JP2006197786A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless motor capable of reducing a ripple rate, with no increase in ripple torque due to variation in dimensional accuracy of a rotor magnet. <P>SOLUTION: An inner rotor type brushless motor 1 comprises a rotor 20 in which a plurality of rotor magnets 23 are arranged on the outer peripheral surface, and a stator 10 in which a coil 14 is wound on teeth 13 radially arranged to face an outside surface 23d of the rotor magnet 23. With the number of magnetic poles being set to be 20, the number of teeth 13 to be 18, and the outside diameter of stator 10 to be in the range 70-80 mm, a magnetic pole width M of the rotor magnet 23 is set in the range 5.135-5.777 mm. An eccentric radius N of the outside surface 23d is set in the range 10.8-24.7 mm so that the central part in a width direction of the outside surface 23d facing the stator 10 protrudes to the outside in a radial direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a brushless motor, and more particularly to a brushless motor effective in reducing torque ripple in an inner rotor type.

  The brushless motor desirably has a small cogging torque when no driving current is flowing, and a small torque ripple generated when the driving current is flowing. Conventionally, various techniques for reducing the cogging torque and the like have been proposed. Cogging torque is generally generated at the switching position of each magnetic pole of the motor. The cogging torque is a pulsation torque generated by the least common multiple of the number of salient poles (teeth) and the number of magnetic poles per rotation, and the magnitude thereof is inversely proportional to the number of pulsations. Therefore, the cogging torque and the ripple torque can be reduced by configuring the motor in multiple poles and multiple slots and increasing the above-mentioned least common multiple.

For example, in the brushless motor described in Patent Document 1, the rotor has a configuration in which 10 or 14 magnets are bonded to the inner peripheral surface thereof, and the stator has a configuration having 12 teeth. In the brushless motor of Patent Document 1, for example, when the number of magnetic poles is 10, 60 pulsations are generated per rotation, and the cogging torque can be suppressed to a small value.
Further, Patent Document 1 proposes to reduce the cogging torque by setting the ratio between the pole pitch of the rotor and the circumferential length of the magnet to a predetermined value.

JP 2000-134893 (page 3, FIG. 1)

However, as in the case of the brushless motor described in Patent Document 1, the ratio between the pole pitch of the rotor and the circumferential length of the magnet is set to a predetermined value, and the rotor magnet formed at the predetermined setting value is attached to the rotor body The dimensional accuracy of the magnet is required. For this reason, if there are variations in the dimensions of the rotor magnet, the cogging torque and the ripple torque may increase.
Moreover, in order to function effectively as a motor, it is necessary to ensure high-torque driving, and it is necessary to prevent the motor efficiency from deteriorating as cogging torque and ripple torque are reduced. It was.
In view of the above problems, an object of the present invention is to provide a brushless motor capable of reducing a ripple ratio and ensuring a high torque without increasing a ripple torque due to variations in dimensional accuracy of a rotor magnet. It is in.

  According to the present invention, a winding is wound around a rotor having a plurality of rotor magnets disposed on an outer peripheral surface and teeth disposed radially to face the outer peripheral surface of the rotor magnet. The rotor has an inner rotor type brushless motor, the number of magnetic poles of the rotor being 20, the outer diameter of the stator being set in the range of 70 mm to 80 mm, and the number of teeth being 18 The rotor magnet has a circumferential width set in the range of 5.135 mm to 5.777 mm, and a central portion in the width direction of the outer peripheral surface facing the stator protrudes radially outward. This is solved by setting the radius of the outer peripheral surface to a range of 10.8 mm to 24.7 mm.

  Thus, the inner rotor type brushless motor of the present invention has 20 poles, 18 teeth (number of slots), and an outer diameter of the stator set in the range of 70 mm to 80 mm. The rotor magnet has a circumferential width set in the range of 5.135 mm to 5.777 mm, and the outer circumferential surface facing the stator has a widthwise central portion protruding radially outward. The radius of the surface is set in the range of 10.8 mm to 24.7 mm. Thus, by setting the number of poles, the number of slots, and the shape of the rotor magnet, it is possible to configure a brushless motor with an extremely reduced ripple rate as shown in the following embodiments.

  In addition, according to the present invention, the above-described problem is that a winding is wound around a rotor having a plurality of rotor magnets disposed on the outer circumferential surface and teeth disposed radially to face the outer circumferential surface of the rotor magnet. An inner rotor type brushless motor, wherein the rotor has 16 magnetic poles, the stator has an outer diameter in the range of 70 mm to 80 mm, and the number of teeth. The rotor magnet has a circumferential width set in the range of 5.624 mm to 6.327 mm, and a central portion in the width direction of the outer peripheral surface facing the stator projects radially outward. Thus, the problem is solved by setting the radius of the outer peripheral surface in the range of 10.8 mm to 21.65 mm.

  Thus, the inner rotor type brushless motor of the present invention has 16 poles, 18 teeth (number of slots), and an outer diameter of the stator set in the range of 70 mm to 80 mm. The rotor magnet has a circumferential width set in the range of 5.624 mm to 6.327 mm, and the outer circumferential surface facing the stator has a widthwise central portion protruding radially outward. The radius of the surface is set in the range of 10.8 mm to 21.65 mm. Thus, by setting the number of poles, the number of slots, and the shape of the rotor magnet, it is possible to configure a brushless motor with an extremely reduced ripple rate as shown in the following embodiments.

  Further, the problem is that a rotor having a plurality of rotor magnets disposed on an outer peripheral surface, a stator having windings wound around teeth radially disposed so as to face the outer peripheral surface of the rotor magnet, The rotor has a number of magnetic poles, the stator has a number of teeth of 18, and the stator has an outer diameter in the range of 70 mm to 80 mm. At the same time, the rotor can be solved by setting its outer diameter in the range of 45.98 mm to 57.0 mm.

  Thus, the inner rotor type brushless motor of the present invention has 20 poles, 18 teeth (slots), an outer diameter of the stator set in a range of 70 mm to 80 mm, and an outer surface of the rotor. The diameter is set in the range of 45.98 mm to 57.0 mm. By setting the number of poles, the number of slots, and the outer diameter of the stator and rotor in this way, it is possible to configure a brushless motor that can reduce the ripple rate and secure a high torque value as shown in the following embodiments. it can.

  Further, the rotor magnet is set to have a circumferential width of about 6.419 mm, and a radius of the outer circumferential surface is set so that a central portion in the width direction of the outer circumferential surface facing the stator protrudes radially outward. It is preferable that it is set to 10.8 mm. Thus, by setting the shape of the rotor magnet, the ripple rate can be reduced.

  According to the inner rotor type brushless motor of the present invention, the circumferential width of the rotor magnet and the radius of the curved shape in which the circumferential central portion of the outer circumferential surface protrudes radially outward are set within a predetermined range. As a result, the ripple rate can be extremely reduced. At this time, a high torque motor can be obtained by setting the outer diameter of the rotor within an appropriate range.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the members, arrangements, and the like described below do not limit the present invention, and it is needless to say that various modifications can be made in accordance with the spirit of the present invention.
1 to 6 relate to an embodiment of the present invention, FIG. 1 is an explanatory view showing a configuration of a brushless motor, FIG. 2 is an explanatory view of a stator and a rotor of the brushless motor of FIG. 1, and FIG. FIG. 4 and FIG. 5 are graphs showing the ripple rate of the brushless motor, and FIG. 6 is a graph showing the torque with respect to the rotor outer diameter of the brushless motor.

  An embodiment in which the brushless motor of the present invention is applied to a brushless motor 1 (hereinafter referred to as “motor 1”) of an electric power steering apparatus (EPS) will be described. FIG. 1 is an explanatory diagram showing the configuration of the motor 1 of this example. The motor 1 is an inner rotor type, and includes a stator 10, a rotor 20 that is rotatably supported in the stator 10, and a housing 30 that accommodates the stator 10 and the rotor 20 therein as main components. When the driver operates the steering wheel, the motor 1 is controlled and driven based on a steering angle, a traveling speed, and the like, and supplies a steering assist force to the steering column shaft via a reduction gear (not shown) linked to the shaft 21 of the rotor 20. It is supposed to be.

The stator 10 of this example is a winding in which a coil is wound around a stator core 11 fixed to the inner peripheral side of a bottomed cylindrical housing body 31 and a tooth 13 protruding radially inward from an outer core 12 of the stator core 11. 14 is provided. In the stator 10 of this example, 18 teeth 13 are arranged at substantially equal angular intervals in the circumferential direction of the outer core 12 and project radially from the outer core 12 toward the center.
The rotor 20 of this example includes a shaft 21, an annular spacer 22 made of a magnetic material and attached to the shaft 21, and a rotor magnet 23 attached to the outer peripheral surface of the spacer 22. In the rotor 20 of this example, 20 rotor magnets 23 are disposed on the outer peripheral surface of the spacer 22 so as to be separated from each other in the width direction at substantially equal angular intervals. Further, the rotor magnets 23 adjacent to each other in the circumferential direction are magnetized so that the magnetic flux direction is opposite to the radial direction. The rotor magnet 23 of this example is a neodymium magnet and is magnetized so that the magnetic flux density is 1.28T.

The housing 30 of this example includes a bottomed cylindrical housing body 31, an end housing 32 that closes the opening of the housing body 31, and bearings 33 and 34 that rotatably support the shaft 21. The bearing 33 is fixed to a bulging portion formed at the bottom of the housing body 31, and the bearing 34 is fixed to the end housing 32.
A substrate 35 is disposed on the end housing 32 side in the housing body 31. A hall sensor 36 for detecting the rotational position of the rotor 20 is disposed on the substrate 35 so that changes in the magnetic poles of the rotor magnet 23 can be captured. That is, in the motor 1 of this example, the current to the winding 14 is appropriately switched based on the detection signal of the hall sensor 36 using the main magnetic flux generated by the rotor magnet 23, and a rotating magnetic field that rotates the rotor 20 is formed. .

  FIG. 2 is an explanatory view of the stator 10 and the rotor 20 of the motor 1 viewed from the axial direction. The stator 10 of this example is set to an outer diameter dimension D (mm). The protruding length of the teeth 13 is appropriately set according to the outer diameter R (mm) of the rotor 20. That is, the protruding length of the teeth 13 is set so as to provide a predetermined gap between the stator 10 and the rotor 20. Further, the outer diameter R of the rotor 20 is appropriately set according to the width and the number of poles of the rotor magnet 23.

As shown in FIG. 3, the rotor magnet 23 of this example is formed symmetrically in the width direction (circumferential direction), and is substantially radially outward from both ends in the width direction of the inner peripheral surface 23 a that contacts the spacer 22. Side surfaces 23b and 23c extend toward the outside, and an outer surface 23d connecting the radially outer ends of the side surfaces 23b and 23c is formed as a curved surface having a predetermined curvature. In the rotor magnet 23 of this example, the side surfaces 23b and 23c are formed substantially in parallel.
Further, as shown in FIG. 3, the outer surface 23d is set to a curved surface having a radius (eccentric radius) N (mm). In the figure, the point P represents the center of this curved surface. The radius N is set to be smaller than a radius d (= R / 2) (mm) to the maximum outer peripheral surface (surface or side located on the outermost radial direction) of the rotor magnet 23. In the figure, point O is the axis center. That is, the rotor magnet 23 is formed such that the center portion in the width direction protrudes radially outward. In the rotor magnet 23 of this example, the magnetic pole width in the circumferential direction is set to M (mm).

  Table 1 shows the torque and ripple rate when the combination of the magnetic pole width M and the eccentric radius N is changed (Examples 1 to 9) in the motor 1 of this example (number of magnetic poles: 20, number of slots: 18). The ripple rate is a value obtained by dividing the difference between the maximum value and the minimum value of torque at a predetermined current value by the maximum value. Table 1 shows the unit as a percentage. FIG. 4 is a graph of Table 1. The horizontal axis represents the ripple rate (%), and the vertical axis represents the different motors 1 (Examples 1 to 9) combined with various dimensions. Moreover, in each Example of Table 1, the outer diameter dimension D of the stator 10 is set to 76 mm.

In the combinations shown in Table 1 (Examples 1 to 9), there are three types of eccentric radii N (10.80 mm, 17.5 mm) for the same magnetic pole width M (5.135 mm, 5.777 mm, 6.419 mm). 75mm, 24.70mm). When the eccentric radius N is 24.70 mm, the eccentric radius N and the radius d substantially coincide.
4 and the like, it can be seen that when the magnetic pole width M is at least 5.777 mm or less, the ripple ratio is less than 0.9%, but when the magnetic pole width M is 6.419 mm, the ripple ratio exceeds 1%. When the magnetic pole width M is the same, the smaller the eccentric radius N, the smaller the ripple rate. Thus, when the motor 1 is set to 20 poles and 18 slots, when the magnetic pole width M is in the range of 5.135 mm to 5.777 mm and the eccentric radius N is in the range of 10.8 mm to 24.7 mm, It was confirmed that the ripple rate was 0.9% or less and showed a good value. When the shape of the rotor magnet 23 is set in this way, torque unevenness is suppressed and the ripple rate can be reduced.
Similarly, when the outer diameter D of the stator 10 is set to 70 mm and 80 mm, the magnetic pole width M is in the range of 5.135 mm to 5.777 mm and the eccentric radius N is 10.8 mm to 24.24. It was confirmed that the ripple rate could be 0.9% or less when it was within the range of 7 mm.

Next, in the motor 1 in which the number of magnetic poles is set to 16 and the number of slots is set to 18, an example (Examples 10 to 18) in which the combination of the magnetic pole width M and the eccentric radius N is changed will be described. In this example, since the number of magnetic poles is 16, the rotor magnets 23 are arranged at an interval of about 22.5 degrees so that the magnetic flux directions of the rotor magnets 23 adjacent in the circumferential direction are opposite.
Table 2 shows the combinations of the magnetic pole width M and the eccentric radius N in this example (Examples 10 to 18), and the torque and ripple rate at that time. FIG. 5 is a graphical representation of Table 2. Further, in each example of Table 2, the outer diameter D of the stator 10 is set to 76 mm as in the examples of Table 1.

In the combinations shown in Table 2 (Examples 10 to 18), there are three types of eccentric radii N (10.80 mm, 16.30 mm) for the same magnetic pole width M (5.624 mm, 6.327 mm, 7.030 mm). 23 mm, 21.65 mm).
From FIG. 5 and the like, it can be seen that when the magnetic pole width M is at least 6.327 mm or less, the ripple ratio is less than 0.6%, but when the magnetic pole width M is 6.419 mm, the ripple ratio exceeds 1%. At this time, the ripple rate tends to be smaller as the eccentric radius N is smaller. Thus, when the motor 1 is set to 16 poles and 18 slots, when the magnetic pole width M is in the range of 5.624 mm to 6.327 mm and the eccentric radius N is in the range of 10.80 mm to 21.65 mm, It was confirmed that the ripple rate was as good as 0.6% or less. When the shape of the rotor magnet 23 is set in this way, torque unevenness is suppressed and the ripple rate can be reduced.
Similarly, when the outer diameter D of the stator 10 is set to 70 mm and 80 mm, the magnetic pole width M is in the range of 5.624 mm to 6.327 mm, and the eccentric radius N is 10.80 mm to 21.21 mm. It was confirmed that the ripple rate can be 1.0% or less when it is within the range of 65 mm.

  As described above, by setting the combination of the magnetic pole width M and the eccentric radius N to an appropriate range, the torque unevenness can be extremely reduced when the motor 1 is operated. In addition, by applying the motor 1 with a reduced ripple rate to EPS, for example, a smoother operational feeling can be given to the driver.

Next, the outer diameter D of the stator 10 is set to 76 mm, and the outer diameter R of the rotor 20 is set to 39.98 mm, 42.56 mm, 45.98 mm, 49.40 mm, 57.00 mm, 60.80 mm. The number of magnetic poles was 20, and the number of slots was 18). At this time, in the motor 1 of each dimension setting, the gap (air gap) between the tip of the tooth 13 and the outer peripheral surface of the rotor magnet 23 was set to be substantially the same. FIG. 6 shows the torque measurement result of each motor 1.
In each motor 1, the magnetic pole width M is set to 6.419 mm, and the eccentric radius N is set to 10.80 mm. This is the same setting as in the seventh embodiment. In Example 7, the ripple rate can be kept relatively low at 1.39%, and a torque value exceeding 5.5 (Nm) can be secured.

  From FIG. 6, when the outer diameter R of the rotor 20 is set to 49.40 mm, the torque value is maximum at 5.51 (Nm), and when the outer diameter R is set to 45.98 mm to 57.00 mm, the torque value is 5. It turns out that it becomes a favorable value exceeding 0 (Nm). However, it can be seen that the torque is less than 5.0 (Nm) when set to 42.56 mm or less or 60.80 mm or more. That is, when the outer diameter R is in the range of 45.98 mm to 57.00 mm, the amount of decrease from the maximum torque value can be suppressed to a relatively small value, and the torque value can be secured to 5.0 (Nm) or more. Is possible.

As described above, when the outer diameter D of the stator 10 is 76 mm, the motor 1 having a high torque can be obtained by appropriately selecting the outer diameter R of the rotor 20.
Even when the outer diameter D of the stator 10 is set to 70 mm and 80 mm, respectively, when the outer diameter R of the rotor 20 is in the range of 45.98 mm to 57.00 mm, the torque value is 5.0 (Nm). It was confirmed that it was a good value exceeding.

It is explanatory drawing which shows the structure of the brushless motor which concerns on one Embodiment of this invention. It is explanatory drawing of the stator and rotor of the brushless motor of FIG. It is principal part explanatory drawing of the stator and rotor of the brushless motor of FIG. It is a graph showing the ripple rate of the brushless motor which concerns on one Embodiment of this invention. It is a graph showing the ripple rate of the brushless motor which concerns on one Embodiment of this invention. It is a graph showing the torque with respect to the rotor outer diameter of the brushless motor which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Brushless motor, 10 ... Stator, 11 ... Stator core,
12 ... Outer core, 13 ... Teeth, 14 ... Winding, 20 ... Rotor,
21 ... Shaft 22 ... Spacer 23 ... Rotor magnet 23d ... Outer surface
23b, 23c ··· side surface, 23a ··· inner peripheral surface, 30 ··· housing,
31 ... Housing body, 32 ... End housing, 33, 34 ... Bearing,
35 ... Substrate, 36 ... Hall sensor, D ... Outer diameter, d ... Radius, M ... Magnetic pole width,
N: Eccentric radius, R: Outer diameter of rotor

Claims (4)

An inner rotor type comprising: a rotor having a plurality of rotor magnets disposed on an outer peripheral surface; and a stator having windings wound around teeth radially disposed to face the outer peripheral surface of the rotor magnet. Brushless motor
The rotor has 20 magnetic poles, the stator has an outer diameter in the range of 70 mm to 80 mm and the number of teeth is 18,
The rotor magnet has a circumferential width set in the range of 5.135 mm to 5.777 mm, and the outer circumferential surface of the outer circumferential surface facing the stator protrudes radially outward so that the central portion in the width direction protrudes radially outward. The brushless motor is characterized in that the radius is set in the range of 10.8 mm to 24.7 mm. An inner rotor type comprising: a rotor having a plurality of rotor magnets disposed on an outer peripheral surface; and a stator having windings wound around teeth radially disposed to face the outer peripheral surface of the rotor magnet. Brushless motor
The rotor has 16 magnetic poles, the stator has an outer diameter in the range of 70 mm to 80 mm and the number of teeth is 18.
The rotor magnet has a width in the circumferential direction set in a range of 5.624 mm to 6.327 mm, and the outer circumferential surface of the outer circumferential surface facing the stator protrudes radially outward. The brushless motor is characterized in that the radius is set in the range of 10.8 mm to 21.65 mm. An inner rotor type comprising: a rotor having a plurality of rotor magnets disposed on an outer peripheral surface; and a stator having windings wound around teeth radially disposed to face the outer peripheral surface of the rotor magnet. Brushless motor
The rotor has 20 magnetic poles and the stator has 18 teeth.
The brushless motor is characterized in that the outer diameter of the stator is set in a range of 70 mm to 80 mm, and the outer diameter of the rotor is set in a range of 45.98 mm to 57.0 mm. The rotor magnet has a circumferential width of approximately 6.419 mm, and a radius of the outer peripheral surface of 10.10 so that a central portion in the width direction of the outer peripheral surface facing the stator protrudes radially outward. The brushless motor according to claim 3, wherein the brushless motor is set to 8 mm.

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