Brushless motor

Abstract

Brushless motor (20) with: one rotor (22, 250); and a stator (32) arranged on an outer circumference of the rotor (22, 250), a press-fit component (144b, 146b, 256, 264, 756, 856) fixed on the shaft (24, 752, 852), wherein the rotor (22, 250) comprises: a shaft (24, 252, 752, 852); a yoke (62, 72, 82, 92, 114, 124, 141, 266) fixed on the shaft (24, 252, 752, 852); a permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260), which is arranged on an outer circumference of the yoke (62, 72, 82, 92, 114, 124, 141, 266); a first resin area (68a, 103a, 254a) which is located at one end of the yoke (62, 72, 82, 92, 114, 124, 141, 266) and of the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260) is formed and configured in a shaft axis direction to fix the yoke (62, 72,82, 92, 114, 124, 141, 266) and of the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260); and a second resin area (68b, 103b, 254b) formed and configured at other ends of the yoke (62, 72, 82, 92, 114, 124, 141, 266) and the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260) in the shaft axis direction to fix the yoke (62, 72, 82, 92, 114, 124, 141, 266) and the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260), wherein a transmission hole (66a, 74, 270) connecting one end and another end in the direction of the shaft axis extends through the yoke (62, 72, 82, 92, 114, 124, 141, 266) and / or between the shaft (24, 252, 752, 852) and the yoke (62, 72,82, 92, 114, 124, 141, 266) is formed, a third resin area (68c, 103c, 254c) is formed in the transmission hole (66a, 74, 270), the third resin area (68c, 103c, 254c) is configured to connect the first resin area (68a, 103a, 254a) and the second resin area (68b, 103b, 254b), the first resin area (68a, 103a, 254a), the second resin area (68b, 103b, 254b) and the third resin area (68c, 103c, 254c) are formed as integrated components, the rotor (22, 250) furthermore includes a magnet holder (100, 102, 110, 118, 120, 142, 154, 160, 258, 262, 358, 458, 558, 658, 758, 768, 858) which is arranged on at least one end of the permanent magnet (64a, 64b, 64c, 64d, 116, 126, 132, 140, 260) in the direction of the shaft axis, the magnet holder (100, 102, 110, 118, 120, 142, 154, 160, 258, 262, 358, 458, 558, 658, 758, 768, 858) is configured to regulate the permanent magnet (64a, 64b, 64c, 64d, 116, 126, 132, 140,260) with respect to a movement in the shaft axis direction and a circumferential direction of the permanent magnet (64a, 64b, 64c, 64d, 116, 126, 132, 140, 260), the press-fit component (144b, 146b, 256, 264, 756, 856) is configured to cause the yoke (141, 266) to contact the magnet holder (142, 154, 160, 258, 262, 358, 458, 558, 658, 758, 768, 858) in the shaft axis direction, and the magnet holder (142, 154, 160, 258, 262, 358, 458, 558, 658, 758, 768, 858) is arranged between the press component (144b, 146b, 256, 264, 756, 856) and the permanent magnet (140, 260).

Description

In this specification, a technique related to a brushless motor is disclosed.Japanese Utility Model JP H06-48 382 U discloses a brushless motor. In this brushless motor, a rotor includes a shaft, a back yoke, or hereinafter, also simply referred to as a yoke, disposed on an outer periphery of the shaft, and a permanent magnet disposed on an outer periphery of the yoke.In the brushless motor disclosed in Japanese Utility Model JP H06-48 382 U, a resin portion is formed at both ends in a shaft axis direction of the permanent magnet and the yoke. Moreover, a resin portion is also formed on the entire inner circumferential surface of the yoke. The permanent magnet and the yoke are integrated by the resin portion. A bearing is formed in the resin portion formed on the inner circumferential surface of the yoke, and the shaft is engaged with the bearing. Due to this fact, the shaft, the yoke and the permanent magnet are integrated.In the above brushless motor, since the resin portion is formed on the entire inner circumferential surface of the yoke, the bearing engaged with the shaft needs to be formed in the resin portion. Consequently, a centrifugal force generated when the rotor rotates acts on the bearing formed in the resin portion. Consequently, the bearing formed in the resin portion needs to have a relatively high mechanical strength, and the size of the rotor increases.DE 89 00 963 U1 relates to a rotor for an electric machine, wherein a rotor laminated core together with permanent magnets is connected to a shaft in a positive-locking and rotationally fixed and axially non-displaceable manner by means of a rotor cage.JP H08-322 173 A relates to a rotor for a motor having a core, a permanent magnet and a metal tube, wherein two side plates cover the opposite end faces of the permanent magnet in the axial direction.This description aims to provide a technique for easily integrating a shaft, a yoke, and a permanent magnet while preventing an increase in size of a rotor and securing a force to be able to hold the yoke by the shaft.A brushless motor disclosed herein may include a rotor and a stator. The stator may be disposed on an outer periphery of the rotor. The rotor may include a shaft, a back yoke, or hereinafter, also simply referred to as a yoke fixed on the shaft, a permanent magnet disposed on an outer periphery of the yoke, a first resin portion, and a second resin portion. The first resin portion may be formed at one ends of the yoke and the permanent magnet in a shaft axis direction. The first resin portion may be configured to fix the yoke and the permanent magnet. The second resin portion may be formed at other ends of the yoke and the permanent magnet in the shaft axis direction. The second resin portion may be configured to fix the yoke and the permanent magnet. A transmission hole connecting one end side and another end side in the shaft axis direction may be formed through the yoke, between the shaft and the yoke, or in a combination thereof. "In a combination thereof" as mentioned above denotes a case where the transmission hole is formed through the yoke, and another transmission hole is formed between the shaft and the yoke. A third resin region may be formed inside the transmission hole. The third resin portion may be configured to communicate with the first resin portion and the second resin portion. The first resin portion, the second resin portion, and the third resin portion may be integrally formed.In this brushless motor, since the shaft is fixed to the yoke, the resin portion does not require a holding force (i.e., a force that allows the yoke to be held by the shaft) against the centrifugal force. Consequently, a mechanical strength necessary for the resin portion can be reduced, and an increase in the size of the rotor can be suppressed. Further, the transmission hole is formed in the yoke and / or between the shaft and the yoke. Consequently, the third resin portion formed in the transmission hole may be integrally formed with the first and second resin portions for fixing the yoke and the permanent magnet. Due to this fact, the shaft, the yoke, and the permanent magnet can be easily integrated. Consequently, the rotor can be prevented from becoming larger while the permanent magnet is appropriately supported.The brushless motor disclosed herein may further include a fourth resin portion configured to cover an outer circumferential surface of the permanent magnet. The first resin portion, the second resin portion, the third resin portion, and the fourth resin portion may be integrally formed. According to this configuration, the yoke and the permanent magnet can be reliably integrated.In the brushless motor disclosed herein, the permanent magnet may be configured to be divided into a plurality of regions in a circumferential direction of the permanent magnet. The plurality of regions of the permanent magnet may be alternately magnetized in different directions. In a cross section perpendicular to the shaft axis, at least a part of the transmission hole may be positioned on a line connecting a center of the plurality of regions in the circumferential direction and the shaft axis. According to this configuration, magnetic flux flowing from the respective divided regions of the permanent magnet into an adjacent region through the yoke is unlikely to be divided by the transmission hole, and an increase in magnetic resistance can be prevented.In the brushless motor disclosed herein, the yoke may include a through hole configured to pass through a center of the yoke in the shaft axis direction. The shaft may be press fit into the through hole of the yoke. According to this configuration, the shaft can be fixed to the yoke with a simple method.In the brushless motor disclosed herein, the yoke may include a through hole configured to pass through a center of the yoke in the shaft axis direction. In a cross section perpendicular to the shaft axis, an outer shape of the shaft may be a circular shape, and the through hole of the yoke may have a polygonal shape. The transmission hole may be formed between an outer circumferential surface of the shaft and the through hole of the yoke. According to this configuration, by forming the through hole of the yoke in a polygonal shape, the transmission hole can be easily formed.In the brushless motor disclosed herein, the permanent magnet may include a plurality of sub-permanent magnets each having a cross section perpendicular to the shaft axis in an arc shape. A circumferential position regulating portion may be formed in the yoke.The circumferential position regulating portion may be configured to regulate a position of the sub-permanent magnets at least at a point of an entire length of the permanent magnet in the shaft axis direction. According to this configuration, the divisional permanent magnets can be positioned at appropriate positions.In the brushless motor disclosed herein, the rotor may further include a magnet holder disposed on at least one end of the permanent magnet in the shaft axis direction. The magnet holder may be configured to regulate a movement of the permanent magnet in the shaft axis direction and a circumferential direction of the permanent magnet. According to this configuration, the permanent magnet can be positioned at an appropriate position.The brushless motor disclosed herein may further include a pressing member fixed to the shaft. The pressing member may be configured to cause the yoke to contact the magnet holder in the shaft axis direction. When the resin portion is integrally formed, a resin can be prevented from leaking to an outer circumferential surface of the permanent magnet by the pressing member. In this case, an outer diameter of the pressing member may be larger than an outer diameter of the permanent magnet. According to this configuration, since deburring of a resin can be performed on the outer circumferential surface of the pressing member and the resin is prevented from leaking to the outer circumferential surface of the permanent magnet via the outer circumferential surface of the pressing member, the pressing member can have a function of adjusting a weight balance of the rotor.In the brushless motor disclosed herein, the magnet holder may include a base portion and a plurality of peripheral wall portions. The base portion may be configured to be opposed to an end surface of the permanent magnet. Each of the plurality of circumferential wall portions may be configured to contact a contact part of an outer circumferential surface of the permanent magnet located at the one end of the permanent magnet, and extends along a circumferential direction of the permanent magnet. The base portion may include a plurality of outer peripheral parts, an inner peripheral part, and a beam part. The plurality of outer peripheral parts may be configured to communicate with the plurality of peripheral wall portions. The inner peripheral part may be configured to be closer to the shaft than the plurality of outer peripheral parts, and surround the shaft. The beam part may be configured to connect the plurality of outer peripheral parts and the inner peripheral part. The beam part may deform such that the outer circumferential parts are spaced apart from the inner circumferential part.In this brushless motor, the peripheral wall portions of the magnet holder contact the outer peripheral surface of the permanent magnet. As a result, the permanent magnet can be prevented from being separated from the yoke. The permanent magnet can be appropriately supported by the magnet holder. In the magnet holder, the outer peripheral parts are separated from the inner peripheral part by deformation of the beam part. As a result, an area surrounded by the plurality of circumferential wall portions becomes larger. With this structure, when the magnet holder is engaged with the permanent magnets, the peripheral wall portions can be prevented from being inclined toward the outside of the rotor. Consequently, it is not necessary to increase the gap between the permanent magnets and the stator by considering the inclination of the circumferential wall portions. According to this configuration, the permanent magnet can be appropriately supported and the motor efficiency does not decrease.In the brushless motor disclosed herein, in a direction perpendicular to the shaft axis, the contact parts of the outer circumferential surface of the permanent magnet may be formed closer to the shaft than other parts of the outer circumferential surface of the permanent magnet.According to this configuration, the amount of protrusion of the circumferential wall portion protruding from the outer circumferential surface of the permanent magnet toward the outer side of the rotor can be reduced. As a result, it is not necessary to provide a large gap between the permanent magnet and the stator by considering the portion of the circumferential wall portion protruding from the outer circumferential surface of the permanent magnet.In the brushless motor disclosed herein, each of the plurality of circumferential wall portions may be connected to the corresponding outer circumferential part at a connection part extending along the outer circumferential surface of the permanent magnet. In a plane perpendicular to the shaft axis, an angle between a line connecting one end of the connection part and a shaft center and a line connecting the other end of the connection part and the shaft center may be equal to or greater than 40 degrees.According to this configuration, it is possible to appropriately prevent the permanent magnet from being displaced toward the outer side of the rotor according to rotation of the rotor. As a result, it is not necessary to provide a large gap between the rotor and the stator by considering the displacement of the permanent magnet during the rotation of the rotor.Each of the plurality of outer circumferential parts may be connected to the inner circumferential part by two or more beam parts.According to this structure, the magnet holder can stably hold the permanent magnet as compared with a structure in which a beam portion is formed on an outer peripheral portion.The rotor may further include a pressing member configured to contact a surface of the base portion on an opposite side to the permanent magnet, and press the base portion from the opposite side to the permanent magnet toward the permanent magnet.According to this configuration, the base portion of the magnet holder can be prevented from being deformed in the shaft axis direction. As a result, the magnet holder can stably support the permanent magnet.In the direction perpendicular to the shaft axis, an outer diameter of the pressing member may be larger than an outer diameter of the permanent magnet and an outer diameter of the magnet holder.According to this configuration, the weight balance for stabilizing the rotation of the rotor by the pressing member can be adjusted.The rotor may further include a fifth resin portion configured to regulate deformation of the beam part.According to this configuration, deformation of the beam part during rotation of the rotor can be suppressed. As a result, the magnet holder can stably support the permanent magnet.The base region may include, in each of the plurality of outer peripheral parts, a contact hole configured to pass through the base region in the shaft axis direction at a location circumferentially outside the beam part connected to the outer peripheral part. The fifth resin region may be disposed in the contact hole. Each of the plurality of outer peripheral parts may include a contact region configured to contact the fifth resin region disposed within the contact hole from an inner peripheral side.According to this configuration, since the contact portion makes contact with the inner periphery of the fifth resin member, the outer peripheral part is prevented from being moved to the outside. As a result, deformation of the beam part can be suppressed appropriately during rotation of the rotor.FIG. 1 is a longitudinal cross-sectional view of a fuel pump according to an embodiment. FIG. 2 is a longitudinal cross-sectional view of a rotor. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2, FIG. 4 is a cross-sectional view (corresponding to the cross-section shown in FIG. 3 ) according to a modification of a rotor shown in FIG. 2. FIG. 5 is a longitudinal cross-sectional view of a rotor according to another modification. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5, FIG. 7 is a cross-sectional view (corresponding to the cross-section shown in FIG. 6 ) according to a modification of the rotor shown in FIG. 5. FIG. 8 is a cross-sectional view (corresponding to the cross-section shown in FIG. 6 ) according to another modification of the rotor shown in FIG. 5. FIG. 9 is a cross-sectional view (corresponding to the cross-section shown in FIG. 6 ) according to another modification of the rotor shown in FIG. 5. FIG. 10 is a longitudinal cross-sectional view of a rotor according to a second embodiment. FIG. 11 is a longitudinal cross-sectional view of a rotor according to a modification of the second embodiment. FIG. 12 is a longitudinal cross-sectional view of a rotor according to a third embodiment. FIG. 13 is a cross-sectional view taken along the line XIII-XIII in FIG. 12, FIG. 14 is a cross-sectional view taken along the line XIV-XIV in FIG. 12, FIG. 15 is a cross-sectional view (corresponding to the cross-section shown in FIG. 12 ) of a rotor according to a modification of the third embodiment. FIG. 16 is a longitudinal cross-sectional view of a rotor according to a fourth embodiment. FIG. 17 is a cross-sectional view taken along the line XVII-XVII in FIG. 16, FIG. 18 is a cross-sectional view taken along the line XVIII-XVIII in FIG. 16, FIG. 19 is a cross-sectional view (corresponding to the cross-section shown in FIG. 18 ) of a rotor according to a modification of the fourth embodiment. FIG. 20 is a front view of a rotor according to a fifth embodiment. FIG. 21 is a longitudinal cross-sectional view of the rotor shown in FIG. 20. FIG. 22 is a cross-sectional view taken along the line XXII-XXII in FIG. 21 (the resin portion is not shown). FIG. 23 is a cross-sectional view taken along the line XXIII-XXIII in FIG. 21, FIG. 24 is a cross-sectional view taken along the line XXIV-XXIV in FIG. 21 (a back yoke is not shown). FIG. 25 is a plan view (corresponding to FIG. 24 ) of a restriction plate according to a modification of the fifth embodiment. FIG. 26 is a front view of a rotor according to a modification of the fifth embodiment. FIG. 27 is a longitudinal cross-sectional view of the rotor shown in FIG. 26. FIG. 28 is a cross-sectional view taken along the line XXVIII-XXVIII in FIG. 27, FIG. 29 is a longitudinal cross-sectional view of a fuel pump according to a sixth embodiment. FIG. 30 is an exploded perspective view of a rotor. FIG. 31 is a plan view of a magnet holder. FIG. 32 is a plan view of a pressing member. FIG. 33 is a plan view of the rotor. FIG. 34 is a cross-sectional view taken along the line of intersection XXXIV-XXXIV in FIG. 33, FIG. 35 is a diagram showing a relationship between an angle θ of a connection part and an amount of displacement of a circumferential wall portion. FIG. 36 is a plan view of a magnet holder according to a modification. FIG. 37 is a plan view of a magnet holder according to a modification. FIG. 38 is a plan view of a magnet holder according to a modification. FIG. 39 is a plan view of a magnet holder according to a modification. FIG. 40 is a cross-sectional view taken along the line XXXIV-XXXIV according to a modification. FIG. 41 is a longitudinal cross-sectional view of a fuel pump according to a modification. FIG. 42 is a plan view of a magnet holder according to a seventh embodiment. FIG. 43 is a plan view of a pressing member according to the seventh embodiment. FIG. 44 is a plan view of a magnet holder according to an eighth embodiment. FIG. 45 is a plan view of a pressing member according to the eighth embodiment.(First Embodiment)A brushless motor according to a first embodiment will be described below. The brushless motor according to this embodiment is used in a fuel pump 10 for cars. The fuel pump 10 is disposed in a fuel tank to supply fuel, which is located in the fuel tank, to an internal combustion engine of a car. First, the structure of the fuel pump 10 will be described.As shown in FIG. 1, the fuel pump 10 includes a motor portion (i.e., a brushless motor) 20 and a pump portion 40, and the motor portion 20 and the pump portion 40 are accommodated in a housing 14. The housing 14 is formed in a substantially cylindrical shape. The motor portion 20 is disposed on an upper side of the housing 14, and the pump portion 40 is accommodated in a lower side of the housing 14. A motor cover 16 is fixed to an upper edge of the housing 14. An output port 18 open upward and a connector terminal 50 connected to an external power supply are formed on the motor cover 16.The motor portion 20 includes a rotor 22 and a stator 32 disposed on an outer periphery of the rotor 22. As described later, the rotor 22 includes a shaft 24, a support yoke 62 (shown in FIG. 2 ), and permanent magnets 64 ato 64 d(shown in FIG. 2 ). The shaft 24 is rotatably supported by bearings 26 and 28 relative to the housing 14. The stator 32 includes a yoke in which a plurality of slots are formed. The plurality of slots are spaced apart in the circumferential direction of the stator 32. The front end surfaces of the plurality of slots face the outer circumferential surface of the rotor 22 with a gap therebetween (however, the gap is not shown in FIG. 1 ). A coil is wound around each slot. The connector terminal 50 is connected to each coil.The pump portion 40 includes an impeller 44 having an approximately disk shape, and pump housings 38 and 42 accommodating the impeller 44. A group of recesses 44a are formed on an upper surface of the impeller 44 along the outer peripheral edge thereof. A group of recesses 44b are formed on a lower surface of the impeller 44 along the outer peripheral edge thereof. A through hole is formed at the center of the impeller 44, and the shaft 24 is fitted to the through hole so as to be non-rotatable relative to the through hole. Consequently, when the shaft 24 rotates, the impeller 36 also rotates.The pump housings 38 and 42 are fixed to the lower end of the housing 14 in a state where the impeller 44 is accommodated in the pump housings 38 and 42. The pump housings 38 and 42 include an outlet-side housing 38 and an inlet-side housing 42. A groove 38a is formed in a portion of the outlet-side housing 38 facing the group of recesses 44a on the upper surface of the impeller 44. The groove 38a is formed approximately in a C shape and extends from an upstream end to a downstream end along the rotational direction of the impeller 44. An outlet port (not shown) extending from the downstream end of the groove 38a to the upper surface of the outlet-side casing 38 is formed in the outlet-side casing 38. The outlet port allows the interior of the pump housing to communicate with the outside (i.e., the inner space of the motor portion 20).A groove 42a is formed in a portion of the inlet-side casing 42 facing the group of recesses 44b on the lower surface of the impeller 44. Similarly to the groove 38a, the groove 42a is formed in an approximate C shape and extends from the upstream end to the downstream end along the rotational direction of the impeller 44. The inlet port 46 allows the inside of the pump housings 38 and 42 to communicate with the outside (the outside of the fuel pump 10).In the fuel pump 10 described above, when electric power is supplied to the coil of the stator 32 via the connector terminal 50, the rotor 22 rotates. When the impeller 44 rotates with the rotation of the rotor 22, fuel is sucked into the pump housing from the inlet port 46 of the inlet-side housing 42. The fuel sucked into the pump housings 38 and 42 flows from the upstream end to the downstream end through pump passages 42 a, 44 b, 44 aand 38 awhile being pressurized. The fuel pressurized in the pump passages is supplied through the outlet port into the housing 14 of the engine section 20. The fuel supplied into the housing 14 flows upward in the housing 14 and is discharged from the outlet port 18 of the engine cover 16.Next, the structure of the rotor 22 will be described in detail. As shown in FIGS. 2 and 3, the rotor 22 includes the shaft 24, the yoke 62 fixed to the shaft 24, and permanent magnets 64 ato 64 ddisposed on the outer circumferential surface of the yoke 62.The shaft 24 extends through the yoke 62, and an engaging portion 24a engaged with a through hole of the impeller 44 is formed at a lower end of the shaft 24. A cross section (hereinafter often referred to simply as a perpendicular cross section) of the engagement portion 24 aperpendicular to a shaft axis line A has an approximately D shape. Consequently, when the engaging portion 24a of the shaft 24 is engaged with the through hole of the impeller 44, the shaft 24 and the impeller 44 integrally rotate with each other. In regions other than the engagement region 24 a, the vertical cross section of the shaft 24 has an outer circular shape (see FIG. 3 ).The yoke 62 includes a plurality of core plates 62 stacked in the axial direction. Each core plate 62 is formed of a magnetic steel plate. As shown in FIG. 3, a through hole 66 is formed at the center of each core plate 62. Since the through hole 66 is formed in each core plate 62, the through holes 66 extending in the axial direction are formed in the yoke 62 (see FIG. 2 ). The shaft 24 is press-fitted with the through hole 66 of the yoke 62. as shown in FIG. 3, the perpendicular cross section of the through hole 66 has a rectangular shape, and the perpendicular cross section of the shaft 24 has a circular shape. Consequently, when the shaft 24 is press-fitted with the through hole 66 of the yoke 62, four communication holes 66 aare formed between the outer circumferential surface of the shaft 24 and the inner circumferential surface of the through hole 66 of the core plate 62. Each transmission hole 66 aextends parallel to the shaft axis line and passes through the yoke 62.The permanent magnets 64 ato 64 dare disposed on the outer circumferential surfaces of the yoke 62. Each of the permanent magnets 64 ato 64 dextends from the upper end to the lower end of the yoke 62, and the perpendicular cross section thereof has an arc shape (see FIG. 3 ). Accordingly, when the permanent magnets 64a to 64d are disposed on the outer circumferential surfaces of the yoke 62, the respective permanent magnets 64a to 64d contact the adjacent permanent magnets and form cylindrical permanent magnet portions. The permanent magnets 64a to 64d are alternately magnetized in different directions. For example, the permanent magnets 64 aand 64 care magnetized such that the outer circumferential surface becomes the N pole, and the inner circumferential surface becomes the S pole. Moreover, the permanent magnets 64 band 64 dare magnetized such that the outer circumferential surface becomes the S pole, and the inner circumferential surface becomes the N pole. As is clear from FIG. 3, in a cross section perpendicular to the shaft axis line A, each transmission hole 66 ais positioned on a line B connecting the center in the circumferential direction of the permanent magnets 64 ato 64 dand the shaft axis line A.As shown in FIG. 2, a first resin portion 68 ais formed on the lower surface of the yoke 62 and the lower surfaces of the permanent magnets 64 ato 64 d. Moreover, a second resin portion 68 bis formed on the upper surface of the yoke 62 and the upper surfaces of the permanent magnets 64 ato 64 d. The first and second resin portions 68 aand 68 bare formed to extend over the yoke 62 and the permanent magnets 64 ato 64 d, thereby fixing the permanent magnets 64 ato 64 dto the yoke 62.Moreover, a third resin portion 68 cis formed in each transmission hole 66 aformed between the shaft 24 and the yoke 62. Since the transmission holes 66 apass through the yoke 62 in the shaft axis direction, the lower ends of the third resin portions 68 care connected to the first resin portion 68 a, and the upper ends of the third resin portion 68 care connected to the second resin portion 68 b. That is, the third resin portions 68 cconnect the first and second resin portions 68 aand 68 bto each other.In the fuel pump 10 according to the present embodiment, by forming the transfer hole 66 ain the rotor 22, the first, second, and third resin portions 68 a, 68 b, and 68 cmay be integrally formed by a single resin molding process. This will be described in detail with reference to an example of a method of manufacturing the rotor 22. When the rotor 22 is manufactured, first, the shaft 24 is press-fitted with the through hole 66 of the yoke 62, and then, in a state where the permanent magnets 64 ato 64 dare disposed on the outer circumferential surface of the yoke 62, the shaft 24, the yoke 62, and the permanent magnets 64 ato 64 dare disposed in a shape. In order to improve the mobility of an in-mold resin, ports are formed on the upper or lower side of the yoke 62 in the mold. Moreover, resin is injected into the mold to form the respective resin portions 68 a, 68 b, and 68 c. For example, when the openings are formed on the lower surface side of the yoke 62, the resin injected into the mold flows into a space for forming the first resin portion 68 a. The resin flows into the space for forming the first resin portion 68 a, so that the space is filled with the resin. The resin flows into a space for forming the second resin portion 68 bthrough the transfer hole 66 a, so that the space is filled with the resin. As a result, the first, second and third resin portions 68 a, 68 band 68 care integrally formed by a single resin molding process.In the fuel pump 10 described above, the shaft 24 is fixed to the yoke 62 by press-fitting. A centrifugal force acting on the yoke 62 and the permanent magnets 64 ato 64 dduring the rotation of the rotor 22 thus directly acts on the shaft 24, and is not applied to the third resin portions 68 c. The transfer hole 66 atherefore only needs to serve as a resin flow path when the first and second resin portions 68 aand 68 bare formed. As a result, it is possible to make the third resin portions 68 cindividual and suppress an increase in size of the rotor 22. Since the shaft 24 and the yoke 62 are fixed by press-fitting, the shaft 24 and the yoke 62 can be fixed more reliably as compared with holding the same using the resin portion. Moreover, it is possible to prevent the fuel pump 10 from becoming larger.In addition, in the fuel pump 10 described above, it is not necessary to form a resin flow path on the outer sides of the permanent magnets 64 ato 64 d, because it is sufficient that a resin flows into the transfer hole 66 awhen the first and second resin portions 68 aand 68 bare formed. As a result, no resin portion is formed on the outer circumferential surfaces of the permanent magnets 64 ato 64 d, and the gap between the permanent magnets 64 ato 64 dand the stator 32 can be reduced. Further, since it is not necessary to flow resin into a space between adjacent permanent magnets, the adjacent permanent magnets can make contact with each other, and the angle between the permanent magnets 64 ato 64 dmay be increased. Consequently, it is possible to improve an engine performance and a pump efficiency of the fuel pump 10.In the cross section perpendicular to the shaft axis line A, moreover, each transmission hole 66 ais positioned on a line B connecting a center of the corresponding one of the permanent magnets 64 ato 64 din the circumferential direction with the shaft axis line A (see FIG. 3 ). Thus, the transmission holes 66a are disposed at positions farthest from the boundary line between the adjacent permanent magnets (i.e., between the permanent magnets 64a and 64b, 64b and 64c, 64c and 64d or 64d and 64a). Consequently, due to the transmission holes 66 a, a magnetic flux area in which a magnetic flux flowing between the adjacent permanent magnets passes through the yoke 62 is prevented from being reduced. As a result, increase in magnetic resistance due to the transmission holes 66 ais suppressed, and reduction in motor efficiency is suppressed.In the first embodiment described above, although a plurality of permanent magnets 64a to 64d are arranged on the outer peripheral surface of the yoke 62, as shown in FIG. 4, a cylindrical permanent magnet 70 may be arranged on the outer peripheral surface of the yoke 62. In this structure, the permanent magnet 70 may be magnetically divided into a plurality of circumferential direction regions 70 ato 70 d, and the respective regions 70 ato 70 dmay be alternately magnetized in different directions.Moreover, in the above-described first embodiment, although a transmission hole 66 ais formed between the yoke 62 and the shaft 24, as shown in FIGS. 5 and 6, transmission holes 74 may be formed in the yoke 72. That is, a partial transmission hole extending in the axial direction may be formed in each core plate 72 constituting the yoke 72, and the partial transmission holes of the respective core plates 72 may constitute the transmission hole 74. According to this configuration, since the first and second resin portions 78 aand 78 bare connected by the third resin portions 78 cformed in the transmission holes 74, it is possible to integrally form these resin portions 78 a, 78 band 78 c.In the example shown in FIGS. 5 and 6, in a cross section perpendicular to the shaft axis line A, each transmission hole 74 is positioned on a line B connecting the center of the corresponding one of the permanent magnets 76 ato 76 din the circumferential direction and the shaft axis line A (see FIG. 6 ). Consequently, a magnetic flux region in which a magnetic flux passes through the yoke 72 is prevented from being reduced due to the transmission holes 74. Moreover, since the respective core plates 72 are thin, it is possible to easily form the partial transmission holes in the respective core plates 72. Further, the through hole of the yoke 72 with which the shaft 24 is press-fitted has a circular perpendicular cross section and makes contact with the outer circumferential surface of the shaft 24 with the entire circumference.In the example shown in FIGS. 5 and 6, although four permanent magnets are disposed on the outer circumferential surfaces of the yoke 72 as shown in FIG. 7, only one cylindrical permanent magnet 80 may be disposed on the outer circumferential surface of the yoke 72.Moreover, the rotor 22 according to the above-described first embodiment may be modified to have a structure as shown in FIG. 8. In the rotor shown in Fig. 8, a convex portion 88a is formed on the outer circumferential surfaces of the yoke 82, and a concave portion 88b is formed at the boundaries between the respective permanent magnets 86a to 86d. When the permanent magnets 86a to 86d are placed on the outer circumferential surfaces of the yoke 82, the convex portions 88a of the yoke 82 are engaged with the concave portions 88b of the permanent magnets 86a to 86d. According to this configuration, since the permanent magnets 86 ato 86 dare prevented from rotating about the shaft axis line relative to the yoke 82, the permanent magnets 86 ato 86 dmay be positioned at appropriate locations relative to the yoke 82.In the rotor shown in FIG. 9, similarly to the rotor shown in FIG. 8, it is possible to prevent the permanent magnets 94 ato 94 dfrom rotating the shaft axis line relative to the yoke 82. That is, in the rotor shown in FIG. 9, a plurality of bent portions 92 ato 92 dare formed on the outer circumferential surfaces of the yoke 92, and both end portions 96 ato 96 dof the respective permanent magnets 86 ato 86 dhave shapes corresponding to the bent portions 92 ato 92 d. According to this configuration, it is possible to prevent the permanent magnets 94 ato 94 dfrom rotating the shaft axis line relative to the yoke 92. The folded portions 92a to 94d may be formed at any position in the rotational direction.In the rotor according to the first embodiment, although the outer circumferential surfaces of the permanent magnets 64 ato 64 dare not covered with a resin, the present invention is not limited to such an embodiment, the rotor may further include a fourth resin portion covering the outer circumferential surfaces of the permanent magnets, and first to fourth resin portions may be integrally formed. Further, the rotor may include a structure that aligns the core plates constituting the yoke. When a convex portion is formed on the upper surface of the core plate and a concave portion is formed on the lower surface of the core plate to stack the core plates, the core plates are stacked such that the convex portion on the upper surface of the core plate is engaged with the concave portion on the lower surface of the core plate. This prevents positional displacement between the core plates, and handling of the core plates becomes easy.(Second Embodiment)In a fuel pump according to a second embodiment, the rotor 22 of the fuel pump 10 according to the first embodiment is modified. In this embodiment, therefore, only the structure of the rotor different from that of the fuel pump 10 according to the first embodiment will be described.As shown in FIG. 10, in the rotor 22 according to the second embodiment, restriction plates 100 and 102 are disposed on the upper and lower ends of the yoke 62 and the permanent magnets 64 ato 64 d, respectively. The same through hole as the through hole 66 of the core plates 62 is formed at the center of each restriction plate 100 and 102. When the shaft 24 is press-fitted with the through holes of the restriction plates 100 and 102, a transmission hole is also formed between the shaft 24 and the restriction plates 100 and 102. As a result, the restriction plates 100 and 102 can be fixed to the shaft 24, and the first, second and third resin portions 103 a, 103 band 103 cmay be integrally formed.Engaging portions 100a and 102a are formed on the outer peripheral edges of the restriction plates 100 and 102. A plurality of the engaging parts 100 aand 102 aare formed with a pitch in the circumferential direction. The respective engaging portions 100a and 102a are engaged with the permanent magnets 64a to 64d. Thereby, the permanent magnets 64 ato 64 dare prevented from being rotated relative to the yoke 62 and moving in the shaft axis direction. Consequently, it is possible to prevent positional displacement of the permanent magnets 64 ato 64 drelative to the yoke 62 due to resin pressure when the resin parts 103 a, 103 band 103 care formed.In the rotor 22 according to the second embodiment, although the engaging parts 100 aand 102 aare formed in the restriction plates 100 and 102, the present teaching is not limited to such an embodiment, and the rotor 22 may have a structure as shown in FIG. 11. In the rotor 22, as shown in Fig. 11, engaging portions 67a and 67b are formed on the upper and lower edges of the magnets 65a to 65d, and these engaging portions 67a and 67b are engaged with the restriction plates 106 and 104. According to such a configuration, it is also possible to prevent positional displacement of the permanent magnets 65 ato 65 drelative to the rear yoke 62. In this embodiment, each of the restriction plates 100, 102, 104, and 106 is an example of the "magnet holder".In the example shown in FIGS. 10 and 11, although the engaging parts 100 aand 102 aor 67 aand 67 bare formed in a portion of the circumference, the present teaching is not limited to such an embodiment, and the engaging part may be formed on the entire circumference of the restriction plates or the permanent magnets. According to such a configuration, it is also possible to prevent positional displacement of the permanent magnets relative to the yoke.(Third Embodiment)In a fuel pump according to a third embodiment, the rotor 22 of the fuel pump 10 according to the first embodiment is modified. In this embodiment, only the structure of the rotor different from that of the fuel pump 10 according to the first embodiment will be described.In the rotor 22 according to the third embodiment, as shown in Figs. 12 to 14, restriction plates 110 are disposed on the upper and lower ends of the yoke 114 and the permanent magnets 116. As shown in FIG. 13, four permanent magnets 116 are disposed on the outer circumferential surfaces of the yoke 114. A concave portion 116a is formed at the boundary between the adjacent permanent magnets 116, and a convex portion 114a formed on the outer circumferential surface of the yoke 114 is engaged with the concave portion 116a. This limits rotation of the permanent magnets 116 relative to the yoke 114. Moreover, the convex portion 114 ais an example of the "circumferential position regulating portion". Similarly to the first embodiment, a through hole having a rectangular perpendicular cross section is formed at the center of each yoke 114, and the shaft 24 is press-fitted with the through hole. Thus, in the rotor 22 according to the third embodiment, a transmission hole extending parallel to the shaft axis is also formed between the shaft 24 and the yoke 114.As shown in Fig. 14, the same through hole 117 as the through hole of the yoke 114 is formed at the center of the restriction plate 110. That is, a cross section of the through hole 117 perpendicular to the shaft axis has a rectangular outer shape, and the shaft 24 is press-fitted with the through hole 117. Moreover, a transmission hole communicating with the transmission hole formed between the yoke 114 and the shaft 24 is formed between the restriction plate 110 and the shaft 24. Since the shaft 24 is press-fitted with the through hole 117, positional displacement of the restriction plate 110 relative to the shaft 24 is prevented. Moreover, since the transmission hole extending in the shaft axis direction is formed in the yoke 114 and the restriction plate 110, the resin portions 111 aand 111 bformed on both ends of the shaft 24 can be integrally formed with a resin portion formed in the transmission hole (however, the resin portion is not shown because FIG. 12 shows a cross section of a portion where the transmission hole is not formed, and the resin portion is not shown in FIGS. 13 and 14 ).As shown in Fig. 14, four engaging parts 112 are formed on an outer peripheral edge of the restriction plate 110. The four engaging parts 112 are arranged at equal intervals in the circumferential direction. Each engaging part 112 is engaged with a central portion in the circumferential direction of the permanent magnet 116. Thereby, the permanent magnet 116 is limited from rotating about the shaft axis relative to the yoke 114 and from moving in the shaft axis direction. Consequently, due to a resin pressure when the resin portions 111 aand 111 bare formed, it is possible to more reliably prevent a positional displacement of the permanent magnets 116 relative to the yoke 114.The restriction plates disposed on the upper and lower edges of the yoke are not limited to those shown in Fig. 14, and a restriction plate 118 as shown in Fig. 15 may be used. In the restriction plate 118, as shown in Fig. 15, an engaging wall 118a is formed on the entire outer peripheral edge thereof, and the permanent magnet is engaged with the engaging wall 118a. Consequently, it is possible to more reliably prevent positional displacement of the permanent magnet. In this embodiment, each of the restriction plates 110, 118 is an example of the "magnet holder".(Fourth Embodiment)In a fuel pump according to a fourth embodiment, the rotor 22 of the fuel pump 10 according to the first embodiment is modified. In this embodiment, therefore, only the structure of the rotor different from that of the fuel pump 10 according to the first embodiment will be described.As shown in FIGS. 16 to 18, the rotor 22 according to the fourth embodiment also has approximately the same structure as the rotor 22 according to the third embodiment. However, the rotor 22 according to the fourth embodiment includes restriction plates 120 having a different configuration from that of the third embodiment. That is, the restriction plates 120 are disposed on the upper and lower ends of the back yoke 124 and the permanent magnets 126 (126a to 126d). As shown in FIG. 17, a through hole 121 whose cross section perpendicular to the shaft axis has a rectangular shape is formed at the center of each restriction plate 120, and the shaft 24 is press-fitted with the through hole 121. Moreover, four engaging parts 130 are formed on the outer peripheral edges of the restriction plates 120. The respective engaging parts 130 are engaged with the permanent magnets 126a to 126d at the boundaries between adjacent permanent magnets (i.e., the boundaries between the permanent magnets 126a and 126b, 126b and 126c, 126c and 126d, and 126d and 126a). Specifically, as shown in FIG. 18, at the boundaries between the adjacent permanent magnets (i.e., at the boundaries between the permanent magnets 126 aand 126 b, 126 band 126 c, 126 cand 126 d, and 126 dand 126 a), a concave portion 127 is formed at the outer peripheries of the boundaries. Each engaging part 130 is bent upward or downward and makes contact with side surfaces of the permanent magnets 126 ato 126 din the concave portions 127.In the fourth embodiment, the restriction plates 120 are disposed on the upper and lower edges of the yoke 124 and the permanent magnets 126, and a positional displacement of the yoke 124 relative to the permanent magnets 126 is restricted by the restriction plates 120. Thereby, it is possible to form a resin portion in a state where the permanent magnets 126 are positioned at appropriate positions relative to the yoke 124. Moreover, the engaging portions 130 of the restriction plates 120 make contact with the permanent magnets 126 at boundaries between the permanent magnets 126 ato 126 d. Consequently, it is possible to prevent the engaging parts 130 from influencing the magnetic field generated by the permanent magnets 126 ato 126 d. As a result, it is possible to prevent deterioration of the motor efficiency and deterioration of the pump efficiency. Moreover, the restriction plate 120 is an example of the "magnet holder".A permanent magnet 132 as shown in FIG. 19 may be used in the rotor 22 according to the fourth embodiment. As shown in Fig. 19, a contact portion 132a which makes contact with the engaging portion 130 of the restriction plate 120 is formed on one end of the permanent magnet 132. On the other hand, a contact portion 132b which makes contact with the contact portion 132a of the adjacent permanent magnet 132 is formed on the other end of the permanent magnet 132 from the inner side. In the example shown in FIG. 19, the engaging part 130 makes contact with only one end of the permanent magnet 132, and a contact area between the engaging part 130 and the permanent magnet 132 can be increased. Consequently, one end of the permanent magnet 132 can be stably held by the restriction plate 120. Further, the other end of the adjacent permanent magnet 132 is engaged with one end of the adjacent permanent magnet, and these ends can be pressed toward the inner side by the engaging member 130. Consequently, it is possible to prevent the permanent magnet 132 from dropping off when the rotor rotates.(Fifth Embodiment)In a fuel pump according to a fifth embodiment, the rotor 22 of the fuel pump 10 according to the first embodiment is modified. In this embodiment, therefore, only the structure of the rotor different from that of the fuel pump 10 according to the first embodiment will be described.As shown in FIGS. 20 and 21, in the rotor 22 according to the fifth embodiment, restriction plates 142 and pressing members 144 band 146 bare disposed on the upper and lower ends of the yoke 141 and the permanent magnets 140. Resin portions 144 aand 146 aare formed on the lower surface of the pressing member 144 band the upper surface of the pressing member 146 b, respectively. As is clear from FIG. 20, the outer diameters of the restriction plates 142, the pressing members 144 band 146 b, and the resin portions 144 aand 146 aare smaller than the inner diameter of the stator 32.As shown in FIG. 23, the restriction plate 142 is a plate member in which a portion 148 dis open in the circumferential direction, and is configured to press the permanent magnets 140 toward the back yoke 141 due to an elastic force thereof. Thus, before the resin portions 144 aand 146 aare formed, the yoke 141 and the permanent magnets 140 may be treated as integral bodies. The shaft 24 is press-fitted with a through hole of the yoke 141, and transmission holes 141 aare formed between the shaft 24 and the yoke 141. Similarly to the above-described embodiment, a resin portion (not shown) connecting the resin portions 144 aand 146 bis formed in the transmission hole 141 a.As shown in FIG. 24, the restriction plate 142 includes an annular portion 148 cthat makes contact with the outer circumferential surface of the permanent magnet 140, and a plurality of protruding parts 148 aof which a set of ends is connected to the annular portion 148 c. A portion 148 din the circumferential direction is open to the annular portion 148 c, and the dimension of the annular portion 148 cmay be increased due to its elastic force. Even if the thicknesses of the permanent magnets 140 vary, the annular portion 148 cmay follow the variations. The plurality of protruding parts 148 aare bent relative to the annular portion 148 cand arranged at equal intervals in the circumferential direction. A through hole 148 bis formed in the front end portions of the plurality of protruding parts 148 a.The pressing members 144 band 146 bare members for pressing the restriction plate 142 toward the permanent magnet 140 and adjusting weight balance of the rotor 22, and the pressing members 144 band 146 bmay be formed of a metal material such as stainless steel. Since the pressing members 144 band 146 bhave the same structure, only the pressing member 146 bis described.As shown in FIG. 22, the pressing member 146 bincludes a through hole 152 into which the shaft 24 is press-fitted with its center, and a plurality of through holes 150 arranged along its outer periphery. The through hole 152 has the same shape as the through holes (see FIG. 23 ) of the yoke 141. Consequently, transmission holes 152a communicating with the transmission holes 141a formed between the yoke 141 and the shaft 24 are also formed between the pressing members 146b and the shaft 24. Thus, in the fifth embodiment, the resin portions 144 aand 146 acan be formed by a single resin molding process. The through hole 150 is formed at a position corresponding to the through hole 148b formed in the front end portion of the protruding part 148a of the restriction plate 142. Consequently, when the resin portions 144 aand 146 aare formed, a resin flows into the inside of the through hole 150 of the pressing members 144 band 146 band the through hole 148 bof the restriction plate 142, and the inside thereof is filled with resin. As a result, all the pressing members 144 band 146 b, the restriction plate 142, the permanent magnet 140, and the yoke 141 are fixed after the resin injection process. The opening 148d of the restriction plate 142 can be prevented from being deformed according to the force of the permanent magnet 140 to be separated from the yoke 141 according to the centrifugal force during the rotation of the rotor 22. Thus, the permanent magnet 140 is prevented from being separated from the yoke 141.In the rotor 22 according to the fifth embodiment, since the shaft 24 is press-fitted to the yoke 141 and the pressing members 144 band 146 b, the resin portion does not need a holding force against the centrifugal force, and a large mechanical strength is not required for the resin portion. As a result, it is possible to suppress the size increase of the rotor 22. Moreover, since the rotor 22 includes the transmission holes 141 aand 152 aextending through the yoke 141 and the pressing members 144 band 146 b, it is possible to form the resin portions 144 aand 146 aby a single resin injection process.Further, in the rotor 22 according to the fifth embodiment, the restriction plates 142 and the pressing members 144 band 146 bare disposed on both upper and lower ends of the permanent magnet 140. Consequently, positional displacement of the permanent magnet 140 relative to the yoke 141 is unlikely to occur, and the yoke 141 and the permanent magnet 140 can be maintained in an appropriate positional relationship when the resin portions are formed. As a result, it is possible to manufacture the rotor 22 with high accuracy. Moreover, it is possible to control the flow of a resin with the pressing members 144 band 146 bin such a manner that the resin does not enter the opening of the restriction plate 142 and the clearance between the permanent magnets 140, and deburring or removal of the resin is prevented.A restriction plate 154 as shown in Fig. 25 may be used as the restriction plate disposed in the end portion of the permanent magnet 140. As shown in Fig. 25, the restriction plate 154 includes an annular plate portion 155 which makes contact with the upper or lower end face of the permanent magnet 140. A protruding part 156 in which a through hole 158 is formed is formed on an inner peripheral edge of the plate portion 155. According to such a configuration, since deformation of the restriction plate 154 is prevented by the plate portion 155, it is possible to appropriately hold the permanent magnet 140.Alternatively, a restriction plate 160 as shown in Figs. 26 to 28 may be used. As shown in Figs. 26 to 28, the restriction plate 160 includes a first planar portion 160 which makes contact with the end surfaces of the yoke 141, and a second planar portion 160b which makes contact with the outer circumferential surface of the permanent magnet 140. A through hole 164 is formed at the center of the first planar portion 160 a. The through hole 164 has the same shape as the through hole 152 formed at the center of the pressing members 144 band 146 b. On the other hand, slits 162 are formed in the second planar portion 160 bwith a circumferential distance (see FIG. 26 ). Since the slits 162 are formed in the second planar portion 160 b, the second planar portion 160 bmay be deformed according to the thickness of the permanent magnet 140. In this embodiment, each of the restriction plates 142, 154, and 160 is an example of the "magnet holder".(Modification)In the above-described embodiments, although a plurality of core plates are stacked to form the yoke, the present invention is not limited to such an embodiment, and a cylindrical support yoke may be used, for example.(Sixth Embodiment)In a fuel pump 210 according to this embodiment, the rotor 22 of the fuel pump 10 according to the first embodiment is modified. In this example, only the structure of the rotor different from that of the fuel pump 10 according to the first embodiment will be described. In FIG. 29, the same configurations as those of the fuel pump 10 according to the first embodiment are denoted by the same reference numerals as those used in FIG. 1. In FIG. 29, a small gap is shown between the front end surfaces of a plurality of slits and the outer circumferential surface of a rotor 250.As shown in FIG. 29, the rotor 250 includes a shaft 24, a plurality of (four in this embodiment) permanent magnets 260, two magnet holders 258 and 262, two pressing members 256 and 264, a resin layer 254, and a back yoke 266 (see FIG. 34 ).As shown in FIG. 34, the yoke 266 includes a plurality of core plates 266 astacked in a direction of the axial line X. Each core plate 266a is formed of a magnetic steel plate. A through hole is formed at the center of each core plate 266a. Due to the through hole formed in each core plate 266 a, a through hole 266 bextending in the direction of the axial line X is formed in the yoke 266. The shaft 24 is press-fitted with the through hole 266 bof the yoke 266. The through hole 266 bhas the same shape as a through hole 294 described later when viewed from the axial line X direction. When the shaft 24 is press-fitted with the through hole 266 bof the yoke 266, four transmission holes 270 are formed between the outer circumferential surface of the shaft 252 and the inner circumferential surface of the through hole 266 bof each core plate. Each transmission hole 270 extends parallel to the direction of the axial line X and passes through the yoke 266.The plurality of permanent magnets 260 have the same structure as the permanent magnets 64 ato 64 d. An outer circumferential surface 260 a, which is closer to the axial line X than an outer circumferential surface 260 bat an intermediate portion of each permanent magnet 260 in a perpendicular cross section, is formed on an upper end portion of each permanent magnet 260. Similarly, an outer circumferential surface 260 c, which is closer to the axial line X than the outer circumferential surface 260 bis formed at an intermediate portion of the permanent magnets 260 in a perpendicular cross section in a lower end portion of each permanent magnet 260. The outer circumferential surfaces 260 aand 260 care closer to the axial line X than the outer circumferential surface 260 bto an extent corresponding to the thickness of the magnet holders 258 and 262 described later. The outer diameter of a cylinder formed of a plurality of outer circumferential surfaces 260 aand a plurality of outer circumferential surfaces 260 cis smaller than the outer diameter of a cylinder formed of a plurality of outer circumferential surfaces 260 b.The magnet holder 258 is disposed on the upper surface of the yoke 266 and the upper surfaces of the permanent magnets 260. The magnet holder 258 is made of a non-magnetic material. As shown in FIG. 31, the magnet holder 258 includes a base portion 280 and a plurality of (four in this embodiment) peripheral wall portions 282. The base portion 280 has a circular planar shape. The base portion 280 faces the upper surface of the yoke 266 and the upper surfaces of the permanent magnets 260. The outer diameter of the base portion 280 in a state before being attached to the plurality of permanent magnets 260 is slightly smaller than the outer diameter of a cylinder formed by the outer circumferential surfaces 260 aof the plurality of permanent magnets 260. As shown in FIG. 31, the base portion 280 includes an inner peripheral part 290 and a plurality of (four in this embodiment) peripheral parts 281.The inner peripheral part 290 has a ring shape such that it has a through hole 294 at its central portion. The diameter of the through hole 294 is slightly smaller than the diameter of the shaft 24. a plurality (four in this embodiment) of rectangular transmission holes 296 extending in a radial direction (hereinafter referred to as a "first radial direction") of the base portion 280 is formed in the through hole 294. The plurality of through holes 296 are arranged at equal intervals in the circumferential direction (hereinafter referred to as "circumferential direction") of the base portion 280. The shaft 24 is press-fitted with the through hole 294. As a result, each transmission hole 296 communicates with each transmission hole 270 formed by the shaft 24 and the yoke 266. In other words, each transmission hole 270 extends parallel to the axial line X and passes through the yoke 266 and the magnet holder 258.The plurality of circumferential parts 281 are spaced around the outer periphery of the inner circumferential part 290. A notch 292 is formed between adjacent circumferential parts 281. The notch 292 has a structure in which a second part 292 aextending in the circumferential direction is connected to an inner end in the first radial direction of a first part 292 bextending in the first radial direction. The first part 292b is located at a position corresponding to the boundary between adjacent permanent magnets 260.Each circumferential part 281 has a partial circular shape. The inner peripheral part 290 is connected to the inner peripheral edge of each peripheral part 281. A connection part 281 aconnected to the peripheral wall portion 282 is formed on the outer peripheral edge of each peripheral part 281 (see FIG. 30 ). On an inner peripheral side of each peripheral part 281, a beam part 286 is formed at both ends in the circumferential direction of each peripheral part 281. Each peripheral portion 281 thus includes two beam portions 286. Each beam portion 286 is a portion of the base portion 280 that has a smallest width. Each beam portion 286 is a portion of the base portion 280 that has the lowest strength. Each beam portion 286 extends circumferentially, and the inner circumferential portion 290 is connected to one end of each beam portion 286. An outer peripheral portion 284 is connected to the other end of each beam portion 286. The inner peripheral part 290 and the outer peripheral part 284 are thus connected by two beam parts 286. Each of the two beam parts 286 is connected to one end in the circumferential direction of the outer circumferential part 284. A through hole 288 is formed between the outer peripheral part 284 and the inner peripheral part 290. The through hole 288 is located more on the outer side in the first radial direction than the second portion 292 aand extends in the circumferential direction. Each beam part 286 is formed between the through hole 288 and the notch 292. More specifically, when the beam part 286 is tracked toward the outer side from the inner side in the first radial direction, the beam part 286 extends in the circumferential direction between the through hole 288 and the second part 292 aand then extends in the first radial direction between the through hole 288 and the first part 292 b.Since the first part 292 bof the notch 292 is located at the boundary between the two permanent magnets 260, each outer peripheral part 284 is disposed at such a position that the outer peripheral part 284 faces the end face of each permanent magnet 260. The circumferential wall portion 282 is connected to the outer end in the first radial direction of each outer circumferential part 284. As shown in FIG. 30, the peripheral wall portion 282 vertically protrudes toward the permanent magnets 260 from the base portion 280. The length in the circumferential direction of the circumferential wall portion 282 is the same as the length in the circumferential direction of the outer end in the first radial direction of the outer circumferential part 284. In this configuration, the plurality of circumferential wall portions 282 form a cylindrical shape. The circumferential wall portion 282 is connected to the outer circumferential part 284 with the entire length in the circumferential direction. As shown in FIG. 31, in a plane perpendicular to the axial line X, the angle θ between a line connecting one end in the circumferential direction of the connection part 281 aand the center O (i.e., the center of the shaft 24) and a line connecting the other end in the circumferential direction of the connection part 281 aand the center O of the base portion 280 is 86°.As shown in FIG. 30, when the magnet holder 258 is attached to the permanent magnets 260, the shaft 24 and the through hole 294 are press-fitted. Moreover, the permanent magnets 260 engage with the cylindrical shape formed by the plurality of circumferential wall portions 282. Thereby, the outer circumferential surface 260 aof each permanent magnet 260 makes contact with the inner circumferential surface of the circumferential wall portion 282 of the magnet holder 258. In a state before the magnet holder 258 is attached to the permanent magnets 260 (i.e., in a normal state), the inner diameter of the cylinder formed by the plurality of circumferential wall portions 282 is slightly smaller than the outer diameter of the cylinder formed by the outer circumferential surfaces 260 aof the plurality of permanent magnets 260. Consequently, when the permanent magnet 260 is engaged with the cylinder formed by the plurality of circumferential wall portions 282, the beam part 286 of the base portion 280 having the lowest strength is deformed, and the outer circumferential part 284 is displaced to be separated from the inner circumferential part 290. As a result, the permanent magnets are fitted into the magnet holder 258. In this case, the peripheral wall portion 282 vertically protruding toward the permanent magnets 260 from the base portion 280 is held at a vertical angle with respect to the base portion 280. Thus, when the magnet holder 258 is attached to the permanent magnet 260, the peripheral wall portion 282 is not inclined toward the outer side of the rotor 250. In other words, the beam part 286 is formed such that the circumferential wall portion 282 is not inclined toward the outer side of the rotor 250 in a state where the magnet holder 258 is attached to the permanent magnet 260. The base portion 280 is in contact with the upper surface of the yoke 266, and a gap is formed between the base portion 280 and the upper surface of the permanent magnet 260.The magnet holder 262 is disposed between the lower surface of the yoke 266 and the lower surface of the permanent magnet 260. The magnet holder 262 has the same structure as the magnet holder 258. The magnet holder 262 is attached to the permanent magnet 260 such that the shaft 24 is press-fitted with the through hole of the magnet holder 262, and the permanent magnets 260 are engaged with the cylinder formed by the plurality of circumferential wall portions. As a result, each transmission hole 270 passes through the magnet holder 262, and the yoke 266 and the magnet holder 258. The outer diameter of the base portion of the magnet holder 262 is slightly smaller than the outer diameter of the cylinder formed by the outer circumferential surfaces 260 cof the plurality of permanent magnets 260. Thus, when the magnet holder 262 is attached to the permanent magnet 260, the magnet holder 262 is deformed in a similar manner as in the case where the magnet holder 258 is attached to the permanent magnet 260.The pressing member 256 is disposed on a side of the magnet holder 258 opposite to the permanent magnets 260. As shown in FIG. 30, the pressing member 256 includes a pressing portion 302 and an outer peripheral portion 300. The pressing portion 302 has a disc shape. The pressing portion 302 has a radius approximately the same as that of the base portion 280 in a state of being attached to the permanent magnets 260. The pressing portion 302 is attached to the shaft 24 in a state of being in contact with the base portion 280. The through hole 306 is formed in a central portion of the pressing portion 302. A diameter of the through hole 306 is slightly smaller than the diameter of the shaft 24. A plurality of rectangular transmission holes 308 having the same shape as the through hole 296 are formed in the through hole 306 at a position overlapping the transmission hole 296 of the magnet holder 258. The shaft 24 is press-fitted with the through hole 306. When the shaft 24 is press-fitted with the through hole 306, the outer circumferential surface of the shaft 24 and the through holes 308 form a transmission hole communicating with the transmission hole 270 formed by the shaft 24, the yoke 266, and the magnet holders 258 and 262. In other words, each transmission hole 270 passes through the yoke 266, the magnet holders 258 and 262, and the pressing member 256.The outer peripheral portion 300 is disposed on the outer periphery of the pressing portion 302. The outer peripheral portion 300 vertically protrudes toward a side opposite to the magnet holder 258 with respect to the pressing portion 302. The outer peripheral portion 300 surrounds the pressing portion 302 along the outer periphery of the pressing portion 302. The outer diameter of the outer peripheral portion 300 is larger than the outer diameter of the magnet holder 258.As shown in FIG. 30, the pressing member 264 is disposed on a side of the magnet holder 262 opposite to the permanent magnet 260. The pressing member 264 has the same structure as the pressing member 256. The pressing member 264 is attached to the shaft 24 in such a manner that the shaft 24 is press-fitted with the through hole of the pressing member 264, and the base portion of the magnet holder 262 makes contact with the pressing portion of the pressing member 264. As a result, each transmission hole 270 passes through the pressing member 264, as well as the yoke 266, the magnet holders 258 and 262, and the pressing member 256.As shown in FIG. 34, the resin layer 254 is disposed on a side of the pressing members 256 and 264 opposite to the permanent magnet 260. The resin layer 254 includes a first resin portion 254 a, a second resin portion 254 b, and a third resin portion 254 c. The first resin portion 254 ais similar to the first resin portions 68 aand 103 a. The second resin portion 254 bis similar to the second resin portions 68 band 103 b. The third resin portion 254 cis the third resin portions 68 cand 103 c. The resin layer 254 is integrally formed to pass through the through hole 270 from a pressing portion 302 side opposite to the permanent magnet 260 to a pressing portion side of the pressing member 264 opposite to the permanent magnet 260. In a modification, the third resin portion 254 cmay be formed in a through hole of the yoke 266. Moreover, the resin layer 254 further includes a fifth resin portion 254 ddisposed in the through hole 304 of the pressing member 256 and the through hole 288 of the magnet holder 258.Next, a method of manufacturing the rotor 250 will be described. First, the shaft 24 is press-fitted with the through hole 266b of the yoke 266. Subsequently, the shaft 24 is press-fitted with the through hole 294 of the magnet holders 258 and 262, and the permanent magnets 260 engage (fit) with the magnet holder 258. In this case, an external force is applied to the magnet holder 258 to deform the beam member 286, whereby the outer peripheral member 284 is moved to be separated from the inner peripheral member 290. As a result, the inner diameter of the cylinder formed by the plurality of circumferential wall portions 282 increases. When the permanent magnets 260 are inserted into the cylinder formed by the plurality of circumferential wall portions 282, an external force applied to the magnet holder 258 is released. Thereby, the elastic deformation of the beam part 286 is released. As a result, the circumferential wall portion 282 presses the permanent magnets 260 in the radial direction of the permanent magnets 260. The same applies to the magnet holder 262. In a state where the magnet holder 258 is attached to the permanent magnet 260, the circumferential direction of the base portion 280 is equal to the circumferential direction of the permanent magnets 260.Further, the shaft 24 is press-fitted with the through holes 306 of the pressing members 256 and 264, and the pressing members 256 and 264 are brought into contact with the respective magnet holders 258 and 262. In this state, the respective regions 252, 256, 258, 260, 262, 264, and 266 are arranged in a mold. Moreover, a resin is injected into the mold to form the resin layer 254. As a result, due to the resin layer 254, the pressing portion 302 of the pressing member 256 presses the base portion 280 of the magnet holder 258 toward the yoke 266. Similarly, due to the resin layer 254, the pressing portion of the pressing member 264 presses the base portion of the magnet holder 262 toward the yoke 266. As a result, it is possible to prevent the base portion 280 of the magnet holders 258 and 262 from being deformed in the direction of the axial line X.(Effect of this Embodiment)In this embodiment, the permanent magnets 260 are supported by magnet holders 258 and 262 in a state where the permanent magnets 260 are restricted from moving relative to the yoke 266. As a result, it is possible to prevent the permanent magnets 260 from being displaced toward the outer side in the radial direction (hereinafter referred to as "second radial direction") of the rotor 250 due to the rotation of the rotor 250. Even if the gap between the rotor 250 and the stator 32 is not increased in consideration of displacement of the permanent magnet 260 toward the outer side in the second radial direction, the motor efficiency of the motor portion 20 does not deteriorate.Before the magnet holder 258 is attached to the permanent magnet 260, the inner diameter of the cylinder formed by the circumferential wall portions 282 is smaller than the outer diameter of the cylinder formed by the plurality of permanent magnets 260. As a result, in a state where the magnet holder 258 is attached to the permanent magnets 260, the magnet holder 258 applies a force directed toward the inner side in the second radial direction to the permanent magnets 260. Consequently, the permanent magnets 260 are suitably prevented from being displaced toward the outer side in the second radial direction. The same applies to the magnet holder 262.Moreover, when the magnet holder 258 is attached to the permanent magnets 260, the beam parts 286 of the base portion 280 are deformed, whereby the inner diameter of the cylinder formed by the plurality of circumferential wall portions 282 increases. Consequently, when the magnet holder 258 is attached to the permanent magnets 260, it is possible to prevent the peripheral wall portion 282 from being inclined toward the outer side of the rotor 250. Consequently, it is not necessary to increase the gap between the rotor 250 and the stator 32 when considering the inclination of the circumferential wall portion 282. Accordingly, the motor efficiency of the motor portion 20 does not deteriorate.The beam parts 286 are connected to respective ends of the outer circumferential part 284 in the circumferential direction. According to this structure, it is possible to stably connect the outer peripheral part 284 to the inner peripheral part 290, compared to a structure in which a beam part is formed in the outer peripheral part 284. The magnet holder 258 can thus stably support the permanent magnets 260. Moreover, when the beam part 286 is deformed such that the outer peripheral part 284 is displaced, the two beam parts 286 connected to an outer peripheral part 284 are balanced, and the outer peripheral part 284 can be suitably displaced to the outer side in the second radial direction (i.e., the first radial direction). The same applies to the magnet holder 262.In a perpendicular cross section, the outer circumferential surfaces 260 aof the permanent magnets 260 which are in contact with the circumferential wall portion 282 are closer to the axial line X than the outer circumferential surfaces 260 bof the permanent magnets 260 by an amount corresponding to the thickness of the magnet holder 258. According to this configuration, the peripheral wall portion 282 is disposed on the same plane as the outer peripheral surfaces 260 aof the permanent magnets 260. Consequently, it is not necessary to increase the clearance between the rotor 250 and the stator 32 in consideration of the thickness of the circumferential wall portion 282. The same applies to the relationship between the magnet holder 262 and the outer circumferential surfaces 260 c. Moreover, the outer circumferential surface 260 amay not be in close proximity to the axial line X by considering the inclination of the circumferential wall portion 282. According to this structure, it is not necessary to increase the gap between a portion of the permanent magnet 260 to which the magnet holders 258 and 262 are attached and the stator 32. As a result, the portions of the permanent magnets 260 to which the magnet holders 258 and 262 are attached can generate a magnetic force for rotating the rotor 250, similarly to the other portions of the permanent magnets 260. Thereby, it is possible to prevent deterioration of the motor efficiency of the motor portion 20.When a force directed to the outer side in the second radial direction is applied to the permanent magnet 260 during the rotation of the rotor 250, a force directed to the outer side in the second radial direction is applied from the permanent magnets 260 to the circumferential wall portions 282 of the magnet holder 258. The resin layer 254, i.e., the fifth resin portion 254 dis inserted into the through hole 304 of the pressing member 256 and the through hole 288 of the magnet holder 258. The beam part 286 of the magnet holder 258 can thus be restricted from being deformed toward the outer side in the second radial direction by the resin layer 254. The same applies to the relationship between the pressing member 264 and the magnet holder 262. In the modification, the pressing member 256 may include a protrusion portion inserted into the through hole or a concave portion formed on the outer peripheral part 284 of the magnet holder 258. According to this configuration, the protrusion portion can prevent the outer peripheral part 284 of the magnet holder 258 from being moved in a direction to be separated from the inner peripheral part 290 during the rotation of the rotor 250 and from being deformed toward the outer side in the second radial direction. The rotor 250 may generally include a restriction portion configured to restrict the outer peripheral part 284 of the magnet holder 258 from being displaced in one direction (a direction separated from the axial line X) to be separated from the inner peripheral part 290 during the rotation of the rotor 250.The outer diameter of the outer peripheral portion 300 of the pressing member 256 is larger than the outer diameter of the magnet holder 258. According to this configuration, by adjusting the outer shape of the outer peripheral portion 300, it is possible to easily adjust the weight balance of the rotor 250.Moreover, according to the outer peripheral portion 300, it is possible to prevent resin from reaching the permanent magnets 260 when the resin layer 254 is formed. As a result, it is possible to prevent the pressure of the resin from being applied to the permanent magnets 260 during the formation of the resin. Consequently, it is possible to prevent the permanent magnets 260 from being damaged during the resin molding. Further, it is possible to prevent the resin from being formed on the outer periphery of the permanent magnets 260. Consequently, it is possible to reduce the clearance between the permanent magnets 260 and the stator 32.In the connection part 281 abetween the circumferential wall portion 282 and the circumferential part 281 (i.e., the outer circumferential part 284), the angle θ between the line connecting one end in the circumferential direction of the connection part 281 aand the center O of the base portion 280 and the line connecting the other end in the circumferential direction of the connection part 281 aand the center O of the base portion 280 is 86°. According to this configuration, it is possible to appropriately prevent the circumferential wall portion 282 from being inclined toward the outer side of the rotor 250 according to the force directed toward the outer side in the second radial direction (i.e., the first radial direction) applied to the circumferential wall portions 282 by the permanent magnets 260 during the rotation of the rotor 250.FIG. 35 shows the calculation results obtained by simulation regarding the amount of displacement of the outer circumferential end on the outer side in the second radial direction (i.e., the first radial direction) of the circumferential wall portion 282 during the rotation of the rotor 250 when the angle θ is changed. The rotational speed of the rotor 250 is 12000 rpm, which is used as the rotational speed of a motor of a conventional fuel pump. The vertical axis of FIG. 35 represents the displacement amount, and the horizontal axis represents the angle θ. As a result, when the angle θ is 40° or greater, it is possible to appropriately prevent the circumferential wall portion 282 from being inclined toward the outer side of the rotor 250. Moreover, when the angle θ is less than 40°, a change in the amount of displacement of the outer circumferential end of the circumferential wall portion 282 with respect to a change in the angle θ is greater than when the angle θ is 40° or greater. When the angle θ is designed to be smaller than 40°, when the actual dimension is reduced by one degree, the displacement amount of the outer circumferential end of the circumferential wall portion 282 becomes significantly larger than the designed displacement amount. On the other hand, when the angle θ is designed 40° or larger, the displacement amount of the outer circumferential end of the circumferential wall portion 282 is not largely changed from the designed displacement amount when the actual dimension is reduced by one degree. Accordingly, when the angle θ is 40° or greater, it is not necessary to increase the clearance between the rotor 250 and the stator 32 when considering the dimensional accuracy.(Modification)In the above-described embodiments, although a plurality of core plates are stacked to form the yoke, the present teaching is not limited to such an embodiment, and a cylindrical rear yoke may be used as an example.Moreover, the magnet holder may be a magnet holder having a shape different from that of the magnet holders 258 and 262. For example, magnet holders 358, 458, 558 and 658 may be used.As shown in FIG. 36, the magnet holder 358 may have a structure in which the shapes of a notch 392 and a beam part 386 of a base portion 380 are different from the shapes of the notch 292 and the beam part 286 of the magnet holder 258. Apart from this, the magnet holder 358 may have the same configurations 381 ( 384 and 388), 382, 390, and 394 as the respective configurations 281 ( 284 and 288), 282, 290, and 294 of the magnet holder 258. The notch 392 may be formed at an intermediate position (specifically, closer to the outer side in the first radial direction than the through hole 388) of a first part 392 bextending in the first radial direction to be connected to a second region 292 aextending in the circumferential direction. The beam part 386 may be formed between the through hole 388 and the notch 392. More specifically, when the beam part 386 is tracked from the inner side in the first radial direction to the outer side, the beam part 386 may extend in the first radial direction between the through hole 388 and the first part 392 band then extend in the circumferential direction between the through hole 388 and the second part 392 a.As shown in FIG. 37, the magnet holder 458 may have a structure in which the shapes of a notch 492, a through hole 488, and a beam part 486 of a base portion 480 are different from the shapes of the notch 292, the through hole 288, and the beam part 286 of the magnet holder 258. Apart from this, the magnet holder 458 may have the same configurations 481 (484), 482, 490 and 494 as the respective configurations 281 (284), 282, 290 and 294 of the magnet holder 258. The notch 492 may have a structure in which the second part 492 ahaving an approximately triangular shape is connected to the inner end in the first radial direction of a first part 492 bextending in the first radial direction. The through hole 488 may be positioned closer to the outer side in the first radial direction than the second part 492 aand may extend in the circumferential direction. Peripheral edges at both ends of the through hole 488 may be formed in a linear shape following the shape of the second part 492 a. The beam member 486 may be formed between the through hole 488 and the notch 492. The beam part 486 may extend in a linear shape inclined with respect to the first radial direction between the through hole 488 and the second part 492 a.As shown in FIG. 38, the magnet holder 558 may have a structure in which the shapes of a notch 592 and a beam part 586 of a base portion 580 are different from the shapes of the notch 292 and the beam part 286 of the magnet holder 258. Apart from this, the magnet holder 558 may have the same configurations 581 (584 and 588), 582, 590 and 594 as the respective configurations 281 (284 and 288), 282, 290 and 294 of the magnet holder 258. The notch 592 may have a structure in which a second part 592 aextending in the circumferential direction is connected to the inner end (specifically, the inner side in the first radial direction more than the through hole 588) in the first radial direction of a first part 592 bextending in the first direction, and a third part 592 cextending in the circumferential direction is connected to an intermediate position (specifically, the outer side in the first radial direction more than the through hole 588) of the first part 592 b. The beam part 586 may be formed between the through hole 588 and the notch 592. More specifically, when the beam part 586 is tracked to the outer side from the inner side in the first radial direction, the beam part 586 may extend in the circumferential direction between the through hole 588 and the second part 592 a, extend in the first radial direction between the through hole 588 and the first part 592 b, and then extend in the circumferential direction between the through hole 588 and the third part 592 c.As shown in FIG. 39, the magnet holder 658 may have a structure in which the configurations of the through holes 688 and 689 and the beam parts 686 and 687 of a base portion 680 are different from the configurations of the through hole 288 and the beam part 286 of the magnet holder 258. Apart from this, the magnet holder 658 may have the same configurations 681( 684), 682, 690, 692, and 694 as the respective configurations 281( 284), 282, 290, 292, and 294 of the magnet holder 258.The through hole 688 may be formed closer to the outer side in the first radial direction than the second part 692 aof the notch 692. Two through holes 688 may be formed in a peripheral part 681. A through hole 689 may be formed between the through holes 688 formed in a peripheral part 681 separate from the two through holes 688. The through hole 689 may have an approximately triangular shape. The beam part 687 may be formed between each through hole 688 and the through hole 689. In the magnet holder 658, the inner peripheral part 690 and an outer peripheral part 684 may be connected to two beam parts 684 and two beam parts 687. The inner peripheral part and the outer peripheral part may be connected by five or more beam parts.In the above embodiment, in the perpendicular cross section, the outer circumferential surface 260 aof the permanent magnet 260 which is in contact with the circumferential wall portion 282 is closer to the axial line X than the outer circumferential surface 260 bof the permanent magnet 260 by an amount corresponding to the thickness of the magnet holder 258. As shown in FIG. 40, in the perpendicular cross section, the outer circumferential surface 260 bof the permanent magnet 260 may be the same distance from the axial line X over an entire range extending from the upper end to the lower end. Alternatively, in the perpendicular cross section, the outer circumferential surface 260 amay be closer to the axial line X than the outer circumferential surface 260 bby an amount equal to or less than the thickness of the magnet holder 258.Moreover, the outer diameter of the pressing member 256 may be the same as the outer diameter of the magnet holder 258.In the above embodiment, a clearance between the rotor 250 and the stator 32 is constant. As shown in FIG. 41, the clearance between the rotor 250 and the stator 32 may be set such that the clearance between the permanent magnet 260 and the stator 32 is smaller than the clearance between the other portion (for example, the magnet holder 258) of the rotor 250 and the stator 32.In the above embodiment, the magnet holder 258 includes four peripheral wall portions 282. However, the magnet holder 258 may include five or more circumferential wall portions, and may include three or less circumferential wall portions. In this modification, the angle θ between the both ends of a connecting part connecting the circumferential wall portion and the outer circumferential part is set to 40° or greater.In the above embodiment, a peripheral wall portion 282 is connected to an outer peripheral part 284. However, a peripheral wall portion 282 may be connected to two or more outer peripheral parts 284. Alternatively, two or more peripheral wall portions 282 may be connected to an outer peripheral portion 284. That is, the number of circumferential wall portions 282 may be different from the number of outer circumferential portions 284.Moreover, although the magnet holders 258 and 262 are engaged with both ends in the direction of the axial line X of the permanent magnet 260, the magnet holders 258 and 262 may be engaged with only one end in the direction of the axial line X of the permanent magnet 260. Moreover, the position of the boundary between the adjacent permanent magnet 260 and the position of the notch 292 may not be identical in the circumferential direction of the permanent magnet 260. For example, the position of the boundary between the adjacent permanent magnet 260 and the position of the notch 292 may be shifted by 45° in the circumferential direction of the permanent magnet 260.In the above embodiment, the resin layer 254 is disposed on a side of the pressing members 256 and 264 opposite to the permanent magnet 260. However, the resin layer 254 may be disposed between the pressing member 256 and the magnet holder 258. Similarly, the resin layer 254 may be disposed between the pressing member 264 and the magnet holder 262.(Seventh Embodiment)A difference from the sixth embodiment will be described. As shown in FIGS. 42 and 43, in the seventh embodiment, the shape of a magnet holder 758 is different from the shape of the magnet holders 258 and 262, and the shape of the pressing member 756 is different from that of the pressing members 256 and 264. Moreover, the shape of a resin layer 754 is different from the shape of the resin layer 254. FIGS. 42 and 43 show a cross section of the resin layer 754 and a cross section of a shaft 752. The other configuration is the same as the configuration of the fuel pump 10 (i.e., the motor portion 20) according to the sixth embodiment. In the following description, the same configurations as those of the fuel pump 10 according to the sixth embodiment are denoted by the same reference numerals as those used in the sixth embodiment.The magnet holder 758 is disposed on the upper and lower surfaces of the yoke 266 and the permanent magnet 260. The magnet holder 758 is formed of a non-magnetic material. As shown in FIG. 42, the magnet holder 758 includes a base portion 780 and a plurality of (four in this embodiment) peripheral wall portions 782. The peripheral wall portion 782 is the same as the peripheral wall portion 782.The base portion 780 has a circular planar shape. The base portion 780 of a magnet holder 768 faces the upper surface of the yoke 266 and the upper surface of the permanent magnet 260. The base portion 780 of the other magnet holder 768 faces the lower surface of the yoke 266 and the lower surface of the permanent magnet 260. The outer diameter of the base portion 780 in a state before being attached to the plurality of permanent magnets 260 is slightly smaller than the outer diameter of a cylinder formed by the outer circumferential surfaces 260 aof the plurality of permanent magnets 260. The base portion 780 includes an inner peripheral part 790 and a plurality of (four in this embodiment) peripheral parts 781.The inner peripheral part 790 has such a ring shape that has the same through hole 794 as the through hole 294 at its central portion. The shaft 752 is press-fitted with the through hole 794. Each transmission hole of the through hole 794 communicates with the transmission hole 270 formed by the shaft 752 and the yoke 266.The plurality of circumferential portions 781 are spaced around the outer periphery of the inner circumferential portion 790. The same notch 792 as the notch 292 is formed between the adjacent circumferential portions 781. Each circumferential part 781 has a pitch circular shape. The inner peripheral part 790 is connected to the inner peripheral edge of each peripheral part 781. A connecting part connected to the peripheral wall portion 782 is formed on the outer peripheral edge of each peripheral part 781. On the inner peripheral side of each peripheral part 781, a beam part 786 is formed on both ends in the circumferential direction of each peripheral part 781. Each peripheral portion 781 thus includes two beam portions 786. Each beam portion 786 is a portion of the base portion 780 that has a smallest width. Each beam portion 786 is a portion of the base portion 780 that has the lowest strength. Each beam part 786 extends obliquely in the first rotational direction (i.e., the radial direction of the base portion 780) with respect to the circumferential direction, and the inner circumferential part 790 is connected to one end of each beam part 786. An outer peripheral portion 784 is connected to the other end of each beam portion 786. The inner peripheral part 790 and the outer peripheral part 784 are thus connected by two beam parts 786. Each of the two beam parts 786 is connected to one end in the circumferential direction of the outer circumferential part 784. A through hole 788 is formed between each of the plurality of outer peripheral parts 784 and the inner peripheral part 790.Each through hole 788 passes through the base portion 780 in a direction from the upper surface to the lower surface (i.e., the through hole 788 passes through both ends in the axial direction of the shaft 752). The through hole 788 is formed between the inner peripheral part 790 and the outer peripheral part 784. The through hole 788 is formed along the outer peripheral part 784 of the beam part 786. In other words, the beam part 786 is formed between the through hole 788 and the notch 792. The through hole 788 is continuously formed without discontinuity to extend from an end of one beam part 786 closer to the outer circumferential part 784 to an end of the other beam part 786 closer to the outer circumferential part 784.The outer peripheral part 784 includes a contact portion 787. The contact portion 787 is formed in such a manner that an edge of the outer peripheral part 784 closer to the inner peripheral part 790 protrudes toward the inner peripheral part 790. The contact portion 787 includes a contact surface 787a formed at the central portion of the through hole 788 to extend in the circumferential direction.Similar to the connection part 281 a, in a connection part between the base portion 780 and the circumferential wall portion 782, in a plane perpendicular to the axial line X, the angle θ between a line connecting one end in the circumferential direction of the connection part and the center O (i.e., the center of the shaft 752) of the base portion 780 and a line connecting the other end in the circumferential direction of the connection part and the center O of the base portion 780 is 86°.When the magnet holder 758 is attached to the permanent magnets 260, the permanent magnet 260 is engaged with a cylinder formed by the plurality of circumferential wall portions 782. In this case, similarly to the magnet holder 758, the beam part 786 having the lowest strength is deformed from the base portion 780, and the outer peripheral part 784 is displaced to be separated from the inner peripheral part 790. As a result, the peripheral wall portion 782 is maintained at a vertical angle with respect to the base portion 780.The pressing member 756 is disposed on a side of the magnet holder 758 opposite to the permanent magnet 260. As shown in FIG. 43, the pressing member 756 includes a pressing portion 702 and an outer peripheral portion 700. The outer peripheral portion 700 has the same structure as the outer peripheral portion 300. The pressing portion 702 has a disc shape. The pressing portion 702 has approximately the same radius as the base portion 780 in a state of being attached to the permanent magnet 260. The pressing portion 702 is attached to the shaft 752 in a state of being in contact with the base portion 780. The same through hole 706 as the through hole 306 is formed at the central portion of the pressing portion 702. The shaft 752 is press-fitted with the through hole 706. Thereby, a transmission hole communicating with the transmission hole 270 is formed in the through hole 706.The pressing portion 702 includes through holes 704 positioned over the through holes 788. Each through hole 704 has an outer shape that follows the outer shape of the corresponding through hole 788. The pressing portion 702 includes contact portions 710 that make contact with a corresponding surface of the contact portions 787 opposite to the permanent magnets 206. According to this configuration, it is possible to prevent the contact regions 787 from being deformed toward the side opposite to the permanent magnets 260.The resin layer 754 (i.e., the first and second resin portions) is disposed on a side of the pressing member 756 opposite to the permanent magnets 260. The resin layer 754 is integrally formed to pass through the through hole 270 from a side facing the permanent magnet 260 of the pressing portion 702 from the pressing member 756 positioned above the rotor 250 to the side facing the permanent magnets 260 of the pressing portion 702 from the pressing member 756 positioned below the rotor 250. Moreover, the resin layer 754 (i.e., the fifth resin region) is disposed in the through hole 704 of the pressing member 756 and the through hole 788 of the magnet holder 758. That is, the resin layer 754 passes through the through hole 788. The contact surface 787 aof the contact portion 787 makes contact with the resin layer 754 positioned closer to the outer peripheral side than the contact surface 787 afrom an inner peripheral side (the shaft side 752). When a force directed toward the outer side in the second radial direction is applied to the permanent magnet 260 during the rotation of the rotor 250, the force directed toward the outer side in the second radial direction is applied from the permanent magnet 260 to the circumferential wall portion 782 of the magnet holder 758. The resin layer 754 is inserted into the through hole 704 of the pressing member 756 and the through hole 788 of the magnet holder 758. Consequently, beam parts 786 of the magnet holder 758 can be prevented from being deformed toward the outer side in the second radial direction by forming contact with the resin layer 754. Further, the entire contact surfaces 787a of the contact regions 787 make contact with the resin layer 754 from the inner peripheral side. Consequently, the outer peripheral parts 784 are reliably restricted from moving toward the outer side in the second radial direction. As a result, it is possible to prevent the beam parts 786 from being deformed toward the outer side in the second radial direction.Moreover, in the seventh embodiment, it is also possible to obtain the same advantages as in the sixth embodiment.(Eighth Embodiment)A difference from the seventh embodiment will be described. As shown in FIG. 44, in the eighth embodiment, the shape of a magnet holder 858 is different from the shape of the magnet holder 758, and the shape of a pressing member 856 is different from the shape of the pressing member 756. Moreover, the shape of a resin layer 854 is different from the shape of the resin layer 754. FIGS. 44 and 45 show a cross section of the resin layer 854 and a cross section of a shaft 852. The arrangement of the magnet holder 858, the pressing member 856, and the resin layer 854 are the same as the arrangement of the magnet holder 758, the pressing member 756, and the resin layer 754. The other configuration is the same as the configuration of the fuel pump 10 (i.e., the motor portion 20) according to the seventh embodiment. In the following description, the same configurations as those of the fuel pump 10 are denoted by the same reference numerals used in the seventh embodiment.As shown in FIG. 44, the magnet holder 858 includes a base portion 880 and a plurality of (four in this embodiment) peripheral wall portions 882. The peripheral wall portion 882 is the same as the peripheral wall portion 782.The base portion 880 has a circular planar shape. The outer diameter of the base portion 880 in a state before being attached to the plurality of permanent magnets 260 is slightly smaller than the outer diameter of a cylinder formed by the outer circumferential surfaces 260 aof the plurality of permanent magnets 260. The base portion 880 includes an inner peripheral part 890 and a plurality (four in this embodiment) of peripheral parts 881.The inner peripheral member 890 has such a ring shape as has the same through hole 894 as the through hole 794 at its central portion. The shaft 852 is press fit with the through hole 894. Each transmission hole of the through hole 894 communicates with a transmission hole 270 formed by the shaft 852 and the yoke 266.The plurality of circumferential parts 881 are spaced around the outer periphery of the inner circumferential part 890. The same notch 892 as the notch 792 is formed between adjacent circumferential portions 881. Each circumferential part 881 has a partial circular shape. The inner peripheral part 890 is connected to the inner peripheral edge of each peripheral part 881. A connecting part connected to the peripheral wall portion 882 is formed on the outer peripheral edge of each peripheral part 881. On an inner peripheral side of each peripheral part 881, a beam part 886 is formed on both ends in the circumferential direction of each peripheral part 881. Each peripheral portion 881 thus includes two beam portions 886. Each beam portion 886 is a region of the base portion 880 having a smallest width. Each beam portion 886 is a portion of the base portion 880 having the lowest strength. Each beam part 886 extends obliquely in the first radial direction (i.e. the radial direction of the base portion 880) in relation to the circumferential direction, and the inner circumferential part 890 is connected to one end of each beam part 886. An outer peripheral portion 884 is connected to the other end of each beam portion 886. The inner peripheral part 890 and the outer peripheral part 884 are thus connected by two beam parts 886. Each of the two beam parts 886 is connected to one end in the circumferential direction of the outer circumferential part 884. A through hole 888 is formed between the plurality of outer peripheral parts 884 and the inner peripheral part 890.The through hole 888 passes through the base portion 880 in a direction from the upper surface to the lower surface (i.e., the through hole 880 passes through both ends in the axial direction of the shaft 852). The through hole 888 is formed between the inner peripheral part 890 and the outer peripheral part 884. The through hole 880 is formed along the outer circumferential portion 884 of the beam portion 886. In other words, the beam part 886 is formed between the through hole 888 and the notch 892. The through hole 888 is continuously formed to extend from an end of one beam part 886 located closer to the outer peripheral part 884 to an end of the other beam part 886 located closer to the outer peripheral part 884.The outer peripheral part 884 includes a through hole 889 passing through the base portion 880 in the direction from the upper surface to the lower surface (i.e., in the axial direction of the shaft 852). The through hole 889 has a triangular shape. The shape of the through hole 889 is not limited to a triangular shape, but may be another shape such as a square shape or a circular shape. The through hole 889 is formed closer to the outer circumferential side than the through hole 888. The outer peripheral part 884 further includes a contact portion 887. The contact portion 887 is formed at an edge closer to the inner circumferential side of the through hole 889. The contact portion 887 is formed between the through hole 888 and the through hole 889. The contact portion 887 is formed to extend over the entire length of the edge that is closer to the inner circumferential side of the through hole 889.Similarly to the respective embodiments described above, in a connection part between the base portion 880 and the peripheral wall portion 882 in a plane perpendicular to the axial line X, the angle θ between a line connecting one end in the peripheral direction of the connection part and the center O (i.e., the center of the shaft 852) of the base portion 880 and a line connecting the other end in the peripheral direction of the connection part and the center O of the base portion 880 is 86°.When the magnet holder 858 is attached to the permanent magnet 260, the permanent magnet 260 engages with a cylinder formed by the plurality of circumferential wall portions 882. In this case, similar to the magnet holder 858, the beam part 886 of the base portion 880 having the lowest strength is deformed, and the outer peripheral part 884 is offset to be separated from the inner peripheral part 890. As a result, the peripheral wall portion 882 is maintained at a vertical angle with respect to the base portion 880.The pressing member 856 is disposed on a side of the magnet holder 858 opposite to the permanent magnet 260. As shown in FIG. 45, the pressing member 856 includes a pressing portion 802 and an outer peripheral portion 800. The outer peripheral portion 800 has the same structure as the outer peripheral portion 700. The pressing portion 802 has a disc shape. The pressing portion 802 has approximately the same radius as the base portion 880 in a state of being attached to the permanent magnet 260. The pressing portion 802 is attached to the shaft 852 in a state of being in contact with the base portion 880. The same through hole 806 as the through hole 706 is formed at the central portion of the pressing portion 802. The shaft 852 is press-fitted with the through hole 806. Thereby, a transmission hole communicating with the transmission hole 270 is formed in the through hole 806.The pressing portion 802 includes a through hole 804 positioned over the through hole 888. The through hole 804 has an outer shape following the outer shape of the through hole 888. The pressing portion 802 further includes a through hole 810 positioned above the through hole 889. The through hole 810 has an outer shape following the outer shape of the through hole 889.The resin layer 854 is disposed on a side of the pressing member 856 opposite to the permanent magnet 260. The resin layer 854 is integrally formed to pass through the through hole 270 from a side facing the permanent magnet 260 of the pressing portion 802 of the pressing member 856 positioned above the rotor 250 to a side facing the permanent magnet 260 of the pressing portion 802 of the pressing member 856 positioned below the rotor 250. Moreover, the resin layer 854 is disposed in the through hole 804 of the pressing member 856 and the through hole 888 of the magnet holder 858, and also in the through hole 810 and the through hole 889. That is, the resin layer 854 passes through the through holes 888 and 889. The contact portion 887 makes contact with the resin layer 854 in the through hole 889 from an inner circumferential side (the shaft 852 side). When a force directed to the outer side in the second radial direction is applied to the permanent magnet 260 during the rotation of the rotor 250, the force directed to the outer side in the second radial direction is applied from the permanent magnet 260 to the circumferential wall portion 882 of the magnet holder 858. The resin layer 854 (i.e., a fifth resin portion) is inserted into the through hole 804 of the pressing member 856 and the through hole 888 of the magnet holder 858. Consequently, the beam part 886 of the magnet holder 858 can be restricted from being deformed toward the outer side in the second radial direction by making contact with the resin layer 854. Further, an entire surface of the contact portion 887 closer to the through hole 889 makes contact with the resin layer 854 from the inner circumferential side. Consequently, the outer peripheral part 884 is reliably restricted from moving toward the outer side in the second radial direction. As a result, it is possible to prevent the beam part 886 from deforming to the outer side in the second radial direction.Moreover, in the eighth embodiment, it is also possible to obtain the same advantages as in the sixth embodiment.(Modification)For example, a plurality of through holes in which the resin layers 754 and 854 (i.e., the fifth resin regions) are disposed may be formed in the outer peripheral parts 784 and 884. For example, at least one through hole in which the resin layer 854 is disposed may be formed in a region of the outer peripheral part 884 that is closer to the outer peripheral side than the through hole 889. In this case, a through hole overlapping the through hole formed in the outer peripheral part 884 may be formed in the pressing member 856. The resin layer 854 (i.e., the fifth resin portion) may pass through both the through hole of the outer peripheral part 881 and the through hole of the pressing member 856.The resin layers 754 and 854 are disposed outside the through hole. For example, the resin layer may be disposed in the notch formed in the outer peripheral parts 784 and 884, for example, a notch extending circumferentially from the notches 792 and 892. In this case, a contact portion may be formed at an edge closer to the inner circumferential side of the notch formed in the outer circumferential parts 784 and 884.

Claims

A brushless motor (20) comprising: a rotor (22, 250); and a stator (32) disposed on an outer periphery of the rotor (22, 250), a pressing member (144b, 146b, 256, 264, 756, 856) fixed on the shaft (24, 752, 852), the rotor (22, 250) including: a shaft (24, 252, 752, 852); a yoke (62, 72, 82, 92, 114, 124, 141, 266) fixed on the shaft (24, 252, 752, 852); a permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260) disposed on an outer periphery of the yoke (62, 72, 82, 92, 114, 124, 141, 266); a first resin portion (68a, 103a, 254a) formed on an ends of the yoke (62, 72, 82, 92, 114, 124, 141, 266) and the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260) is formed in a shaft axis direction and configured to fix the yoke (62, 72, 82, 92, 114, 124, 141, 266) and the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260); and a second resin portion (68b, 103b, 254b) formed at other ends of the yoke (62, 72, 82, 92, 114, 124, 141, 266) and the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94 a, 94 b, 94 c, 94 d, 116, 126, 132, 140, 260) in the shaft axis direction and is configured to fix the yoke (62, 72, 82, 92, 114, 124, 141, 266) and the permanent magnet (64 a, 64 b, 64 c, 64 d, 65 a, 65 b, 65 c, 65 d, 70, 76 a, 76 b, 76 c, 76 d, 80, 86 a, 86 b, 86 c, 86 d, 94 a, 94 b, 94 c, 94 d, 116, 126, 132, 140, 260), wherein a transmission hole (66 a, 74, 270) connecting one end side and another end side in the shaft axis direction extends through the yoke (62, 72, 82, 92, 114, 124, 141, 266) and / or between the shaft (24, 252, 752, 852) and the yoke (62, 72, 82, 92, 114, 124, 141, 141), 266), a third resin portion (68c, 103c, 254c) is formed in the transmission hole (66a, 74, 270), the third resin portion (68c, 103c, 254c) is configured to connect the first resin portion (68a, 103a, 254a) and the second resin portion (68b, 103b, 254b), the first resin portion (68a, 103a, 254a), the second resin portion (68b, 103b, 254b) and the third resin portion (68c, 103c, 254c) integrally, the rotor (22, 250) further includes a magnet holder (100, 102, 110, 118, 120, 142, 154, 160, 258, 262, 358, 458, 558, 658, 758, 768, 858) integrally formed on at least one end of the permanent magnet (64a, 64b, 254c), 64 c, 64 d, 116, 126, 132, 140, 260) is arranged in the shaft axis direction, the magnet holder (100, 102, 110, 118, 120, 142, 154, 160, 258, 262, 358, 458, 558, 658, 758, 768, 858) is configured to regulate the permanent magnet (64 a, 64 b, 64 c, 64 d, 116, 126, 132, 140, 260) with respect to a movement in the shaft axis direction and a circumferential direction of the permanent magnet (64 a, 64 b, 64 c, 64 d, 116, 126, 132, 140, 260), the pressing member (144 b, 146 b, 256, 264, 756, 856) is configured to cause the yoke (141, 266) to contact the magnet holder (142, 154, 160, 258, 262, 358, 458, 558, 658, 758, 768, 858) in the shaft axis direction, and the magnet holder (142, 154, 160, 258, 262, 358, 458, 558, 658, 758, 768, 858) is disposed between the pressing member (144b, 146b, 256, 264, 756, 856) and the permanent magnet (140, 260).The brushless motor (20) according to claim 1, further comprising: a fourth resin portion configured to cover an outer circumferential surface of the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 76a, 76b, 76c, 76d, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260), and the first resin portion (68a, 103a, 254a), the second resin portion (68b, 103b, 254b), the third resin portion (68c, 103c, 254c), and the fourth resin portion are integrally formed.The brushless motor (20) according to claim 1 or 2, wherein the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260) is configured to be divided into a plurality of circumferential-direction regions of the permanent magnet (64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d, 70, 76a, 76b, 76c, 76d, 80, 86a, 86b, 86c, 86d, 94a, 94b, 94c, 94d, 116, 126, 132, 140, 260), the plurality of circumferential-direction regions of the permanent magnet (64a, 64b, 64c, 64d, 65 a, 65 b, 65 c, 65 d, 70, 76 a, 76 b, 76 c, 76 d, 80, 86 a, 86 b, 86 c, 86 d, 94 a, 94 b, 94 c, 94 d, 116, 126, 132, 140, 260) are alternately magnetized in different directions, and in a cross section perpendicular to the shaft axis, at least a part of the transmission hole ( 66 a, 74, 270) is positioned on a line connecting a center of the plurality of regions in the circumferential direction and the shaft axis.The brushless motor (20) according to any one of claims 1 to 3, wherein the yoke (62, 72, 82, 92, 114, 124, 141, 266) includes a through hole (66, 117, 121, 266b) configured to pass through a center of the yoke (62, 72, 82, 92, 114, 124, 141, 266) in the shaft axis direction, and the shaft (24, 252, 752, 852) is press-fitted into the through hole (66, 117, 121, 266b) of the yoke (62, 72, 82, 92, 114, 124, 141, 266).The brushless motor (20) according to any one of claims 1 to 4, wherein the yoke (62, 82, 92, 114, 124, 141, 266) includes a through hole (66, 117, 121, 266b) configured to pass through a center of the yoke (62, 82, 92, 114, 124, 141, 266) in the shaft axis direction, in a cross section perpendicular to the shaft axis, an outer shape of the shaft (24, 252, 752, 852) is a circular shape, and the through hole (66, 117, 121, 266b) of the yoke (62, 82, 92, 114, 124, 141, 266) is a polygonal shape, and the transmission hole (66a, 270) is formed between an outer circumferential surface of the shaft 24, 252, 752, 852) and the through hole (66, 117, 121, 266b) of the yoke (62, 82, 92, 114, 124, 141, 266).The brushless motor (20) according to any one of claims 1 to 5, wherein the permanent magnet (116, 126, 132) includes a plurality of sub-permanent magnets (116, 126a, 126b, 126c, 126d, 132), each of which has a cross section perpendicular to the shaft axis in a circular arc shape, a circumferential position regulating portion (114a) is formed in the yoke (110, 120), and the circumferential position regulating portion (114a) is configured to regulate the position of the sub-permanent magnets (116, 126a, 126b, 126c, 126d, 132) at at least one point of an overall length of the permanent magnet (116, 126, 132) in the shaft axis direction.The brushless motor (20) according to any one of claims 1 to 6, wherein an outer diameter of the pressing member (144b, 146b, 256, 264, 756, 856) is larger than an outer diameter of the permanent magnet (142, 154, 160, 262, 358, 458, 558, 658, 758, 768, 858).The brushless motor (20) according to any one of claims 1 to 7, wherein the pressing member (144b, 146b, 256, 264, 756, 856) is configured to adjust a weight balance of the rotor (22, 250).The brushless motor (20) according to any one of claims 1 to 8, wherein the magnet holder (258, 262, 358, 458, 558, 658, 758, 768, 858) includes: a base portion (280, 380, 480, 580, 680, 780, 880) configured to oppose an end surface of the permanent magnet (260); and a plurality of peripheral wall portions (282, 382, 482, 582, 682, 782, 882) each configured to contact a contact portion (260a) of an outer peripheral surface of the permanent magnet (260) located at the one end of the permanent magnet (260) and extending along a peripheral direction of the permanent magnet (260), and the base portion (280, 380, 480, 580, 680, 780, 880) includes: a plurality of outer peripheral portions (284, 384, 484, 584, 684, 784, 884) configured to connect the plurality of peripheral wall portions (282, 382, 482, 582, 682, 782, 882); an inner circumferential portion (290, 390, 490, 590, 690, 790, 890) configured to be closer to the shaft (24, 252, 752, 852) than the plurality of outer circumferential portions (284, 384, 484, 584, 684, 784, 884) and to surround the shaft (24, 252, 752, 852); A beam portion (286, 386, 486, 586, 686, 687,786, 886) configured to connect the plurality of outer perimeter portions (284, 384, 484, 584, 684, 784, 884) and the inner perimeter portion (290, 390, 490, 590, 690, 790, 890), wherein the beam portion (286, 386, 486, 586, 686, 687,786, 886) is capable of being deformed such that the outer perimeter portions (284, 384, 484, 584, 684, 784, 884) separate from the inner perimeter portion (290, 390, 490, 590, 690, 790, 890).The brushless motor (20) according to claim 9, wherein in the direction perpendicular to the shaft axis, the contact parts (260a) of the outer circumferential surface of the permanent magnet (260) are formed closer to the shaft (24, 252, 752, 852) than other parts of the outer circumferential surface of the permanent magnet (260).The brushless motor (20) according to claim 9 or 10, wherein each of the plurality of circumferential wall portions (282, 382, 482, 582, 682, 782, 882) is connected to the corresponding outer circumferential part (284, 384, 484, 584, 684, 784, 884) at a connection part (281a) extending along the outer circumferential surface of the permanent magnet (260), in a plane perpendicular to the shaft axis, an angle between a line connecting one end of the connection part (281a) and a shaft center and a line connecting another end of the connection part (281a) and the shaft center is equal to or greater than 40 degrees.The brushless motor (20) according to any one of claims 9 to 11, wherein each of the plurality of outer peripheral parts (284, 384, 484, 584, 684, 784, 884) is connected to the inner peripheral part (290, 390, 490, 590, 690, 790, 890) by two or more beam parts (286, 386, 486, 586, 686, 786, 886).The brushless motor (20) according to any one of claims 9 to 12, wherein the rotor (250) further includes a pressing member (256, 264, 756, 856) configured to contact a surface of the base portion (280, 380, 480, 580, 680, 780, 880) on an opposite side to the permanent magnet (260), and press the base portion (280, 380, 480, 580, 680, 780, 880) from the opposite side from the permanent magnet (260) to the permanent magnet (260).The brushless motor (20) according to claim 13, wherein in the direction perpendicular to the shaft axis, an outer diameter of the pressing member (256, 264, 756, 856) is larger than an outer diameter of the permanent magnet (260), and an outer diameter of the magnet holder (258, 262, 358, 458, 558, 658, 758, 768, 858).The brushless motor (20) according to any one of claims 9 to 14, wherein the rotor (250) further includes a fifth resin portion (254b) configured to regulate deformation of the beam part (286, 386, 486, 586, 686, 687, 786, 886).The brushless motor (20) according to claim 15, wherein the base portion (280, 480, 580, 680, 780, 880) in each of the plurality of outer peripheral parts (284, 484, 584, 684, 784, 884) includes a contact hole (288, 488, 588, 688, 788, 888) configured to pass through the base portion (280, 480, 580, 680, 780, 880) in the shaft axis direction at a position circumferentially outside the beam part (286, 486, 586, 686, 687, 786, 886) connected to the outer peripheral part (284, 484, 584, 684, 784, 884), the fifth resin portion (254b) is disposed in the contact hole (288, 488, 588, 688, 788, 888), and each of the plurality of outer peripheral parts (284, 484, 584, 684, 784, 884) includes a contact region configured to contact the fifth resin region (254b) disposed in the contact hole (288, 488, 588, 688, 788, 888, 888) from an inner circumferential side.

Images