JP2013192359A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cogging torque and torque ripple with good balance while enhancing the output of a synchronous reluctance motor, and to manufacture a stator by press.SOLUTION: Output is enhanced by arranging a magnet 26 on the rotor 3 of a brushless motor 1 of synchronous reluctance motor type, and using the magnetic force of the magnet 26 supplementally. A bridge 14 for interconnecting the inner peripheral side tips of adjoining teeth 13 is provided in the stator core 5. Radial thickness W of the bridge 14 is set to satisfy a relation t≤W≤1.5 mm, where t is the thickness of a steel sheet composing the stator core 5, thus reducing the cogging torque, and suppressing the torque ripple rate 5% or lower.

Description

  The present invention relates to a brushless motor, and more particularly to a synchronous (synchronous) reluctance motor using reluctance torque generated in a rotor.

  2. Description of the Related Art Conventionally, a reluctance motor is known as a type of electric motor that generates a rotational force by utilizing a magnetic resistance difference between a stator and a rotor. Such a reluctance motor includes a synchronous reluctance motor having a structure similar to that of an AC motor and a switched reluctance motor having a structure similar to that of a VR type stepping motor. Among these reluctance motors, the synchronous reluctance motor is configured to supply a multi-phase (usually three-phase) sinusoidal current to the stator and to drive the rotor using reluctance torque generated by magnetic saliency. ing.

  On the other hand, since such a synchronous reluctance motor rotates a rotor by the reluctance torque which arises by a magnetic resistance difference, there exists a tendency for output torque to become small compared with the motor using a magnet. For this reason, in order to obtain a desired torque, there has been a problem that the motor size becomes large. Therefore, the present inventors have set up a reluctance torque type magnet in which the basic configuration is a reluctance motor, and a magnet is arranged on the rotor, so that the magnetic force of the magnet is used as an auxiliary to achieve both improvement in output and miniaturization of the motor. Auxiliary motor was studied and developed.

JP 2009-33925 A

  However, the above-described reluctance torque type magnet auxiliary motor has a problem that cogging, which was not found in a reluctance motor, occurs with the use of a magnet. In particular, in a motor used in an electric power steering apparatus, the return of the steering wheel is deteriorated by cogging, so it is necessary to suppress cogging to a small extent, and countermeasures are urgently required.

  In addition, torque ripple, which is torque fluctuation at the time of energization, has a problem that, for example, in a motor for an electric power steering apparatus, the steering feeling is deteriorated and the driver feels uncomfortable. Torque ripple is also a problem in ordinary reluctance motors. For example, in Patent Document 1, as a countermeasure, a stator around which a winding is wound is formed of an inner stator and an outer stator, and a tooth tip side (rotor A synchronous reluctance motor is described in which the inner peripheral side of the inner stator, that is, the tooth tip side is closed in order to ensure the roundness of the housing portion.

  However, according to the experiments by the inventors, in the reluctance torque type magnet auxiliary motor, when the inner peripheral wall of the inner stator becomes thin, the cogging torque and the torque ripple increase on the contrary. There was a problem that the operability of the steering wheel became worse. In addition, the stator is generally manufactured by laminating a plurality of thin steel plates. However, when the inner peripheral wall is as thin as 0.1 to 0.3 mm as in Patent Document 1, the stator is laminated. It is difficult to punch the steel plate with a press, and Patent Document 1 does not mention a method for manufacturing the steel plate. When the thickness of the inner peripheral wall is as thin as 0.1 to 0.3 mm, it is necessary to use a costly processing method such as cutting by post-processing in order to manufacture a laminated steel sheet of the stator, and the product cost is high. There was also a problem of increasing.

  An object of the present invention is to reduce cogging torque and torque ripple in a balanced manner while improving the output in a brushless motor, particularly a synchronous reluctance motor. Another object of the present invention is to enable stator production by press working and to reduce product costs.

  The brushless motor of the present invention includes a hollow motor case, a stator fixed in the motor case, and a rotor that is disposed on the inner peripheral side of the stator and is rotatably supported by the motor case. A brushless motor, wherein the rotor includes a plurality of flux barriers penetrating the rotor in the axial direction, a magnet is disposed in the flux barrier, and the stator is a thin plate formed by press working A plurality of teeth portions that are formed by laminating a plurality of steel plates and radially arranged in the radial direction, and a bridge portion that connects the inner peripheral side tip portions of the adjacent tooth portions provided on the inner peripheral side of the teeth portion. Where W is the thickness in the radial direction of the bridge portion, and W is not less than the thickness t of the steel plate constituting the stator and not more than 1.5 mm (t ≦ W ≦ 1.5 mm).

  In the present invention, in a reluctance motor type brushless motor, by arranging a magnet in the rotor, the magnetic force of the magnet is used as an auxiliary to achieve both improvement in output and miniaturization of the motor. In the brushless motor, a bridge portion is provided to connect the inner peripheral side tip portions of the teeth portion formed on the stator, and the radial thickness W of the bridge portion is determined by the plate thickness t ≦ W ≦ 1 of the steel plate constituting the stator. By setting it to 5 mm, the maximum torque becomes larger than that of a synchronous reluctance motor without a magnet, and torque ripple can be reduced while minimizing the occurrence of cogging associated with the use of a magnet.

  In the brushless motor, the radial thickness W of the bridge portion is set to be equal to or greater than a plate thickness t of the steel plate that can punch the steel plate constituting the stator with a press, and the torque ripple rate of the brushless motor is 5%. You may set to 1.5 mm or less so that it may be suppressed below. Thereby, the specification (torque ripple rate of 5% or less) required for the motor for the electric power steering apparatus can be satisfied, and the present invention can be used as a drive source of the electric power steering apparatus.

  The stator may be provided with an inner stator disposed on the inner peripheral side and an outer stator disposed on the outer peripheral side, and the teeth portion and the bridge portion may be provided on the inner stator.

  In addition, a plurality of recesses are formed on the inner peripheral surface of the outer stator, and the outer peripheral side front end portion of the tooth portion is fitted into the recess, so that the outer stator and the inner stator are connected to the recess. By inserting and fitting the outer peripheral side distal end portion, it may be fixed in a state of being prevented from coming off in the radial direction and the circumferential direction. As a result, it is possible to reliably prevent displacement of the inner stator with respect to the force in the rotational direction, as compared with the coupling simply by press-fitting. In this case, the concave portion may be formed in a dovetail shape having a cross-section of an inverted C shape, and a tenon-like fitting portion whose outer end side is enlarged may be formed at the outer peripheral side tip portion of the tooth portion. .

  On the other hand, a coil may be formed by winding a copper wire around the teeth portion with distributed winding, thereby reducing leakage of magnetic flux at the bridge portion compared to concentrated winding, and concentrated winding. The maximum torque can be made larger than in the case of.

  According to the brushless motor of the present invention, by arranging a magnet in the rotor, the magnetic force of the magnet can be used supplementarily, and the maximum torque can be increased as compared with a synchronous reluctance motor without a magnet. In addition, a bridge portion is provided to connect the inner peripheral side tip portions of the teeth portion formed on the stator, and the radial thickness W of the bridge portion is set to a plate thickness t ≦ W ≦ 1.5 mm of the steel plate constituting the stator. As a result, torque ripple can be reduced while minimizing the occurrence of cogging associated with the use of the magnet. Therefore, when the brushless motor is used in an electric power steering apparatus, the returnability of the steering wheel is improved by reducing cogging, and the operability of the steering wheel is improved by reducing torque ripple. Furthermore, by making W equal to or greater than the plate thickness t, each steel plate of the stator core made of laminated steel plates can be manufactured only by pressing, so that the manufacturing cost can be reduced and an inexpensive motor can be provided.

1 is a cross-sectional view of a brushless motor 1 (hereinafter abbreviated as a motor 1) that is an embodiment of the present invention. It is sectional drawing along the AA line of FIG. It is explanatory drawing which shows the structure of a bridge part. It is explanatory drawing which shows the structure of the fitting fixing | fixed part of an outer stator and an inner stator. It is the graph which showed the relationship between the width W of a bridge | bridging part, and a cogging torque about each case where the plate | board thickness of the laminated steel plate which forms a stator core is 0.35 mm and 0.5 mm. It is the graph which showed the relationship between the width W of a bridge | bridging part and cogging torque when changing the amount of magnetic flux (when changing the strength of a magnet) (plate thickness = 0.5 mm). It is the graph which showed the relationship between the width W of a bridge | bridging part, and output torque (plate thickness of a steel plate = 0.35 mm, 0.5 mm). It is the graph which showed the relationship between the width W of a bridge | bridging part and output torque when changing the amount of magnetic flux (plate thickness = 0.5 mm). It is the graph which showed the relationship between the width W of a bridge | bridging part, and a torque ripple (plate thickness of a steel plate = 0.35 mm, 0.5 mm). It is the graph which showed the relationship between the width W of a bridge | bridging part, and a torque ripple at the time of changing the amount of magnetic flux (plate thickness = 0.5 mm).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a brushless motor 1 (hereinafter abbreviated as “motor 1”) according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG. The motor 1 is a reluctance torque type magnet auxiliary motor that uses the magnet's magnetic force by arranging a magnet on the rotor while being based on a reluctance motor, and is used as a drive source for an electric power steering device. The As shown in FIG. 1, the motor 1 is an inner rotor type brushless motor in which a stator (stator) 2 is disposed on the outside and a rotor (rotor) 3 is disposed on the inside, similarly to a normal reluctance motor.

  The stator 2 includes a bottomed cylindrical motor case 4, a stator core 5, a stator coil 6 (hereinafter abbreviated as a coil 6) wound around the stator core 5, and a bus bar unit (terminal unit) 7 attached to the stator core 5. It is composed of The motor case 4 is formed in a bottomed cylindrical shape with iron or the like, and an aluminum die-cast bracket 8 is attached to an opening of the motor case 4 with a fixing screw (not shown). The stator core 5 is press-fitted and fixed to the inner peripheral surface of the motor case 4 after winding the coil 6. The motor 1 employs a so-called outer winding in which a coil 6 is arranged on a stator 2 that is an outer member, and the space factor of the winding can be made larger than the configuration in which the coil is wound around the inner member, and the output of the motor Improvement is achieved.

  As shown in FIG. 2, the stator core 5 includes a cylindrical outer stator 11 and an inner stator 12 attached to the inner peripheral side of the outer stator 11. The outer stator 11 and the inner stator 12 are each formed by laminating electromagnetic steel plates having a thickness t (t = 0.35 to 0.70 mm). The inner stator 12 includes a radially formed tooth portion 13 and a bridge portion 14 that connects the inner peripheral sides of the tooth portion 13, and a slot 15 is formed between adjacent tooth portions 13. . As shown in FIG. 3, in the motor 1, the radial width W of the bridge portion 14 is set in a range of a thickness t ≦ W ≦ 1.5 mm of one steel plate on which the stator core 5 is laminated.

  Thus, in the motor 1, since the inner peripheral side of the teeth part 13 is connected by the bridge part 14, it is possible to wind a coil around the teeth using a slit on the tooth tip side as in a normal motor. Can not. Therefore, in the motor 1 as well, as in Patent Document 1, the stator 2 is divided into an outer stator 11 and an inner stator 12, and the teeth portion 13 of the inner stator 12 is opened so that a copper wire is connected to the teeth portion 13. The coil 6 can be formed by winding. After the coil 6 is wound by distributed winding, the teeth portion 13 is attached to the inner peripheral side of the outer stator 11 (fitting and fixing). As a result, the stator core 5 having the coil 6 accommodated in the slot 15 is formed. The distributed winding has less leakage of magnetic flux at the bridge portion 14 than the concentrated winding, and the maximum torque can be increased as compared with the concentrated winding. Therefore, in the motor 1, the coil 6 is wound with the distributed winding. .

  FIG. 4 is an explanatory diagram showing a configuration of a fitting and fixing portion between the outer stator 11 and the inner stator 12. In the motor 1, 24 tooth portions 13 are provided, and each tooth portion 13 is fitted and fixed to a tooth mounting groove (concave portion) 16 formed on the inner peripheral surface of the outer stator 11. As shown in FIG. 4, a dovetail-shaped tooth mounting groove 16 having a cross-section of an inverted C shape is formed on the outer stator 11 side. The teeth mounting groove 16 extends along the axial direction over the entire length of the outer stator 11. On the other hand, a tenon-like fitting portion 17 whose outer end side is enlarged is formed at the outer peripheral end of the tooth portion 13.

  The outer stator 11 and the inner stator 12 are fixed in a state where they are prevented from coming off in the radial direction and the circumferential direction by inserting and fitting the tooth mounting grooves 16 and the fitting portions 17 from the axial direction. Thereby, the movement to the rotation direction of the inner stator 12 is controlled, and the position shift of the inner stator 12 with respect to the force in the rotation direction can be reliably prevented. In Patent Document 1, the inner stator is press-fitted and fixed to the outer stator after winding the winding around each tooth.

  A bus bar unit 7 is attached to one end side of the stator core 5. The bus bar unit 7 has a structure in which a copper bus bar is insert-molded in a synthetic resin main body. Around the bus bar unit 7, a plurality of power supply terminals 21 protrude in the radial direction. When the bus bar unit 7 is attached, the power feeding terminal 21 is welded to the end 6 a of the coil 6 drawn from the stator core 5. In the bus bar unit 7, the number of bus bars corresponding to the number of phases of the motor 1 (here, three for the U phase, V phase, and W phase) is provided. Each coil 6 is electrically connected to a power supply terminal 21 corresponding to the phase. The stator core 5 is press-fitted and fixed in the motor case 4 after the bus bar unit 7 is attached.

  A rotor 3 is inserted inside the stator 2. The rotor 3 has a rotor shaft 22, and the rotor shaft 22 is rotatably supported by bearings 23a and 23b. The bearing 23 a is fixed to the center of the bottom 4 a of the motor case 4, and 23 b is fixed to the center of the bracket 8. A cylindrical rotor core 24 and a rotor (resolver rotor) 32 of a resolver 31 serving as a rotation angle detection unit are attached to the rotor shaft 22.

  A cover 33 is attached to the outside of the bottom 4a of the motor case 4 (on the right side in FIG. 1). The rotor shaft 22 extends from the bottom 4a of the motor case 4 into the cover 33, and a resolver rotor 32 is attached to the tip of the rotor shaft 22. Control boards 34 and 35 are accommodated in the cover 33, and a power system element 36 and a control system element 37 are mounted on the control board 34 and the control board 35, respectively. A resolver stator 38 is attached to the control board 35 so as to face the outer peripheral side of the rotor of the resolver 31, and a signal wire of a rotation angle detection coil provided on the resolver stator 38 is electrically connected to the control system element 37. It is connected.

  The rotor core 24 forming the rotor 3 is also formed by laminating a large number of disk-shaped electromagnetic steel plates. The steel plate constituting the rotor core 24 is provided with a plurality of slits 25 as flux barriers for varying the magnetic resistance of the rotor 3 along the rotation direction. The slit 25 is bent in an arc shape, and the inside of the slit 25 is a space. The slits 25 are radially arranged around the q axis that is mechanically inclined 45 degrees with the d axis orthogonal to the rotor shaft 22 as a boundary. In the motor 1, four sets of a plurality of slits 25 centering on the q axis are provided in a radial manner, and a plurality of layers of magnetic paths are formed in each set.

  Here, in a normal reluctance motor, the slit 25 is used as a gap in order to change the magnetic resistance of the rotor 3. However, in the motor 1 according to the present invention, a magnet (permanent magnet) is provided in the slit 25 to improve the output. 26 is arranged. In this case, in the motor 1, since the reluctance torque is the main and the magnet torque is the auxiliary, the magnet 26 may be an inexpensive ferrite magnet. However, a rare earth magnet such as a neodymium bond magnet may be used for the magnet 26 in order to further increase the output.

  On the other hand, in a reluctance motor that does not use a magnet, excitation poles are short-cut, and therefore, a configuration that connects teeth tips is generally not employed. In that respect, Patent Document 1 closes the stator inner peripheral side in order to ensure the roundness of the rotor accommodating portion in order to reduce torque ripple, but this also reduces the thickness of the inner peripheral wall to minimize magnetic flux leakage. The thickness is suppressed to 0.1 to 0.3 mm. Moreover, in patent document 1, the structure whose thickness of an inner peripheral wall exceeds 0.6 mm is not considered. On the other hand, in the motor 1 of the present invention, the reluctance torque efficiency is reduced by using a magnet, and it is intended to increase the output by obtaining a torque equal to or more than the amount of the drop by the magnet. As described above, cogging occurs with the use of a magnet.

  Therefore, in order to reduce cogging, the motor 1 is provided with the bridge portion 14 by connecting the inner peripheral side tip portions of the adjacent tooth portions 13. In consideration of the cost, the stator core 5 including the bridge portion 14 is also included. Is preferably formed by stamping and forming thin steel plates and then laminating them. Accordingly, the inventors consider the best balance of the width W of the bridge portion 14 in consideration of the balance between the assist of the output torque by the magnet and the cogging torque, the magnitude of torque ripple, press workability, and the like. The possible range was examined.

  FIG. 5 is a graph showing the relationship between the width W of the bridge portion 14 and the cogging torque when the thickness of each steel plate of the stator core 5 made of laminated steel plates is 0.35 mm and 0.5 mm. FIG. 6 is a graph showing the relationship between the width W of the bridge portion and the cogging torque when the amount of magnetic flux is changed (when the strength of the magnet is changed) (plate thickness = 0.5 mm). . Note that 0 on the X-axis on the graph indicates a state where the bridge portion 14 does not exist, that is, a case where the inner peripheral end of the teeth portion 13 is opened in a slit shape and is not a closed stator.

  As shown in FIG. 5, if the width W of the bridge portion 14 is small, the cogging torque becomes very large. Conversely, if the bridge portion 14 is provided and the stator core 5 is a closed stator, the cogging is dramatically reduced. In addition, the change of cogging generally becomes smaller from the extent of exceeding the plate thickness. This is thought to be due to the fact that magnetic flux flows through the bridge portion 14, so that the change in magnetic flux (switching of magnetic flux) associated with the rotation of the rotor is alleviated. Expected to be killed. That is, by closing the inner peripheral side of the stator 2 with the bridge portion 14, the magnetic flux by the magnet 26 is short-circuited, the change in magnetic flux is suppressed, and cogging is reduced. As shown in FIG. 6, this tendency is the same even when the amount of magnetic flux is changed, and it has been found that the width W of the bridge portion 14 is preferably equal to or greater than the plate thickness in order to reduce cogging.

  Next, the output torque in the motor 1 will be examined with reference to FIGS. FIG. 7 is a graph showing the relationship between the width W of the bridge portion 14 and the output torque (steel plate thickness = 0.35 mm, 0.5 mm), and FIG. 8 shows the bridge portion when the amount of magnetic flux is changed. It is the graph which showed the relationship between the width W of this and an output torque (plate | board thickness = 0.5 mm). As shown in FIGS. 7 and 8, the output torque has an inflection point in the vicinity of W = 1.5 mm regardless of the plate thickness, and when the width W exceeds 1.5 mm, the output torque suddenly drops. This phenomenon was the same even when the amount of magnetic flux was changed. This is because when the width W is thin, magnetic flux saturation occurs and the leakage of magnetic flux decreases, and the torque is difficult to decrease. However, when the width W exceeds 1.5 mm, the magnetic flux easily goes around the bridge portion 14 and the leakage of magnetic flux increases. It is considered that the effective magnetic flux decreases. Accordingly, from the viewpoint of output torque, the smaller the width W is 1.5 mm or less, the better.

  Further, torque ripple in the motor 1 will be examined with reference to FIGS. FIG. 9 is a graph showing the relationship between the width W of the bridge portion 14 and torque ripple (steel plate thickness = 0.35 mm, 0.5 mm), and FIG. 10 shows the bridge portion when the amount of magnetic flux is changed. Is a graph showing the relationship between the width W and the torque ripple (plate thickness = 0.5 mm). As shown in FIGS. 9 and 10, the torque ripple decreases as the width W increases from zero, but the torque ripple gradually increases as the width becomes thicker than the width W = 1 mm. The phenomenon in which the torque ripple changes from decreasing to increasing as the width W changes varies slightly depending on the plate thickness, but occurs approximately in the vicinity of the width W = 1 mm. Such a phenomenon in which the torque ripple graph is concave occurs similarly even if the magnetic flux changes, and both take a local minimum value around 1 mm.

  Regarding the torque ripple, in the portion before the minimum value, if the width W is small, the magnetic flux is saturated at the bridge portion 14, so that the polarity is suddenly switched greatly from N saturated state to S saturated state due to switching of the magnetic poles. Ripple is thought to increase. For this reason, when the magnetic flux leaks to some extent, the magnetic flux change becomes smoother and the torque ripple decreases, and the torque ripple decreases as the width W increases. On the other hand, when the width W increases and the leakage of magnetic flux increases, the induced voltage waveform is disturbed, and the sine wave waveform is distorted. For this reason, although the change of magnetic flux is small, torque ripple increases due to disturbance of the induced voltage waveform. However, if the width W is 2 mm or more, the magnetic flux does not change due to the leakage of the magnetic flux, and the torque ripple is stabilized at less than 6%.

  From the above points, the torque ripple becomes a minimum value in the vicinity of the width W = 1 mm where they balance. Therefore, in order to satisfy the specification of “torque ripple 5% or less” required as a motor for electric power steering, the width W is 0.35 to 1.7 mm at a plate thickness of 0.35 mm, and the plate thickness is 0.5 mm. Then, about 0.5 to 1.8 mm, that is, a plate thickness of about 1.7 mm is preferable.

Summarizing these results and taking into account the processing constraints of punching a thin steel plate with a press, the following results.
(1) For reducing cogging, it is preferable that the width W of the bridge portion 14 is equal to or greater than the plate thickness.
(2) From the viewpoint of output torque, the width W is preferably as small as 1.5 mm or less.
(3) Regarding the torque ripple, the torque ripple rate can be suppressed to 5% or less by setting the width W to a plate thickness to 1.7 mm.
(4) The width W needs to be equal to or greater than the plate thickness because of restrictions on press working when forming the bridge portion 14.
Note that the plate thickness is preferably within a range where press working is preferable (more than 0.30 mm, preferably 0.35 mm or more) as a thin steel plate for the stator core.
Therefore, considering (1) to (4), the upper limit value of the width W is preferably 1.5 mm from the viewpoint of output torque, and the lower limit value is preferably a plate thickness due to press working restrictions (plate thickness ≦ width W ≦ 1). 0.5 mm).

  As described above, in the motor 1, when the width W of the bridge portion 14 is set such that plate thickness ≦ width W ≦ 1.5 mm, the maximum torque can be increased as compared with a synchronous reluctance motor without a magnet. In the case of torque, the motor size can be reduced. In the motor 1, the output torque is increased, the occurrence of cogging due to the arrangement of the magnets is minimized, and the torque ripple is further reduced. Therefore, the quietness of the motor is improved, and when the motor 1 is used in an electric power steering device, the return of the handle is improved by reducing cogging, and the operability of the handle is improved by reducing torque ripple. To do. In addition, since each steel plate of the stator core made of laminated steel plates can be manufactured only by pressing, the manufacturing cost can be reduced and an inexpensive motor can be provided.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, the magnets 26 are attached to all the slits 25. However, some of the slits 25 may be left as gaps or may be appropriately filled with a nonmagnetic material such as a synthetic resin. It is. Further, the brushless motor according to the present invention can be applied to a hybrid vehicle, an electric vehicle and the like in addition to the electric power steering device.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Stator 3 Rotor 4 Motor case 4a Bottom part 5 Stator core 6 Stator coil 6a End part 7 Bus bar unit 8 Bracket 11 Outer stator 12 Inner stator 13 Teeth part 14 Bridge part 15 Slot 16 Teeth attachment groove (concave part)
17 Fitting portion 21 Power supply terminal 22 Rotor shaft 23a, 23b Bearing 24 Rotor core 25 Slit 26 Magnet 31 Resolver 32 Resolver rotor 33 Cover 34 Control board 35 Control board 36 Power system element 37 Control system element 38 Resolver stator W Bridge section width t Thickness of steel plate constituting stator

Claims (6)

A brushless motor having a hollow motor case, a stator fixed in the motor case, and a rotor disposed on the inner peripheral side of the stator and rotatably supported by the motor case,
The rotor includes a plurality of flux barriers penetrating the rotor in the axial direction, and a magnet is disposed in the flux barrier.
The stator is formed by laminating a plurality of thin steel plates formed by press working, and a plurality of teeth portions arranged radially in the radial direction and the adjacent tooth portions provided on the inner peripheral side of the teeth portions. A bridge portion that connects the inner peripheral side tip portions of each other,
When the thickness in the radial direction of the bridge portion is W, the W is set to a thickness t or more and 1.5 mm or less (t ≦ W ≦ 1.5 mm) of a steel plate constituting the stator. Brushless motor. The brushless motor according to claim 1,
The radial thickness W of the bridge portion is set to be not less than the plate thickness t of the steel plate capable of punching the steel plate constituting the stator with a press, and the torque ripple rate of the brushless motor is suppressed to 5% or less. The brushless motor is set to 1.5 mm or less. The brushless motor according to claim 1 or 2,
The stator includes an inner stator disposed on the inner peripheral side, and an outer stator disposed on the outer peripheral side,
The inner stator includes the tooth portion and the bridge portion. The brushless motor according to any one of claims 1 to 3,
A plurality of recesses are formed on the inner peripheral surface of the outer stator,
The outer peripheral side tip of the teeth portion is fitted into the recess,
The brushless motor, wherein the outer stator and the inner stator are fixed in a state of being prevented from coming off in a radial direction and a circumferential direction by inserting and fitting an outer peripheral end portion of the teeth portion into the concave portion. . The brushless motor according to claim 4,
The recess is formed in the shape of a dovetail with a cross-section having an inverted C shape,
A brushless motor characterized in that a tenon-like fitting portion whose outer end side is enlarged is formed at the outer peripheral end portion of the tooth portion. The brushless motor according to any one of claims 1 to 5,
A brushless motor in which a copper wire is wound around the teeth portion by distributed winding to form a coil.

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