner rotor 11 and the outer rotor 12 of the pump portion 10 are accommodated in the pump accommodating recessed portion 31 eccentrically to each other. Specifically, the center of the pump accommodating recessed portion 31 coincides with the center of the outer rotor 12 and is formed offset from the center of the drive shaft 1. A plurality of fastening holes 32 into which fastening members 70 (see FIG. 1) for attaching the cover portion 40A are respectively fastened are formed in an end surface 30a of the body portion 30A. The fastening members 70 are bolts. The fastening holes 32 are formed so as to correspond to insertion holes 47 (see FIG. 3) provided in the cover portion 40A.

[0014] As shown in FIGs. 1 and 2, the cover portion 40A is provided so as to cover the pump accommodating recessed portion 31 in which the inner rotor 11 and the outer rotor 12 are accommodated. The cover portion 40A is attached to the end surface 30a of the body portion 30A by the fastening members 70. The cover portion 40A has a disc-shaped cover body portion 41 attached to the end surface 30a, and a cylindrical projected portion 48 formed so as to project from the cover body portion 41 in the axial direction.

[0015] The cover body portion 41 is formed such that a region facing the inner rotor 11 and the outer rotor 12 protrudes in the axial direction. As shown in FIGs. 1 and 3, the cover body portion 41 is formed with: the suction port 42, the discharge port 44, and the suction inlet 43 described above; a shaft accommodating portion 46 in which a tip end portion of the drive shaft 1 is accommodated; and a plurality of insertion holes 47 through which the fastening members 70 are respectively inserted to fix the cover portion 40A to the body portion 30A. In addition, the projected portion 48 is formed with the above-described discharge outlet 45.

[0016] As shown in FIG. 3, the suction port 42 and the discharge port 44 are formed in a back surface of the cover body portion 41 so as to have an arc shape. The suction port 42 and the discharge port 44 are formed such that inner circumferences 42a and 44a are formed on a circle A1 centered on the drive shaft 1, and outer circumferences 42b and 44b are formed on a circle B1 centered on the outer rotor 12. A discharge-suction transition section 60 is formed between a front end portion 44c of the discharge port 44 and a rear end portion 42d of the suction port 42 in the rotational direction of the drive shaft 1, and a suction-discharge transition section 61 is formed between a front end portion 42c of the suction port 42 and a rear end portion 44d of the discharge port 44 in the rotational direction of the drive shaft 1. The cover body portion 41 is divided into a plurality of imaginary regions by a first imaginary line 62 passing through a midpoint of the discharge-suction transition section 60 and the center of the drive shaft 1, and a second imaginary line 63 perpendicular to the first imaginary line 62 and the drive shaft 1 and passing through the center of the drive shaft 1.

[0017] For example, the suction region 65 is a region (a planar region orthogonal to the axial direction) where the suction port 42 is formed and is a region on one side (the suction port 42 side) from the first imaginary line 62. In addition, the discharge region 66 is a region where the discharge port 44 is formed and is a region on the other side (the discharge port 44 side) from the first imaginary line 62. The suction port 42 and the discharge port 44 are formed symmetrically with respect to the first imaginary line 62.

[0018] The suction inlet 43 is formed to have an arc shape in a surface of the cover body portion 41 and communicates with the suction port 42. The suction inlet 43 is formed so that its entirety faces the suction port 42. The shaft accommodating portion 46 is formed to have a concave shape at the center of the back surface of the cover body portion 41. The tip end portion of the drive shaft 1 is accommodated inside the shaft accommodating portion 46, and the shaft accommodating portion 46 rotatably supports the drive shaft 1. The discharge outlet 45 is formed so as to penetrate through the projected portion 48 in the axial direction (see FIG. 1) and communicates with the discharge port 44. In the internal gear pump 100A, the projected portion 48 (see FIG. 1) is inserted into a hole portion (not shown) provided in equipment to which the internal gear pump 100A is attached, and the discharge outlet 45 is connected to a flow path (not shown). A suction passage 80 shown by a two-dot chain line is connected to the suction inlet 43, and the oil is sucked through the suction passage 80.

[0019] In the discharge region 66, the pump chamber 13 partitioned by the inner rotor 11 and the outer rotor 12 pressurizes the oil while being contracted. Therefore, in the discharge region 66, an unbalanced load F (see FIG. 2) acts on the inner rotor 11 and the outer rotor 12 in directions in which the inner rotor 11 and the outer rotor 12 move away from each other. As a result, in the suction region 65, a gear clearance between external teeth gears of the inner rotor 11 and internal teeth gears of the outer rotor 12 may become smaller, causing a deterioration in sliding characteristics or an increase in torque.

[0020] Therefore, the internal gear pump 100A is configured as described further below.

[0021] As shown in FIGs. 2 and 3, the internal gear pump 100A further has a first volume chamber R1 provided in the discharge region 66, an introduction passage 49 that guides the oil to the first volume chamber R1, and a drain passage 50 that drains the oil from the first volume chamber R1. Both the introduction passage 49 and the drain passage 50 are formed in a groove shape in the back surface of the cover portion 40A and are configured as passages in a state in which the cover portion 40A is arranged on the end surface 30a of the body portion 30A. In FIG. 2, the suction port 42, the discharge port 44, the introduction passage 49, and the drain passage 50, which are formed in the cover portion 40A, as well as the suction passage 80 are also shown by two-dot chain lines. In addition, in FIG. 3, the first volume chamber R1 and an outer circumference of the outer rotor 12 are also shown by two-dot chain lines. FIG. 4 shows the first volume chamber R1 in an enlarged state.

[0022] The introduction passage 49 communicates the discharge port 44 and the first volume chamber R1, and the pressurized oil discharged from the pump portion 10 is guided to the first volume chamber R1 through the introduction passage 49. The drain passage 50 communicates the first volume chamber R1 and the suction port 42, and the pressurized oil is drained from the first volume chamber R1 to the suction port 42 through the drain passage 50. The introduction passage 49 communicates with the first volume chamber R1 on one end side in the circumferential direction, and the drain passage 50 communicates with the first volume chamber R1 on the other end side in the circumferential direction. Therefore, in the first volume chamber R1, the pressurized oil guided from the discharge port 44 flows in a direction from the one end side to the other end side in the circumferential direction, in other words, the pressurized oil flows along the rotational direction of the drive shaft 1. The introduction passage 49 communicates with the discharge port 44 on the one end side in the circumferential direction, and the drain passage 50 communicates with the suction port 42 on the one end side in the circumferential direction.

[0023] As shown in FIGs. 2 and 4, the first volume chamber R1 is partitioned by the outer circumference of the outer rotor 12 and an inner circumference of the pump accommodating recessed portion 31 of the body portion 30A (a recessed portion 33 which will be described later), and is partitioned by a bottom surface of the pump accommodating recessed portion 31 and the cover portion 40A. The recessed portion 33 is formed in the inner circumference of the pump accommodating recessed portion 31 at a portion where the first volume chamber R1 is formed. The recessed portion 33 is formed to have a concave shape along the radial direction from the inner peripheral surface of the pump accommodating recessed portion 31, and a bottom surface 33a thereof is provided so as to extend along the direction orthogonal to the radial direction. The recessed portion 33 is provided so as to extend from the end surface 30a of the body portion 30A to the bottom surface of the pump accommodating recessed portion 31 in accordance with the thickness of the outer rotor 12 in the axial direction. The first volume chamber R1 extends along the circumferential direction, and a circumferential length thereof is set in consideration of a biasing force to be applied to the outer rotor 12 based on the pressurized oil in the first volume chamber R1. The first volume chamber R1 is formed along the outer circumference of the outer rotor 12 and faces the outer circumference of the outer rotor 12. A restriction portion T is formed in the first volume chamber R1 by the outer circumference of the outer rotor 12 and the bottom surface 33a of the recessed portion 33.

[0024] The restriction portion T is a portion with a minimum cross-sectional area (a minimum cross-sectional area portion) and its vicinity in the first volume chamber R1, and is formed along the outer circumference of the outer rotor 12 in a circumferentially central portion of the first volume chamber R1. The cross-sectional area is a cross-sectional area of a portion of the first volume chamber R1 along the radial direction that is sandwiched between the outer circumference of the outer rotor 12 and the bottom surface 33a of the recessed portion 33. The minimum cross-sectional area portion has a smaller cross-sectional area compared to an introduction side of the oil of the first volume chamber R1 and further has a smaller cross-sectional area compared to the oil drain side of the first volume chamber R1. The restriction portion T is formed so as to face the outer circumference of the outer rotor 12, and the biasing force based on the pressurized oil in the first volume chamber R1 including inside the restriction portion T acts on the outer rotor 12.

[0025] In the internal gear pump 100A configured as described above, the pressurized oil introduced into the first volume chamber R1 through the introduction passage 49 is drawn into the restriction portion T by the rotation of the outer rotor 12, thereby generating the wedge effect, and thus, the oil pressure is increased so as to be higher than the discharge pressure. Therefore, by biasing the outer rotor 12 against the unbalanced load F with the biasing force based on high oil pressure compared to the discharge pressure, an influence of the unbalanced load F generated in the discharge region 66 can be suitably reduced. In addition, the oil that has passed through the restriction portion T can be drained from the first volume chamber R1 through the drain passage 50.

[0026] The first volume chamber R1 is partitioned by the outer circumference composed of the circumferential surface of the outer rotor 12 and the bottom surface 33a composed of a flat surface of the recessed portion 33, and the outer circumference of the outer rotor 12 approaches the bottom surface 33a of the recessed portion 33 toward the restriction portion T from the introduction side of the oil of the first volume chamber R1. Therefore, the first volume chamber R1 has a shape in which the cross-sectional area is gradually decreased from the introduction side of the oil toward the restriction portion T. With such a configuration, the wedge effect can be effectively generated, and so, the influence of the unbalanced load F can be more suitably reduced. The first volume chamber R1 has a shape in which the cross-sectional area gradually increases from the restriction portion T toward the oil drain side.

[0027] The pressurized oil in the first volume chamber R1 that has passed through the restriction portion T is guided to the pump chambers 13 positioned in the suction region 65 through the drain passage 50 and the suction port 42. As a result, the oil pressure drop that may occur in the pump chambers 13 positioned in the suction region 65 is suppressed, and thus, generation of cavitation is also suppressed.

[0028] A recessed portion having a similar shape facing the suction port 42 may be provided in the bottom surface of the pump accommodating recessed portion 31, and the drain passage 50 may be formed in the body portion 30 to communicate the first volume chamber R1 and the recessed portion facing the suction port 42. Even with such a configuration, the pressurized oil in the first volume chamber R1 can be guided to the pump chambers 13 positioned in the suction region 65.(First Modification)

[0029] Next, an internal gear pump 100B according to a first modification will be described with reference to FIGs. 5 and 6. FIG. 5 is a plan view showing the back surface of a cover portion 40B of a housing 20B of the internal gear pump 100B. FIG. 6 is a plan view of the pump portion 10 and the body portion 30A of the housing 20B of the internal gear pump 100B. In FIG. 6, the suction port 42, the discharge port 44, the introduction passage 49, and a drain passage 51 formed in the cover portion 40B as well as the suction passage 80 are also shown by two-dot chain lines.

[0030] The first modification differs from the above-described embodiment in the configuration of the drain passage that drains the liquid from the volume chamber. In the first modification, the drain passage 51 is formed in the cover portion 40B, and as described below, the drain passage 51 communicates the first volume chamber R1 and the suction port 42 by connecting to the suction port 42 in an orientation along a direction S along a suction flow of the oil to the suction port 42. The drain passage 51 communicates with the suction port 42 at the center in the circumferential direction, and additionally, communicates with the suction port 42 at a position overlapping with the suction passage 80 in the axial direction.

[0031] The oil is sucked into the suction port 42 through the suction passage 80, and the suction flow of the oil to the suction port 42 is formed along an extending direction of the suction passage 80. Therefore, the direction S along the suction flow of the oil to the suction port 42 is, for example, a direction S1 along the extending direction of the suction passage 80 as viewed from the axial direction, and the drain passage 51 connects to the suction port 42 in the direction S1. With such a configuration, the flow of the oil drained from the drain passage 51 to the suction port 42 is suppressed from interfering with the suction flow to the suction port 42, and so, a pressure loss is suppressed.

[0032] The direction S along the suction flow may be a direction S2 or a direction S3 that intersects with the direction S1 at an acute angle α in the direction from the drain passage 51 side toward the suction port 42 side. The acute angle α can be set to, for example, less than 45 degrees. If the acute angle is less than 45 degrees, a vector component in the direction S1 along the extending direction of the suction passage 80 becomes larger than a vector component in the direction orthogonal to the direction S1, and so, the suction flow to the suction port 42 is less likely to be obstructed. From a viewpoint of suppressing obstruction of the suction flow to the suction port 42, a smaller acute angle α is preferable.

[0033] The oil sucked into the suction port 42 is subject to the force in the rotational direction of the drive shaft 1. Between the direction S2 and the direction S3, the direction S2 that forms the acute angle α in the direction approaching the suction port 42 with respect to the direction S1 becomes more along the rotational direction compared to the direction S3 that forms the acute angle α in the direction away from the suction port 42 with respect to the direction S1. Therefore, between the direction S2 and the direction S3, the direction S2 is less likely to obstruct the flow of the oil sucked into the suction port 42 and can be said to be preferable.(Second Modification)

[0034] Next, an internal gear pump 100C according to a second modification will be described with reference to FIG. 7. FIG. 7 is a plan view showing the pump portion 10 and a body portion 30B of a housing 20C of the internal gear pump 100C. In FIG. 7, the suction port 42, the discharge port 44, and an introduction passage 52 formed in a cover portion (not shown) of the housing 20C are also shown by two-dot chain lines.

[0035] The second modification differs from the above-described embodiment in a configuration of the volume chamber. In the second modification, the body portion 30B has a second volume chamber R2 that faces the outer circumference of the outer rotor 12. The second volume chamber R2 is partitioned by a recessed portion 34 formed in a recessed shape in the radial direction from the pump accommodating recessed portion 31, the outer circumference of the outer rotor 12, and the cover portion of the internal gear pump 100C, and has a rectangular cross-section orthogonal to the radial direction. The cross-section is set to a size that allows a ball 90 described later to slide, and a gap is formed between the second volume chamber R2 and the ball 90 by this cross-section. The pressurized oil is introduced, from the discharge port 44, into the second volume chamber R2 through the introduction passage 52 that communicates the discharge port 44 and the second volume chamber R2. The pressurized oil is introduced near a bottom surface (a wall surface 34a orthogonal to the radial direction of the recessed portion 34) of the second volume chamber R2.

[0036] In the second volume chamber R2, the pressurized oil introduced from the discharge port 44 acts directly on the outer rotor 12. Therefore, the drain passage 50 described in the above-described embodiment or the drain passage 51 described in the first modification is not required in the second volume chamber R2. An opening area of a portion of the second volume chamber R2 facing the outer rotor 12 is set in consideration of the biasing force to be applied to the outer rotor 12 based on the pressurized oil in the second volume chamber R2, and it may be set wider in the circumferential direction or in the radial direction compared to the above-described cross-section, for example.

[0037] The ball 90 and a spring 91 are accommodated in the second volume chamber R2. The ball 90 is provided facing the outer rotor 12, and the spring 91 is provided between the ball 90 and the wall surface 34a forming the bottom surface of the second volume chamber R2. The spring 91 is a biasing member and is accommodated in the second accommodation chamber R2 in a compressed state, thereby biasing the ball 90 toward the outer rotor 12.

[0038] In the internal gear pump 100C configured as described above, in addition to the biasing force based on the discharge pressure due to the pressurized oil guided into the second volume chamber R2, the biasing force opposing the unbalanced load F is generated by the biasing force exerted by the spring 91. Therefore, also in this case, because the outer rotor 12 can be biased against the unbalanced load F with the biasing force larger than the biasing force based on discharge pressure, the influence of the unbalanced load F can be suitably reduced. If the outer rotor 12 were to be biased only by the spring 91, either a sufficient biasing force could not be generated, or the size of the spring 91 would have to be increased, which would result in an increase in the size of the internal gear pump 100C or would make the installation of the spring 91 difficult.(Other Modifications)

[0039] Next, other modifications will be described with reference to FIGs. 8 to 10.

[0040] As shown in FIG. 8, the bottom surface 33a of the recessed portion 33 of the first volume chamber R1 may be, for example, an arc surface. In this example, the bottom surface 33a is formed by a gentle arc surface having a smaller curvature compared to a cylindrical surface of the outer circumference of the outer rotor 12. In this case as well, because the restriction portion T can be formed at the center of the first volume chamber R1 in the circumferential direction by the outer circumference of the outer rotor 12 and the arc-shaped bottom surface 33a, the wedge effect can be generated. In addition, because the first volume chamber R1 can be formed to have a shape in which the cross-sectional area is gradually decreased from the introduction side of the oil toward the restriction portion T, the wedge effect can be effectively generated.

[0041] As shown in FIG. 9, the restriction portion T of the first volume chamber R1 may be, for example, a portion in which the cross-sectional area is set smaller in a step-like manner compared to the introduction side of the oil of the first volume chamber R1. Even with such a restriction portion T, the wedge effect can be generated when oil is drawn in by the rotating outer rotor 12. In addition, the wedge effect may also be generated by providing multistage steps along the circumferential direction from the introduction side of the oil to gradually reduce the cross-sectional area.

[0042] As shown in FIG. 10, the first volume chamber R1 may communicate with the discharge port 44 through a drain passage 52 that communicates the first volume chamber R1 and the discharge port 44. Even with such a configuration, the pressure of the pressurized oil in the first volume chamber R1 is increased so as to become higher than the discharge pressure by the wedge effect when it is drawn into the restriction portion T, and so, it is possible to discharge the oil from the first volume chamber R1.

[0043] The configurations, operations, and effects of the embodiment of the present invention will be collectively described below.

[0044] The internal gear pump 100A includes the pump portion 10 configured to discharge the oil when the drive shaft 1 is rotated, and the housing 20A that accommodates the pump portion 10. The pump portion 10 has: the inner rotor 11 having the plurality of external teeth 11a and connected to the drive shaft 1; and the outer rotor 12 having the plurality of internal teeth 12a in sliding contact with the external teeth 11a, the outer rotor 12 being arranged outside the inner rotor 11. The internal gear pump 100A has: the first volume chamber R1 facing the outer circumference of the outer rotor 12 in the discharge region 66, the first volume chamber R1 having the restriction portion T formed to extend along the outer circumference, the first volume chamber R1 being configured such that the pressurized oil discharged from the pump portion 10 is guided to the first volume chamber R1; and the drain passage 50 configured to drain, from the first volume chamber R1, the oil passed through the restriction portion T.

[0045] According to this configuration, the wedge effect can be generated by drawing the pressurized oil into the restriction portion T by the rotating outer rotor 12, and the oil pressure of the pressurized oil guided to the first volume chamber R1 can be increased so as to be higher than the discharge pressure. Therefore, by biasing the outer rotor 12 against the unbalanced load F with the biasing force based on high oil pressure compared to the discharge pressure, the influence of the unbalanced load F generated in the discharge region 66 can be suitably reduced. In addition, the oil that has passed through the restriction portion T can be drained from the first volume chamber R1 via the drain passage 50.

[0046] The first volume chamber R1 has the shape in which the cross-sectional area is gradually decreased from the introduction side of the oil toward the restriction portion T.

[0047] According to this configuration, because the wedge effect can be effectively generated, the influence of the unbalanced load F can be more suitably reduced.

[0048] The drain passage 50 / the drain passage 51 communicates the first volume chamber R1 and the pump chambers 13 of the pump portion 10 positioned in the suction region 65.

[0049] According to this configuration, by guiding the pressurized oil in the first volume chamber R1 to the pump chambers 13 positioned in the suction region 65 through the drain passage 51, the oil pressure drop that may occur in the pump chambers 13 positioned in the suction region 65 can be suppressed, and so, it is possible to suppress the generation of cavitation.

[0050] The drain passage 51 is connected to the suction port 42 in the direction S along the suction flow of the oil to the suction port 42, the suction flow guiding the oil to the pump chambers 13.

[0051] According to this configuration, because the oil from the drain passage 51 is guided to the suction port 42 so as not to interfere with the suction flow of the suction port 42, it is possible to suppress the generation of pressure loss.

[0052] The internal gear pump 100C includes the pump portion 10 configured to discharge the oil when the drive shaft 1 is rotated, and the housing 20C that accommodates the pump portion 10. The pump portion 10 has: the inner rotor 11 having the plurality of external teeth 11a and connected to the drive shaft 1; and the outer rotor 12 having the plurality of internal teeth 12a in sliding contact with the external teeth 11a, the outer rotor 12 being arranged outside the inner rotor 11. The internal gear pump 100C has: the second volume chamber R2 facing the outer circumference of the outer rotor 12 in the discharge region 66, the second volume chamber R2 being configured such that the pressurized oil discharged from the pump portion 10 is guided to the second volume chamber R2; and the spring 91 accommodated in the second volume chamber R2, the spring 91 being configured to bias the outer rotor 12.

[0053] According to this configuration, the outer rotor 12 can be biased against the unbalanced load F by the biasing force exerted by the spring 91, in addition to the biasing force based on the discharge pressure due to the pressurized oil guided into the second volume chamber R2. Therefore, compared to a case in which the outer rotor 12 is biased only by the biasing force based on the discharge pressure, it is possible to suitably reduce the influence of the unbalanced load F.

[0054] Embodiments of this invention were described above, but the above embodiments are merely examples of applications of this invention, and the technical scope of this invention is not limited to the specific constitutions of the above embodiments.

[0055] This application claims priority based on Japanese Patent Application No.2023-098722 filed with the Japan Patent Office on June 15, 2023, the entire contents of which are incorporated into this specification.

Examples

first modification

(First Modification)

[0029]Next, an internal gear pump 100B according to a first modification will be described with reference to FIGs. 5 and 6. FIG. 5 is a plan view showing the back surface of a cover portion 40B of a housing 20B of the internal gear pump 100B. FIG. 6 is a plan view of the pump portion 10 and the body portion 30A of the housing 20B of the internal gear pump 100B. In FIG. 6, the suction port 42, the discharge port 44, the introduction passage 49, and a drain passage 51 formed in the cover portion 40B as well as the suction passage 80 are also shown by two-dot chain lines.

[0030]The first modification differs from the above-described embodiment in the configuration of the drain passage that drains the liquid from the volume chamber. In the first modification, the drain passage 51 is formed in the cover portion 40B, and as described below, the drain passage 51 communicates the first volume chamber R1 and the suction port 42 by connecting to the suction port 42 in an or...

second modification

(Second Modification)

[0034]Next, an internal gear pump 100C according to a second modification will be described with reference to FIG. 7. FIG. 7 is a plan view showing the pump portion 10 and a body portion 30B of a housing 20C of the internal gear pump 100C. In FIG. 7, the suction port 42, the discharge port 44, and an introduction passage 52 formed in a cover portion (not shown) of the housing 20C are also shown by two-dot chain lines.

[0035]The second modification differs from the above-described embodiment in a configuration of the volume chamber. In the second modification, the body portion 30B has a second volume chamber R2 that faces the outer circumference of the outer rotor 12. The second volume chamber R2 is partitioned by a recessed portion 34 formed in a recessed shape in the radial direction from the pump accommodating recessed portion 31, the outer circumference of the outer rotor 12, and the cover portion of the internal gear pump 100C, and has a rectangular cross-sec...

TECHNICAL FIELD

[0001] The present invention relates to an internal gear pump.BACKGROUND ART

[0002] JP6096545B discloses an oil pump including an oil guide groove that is formed at the same position in the circumferential direction as a discharge port in an inner peripheral surface of a portion of a housing facing an outer peripheral surface of an outer rotor and that communicates with a discharge passage. JP2008-1251A discloses a pump device in which an introduction groove for introducing pump discharge pressure is formed over a predetermined angular range in an inner peripheral surface of a cam ring. JP7-145785A discloses a trochoidal refrigerant compressor in which an oil groove for guiding pressurized lubricating oil is formed between a cylindrical bearing surface of a front housing and a sliding surface of an outer circumference of an outer rotor.SUMMARY OF INVENTION

[0003] In a discharge region of an internal gear pump, pump chambers partitioned by an inner rotor and an outer rotor pressurize liquid as they are contracted. Therefore, in the discharge region, an unbalanced load acts on the inner rotor and the outer rotor in directions in which the rotors move away from each other. As a result, the gear clearance between external teeth gears of the inner rotor and internal teeth gears of the outer rotor in a suction region may become smaller, causing a deterioration in sliding characteristics or an increase in torque.

[0004] The present invention has been made in view of such issue, and an object thereof is to suitably reduce an influence of the unbalanced load generated in the discharge region.

[0005] According to one aspect of the present invention, an internal gear pump is provided that includes a pump portion configured to discharge liquid when a drive shaft is rotated, and a housing accommodating the pump portion, the pump portion having: an inner rotor having a plurality of external teeth and connected to the drive shaft; and an outer rotor having a plurality of internal teeth in sliding contact with the external teeth, the outer rotor being arranged outside the inner rotor, wherein the internal gear pump has: a volume chamber facing an outer circumference of the outer rotor in a discharge region, the volume chamber having a restriction portion formed to extend along the outer circumference, the volume chamber being configured such that the liquid discharged from the pump portion is guided to the volume chamber; and a drain passage configured to drain, from the volume chamber, the liquid passed through the restriction portion.BRIEF DESCRIPTION OF DRAWINGS

[0006] [FIG. 1] FIG. 1 is a plan view of a pump portion of an internal gear pump according to an embodiment of the present invention. [FIG. 2] FIG. 2 is a plan view of the pump portion with a cover portion removed. [FIG. 3] FIG. 3 is a plan view showing a back surface of the cover portion. [FIG. 4] FIG. 4 is an enlarged view of a volume chamber. [FIG. 5] FIG. 5 is a plan view showing the back surface of the cover portion in a first modification. [FIG. 6] FIG. 6 is a plan view of the pump portion and a body portion in the first modification. [FIG. 7] FIG. 7 is a sectional view of the pump portion and the body portion in a second modification. [FIG. 8] FIG. 8 is an enlarged view of one modification of the volume chamber. [FIG. 9] FIG. 9 is an enlarged view of another modification of the volume chamber. [FIG. 10] FIG. 10 is a view showing one modification of a drain passage. DESCRIPTION OF EMBODIMENTS

[0007] Hereinafter, an internal gear pump according to an embodiment of the present invention will be described with reference to the drawings. The internal gear pump according to the embodiment of the present invention is mounted on, for example, a vehicle, and discharges coolant (liquid) for cooling an electric motor mounted on the vehicle or discharges oil (liquid) for lubricating gears mounted on the vehicle. The internal gear pump may be used as a fluid pressure source that discharges working fluid (liquid) for driving equipment. In addition, the internal gear pump may be mounted on industrial machinery other than vehicles. In this embodiment, a case in which oil serving as a viscous fluid is used as the liquid discharged by the internal gear pump will be described, but instead of oil, for example, an aqueous alternative fluid or the like may also be used.

[0008] An internal gear pump 100A according to this embodiment will be described with reference to FIGs. 1 to 4. FIGs. 1 and 2 are plan views of a pump portion 10 of the internal gear pump 100A, and FIG. 2 shows a plan view with a cover portion 40A removed (a plan view of the pump portion 10 and a body portion 30A of a housing 20A). FIG. 3 is a plan view showing a back surface of the cover portion 40A that covers the pump portion 10.

[0009] The internal gear pump 100A includes the pump portion 10 that discharges the oil when a drive shaft 1 is rotated, and the housing 20A that accommodates the pump portion 10. The arrow in FIG. 2 indicates the rotational direction of the drive shaft 1.

[0010] As shown in FIG. 2, the pump portion 10 has an inner rotor 11 to which the drive shaft 1 is coupled, and an outer rotor 12 that is arranged outside the inner rotor 11. The inner rotor 11 and the outer rotor 12 are accommodated in the housing 20A (specifically, in the body portion 30A described later), are provided eccentrically relative to each other, and are covered by the cover portion 40A of the housing 20A. Specifically, the inner rotor 11 is provided such that its center coincides with the center of the drive shaft 1, and the outer rotor 12 is provided such that its center is shifted downward from the drive shaft 1 in FIGs. 1 and 2. The inner rotor 11 has a plurality of external teeth 11a on an outer peripheral surface, and the outer rotor 12 has a plurality of internal teeth 12a, which are in sliding contact with the external teeth 11a, on an inner peripheral surface. The external teeth 11a and the internal teeth 12a are formed with different numbers of teeth, and each of pump chambers 13 is partitioned by adjacent external teeth 11a of the inner rotor 11 and the internal teeth 12a of the outer rotor 12. A plurality of pump chambers 13 are formed in the pump portion 10. Note that trochoidal curve tooth profiles are applied to the external teeth 11a of the inner rotor 11 and the internal teeth 12a of the outer rotor 12, but the invention is not limited thereto, and curve tooth profiles such as involute curves, cycloid curves, or the like may also be used.

[0011] As shown in FIGs. 1 and 3, the cover portion 40A is formed with a suction port 42 and a suction inlet 43 that guide the oil from outside to the pump chambers 13, and a discharge port 44 and a discharge outlet 45 that guide pressurized oil (liquid, pressurized liquid) discharged from the pump chambers 13 to outside. When the drive shaft 1 is rotated by a motor 15, the inner rotor 11 and the outer rotor 12 are rotated while the external teeth 11a of the inner rotor 11 slide against the internal teeth 12a of the outer rotor 12. As the inner rotor 11 and the outer rotor 12 are rotated, the volume of each pump chamber 13 is repeatedly expanded and contracted. In an expansion region where the pump chambers 13 are expanded (a suction region 65 described later), the oil is sucked through the suction port 42 and the suction inlet 43, and in a contraction region where the pump chambers 13 are contracted (a discharge region 66 described later), the oil is discharged and guided to outside through the discharge port 44 and the discharge outlet 45.

[0012] As shown in FIGs. 1 and 2, the housing 20A has the body portion 30A that accommodates the pump portion 10, and the cover portion 40A that is attached to the body portion 30A and covers the pump portion 10. The body portion 30A and the cover portion 40A are provided side by side in the axial direction of the drive shaft 1 (hereinafter also simply referred to as "the axial direction").

[0013] As shown in FIG. 2, the body portion 30A has a pump accommodating recessed portion 31 in which the pump portion 10 is accommodated. The pump accommodating recessed portion 31 is a recessed portion with a circular bottom surface, and the inner rotor 11 and the outer rotor 12 of the pump portion 10 are accommodated in the pump accommodating recessed portion 31 eccentrically to each other. Specifically, the center of the pump accommodating recessed portion 31 coincides with the center of the outer rotor 12 and is formed offset from the center of the drive shaft 1. A plurality of fastening holes 32 into which fastening members 70 (see FIG. 1) for attaching the cover portion 40A are respectively fastened are formed in an end surface 30a of the body portion 30A. The fastening members 70 are bolts. The fastening holes 32 are formed so as to correspond to insertion holes 47 (see FIG. 3) provided in the cover portion 40A.

[0014] As shown in FIGs. 1 and 2, the cover portion 40A is provided so as to cover the pump accommodating recessed portion 31 in which the inner rotor 11 and the outer rotor 12 are accommodated. The cover portion 40A is attached to the end surface 30a of the body portion 30A by the fastening members 70. The cover portion 40A has a disc-shaped cover body portion 41 attached to the end surface 30a, and a cylindrical projected portion 48 formed so as to project from the cover body portion 41 in the axial direction.

[0015] The cover body portion 41 is formed such that a region facing the inner rotor 11 and the outer rotor 12 protrudes in the axial direction. As shown in FIGs. 1 and 3, the cover body portion 41 is formed with: the suction port 42, the discharge port 44, and the suction inlet 43 described above; a shaft accommodating portion 46 in which a tip end portion of the drive shaft 1 is accommodated; and a plurality of insertion holes 47 through which the fastening members 70 are respectively inserted to fix the cover portion 40A to the body portion 30A. In addition, the projected portion 48 is formed with the above-described discharge outlet 45.

[0016] As shown in FIG. 3, the suction port 42 and the discharge port 44 are formed in a back surface of the cover body portion 41 so as to have an arc shape. The suction port 42 and the discharge port 44 are formed such that inner circumferences 42a and 44a are formed on a circle A1 centered on the drive shaft 1, and outer circumferences 42b and 44b are formed on a circle B1 centered on the outer rotor 12. A discharge-suction transition section 60 is formed between a front end portion 44c of the discharge port 44 and a rear end portion 42d of the suction port 42 in the rotational direction of the drive shaft 1, and a suction-discharge transition section 61 is formed between a front end portion 42c of the suction port 42 and a rear end portion 44d of the discharge port 44 in the rotational direction of the drive shaft 1. The cover body portion 41 is divided into a plurality of imaginary regions by a first imaginary line 62 passing through a midpoint of the discharge-suction transition section 60 and the center of the drive shaft 1, and a second imaginary line 63 perpendicular to the first imaginary line 62 and the drive shaft 1 and passing through the center of the drive shaft 1.

[0017] For example, the suction region 65 is a region (a planar region orthogonal to the axial direction) where the suction port 42 is formed and is a region on one side (the suction port 42 side) from the first imaginary line 62. In addition, the discharge region 66 is a region where the discharge port 44 is formed and is a region on the other side (the discharge port 44 side) from the first imaginary line 62. The suction port 42 and the discharge port 44 are formed symmetrically with respect to the first imaginary line 62.

[0018] The suction inlet 43 is formed to have an arc shape in a surface of the cover body portion 41 and communicates with the suction port 42. The suction inlet 43 is formed so that its entirety faces the suction port 42. The shaft accommodating portion 46 is formed to have a concave shape at the center of the back surface of the cover body portion 41. The tip end portion of the drive shaft 1 is accommodated inside the shaft accommodating portion 46, and the shaft accommodating portion 46 rotatably supports the drive shaft 1. The discharge outlet 45 is formed so as to penetrate through the projected portion 48 in the axial direction (see FIG. 1) and communicates with the discharge port 44. In the internal gear pump 100A, the projected portion 48 (see FIG. 1) is inserted into a hole portion (not shown) provided in equipment to which the internal gear pump 100A is attached, and the discharge outlet 45 is connected to a flow path (not shown). A suction passage 80 shown by a two-dot chain line is connected to the suction inlet 43, and the oil is sucked through the suction passage 80.

[0019] In the discharge region 66, the pump chamber 13 partitioned by the inner rotor 11 and the outer rotor 12 pressurizes the oil while being contracted. Therefore, in the discharge region 66, an unbalanced load F (see FIG. 2) acts on the inner rotor 11 and the outer rotor 12 in directions in which the inner rotor 11 and the outer rotor 12 move away from each other. As a result, in the suction region 65, a gear clearance between external teeth gears of the inner rotor 11 and internal teeth gears of the outer rotor 12 may become smaller, causing a deterioration in sliding characteristics or an increase in torque.

[0020] Therefore, the internal gear pump 100A is configured as described further below.

[0021] As shown in FIGs. 2 and 3, the internal gear pump 100A further has a first volume chamber R1 provided in the discharge region 66, an introduction passage 49 that guides the oil to the first volume chamber R1, and a drain passage 50 that drains the oil from the first volume chamber R1. Both the introduction passage 49 and the drain passage 50 are formed in a groove shape in the back surface of the cover portion 40A and are configured as passages in a state in which the cover portion 40A is arranged on the end surface 30a of the body portion 30A. In FIG. 2, the suction port 42, the discharge port 44, the introduction passage 49, and the drain passage 50, which are formed in the cover portion 40A, as well as the suction passage 80 are also shown by two-dot chain lines. In addition, in FIG. 3, the first volume chamber R1 and an outer circumference of the outer rotor 12 are also shown by two-dot chain lines. FIG. 4 shows the first volume chamber R1 in an enlarged state.

[0022] The introduction passage 49 communicates the discharge port 44 and the first volume chamber R1, and the pressurized oil discharged from the pump portion 10 is guided to the first volume chamber R1 through the introduction passage 49. The drain passage 50 communicates the first volume chamber R1 and the suction port 42, and the pressurized oil is drained from the first volume chamber R1 to the suction port 42 through the drain passage 50. The introduction passage 49 communicates with the first volume chamber R1 on one end side in the circumferential direction, and the drain passage 50 communicates with the first volume chamber R1 on the other end side in the circumferential direction. Therefore, in the first volume chamber R1, the pressurized oil guided from the discharge port 44 flows in a direction from the one end side to the other end side in the circumferential direction, in other words, the pressurized oil flows along the rotational direction of the drive shaft 1. The introduction passage 49 communicates with the discharge port 44 on the one end side in the circumferential direction, and the drain passage 50 communicates with the suction port 42 on the one end side in the circumferential direction.

[0023] As shown in FIGs. 2 and 4, the first volume chamber R1 is partitioned by the outer circumference of the outer rotor 12 and an inner circumference of the pump accommodating recessed portion 31 of the body portion 30A (a recessed portion 33 which will be described later), and is partitioned by a bottom surface of the pump accommodating recessed portion 31 and the cover portion 40A. The recessed portion 33 is formed in the inner circumference of the pump accommodating recessed portion 31 at a portion where the first volume chamber R1 is formed. The recessed portion 33 is formed to have a concave shape along the radial direction from the inner peripheral surface of the pump accommodating recessed portion 31, and a bottom surface 33a thereof is provided so as to extend along the direction orthogonal to the radial direction. The recessed portion 33 is provided so as to extend from the end surface 30a of the body portion 30A to the bottom surface of the pump accommodating recessed portion 31 in accordance with the thickness of the outer rotor 12 in the axial direction. The first volume chamber R1 extends along the circumferential direction, and a circumferential length thereof is set in consideration of a biasing force to be applied to the outer rotor 12 based on the pressurized oil in the first volume chamber R1. The first volume chamber R1 is formed along the outer circumference of the outer rotor 12 and faces the outer circumference of the outer rotor 12. A restriction portion T is formed in the first volume chamber R1 by the outer circumference of the outer rotor 12 and the bottom surface 33a of the recessed portion 33.

[0024] The restriction portion T is a portion with a minimum cross-sectional area (a minimum cross-sectional area portion) and its vicinity in the first volume chamber R1, and is formed along the outer circumference of the outer rotor 12 in a circumferentially central portion of the first volume chamber R1. The cross-sectional area is a cross-sectional area of a portion of the first volume chamber R1 along the radial direction that is sandwiched between the outer circumference of the outer rotor 12 and the bottom surface 33a of the recessed portion 33. The minimum cross-sectional area portion has a smaller cross-sectional area compared to an introduction side of the oil of the first volume chamber R1 and further has a smaller cross-sectional area compared to the oil drain side of the first volume chamber R1. The restriction portion T is formed so as to face the outer circumference of the outer rotor 12, and the biasing force based on the pressurized oil in the first volume chamber R1 including inside the restriction portion T acts on the outer rotor 12.

[0025] In the internal gear pump 100A configured as described above, the pressurized oil introduced into the first volume chamber R1 through the introduction passage 49 is drawn into the restriction portion T by the rotation of the outer rotor 12, thereby generating the wedge effect, and thus, the oil pressure is increased so as to be higher than the discharge pressure. Therefore, by biasing the outer rotor 12 against the unbalanced load F with the biasing force based on high oil pressure compared to the discharge pressure, an influence of the unbalanced load F generated in the discharge region 66 can be suitably reduced. In addition, the oil that has passed through the restriction portion T can be drained from the first volume chamber R1 through the drain passage 50.

[0026] The first volume chamber R1 is partitioned by the outer circumference composed of the circumferential surface of the outer rotor 12 and the bottom surface 33a composed of a flat surface of the recessed portion 33, and the outer circumference of the outer rotor 12 approaches the bottom surface 33a of the recessed portion 33 toward the restriction portion T from the introduction side of the oil of the first volume chamber R1. Therefore, the first volume chamber R1 has a shape in which the cross-sectional area is gradually decreased from the introduction side of the oil toward the restriction portion T. With such a configuration, the wedge effect can be effectively generated, and so, the influence of the unbalanced load F can be more suitably reduced. The first volume chamber R1 has a shape in which the cross-sectional area gradually increases from the restriction portion T toward the oil drain side.

[0027] The pressurized oil in the first volume chamber R1 that has passed through the restriction portion T is guided to the pump chambers 13 positioned in the suction region 65 through the drain passage 50 and the suction port 42. As a result, the oil pressure drop that may occur in the pump chambers 13 positioned in the suction region 65 is suppressed, and thus, generation of cavitation is also suppressed.

[0028] A recessed portion having a similar shape facing the suction port 42 may be provided in the bottom surface of the pump accommodating recessed portion 31, and the drain passage 50 may be formed in the body portion 30 to communicate the first volume chamber R1 and the recessed portion facing the suction port 42. Even with such a configuration, the pressurized oil in the first volume chamber R1 can be guided to the pump chambers 13 positioned in the suction region 65.(First Modification)

[0029] Next, an internal gear pump 100B according to a first modification will be described with reference to FIGs. 5 and 6. FIG. 5 is a plan view showing the back surface of a cover portion 40B of a housing 20B of the internal gear pump 100B. FIG. 6 is a plan view of the pump portion 10 and the body portion 30A of the housing 20B of the internal gear pump 100B. In FIG. 6, the suction port 42, the discharge port 44, the introduction passage 49, and a drain passage 51 formed in the cover portion 40B as well as the suction passage 80 are also shown by two-dot chain lines.

[0030] The first modification differs from the above-described embodiment in the configuration of the drain passage that drains the liquid from the volume chamber. In the first modification, the drain passage 51 is formed in the cover portion 40B, and as described below, the drain passage 51 communicates the first volume chamber R1 and the suction port 42 by connecting to the suction port 42 in an orientation along a direction S along a suction flow of the oil to the suction port 42. The drain passage 51 communicates with the suction port 42 at the center in the circumferential direction, and additionally, communicates with the suction port 42 at a position overlapping with the suction passage 80 in the axial direction.

[0031] The oil is sucked into the suction port 42 through the suction passage 80, and the suction flow of the oil to the suction port 42 is formed along an extending direction of the suction passage 80. Therefore, the direction S along the suction flow of the oil to the suction port 42 is, for example, a direction S1 along the extending direction of the suction passage 80 as viewed from the axial direction, and the drain passage 51 connects to the suction port 42 in the direction S1. With such a configuration, the flow of the oil drained from the drain passage 51 to the suction port 42 is suppressed from interfering with the suction flow to the suction port 42, and so, a pressure loss is suppressed.

[0032] The direction S along the suction flow may be a direction S2 or a direction S3 that intersects with the direction S1 at an acute angle α in the direction from the drain passage 51 side toward the suction port 42 side. The acute angle α can be set to, for example, less than 45 degrees. If the acute angle is less than 45 degrees, a vector component in the direction S1 along the extending direction of the suction passage 80 becomes larger than a vector component in the direction orthogonal to the direction S1, and so, the suction flow to the suction port 42 is less likely to be obstructed. From a viewpoint of suppressing obstruction of the suction flow to the suction port 42, a smaller acute angle α is preferable.

[0033] The oil sucked into the suction port 42 is subject to the force in the rotational direction of the drive shaft 1. Between the direction S2 and the direction S3, the direction S2 that forms the acute angle α in the direction approaching the suction port 42 with respect to the direction S1 becomes more along the rotational direction compared to the direction S3 that forms the acute angle α in the direction away from the suction port 42 with respect to the direction S1. Therefore, between the direction S2 and the direction S3, the direction S2 is less likely to obstruct the flow of the oil sucked into the suction port 42 and can be said to be preferable.(Second Modification)

[0034] Next, an internal gear pump 100C according to a second modification will be described with reference to FIG. 7. FIG. 7 is a plan view showing the pump portion 10 and a body portion 30B of a housing 20C of the internal gear pump 100C. In FIG. 7, the suction port 42, the discharge port 44, and an introduction passage 52 formed in a cover portion (not shown) of the housing 20C are also shown by two-dot chain lines.

[0035] The second modification differs from the above-described embodiment in a configuration of the volume chamber. In the second modification, the body portion 30B has a second volume chamber R2 that faces the outer circumference of the outer rotor 12. The second volume chamber R2 is partitioned by a recessed portion 34 formed in a recessed shape in the radial direction from the pump accommodating recessed portion 31, the outer circumference of the outer rotor 12, and the cover portion of the internal gear pump 100C, and has a rectangular cross-section orthogonal to the radial direction. The cross-section is set to a size that allows a ball 90 described later to slide, and a gap is formed between the second volume chamber R2 and the ball 90 by this cross-section. The pressurized oil is introduced, from the discharge port 44, into the second volume chamber R2 through the introduction passage 52 that communicates the discharge port 44 and the second volume chamber R2. The pressurized oil is introduced near a bottom surface (a wall surface 34a orthogonal to the radial direction of the recessed portion 34) of the second volume chamber R2.

[0036] In the second volume chamber R2, the pressurized oil introduced from the discharge port 44 acts directly on the outer rotor 12. Therefore, the drain passage 50 described in the above-described embodiment or the drain passage 51 described in the first modification is not required in the second volume chamber R2. An opening area of a portion of the second volume chamber R2 facing the outer rotor 12 is set in consideration of the biasing force to be applied to the outer rotor 12 based on the pressurized oil in the second volume chamber R2, and it may be set wider in the circumferential direction or in the radial direction compared to the above-described cross-section, for example.

[0037] The ball 90 and a spring 91 are accommodated in the second volume chamber R2. The ball 90 is provided facing the outer rotor 12, and the spring 91 is provided between the ball 90 and the wall surface 34a forming the bottom surface of the second volume chamber R2. The spring 91 is a biasing member and is accommodated in the second accommodation chamber R2 in a compressed state, thereby biasing the ball 90 toward the outer rotor 12.

[0038] In the internal gear pump 100C configured as described above, in addition to the biasing force based on the discharge pressure due to the pressurized oil guided into the second volume chamber R2, the biasing force opposing the unbalanced load F is generated by the biasing force exerted by the spring 91. Therefore, also in this case, because the outer rotor 12 can be biased against the unbalanced load F with the biasing force larger than the biasing force based on discharge pressure, the influence of the unbalanced load F can be suitably reduced. If the outer rotor 12 were to be biased only by the spring 91, either a sufficient biasing force could not be generated, or the size of the spring 91 would have to be increased, which would result in an increase in the size of the internal gear pump 100C or would make the installation of the spring 91 difficult.(Other Modifications)

[0039] Next, other modifications will be described with reference to FIGs. 8 to 10.

[0040] As shown in FIG. 8, the bottom surface 33a of the recessed portion 33 of the first volume chamber R1 may be, for example, an arc surface. In this example, the bottom surface 33a is formed by a gentle arc surface having a smaller curvature compared to a cylindrical surface of the outer circumference of the outer rotor 12. In this case as well, because the restriction portion T can be formed at the center of the first volume chamber R1 in the circumferential direction by the outer circumference of the outer rotor 12 and the arc-shaped bottom surface 33a, the wedge effect can be generated. In addition, because the first volume chamber R1 can be formed to have a shape in which the cross-sectional area is gradually decreased from the introduction side of the oil toward the restriction portion T, the wedge effect can be effectively generated.

[0041] As shown in FIG. 9, the restriction portion T of the first volume chamber R1 may be, for example, a portion in which the cross-sectional area is set smaller in a step-like manner compared to the introduction side of the oil of the first volume chamber R1. Even with such a restriction portion T, the wedge effect can be generated when oil is drawn in by the rotating outer rotor 12. In addition, the wedge effect may also be generated by providing multistage steps along the circumferential direction from the introduction side of the oil to gradually reduce the cross-sectional area.

[0042] As shown in FIG. 10, the first volume chamber R1 may communicate with the discharge port 44 through a drain passage 52 that communicates the first volume chamber R1 and the discharge port 44. Even with such a configuration, the pressure of the pressurized oil in the first volume chamber R1 is increased so as to become higher than the discharge pressure by the wedge effect when it is drawn into the restriction portion T, and so, it is possible to discharge the oil from the first volume chamber R1.

[0043] The configurations, operations, and effects of the embodiment of the present invention will be collectively described below.

[0044] The internal gear pump 100A includes the pump portion 10 configured to discharge the oil when the drive shaft 1 is rotated, and the housing 20A that accommodates the pump portion 10. The pump portion 10 has: the inner rotor 11 having the plurality of external teeth 11a and connected to the drive shaft 1; and the outer rotor 12 having the plurality of internal teeth 12a in sliding contact with the external teeth 11a, the outer rotor 12 being arranged outside the inner rotor 11. The internal gear pump 100A has: the first volume chamber R1 facing the outer circumference of the outer rotor 12 in the discharge region 66, the first volume chamber R1 having the restriction portion T formed to extend along the outer circumference, the first volume chamber R1 being configured such that the pressurized oil discharged from the pump portion 10 is guided to the first volume chamber R1; and the drain passage 50 configured to drain, from the first volume chamber R1, the oil passed through the restriction portion T.

[0045] According to this configuration, the wedge effect can be generated by drawing the pressurized oil into the restriction portion T by the rotating outer rotor 12, and the oil pressure of the pressurized oil guided to the first volume chamber R1 can be increased so as to be higher than the discharge pressure. Therefore, by biasing the outer rotor 12 against the unbalanced load F with the biasing force based on high oil pressure compared to the discharge pressure, the influence of the unbalanced load F generated in the discharge region 66 can be suitably reduced. In addition, the oil that has passed through the restriction portion T can be drained from the first volume chamber R1 via the drain passage 50.

[0046] The first volume chamber R1 has the shape in which the cross-sectional area is gradually decreased from the introduction side of the oil toward the restriction portion T.

[0047] According to this configuration, because the wedge effect can be effectively generated, the influence of the unbalanced load F can be more suitably reduced.

[0048] The drain passage 50 / the drain passage 51 communicates the first volume chamber R1 and the pump chambers 13 of the pump portion 10 positioned in the suction region 65.

[0049] According to this configuration, by guiding the pressurized oil in the first volume chamber R1 to the pump chambers 13 positioned in the suction region 65 through the drain passage 51, the oil pressure drop that may occur in the pump chambers 13 positioned in the suction region 65 can be suppressed, and so, it is possible to suppress the generation of cavitation.

[0050] The drain passage 51 is connected to the suction port 42 in the direction S along the suction flow of the oil to the suction port 42, the suction flow guiding the oil to the pump chambers 13.

[0051] According to this configuration, because the oil from the drain passage 51 is guided to the suction port 42 so as not to interfere with the suction flow of the suction port 42, it is possible to suppress the generation of pressure loss.

[0052] The internal gear pump 100C includes the pump portion 10 configured to discharge the oil when the drive shaft 1 is rotated, and the housing 20C that accommodates the pump portion 10. The pump portion 10 has: the inner rotor 11 having the plurality of external teeth 11a and connected to the drive shaft 1; and the outer rotor 12 having the plurality of internal teeth 12a in sliding contact with the external teeth 11a, the outer rotor 12 being arranged outside the inner rotor 11. The internal gear pump 100C has: the second volume chamber R2 facing the outer circumference of the outer rotor 12 in the discharge region 66, the second volume chamber R2 being configured such that the pressurized oil discharged from the pump portion 10 is guided to the second volume chamber R2; and the spring 91 accommodated in the second volume chamber R2, the spring 91 being configured to bias the outer rotor 12.

[0053] According to this configuration, the outer rotor 12 can be biased against the unbalanced load F by the biasing force exerted by the spring 91, in addition to the biasing force based on the discharge pressure due to the pressurized oil guided into the second volume chamber R2. Therefore, compared to a case in which the outer rotor 12 is biased only by the biasing force based on the discharge pressure, it is possible to suitably reduce the influence of the unbalanced load F.

[0054] Embodiments of this invention were described above, but the above embodiments are merely examples of applications of this invention, and the technical scope of this invention is not limited to the specific constitutions of the above embodiments.

[0055] This application claims priority based on Japanese Patent Application No.2023-098722 filed with the Japan Patent Office on June 15, 2023, the entire contents of which are incorporated into this specification.

Examples

first modification

(First Modification)

[0029]Next, an internal gear pump 100B according to a first modification will be described with reference to FIGs. 5 and 6. FIG. 5 is a plan view showing the back surface of a cover portion 40B of a housing 20B of the internal gear pump 100B. FIG. 6 is a plan view of the pump portion 10 and the body portion 30A of the housing 20B of the internal gear pump 100B. In FIG. 6, the suction port 42, the discharge port 44, the introduction passage 49, and a drain passage 51 formed in the cover portion 40B as well as the suction passage 80 are also shown by two-dot chain lines.

[0030]The first modification differs from the above-described embodiment in the configuration of the drain passage that drains the liquid from the volume chamber. In the first modification, the drain passage 51 is formed in the cover portion 40B, and as described below, the drain passage 51 communicates the first volume chamber R1 and the suction port 42 by connecting to the suction port 42 in an or...

second modification

(Second Modification)

[0034]Next, an internal gear pump 100C according to a second modification will be described with reference to FIG. 7. FIG. 7 is a plan view showing the pump portion 10 and a body portion 30B of a housing 20C of the internal gear pump 100C. In FIG. 7, the suction port 42, the discharge port 44, and an introduction passage 52 formed in a cover portion (not shown) of the housing 20C are also shown by two-dot chain lines.

[0035]The second modification differs from the above-described embodiment in a configuration of the volume chamber. In the second modification, the body portion 30B has a second volume chamber R2 that faces the outer circumference of the outer rotor 12. The second volume chamber R2 is partitioned by a recessed portion 34 formed in a recessed shape in the radial direction from the pump accommodating recessed portion 31, the outer circumference of the outer rotor 12, and the cover portion of the internal gear pump 100C, and has a rectangular cross-sec...

Claims

1. An internal gear pump comprising: a pump portion configured to discharge liquid when a drive shaft is rotated; and a housing accommodating the pump portion, the pump portion having: an inner rotor having a plurality of external teeth and connected to the drive shaft; and an outer rotor having a plurality of internal teeth in sliding contact with the external teeth, the outer rotor being arranged outside the inner rotor, wherein the internal gear pump has: a volume chamber facing an outer circumference of the outer rotor in a discharge region, the volume chamber having a restriction portion formed to extend along the outer circumference, the volume chamber being configured such that the liquid discharged from the pump portion is guided to the volume chamber; and a drain passage configured to drain, from the volume chamber, the liquid passed through the restriction portion.

2. The internal gear pump according to claim 1, wherein the volume chamber has a shape in which a cross-sectional area is gradually decreased from an introduction side of the liquid toward the restriction portion.

3. The internal gear pump according to claim 1, wherein the drain passage is configured to communicate the volume chamber and pump chambers of the pump portion positioned in a suction region.

4. The internal gear pump according to claim 3, wherein the drain passage is connected to a suction port guiding the liquid to the pump chamber in a direction along a suction flow of the liquid to the suction port.

5. An internal gear pump comprising: a pump portion configured to discharge liquid when a drive shaft is rotated; and a housing accommodating the pump portion, the pump portion having: an inner rotor having a plurality of external teeth and connected to the drive shaft; and an outer rotor having a plurality of internal teeth in sliding contact with the external teeth, the outer rotor being arranged outside the inner rotor, wherein the internal gear pump has: a volume chamber facing an outer circumference of the outer rotor in a discharge region, the volume chamber being configured such that the liquid discharged from the pump portion is guided to the volume chamber; and a biasing member accommodated in the volume chamber, the biasing member being configured to bias the outer rotor.

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