JP2021175304A - motor - Google Patents

Abstract

To provide a motor that can generate a large cogging torque and can reduce manufacturing costs.SOLUTION: A motor 100 is a permanent magnet embedded type motor. The motor includes a stator 130 and rotor 150, the rotor being rotatable and provided with a gap between the stator 130 and the rotor. The rotor 150 has a rotor iron core 152 and a plurality of permanent magnets 154, which are fixed to the rotor iron core 152. A flat portion 170 is formed on the outer periphery of the rotor iron core 152 to increase the cogging torque. The flat portion 170 is formed in a plane orthogonal to a magnetic pole center axis Ca on the magnetic pole center axis Ca of a magnetic pole portion 160 formed by the permanent magnets 154.SELECTED DRAWING: Figure 3

Description

The present invention relates to a motor.

Motors (motors) used in devices that require a position holding function, such as electric variable valve timing control devices, require a large cogging torque. Patent Document 1 discloses a motor including a stator and a rotor in which a plurality of gaps for increasing cogging torque are partially provided in the circumferential direction. The plurality of gaps are provided at positions corresponding to the boundary gaps provided between the magnetic poles adjacent to each other in the circumferential direction and the cycle of the cogging torque obtained from the number of poles of the rotor and the number of slots of the stator in the magnetic poles. It includes the void inside the pole.

JP-A-2019-41530

In the motor described in Patent Document 1, in-pole gaps are provided at positions deviated from the center line of the magnetic poles by 1/2 of the period φ of the cogging torque in the circumferential direction, respectively, and boundary gaps are provided between the magnetic poles. A part is provided. Therefore, the number of voids increases, which may increase the manufacturing cost.

An object of the present invention is to provide a motor capable of generating a large cogging torque and reducing a manufacturing cost.

The motor according to one aspect of the present invention is a permanent magnet embedded motor, and includes a stator and a rotor that is rotatably provided with a gap in the stator. The rotor has a rotor core and a plurality of permanent magnets fixed to the rotor core. A flat surface portion for increasing the cogging torque is formed on the outer peripheral portion of the rotor core. The flat surface portion is formed in a plane shape orthogonal to the magnetic pole center axis on the magnetic pole center axis of the magnetic pole portion formed by the permanent magnet.

According to the present invention, it is possible to provide a motor capable of generating a large cogging torque and reducing a manufacturing cost.

The plan sectional view which shows the structure of the motor which concerns on embodiment of this invention. It is sectional drawing which shows a part of a motor, and shows about the circumferential angle θm and the magnetic pole pitch angle θp of a permanent magnet. It is sectional drawing which shows a part of a motor, and shows the circumferential width Lm of a permanent magnet and the circumferential width Lc of a plane part. The waveform diagram of the cogging torque of the motor which concerns on Example 1. FIG. The figure which shows the result of the degree analysis of the cogging torque waveform shown in FIG. FIG. 5 is a diagram showing a magnitude Tc of cogging torque when the width ratio Wr is changed in the motor according to the first embodiment (motor having a polar arc ratio of 0.66). FIG. 5 is a diagram showing a magnitude Tc of cogging torque when the width ratio Wr is changed in the motor according to the second embodiment (motor having a polar arc ratio of 0.55). It is a figure which shows the magnitude Tc of the cogging torque when the width ratio Wr is changed in the motor (the motor of the polar arc ratio 0.775) which concerns on Example 3. FIG. The figure which shows a part of the motor which concerns on the modification of this embodiment.

The motor according to this embodiment is used for a device that requires a position holding function, such as an electric variable valve timing control device. The valve timing control device is a device that controls the opening / closing timing of the intake valve and the exhaust valve by controlling the phase difference between the camshaft and the crankshaft by the rotational driving force of the motor. The motor used in the valve timing control device needs a position holding function, and it is necessary to secure the holding force by cogging torque. Hereinafter, the motor according to the embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a plan sectional view showing a configuration of a motor 100 according to an embodiment of the present invention. FIG. 1 shows a cross section of the motor 100 viewed from the axial direction, that is, a cross section orthogonal to the rotation axis. As shown in FIG. 1, the motor 100 includes a stator 130 fixed to a housing (not shown) and a rotor 150 rotatably provided on the inner peripheral side of the stator 130 with a gap.

The motor 100 is a brushless motor, which is a permanent magnet embedded type three-phase synchronous motor in which a permanent magnet 154 is embedded in a rotor 150. The motor 100 operates as an electric motor for rotating the rotor 150 by supplying a three-phase alternating current to the stator coil 138 wound around the stator core 132.

The rotor 150 is fixed to the shaft 118. The rotor 150 is rotatably held inside the stator core 132 by the shaft 118 being supported by the bearings of the housing.

The rotation center axis O of the rotor 150 coincides with the center axis of the cylindrical stator 130. In the following description, the direction parallel to the rotation center axis O of the rotor 150 is described as the axial direction, and the radiation direction orthogonal to the rotation center axis O of the rotor 150 and centered on the rotation center axis O of the rotor 150. Is described as the radial direction, and the circumferential direction around the rotation center axis O of the rotor 150, which is orthogonal to the rotation center axis O of the rotor 150, is described as the circumferential direction.

The stator 130 includes a cylindrical stator core 132 and a stator coil 138 that is wound around the stator core 132 in a concentrated manner. In the present embodiment, the winding method of the stator coil 138 is centralized winding, but the winding method is not limited to this, and distributed winding may be used. A plurality of (12 in this embodiment) slots 133 parallel to the central axis direction of the stator core 132 are formed in the inner peripheral portion of the stator core 132. The plurality of slots 133 are formed at equal intervals in the circumferential direction of the stator core 132.

Each slot 133 accommodates a stator coil 138. Teeth 134 are formed between the slots 133. In this embodiment, a plurality of (12 in this embodiment) teeth 134 are integrated with the annular core back 135. That is, the stator core 132 is an integrated core in which a plurality of teeth 134 and a core back 135 are integrally molded. The teeth 134 form a radial magnetic path, and the core back 135 forms a circumferential magnetic path. The teeth 134 guides the rotating magnetic field generated by the stator coil 138 to the rotor 150, and generates a rotational torque in the rotor 150.

The stator core 132 is formed, for example, by laminating a plurality of ring-shaped electromagnetic steel plates or soft magnetic metal plates. The stator core 132 is fitted and fixed to the inside of a cylindrical housing (not shown) by shrink fitting and press fitting.

The rotor 150 includes a cylindrical rotor core 152 and a plurality of permanent magnets 154 fixed to the rotor core 152. The rotor core 152 is formed, for example, by laminating a plurality of ring-shaped electromagnetic steel plates or soft magnetic metal plates.

Magnet holding holes 153 to which the rectangular parallelepiped permanent magnets 154 are fixed are formed in the vicinity of the outer peripheral portion of the rotor core 152 at equal intervals in the circumferential direction. A pair of magnet stop portions 153a (see FIG. 2) that define the positions of both peripheral surfaces of the permanent magnet 154 are formed on the inner surface of the magnet holding hole 153 in the radial direction. The permanent magnet 154 is inserted between the pair of magnet stoppers 153a and fixed in the magnet holding hole 153. The circumferential width of the magnet holding hole 153 is larger than the circumferential width of the permanent magnet 154. A magnetic gap 156 is formed between both ends of the permanent magnet 154 in the circumferential direction and both sides of the magnet holding hole 153 in the circumferential direction. An adhesive, a resin, or the like may be embedded in the magnetic gap 156 and solidified integrally with the permanent magnet 154.

The permanent magnet 154 forms the magnetic pole portion 160 of the rotor 150. In this embodiment, one magnetic pole portion 160 is formed by one permanent magnet 154. The permanent magnets 154 are arranged so that the pair of wide surfaces 154a are orthogonal to the magnetic pole center axis Ca (see FIG. 2) of the magnetic pole portion 160. The wide surface 154a is the surface having the largest area among the side surfaces. The magnetization direction of the permanent magnet 154 is in the radial direction, and the direction of the magnetization direction is reversed for each magnetic pole portion 160. That is, assuming that the surface of the permanent magnet 154 for forming a certain magnetic pole portion 160 on the stator 130 side is magnetized to the north pole and the surface on the shaft 118 side is magnetized to the south pole, the permanent magnet forming the adjacent magnetic pole portion 160 is formed. The surface of the stator 130 side of 154 is magnetized to the south pole, and the surface of the shaft 118 side is magnetized to the north pole. In the present embodiment, eight permanent magnets 154 are magnetized and arranged so that the magnetization direction changes alternately for each magnetic pole at equal intervals in the circumferential direction. The number of poles P of the rotor 150 is eight poles. As the permanent magnet 154, a neodymium-based or samarium-based sintered magnet, a ferrite magnet, a neodymium-based bonded magnet, or the like can be used.

FIG. 2 is a cross-sectional view showing a part of the motor 100, and shows a circumferential angle θm and a magnetic pole pitch angle θp of the permanent magnet 154. As shown in the figure, the magnetic pole center axis (magnetic pole center line) Ca of the magnetic pole portion 160 is set at the circumferential center position of the magnetic pole portion 160. In the present embodiment, the magnetic pole center axis Ca corresponds to the axis connecting the rectangular parallelepiped permanent magnet 154 at the center position in the circumferential direction and the rotation center axis O. When the magnetic pole pitch angle, which is the angle between the magnetic pole portions 160, is θp as the mechanical angle, the magnetic pole pitch angle θp is an angle obtained by dividing 360 degrees by the number of poles P (θp = 360 / P). In the present embodiment, since the number of poles P is eight, the magnetic pole pitch angle θp is 45 degrees (θp = 360/8). The magnetic pole pitch angle θp can also be said to be the angle from the midpoint between the adjacent permanent magnets 154 to the adjacent midpoint.

The midpoints between the adjacent permanent magnets 154 are the boundary portions 161 of the adjacent magnetic pole portions 160, and are provided at intervals of 45 degrees in the circumferential direction. A V-shaped groove portion 162 is formed at the boundary portion 161. The groove portion 162 is formed from one end to the other end in the axial direction of the rotor core 152. The groove portion 162 is a boundary gap portion formed to increase the cogging torque, similarly to the flat surface portion 170 described later.

In the rotor 150, when the circumferential angle (width angle) of the permanent magnet 154 is θm in terms of mechanical angle, the ratio (θm / θp) of the circumferential angle θm of the permanent magnet 154 to the magnetic pole pitch angle θp is the polar arc ratio. Is called. The polar arc ratio is a value obtained by dimensionlessizing the circumferential angle θm of the permanent magnet 154 with the magnetic pole pitch angle θp, and represents the magnitude of the permanent magnet 154 in the circumferential direction.

As shown in the figure, the circumferential angle θm of the permanent magnet 154 is the angle formed by the straight line L1 and the straight line L2. The straight line L1 is a straight line connecting the corner portion E1 of the permanent magnet 154 and the rotation center axis O, and the straight line L2 is a straight line connecting the corner portion E2 of the permanent magnet 154 and the rotation center axis O. The corner portion E1 of the permanent magnet 154 is a boundary between the radial outer surface and the circumferential end surface of the pair of wide surfaces 154a of the permanent magnet 154, and the corner portion E2 of the permanent magnet 154 is a pair of permanent magnets 154. It is a boundary between the outer surface in the radial direction and the other end surface in the circumferential direction of the wide surface 154a of the above.

FIG. 3 is a cross-sectional view showing a part of the motor 100, and shows the circumferential width Lm of the permanent magnet 154 and the circumferential width Lc of the flat surface portion 170. As shown in FIG. 3, in the present embodiment, a flat surface portion 170 for increasing the cogging torque is formed on the outer peripheral portion of the rotor core 152. The flat surface portion 170 is formed on the magnetic pole central axis Ca of the magnetic pole portion 160 in a plane shape orthogonal to the magnetic pole central axis Ca. That is, in the present embodiment, the flat surface portion 170 is formed so as to be parallel to the wide surface 154a of the permanent magnet 154. The flat surface portion 170 is formed from one end to the other end of the rotor core 152 in the axial direction.

Circumferential width of the permanent magnet 154 (width in the direction orthogonal to the magnetic pole center axis Ca and the rotation center axis O) Circumferential width of the flat surface portion 170 with respect to Lm (width in the direction orthogonal to the magnetic pole center axis Ca and the rotation center axis O) The ratio of Lc (hereinafter, also referred to as width ratio) Wr affects the magnitude of cogging torque, as will be described later. The width ratio Wr is obtained by dividing the circumferential width Lc of the flat surface portion 170 by the circumferential width Lm of the permanent magnet 154 (Wr = Lc / Lm). That is, the width ratio Wr is a value obtained by non-dimensionalizing the circumferential width Lc of the flat surface portion 170 with the circumferential width Lm of the permanent magnet 154, and represents the size of the flat surface portion 170 in the circumferential direction. In the rotary electric machine 100 provided with the flat surface portion 170, the magnitude of the cogging torque can be adjusted by adjusting the width ratio Wr.

As shown in FIGS. 2 and 3, the flat surface portion 170 is preferably formed so as to be within the installation range Am of the permanent magnet 154. The installation range Am of the permanent magnet 154 refers to the range between the intersection A1 between the straight line L1 and the outer peripheral surface of the rotor core 152 and the intersection A2 between the straight line L2 and the outer peripheral surface of the rotor core 152. The flat surface portion 170 may be formed larger than the installation range Am. At least, the flat surface portion 170 may be formed so as to overlap the permanent magnet 154 when viewed radially outward from the rotation center axis O. However, in order to suppress the decrease in the line-induced voltage described later, it is preferable to form the flat surface portion 170 within the installation range Am of the permanent magnet 154. That is, it is preferable that the circumferential angle θc of the flat surface portion 170 is equal to or less than the circumferential angle θm of the permanent magnet 154. The circumferential angle θc of the flat surface portion 170 is formed by a straight line connecting the rotation center axis O and one end portion Bp1 of the flat surface portion 170 and a straight line connecting the rotation center axis O and the other end portion Bp2 of the flat surface portion 170. The angle.

As shown in FIG. 3, the flat surface portion 170 extends from the magnetic pole central axis Ca to one side and the other side in the circumferential direction by the same distance (Lc / 2) with reference to the magnetic pole central axis Ca. Both ends Bp1 and Bp2 of the flat surface portion 170 are formed so as to be continuous with the outermost outer peripheral surface (arc surface) 152x having a radius Rx of the rotor core 152. Therefore, the rotor core 152 can be easily manufactured as compared with the case where a concave portion is provided on the outer peripheral portion of the rotor core 152 and the bottom portion of the concave portion is a flat surface portion.

By forming the flat surface portion 170 in this way, in the region within the installation range Am of the permanent magnet 154, between the outer peripheral surface of the rotor core 152 and the inner peripheral surface of the stator core 132 (the tip surface of the teeth 134). The distance h is the minimum at the position of the outermost peripheral surface 152x and the maximum at the magnetic pole central axis Ca. In other words, the flat surface portion 170 is formed so that the distance h between the outer peripheral surface of the rotor core 152 and the inner peripheral surface of the stator core 132 decreases as the distance from the magnetic pole center axis Ca in the circumferential direction increases. ing.

The flat surface portion 170 formed on the rotor core 152 is formed one on each of the plurality of magnetic pole portions 160, and the rotor core 152 has a rotationally symmetric shape centered on the rotation center axis O. The rotationally symmetric shape is a shape in which the shape does not change when the rotation is moved by a certain angle around the rotation center axis O, which is the axis of symmetry. The rotor core 152 according to the present embodiment has an eight-fold rotational symmetry shape that overlaps with itself when rotated by 45 degrees, that is, (360 / n) degrees (n = 8) around the rotation center axis O.

In the motor 100 according to the present embodiment, by providing the flat surface portion 170, the reluctance is intended by changing the distance h between the rotor core 152 and the stator core 132 as the rotor 150 rotates. The cogging torque is increased.

Hereinafter, specific examples of the effects of this embodiment will be shown.

[Example 1]
FIG. 4 is a waveform diagram of the cogging torque of the motor 100 according to the first embodiment, and FIG. 5 is a diagram showing the result of order analysis of the cogging torque waveform shown in FIG. The horizontal axis of FIG. 4 is the rotation angle of the motor 100, which is indicated by the mechanical angle. The waveform diagram shown in FIG. 4 is obtained from the result of magnetic field analysis by the finite element method (FEM).

In the motor 100 according to the first embodiment, the permanent magnet 154 is formed so that the polar arc ratio is about 2/3 (= about 30/45). In the motor 100 according to the first embodiment, the circumferential angle θm of the permanent magnet 154 is about 30 degrees (specifically, 29.76 degrees). Therefore, the polar arc ratio of the rotor 150 according to the first embodiment is 0.66.

In FIGS. 4 and 5, the calculation result for the motor 100 according to the first embodiment is shown by a solid line, and the calculation result for the motor according to the comparative example 1 in which the flat surface portion 170 is not provided is shown by a broken line. The motor according to Comparative Example 1 has the same configuration as the motor 100 according to Example 1 except that the flat surface portion 170 is not provided.

The period of cogging torque (mechanical angle) is a value obtained by dividing 360 degrees by the least common multiple of the number of poles P of the rotor 150 and the number of teeth 134 of the stator 130. In the motor 100 according to the first embodiment, the number of poles P is 8 and the number of teeth 134 is 12. Therefore, since the least common multiple of the number of poles P and the number of teeth 134 is 24, the period (mechanical angle) of the cogging torque is 15 (= 360/24) degrees.

As shown in FIGS. 4 and 5, the cogging torque of the motor 100 according to the first embodiment has a sixth-order component in the electric angle (24th-order component in the mechanical angle), that is, 60 degrees in the electric angle (15 degrees in the mechanical angle). The component of the cycle is dominant, and its peak value is much higher than that of Comparative Example 1. In this way, when the flat surface portion 170 is provided, the cogging torque can be increased as compared with the case where the flat surface portion 170 is not provided.

FIG. 6 is a diagram showing the magnitude Tc of the cogging torque when the width ratio Wr is changed in the motor (motor having a polar arc ratio of 0.66) 100 according to the first embodiment, and is a diagram showing the magnitude Tc of the cogging torque in the circumferential direction of the permanent magnet 154. The calculation results under a plurality of conditions in which the circumferential width Lc of the flat surface portion 170 is changed without changing the width Lm are shown. The horizontal axis represents the width ratio Wr, the vertical axis on the left side (first axis) represents the magnitude Tc [Nm] of the cogging torque shown by the solid line, and the vertical axis on the right side (second axis) is a broken line. The indicated line-induced voltage [V] is shown. In the present specification, the magnitude Tc of the cogging torque is the absolute value of the peak value (maximum value) of the cogging torque on the positive side and the peak value (maximum value) of the cogging torque on the negative side in the torque waveform diagram shown in FIG. Refers to the sum with the value. The calculation result when the width ratio Wr shown in FIG. 6 is 0.52 is obtained from the waveform (solid line) of the cogging torque shown in FIG. That is, the waveform (solid line) of the cogging torque shown in FIG. 4 shows the calculation result when the width ratio Wr is 0.52 in the motor 100 according to the first embodiment, that is, the motor 100 having a polar arc ratio of 0.66. There is.

The value of the width ratio Wr of 0 (zero) indicates the magnitude Tc of the cogging torque of the motor according to Comparative Example 1 which does not have the flat surface portion 170. As shown in FIG. 6, the magnitude Tc of the cogging torque of the motor according to Comparative Example 1 is 0.011 [Nm]. The magnitude Tc of the cogging torque of the motor 100 according to the first embodiment having the flat surface portion 170 is larger than the magnitude Tc of the cogging torque of the motor according to the comparative example 1.

As shown in FIG. 6, in the motor 100 according to the first embodiment, the magnitude Tc of the cogging torque is 0.050 [Nm] when the width ratio Wr is 0.37, and is 0.050 [Nm] when the width ratio Wr is 0.52. Among the calculation results, the maximum was 0.076 [Nm], and when the width ratio was 0.63, it was 0.047 [Nm]. Therefore, it is estimated that there is a point where the magnitude Tc of the cogging torque is maximized when the width ratio Wr is between 0.37 and 0.63. Therefore, in the motor 100 according to the first embodiment, it is preferable to form the flat surface portion 170 so that the width ratio Wr is 0.37 to 0.63. Further, from the approximate curve of the calculation result shown in the figure, it is stated that in the motor 100 according to the first embodiment, a large cogging torque can be generated by setting the width ratio Wr to a value of 0.4 or more and 0.6 or less. Conceivable.

In the motor 100 according to the first embodiment, the magnitude Tc of the cogging torque is 0.023 [Nm] when the width ratio Wr is 0.73 and 0.064 [Nm] when the width ratio Wr is 0.81. When the width ratio Wr was 0.89, it was 0.063 [Nm]. As described above, in the motor 100 according to the first embodiment, when the width ratio Wr is increased, the width ratio Wr has a first peak between 0.37 and 0.63, and the width ratio Wr becomes 0. It is estimated that there is a second peak between 81 and 0.89. Therefore, in the motor 100 according to the first embodiment, the flat surface portion 170 may be formed so that the width ratio Wr is 0.81 to 0.89. From the approximate curve of the calculation result, it can be read that a sufficient cogging torque can be obtained in the range where the width ratio Wr is 0.8 or more and 0.9 or less. Therefore, in the motor 100 according to the first embodiment, a sufficient cogging torque can be obtained even by setting the width ratio Wr to a value of 0.8 or more and 0.9 or less.

The line-induced voltage decreases as the width ratio Wr increases. The line-induced voltage has the same value as the torque constant. Therefore, when the current conditions of the line-induced voltage are the same, the larger the value, the larger the output torque. As described above, the gap (distance h) between the flat surface portion 170 and the stator core 132 is larger than the gap (distance h) between the outermost peripheral surface 152x of the rotor core 152 and the stator core 132. growing. Therefore, as the circumferential width Lc of the flat surface portion 170 increases, the gap (distance h) between the rotor core 152 and the stator core 132 increases, and the line-induced voltage decreases.

Therefore, the circumferential width Lc of the flat surface portion 170 needs to be set so that the output torque of the motor 100 becomes a line-induced voltage that satisfies the required specifications. For example, when it is necessary to secure 80% or more of the line-induced voltage when the flat surface portion 170 is provided, assuming that the calculation result of the line-induced voltage in Comparative Example 1 in which the flat surface portion 170 is not provided is 100%, FIG. From the calculation result shown in 6, it is considered preferable to set the width ratio Wr to 1.02 or less.

[Example 2]
FIG. 7 is a diagram similar to FIG. 6, showing the magnitude Tc of the cogging torque when the width ratio Wr is changed in the motor (motor having a polar arc ratio of 0.55) 100 according to the second embodiment. Is. In the motor 100 according to the second embodiment, the circumferential width Lm of the permanent magnet 154 is shorter than the circumferential width Lm of the permanent magnet 154 of the motor 100 according to the first embodiment, but the other configurations are the motor 100 according to the first embodiment. Is the same as. In other words, the motor 100 according to the second embodiment has the same configuration as the motor 100 according to the first embodiment except that the polar arc ratio is different.

In the motor 100 according to the second embodiment, the permanent magnet 154 is formed so that the polar arc ratio is about 5/9 (= about 25/45). In the motor 100 according to the second embodiment, the circumferential angle θm of the permanent magnet 154 is about 25 degrees (specifically, 24.76 degrees). Therefore, the polar arc ratio of the rotor 150 according to the second embodiment is 0.55.

FIG. 7 shows the calculation results under a plurality of conditions in which the circumferential width Lc of the flat surface portion 170 is changed without changing the circumferential width Lm of the permanent magnet 154. The value of the width ratio Wr of 0 (zero) indicates the magnitude Tc of the cogging torque of the motor (motor having a polar arc ratio of 0.55) according to Comparative Example 2 which does not have the flat surface portion 170. The motor according to Comparative Example 2 has the same configuration as the motor 100 according to the second embodiment except that the flat surface portion 170 is not provided.

As shown in FIG. 7, the magnitude Tc of the cogging torque of the motor according to Comparative Example 2 is 0.119 [Nm]. The magnitude Tc of the cogging torque of the motor 100 according to the second embodiment having the flat surface portion 170 is larger than the magnitude Tc of the cogging torque of the motor according to the comparative example 2.

In the motor 100 according to the second embodiment, the magnitude Tc of the cogging torque is 0.166 [Nm] when the width ratio Wr is 0.44 and 0.205 [Nm] when the width ratio Wr is 0.62. When the width ratio was 0.76, it was 0.197 [Nm]. Therefore, it is estimated that there is a point where the magnitude Tc of the cogging torque is maximized when the width ratio Wr is between 0.44 and 0.76. Therefore, in the motor 100 according to the second embodiment, it is preferable to form the flat surface portion 170 so that the width ratio Wr is 0.44 to 0.76. Further, from the approximate curve of the calculation result shown in the figure, it is stated that in the motor 100 according to the second embodiment, a large cogging torque can be generated by setting the width ratio Wr to a value of 0.5 or more and 0.7 or less. Conceivable.

In the second embodiment as well, as in the first embodiment, the circumferential width Lc of the flat surface portion 170 needs to be set so that the output torque of the motor 100 becomes a line-induced voltage that satisfies the required specifications. For example, when it is necessary to secure 80% or more of the line-induced voltage when the flat surface portion 170 is provided, assuming that the calculation result of the line-induced voltage in Comparative Example 2 in which the flat surface portion 170 is not provided is 100%, FIG. From the calculation result shown in 7, it is considered preferable to set the width ratio Wr to 1.15 or less.

[Example 3]
FIG. 8 is a diagram similar to FIG. 6, showing the magnitude Tc of the cogging torque when the width ratio Wr is changed in the motor (motor having a polar arc ratio of 0.775) 100 according to the third embodiment. Is. In the motor 100 according to the third embodiment, the circumferential width Lm of the permanent magnet 154 is longer than the circumferential width Lm of the permanent magnet 154 of the motor 100 according to the first embodiment, but the other configurations are the motor 100 according to the first embodiment. Is the same as. In other words, the motor 100 according to the third embodiment has the same configuration as the motor 100 according to the first embodiment except that the polar arc ratio is different.

In the motor 100 according to the third embodiment, the permanent magnet 154 is formed so that the polar arc ratio is about 7/9 (= about 35/45). In the motor 100 according to the third embodiment, the circumferential angle θm of the permanent magnet 154 is about 35 degrees (specifically, 34.88 degrees). Therefore, the polar arc ratio of the rotor 150 according to the third embodiment is 0.775.

FIG. 8 shows the calculation results under a plurality of conditions in which the circumferential width Lc of the flat surface portion 170 is changed without changing the circumferential width Lm of the permanent magnet 154. The value of the width ratio Wr of 0 (zero) indicates the magnitude Tc of the cogging torque of the motor (motor having a polar arc ratio of 0.775) according to Comparative Example 3 which does not have the flat surface portion 170. The motor according to Comparative Example 3 has the same configuration as the motor 100 according to Example 3 except that the flat surface portion 170 is not provided.

As shown in FIG. 8, the magnitude Tc of the cogging torque of the motor according to Comparative Example 3 is 0.180 [Nm]. In the motor 100 according to the third embodiment, the magnitude Tc of the cogging torque is 0.157 [Nm] when the width ratio Wr is 0.31 and 0.163 [Nm] when the width ratio Wr is 0.44. When the width ratio Wr was 0.54, it was 0.221 [Nm]. From the approximate curve of the calculation result shown in the figure, if the width ratio Wr is about 0.5 or more, that is, if the circumferential width Lc of the flat surface portion 170 is secured about half or more of the circumferential width Lm of the permanent magnet 154, the flat surface portion 170 It is considered that the cogging torque can be increased by providing the above. Therefore, in the motor 100 according to the third embodiment, it is preferable to set the width ratio Wr to a value of about 0.5 or more in order to increase the cogging torque as compared with the case where the flat surface portion 170 is not provided.

In the motor 100 according to the third embodiment, the magnitude Tc of the cogging torque is 0.361 [Nm] when the width ratio Wr is 0.70 and 0.421 [Nm] when the width ratio Wr is 0.76. When the width ratio Wr was 0.82, it was 0.463 [Nm]. Further, in the motor 100 according to the third embodiment, the magnitude Tc of the cogging torque is 0.442 [Nm] when the width ratio Wr is 0.88, and 0.356 [Nm] when the width ratio Wr is 0.93. ]. In the motor 100 according to the third embodiment, it is estimated that there is a point where the magnitude Tc of the cogging torque is maximized when the width ratio Wr is between 0.76 and 0.88. Therefore, in the motor 100 according to the third embodiment, it is preferable to form the flat surface portion 170 so that the width ratio Wr is 0.76 to 0.88. Further, from the approximate curve of the calculation result shown in the figure, it is stated that in the motor 100 according to the third embodiment, a large cogging torque can be generated by setting the width ratio Wr to a value of 0.7 or more and 0.9 or less. Conceivable.

In the third embodiment as well, as in the first embodiment, the circumferential width Lc of the flat surface portion 170 needs to be set so that the output torque of the motor 100 becomes a line-induced voltage that satisfies the required specifications. For example, when it is necessary to secure 80% or more of the line-induced voltage when the flat surface portion 170 is provided, assuming that the calculation result of the line-induced voltage in Comparative Example 3 in which the flat surface portion 170 is not provided is 100%, FIG. From the calculation result shown in 8, it is considered preferable to set the width ratio Wr to 0.90 or less.

As described above, the motor 100 according to the present embodiment has a simple configuration in which the flat surface portion 170 is provided on the magnetic pole center axis Ca, and aims to increase the cogging torque generated due to the switching of the magnetic pole portions 160 of the rotor 150. be able to. When designing the motor 100, the magnitude Tc of the cogging torque generated by the motor that does not have the flat surface portion 170 is obtained, and then, in the motor provided with the flat surface portion 170, the width ratio Wr is changed to obtain the cogging torque. It is preferable to adjust the size Tc of.

From the calculation results for the motor 100 of Examples 1 to 3, in order to increase the magnitude Tc of the cogging torque regardless of the polar arc ratio as compared with the case where the flat surface portion 170 is not provided, the circumferential direction of the flat surface portion 170 is to be increased. It can be said that it is preferable to set the width Lc to a value of about half or more of the circumferential width Lm of the permanent magnet 154. Further, from the calculation result for the motor 100 of Example 1, if the polar arc ratio is about 2/3, the width ratio Wr is 0.4 or more and 0.6 or less, or 0.8 or more and 0.9 or less. It can be said that it is preferable to set it to a value. From the calculation results for the motor 100 of the second embodiment, if the polar arc ratio is about 5/9, it can be said that it is preferable to set the width ratio Wr to a value of 0.5 or more and 0.7 or less. From the calculation results for the motor 100 of Example 3, if the polar arc ratio is about 7/9, it can be said that it is preferable to set the width ratio Wr to a value of 0.7 or more and 0.9 or less.

According to the above-described embodiment, the following effects are exhibited.

The motor 100 is a permanent magnet embedded type motor, and includes a stator 130 and a rotor 150 that is rotatably provided in the stator 130 with a gap. The rotor 150 has a rotor core 152 and a plurality of permanent magnets 154 fixed to the rotor core 152. A flat surface portion 170 for increasing the cogging torque is formed on the outer peripheral portion of the rotor core 152. The flat surface portion 170 is formed in a plane shape orthogonal to the magnetic pole central axis Ca on the magnetic pole central axis Ca of the magnetic pole portion 160 formed by the permanent magnet 154.

The magnitude Tc of the cogging torque can be adjusted based on the polar arc ratio and the ratio Wr of the circumferential width of the flat surface portion 170 and the permanent magnet 154. Therefore, according to the present embodiment, it is possible to provide the motor 100 that can generate a large cogging torque and can reduce the manufacturing cost.

<Modification example>
In the above embodiment, an example in which one magnetic pole portion 160 is formed by one permanent magnet 154 has been described, but the present invention is not limited thereto. As shown in FIG. 9, one magnetic pole portion 260 may be formed by a plurality of permanent magnets 254. In the rotor 250 according to the present modification, as in the above embodiment, the flat surface portion 270 for increasing the cogging torque is formed on the magnetic pole center axis Ca of the magnetic pole portion 260 so as to be orthogonal to the magnetic pole center axis Ca. Will be done. As a result, the same effect as that of the above-described embodiment is obtained. Further, by increasing the number of permanent magnets 254 for forming each magnetic pole portion 260 to a plurality, the magnetic flux density of each magnetic pole portion 260 can be increased, and the magnet torque can be increased.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. No.

100 ... motor, 130 ... stator, 132 ... stator core, 138 ... stator coil, 150, 250 ... rotor, 152 ... rotor core, 152x ... outermost surface, 154,254 ... permanent magnet, 154a ... wide Surface, 160, 260 ... Magnetic pole portion, 170, 270 ... Flat portion, Ca ... Magnetic pole central axis, Lc ... Circumferential width of flat portion, Lm ... Permanent magnet circumferential width, O ... Rotation center axis, Wr ... Width ratio (Ratio of width in the circumferential direction)

Claims (4)

It is a permanent magnet embedded type motor.
A stator and a rotor provided so as to be rotatable with a gap in the stator are provided.
The rotor has a rotor core and a plurality of permanent magnets fixed to the rotor core.
A flat surface portion for increasing the cogging torque is formed on the outer peripheral portion of the rotor core.
The flat surface portion is formed in a plane shape orthogonal to the magnetic pole center axis on the magnetic pole center axis of the magnetic pole portion formed by the permanent magnet.
motor. In the motor according to claim 1,
Both ends of the flat surface portion are continuous with the outermost peripheral surface of the rotor core.
motor. In the motor according to claim 1,
The permanent magnet has a rectangular parallelepiped shape, and its wide surface is arranged so as to be orthogonal to the magnetic pole center axis.
The circumferential width of the flat surface portion is set to a value of about half or more of the circumferential width of the permanent magnet.
motor. In the motor according to claim 1,
The permanent magnet has a rectangular parallelepiped shape, and its wide surface is arranged so as to be orthogonal to the magnetic pole center axis.
The polar arc ratio of the permanent magnet is about 2/3, and when the circumferential width of the permanent magnet is Lm and the circumferential width of the flat surface portion is Lc, the ratio Lc / Lm of the width in the circumferential direction is 0. Set to a value of 4 or more and 0.6 or less,
motor.

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