pump

Abstract

The pump includes a housing, a stator disposed within the housing, an outer gear disposed within the stator, an inner gear disposed within the outer gear, a shaft disposed in the center of the inner gear, and a bearing coupled to one end of the shaft, the shaft including a first region coupled to the inner gear and a second region coupled to the bearing, the center of the first region and the center of the second region being different from each other.

Description

[Technical field]

[0001] This embodiment relates to a pump. [Background technology]

[0002] The pump includes a motor region that generates a rotary driving force and a pump region that generates hydraulic pressure. Therefore, since the motor region and the pump region in the pump are separated from each other, there is a problem that the number of parts and the overall product width increase.

[0003] In general, an EOP includes a housing, a stator disposed in the housing, and an outer gear and an inner gear disposed in the stator, wherein the outer gear has a placement area defined by a can disposed between the outer gear and the stator, and the inner gear has a placement area defined by a cover coupled to the housing.

[0004] According to the above-mentioned structure, since the arrangement areas of the outer gear and the inner gear are set by different parts, there is a problem that an accumulated tolerance occurs between the multiple parts in the pump.

[0005] Furthermore, since the conventional EOP does not have a means to support the axial load applied to the outer rotor, the rotation stability of the outer or inner rotor decreases due to the force applied from the pump outlet as the working pressure inside the pump increases. In particular, when high pressure of 3 bar or more is generated, friction with the housing occurs due to the misalignment of the outer rotor axis, which is a factor in reducing the performance of the pump. Summary of the Invention [Problem to be solved by the invention]

[0006] The present embodiment provides a pump that can improve the structure and the ease of assembly, thereby improving production efficiency.

[0007] In addition, the pump provides a pump that can minimize the tolerance between the outer gear and the inner gear and control the eccentricity.

[0008] The present invention also provides a pump that can evenly distribute hydraulic load and improve hydraulic pressure drop within the pump.

[0009] The present invention also provides a pump that can be reduced in size and made compact. [Means for solving the problem]

[0010] The pump according to this embodiment includes a housing, a stator disposed within the housing, an outer gear disposed within the stator, an inner gear disposed within the outer gear, a shaft disposed in the center of the inner gear, and a bearing coupled to one end of the shaft, the shaft including a first region coupled to the inner gear and a second region coupled to the bearing, and the center of the first region and the center of the second region are different from each other.

[0011] A cross-sectional area of ​​the first region can be greater than a cross-sectional area of ​​the second region.

[0012] The outer gear and the inner gear are capable of eccentric rotation.

[0013] The axial length of the first region may correspond to the axial lengths of the inner gear and the outer gear.

[0014] The length of the second region may be smaller than the length of the first region in the axial direction.

[0015] The length of the second region may be equal to or less than half the length of the first region.

[0016] The centre of the first region may correspond to a centre of rotation of the inner gear.

[0017] The centre of the second region may correspond to a centre of rotation of the outer gear.

[0018] The distance between the center of the first region and the center of the second region in the radial direction may be 0.02 mm or less.

[0019] The inner gear may include a first hole with which the first region is coupled, and the bearing may include a second hole with which the second region is coupled. Effect of the Invention

[0020] According to this embodiment, the eccentricity between the outer gear and the inner gear can be set through the eccentricity between multiple regions of the shaft, which has the advantage of improving the precision of assembly between multiple parts.

[0021] In addition, since the rotating structure including the bearings can be aligned through a single shaft, there is an advantage in that the overall size of the product can be reduced in the axial direction.

[0022] In addition, since the inner gear, the outer gear and the shaft are connected to each other simply by assembling the shaft and the inner gear and the shaft and the outer gear, there is an advantage in that the number of assembly steps is reduced, thereby improving production efficiency. [Brief description of the drawings]

[0023] [Figure 1] 1 is a perspective view of a pump according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an exploded perspective view of a pump according to an embodiment of the present invention. [Diagram 3] FIG. 2 is an exploded perspective view of an outer gear, an inner gear, and a cover according to an embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a pump according to an embodiment of the present invention. [Diagram 5] A drawing showing Figure 4 from another angle. [Figure 6] 4 is a cross-sectional view showing a coupling structure of a cover, an outer gear, an inner gear and a bearing according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] However, the technical concept of the present invention is not limited to some of the embodiments described, but can be embodied in various different forms, and one or more of the components of the embodiments can be selectively combined or substituted for each other within the scope of the technical concept of the present invention.

[0026] Furthermore, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted in the sense that they are commonly understood by a person having ordinary knowledge in the technical field to which the present invention belongs, unless otherwise clearly and specifically defined, and commonly used terms, such as terms defined in a dictionary, may be interpreted in the context of the relevant art.

[0027] In addition, the terms used in the examples of the present invention are intended to describe the examples and are not intended to limit the present invention. In this specification, the singular form can include the plural form unless otherwise specified, and when it is described as "A and (and) at least one (or more) of B and C," it can include one or more of all combinations of A, B, and C.

[0028] Additionally, terms such as first, second, A, B, (a), (b), etc. may be used to describe components of embodiments of the present invention.

[0029] These terms are used only to distinguish a component from other components, and are not intended to limit the essence, order, or sequence of the components.

[0030] Furthermore, when a component is described as being "coupled," "coupled," or "connected" to another component, it can include not only when the component is directly coupled, coupled, or connected to the other component, but also when the component is "coupled," "coupled," or "connected" by another component between the component and the other component.

[0031] In addition, when described as being formed or disposed "above (above) or below (below)" each component, "above (above) or below (below)" includes not only the case where two components are in direct contact with each other, but also the case where one or more other components are formed or disposed between the two components. In addition, when expressed as "above (above) or below (below)," it can include not only the upward direction based on one component, but also the downward direction.

[0032] The term "axial direction" as used below is defined as the direction that forms the center of rotation of the inner gear or the outer gear. The term "axial direction" may also be the direction in which the exploded configuration is joined with reference to FIG. 2.

[0033] The term "radial direction" used below is defined as a direction perpendicular to the aforementioned "axial direction." The term "radial direction" can be defined as the direction in which the first lobe protrudes from the inner surface of the outer gear, and the direction in which the second lobe protrudes from the inner surface of the inner gear.

[0034] The "circumferential direction" used below can be defined as the circumferential direction of either the stator, the outer gear, or the inner gear, or the circumferential direction of an area that forms a virtual concentric circle with the circumferential direction of either the stator, the outer gear, or the inner gear.

[0035] FIG. 1 is an oblique view of a pump according to an embodiment of the present invention, FIG. 2 is an oblique view of a pump according to an embodiment of the present invention, FIG. 3 is an exploded oblique view of an outer gear, an inner gear and a cover according to an embodiment of the present invention, FIG. 4 is a cross-sectional view of a pump according to an embodiment of the present invention, FIG. 5 is a drawing showing FIG. 4 from another angle, and FIG. 6 is a cross-sectional view showing the connection structure of the cover, outer gear, inner gear and bearing according to an embodiment of the present invention.

[0036] 1 to 6, a pump 10 according to an embodiment of the present invention may have an outer shape formed by combining a housing 100 and a cover 200. The cover 200 may be combined with a lower surface of the housing 100. The housing 100 and the cover 200 may be screw-combined with each other via a screw 290. The housing 100 and the cover 200 may each include a first coupling portion 112 and a second coupling portion 230 to which the screw 290 is combined. The first coupling portion 112 and the second coupling portion 230 may be disposed to face each other in a vertical direction, and each may include a hole to which the screw 290 is combined.

[0037] The cover 200 may include an opening. In detail, a first opening through which a fluid is drawn and a second opening through which a circulated fluid is discharged may be formed on one side of the cover 200. A third opening 212 connected to the first opening and a fourth opening 214 connected to the second opening may be formed on the other side of the cover 200. The first opening and the second opening may be formed on a lower surface of the cover 200, and the third opening 212 and the fourth opening 214 may be formed on an upper surface of the cover 200 coupled to the housing 100.

[0038] A mounting portion 210 may be disposed on an upper surface of the cover 200, protruding upward and coupled to a space within the can 470, which will be described later. Thus, the cover 200 can be understood as including a cover body and the mounting portion 210 protruding from an upper surface of the cover body.

[0039] The cross section of the mounting part 210 may be circular. The mounting part 210 may be screwed into the space in the can 470. The cross section of the mounting part 210 may correspond to the cross section of the space in the can 470. A ring-shaped sealing member 220 for sealing may be disposed between the outer circumferential surface of the mounting part 210 and the inner surface of the space in the can 470. The sealing member 220 is made of a rubber material and may prevent fluid from leaking between the outer circumferential surface of the mounting part 210 and the inner surface of the space in the can 470. The outer surface of the mounting part 210 may be recessed from other regions to form a groove into which the sealing member 220 is coupled.

[0040] The cover 200 may have a third opening 212 through which a fluid is drawn and a fourth opening 214 through which the drawn fluid is discharged on an upper surface thereof. The fluid may be oil. The third opening 212 and the fourth opening 214 may each be formed to have an arc shape, and may be spaced narrower from one side to the other. More specifically, the wide side of the third opening 212 may face the wide side of the fourth opening 214, and the narrow side of the third opening 212 may face the narrow side of the fourth opening 214.

[0041] The third opening 212 and the fourth opening 214 may be formed on an upper surface of the mounting part 210 .

[0042] The housing 100 is made of, but not limited to, a resin or plastic material.

[0043] The housing 100 may include an upper region 120 and a lower region 110. The upper region 120 may have a rectangular cross section. The lower region 110 is disposed below the upper region 120 and may have a circular cross section.

[0044] A second space 122 may be formed inside the upper region 120. The second space 122 may have a groove shape. A number of electronic components for driving may be disposed in the second space 122. For example, a printed circuit board (not shown) and terminals 395 may be disposed in the second space 122. A number of elements may be mounted on the printed circuit board.

[0045] The housing 100 may include a first partition 101 (see FIG. 2) that divides the upper region 120 and the lower region 110. A hole may be formed at the center of the first partition 101 to which a first protrusion 478 of a can 470 (to be described later) is coupled.

[0046] A separate cover (not shown) may be coupled to the upper surface of the housing 100 to cover the second space 122. In this case, the separate cover may be referred to as a second cover, and the cover 200 may be referred to as a first cover 200.

[0047] A stator 300 and a gear may be disposed in the housing 100. The gear may be coupled onto the cover 200.

[0048] The stator 300 may be disposed within the housing 100 .

[0049] The stator 300 may be integrally formed with the housing 100 by double injection. The stator 300 and the housing 100 may be integrally formed by insert injection. The stator 300 may be molded in the housing 100. A stator accommodating space in which the stator 300 is disposed may be formed in the housing 100. The stator accommodating space may be disposed outside the first space 114. An outer surface of the stator 300 may be surrounded by the housing 100.

[0050] The stator 300 may include a stator core 320 and a coil 310 wound around the stator core 320. The stator 300 may include an insulator (not shown) disposed to enclose an outer surface of the core. The coil 310 may be wound around an outer surface of the insulator.

[0051] A router 390 is disposed on the upper surface of the stator core 320, and the coils 310 protruding above the stator core 320 may be aligned by the router 390.

[0052] A bus bar 340 is disposed on an upper surface of the router 390, and ends of the coils 310 protruding above the stator core 320 may be fused to the bus bar 340.

[0053] A terminal 395 may be disposed on an upper surface of the router 390, and the terminal 395 may have a shape that protrudes upward from the router 390. The printed circuit board may be electrically connected to the terminal 395.

[0054] The first space 114 may be formed at the center of the housing 100. The first space 114 may be formed inside the lower region 110. The first space 114 may be a groove in which a portion of the lower surface of the housing 100 is recessed upward. An arrangement area of ​​the stator 300 and the first space 114 may be partitioned by a second partition wall (not shown). An inner surface of the second partition wall may form an inner surface of the first space 114. That is, the second partition wall may be disposed between the stator 300 and an outer gear 410, which will be described later. The second partition wall may be formed to a thickness of 0.2 mm to 1 mm.

[0055] The second space 122 and the first space 114 may be vertically partitioned by a first partition 101. A lower surface of the first partition 101 may form an upper surface of the first space 114. The first space 114 and the second space 122 may be partitioned into different regions by the first partition 101. Thus, the fluid in the first space 114 may be prevented from flowing into the second space 122.

[0056] The gears may be disposed inside the stator 300. The gears may include an outer gear 410 and an inner gear 450. The outer gear 410 and the inner gear 450 may be disposed in the first space 114.

[0057] The outer gear 410 may be disposed inside the stator 300. The second partition wall may be disposed between the outer gear 410 and the stator 300.

[0058] The outer gear 410 may include a core 411 and a magnet 412 attached to the core 411. The magnet 412 may be disposed on an outer circumferential surface of the core 411 to correspond to the coil 310. The outer gear 410 may be a surface permanent magnet (SPM) type in which the magnet 412 is attached to the outer circumferential surface of the core 411. For this reason, a groove in which the magnet 412 is attached may be formed on the outer circumferential surface of the core 411. A plurality of the grooves may be provided and may be disposed spaced apart from each other along the circumferential direction.

[0059] A magnet guide 414 protruding outward may be formed on an outer circumferential surface of the core 411. A plurality of magnet guides 414 may be provided and spaced apart from each other along the circumferential direction. A groove to which the magnet 412 is coupled may be formed between the plurality of magnet guides 414. The magnet guide 414 may support a side surface of the magnet 412.

[0060] The axial length of the magnet guide 414 may be smaller than the axial length of the magnet 412. A side surface of the magnet guide 414 facing a side surface of the magnet 412 may be formed with an inclined surface having a circumferential length that increases toward the outside. And, a side surface of the magnet 412 facing the side surface of the magnet guide 414 may also be formed with an inclined surface corresponding to the inclined surface.

[0061] When a current is applied to the coil 310 of the stator 300, the outer gear 410 can rotate due to electromagnetic interaction between the stator 300 and the outer gear 410.

[0062] A first hole in which the inner gear 450 is disposed may be formed at the center of the outer gear 410. A plurality of ridges protruding inward from the inner peripheral surface and a plurality of valleys disposed between the plurality of ridges may be formed on an inner peripheral surface of the first hole. That is, a first gear in which a plurality of ridges and valleys are alternately disposed may be formed on the inner peripheral surface of the first hole.

[0063] The inner gear 450 may be disposed inside the outer gear 410. The inner gear 450 may be disposed in the first hole. The outer gear 410 may be called an outer rotor, and the inner gear 450 may be called an inner rotor.

[0064] The outer circumferential surface of the inner gear 450 may include a number of ridges 454 protruding outward from the outer circumferential surface, and valleys 458 disposed between the ridges 454. The outer circumferential surface of the inner gear 450 may be formed with a second gear in which the ridges 454 and the valleys 458 are alternately disposed.

[0065] That is, the inner gear 450 may have a second lobe having N gear teeth arranged in a circumferential direction and facing radially outward with respect to a rotation center. The outer gear 410 may have N+1 first lobes facing radially inward. The first lobes may be arranged to overlap with the second lobes. When the outer gear 410 rotates, the inner gear 450 may rotate due to the first and second lobes. The rotation of the inner gear 450 may allow fluid to flow into a space within a can 470, which will be described later, or allow fluid in the space within the can 470 to be discharged to the outside.

[0066] The outer gear 410 and the inner gear 450 can rotate eccentrically. Due to the eccentricity between the outer gear 410 and the inner gear 450, a volume capable of transporting a fluid fuel is generated between the outer gear 410 and the inner gear 450, and the increased volume portion draws in the surrounding fluid due to a pressure drop, and the decreased volume portion discharges the fluid due to an increase in pressure.

[0067] The inner gear 450 and the outer gear 410 may be disposed so that their centers do not coincide with each other. The outer gear 410 and the inner gear 450 may have different rotation centers.

[0068] The inner gear 450 may have a hole 452 formed at its center to which the shaft 250 (to be described later) is coupled.

[0069] The pump 10 may include a can 470. The can 470 may be disposed in the first space 114. The can 470 may be made of a metal material. The can 470 may be integrally formed with the housing 100 by double injection molding. However, this is merely an example, and the can 470 may also be made of a plastic material.

[0070] The can 470 may include a body portion 472 , a lower end portion 474 protruding outward from a lower end of the body portion 472 , and a first protrusion portion 478 protruding upward from an upper surface of the body portion 472 .

[0071] A space may be formed inside the body portion 472. The inner gear 450 and the outer gear 410 may be disposed in the space. The cross-sectional shape of the body portion 472 may be formed to correspond to the cross-sectional shape of the first space 114. As an example, the cross-sectional shape of the body portion 472 may be circular.

[0072] The lower end 474 may be formed to be bent outwardly and extend from the lower end of the body 472. The lower end 474 may be disposed between the lower surface of the housing 100 and the upper surface of the cover 200.

[0073] The first protrusion 478 may be coupled to a hole in the first partition 101. The cross-sectional shape of the first protrusion 478 may be formed to correspond to the cross-sectional shape of the hole. An upper end of the first protrusion 478 may protrude upward from an upper surface of the first partition 101.

[0074] A bearing space for accommodating a bearing 490 (described later) may be formed inside the first protrusion 478. The first protrusion 478 may be formed to have a smaller cross-sectional area than the body 472.

[0075] The can 470 can prevent the fluid in the first space 114 from flowing into the second space 122 .

[0076] The pump 10 may include a support 430. The support 430 may be coupled to the outer gear 410 and support the outer gear 410 in the first space 114. The support 430 may have a circular cross-sectional shape and may be coupled to an upper portion of the outer gear 410. The support 430 may be coupled to the outer gear 410 by pressing.

[0077] The support 430 may include a base 432 disposed on one side of the outer gear 410. As an example, the base 432 may be coupled to an upper surface of the outer gear 410. The cross-sectional area of ​​the base 432 may be smaller than the cross-sectional area of ​​the outer gear 410. A hole through which a shaft 250, which will be described later, passes may be formed in the center of the base 432.

[0078] The support 430 may include a coupling portion 434 that protrudes downward from an end region of the base 432 and couples with a side surface of the outer gear 410. The coupling portion 434 may be disposed between an outer surface of the core 411 and an inner surface of the magnet 412. The inner surface of the coupling portion 434 may face the outer surface of the core 411, and the outer surface of the coupling portion 434 may face the inner surface of the magnet 412. The lower end of the coupling portion 434 may contact an upper surface of the magnet guide 414. The coupling portion 434 may be pressed between the outer surface of the core 411 and the inner surface of the magnet 412.

[0079] In detail, the support 430 may be disposed between the magnet 412 and the core 411. Thus, the core 411 may include a lower region in which the magnet guide 414 is disposed on an outer circumferential surface, and an upper region disposed on an upper portion of the lower region and to which the support 430 is coupled on an outer circumferential surface. The cross-sectional area of ​​the upper region may be smaller than that of the lower region. The cross-sectional area of ​​the space within the support 430 may correspond to the cross-sectional area of ​​the upper region.

[0080] When the support 430 is coupled to the outer circumferential surface of the upper region, the inner surface of the support 430 may be disposed to face the outer surface of the upper region and the outer surface of the support 430 may be disposed to face the inner surface of the magnet 412. Adhesive regions may be formed between the inner surface of the support 430 and the outer surface of the upper region and between the outer surface of the support 430 and the inner surface of the magnet 412. A lower end of the support 430 may contact an upper surface of the lower region.

[0081] The support 430 may include a second protrusion 436 protruding upward from an upper surface. The second protrusion 436 may protrude from an upper surface of the base 432 in a direction opposite to a protruding direction of the coupling portion 434. That is, the second protrusion 436 may protrude upward from an upper surface of the base 432. The second protrusion 436 may have a smaller cross-sectional area than the base 432 and may have a circular cross-sectional shape. The second protrusion 436 may be disposed in a bearing space within the first protrusion 478 of the can 470. The second protrusion 436 may be disposed to overlap the first partition wall 101 in a horizontal direction. The second protrusion 436 has a ring-shaped cross section with a space formed inside, and the bearing 490 may be disposed in the inner space of the second protrusion 436.

[0082] The support 430 may be positioned to form the same center of rotation as the outer gear 410 .

[0083] The pump 10 may include a bearing 490. The bearing 490 may be disposed in the bearing space. The bearing 490 may be a ball bearing. Thus, the bearing 490 may include a ball disposed between an outer ring and an inner ring. A coupling hole 495 (see FIG. 3) may be formed in the center of the bearing 490. The shaft 250, which will be described later, may be coupled to the coupling hole 495. The shaft 250 may be pressed into the coupling hole 495. The shaft 250 may be coupled to the inner ring. An outer surface of the shaft 250 may contact an inner surface of the inner ring. Therefore, when the support 430 rotates together with the outer gear 410, the bearing 490 may support the rotation of the shaft 250. The shaft 250 may rotate integrally with the bearing 490 and the outer gear 410.

[0084] Meanwhile, an upper surface of the second protrusion 436 and an upper surface of the bearing 490 may be spaced apart from a lower surface of the first protrusion 478 .

[0085] The pump 10 may include a shaft 250. The shaft 250 may support the rotation of the inner gear 450 or the outer gear 410. The shaft 250 may have a shape that protrudes upward from an upper surface of the cover 200. The shaft 250 may have a shape that protrudes upward from an upper surface of the mounting part 210. The shaft 250 may be formed integrally with the cover 200.

[0086] The shaft 250 may include a first region 252 that is coupled to the inner gear 450 and a second region 254 that is coupled to the bearing 490. The first region 252 may be coupled to a hole 452 of the inner gear 450, and the second region 254 may be coupled to a coupling hole 495 of the bearing 490.

[0087] The first region 252 may have a shape that protrudes upward from an upper surface of the cover 200. The first region 252 may have a first diameter. The first region 252 may have a first length (L1, see FIG. 6) based on the axial direction.

[0088] The second region 254 may have a shape that protrudes upward from an upper surface of the first region 252. The second region 254 may have a second diameter smaller than the first diameter. The second region 254 may have a second length (L2) smaller than the first length (L1) based on the axial direction. Here, the second length (L2) may be equal to or smaller than ½ of the first length (L1). The cross-sectional area of ​​the first region 252 may correspond to the cross-sectional area of ​​the hole 452. The cross-sectional area of ​​the second region 254 may correspond to the cross-sectional area of ​​the coupling hole 495.

[0089] The axial length of the first region 252 may correspond to the axial length of the inner gear 450 or the outer gear 410 .

[0090] The first region 252 and the second region 254 may each have a circular cross section. The first region 252 and the second region 254 may have centers different from each other. The center (O1) of the first region 252 may be different from the center (O2) of the second region 254. The first region 252 and the second region 254 may be disposed eccentrically. A distance between the center of the first region 252 and the center of the second region 254 based on the radial direction of the shaft 250 may be 0.02 mm or less.

[0091] The center (O1) of the first region 252 may correspond to the rotation center of the inner gear 450. The center (O2) of the second region 254 may correspond to the rotation center of the outer gear 410. Thus, the rotation of the bearing 490 and the outer gear 410 may be supported around the second region 254, and the rotation of the inner gear 450 may be supported around the first region 252.

[0092] According to the above-mentioned structure, since the amount of eccentricity between the outer gear and the inner gear can be set by the amount of eccentricity between the first region and the second region, it has an advantage that the precision of assembly between multiple parts can be improved.

[0093] In addition, since the rotating structure including the bearings can be aligned through a single shaft, there is an advantage in that the overall size of the product can be reduced in the axial direction.

[0094] In addition, since the inner gear, the outer gear and the shaft are connected to each other simply by assembling the shaft and the inner gear and the shaft and the outer gear, there is an advantage in that the number of assembly steps is reduced and production efficiency is improved.

[0095] Although all components constituting the embodiments of the present invention have been described as being combined or operated in combination, the present invention is not necessarily limited to such an embodiment. That is, all components may be selectively combined and operated in one or more combinations within the scope of the present invention. In addition, the terms "comprise", "comprise", "have" and the like described above mean that the component may be present, unless otherwise specified, and should be interpreted as including other components without excluding other components. All terms, including technical or scientific terms, have the same meaning as commonly understood by a person having ordinary skill in the art to which the present invention belongs, unless otherwise defined. Commonly used terms, such as dictionary-defined terms, should be interpreted as being consistent with the contextual meaning of the relevant art, and should not be interpreted as being idealized or overly formal unless clearly defined in the present invention.

[0096] The above description is merely an illustrative example of the technical concept of the present invention, and a person having ordinary knowledge in the technical field to which the present invention belongs may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are for illustrative purposes only and do not limit the technical concept of the present invention. The scope of the present invention should be interpreted according to the following claims, and all technical concepts within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims

1. Housing and a stator disposed within the housing; an outer gear disposed within the stator; an inner gear disposed within the outer gear; a shaft disposed at the center of the inner gear; a bearing coupled to one end of the shaft; the shaft includes a first region that couples with the inner gear and a second region that couples with the bearing; A pump, wherein a center of the first region and a center of the second region are different from each other.

2. The pump of claim 1 , wherein a cross-sectional area of ​​the first region is greater than a cross-sectional area of ​​the second region.

3. The pump of claim 1 , wherein the outer gear and the inner gear rotate eccentrically.

4. The pump of claim 1 , wherein an axial length of the first region corresponds to an axial length of the inner gear and the outer gear.

5. The pump of claim 1 , wherein a length of the second region is smaller than a length of the first region in an axial direction.

6. 6. The pump of claim 5, wherein the length of the second region is less than or equal to one-half the length of the first region.

7. The pump of claim 1 , wherein a center of the first region corresponds to a center of rotation of the inner gear.

8. The pump of claim 1 , wherein a center of the second region corresponds to a center of rotation of the outer gear.

9. The pump according to claim 1 , wherein a distance between a center of the first region and a center of the second region in a radial direction is 0.02 mm or less.

10. the inner gear includes a first hole to which the first region is coupled; The pump of claim 1 , wherein the bearing includes a second hole to which the second region is coupled.

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