CN117220430A - motor - Google Patents

Abstract

A motor, the radial outer side surface of the magnet insertion hole of the rotor core has: a pair of magnet facing surfaces facing the respective end portions of the first magnet and the second magnet; and a pair of peripheral end surfaces extending from the peripheral end portions of the magnet facing surfaces along the outer peripheral surface of the rotor core, satisfying 0.92.ltoreq.RT/ST.ltoreq.0.96. RT: and a center angle of each intersection point between the magnet facing surface and the peripheral end surface. ST: the total number of teeth is divided by the total number of magnetic poles formed by the first magnet and the second magnet to form a corresponding number of magnetic poles, and the center angle between the radially inner ends of the circumferential inner surfaces of the tooth bases on which the coils are mounted is the center angle among the teeth at the circumferential both ends of the teeth of the corresponding number of magnetic poles arranged in the circumferential direction.

Description

Motor

Technical Field

The present invention relates to a motor.

Background

Conventionally, a rotor of a synchronous motor has a plurality of permanent magnets, and the plurality of permanent magnets are inserted into a plurality of magnet insertion holes formed along an outer periphery of the rotor to constitute magnetic poles, respectively. Magnetic flux barriers each including a gap are formed at opposite side ends of the two permanent magnets disposed to face each other. A magnetic circuit portion is formed between these flux barriers. Torque ripple is reduced by optimizing the width of the opposing faces of the magnetic circuit portion.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2015-53778

Disclosure of Invention

When only the width between the flux barriers is optimized as in the synchronous motor described above, the torque ripple during rotation is not sufficiently reduced, and particularly the effect of reducing the cogging torque is weak.

Accordingly, an object of the present invention is to provide a synchronous motor capable of reducing cogging torque without reducing output torque.

An exemplary motor of the present invention has: a shaft extending along a central axis; a rotor fixed to the shaft and rotatable together with the shaft about a central axis; and a stator radially opposite to the rotor. The stator has a plurality of teeth extending radially inward from an annular stator core disposed radially outward of the rotor, and has a tooth base to which a coil is attached. The rotor has: a plurality of magnet pairs arranged in the circumferential direction, each having a first magnet and a second magnet which are arranged so as to be separated from each other in the circumferential direction as facing radially outward; and a rotor core having a plurality of magnet insertion holes into which the pair of the first magnet and the second magnet are inserted. The radially outer surface of the magnet insertion hole has: a pair of magnet facing surfaces that expand in the circumferential direction as they go outward in the radial direction and face ends of the first magnet and the second magnet that are outward in the radial direction; and a pair of peripheral end surfaces extending from circumferential ends of the magnet facing surface along an outer peripheral surface of the rotor core. When viewed in the direction along the central axis, a center angle of each intersection point between the magnet facing surface and the peripheral end surface with the central axis as a center is set as a rotor characteristic value RT, a value obtained by dividing the total number of teeth by the total number of magnetic poles constituted by the first magnet and the second magnet is set as a magnetic pole corresponding number, and a center angle of a radial inner end of a circumferential inner surface of the tooth base portion of two teeth arranged at both ends in the circumferential direction with the magnetic pole corresponding number with the central axis as a center is set as a stator characteristic value ST, 0.92 r/ST is satisfied.

According to the motor of the present invention, the cogging torque is reduced, and the motor can smoothly rotate.

Drawings

Fig. 1 is a perspective view of an exemplary motor of the present invention.

Fig. 2 is an axial view of the exemplary motor of the present invention shown in fig. 1.

Fig. 3 is a partial enlarged view of the exemplary motor of the present invention shown in fig. 2.

Fig. 4 is a graph showing the results of an exemplary experiment 1 of the present invention.

Fig. 5 is a graph showing the results of exemplary experiment 2 of the present invention.

Detailed Description

Hereinafter, a motor for an electric vehicle according to an embodiment of the present invention will be described with reference to the drawings. The scope of the present invention is not limited to the following embodiments, and may be arbitrarily changed within the scope of the technical idea of the present invention.

In this specification, a direction parallel to the central axis Cx of the motor 100 shown in fig. 1 is referred to as an "axial direction". The radial direction orthogonal to the central axis Cx is simply referred to as "radial direction", and the circumferential direction centered on the central axis Cx is simply referred to as "circumferential direction".

In the present specification, the term "annular" includes a shape having one or more slits in a part of the entire region around the central axis Cx, in addition to a shape in which the annular shape is continuously integrally connected to the entire region around the central axis Cx without any gaps.

In addition, in the positional relationship of any one of the azimuth, the line, and the plane with the other, the "parallel" includes not only a state where the two are completely disjoint wherever they are extended, but also a substantially parallel state. In addition, "orthogonal" includes not only a state in which both intersect each other at 90 degrees, but also a substantially perpendicular state and a substantially orthogonal state. That is, the terms "parallel" and "orthogonal" include a state in which the positional relationship of the two is angularly offset to an extent that does not deviate from the gist of the present invention. These are names used for the purpose of illustration only, and are not intended to limit the actual positional relationship, directions, names, and the like.

Motor 100 >

Fig. 1 is a perspective view of an exemplary motor 100 of the present invention. Fig. 2 is an axial view of the exemplary motor 100 of the present invention shown in fig. 1. Fig. 3 is an enlarged view of a portion of the exemplary motor 100 of the present invention shown in fig. 2. As shown in fig. 1 and 2, the motor 100 is an 8-pole 48-slot synchronous motor. That is, the motor 100 has eight poles Mp. In the motor 100, eight magnetic poles Mp are arranged at equal intervals in the circumferential direction.

As shown in fig. 1 and 2, the motor 100 has a shaft 10, a rotor 20, and a stator 30. In the motor 100, the stator 30 is disposed radially outward of the rotor 20. The radially inner end of the stator 30 is radially opposite the radially outer end of the rotor 20. That is, the stator 30 is radially opposite to the rotor 20.

< shaft 10 >)

The shaft 10 extends along a central axis Cx. The shaft 10 has a cylindrical shape and is rotatable about a central axis Cx. The shaft 10 is rotatably supported by a housing (not shown) of the motor 100 via a bearing (not shown).

Rotor 20 >, a motor

The rotor 20 has a cylindrical shape extending in a direction along a central axis Cx extending in the axial direction. In the motor 100 of the present embodiment, the rotor 20 is fixed to the shaft 10 and is rotatable about the central axis Cx together with the shaft 10. The rotor 20 has a rotor core 21 and a plurality of magnet pairs arranged in the circumferential direction. Each magnet pair has a first magnet 22 and a second magnet 23. In the rotor 20, the first magnet 22 and the second magnet 23 of one magnet pair are arranged so as to be separated from each other in the circumferential direction as they face radially outward.

Rotor core 21

The rotor core 21 is formed using a magnetic material. In the present embodiment, the rotor core 21 is a laminated body in which electromagnetic steel plates are laminated in the axial direction. The rotor core 21 has a shaft hole 211 and a plurality of magnet insertion holes 24. The shaft hole 211 is arranged at the center as viewed in the axial direction, and extends in the axial direction. The shaft hole 211 penetrates the rotor core 21 in the axial direction. The shaft 10 is pressed into the shaft hole 211. Thereby, the shaft 10 is fixed to the rotor core 21. The fixation of the shaft 10 and the rotor core 21 is not limited to press fitting, and a method that can be firmly fixed without deteriorating the rotation balance of the shaft 10 and the rotor core 21, such as welding, or screw fixation, can be widely used.

A first magnet 22 and a second magnet 23 are inserted into each of the magnet insertion holes 24.

< first magnet 22 and second magnet 23 >)

The first magnet 22 and the second magnet 23 are both flat plate-like (rectangular parallelepiped) permanent magnets of the same shape. That is, the first magnet 22 and the second magnet 23 have a rectangular parallelepiped shape. One of the first magnet 22 and the second magnet 23 in the thickness direction is an N pole, and the other is an S pole. In the rotor 20, one of the N-pole or S-pole of the first magnet 22 and the second magnet 23 inserted into one magnet insertion hole 24 is disposed radially inward, and the other is disposed radially outward. In the circumferentially adjacent magnet insertion holes 24, the N pole and the S pole are arranged in opposite directions.

The first magnet 22 and the second magnet 23 are fixed to the rotor core 21 by, for example, adhesion. The fixing method is not limited to the bonding method, and a fixing method that can firmly fix the first magnet 22 and the second magnet 23 to the rotor core 21 by pressing other non-magnetic members, insert molding using a resin or the like can be widely used. In addition, a plurality of these fixing methods may be used.

< magnet insertion hole 24 >)

The magnet insertion hole 24 expands in the circumferential direction as seen in the axial direction as it goes radially outward. In the motor 100 of the present embodiment, each of the magnet insertion holes 24 is a hole continuous in the circumferential direction, and the circumferential intermediate portion is V-shaped bent radially inward. The first magnet 22 and the second magnet 23 are disposed along the central axis Cx from the end portion on the axial side of the rotor core 21. By this arrangement, the length of the first magnet 22 in the circumferential direction disposed in the magnet insertion hole 24 is equal to the length of the second magnet 23 in the circumferential direction. By this arrangement, the balance between the magnetic flux from the first magnet 22 and the magnetic flux from the second magnet 23 can be maintained, and cogging torque can be suppressed.

The magnet insertion hole 24 has a radially inner surface 241 and a radially outer surface 242. Radially inner surface 241 and radially outer surface 242 are diametrically opposed. The pair of radially inner surfaces 241 are symmetrical with respect to a plane including a line intersecting the respective planes and the central axis. The pair of radially outer surfaces 242 are also plane-symmetrical with respect to the same plane as the pair of radially inner surfaces 241.

The magnet insertion hole 24 has a pair of first protrusions 243 and second protrusions 244. The pair of first protruding portions 243 are provided at both circumferential ends of the radially inner surface 241, and protrude radially outward. The second convex portion 244 is provided at a circumferential center portion of the radially outer surface 242, and protrudes radially inward.

The pair of radially outer surfaces 242 of the magnet insertion hole 24 has a magnet facing surface 245 and a peripheral end surface 246, respectively. The pair of magnet facing surfaces 245 extend circumferentially outward in the radial direction and face the radially outer end portions of the first magnet 22 and the second magnet 23, respectively. The circumferential length of the magnet facing surface 245 is longer than the circumferential lengths of the first magnet 22 and the second magnet 23. Further, a pair of peripheral end surfaces 246 extend from respective peripheral end portions of the pair of magnet facing surfaces 245 along the outer peripheral surface of the rotor core 21. In the motor 100 of the present embodiment, the pair of magnet facing surfaces 245 are in contact with the first magnet 22 and the second magnet 23, respectively, but may not be in contact.

The first magnet 22 and the second magnet 23 are inserted into the magnet insertion hole 24. At this time, the surfaces of the first magnet 22 and the second magnet 23 disposed on the outer sides in the circumferential direction are in contact with the first convex portion 243. The circumferentially facing surfaces of the first magnet 22 and the second magnet 23 are in contact with the second convex portion 244. In this state, the first magnet 22 and the second magnet 23 are fixed by adhesion.

The fixing of the first magnet 22 and the second magnet 23 is not limited to the bonding, and other methods such as pressing by other members, and insert molding by resin may be employed. In addition, a fixing method capable of firmly fixing the first magnet 22 and the second magnet 23 without breaking the balance when the rotor 20 rotates may be widely used in addition to this. Thereby, when the rotor 20 rotates, the circumferential misalignment of the first magnet 22 and the second magnet 23 is suppressed.

As shown in fig. 3, by inserting and fixing the first magnet 22 and the second magnet 23 into the magnet insertion hole 24, magnetic flux barriers 247 are formed at both ends of the first magnet 22 and the second magnet 23 in the circumferential direction.

More specifically, the first magnetic flux barriers 247a are provided in the magnet insertion holes 24 surrounded by the first circumferential side surface, the magnet facing surface 245, the circumferential side end surface 246, and the first protruding portions 243 of the first magnet 22. A second magnetic flux barrier 247b is provided in the magnet insertion hole 24 surrounded by the other circumferential side surface of the second magnet 23, the magnet facing surface 245, the circumferential side end surface 246, and the first convex portion 243. A third magnetic flux barrier 247c is provided in the magnet insertion hole 24 surrounded by the other circumferential side surface of the first magnet 22, the second convex portion 244, the one circumferential side surface of the second magnet 23, and the radially inner surface 241. By providing the magnetic flux barriers 247, abrupt changes in magnetic flux can be suppressed, and torque fluctuations can be reduced. Therefore, torque pulsation when the rotor 20 rotates is suppressed.

The first magnet 22 and the second magnet 23 are inserted into the magnet insertion hole 24 and fixed, whereby a magnetic pole Mp is formed in the rotor 20. As shown in fig. 1 and 2, the rotor 20 has eight magnet insertion holes 24. That is, in the motor 100 of the present embodiment, the total number of the magnetic poles Mp is eight.

In the motor 100 of the present embodiment, the first magnet 22 and the second magnet 23 are inserted into one magnet insertion hole 24, but the present invention is not limited thereto. The magnet insertion hole may be formed of two independent holes, and the first magnet 22 may be inserted into one hole and the second magnet 23 may be inserted into the other hole. Even in this case, the magnet facing surface and the peripheral side end surface are formed in each hole.

< stator 30 >)

The stator 30 includes a stator core 31, teeth 32, and coils 33 (see fig. 2 and 3). The stator 30 is fixed to a motor housing of the motor 100.

< stator core 31 >

The stator core 31 is formed using a magnetic material. In the present embodiment, the stator core 31 is annular and is a laminated body in which electromagnetic steel plates are laminated in the axial direction, the annular being disposed radially outward of the rotor 20. The stator core 31 has a ring shape around the central axis Cx. The stator core 31 is fixed inside the motor housing.

A plurality of teeth 32 extend radially inward from the stator core 31, and a coil 33 is mounted. The plurality of teeth 32 are circumferentially arrayed. Each tooth 32 has a tooth base 321 and a tooth tip 322. The tooth base 321 is a portion protruding from the stator core 31. In the motor 100 of the present embodiment, the total number of teeth 32 is 48.

An insulator, not shown, is attached to at least the tooth base 321 of the tooth 32. The insulator is formed of a material having electrical insulation such as resin. A wire is wound around the tooth base 321 of each tooth 32 covered with an insulator, and a coil 33 is formed. That is, the teeth 32 have a tooth base 321 to which the coil 33 is mounted. The wire is, for example, an enameled copper wire, a metal wire covered with an insulating member, or the like. By providing the insulator, electric leakage, discharge, and the like from the coil 33 to the teeth 32 can be suppressed.

The tooth tip portion 322 is connected to a radially inner end portion of the tooth base 321 and extends in both circumferential directions. By providing the tooth tip portion 322, the wire can be prevented from being displaced radially inward when the coil 33 is formed by winding the wire around the tooth base 321. The insulator may cover at least a portion of the tooth tip portion 322 that may contact the coil 33.

The coils 33 disposed on the teeth 32 are electrically connected by a jumper wire, not shown. In the present embodiment, the jumper wire is a part of a wire. However, the jumper wire is not limited to this example, and may be a member different from the wire. When a driving current is supplied to each coil 33, the stator 30 is excited. The rotor 20 is rotated (driven) by excitation of the stator 30.

< optimization of Motor 100 >)

The motor 100 has the structure shown above. Depending on the purpose of use, in the motor 100, the rotor 20 is required to rotate as smoothly as possible. In other words, when the rotor 20 rotates, it is required to suppress the rotation of the torque fluctuation (torque ripple). In the motor 100, torque ripple is suppressed by reducing cogging torque.

The inventors of the present invention found that by adjusting the relative shapes of the magnet insertion holes 24 and the teeth 32, the cogging torque was changed. Therefore, in the motor 100, in order to quantitatively show the relationship between the shape of the magnet insertion hole 24 and the tooth 32, the rotor characteristic value RT, the stator characteristic value ST, and the shape factor RT/ST are defined as follows (see fig. 3).

As shown in fig. 3, an intersection between the magnet facing surface 245 and the peripheral end surface 246 is defined as an intersection Cp when viewed from the central axis Cx direction. The intersections Cp of the pair of magnet facing surfaces 245 and the pair of peripheral end surfaces 246 are also circumferentially separated and paired. The rotor characteristic value RT is set as a center angle of the pair of intersection points Cp with the central axis Cx as the center. The rotor characteristic value RT is a region where magnetic fluxes flow in each magnetic pole Mp of the rotor 20.

The total number of teeth 32 is divided by the total number of poles Mp formed by the first magnet 22 and the second magnet 23, and the number of poles Mn is calculated. In the motor 100 of the present embodiment, the total number of teeth 32 is 48, and the total number of poles Mp is 8, so the number of pole correspondences Mn is 6. By setting the total number of teeth 32 to be a multiple of the total number of magnetic poles Mp in this way, the shape factor RT/ST can be easily calculated, and the motor 100 with an optimized shape can be easily manufactured.

Further, the teeth 32 located at both ends in the circumferential direction among the Mn teeth 32 arranged in the circumferential direction are set as end teeth 32a (see fig. 3) as viewed from the central axis Cx direction. The stator characteristic value ST is a center angle centered on the center axis Cx between radially inner ends 321a (see fig. 3) of the circumferential inner surfaces of the tooth bases 321 of the pair of end teeth 32 a. The stator characteristic value ST is a region (angle) in which the magnetic flux in the teeth 32 is received from a region through which the magnetic flux in the magnetic pole Mp of the rotor 20 flows.

The shape factor RT/ST is a variable showing the relationship between the magnet insertion hole 24 and the teeth 32, and is a value obtained by dividing the rotor characteristic value RT by the stator characteristic value ST.

Experiments were performed on the relationship of the form factor RT/ST as defined above to the cogging torque. The experimental details are shown below. In the experiment, a model having different sizes of the respective portions was prepared using the motor 100 as a basic structure, and the cogging torque at the time of the change of the form factor RT/ST was measured in each model. The adjustment of the form factor RT/ST is performed by setting the stator characteristic value ST to a fixed value and changing the rotor characteristic value RT. More specifically, the shape factor RT/ST is adjusted by changing the lengths of the magnet facing surface 245 and the peripheral end surface 246.

Experiment 1 >

First, cogging torque when changing the form factor RT/ST was measured for three kinds of motors 100 having a constant circumferential length L of the first magnet 22 and a constant circumferential length L of the second magnet 23 and different diameters d of the rotor 20.

In experiment 1, three models a, B, and C having different diameters d of the rotor 20 were used. In model a, the diameter d of rotor 20 is 97.4mm. In model B, the diameter d of the rotor 20 is 90mm. In the model C, the diameter d of the rotor 20 is 105mm. In each model, the diameter d and the inner diameter of the stator 30 are determined according to the diameter of the rotor 20. Further, in all the models, the circumferential length L of the first magnet 22 and the second magnet 23 was 9.6mm.

The results of experiment 1 are shown in fig. 4. Fig. 4 is a graph showing the results of experiment 1. Fig. 4 is a graph showing a relationship between a form factor RT/ST and a cogging torque ratio Rc when the diameter of the rotor 20 is changed by setting the circumferential lengths L of the first magnet 22 and the second magnet to be constant. In FIG. 4, the horizontal axis is the form factor RT/ST. The vertical axis is the cogging torque ratio Rc. Here, the cogging torque ratio Rc is a ratio of the cogging torque to the maximum torque in each model. In more detail, the cogging torque ratio Rc is the cogging torque/maximum torque. The results of model a are shown by solid lines, the results of model B are shown by broken lines, and the results of model C are shown by dot-dash lines.

As shown in fig. 4, the cogging torque ratio Rc of each of the models a, B, and C has a minimum value. The shape factor RT/ST, which becomes the minimum value, varies depending on the model, but it is found that the minimum value is approximately between 0.92 and 0.96. According to the results of experiment 1, the cogging torque can be suppressed to be small and the form factor is 0.92.ltoreq.RT/ST.ltoreq.0.96.

The diameter d of the rotor 20 is 90mm or more and 105mm or less. With this configuration, the motor 100 having an optimized shape can be easily manufactured.

Experiment 2 >

Next, for three kinds of motors 100 having a constant diameter d of the rotor 20 and different circumferential lengths L of the first magnet 22 and the second magnet 23, cogging torque when the shape factor RT/ST is changed was measured.

In experiment 2, three models a, D, and E having different circumferential lengths L of the first magnet 22 and the second magnet 23 were used. The model a was 9.6mm in the circumferential direction length L of the first magnet 22 and the second magnet 23, as in the model a of experiment 1. In the model D, the circumferential length L of the first magnet 22 and the second magnet 23 is 9mm. In the model E, the circumferential length L of the first magnet 22 and the second magnet 23 is 10mm. In addition, the diameter d of the rotor 20 was 97.4mm in all the models.

The results of experiment 2 are shown in fig. 5. Fig. 5 is a graph showing the results of experiment 2. Fig. 5 is a graph showing a relationship between a form factor RT/ST and a cogging torque ratio Rc when the diameter of the rotor 20 is fixed and the circumferential lengths L of the first magnet 22 and the second magnet 23 are changed. In FIG. 5, the horizontal axis is the form factor RT/ST. The vertical axis is the cogging torque ratio Rc. Here, the cogging torque ratio Rc is the same as fig. 4. The results of model a are shown by solid lines, model D by dotted lines, and model C by two-dot chain lines.

As shown in fig. 5, the cogging torque ratio Rc of each of the models a, D, and E has a minimum value. The shape factor RT/ST, which becomes the minimum value, varies depending on the model, but it is found that the minimum value is approximately between 0.92 and 0.96. According to the results of experiment 1, the cogging torque can be suppressed to be small and the form factor is 0.92.ltoreq.RT/ST.ltoreq.0.96.

The first magnet 22 and the second magnet 23 inserted into the magnet insertion hole 24 have a circumferential length L of 9mm to 10mm.

As described above, according to experiment 1 and experiment 2, in the motor 100 of the present embodiment, the cogging torque can be suppressed to be small when 0.92 r/ST is equal to or smaller than 0.96, regardless of the diameter d of the rotor 20 and the circumferential lengths L of the first magnet 22 and the second magnet 23.

That is, in the motor 100 of the present embodiment, when viewed in the direction along the central axis Cx, the rotor characteristic value RT is the center angle around the central axis Cx of each intersection point between the magnet facing surface 245 and the peripheral end surface 246, the value obtained by dividing the total number of teeth 32 by the total number of magnetic poles Mp formed by the first magnet 22 and the second magnet 23 is the magnetic pole correspondence number Mn, and the stator characteristic value ST is the center angle around the central axis Cx of the radially inner ends 321a of the inner surfaces in the circumferential direction of the tooth bases 321 of the two end teeth 32a arranged at both ends of the magnetic pole correspondence number Mn in the circumferential direction, which is 0.92 r/ST is equal to or less than 0.96.

In the motor 100, torque ripple during rotation of the rotor 20 can be suppressed by suppressing the cogging torque to be small, and the rotor 20 can be smoothly rotated. Thereby, vibration and noise can be reduced. Further, by suppressing the cogging torque to be small, the torque required at the time of starting the motor 100 can be suppressed. This can suppress the electric power required for starting.

< summary >

The motor 100 of the present invention has the following structure.

(1) A motor has a shaft extending along a central axis, a rotor fixed to the shaft and rotatable together with the shaft about the central axis, and a stator radially opposed to the rotor.

The stator has a plurality of teeth extending radially inward from an annular stator core disposed radially outward of the rotor, and has a tooth base to which a coil is attached.

The rotor has:

a plurality of magnet pairs arranged in the circumferential direction, each of the plurality of magnet pairs having a first magnet and a second magnet which are arranged so as to be separated from each other in the circumferential direction as the plurality of magnet pairs face radially outward; and

and a rotor core having a plurality of magnet insertion holes into which the pair of the first magnet and the second magnet are inserted.

The radially outer surface of the magnet insertion hole has:

a pair of magnet facing surfaces that expand in a circumferential direction as they go outward in the radial direction and face ends of the first magnet and the second magnet that are outward in the radial direction; and

and a pair of peripheral end surfaces extending from peripheral ends of the magnet facing surfaces along an outer peripheral surface of the rotor core.

When viewed in a direction along the central axis, a central angle of each intersection point between the magnet facing surface and the peripheral end surface with the central axis as a center is set as a rotor characteristic value RT,

the value obtained by dividing the total number of teeth by the total number of magnetic poles formed by the first magnet and the second magnet is set as a magnetic pole corresponding number, and when a center angle of a radial inner end of a circumferential inner surface of the tooth base portion of two teeth arranged at both ends of the magnetic pole corresponding number in the circumferential direction, which is centered on the center axis, is set as a stator characteristic value ST, 0.92-RT/ST-0.96 is satisfied.

(2) The motor according to (1), wherein the total number of teeth is 48 and the total number of poles is 8.

(3) The motor according to (1) or (2), wherein the first magnet and the second magnet have a rectangular parallelepiped shape having the same shape, and a length in a circumferential direction of the first magnet and a length in a circumferential direction of the second magnet inserted into the magnet insertion hole are 9mm or more and 10mm or less.

(4) The motor according to any one of (1) to (3), wherein a circumferential length of the first magnet inserted into the magnet insertion hole is equal to a circumferential length of the second magnet.

(5) The motor according to any one of (1) to (4), wherein a diameter of the rotor is 90mm or more and 105mm or less.

While the embodiments of the present invention have been described above, the structures and combinations thereof in the embodiments are examples, and the structures may be added, omitted, substituted, and other modified without departing from the spirit of the present invention. The present invention is not limited to the embodiments.

Industrial applicability

The structure of the present invention can be used as an electric motor.

Symbol description

100 motor

Mp magnetic pole

10-axis

20 rotor

21 rotor core

211 shaft hole

22 first magnet

23 second magnet

24 magnet insertion hole

241 radially inner surface

242 radially outer surface

243 first convex part

244 second protrusion

245 magnet facing surface

246 peripheral side end face

247 magnetic flux barrier

30 stator

31 stator core

32 teeth

321 tooth base

322 tooth front end

32a end teeth

321a radial inner end

33 coils.

Claims (5)

1. A motor, comprising:

a shaft extending along a central axis;

a rotor fixed to the shaft and rotatable together with the shaft about a central axis; and

a stator radially opposed to the rotor,

the stator has a plurality of teeth extending radially inward from an annular stator core disposed radially outward of the rotor and having a tooth base on which a coil is mounted,

the rotor has:

a plurality of magnet pairs arranged in a circumferential direction, the plurality of magnet pairs having a first magnet and a second magnet which are arranged so as to be separated in the circumferential direction as going radially outward; and

a rotor core having a plurality of magnet insertion holes into which the pair of the first magnet and the second magnet are inserted,

the radially outer surface of the magnet insertion hole has:

a pair of magnet facing surfaces that expand in a circumferential direction as they go outward in the radial direction and face ends of the first magnet and the second magnet that are outward in the radial direction; and

a pair of peripheral end surfaces extending from circumferential end portions of the magnet facing surfaces along an outer peripheral surface of the rotor core,

when viewed in a direction along the central axis, a central angle of each intersection point between the magnet facing surface and the peripheral end surface with the central axis as a center is set as a rotor characteristic value RT,

when a value obtained by dividing the total number of teeth by the total number of magnetic poles formed by the first magnet and the second magnet is set as a magnetic pole corresponding number, and a center angle of a radial inner end of a circumferential inner surface of the tooth base portion of two teeth arranged at both ends of the magnetic pole corresponding number in a circumferential direction, which is centered on the center axis, is set as a stator characteristic value ST,

meets the requirement of RT/ST of 0.92-0.96.

2. The motor according to claim 1, wherein,

the total number of teeth is 48,

the total number of poles is 8.

3. A motor according to claim 1 or 2, wherein,

the first magnet and the second magnet are in a cuboid shape with the same shape,

the length of the first magnet in the circumferential direction and the length of the second magnet in the circumferential direction inserted into the magnet insertion hole are 9mm to 10mm.

4. The motor according to claim 3, wherein,

the length of the first magnet in the circumferential direction inserted into the magnet insertion hole is equal to the length of the second magnet in the circumferential direction.

5. A motor according to claim 1 or 2, wherein,

the diameter of the rotor is more than 90mm and less than 105mm.