Motor and method of manufacturing a motor

Abstract

Provided is a motor and a manufacturing method for a motor, which can suppress dynamic imbalance of a rotor and further can suppress a decrease in motor characteristics. In a motor portion (20), a rotor center position (C1), a magnet center position (C2), and a stator center position (C3) are offset, a length L1 between mutually facing inner wall surfaces (44i) of each magnet holder (44A, 44B) in the axial direction, a magnet length L2 of the magnet (43A), the magnet (43B) in the axial direction, and an offset length L3 satisfy L1-L2

Description

TECHNICAL FIELD

[0001] The present application relates to a motor and a manufacturing method of a motor. BACKGROUND

[0002] For example, in a motor, as a brushless motor, a so-called inner rotor type motor including a stator in which a winding is wound and a rotor rotatably provided at a radially inner side of the stator is known. In an outer peripheral portion of the rotor, permanent magnets (hereinafter referred to as magnets) are arranged in a manner that magnetic poles of opposite polarity are alternately arranged in a circumferential direction. On the other hand, the stator includes a cylindrical stator core that surrounds the periphery of the rotor, a plurality of teeth that protrude from the stator core toward the radially inner side, and a winding wound on the teeth.

[0003] When the motor supplies power to the winding, a predetermined magnetic field is formed on the stator, the magnetic field is received, and magnetic attractive force or repulsive force is generated between the magnetic field and the magnets, whereby the rotor continuously rotates.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: International Publication No. 2017 / 002869 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the structure of the conventional rotor, when the magnets are close to the end surface side of the rotation axis, the center of gravity is far from the center position of the rotation axis (rotor), and there are disadvantages such as large dynamic imbalance due to slight vibration.

[0009] In addition, in the case where the center of gravity of the magnets is close to the center position of the rotor, the center position of the magnets deviates from the center position of the axis of the stator, and the effective magnetic flux of the magnets cannot effectively assist the rotational torque of the rotor, and there is a possibility that the motor characteristics are reduced.

[0010] Therefore, the present application provides a motor and a manufacturing method of a motor that can suppress dynamic imbalance of the rotor and further can suppress reduction of motor characteristics.

[0011] TECHNICAL MEANS FOR SOLVING THE PROBLEMS

[0012] To solve the problem, the motor of the present application includes: a stator having a winding and a stator core in which the winding is wound; a rotor installed at one end of a rotating shaft, rotating by receiving a magnetic field of the stator, the rotor including: a rotor core rotating integrally with the rotating shaft; a magnet disposed at an outer circumferential portion of the rotor core; and two holders provided at both ends of the rotating shaft in an axial direction of the rotor core, limiting movement of the magnet in the axial direction, a center position in the axial direction of the stator core, a center position in the axial direction of the rotor core, and a center position in the axial direction of the magnet are offset, when a length between inner wall surfaces of the two holders facing each other in the axial direction is set as L1, a length in the axial direction of the magnet is set as L2, and a length between the center position in the axial direction of the stator core and the center position in the axial direction of the rotor core is set as L3, each of the lengths L1, L2, and L3 satisfies

[0013] L1-L2

[0014] L3,

[0015] and a length between an end surface of the rotor core and the inner wall surface of each of the holders facing the end surface of the rotor core in the axial direction is the same.

[0016] In the structure, the magnet can abut against the holder on the opposite side of the rotor core from the direction in which the rotor core is offset with respect to the stator core.

[0017] In the structure, the center position in the axial direction of the rotor core can be located closer to the other end of the rotating shaft than the center position in the axial direction of the magnet.

[0018] In the structure, a magnet cover covering an outer circumferential surface of the magnet and having an inner circumferential surface abutting against the outer circumferential surface of the magnet can be further included.

[0019] In the structure, the specific gravity of the rotor core can be greater than the specific gravity of the magnet.

[0020] The manufacturing method of the motor of the structure includes: a magnet cover press-in process of press-in a magnet cover covering an outer peripheral surface of the magnet into the outer peripheral surface of the magnet in a state that the magnet is arranged at an outer peripheral portion of the rotor core and pressing one end of the magnet cover on the retainer; and a magnet cover fixing process of fastening the other end of the magnet cover to the retainer after the magnet cover press-in process.

[0021] Effects of the Invention

[0022] According to the present application, dynamic unbalance of the rotor can be suppressed, and further, a decrease in motor characteristics can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a perspective view showing an appearance of a motor with a speed reducer in an embodiment of the present application.

[0024] Figure 2 is a sectional view showing the motor with the speed reducer in the embodiment of the present application.

[0025] Figure 3 is a sectional view showing a motor portion in the embodiment of the present application.

[0026] Figure 4 is a sectional view showing a rotor in the embodiment of the present application.

[0027] Figure 5 is a perspective view of the rotor in the embodiment of the present application.

[0028] Figure 6 is an exploded perspective view of the rotor in the embodiment of the present application.

[0029] Figure 7 is a plan view of a magnet and a rotor core of the rotor in the embodiment of the present application, as viewed from an axial direction of a rotation axis.

[0030] Figures 8(a) to 8(c) is a sectional view showing a manufacturing process of the rotor in the embodiment of the present application, in which Figures 8(a) to 8(c) each process is shown.

[0031] [Explanation of Symbols]

[0032] 1: Motor with speed reducer (Motor)

[0033] 20: Motor portion (Motor)

[0034] 22: Stator

[0035] 23: Rotor

[0036] 24: Stator core

[0037] 27: rotation shaft

[0038] 27a: end face of rotation shaft (one end)

[0039] 27b: end portion of end face side of rotation shaft (one end)

[0040] 42: rotor core

[0041] 42a, 42b: core end face (end face of rotor core)

[0042] 43A, 43B: magnet

[0043] 43d: outer diameter face of magnet (outer peripheral face of magnet)

[0044] 44A: first magnet holder (holder)

[0045] 44B: second magnet holder (holder)

[0046] 44c: magnet holding portion

[0047] 44i: inner wall face

[0048] 45: magnet cover

[0049] 45d: one end of magnet cover

[0050] 45e: other end of magnet cover

[0051] 46: holder space portion

[0052] 47: core base end portion

[0053] 47b: outer peripheral face of core base end portion (outer peripheral portion of rotor core)

[0054] C1: rotor center position (center position in axial direction of rotor core)

[0055] C2: magnet center position (center position in axial direction of magnet)

[0056] C3: stator center position (center position in axial direction of stator core)

[0057] L1: holder space length

[0058] L2: magnet length

[0059] L3: offset length (length between center position in axial direction of stator core and center position in axial direction of rotor core)

[0060] Lk: space length

[0061] Lh: first holder length / second holder length (length between end surface of rotor core and inner wall surface of holder) DETAILED DESCRIPTION

[0062] Hereinafter, a motor and a manufacturing method of a motor according to an embodiment of the present application will be described with reference to the drawings. Further, in the embodiment, a motor 1 with a reduction gear is exemplified as a motor, but the present application is applicable to other motors.

[0063] < Motor with reduction gear >

[0064] Figure 1 is a perspective view showing an appearance of the motor 1 with a reduction gear.

[0065] As shown in Figure 1 , the motor 1 with a reduction gear is a driving source of an electric component (e.g., a wiper, a power window, a sunroof, a power seat, etc.) mounted on a vehicle, for example. Specifically, the motor 1 with a reduction gear includes a case 10 constituting an outer shell of the motor 1 with a reduction gear, a motor portion 20 provided in the case 10, and a reduction gear portion 30 provided in the case 10 and reducing and outputting rotation of the motor portion 20.

[0066] Figure 2 is a sectional view showing the motor 1 with a reduction gear.

[0067] As shown in Figure 1 , Figure 2 , the case 10 is formed of a material excellent in heat dissipation, such as an aluminum casting, for example. The case 10 includes a shell main body 11 holding the motor portion 20 and the reduction gear portion 30, and a cover 12.

[0068] A reduction gear housing portion 13 housing the reduction gear portion 30 is formed on one side of the shell main body 11. The reduction gear housing portion 13 is a bottomed shape recessed from a top surface portion 11t of the shell main body 11 toward a back surface portion 11b facing the top surface portion 11t. The reduction gear housing portion 13 is surrounded by a bottom portion 13b formed on the back surface portion 11b side, and a peripheral wall portion 13w standing up from an outer peripheral portion of the bottom portion 13b toward the top surface portion 11t.

[0069] In the reduction gear housing portion 13, an axis housing groove 14 housing a worm shaft 31 described later, and a wheel housing recessed portion 15 housing a worm wheel 32 are formed. In the reduction gear housing portion 13, bearing portions 16A, 16B supporting the worm shaft 31 (a rotation axis 27) so as to be rotatable are formed on both end portions in the axis direction of the axis housing groove 14.

[0070] A motor housing portion 17 is integrally formed on the outer peripheral portion of the case main body 11, and extends in a cylindrical shape from the peripheral wall portion 13w toward the outside along the axial direction of the worm shaft 31. The motor housing portion 17 houses a portion of a motor portion 20. An axial insertion hole (not shown) that penetrates the peripheral wall portion 13w and communicates with the bearing portion 16A is formed on the inside of the motor housing portion 17.

[0071] In addition, a boss portion 19 is integrally formed on the case main body 11 so as to protrude from the back surface portion 11b toward the side opposite to the top surface portion 11t. A through hole (not shown) that communicates with the wheel housing recessed portion 15 is formed through the boss portion 19.

[0072] A cover 12 is provided on the top surface portion 11t side of the case main body 11 so as to plug the reduction gear housing portion 13. The cover 12 is fixed to the case main body 11 at a plurality of positions on the outer peripheral portion thereof by means of bolts (not shown). A connector housing portion 12c is formed on the cover 12 so as to be adjacent to the motor housing portion 17 in a state in which the cover 12 is attached to the case main body 11. The connector housing portion 12c is in a cylindrical shape, and is connected to an external power supply connector.

[0073] < Motor portion >

[0074] Figure 3 is a cross-sectional view of the motor portion 20.

[0075] As shown in Figure 3 , the motor portion 20 includes a motor cover 21 that is attached to the motor housing portion 17, a stator 22 that is housed in the motor housing portion 17 and the motor cover 21 and is in a cylindrical shape, and a rotor 23 that is provided on the radially inner side of the stator 22 and is rotatably provided to the stator 22.

[0076] The motor cover 21 is a member that contains a metal such as iron, and is formed in a bottomed cylindrical shape, for example, by press working such as deep drawing. A flange 21a that protrudes toward the radially outer side is formed on the open end of the motor cover 21 (see also Figure 1 ). The motor cover 21 is joined to the motor housing portion 17 by means of a bolt 21b that is inserted through the flange 21a.

[0077] The stator 22 is arranged along the inner peripheral surface of the motor cover 21. The stator 22 includes a stator core 24 that is formed in a substantially cylindrical shape, a plurality of teeth 25 that protrude toward the radially inner side from the stator core 24, and a winding 26 that is wound around the stator core 24.

[0078] The stator core 24 is formed by laminating a plurality of steel sheets 24p. Furthermore, the stator core 24 is not limited to the case where a plurality of metal sheets are laminated, and may, for example, be formed by pressure forming of a soft magnetic powder. The outer peripheral surface of the stator core 24 thus formed is fitted to the inner peripheral surface of the motor cover 21.

[0079] The teeth 25 are formed equi-spaced in the circumferential direction along the radially inner side of the stator core 24. The winding 26 is wound on the teeth 25. The winding 26 generates a magnetic flux for rotating the rotor 23 by a current supplied from a controller substrate not shown.

[0080] Figure 4 is a sectional view of the rotor 23. Figure 5 is a perspective view of the rotor 23.

[0081] As shown in Figure 4 , Figure 5 , the rotor 23 includes a rotation shaft 27 and a rotor main body 28 fitted and fixed to the rotation shaft 27. Further, in the following description, the axial direction of the rotation shaft 27 will be simply referred to as the axial direction.

[0082] The rotor main body 28 includes a rotor core 42 press-fitted into the rotation shaft 27, a magnet (also referred to as "rotor magnet") 43A mounted on the rotor core 42, a magnet 43B, a first magnet holder (holder) 44A for holding the magnets 43A, 43B, a second magnet holder 44B, and a magnet cover 45.

[0083] The first magnet holder 44A and the second magnet holder 44B are arranged to sandwich the magnets 43A, 43B in the axial direction. Thus, the first magnet holder 44A and the second magnet holder 44B prevent the magnets 43A, 43B from falling out of the rotor core 42 in the axial direction.

[0084] < Rotor Core >

[0085] Figure 6 is an exploded perspective view of the rotor 23.

[0086] As shown in Figure 5 , Figure 6 , the rotation shaft 27 is integrally formed with a worm shaft 31 constituting a speed reducer section 30 (see also Figure 2 ). The rotor core 42 is mounted to an end portion (one end) 27b of the rotation shaft 27 on the side of an end face 27a (see Figure 3 ). The rotor core 42 rotates integrally with the rotation shaft 27 by being press-fitted into the outer periphery of the rotation shaft 27. The rotor core 42 is formed by laminating a plurality of metal plates in the axial direction. Further, the rotor core 42 is not limited to the case where a plurality of steel plates are laminated in the axial direction, and may, for example, be formed by pressure molding of soft magnetic powder.

[0087] The rotor core 42 includes a core base end portion 47 formed in a cylindrical shape, and a plurality of core protruding portions 48 protruding radially outward from the core base end portion 47. A through hole 47a penetrating in the axial direction is formed in the radially central portion of the core base end portion 47. The rotation shaft 27 is press-fitted into the through hole 47a (see also Figure 3). Further, the rotating shaft 27 can be inserted into the through hole 47a, and the rotor core 42 can be fixed to the rotating shaft 27 by being fitted from the outside using an adhesive or the like. The plurality of core protrusions 48 protrude at intervals of, for example, 90° in the circumferential direction, and there are four of them.

[0088] < Magnet >

[0089] Figure 7 is a plan view of the magnet 43A, the magnet 43B, and the rotor core 42 as viewed in the axial direction.

[0090] As shown in Figure 6 , Figure 7 , the magnet 43A, the magnet 43B are arranged between the core protrusions 48 that are adjacent in the circumferential direction. The magnet 43A, the magnet 43B are segmented magnets whose axial cross sections are fan-shaped. The magnet 43A, the magnet 43B are arranged in the circumferential direction on the outer circumferential surface (outer circumferential portion) 47b of the core base end portion 47, and there are four of them arranged in a circular ring shape. The magnet 43A, the magnet 43B contain, for example, ferrite magnets. Here, since there are four of the magnet 43A, the magnet 43B, each of them is formed in a sector shape with a central angle θ < 90°.

[0091] The magnet 43A, the magnet 43B are each magnetized from the inner diameter surface (inner circumferential surface) 43c including a circular arc surface to the outer diameter surface (outer circumferential surface) 43d. The magnet 43A, the magnet 43B are configured so that the magnetic poles of the outer diameter surfaces 43d are alternately arranged in opposite polarities in the circumferential direction when arranged in a circular ring shape on the outer circumferential surface of the rotor core 42. That is, for the magnet 43A, the magnet 43B, two types of magnets magnetized in opposite polarities are prepared, and arranged alternately in the circumferential direction on the outer circumferential surface 47b of the core base end portion 47. Therefore, the rotor main body 28 of the assembly having the magnet 43A, the magnet 43B has four magnetic poles.

[0092] The inner diameter surface 43c and the outer diameter surface 43d of the magnet 43A, the magnet 43B are formed in circular arc surfaces. The segmented magnet 43A, the magnet 43B are arranged between the core protrusions 48 that are adjacent in the circumferential direction, and the both end surfaces 43t in the circumferential direction of the magnet 43A, the magnet 43B abut against the adjacent core protrusions 48. Thus, it is possible to prevent the magnet 43A, the magnet 43B from deviating in position with respect to the direction of rotation of the rotor 23.

[0093] In addition, the magnet 43A, the magnet 43B overhang on both sides in the axial direction with respect to the rotor core 42 and the stator core 24. The overhang means a state in which the both end surfaces in the axial direction of the magnet 43A, the magnet 43B protrude from the core end surfaces 42a, 42b on both sides in the axial direction of the rotor core 42.

[0094] < Magnet Holder >

[0095] The first magnet holder 44A and the second magnet holder 44B include a ring-shaped magnet holding portion 44c and a core holding portion 44d formed integrally with the magnet holding portion 44c. As a material of the first magnet holder 44A and the second magnet holder 44B, for example, a non-magnetic resin material can be cited.

[0096] The magnet holding portion 44c is formed in a flat ring shape by forming a radially central opening edge 44e and an outer peripheral edge 44f in a circular arc shape. On the magnet holding portion 44c, the core holding portion 44d is formed integrally on an inner wall surface 44i of a face on the side of the magnets 43A, 43B. The core holding portion 44d includes a ring-shaped portion 44g and a plurality of protruding portions 44h extending radially outward from the ring-shaped portion 44g.

[0097] The ring-shaped portion 44g is formed in a ring shape on the inner wall surface 44i of the magnet holding portion 44c in imitation of the opening edge 44e.

[0098] The plurality of protruding portions 44h extend radially outward from the ring-shaped portion 44g along the inner wall surface 44i of the magnet holding portion 44c to the outer peripheral edge 44f in a radial pattern. The plurality of protruding portions 44h protrude, for example, at intervals of 90° in the circumferential direction, and there are four protruding portions 44h at intervals.

[0099] An end surface of the core base end portion 47 of the rotor core 42 abuts against the ring-shaped portion 44g. An end surface of the core protruding portion 48 of the rotor core 42 abuts against the protruding portion 44h. Specifically, the first magnet holder 44A abuts against the core end surface (end surface) 42a on the opposite side of the end surface 27a of the rotation shaft 27 among the two core end surfaces 42a, 42b of the rotor core 42 (see also FIG. 6). In addition, the second magnet holder 44B abuts against the core end surface (end surface) 42b on the side of the end surface 27a of the rotation shaft 27 among the two core end surfaces 42a, 42b of the rotor core 42. Figure 4

[0100] That is, the first magnet holder 44A and the second magnet holder 44B are arranged on the two core end surfaces 42a, 42b of the rotor core 42 in a manner of sandwiching the rotor core 42 in the axial direction. The magnets 43A, 43B are arranged between the first magnet holder 44A and the second magnet holder 44B. That is, the magnets 43A, 43B are held by the first magnet holder 44A and the second magnet holder 44B so as to be movable in the axial direction, and the above-described movement in the axial direction is limited.

[0101] < Magnet Cover >

[0102] ​The outer periphery of the first magnet holder 44A, the second magnet holder 44B, the rotor core 42, and the magnets 43A, 43B is covered by a magnet cover 45. Further, the first magnet holder 44A and the second magnet holder 44B are held by the magnet cover 45. As the material of the magnet cover 45, for example, a non-magnetic material such as stainless steel can be cited.

[0103] The magnet cover 45 includes a cylindrical portion 45a covering the outer diameter surface 43d of the magnets 43A, 43B, and a first flange 45b and a second flange 45c integrally formed at both axial ends of the cylindrical portion 45a. The cylindrical portion 45a is formed in a hollow cylindrical shape. The inner peripheral surface of the cylindrical portion 45a abuts against the outer diameter surface 43d of the magnets 43A, 43B. Thus, in a state where the both end surfaces 43t of the magnets 43A, 43B abut against (are in close contact with) the core protruding portions 48 of the rotor core 42, the magnets 43A, 43B are held (fixed) by the cylindrical portion 45a.

[0104] In the cylindrical portion 45a, the first flange 45b (also see Figure 4 ) protrudes toward the radial inner side from one end 45d on the opposite side of the end surface 27a of the rotary shaft 27. The first flange 45b abuts against the surface of the magnet holding portion 44c of the first magnet holder 44A.

[0105] In the cylindrical portion 45a, the second flange 45c protrudes toward the radial inner side from the other end 45e on the side of the end surface 27a of the rotary shaft 27. The second flange 45c abuts against the surface of the magnet holding portion 44c of the second magnet holder 44B.

[0106] Thus, the first flange 45b abuts against the surface of the magnet holding portion 44c of the first magnet holder 44A. Also, the second flange 45c abuts against the surface of the magnet holding portion 44c of the second magnet holder 44B. Thus, the first magnet holder 44A and the second magnet holder 44B are held integrally with the rotor core 42 by the magnet cover 45.

[0107] That is, in the rotor 23, for example, in a state where the rotor core 42 is fixed to the rotary shaft 27, the magnets 43A, 43B are fixed to the rotor core 42 by the cylindrical portion 45a of the magnet cover 45. Also, the first magnet holder 44A and the second magnet holder 44B are fixed to the rotor core 42 by the first flange 45b and the second flange 45c of the magnet cover 45. Thus, the rotor 23 is assembled integrally by the rotary shaft 27, the rotor core 42, the magnets 43A, 43B, the first magnet holder 44A, the second magnet holder 44B, and the magnet cover 45.

[0108] Further, in the embodiment, the example in which the magnets 43A, 43B are fixed by the magnet cover 45 is described, but the magnets 43A, 43B can be fixed by an adhesive.

[0109] Positional relationship in the axial direction of the rotor core, the magnets, and the stator core

[0110] Hereinafter, based on Figure 3 , Figure 4 the positional relationship in the axial direction of the rotor core 42, the magnets 43A, 43B, and the stator core 24 will be described.

[0111] As shown in Figure 4 , a holder space portion 46 is formed between the first magnet holder 44A and the second magnet holder 44B.

[0112] Here, when the axial length of the holder space portion 46, that is, the length between the inner wall surfaces 44i of each of the magnet holders 44A, 44B facing each other in the axial direction is set to L1, and the magnet length in the axial direction of the magnets 43A, 43B is set to L2, each of the lengths L1, L2 satisfies:

[0113] L1 > L2 (1)

[0114] Therefore, in the holder space portion 46 between the first magnet holder 44A and the second magnet holder 44B, the magnets 43A, 43B can be held at an arbitrary position in the axial direction.

[0115] In the embodiment, for example, the magnet end surface 43e in the axial direction of the magnets 43A, 43B abuts on the magnet holding portion 44c of the second magnet holder 44B. In addition, the magnet end surface 43f in the axial direction of the magnets 43A, 43B is disposed apart by a space in the axial direction with respect to the magnet holding portion 44c of the first magnet holder 44A. That is, a space having a space length Lk is formed between the magnet end surface 43f and the magnet holding portion 44c. The space length Lk satisfies:

[0116] L1 - L2 = Lk (2)

[0117] In the embodiment, an example in which the magnet end surface 43e abuts on the magnet holding portion 44c is described, but the magnet end surface 43e can be disposed close to the magnet holding portion 44c.

[0118] In addition, the first holder length Lh between the core end surface 42a of the rotor core 42 and the inner wall surface 44i of the magnet holding portion 44c of the first magnet holder 44A and the second holder length Lh between the core end surface 42b of the rotor core 42 and the inner wall surface 44i of the magnet holding portion 44c of the second magnet holder 44B are the same length.

[0119] Here, the magnet end surface 43e abuts against the magnet holding portion 44c, and a space of the space length Lk is formed between the magnet end surface 43f and the magnet holding portion 44c. Thus, the magnet center position C2 of the magnets 43A, 43B in the axial direction is offset (shifted) toward the end surface 27a side of the axial direction with respect to the rotor center position Cl. In other words, the rotor center position Cl is disposed closer to the center of the rotary shaft 27 (i.e., closer to the other end of the end portion (one end) 27b of the rotary shaft 27 opposite to the end surface 27a) than the magnet center position C2. Here, the proportion of the rotor core 42 is generally greater than the proportion of the magnets 43A, 43B. Figure 3

[0120] As shown in FIG. 6, the rotor center position Cl is offset (shifted) toward the side opposite to the axial end surface 27a of the rotary shaft 27 with respect to the stator center position C3. The shift length L3 between the rotor center position Cl and the stator center position C3 is greater than the space length Lk. In other words, the space length Lk is set to be smaller than the shift length L3. Thus, the shift length L3 is set to be greater than the shift length L4 of the magnet center position C2 with respect to the rotor center position Cl. That is, the length LI between the inner wall surfaces 44i of the respective magnet holding frames 44A, 44B facing each other in the axial direction, the magnet length L2 of the magnets 43A, 43B in the axial direction, and the shift length L3 satisfy: Figure 3 L1-L2 < L3 (3)

[0121]

[0122] In addition, the magnet holding portion 44c and the magnet end surface 43e on the side opposite to the shift direction of the rotor center position Cl with respect to the stator center position C3 of the magnets 43A, 43B abut against each other. Thus, the magnet center position C2 is disposed between the stator center position C3 and the rotor center position Cl in the axial direction. That is, the stator center position C3, the magnet center position C2, and the rotor center position Cl are disposed in this order in the direction away from the end surface 27a of the rotary shaft 27. In other words, the magnet center position C2 is located between the stator center position C3 and the rotor center position Cl.

[0123] Thus, in the motor portion 20, the rotor center position (i.e., the center position of the rotor core 42) Cl is offset by the shift length L3 with respect to the stator center position C3 toward the side opposite to the axial end surface 27a (i.e., the center position side of the rotary shaft 27 of the rotor 23). Thus, the magnet center position C2 is disposed on the center position side of the rotary shaft 27 of the rotor 23, and the weight of the magnet center position C2 is close to the center position side of the rotary shaft 27. Thus, when vibration caused by the rotation of the rotor 23 occurs, the dynamic imbalance of the rotor 23 can be suppressed.

[0124] ​​Further, the specific gravity of the rotor core 42 is generally greater than the specific gravity of the magnets 43A, 43B. In addition to this, the rotor center position Cl is disposed closer to the center of the rotation shaft 27 than the magnet center position C2. Thus, the dynamic imbalance of the rotor 23 can be more effectively suppressed.

[0125] Further, the length LI between the inner wall surfaces 44i of the respective magnet holders 44A, 44B facing each other in the axial direction, the magnet length L2 of the magnets 43A, 43B in the axial direction, and the offset length L3 satisfy the equation (3). In other words, the magnet center position C2 is located between the stator center position C3 and the rotor center position Cl. Thus, the weight of the magnet center position C2 can be made closer to the center position side of the rotation shaft 27 of the rotor 23, and the magnet center position C2 can be made closer to the stator center position C3. Thus, the magnetic flux leakage due to the inconsistency between the magnet center position C2 and the stator center position C3 can be suppressed, and the effective magnetic flux of the magnets 43A, 43B can be effectively made to contribute to the rotational torque of the rotor 23. Therefore, the motor characteristics of the motor portion 20 can be suppressed from deteriorating.

[0126] Thus, in the motor 1 with a speed reducer, the magnets 43A, 43B can be held at an arbitrary position in the axial direction in the holder space portion 46 between the first magnet holder 44A and the second magnet holder 44B. Thus, the magnets 43A, 43B can be made to approach the second magnet holder 44B side. Thus, the stator center position C3, the magnet center position C2, and the rotor center position Cl are disposed by being offset in the axial direction, respectively, and the respective center positions C3, C2, and Cl are set at optimum positions. Therefore, the dynamic balance based on the rotor 23 and the motor characteristics can be simultaneously taken into consideration.

[0127] <Speed reducer portion>

[0128] As shown in FIG. 1, the speed reducer portion 30 includes a worm shaft 31 and a worm wheel 32 engaged with the worm shaft 31. Figure 2 The worm shaft 31 is formed in a spiral shape continuously in the outer peripheral surface of the rotation shaft 27 at the intermediate portion of the bearing portions 16A, 16B, and thus is formed as a part of the rotation shaft 27.

[0129] The outer diameter of the worm gear portion 31g is formed larger than the outer diameter of the worm shaft 31 (rotation shaft 27). Such a worm gear portion 31g is formed by roll forming.

[0130] Further, the worm shaft 31 can be formed separately from the rotation shaft 27 of the motor portion 20, and the worm shaft 31 and the rotation shaft 27 can be integrated by being coupled to each other.

[0131]

[0132] ​The worm gear 32 is disc-shaped, and has an outer peripheral gear portion 32g that engages with the worm gear portion 31g of the worm shaft 31 on the outer peripheral surface thereof. The worm gear 32 is housed in the wheel housing recess 15 of the reduction gear housing portion 13 of the housing main body 11.

[0133] In the worm gear 32, an output shaft 33 that protrudes from the radial center of the worm gear 32 is provided on the side facing the bottom portion 13b of the reduction gear housing portion 13. The output shaft 33 is disposed coaxially with the rotation center of the worm gear 32. The front end portion of the output shaft 33 protrudes to the outside of the housing main body 11 via the through hole of the boss portion 19 formed on the housing main body 11. A spline 33a that connects with an electric component not shown is formed on the front end portion of the output shaft 33.

[0134] <Operation of the motor with reduction gear>

[0135] Next, the operation of the motor with reduction gear 1 will be described.

[0136] When electric power is supplied from a controller portion not shown to each winding 26 of the motor portion 20, the motor with reduction gear 1 forms a predetermined magnetic field on the stator 22 (teeth 25). The magnetic field is received, and magnetic attractive force or repulsive force is generated between the magnetic field and the magnets 43A, 43B of the rotor 23. As a result of this, the rotor 23 continues to rotate. When the rotor 23 rotates, the worm shaft 31 that is integrated with the rotation shaft 27 rotates, and the worm gear 32 that engages with the worm shaft 31 rotates. Then, the output shaft 33 that is linked to the worm gear 32 rotates, thereby driving the required electric component.

[0137] <Manufacturing method of the motor>

[0138] Next, a manufacturing method of the rotor 23 will be described in accordance with Figure 3 , Figure 4 , Figures 8(a) to 8(c) , specifically the manufacturing process of the rotor 23. Figures 8(a) to 8(c) is a cross-sectional view that explains the manufacturing process of the rotor 23, Figures 8(a) to 8(c) is a view that shows each process.

[0139] As shown in Fig. 8(a), in a state where the rotor core 42 is fixed to the rotation shaft 27, the first magnet holder 44A abuts against the core end surface 42a of the rotor core 42. In addition, the second magnet holder 44B abuts against the core end surface 42b of the rotor core 42. Furthermore, the magnets 43A, 43B are disposed between the first magnet holder 44A and the second magnet holder 44B. Furthermore, the magnets 43A, 43B are disposed between the adjacent core protruding portions 48 (refer to Fig. 8(b)). Figure 7

[0140] ​In this state, magnets 43A and 43B are freely movable axially in the cage space 46 between the first magnet cage 44A and the second magnet cage 44B.

[0141] The assembled rotating shaft 27, rotor core 42, first magnet holder 44A, second magnet holder 44B, and magnets 43A and 43B are placed on the mounting platform 51. Above the assembled rotating shaft 27, rotor core 42, first magnet holder 44A, second magnet holder 44B, and magnets 43A and 43B, one end 45d of the magnet cover 45 is held in the gripping part 53 of the presser 52. The second flange 45c on the other end 45e of the magnet cover 45 is laid out radially outward in an inclined (divergent) manner without being tightened.

[0142] As shown in Figure 8(b), the magnet cover 45 is lowered using the gripping part 53 of the presser 52. By lowering the magnet cover 45, the second flange 45c of the magnet cover 45 is fitted into the outer diameter surface 43d of the magnets 43A and 43B in the direction of arrow A via the first magnet holder 44A. Thus, the cylindrical part 45a of the magnet cover 45 is fitted into the outer diameter surface 43d of the magnets 43A and 43B.

[0143] Magnets 43A and 43B move together with the cylindrical portion 45a of the magnet cover 45 in the direction of arrow A. As a result, the magnet end faces 43e of magnets 43A and 43B abut against the magnet holding portion 44c of the second magnet holder 44B.

[0144] That is, magnets 43A and 43B move to a position offset relative to the rotor core 42 along the axial direction toward the end face 27a of the rotating shaft 27.

[0145] As shown in Figure 8(c), the cylindrical portion 45a is pressed into the outer diameter surface 43d of the magnets 43A and 43B. Therefore, the first flange 45b of the magnet cover 45 is pressed (aggregated) against the surface of the magnet holding portion 44c of the first magnet holder 44A (magnet cover pressing process). In this state, the second flange 45c of the magnet cover 45 protrudes downwards from the second magnet holder 44B.

[0146] like Figure 4 As shown, by tightening the second flange 45c of the protruding magnet cover 45 radially inward, the second flange 45c abuts against the surface of the magnet holding portion 44c of the second magnet holder 44B (magnet cover fixing process). Thus, as... Figure 3 As shown, the rotating shaft 27, rotor core 42, magnets 43A and 43B, first magnet holder 44A, second magnet holder 44B and magnet cover 45 are integrally assembled into rotor 23, and the manufacturing process of rotor 23 is completed.

[0147] As explained above, according to the manufacturing method of the rotor 23 (i.e., the manufacturing process of the rotor 23), the magnets 43A, 43B are arranged movably in the axial direction in the holder space portion 46 between the first magnet holder 44A and the second magnet holder 44B. Therefore, by pressing the cylindrical portion 45a of the magnet cover 45 into the outer diameter surface 43d of the magnets 43A, 43B, the magnets 43A, 43B can be biased with respect to the rotor core 42.

[0148] Specifically, the magnet center position C2 of the magnets 43A, 43B can be fixed in a state of being offset (biased) by L4 toward the end surface 27a side of the rotor center position Cl with respect to the rotor core 42. Thereby, the rotor 23 in which the magnets 43A, 43B are biased can be simply manufactured. Further, the motor 1 with a reduction mechanism in which the magnet center position C2 is arranged between the stator center position C3 and the rotor center position Cl can be easily manufactured.

[0149] Further, the present application is not limited to the described embodiments, and various modifications can be made to the described embodiments within the scope of the present application.

[0150] For example, the motor 1 with a reduction mechanism is described as a driving source of an electric component (e.g., a wiper, a power window, a sunroof, a power seat, etc.) mounted on a vehicle. However, the motor 1 with a reduction mechanism can be used in various electric devices. In addition, only the motor portion 20 can be used in various electric devices.

Claims

1. A motor characterized by, Comprising: a stator having a winding and a stator core in which the winding is wound; and a rotor installed at one end of a rotating shaft, which rotates by receiving a magnetic field of the stator; the rotor comprising: a rotor core which rotates integrally with the rotating shaft; a magnet disposed at an outer circumferential portion of the rotor core; and two holders provided at both ends in an axial direction of the rotating shaft of the rotor core, which restrict movement in the axial direction of the magnet; a center position in the axial direction of the stator core, a center position in the axial direction of the rotor core, and a center position in the axial direction of the magnet are offset, when a length between inner wall surfaces of the two holders facing each other in the axial direction is set as L1, a length in the axial direction of the magnet is set as L2, and a length between the center position in the axial direction of the stator core and the center position in the axial direction of the rotor core is set as L3, each of the lengths L1, L2, and L3 satisfies: L1 - L2 < L3, and a length between an end surface of the rotor core and the inner wall surface of each of the holders is the same.

2. A motor characterized by, Comprising: a stator having a winding and a stator core in which the winding is wound; and a rotor installed at one end of a rotating shaft, which rotates by receiving a magnetic field of the stator; the rotor comprising: a rotor core which rotates integrally with the rotating shaft; a magnet disposed at an outer circumferential portion of the rotor core; and two holders provided at both ends in an axial direction of the rotating shaft of the rotor core, which restrict movement in the axial direction of the magnet; a length between an end surface of the rotor core and an inner wall surface of each of the holders facing the end surface of the rotor core in the axial direction is the same, a center position in the axial direction of the stator core, a center position in the axial direction of the rotor core, and a center position in the axial direction of the magnet are offset, the center position in the axial direction of the magnet is located between the center position in the axial direction of the stator core and the center position in the axial direction of the rotor core.

3. The motor according to claim 1 or 2, wherein the magnet abuts against the holder on the opposite side of the rotor core with respect to the direction in which the rotor core and the magnet are offset from the stator core.

4. The motor of claim 1 or 2, wherein a center position in the axial direction of the rotor core is located closer to the other end of the rotating shaft than a center position in the axial direction of the magnet.

5. The motor of claim 1 or 2, wherein Further comprising a magnet cover which covers an outer circumferential surface of the magnet and whose inner circumferential surface abuts against the outer circumferential surface of the magnet.

6. The motor according to claim 1 or 2, wherein a specific gravity of the rotor core is greater than a specific gravity of the magnet.

7. A method of manufacturing a motor, the method of manufacturing a motor according to any one of claims 1 to 6, characterized by, Comprising: a magnet cover press-in process in which a magnet cover which covers an outer circumferential surface of the magnet is pressed into the outer circumferential surface of the magnet while the magnet is disposed at an outer circumferential portion of the rotor core, and one end of the magnet cover is pressed against the holder; and a magnet cover fixing process in which the other end of the magnet cover is made to abut against the holder to be fastened after the magnet cover press-in process.

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