Motor

Abstract

A motor (1) comprises: a shaft (2); a rotor (4); and a stator (3). The rotor (4) has: a yoke (41); and first and second magnets (42a, 42b) arranged in the circumferential direction (C). The first and second magnets (42a, 42b) are located in the yoke (41). In the radial direction (R), an end (42a1) of the first magnet (42a) on a side opposite to the stator (3) is located opposite to the stator (3) as compared to an end (42b1) of the second magnet (42b) on the side opposite to the stator (3).

Description

Motor

[0001] The present invention relates to a motor.

[0002] A so-called Halbach array motor is known, in which a plurality of magnets with different magnetic flux directions are arranged on the surface of a rotor yoke (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2007-006545

[0004] However, the motor described above has room for improvement in terms of increasing the output torque.

[0005] In view of the above-mentioned problems, the present invention provides a motor that can improve output torque.

[0006] In order to solve the above-mentioned problems and achieve the object, the motor of the present invention comprises a shaft, a rotor, and a stator, the rotor having a yoke and a first magnet and a second magnet arranged circumferentially, the first magnet and the second magnet are located inside the yoke, and the end of the first magnet opposite the stator in the radial direction is located opposite the end of the second magnet opposite the stator.

[0007] According to one aspect, the output torque of the motor can be improved.

[0008] FIG. 1 is a plan view of a motor according to a first embodiment. FIG. 2 is a perspective view of the motor shown in FIG. 1. FIG. 3 is a perspective view of a rotor included in the motor shown in FIG. 1. FIG. 4 is a perspective view showing a portion of a yoke included in the rotor shown in FIG. 3. FIG. 5 is a plan view showing a portion of the motor shown in FIG. 1. FIG. 6 is a plan view showing the directions of magnetic flux of multiple magnets included in the motor shown in FIG. 1. FIG. 7 is a plan view of a motor according to a first modified example of the first embodiment. FIG. 8 is a perspective view of a rotor included in the motor shown in FIG. 7. FIG. 9 is a plan view showing a portion of a motor according to a second embodiment.

[0009] Motors according to embodiments will be described in detail below with reference to the drawings. Note that the dimensional relationships and ratios of elements in the drawings may differ from the actual situation. The dimensional relationships and ratios may also differ between the drawings.

[0010] FIG. 1 is a plan view of a motor 1 according to a first embodiment. FIG. 2 is a perspective view of the motor 1 shown in FIG. 1. FIG. 3 is a perspective view of a rotor 4 included in the motor 1 shown in FIG. 1. FIG. 4 is a perspective view showing a portion of a yoke 41 included in the rotor 4 shown in FIG. 3. FIG. 5 is a plan view showing a portion of the motor 1 shown in FIG. 1. FIG. 6 is a plan view showing the direction of magnetic flux of a plurality of magnets 42 included in the motor 1 shown in FIG. 1. Note that in FIGS. 1, 2, 5, and 6, the x's located on both sides of teeth 31b (described later) indicate that the windings that are wound around the teeth 31b to form coils 32 are omitted.

[0011] [First embodiment] In the following description of the motor 1 according to the first embodiment, in order to facilitate understanding of directions, the direction in which the shaft 2 described later extends will be referred to as the axial direction A, the direction in which the rotor 4 described later rotates will be referred to as the circumferential direction C, and the direction that is included in a plane perpendicular to the axial direction A, passes through the axis 2o of the shaft 2, and is perpendicular to the circumferential direction C will be referred to as the radial direction R.

[0012] The motor 1 according to the first embodiment shown in FIG. 1 is an inner rotor type motor, as described below. When viewed from the axial direction A, the stator 3 is located radially outward of the rotor 4 relative to the rotor 4, while the shaft 2 is located radially inward of the rotor 4 relative to the rotor 4. In the motor 1 according to this embodiment, the outer side in the radial direction R is referred to as the stator side R1, and the inner side in the radial direction R is referred to as the opposite side of the stator 3, R2. In addition, in FIGS. 1 to 6, the stator side in the radial direction R is indicated by R1, and the opposite side of the stator 3 in the radial direction R is indicated by R2. Note that in FIG. 3, the rotor 4 is shown without some of the multiple magnets 42, which will be described later. Furthermore, for ease of explanation, the shaft 2 is shown by a virtual line in FIG. 1, and is omitted in the other drawings.

[0013] The motor 1 according to the first embodiment is, for example, an electric motor that converts electrical energy from a power source into driving force that rotates the shaft 2 in the circumferential direction C. The motor 1 according to this embodiment is also a so-called flat motor in which the length in the radial direction R of the stator 3, which will be described later, is longer than the length in the axial direction A of the stator 3, as shown in Fig. 2 for example. The motor 1 is housed in, for example, a frame (not shown).

[0014] As shown in Fig. 1, the motor 1 includes a shaft 2, a stator 3, and a rotor 4. The shaft 2 is a so-called rotating shaft, and is formed, for example, from a metal member in a cylindrical shape extending along an axial direction A. The shaft 2 has an axis 2o and is provided so as to be rotatable about the axis 2o. The shaft 2 transmits power to the outside by rotating in a circumferential direction C.

[0015] The stator 3 is a part that generates a force for rotating the rotor 4 in the circumferential direction C. The stator 3 includes a core 31, an insulator (not shown), and a coil 32.

[0016] The core 31 is formed by stacking plate-shaped metal members such as silicon steel plates, electromagnetic steel plates, and soft magnetic steel plates in the axial direction A, and is magnetic. The core 31 according to this embodiment has a main body 31a and teeth 31b. The main body 31a is formed in an annular shape when viewed from the axial direction A. The teeth 31b are formed so as to protrude from the inner circumferential surface of the main body 31a toward the rotor 4 in the radial direction R. The stator 3 according to this embodiment includes, for example, 18 teeth 31b.

[0017] The insulator is made of, for example, insulating resin and is attached to the surface of the core 31. The coils 32 are formed by, for example, winding wire around the teeth 31b with the insulator interposed therebetween. The winding wire has a conductive core wire (not shown) and an insulating covering portion (not shown) that covers the periphery of the core wire. The stator 3 according to this embodiment has, for example, 18 coils 32.

[0018] The rotor 4 is provided so as to be rotatable about an axis 2o of the shaft 2, which is a rotation axis. In the motor 1 according to this embodiment, the shaft 2 and the rotor 4 are formed integrally.

[0019] The rotor 4 is disposed, for example, inside (on the shaft 2 side of) the stator 3 in the radial direction R. In other words, the motor 1 is an inner rotor type brushless motor in which the rotor 4 is located inside the stator 3 in the radial direction R.

[0020] 2, the rotor 4 includes a yoke 41 and a plurality of magnets 42. The yoke 41 is made of a magnetic material such as iron.

[0021] The magnets 42 are, for example, permanent magnets. The plurality of magnets 42 are, for example, arranged along the circumferential direction C. The plurality of magnets 42 include, for example, 20 first magnets 42 a, 20 second magnets 42 b, and 20 third magnets 42 c.

[0022] The first magnet 42 a is a so-called main magnet. The second magnet 42 b and the third magnet 42 c are so-called sub-magnets. In the yoke 41 according to this embodiment, the second magnet 42 b is disposed on one side of the first magnet 42 a in the circumferential direction C, and the third magnet 42 c is disposed on the other side of the first magnet 42 a in the circumferential direction C.

[0023] The yoke 41 functions as a path for magnetic flux between the first magnet 42a and the second magnet 42b, and also functions as a path for magnetic flux between the first magnet 42a and the third magnet 42c.

[0024] 3, the yoke 41 has a main body 411, a hole 412, and a frame 413. The main body 411 is formed to extend along the circumferential direction C. That is, the main body 411 is formed in a cylindrical shape. The yoke 41 also includes an outer circumferential surface 41f1 located on the stator side R1 in the radial direction R, and an inner circumferential surface 41f2 located on the opposite side R2 from the stator 3 in the radial direction R.

[0025] A plurality of holes 412 are formed in the main body 411. The holes 412 are arranged at equal intervals along the circumferential direction C. The holes 412 are formed to penetrate the main body 411 in the axial direction A. The holes 412 are spaced at equal distances from the axis 2o and are arranged at equal intervals along the circumferential direction C. The holes 412 are arranged closer to the inner circumferential surface 41f2 of the yoke 41 in the radial direction R than to the outer circumferential surface 41f1.

[0026] Next, the shape of the hole 412 will be described. As shown in FIG. 4 , for example, when viewed from the axial direction A, the hole 412 has three pairs of opposing inner surfaces 412f1, 412f2, and 412f3. More specifically, the hole 412 has a pair of first inner surfaces 412f1 opposing in the circumferential direction C, a pair of second inner surfaces 412f2 opposing in the circumferential direction C, and a pair of third inner surfaces 412f3 opposing in the radial direction R. In other words, when viewed from the axial direction A, the hole 412 is formed so that its entire circumference is surrounded by the inner surfaces 412f1, 412f2, and 412f3 of the wall portions that constitute the yoke 41. A first magnet 42a is disposed inside each of the holes 412.

[0027] The pair of first inner surfaces 412f1 are disposed in the hole 412 on the opposite side R2 from the stator 3 in the radial direction R (i.e., on the inner circumferential surface 41f2 side of the yoke 41). The pair of first inner surfaces 412f1 are disposed parallel to each other. Each of the pair of first inner surfaces 412f1 is also parallel to a center line 1CL, which will be described later.

[0028] The pair of second inner surfaces 412f2 are disposed on the stator side R1 (i.e., on the outer peripheral surface 41f1 side of the yoke 41) in the radial direction R of the hole 412. The pair of second inner surfaces 412f2 are disposed so as to incline toward the stator side R1 and away from each other. Each of the pair of second inner surfaces 412f2 is inclined with respect to a center line 1CL, which will be described later.

[0029] One third inner surface 412f32 of the pair of third inner surfaces 412f3 is arranged on the stator side R1 in the radial direction R in the hole 412. The other third inner surface 412f31 of the pair of third inner surfaces 412f3 is arranged on the opposite side R2 from the stator 3 in the radial direction R in the hole 412.

[0030] 5, the boundary 412B between the pair of first inner surfaces 412f1 and the pair of second inner surfaces 412f2 in the radial direction R is positioned so that its position in the radial direction R is substantially the same as the first end 42b1 of the second magnet 42b on the side R2 opposite to the stator 3. Similarly, the boundary 412B is positioned so that its position in the radial direction R is substantially the same as the first end 42c1 of the third magnet 42c on the side R2 opposite to the stator 3.

[0031] 3, a plurality of frames 413 are formed on the main body 411. The plurality of frames 413 are, for example, at a constant distance from the axis 2o and are arranged at constant intervals along the circumferential direction C.

[0032] The frame 413 is disposed so as to surround the hole 412 when viewed from the axial direction A. More specifically, as shown in FIG. 5 , two frames 413 are disposed on both sides of the hole 412 in the circumferential direction C so that a portion of the hole 412 on the stator side R1 faces a portion of the frame 413 on the opposite side R2 from the stator 3. In other words, when viewed from the axial direction A, the frame 413 is formed to have a pair of first inner surfaces 413f1 facing each other in the circumferential direction C and a second inner surface 413f2 connecting the pair of first inner surfaces 413f1 with respect to the wall portion constituting the yoke 41, as shown in FIG. 4 , and is formed so as to be surrounded on three sides in the radial direction R excluding the stator side R1 by the pair of first inner surfaces 413f1 and the second inner surface 413f2. The frame 413 described above is formed so as to penetrate the main body 411 in the axial direction A.

[0033] The first inner surface 413f1 is in contact with the side surface 42b3 of the second magnet 42b or the side surface 42c3 of the third magnet 42c. The second inner surface 413f2 is in contact with the first end portion 42b1 of the second magnet 42b or the first end portion 42c1 of the third magnet 42c.

[0034] Furthermore, the frame 413 has an opening 413o that connects the outside of the yoke 41 with the inside of the frame 413 in the radial direction R. In other words, the frame 413 is disposed so that the opening 413o is formed in the outer peripheral surface 41f1 of the yoke 41. In other words, the frame 413 is disposed on the stator side R1 in the radial direction R of the rotor 4.

[0035] Furthermore, the frame 413 has a pair of protrusions 414 that protrude close to each other inside the frame 413, at a portion where the opening 413o is formed. In other words, the protrusions 414 protrude from the first inner surface 413f1 toward the inside of the frame 413 along the circumferential direction C. They protrude from the main body 411 in the circumferential direction C. The second magnet 42b and the third magnet 42c are disposed inside the frame 413 (see FIG. 5 ). As described above, because the protrusions 414 protrude from the first inner surface 413f1 toward the inside of the frame 413 along the circumferential direction C, the protrusions 414 restrict the second magnet 42b and the third magnet 42c from moving toward the stator side R1 in the radial direction R. In other words, the protrusions 414 function as engaging portions that engage with the second magnet 42b and the third magnet 42c.

[0036] The first magnet 42a is formed, for example, in a rectangular parallelepiped shape. As shown in FIG. 5 , the first magnet 42a has a first end (end) 42a1 on the opposite side R2 from the stator 3 in the radial direction R, and a second end (end) 42a2 on the stator side R1. One of the first end 42a1 and the second end 42a2 is a north pole, and the other is a south pole. The first magnet 42a also has two side surfaces 42a3 that face each other in the circumferential direction C. The two side surfaces 42a3 are parallel to each other and to a center line 1CL (described later). The first magnet 42a is positioned so as to be closer to the inner circumferential surface 41f2 of the yoke 41 than to the outer circumferential surface 41f1 in the radial direction R.

[0037] The second magnet 42b is formed, for example, in a rectangular parallelepiped shape. The second magnet 42b has a first end (end) 42b1 on the opposite side R2 from the stator 3 in the radial direction R, and a second end (end) 42b2 on the stator side R1. One of the first end 42b1 and the second end 42b2 is a north pole, and the other is a south pole. The second magnet 42b also has two side surfaces 42b3 that face each other in the circumferential direction C. The two side surfaces 42b3 are parallel to each other and to a center line 1CL (described later). When viewed from the axial direction A, the area of ​​the second magnet 42b according to this embodiment is larger than the area of ​​the first magnet 42a. The second magnet 42b is positioned so that a portion of the second magnet 42b is exposed in the radial direction R from an opening 413o located on the stator side R1.

[0038] The third magnet 42c is formed, for example, in a rectangular parallelepiped shape. The third magnet 42c has a first end (end) 42c1 on the opposite side R2 from the stator 3 in the radial direction R, and a second end (end) 42c2 on the stator side R1. One of the first end 42c1 and the second end 42c2 is a north pole, and the other is a south pole. The third magnet 42c also has two side surfaces 42c3 that face each other in the circumferential direction C. The two side surfaces 42c3 are parallel to each other and to a center line 1CL (described later). When viewed from the axial direction A, the third magnet 42c according to this embodiment has a larger area than the first magnet 42a. The third magnet 42c is positioned so that a portion of the third magnet 42c is exposed in the radial direction R from an opening 413o located on the stator side R1.

[0039] There are 20 first magnets 42a, 20 second magnets 42b, and 20 third magnets 42c, so the rotor 4 according to this embodiment has 60 magnetic poles.

[0040] 1, the second magnet 42b and the third magnet 42c are arranged to be line-symmetrical with respect to a center line 1CL that passes through the center of the first magnet 42a in the circumferential direction C and the axial center 2o of the shaft 2. The second magnet 42b is formed, for example, in the same shape as the third magnet 42c. Furthermore, the length in the axial direction A of the first magnet 42a, the length in the axial direction A of the second magnet 42b, and the length in the axial direction A of the third magnet 42c are all the same. Furthermore, the first magnet 42a, the second magnet 42b, and the third magnet 42c are arranged inside the yoke 41.

[0041] 5, the length L1 of the first magnet 42a in the radial direction R is shorter than, for example, the length L20 of the second magnet 42b in the radial direction R. Also, the length L1 of the first magnet 42a in the radial direction R is shorter than, for example, the length L3 of the third magnet 42c in the radial direction R. Furthermore, the width W1 of the first magnet 42a perpendicular to the radial direction R is narrower than the width W2 of the second magnet 42b perpendicular to the radial direction R. Furthermore, the width W1 of the first magnet 42a perpendicular to the radial direction R is narrower than the width W30 of the third magnet 42c perpendicular to the radial direction R.

[0042] 4, the distance W4 between the pair of protrusions 414 in the circumferential direction C is narrower than the sum of the width W2 of the second magnet 42b and the width W30 of the third magnet 42c. Therefore, when the rotor 4 is rotated in the circumferential direction C, the pair of protrusions 414 can prevent the second magnet 42b and the third magnet 42c from coming off the yoke 41.

[0043] A first gap G1 is formed between the outer peripheral surface 41f1 of the yoke 41 shown in FIG. 6 and the inner peripheral surfaces 31bf of the teeth 31b. The width of the first gap G1 in the radial direction R is W11. A second gap G2 is formed between the second end 42b2 of the stator side R1 of the second magnet 42b and the inner peripheral surfaces 31bf of the teeth 31b. The width of the second gap G2 in the radial direction R is W21. A third gap G3 is formed between the second end 42c2 of the stator side R1 of the third magnet 42c and the inner peripheral surfaces 31bf of the teeth 31b. The width of the third gap G3 in the radial direction R is W31.

[0044] The second magnet 42b is disposed so that the width W11 of the first gap G1 and the width W21 of the second gap G2 are the same in the radial direction R. Furthermore, the third magnet 42c is disposed so that the width W11 of the first gap G1 and the width W31 of the third gap G3 are the same in the radial direction R. In other words, when the shaft 2 and the rotor 4 are rotated in the circumferential direction C relative to the stationary stator 3, a gap of a constant width is formed between the rotor 4 and the stator 3 in the radial direction R.

[0045] The direction of the magnetic flux of the first magnet 42 a is, for example, along the radial direction R. More specifically, the direction of the magnetic flux of the first magnet 42 a is along the stator side R1 in the radial direction R, or along the opposite side R2 from the stator 3 in the radial direction R.

[0046] The direction of the magnetic flux of the second magnet 42b is inclined, for example, with respect to the radial direction R. More specifically, the direction of the magnetic flux of the second magnet 42b is inclined so as to gradually approach the first magnet 42a in the circumferential direction C as it moves toward the side R2 opposite the stator 3, or is inclined so as to gradually move away from the first magnet 42a in the circumferential direction C as it moves toward the stator side R1.

[0047] The direction of the magnetic flux of the third magnet 42c is inclined, for example, with respect to the radial direction R. More specifically, the direction of the magnetic flux of the third magnet 42c is inclined so as to gradually approach the first magnet 42a in the circumferential direction C as it moves toward the side R2 opposite the stator 3, or is inclined so as to gradually move away from the first magnet 42a in the circumferential direction C as it moves toward the stator side R1.

[0048] In other words, the direction of the magnetic flux of the second magnet 42b and the direction of the magnetic flux of the third magnet 42c are inclined so that the distance between them in the circumferential direction C becomes closer as they move toward the opposite side R2 from the stator 3, or are inclined so that the distance between them in the circumferential direction C becomes farther as they move toward the stator side R1.

[0049] Furthermore, as described above, since the direction of the magnetic flux of the first magnet 42a, the direction of the magnetic flux of the second magnet 42b, and the direction of the magnetic flux of the third magnet 42c are different, the rotor 4 in this embodiment is a so-called Halbach array rotor 4 in which the first magnet 42a, the second magnet 42b, and the third magnet 42c are arranged so that the directions of the magnetic flux are different from each other.

[0050] In the radial direction R, the first end 42a1 of the first magnet 42a on the side R2 opposite the stator 3 protrudes relative to the first end 42b1 of the second magnet 42b on the side R2 opposite the stator 3 shown in Fig. 5. In other words, in the radial direction R, the first end 42a1 of the first magnet 42a on the side R2 opposite the stator 3 is located on the side R2 opposite the stator 3 relative to the first end 42b1 of the second magnet 42b on the side R2 opposite the stator 3. In other words, the first end 42a1 of the first magnet 42a on the side R2 opposite the stator 3 in the radial direction R is closer to the inner circumferential surface 41f2 of the yoke 41 than the first end 42b1 of the second magnet 42b on the side R2 opposite the stator 3 in the radial direction R.

[0051] In the radial direction R, the second end 42b2 of the second magnet 42b on the stator side R1 protrudes relative to the second end 42a2 of the first magnet 42a on the stator side R1. In other words, in the radial direction R, the second end 42a2 of the first magnet 42a on the stator side R1 is located on the opposite side R2 from the stator 3 relative to the second end 42b2 of the second magnet 42b on the stator side R1. In other words, the second end 42a2 of the first magnet 42a on the stator side R1 in the radial direction R is farther away from the outer circumferential surface 41f1 of the yoke 41 by a predetermined distance than the second end 42b2 of the second magnet 42b on the stator side R1 in the radial direction R.

[0052] In the radial direction R, the first end 42a1 of the first magnet 42a on the side R2 opposite the stator 3 protrudes relative to the first end 42c1 of the third magnet 42c on the side R2 opposite the stator 3. In other words, in the radial direction R, the first end 42a1 of the first magnet 42a on the side R2 opposite the stator 3 is located on the side R2 opposite the stator 3 relative to the first end 42c1 of the third magnet 42c. In other words, the first end 42a1 of the first magnet 42a on the side R2 opposite the stator 3 in the radial direction R is closer to the inner circumferential surface 41f2 of the yoke 41 than the first end 42c1 of the third magnet 42c on the side R2 opposite the stator 3 in the radial direction R.

[0053] In the radial direction R, the second end 42c2 of the third magnet 42c on the stator side R1 protrudes relative to the second end 42a2 of the first magnet 42a on the stator side R1. In other words, in the radial direction R, the second end 42a2 of the first magnet 42a on the stator side R1 is located on the opposite side R2 from the stator 3 relative to the second end 42c2 of the third magnet 42c on the stator side R1. In other words, the second end 42a2 of the first magnet 42a on the stator side R1 in the radial direction R is farther away from the outer circumferential surface 41f1 of the yoke 41 by a predetermined distance than the second end 42c2 of the third magnet 42c on the stator side R1 in the radial direction R.

[0054] The first end 42a1 of the first magnet 42a and the hole 412 on the side R2 opposite to the stator 3 in the radial direction R contacts the third inner surface 412f31 of the hole 412. In addition, the second end 42a2 of the first magnet 42a and the hole 412 on the stator side R1 in the radial direction R contacts the third inner surface 412f32 of the hole 412.

[0055] The first magnet 42a and the hole 412 are in contact with each other in the circumferential direction C between the both side surfaces 42a3 of the first magnet 42a and the first inner surface 412f1 of the hole 412 on the side R2 opposite the stator 3 in the radial direction R. Meanwhile, the first magnet 42a and the hole 412 are in contact with each other in the circumferential direction C between the both side surfaces 42a3 of the first magnet 42a and the second inner surface 412f2 of the hole 412 on the stator side R1 in the radial direction R.

[0056] Air exists in the gap 412s. Air is a non-magnetic material, and its magnetic permeability is lower than that of the magnetic material forming the yoke 41. In other words, the air existing in the gap 412s functions as a flux barrier that suppresses magnetic flux from the side surface 42b3 of the second magnet 42b to the side surface 42a3 of the first magnet 42a in the circumferential direction C, and from the side surface 42c3 of the third magnet 42c to the side surface 42a3 of the first magnet 42a. Alternatively, the air existing in the gap 412s functions as a flux barrier that suppresses magnetic flux from the side surface 42a3 of the first magnet 42a to the side surface 42b3 of the second magnet 42b in the circumferential direction C, and from the side surface 42a3 of the first magnet 42a to the side surface 42c3 of the third magnet 42c.

[0057] For this reason, in the portion where the gap 412s exists, the magnetic flux flowing in the circumferential direction C from the side surface of one magnet 42 to the side surface of the other magnet 42 is suppressed by the air, which is a non-magnetic material. As a result, in the portion where the gap 412s exists, the magnetic flux is suppressed by the non-magnetic material between both side surfaces 42a3 in the circumferential direction C of the first magnet 42a and both side surfaces 42b3 in the circumferential direction C of the second magnet 42b. Similarly, in the portion where the gap 412s exists, the magnetic flux is suppressed by the non-magnetic material between both side surfaces 42a3 in the circumferential direction C of the first magnet 42a and both side surfaces 42c3 in the circumferential direction C of the third magnet 42c.

[0058] On the other hand, in the circumferential direction C, at the portion where both side surfaces 42a3 of the first magnet 42a contact the first inner surface 412f1 of the hole 412, magnetic flux passes between both side surfaces 42a3 of the first magnet 42a and the first end 42c1 of the third magnet 42c.

[0059] The first magnet 42a is formed in a rectangular parallelepiped shape, and a pair of side surfaces 42a3 facing each other in the circumferential direction C are parallel to each other, and each of the side surfaces 42a3 is parallel to the center line 1CL. Meanwhile, in the hole 412, a pair of second inner surfaces 412f2 facing each other in the circumferential direction C are formed to be inclined so that they move away from each other toward the stator side R1 in the radial direction R. The second inner surfaces 412f2 of the hole 412 are inclined with respect to the center line 1CL. In other words, in the rotor 4 according to this embodiment, the side surfaces 42a3 of the first magnet 42a are inclined relative to the second inner surfaces 412f2 of the hole 412.

[0060] 5 , if the length in the radial direction R from the position of the second end 42a2 of the first magnet 42a on the opposite side R2 from the stator 3 to the position of the second end 42b2 of the second magnet 42b on the opposite side R2 from the stator 3 is L2, then in the rotor 4 according to this embodiment, L1 / 2 > L2. In other words, the amount by which the second end 42a2 of the first magnet 42a protrudes from the second end 42b2 of the second magnet 42b in the radial direction R (i.e., L2 is the offset amount) is less than half the length L1 of the first magnet 42a in the radial direction R.

[0061] Also, the surface area of ​​the side surface 42b3 of the second magnet 42b extending in the radial direction R is defined as S1. Furthermore, the surface area of ​​the surface extending in the circumferential direction C, which is the surface R1 of the yoke 41 of the rotor 4 on the stator side, is defined as S2. Furthermore, if the number of magnetic poles of the rotor 4 (the number of magnetic poles of the rotor 4 according to this embodiment is 60) is defined as P, then for the rotor 4 according to this embodiment, S1 > S2 / P.

[0062] Furthermore, when the surface area of ​​the surface of the first magnet 42a on the stator side R1, which extends in the circumferential direction C, is S3, the rotor 4 according to this embodiment satisfies S1 / 2>S3.

[0063] Furthermore, if the width of the first magnet 42a in the circumferential direction C is W1, the width of the second magnet 42b in the circumferential direction C is W2, and the width of the frame 413 in the circumferential direction C is W3, then the rotor 4 according to this embodiment satisfies W2≧W1>W3.

[0064] In the rotor 4 according to this embodiment, the first end 42b1 of the second magnet 42b on the side R2 opposite the stator 3 in the radial direction R is opposite the first end 42a1 of the first magnet 42a on the side R2 opposite the stator 3. Therefore, the rotor 4 according to this embodiment can reduce the density of the magnetic flux (magnetic flux indicated by arrows f9 and f10 in FIG. 6 ) flowing from the first end 42a1 of the first magnet 42a and the first end 42b1 of the second magnet 42b toward the side R2 opposite the stator 3 in the radial direction R, and can increase the density of the magnetic flux (magnetic flux indicated by arrows f2 and f4 in FIG. 6 ) flowing from one side to the other in the circumferential direction C at the first end 42a1 of the first magnet 42a and the first end 42b1 of the second magnet 42b. As a result, the motor 1 according to this embodiment can improve the output torque of the motor 1 by increasing the density of the magnetic flux (magnetic flux indicated by arrows f3 and f6 in FIG. 6) flowing from the second end 42a2 of the first magnet 42a and the second end 42b2 of the second magnet 42b toward the stator 3 in the radial direction R.

[0065] In the rotor 4 according to this embodiment, the first end 42c1 of the third magnet 42c is on the side R2 opposite the stator 3 in the radial direction R, while the first end 42a1 of the first magnet 42a on the side R2 opposite the stator 3 is on the side R2 opposite the stator 3. Therefore, the rotor 4 according to this embodiment can reduce the density of the magnetic flux (magnetic flux indicated by arrows f8 and f10 in FIG. 6 ) flowing from the first end 42a1 of the first magnet 42a and the first end 42c1 of the third magnet 42c toward the side R2 opposite the stator 3 in the radial direction R, and can increase the density of the magnetic flux (magnetic flux indicated by arrows f1 and f5 in FIG. 6 ) flowing from one side to the other in the circumferential direction C at the first end 42a1 of the first magnet 42a and the first end 42c1 of the third magnet 42c. As a result, the motor 1 according to this embodiment can improve the output torque of the motor 1 by increasing the density of the magnetic flux (magnetic flux indicated by arrows f3 and f7 in FIG. 6) flowing from the second end 42a2 of the first magnet 42a and the second end 42b2 of the third magnet 42c toward the stator 3 in the radial direction R.

[0066] In the rotor 4 of this embodiment, in the radial direction R, the second end 42b2 of the second magnet 42b on the stator side R1 is located on the opposite side R2 from the stator 3, while the second end 42a2 of the first magnet 42a on the stator side R1 is located on the opposite side R2 from the stator 3.

[0067] In the rotor 4 of this embodiment, in the radial direction R, the second end 42c2 of the third magnet 42c on the stator side R1 is located on the opposite side R2 from the stator 3, while the second end 42a2 of the first magnet 42a on the stator side R1 is located on the opposite side R2 from the stator 3.

[0068] In the rotor 4 according to this embodiment, the yoke 41 includes a hole 412 and a frame 413 surrounding the hole 412. The first magnet 42a is located inside the hole 412, and a gap 412s is present in the circumferential direction C between the second inner surface 412f2 of the hole 412 and the side surface 42a3 of the first magnet 42a. In addition, a non-magnetic material having a lower magnetic permeability than the magnetic material forming the yoke 41 is present in the gap 412s. Therefore, in the portion of the circumferential direction C where the gap 412s exists, the non-magnetic material suppresses magnetic flux from the side surface 42a3 of the first magnet 42a toward the side surface 42b3 of the second magnet 42b and the side surface 42c3 of the third magnet 42c. As a result, the magnetic flux density increases between the first end 42a1 of the first magnet 42a and the first end 42b1 of the second magnet 42b, and between the first end 42a1 of the first magnet 42a and the first end 42c1 of the third magnet 42c. Therefore, the motor 1 according to this embodiment can increase the magnetic flux density from the first magnet 42a to the stator 3.

[0069] In the rotor 4 according to this embodiment, the surface area of ​​the side surface 42b3 of the second magnet 42b extending in the radial direction R is defined as S1, and the surface area of ​​the surface extending in the circumferential direction C on the stator side R1 of the yoke 41 of the rotor 4 is defined as S2. Furthermore, if the number of magnetic poles of the rotor 4 (60 in the rotor 4 according to this embodiment) is defined as P, then in the rotor 4 according to this embodiment, S1 > S2 / P. Therefore, in order to make the surface area S1 of the side surface 42b3 of the second magnet 42b as large as possible, the size L20 of the second magnet 42b in the radial direction R can be made as long as possible.

[0070] In the rotor 4 according to this embodiment, if the width W1 of the first magnet 42a in the circumferential direction C is defined as W1, the width W2 of the second magnet 42b in the circumferential direction C is defined as W2, and the width W3 of the frame 413 in the circumferential direction C is defined as W3, then W2 ≥ W1 > W3 holds. Therefore, in the rotor 4 according to this embodiment, by narrowing the width W3 of the frame 413, it is possible to saturate the magnetic flux between the side surface 42a3 of the first magnet 42a and the side surface 42b3 of the second magnet 42b in the circumferential direction C. As a result, in the motor 1 according to this embodiment, it is possible to increase the magnetic flux density from the first magnet 42a and the second magnet 42b toward the stator 3 by increasing the magnetic flux density between the first end 42a1 of the first magnet 42a and the first end 42b1 of the second magnet 42b. Furthermore, by narrowing the width W3 of the frame 413 as much as possible, it is possible to reduce the size of the yoke 41 in the radial direction R.

[0071] In the rotor 4 according to this embodiment, if the width W1 of the first magnet 42a in the circumferential direction C, the width W30 of the third magnet 42c in the circumferential direction C, and the width W3 of the frame 413 in the circumferential direction C are each defined as W30 ≥ W1 > W3. Therefore, by narrowing the width W3 of the frame 413, the rotor 4 according to this embodiment can saturate the magnetic flux between the side surface 42a3 of the first magnet 42a and the side surface 42c3 of the third magnet 42c in the circumferential direction C. As a result, the motor 1 according to this embodiment can increase the magnetic flux density between the first end 42a1 of the first magnet 42a and the first end 42c1 of the third magnet 42c, thereby increasing the magnetic flux density from the first magnet 42a and the third magnet 42c toward the stator 3. Furthermore, by narrowing the width W3 of the frame 413 as much as possible, the size of the yoke 41 in the radial direction R can be reduced.

[0072] The stator 3 according to the embodiment described above has been described as including 18 teeth 31 b. However, the number of teeth 31 b of the stator 3 according to the embodiment is not limited to this and can be set to any number.

[0073] Furthermore, the stator 3 according to the above-described embodiment has been described as including 18 coils 32. However, the number of coils 32 of the stator 3 according to the present embodiment is not limited to this and can be set to any number.

[0074] Furthermore, the rotor 4 according to the above embodiment has been described as including 20 first magnets 42a, 20 second magnets 42b, and 20 third magnets 42c. However, the numbers of the magnets 42a, 42b, and 42c are not limited to this and can be set to any number.

[0075] In the rotor 4 according to the above embodiment, the side surface 42a3 of the first magnet 42a is parallel to the center line 1CL, while the second inner surface 412f2 of the hole 412 is inclined with respect to the center line 1CL, thereby causing both side surfaces 42a3 of the first magnet 42a to be inclined with respect to the second inner surface 412f2 of the hole 412. However, the rotor 4 according to the present embodiment is not limited to this. For example, the side surface 42a3 of the first magnet 42a may be inclined with respect to the center line 1CL, while the second inner surface 412f2 of the hole 412 may be parallel to the center line 1CL, thereby causing both side surfaces 42a3 of the first magnet 42a to be inclined relative to the second inner surface 412f2 of the hole 412. Furthermore, the side surface 42a3 of the first magnet 42a may be inclined relative to the center line 1CL, and the second inner surface 412f2 of the hole 412 may be inclined relative to the center line 1CL, so that both side surfaces 42a3 of the first magnet 42a may be inclined relative to the second inner surface 412f2 of the hole 412.

[0076] Furthermore, in the above-described embodiment, the rotor 4 is provided with the rectangular parallelepiped first magnet 42a, the rotor 4 is provided with the rectangular parallelepiped second magnet 42b, and the rotor 4 is provided with the rectangular parallelepiped third magnet 42c. However, the shapes of the magnets 42a, 42b, and 42c according to this embodiment are not limited to these, and they may be formed into other shapes.

[0077] In the above-described embodiment, the hole 412 is formed to have three pairs of opposing inner surfaces 412f1, 412f3, 412f4 when viewed from the axial direction A. However, the shape of the hole 412 according to this embodiment is not limited to this, and the hole 412 may be formed in another shape.

[0078] [First Modification of First Embodiment] Next, a motor 1A according to a first modification of the first embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a plan view of the motor 1A according to the first modification of the first embodiment. Fig. 8 is a perspective view of a rotor 4A included in the motor 1A shown in Fig. 7.

[0079] Similar to the frame 413 of the yoke 41 of the rotor 4 of the first embodiment, the frame 413 of the yoke 41 of the rotor 4 according to this modification has a second inner surface 413f2 that is perpendicular to the radial direction R, as shown in FIG. 8 . The rotor 4A according to this modification has recesses 416 formed in the frame 413. Two recesses 416 are formed per frame 413, and two recesses 416 are formed on the second inner surface 413f2 that constitutes the frame 413. More specifically, the recesses 416 are formed along the first inner surface 413f1 and extend in the radial direction R.

[0080] Each of the recesses 416 has a first inner surface 416a located on the side R2 of the frame 413 opposite the stator 3, and a pair of second inner surfaces 416b located on both sides of the first inner surface 416a in the circumferential direction C and facing each other in the circumferential direction C. As shown in FIG. 7 , such recesses 416 are arranged on both sides in the circumferential direction C of the side surface 42a3 of the first magnet 42a. More specifically, the recesses 416 are arranged on both sides in the circumferential direction C of the side surface 42a3 of the first magnet 42a with which the second inner surface 412f2 of the hole 412 comes into contact. Furthermore, a part of the frame 413 is located between the recess 416 and the first magnet 42a in the circumferential direction C.

[0081] The second magnet 42b and the third magnet 42c are disposed inside the frame 413. The length of the recess 416 in the circumferential direction C is shorter than half the length of the frame 413 in the circumferential direction C. Therefore, a part of the first end 42b1 of the second magnet 42b and a part of the first end 42c1 of the third magnet 42c contact the second inner surface 413f2 of the frame 413.

[0082] In other words, the yoke 41 according to this modification has a second inner surface 413f2 that faces the surface of the first end 42b1 of the second magnet 42b on the side R2 opposite the stator 3 in the radial direction R. A recess 416 is provided on the second inner surface 413f2 that faces the surface of the first end 42b1 of the second magnet 42b on the side R2 opposite the stator 3. A gap 416s is provided between the surface of the first end 42b1 of the second magnet 42b on the side R2 opposite the stator 3 and the recess 416. Note that while the above description has been given for the second magnet 42b, the same applies to the third magnet 42c.

[0083] Air exists in the gap 416s. Air is a non-magnetic material, and its magnetic permeability is lower than that of the magnetic material forming the yoke 41. In other words, the air existing in the gap 416s functions as a flux barrier that suppresses magnetic flux from the side surface 42b3 of the second magnet 42b to the side surface 42a3 of the first magnet 42a in the circumferential direction C, and from the side surface 42c3 of the third magnet 42c to the side surface 42a3 of the first magnet 42a. Alternatively, the air existing in the gap 416s functions as a flux barrier that suppresses magnetic flux from the side surface 42a3 of the first magnet 42a to the side surface 42b3 of the second magnet 42b in the circumferential direction C, and from the side surface 42a3 of the first magnet 42a to the side surface 42c3 of the third magnet 42c in the circumferential direction C.

[0084] In addition, in the rotor 4A according to this modification, either a gap 412s or a gap 416s is disposed on the side in the circumferential direction C of the side surface 42a3 of the first magnet 42a.

[0085] In the rotor 4A according to this modification, a recess 416 is provided in the yoke 41, and a gap 416s is present between the recess 416 and the surface of the first end 42b1 of the second magnet 42b on the side R2 opposite the stator 3. Furthermore, a non-magnetic material with a lower magnetic permeability than the magnetic material forming the yoke 41 is present in the gap 416s. Therefore, in the portion of the gap 416s in the circumferential direction C, the non-magnetic material suppresses magnetic flux from the side surface 42a3 of the first magnet 42a to the side surface 42b3 of the second magnet 42b and the side surface 42c3 of the third magnet 42c. As a result, the magnetic flux density increases between the first end 42a1 of the first magnet 42a and the first end 42b1 of the second magnet 42b, and between the first end 42a1 of the first magnet 42a and the first end 42c1 of the third magnet 42c. Therefore, the motor 1A according to this modification can increase the magnetic flux density from the first magnet 42a to the stator 3.

[0086] In the rotor 4A according to this modification, either a gap 412s or a gap 416s is disposed on the side of the side surface 42a3 of the first magnet 42a in the circumferential direction C. Therefore, the rotor 4A according to this modification can reduce the magnetic flux density between the side surface 42a3 of the first magnet 42a and the side surface 412b3 of the second magnet 42b, and between the side surface 42a3 of the first magnet 42a and the side surface 412c3 of the third magnet 42b. As a result, the motor 1A according to this modification can increase the magnetic flux density from the second end 42a2 of the first magnet 42a, the second end 42b2 of the second magnet 42b, and the second end 42c2 of the third magnet 42c toward the stator 3, thereby improving the output torque of the motor 1A.

[0087] Second Embodiment Next, a motor 1B according to a second embodiment will be described with reference to Fig. 9. Fig. 9 is a plan view showing a portion of the motor 1B according to the second embodiment. Note that in the configuration of the motor 1B according to the second embodiment, the same components as those of the motor 1 according to the first embodiment are denoted by the same reference numerals and will not be described again.

[0088] In the motor 1B according to the second embodiment, when viewed from the axial direction A, with the rotor 4 as the reference, the stator 3B is located inside the rotor 4 in the radial direction R, and a shaft (not shown) is located inside the rotor 4 in the radial direction R. In other words, the motor 1B according to the second embodiment is an outer rotor type brushless motor.

[0089] In the motor 1B according to this embodiment, the inner side in the radial direction R is called the stator side R1, and the outer side in the radial direction R is called the side opposite the stator 3B R2. In Fig. 9, the stator side in the radial direction R is indicated by R1, and the side opposite the stator 3B in the radial direction R is indicated by R2. In addition, in the motor 1B according to this embodiment, the shaft (not shown) and the rotor 4B are formed as separate bodies.

[0090] In the motor 1B of this embodiment, the hole 412, the frame 413, the first magnet 42a, the second magnet 42b, and the third magnet 42c are arranged with the outside and inside of the radial direction R reversed relative to their arrangement in the motor 1 of the first embodiment, with the center line 2CL in the radial direction R of the rotor 4B as a reference.

[0091] More specifically, the hole 412 is disposed so as to be closer to the outer peripheral surface 41f1 of the yoke 41 in the radial direction R than to the inner peripheral surface 41f2.

[0092] The frame 413 is disposed so that the opening 413o is formed in the inner peripheral surface 41f2. That is, the frame 413 is disposed on the stator side R1 in the radial direction R of the yoke 41.

[0093] Furthermore, the first magnet 42a is disposed so as to be closer to the outer peripheral surface 41f1 than to the inner peripheral surface 41f2 of the yoke 41 in the radial direction R. The first magnet 42a has a first end 42a1 disposed on the side R2 opposite to the stator 3B, and a second end 42a2 disposed on the stator side R1.

[0094] The second magnet 42b is disposed so that a portion thereof is exposed from an opening 413o located on the stator side R1 in the radial direction R. Furthermore, the second magnet 42b has a first end 42b1 disposed on the opposite side R2 from the stator 3B, and a second end 42b2 disposed on the stator side R1.

[0095] The third magnet 42c is disposed so that a portion thereof is exposed from an opening 413o located on the stator side R1 in the radial direction R. Furthermore, the third magnet 42c has a first end 42c1 disposed on the opposite side R2 from the stator 3B, and a second end 42c2 disposed on the stator side R1.

[0096] By arranging the hole 412, the frame 413, the first magnet 42a, the second magnet 42b and the third magnet 42c as described above, the motor 1B of the second embodiment can achieve the same effects and advantages as those achieved by the motor 1 of the first embodiment.

[0097] The above has been a description of the motor 1 according to the present invention based on an embodiment and modifications thereof, but it goes without saying that the present invention is not limited to the embodiments and various modifications are possible without departing from the spirit of the present invention. The present invention also includes configurations in which the components of the above-described embodiments or modifications are appropriately combined. Such modifications without departing from the spirit of the present invention are also included within the technical scope of the present invention, and this will be clear to those skilled in the art from the claims.

[0098] DESCRIPTION OF SYMBOLS 1, 1A, 1B Motor, 2 Shaft, 3, 3B Stator, 4, 4A, 4B Rotor, 41 Yoke, 412 Hole, 412f2 Second inner surface (inner surface), 412s Gap, 413 Frame, 413f2 Second inner surface (inner surface), 416 Recess, 42a First magnet, 42a1 First end (end), 42a2 Second end (end), 42a3 Side, 42b Second magnet, 42b1 First end (end), 42b2 Second end (end), 42c3 Side, 42c Third magnet, A Axial direction, C Circumferential direction, R Radial direction, R1 Stator side in the radial direction, R2 Opposite side to stators 3, 3B in the radial direction

Claims

1. A motor comprising a shaft, a rotor, and a stator, wherein the rotor has a yoke and first and second magnets arranged in a circumferential direction, the first and second magnets are located inside the yoke, and the end of the first magnet opposite the stator is located opposite the end of the second magnet opposite the stator in the radial direction.

2. The motor according to claim 1, further comprising a third magnet inside the yoke, the first magnet and the third magnet being disposed adjacent to each other in the circumferential direction, and the end of the first magnet on the stator side being located on the opposite side to the stator in the radial direction relative to the end of the second magnet on the stator side.

3. The motor according to claim 1 or 2, wherein the yoke comprises a hole and a frame surrounding the hole, the first magnet is located inside the hole, and there is a gap between the inner surface of the hole and the side surface of the first magnet in the circumferential direction.

4. The motor according to claim 3, wherein the side surface of the first magnet is inclined relative to the inner surface of the hole.

5. The motor according to claim 1 or 2, wherein the first magnet has an end portion on the stator side and an end portion opposite the stator in the radial direction, and the second magnet has an end portion on the stator side and an end portion opposite the stator in the radial direction, and where L1 is the size of the first magnet in the radial direction and L2 is the length from the position of the end portion of the first magnet opposite the stator to the position of the end portion of the second magnet opposite the stator in the radial direction, L1 / 2 > L2.

6. The motor according to claim 1 or 2, wherein, when the surface area of ​​the radially extending side surface of the second magnet is S1, the surface area of ​​the circumferentially extending surface on the stator side of the rotor is S2, and the number of magnetic poles of the rotor is P, then S1 > S2 / P.

7. The motor according to claim 1 or 2, wherein, when the surface area of ​​the circumferentially extending surface of the first magnet facing the stator is S3, the relationship S1 / 2>S3 holds.

8. The motor according to claim 1 or 2, wherein the yoke comprises a hole and a frame surrounding the hole, the first magnet is located inside the hole, and when the width of the first magnet in the circumferential direction is W1, the width of the second magnet in the circumferential direction is W2, and the width of the frame in the circumferential direction is W3, W2 ≧ W1 > W3 holds.

9. The motor according to claim 1 or 2, wherein the yoke has a surface facing the surface of the second magnet opposite the stator in the radial direction, a recess is provided on the surface facing the surface of the second magnet opposite the stator, and there is a gap between the surface of the second magnet opposite the stator and the recess.

10. The motor according to claim 9, wherein the surface of the second magnet opposite to the stator is in contact with a portion of the surface of the second magnet facing the surface of the second magnet opposite to the stator.

11. The motor according to claim 9, wherein the yoke comprises a hole and a frame surrounding the hole, and a part of the frame is located between the recess and the first magnet in the circumferential direction.

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