Internal gear pump

Abstract

An internal gear pump includes an inner rotor having a plurality of external teeth, an outer rotor having a plurality of internal teeth meshing with the plurality of external teeth, a housing rotatably accommodating the inner rotor and the outer rotor, and an axial gap motor having a stator and a motor rotor. The outer rotor is the motor rotor. The housing includes a peripheral wall portion provided in a cylindrical shape to surround an outer periphery of the outer rotor, and a first cover portion and a second cover portion, each covering a corresponding one of two end portions of the peripheral wall portion. The first cover portion is disposed between the stator and the outer rotor. The second cover portion has a suction port and a discharge port communicating with an inside of the housing.

Description

TECHNICAL AREA

[0001] The present invention relates to an internal gear pump. This application claims priority from Japanese patent application No. 2022-202209, which was filed on December 19, 2022, and whose entire contents are incorporated herein by reference. STATE OF THE ART

[0002] Patent literature 1 describes an electric pump with an axial gap rotor. The axial gap rotor is a rotor integrated into an impeller, comprising an impeller and a magnet supported by the impeller. The impeller and the magnet are arranged side by side along a rotating shaft of the impeller. That is, the impeller, to which the rotational force of the rotor is transmitted, and the rotor are arranged parallel to each other along the rotating shaft of the rotor. LIST OF CITINGS PATENT LITERATURE

[0003] [Patent literature 1] Unexamined Japanese patent application with publication number 2020 - 182269 SUMMARY OF THE INVENTION

[0004] An internal gear pump according to the present invention comprises an inner rotor with a plurality of external teeth, an outer rotor with a plurality of internal teeth meshing with the plurality of external teeth, a housing rotatably accommodating the inner and outer rotors, and an axial gap motor with a stator and a motor rotor. The outer rotor is the motor rotor. The housing comprises a circumferential wall section provided in a cylindrical shape to surround an outer circumference of the outer rotor, and a first covering section and a second covering section, each covering one of two corresponding end sections of the circumferential wall section. The first covering section is arranged between the stator and the outer rotor. The second covering section has an inlet and an outlet opening that communicate with the interior of the housing. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic cross-sectional view of an internal gear pump according to one embodiment. Fig. Figure 2 is an illustrative view of a stator provided in an internal gear pump according to one embodiment. Fig. Figure 3 is an illustrative view of an inner rotor and an outer rotor provided in an internal gear pump according to one embodiment. DETAILED DESCRIPTION [Problems to be solved by the present invention]

[0005] When the impeller and rotor are arranged side-by-side along the rotor's rotating shaft, the overall rotor tends to be larger, even in rotors with an integrated impeller. There is a need for electric pumps that can be miniaturized.

[0006] One of the objectives of the present invention is to provide an internal gear pump that can be miniaturized. [Advantageous effects of the present invention]

[0007] The internal gear pump of the present invention can be miniaturized. [Description of embodiments of the present invention]

[0008] First, embodiments of the present invention are listed and described. (1) An internal gear pump according to one embodiment of the present invention comprises an inner rotor with a plurality of external teeth, an outer rotor with a plurality of internal teeth meshing with the plurality of external teeth, a housing rotatably accommodating the inner rotor and the outer rotor, and an axial gap motor with a stator and a motor rotor. The outer rotor is the motor rotor. The housing comprises a circumferential wall section provided in a cylindrical shape to surround an outer circumference of the outer rotor, and a first covering section and a second covering section, each covering one of two corresponding end sections of the circumferential wall section. The first covering section is arranged between the stator and the outer rotor. The second covering section has an inlet opening and an outlet opening that communicate with the interior of the housing.

[0009] In an internal gear pump, the outer rotor acts as the motor rotor, allowing for miniaturization. In this design, the outer rotor is the driving force, while the inner rotor is passive, providing only passive power to the outer rotor. Internal gear pumps can be configured in two ways: firstly and secondly. In the first configuration, one or more components, to which the rotational force of the motor rotor is transferred, are located within the annular motor rotor. In an internal gear pump of this configuration, the size of the motor rotor can be significantly reduced along the shaft compared to pumps where the motor rotor and outer rotor are separate components.The second configuration consists of the motor rotor and stator positioned opposite each other, with the first cover section located between them. In the internal gear pump that uses this second configuration, the size of the motor rotor can be slightly reduced along its diameter compared to the case where the motor rotor and outer rotor are formed from independent elements and the inner and outer rotors are arranged inside the annular stator.

[0010] In an internal gear pump, the outer rotor is surrounded by the circumferential wall section, and the first sealing section is positioned between the motor rotor and the stator, thus improving the sealing performance of the casing. Therefore, the internal gear pump functions appropriately as an electric pump.

[0011] In an internal gear pump, the operating noise of the inner and outer rotors is barely transmitted to the outside of the housing due to the initial configuration. Therefore, the internal gear pump is particularly quiet. This operating noise includes, for example, the impact noise of the teeth between the outer tooth of the inner rotor and the inner tooth of the outer rotor, or a vibration noise.

[0012] In the internal gear pump, the first configuration facilitates the transfer of heat generated in the motor rotor, i.e., heat generated in the outer rotor, to the fluid, thus facilitating a rise in the fluid temperature. As the fluid temperature increases, its viscosity decreases. This reduces the load on the axial-gap motor and lowers its power consumption. The heat generated in the motor rotor is transferred to the fluid, thereby suppressing heat generation in the motor rotor.

[0013] (2) In the internal gear pump according to (1) the first covering section may be made of a non-magnetic material.

[0014] If the first covering section is made of a non-magnetic material, its influence on the magnetic flux from the stator to the motor rotor (i.e., from the stator to the outer rotor) is less than if the first covering section is made of a magnetic material. With a non-magnetic covering section, the outer rotor can rotate appropriately with the rotating magnetic field of the stator.

[0015] (3) In the internal gear pump according to (1) or (2) the thickness of the first covering section can be from 0.3 mm to 5 mm.

[0016] If the thickness of the first covering section is 0.3 mm or more, its strength can be increased, and it will hardly deform, even when the outer rotor slides on it. Minimal deformation of the first covering section also slightly improves the sealing performance of the housing. Furthermore, if the thickness of the first covering section is 0.3 mm or more, operating noise generated by the inner and outer rotors will be minimally transmitted to the outside of the housing. Finally, if the thickness of the first covering section is 5 mm or less, the motor rotor can easily rotate with the stator's rotating magnetic field.

[0017] (4) In the case of the internal gear pump according to one of (1) to (3) the distance between the first covering section and the outer rotor may be 0.01 mm to 0.20 mm.

[0018] If the clearance is 0.01 mm or more, the first cover section and the outer rotor barely slide against each other, and the occurrence of wear or seizing between the first cover section and the outer rotor can be suppressed. If the clearance is 0.20 mm or less, the fluid barely leaks through the clearance to the outer circumference of the outer rotor, and the function of the internal gear pump is favorable. [Details of embodiments of the present invention]

[0019] An example of the internal gear pump of the present invention is described with reference to the drawings. In the drawings, identical reference numerals denote identical or corresponding parts. In the drawings, some components may be exaggerated or simplified for the sake of clarity of description. The proportions of the individual parts in the drawings may differ from the actual proportions. The present invention is not limited to these examples but is defined by the scope of the claims and is intended to encompass all modifications within the meaning and scope that correspond to the scope of the claims. <Overview>

[0020] According to the representation in Fig. 1 comprises an internal gear pump 1 of the embodiment comprising an inner rotor 2, an outer rotor 3, a housing 4, and an axial gap motor 5. One of the features of the internal gear pump 1 of the embodiment is that the outer rotor 3 is a motor rotor 7 of the axial gap motor 5. Another feature of the internal gear pump 1 of the embodiment is that a first covering section 41 of the housing 4 is arranged between the motor rotor 7 and a stator 6 of the axial gap motor 5. <axialspaltmotor>

[0021] The axial gap motor 5 comprises a stator 6 and a motor rotor 7. The stator 6 and the motor rotor 7 are arranged coaxially with the rotating shaft of the motor rotor 7. The stator 6 and the motor rotor 7 are positioned opposite each other with a gap between them in one direction along the rotating shaft. The axial gap motor 5 is a single-stator / single-rotor type comprising a stator 6 and a motor rotor 7. <stator>

[0022] According to the representation in Fig. 1 and Fig. 2 the stator 6 comprises a stator core 60 and a plurality of coils 65.

[0023] The stator core 60 comprises a yoke 61 and a plurality of teeth 62. The yoke 61 is, for example, a circular plate. The yoke 61 can be an annular plate. Each tooth 62 is a columnar body. Each tooth 62 projects from either the front or the rear face of the yoke 61. Each tooth 62 is spaced at intervals along the entire circumference of the yoke 61. Each tooth 62 is, for example, spaced at equal intervals. Each tooth 62 has the same shape and size. Each tooth 62 has, for example, a prismatic or cylindrical shape. The yoke 61 and the teeth 62 are formed in one piece, for example, from a powdered material. The yoke 61 and the teeth 62 can be independent elements and can be connected to each other. The yoke 61 magnetically couples adjacent teeth 62 from the plurality of teeth 62.

[0024] A distal end face of each tooth 62 faces the motor rotor 7 described later. Each tooth 62 is provided with a coil 65. In the Fig. 1 and Fig. 2 is one end of a winding that forms coil 65, not shown.

[0025] The stator core 60 of the present embodiment comprises an annular circumferential wall section 63, which is arranged on a circumferential edge section of the yoke 61. The circumferential wall section 63 is provided on a surface of the yoke 61 from which each tooth 62 projects. The height of the circumferential wall section 63 is equal to or greater than the height of the individual teeth 62. A distal end surface of the circumferential wall section 63 is connected to the first covering section 41 of the housing 4, which will be described later. The circumferential wall section 63 can consist of a powder-molded body integrated into the yoke 61, or it can be formed from an element independent of the yoke 61. The circumferential wall section 63, which is an element independent of the yoke 61, is attached to the yoke 61, for example, by an adhesive or a screw. <motorrotor>

[0026] According to the representation in Fig. 1 and Fig. 3 the motor rotor 7 comprises a base section 71 and a magnet 72.

[0027] According to the representation in Fig. The base section 71 is a tubular body with a through-hole. The base section 71 comprises a plurality of internal teeth 30 provided on an inner circumferential surface of the base section 71. The inner rotor 2, which will be described later, is arranged in the through-hole of the base section 71. The internal tooth 30 has a shape and size corresponding to an outer tooth 20 of the inner rotor 2. The base section 71 rotates while an outer circumferential surface of the base section 71 is pressed through a circumferential wall section 40 of the housing 4, which will be described below. A gap is provided between the outer circumferential surface of the base section 71 and an inner circumferential surface of the circumferential wall section 40. A fluid film may be located in this gap. In this case, the base section 71 rotates in a fluid-lubricated state while being assisted by the reaction force of the film.If the film is not present in the space, the base section 71 rotates in a state of boundary lubrication.

[0028] The base section 71 comprises a first surface, a second surface, an inner circumferential surface, and an outer circumferential surface. The first surface faces the first covering section 41 of the housing 4, which will be described later. The second surface faces a second covering section 42 of the housing 4, which will be described later. The inner circumferential surface faces the inner rotor 2, which will be described later. The outer circumferential surface faces the circumferential wall section 40 of the housing 4, which will be described later. Both the inner and outer circumferential surfaces connect the first and second surfaces. The base section 71 is, for example, made of an iron-based material.

[0029] The magnet 72 is located on the first surface of the base section 71. In other words, the magnet 72 is located on a surface of the base section 71 that faces the first covering section 41. In the relationship between the stator 6 and the motor rotor 7, the magnet 72 faces the distal end faces of the teeth 62.

[0030] Magnet 72 is attached to base section 71. The first surface of base section 71 and a surface of magnet 72 are flush with each other. Magnet 72 is attached to base section 71, for example, by an adhesive. For instance, a recess may be provided on the first surface of base section 71, and magnet 72 may be glued to the inside of the recess. Magnet 72 is positioned in the recess so that the first surface of base section 71 and the surface of magnet 72 are flush with each other. Magnet 72 can be attached so that it is embedded in the material of base section 71. Base section 71 may be formed from a resin mold. In this case, magnet 72 may be overmolded with resin, leaving its surface exposed. The resin may be a thermoplastic resin or a thermosetting resin.

[0031] The number of magnets 72 can be one or more. If the number of magnets 72 is one, the shape of the magnet 72 is ring-shaped. In the ring-shaped magnet 72, the S-poles and the N-poles are arranged alternately clockwise or counterclockwise. If there are multiple magnets 72, the multiple magnets 72 are arranged along the entire circumference of the base section 71. If the number of inner teeth 30 of the outer rotor 3 is an even number, the number of magnets 72 can be equal to the number of inner teeth 30 or a multiple of the number of inner teeth 30. The number of magnets 72 can differ from the number of inner teeth 30. The shape of each magnet 72 is, for example, a flat plate. The planar shape of each magnet 72 is, for example, the same as the planar shape of the distal end face of each tooth 62. The magnet 72 is a permanent magnet.

[0032] Each magnet 72 is magnetized in one direction along the rotating shaft of the motor rotor 7. The magnetization directions of the magnets 72 adjacent to each other along the entire circumference of the base section 71 are opposite to each other. The motor rotor 7 rotates with respect to the stator 6 by means of the magnet 72, which repeatedly attracts and repels each tooth 62 by means of a rotating magnetic field generated by the coil 65, which is excited by passing a current through the coil 65 in the stator 6. <innerenrotor>

[0033] According to the representation in Fig. 1 and Fig. In the present embodiment, the inner rotor 2 is arranged in an interior space of the motor rotor 7. The interior space of the motor rotor 7 is configured with a through-hole in the base section 71. The inner rotor 2 is a tubular or block-shaped body with a plurality of external teeth 20. Each external tooth 20 has a tooth shape formed, for example, by a trochoidal curve. In the present embodiment, the number of external teeth 20 is one less than the number of internal teeth 30.

[0034] The inner rotor 2 is rotatably mounted relative to a pin 9. The pin 9 is located in the center of the inner rotor 2. The pin 9 is attached to the second covering section 42 of the housing 4, which will be described later. The inner rotor 2 and the pin 9 can be integrated together, and the pin 9 can be rotatably mounted relative to the second covering section 42. Alternatively, the inner rotor 2 can be rotatably mounted on a shaft (not shown) instead of the pin 9.

[0035] The inner rotor 2 is eccentric with respect to the center of the outer rotor 3. That is, the inner rotor 2 is also eccentric with respect to the center of the plurality of teeth 62, which are arranged in a ring shape. <Außenrotor>

[0036] The outer rotor 3 is the motor rotor 7 described above. The outer rotor 3 comprises a plurality of inner teeth 30 that engage with the plurality of outer teeth 20. The number of inner teeth 30 is one greater than the number of outer teeth 20. A substantially sealed space is formed between the tips of the outer teeth 20 and the inner teeth 30. The number of inner teeth 30 can be even or odd.

[0037] The outer rotor 3 is a drive source. Since the outer rotor 3 is the motor rotor 7, the motor rotor 7 rotates relative to the stator 6, i.e., the outer rotor 3 rotates relative to the stator 6. When the outer rotor 3 rotates, the internal teeth 30 and the external teeth 20 are engaged, so that the inner rotor 2 rotates in the same direction, following the outer rotor 3. In a general internal gear pump, a shaft is provided in an inner rotor, and when the inner rotor rotates, an outer rotor rotates in the same direction, following the rotation of the inner rotor. That is, the drive-side rotor and the output-side rotor in the internal gear pump 1 of the present embodiment are opposite to the drive-side rotor and the output-side rotor in the conventional internal gear pump.The internal gear pump 1 of the present embodiment does not have a shaft, which is provided in the inner rotor of the conventional pump. With the shaftless design, a bearing for rotatable support of the shaft in the housing 4 is not required. <Gehäuse>

[0038] The housing 4 comprises a circumferential wall section 40, a first covering section 41 and a second covering section 42, as shown in Fig. Figure 1 shows the housing 4 rotatably receiving the inner rotor 2 and the outer rotor 3. The peripheral wall section 40, the first covering section 41, and the second covering section 42 form a pump chamber. In the present embodiment, the peripheral wall section 40, the first covering section 41, and the second covering section 42 are formed from independent elements.

[0039] The circumferential wall section 40 is a tubular body that surrounds the outer circumference of the outer rotor 3. That is, the circumferential wall section 40 has a tubular shape. The lateral cross-sectional shape of the tube is circular. The inner diameter of the circumferential wall section 40 is slightly larger than the outer diameter of the outer rotor 3. Therefore, there is a small clearance between the inner circumferential surface of the circumferential wall section 40 and the outer rotor 3. This clearance is chosen so that the outer rotor 3 can rotate while being pressed by the circumferential wall section 40, and so that there is minimal wear or seizing between the circumferential wall section 40 and the outer rotor 3. The length of the circumferential wall section 40 along the axis is slightly longer than the length of the outer rotor 3 along the rotating shaft. The circumferential wall section 40 is made, for example, of an aluminum-based material.If the perimeter wall section 40 is made of an aluminum-based material, the weight of the housing 4 can be reduced.

[0040] The first covering section 41 is a circular plate that covers the first end of the circumferential wall section 40. The first covering section 41 is arranged between the stator 6 and the outer rotor 3. The first covering section 41 has no hole passing through its front and back faces. The first covering section 41 comprises an outer region and an inner region. The outer region is a region that is in contact with an end face of the circumferential wall section 40. The first covering section 41 is attached to the circumferential wall section 40, for example, by a bolt in an outer region. In the present embodiment, part of the outer region of the first covering section 41 is attached to the circumferential wall section 63. The first covering section 41 can be an integral element with the peripheral wall section 40.The first covering section 41 can be an integral element with the circumferential wall section 63 of the stator core 60. The first covering section 41, the peripheral wall section 40 and the peripheral wall section 63 can be an integral element.

[0041] The inner area comprises a region situated between the stator 6 and the outer rotor 3. For example, the initial clearance between the first covering section 41 and the outer rotor 3 is 0.01 mm to 0.20 mm. If the initial clearance is 0.01 mm or more, the first covering section 41 and the outer rotor 3 barely slide against each other, and the occurrence of wear or seizing between the first covering section 41 and the outer rotor 3 can be suppressed. The initial clearance can be 0.03 mm or more, or 0.05 mm or more. If the initial clearance is 0.20 mm or less, the fluid barely escapes through the clearance to the outer circumference of the outer rotor 3, and the function of the internal gear pump 1 is advantageous. The initial clearance can be 0.17 mm or less, or 0.15 mm or less. The first play can be 0.03 mm to 0.17 mm, or 0.05 mm to 0.15 mm.

[0042] The first clearance correlates with a second clearance between the second covering section 42 and the outer rotor 3, which will be described later. Both the first and second clearances vary depending on the position of the outer rotor 3. The outer rotor 3 moves along its rotating shaft. For example, when the outer rotor 3 is near the first covering section 41, the first clearance is relatively small and the second clearance is relatively large. The value of the first clearance in the above range represents a value in a state where the second covering section 42 and the outer rotor 3 are in contact with each other, i.e., a value in a case where the second clearance is zero. In other words, the sum of the first clearance and the second clearance is, for example, 0.01 mm to 0.20 mm.

[0043] The first covering section 41 is, for example, made of a non-magnetic material. As described above, the motor rotor 7 is rotated by the rotating magnetic field generated by the coil 65, which is excited by a current flowing through the coil 65 in the stator 6. The current flowing through the coil 65 is, for example, an alternating current. If the first covering section 41 is made of a non-magnetic material, its influence on the magnetic flux from the stator 6 to the motor rotor 7, i.e., from the stator 6 to the outer rotor 3, is less than if the first covering section 41 were made of a magnetic material. With the first covering section 41 made of a non-magnetic material, the outer rotor 3 is easily rotated in the correct direction by the rotating magnetic field of the stator 6.

[0044] The non-magnetic material is, for example, an aluminum-based material. If the first covering section 41 is made of an aluminum-based material, the weight of the housing 4 can be reduced. The aluminum-based material is made of aluminum or an aluminum alloy. The aluminum is pure aluminum with a purity level of 99% by mass or higher. The aluminum alloy contains one additional element, and the remainder is aluminum and unavoidable impurities. The first covering section 41 made of an aluminum alloy is lightweight and exhibits excellent wear resistance.

[0045] The first covering section 41 can be made of a phenolic resin. The first covering section 41 made of phenolic resin has a low weight.

[0046] The thickness of the first covering section 41 is, for example, 0.3 mm to 5 mm. If the thickness of the first covering section 41 is 0.3 mm or more, its strength can be increased, and it will hardly deform, even when the outer rotor 3 slides on it. This minimal deformation of the first covering section 41 improves the sealing performance of the housing 4. Furthermore, if the thickness of the first covering section 41 is 0.3 mm or more, the operating noise generated by the inner rotor 2 and outer rotor 3 will be minimally transmitted to the outside of the housing 4. The thickness of the first covering section 41 can be 0.5 mm or more, or 1 mm or more. If the thickness of the first covering section is 41.5 mm or less, the outer rotor 3 is slightly rotated by the rotating magnetic field of the stator 6.The thickness of the first covering section 41 can be 4 mm or less, or 3 mm or less. The thickness of the first covering section 41 can be 0.5 mm to 4 mm, or 1 mm to 3 mm.

[0047] The second covering section 42 is a circular plate that covers the second end of the circumferential wall section 40. The second covering section 42 comprises an outer region and an inner region. The outer region is in contact with an end face of the circumferential wall section 40. The second covering section 42 is attached to the circumferential wall section 40, for example, by a screw in the outer region. The second covering section 42 can be an integral element with the circumferential wall section 40. The inner region is facing the inner rotor 2 and the outer rotor 3. The second covering section 42 can be made of a non-magnetic material containing an aluminum-based material or a resin containing a phenolic resin, as in the case of the first covering section 41.If the second cover section 42 is made of an aluminum-based material, the weight of the housing 4 can be reduced. The second cover section 42 made of an aluminum alloy is lightweight and exhibits excellent wear resistance. The first cover section 41 and the second cover section 42 can be made of the same material or of different materials.

[0048] The second cover section 42 has an intake opening 421 and an outlet opening 422, which are connected to the interior of the housing 4. The intake opening 421 and the outlet opening 422 are flow paths. The intake opening 421 and the outlet opening 422 are located opposite each other in the center of the outer rotor 3. The intake opening 421 and the outlet opening 422 are arranged so that they face the gap between the inner rotor 2 and the outer rotor 3. The intake opening 421 and the outlet opening 422 of the present embodiment are both arc-shaped holes. The intake opening 421 and the outlet opening 422 of the present embodiment extend along the rotating shaft of the outer rotor 3 and are open at the end face of the second cover section 42. The intake opening 421 and the exhaust opening 422 can, for example, be bent in an L-shape.In this case, the intake port 421 and the outlet port 422 are open in a direction that intersects the rotating shaft of the outer rotor 3. The intake port 421 and the pressure port 422 can be opened in any direction, depending on the shape of the lines connected to the internal gear pump 1.

[0049] The internal gear pump 1 of the present embodiment operates as follows. First, the outer rotor 3 is rotated by the rotating magnetic field generated by the coil 65, which is energized by passing a current through the coil 65 in the stator 6. As the outer rotor 3 rotates, the inner tooth 30 and the outer tooth 20 mesh, causing the inner rotor 2 to rotate in the same direction, following the outer rotor 3. The volume of the space formed by the respective tooth tips of the inner tooth 30 and the outer tooth 20 increases and decreases with the rotation of the outer rotor 3 and the inner rotor 2. The fluid drawn in through the intake port 421 is expelled through the outlet port 422 by this expansion and contraction. The fluid can be, for example, oil. The fluid can also be water or a refrigerant. LIST OF REFERENCE MARKS 1 Internal gear pump 2 inner rotors 20 Outer tooth 3 Outer rotor 30 Inner tooth 4 cases 40 Perimeter wall section 41 first covering section 42 second covering section 421 Intake opening 422 Outlet opening 5 Axial gap motor 6 Stator 60 stator core 61 yoke 62 teeth 63 Perimeter wall section 65 Coil 7 Motor rotor 71 Basic section 72 Magnet 9 pens. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-202209

[0001] JP 2020 - 182269

[0003] < / innerenrotor> < / motorrotor> < / stator> < / axialspaltmotor>

Claims

[1] Internal gear pump with an internal rotor with a multitude of external teeth; an outer rotor with a multitude of internal teeth that mesh with the multitude of external teeth; a housing that rotatably accommodates the inner rotor and the outer rotor; and an axial gap motor with a stator and a motor rotor, where the outer rotor is the motor rotor, the housing includes: a circumferential wall section provided in a cylindrical shape to surround an outer circumference of the outer rotor, and a first covering section and a second covering section, each covering one of the two corresponding end sections of the perimeter wall section, wherein the first covering section is arranged between the stator and the outer rotor, and wherein the second covering section has an intake opening and an exhaust opening which are connected to an inside of the housing. [2] Internal gear pump according to claim 1, wherein the first covering section is made of a non-magnetic material. [3] Internal gear pump according to claim 1 or claim 2, wherein the thickness of the first covering section is 0.3 mm to 5 mm. [4] Internal gear pump according to one of claims 1 to 3, wherein the clearance between the first covering section and the outer rotor is 0.01 mm to 0.20 mm.

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