Brushless motor device and steering device

Abstract

A brushless motor device (100) comprises: a shaft (101); a rotor (102) in which a prescribed number p of magnetic poles are alternately disposed; a slotted stator (103) which has a prescribed number s of slots in which a winding is accommodated; and a case (104) which accommodates these and which is provided with a fastening part for fastening to a housing, wherein when the greatest common divisor of the number s of slots and the number p of poles is a circular mode order m, the number of fastening points (FP) of the fastening part is an integer multiple of the circular mode order m or an integer multiple of a divisor (excluding 1) of the circular mode order m.

Description

Brushless motor device and steering device

[0001] The present invention relates to a brushless motor device and a steering device equipped with the brushless motor device, and more particularly to a fastening structure thereof.

[0002] An example of a technology for suppressing the transmission of vibrations from a motor (rotating electric machine) is disclosed in Patent Document 1. According to Patent Document 1, the transmission of vibrations to the mounted body is suppressed by positioning the mounting portion of the motor holder at a position that becomes a node of the vibration mode.

[0003] Japanese Patent Application Laid-Open No. 2017-229214

[0004] The motor device disclosed in Patent Document 1 is a technology that focuses on lowering the vibration transmission gain in order to reduce vibration and noise. Therefore, it only has a suppression effect for a specific frequency (the natural frequency of a specific vibration mode), and is unable to achieve a suppression effect that is independent of frequency.

[0005] An object of the present invention is to provide a brushless motor device that has the effect of reducing vibration and operating noise regardless of frequency.

[0006] As a result of extensive research, the inventors have discovered that the excitation force itself can be reduced by adjusting the number of fastening points and the phase relationship between those fastening points, and have completed the present invention based on this finding.

[0007] The present disclosure will be described below.

[0008] According to the present disclosure, there is provided a brushless motor device comprising: a shaft; a rotor that is arranged coaxially with the shaft and holds a predetermined number of alternating south and north pole magnets on its outer periphery; a slot stator that has a predetermined number of slots that can accommodate windings and in which the shaft and rotor are arranged; and a case that houses the shaft, the rotor, and the slot stator and is provided with a fastening part that has multiple fastening points that are fastened to a housing, wherein when the greatest common divisor of the number of slots in the slot stator and the number of poles is taken as a circular mode order, the number of fastening points of the fastening part is an integer multiple of the circular mode order or an integer multiple of a divisor (excluding 1) of the circular mode order.

[0009] According to the present disclosure, it is possible to provide a brushless motor device that has the effect of reducing vibration and operating noise regardless of frequency.

[0010] 1 is a partially cutaway perspective view illustrating the appearance of a brushless motor device according to an embodiment of the present disclosure. FIG. 1 is a schematic cross-sectional view of the brushless motor device illustrated in FIG. 1 taken along the Y-Z plane. FIG. 2 is a schematic configuration diagram illustrating a cross section along line II of a brushless motor in the brushless motor device illustrated in FIG. 3. FIG. 3 is a schematic cross-sectional view illustrating an example of windings in a slot stator of the brushless motor illustrated in FIG. 3. FIG. 4 is a schematic cross-sectional view of a brushless motor device for generally explaining the number and arrangement of fastening points in this embodiment. FIG. 5 is a schematic cross-sectional view illustrating the arrangement of fastening points in a brushless motor device according to Example 1. FIG. 6 is a more detailed cross-sectional view of the brushless motor device according to Example 1. FIG. 7 is a schematic cross-sectional view illustrating the arrangement of fastening points in a brushless motor device according to Example 2. FIG. 8 is a more detailed cross-sectional view of the brushless motor device according to Example 2. FIG. 9 is a schematic cross-sectional view illustrating the arrangement of fastening points in a brushless motor device according to Example 3. FIG. 10 is a more detailed cross-sectional view of the brushless motor device according to Example 3. FIG. 11 is a schematic cross-sectional view illustrating the arrangement of fastening points in a brushless motor device according to Example 4. FIG. 12 is a more detailed cross-sectional view of the brushless motor device according to Example 4. FIG. 10 is a schematic cross-sectional view showing the arrangement of fastening points in a brushless motor device according to a fifth embodiment. FIG. 11 is a more detailed cross-sectional view of the brushless motor device according to the fifth embodiment. FIG. 12 is a schematic cross-sectional view showing the arrangement of fastening points in a brushless motor device according to a sixth embodiment. FIG. 13 is a more detailed cross-sectional view of the brushless motor device according to the sixth embodiment. FIG. 14 is a schematic cross-sectional view showing the arrangement of fastening points in a brushless motor device according to a seventh embodiment. FIG. 15 is a schematic cross-sectional view showing the arrangement of fastening points in a brushless motor device according to an eighth embodiment. FIG. 16 is a schematic cross-sectional view showing the arrangement of fastening points in a brushless motor device according to a ninth embodiment. FIG. 17 is a graph showing an example of the relationship between the number of fastening points and vibration value in a vibration mode (quadratic ring) of a brushless motor device. FIG. 18 is a graph showing the distribution of moment resultant forces in the X and Z directions in two-point fastening (A), three-point fastening (B) and four-point fastening (C) in a vibration mode (quadratic ring) of a brushless motor device.

[0011] An embodiment of the present invention will be described below with reference to the accompanying drawings. For convenience, the description will be based on the XYZ coordinate system, with the shaft direction of the brushless motor being the Y direction and the plane perpendicular to the shaft being the XZ plane. Furthermore, spatial comparison expressions such as "equal" and "same" and quantitative expressions such as "distance," "interval," and "angle" used in the following description include tolerances and should be interpreted in their substantial meaning for achieving the objectives of the present invention. Furthermore, the embodiment shown in the accompanying drawings is an example of the present invention, and the present invention is not limited to this embodiment.

[0012] 1. Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 4. A brushless motor device 100 according to this embodiment is mounted in a steering device, for example, as a drive source for electric power steering. The brushless motor device 100 according to this embodiment includes a shaft 101, a rotor 102 fixed to the shaft 101, a slot stator 103 having a cylindrical hollow portion that rotatably houses the rotor 102, and a case 104 that houses the shaft 101, the rotor 102, and the slot stator 103. The brushless motor of the brushless motor device 100 according to this embodiment is, for example, a concentrated winding three-phase brushless motor, in which the rotor 102 is an interior permanent magnet rotor and the slot stator 103 is a concentrated winding stator. For simplicity's sake, however, the windings of the slot stator 103 are not shown in FIGS. 1 to 3.

[0013] As illustrated in FIGS. 1 to 4 , the case 104 has a cylindrical shape with the shaft 101 as its central axis. The case 104 has multiple fastening portions 105, each of which has a fastening point FP. These multiple fastening points FP are located on a circumference equidistant from the shaft 101. The case 104 is fixed to the housing 200 at the multiple fastening points FP using any fastening means, such as screws. Specifically, in this embodiment, the fastening points FP are formed as holes through which screws are inserted. Note that the fastening points may be formed as threaded holes, stud bolts, or the like, in addition to insertion holes. The housing 200 is, for example, a gear housing for an EPS (Electric Power Steering). As will be described later, the number of fastening points FP and their phase relationship can provide a frequency-independent reduction effect on operating noise.

[0014] A slot stator 103 is fixedly disposed on the cylindrical inner wall of the case 104. The rotor 102 is disposed in a cylindrical hollow portion within the slot stator 103, and is supported by the case 104 so as to be rotatable about the shaft 101.

[0015] The rotor 102 is provided on its cylindrical outer periphery with a plurality of permanent magnets, namely, south pole magnets M, extending in the direction of the shaft 101. Ｓ and N-pole magnet M Ｎ Hereinafter, the number of poles of the rotor 102 will be referred to as p.

[0016] A plurality of slots SL, which extend in the direction of the shaft 101 and accommodate windings, are arranged at equal intervals on the inner peripheral wall of the slot stator 103. As shown in FIG. 4, the windings C are wound in a concentrated manner around the core between adjacent slots SL. Hereinafter, the number of slots in the slot stator 103 will be referred to as s. Note that a position detection means (such as a Hall element) for the rotor 102 is not shown for simplification.

[0017] In a motor with a p-pole, s-slot configuration, vibration occurs in a circular mode whose order is the greatest common divisor of the number of poles, p, and the number of slots, s. In the example of Figure 3, the number of poles, p, is 10, and the number of slots, s, is 12, so the greatest common divisor is 2, resulting in vibration in a second-order circular mode. In this embodiment, the number of fastening points, FP, is set to an integer multiple (an integer multiple of 1 or greater) of the greatest common divisor, 2, and they are positioned symmetrically about the shaft 101. This eliminates the resultant moment at each fastening point, reducing operating noise.

[0018] However, the 10-pole, 12-slot, concentrated winding, three-phase brushless motor shown in Figure 3 is merely an example, and this embodiment is not limited to this. According to this embodiment, the resultant force of the moment input to the fastening point can be made zero (substantially 0) regardless of the circular mode order. Below, a generalized number and arrangement of fastening points will be described with reference to Figure 5.

[0019] In FIG. 5, the line from the shaft 101 of the X axis to the left side of the paper (negative direction) is used as the reference line, and the angle in the clockwise direction from that reference line is represented by θ. If the greatest common divisor of the number of poles p and the number of slots s is m, then there are m fastening points FP １ ~FP ｍ are arranged at equal intervals on the circumference at a constant distance r from the center of the shaft 101. Therefore, any adjacent fastening points FP ｉ and FP ｉ＋１ The central angle between them is the same θc = 360° / m. In this example, the fastening point FP １ is positioned at an angle θ from the reference line.

[0020] Fastening point FP １ ~FP ｍ The resultant force M of the moment on the XZ plane at Ｘ and M Ｚ can be expressed by the following formulas, respectively.

[0021] Here, α is the phase of the excitation force of the circular mode order, the number of fastening points = the circular mode order = m, and the force A acting on each fastening point is

[0022] It can be expressed as:

[0023] The calculated values ​​of m are all 0, as can be seen by substituting m = 1, 2, 3, etc.

[0024] That is, the above equations (1) and (2) do not depend on the circular mode order m, the distance r, and the phase α of the excitation force.

[0025] From the above equations (1) and (2), the fastening point FP １ ~FP ｍ Resultant force M of the moment at Ｘ and M Ｚ are cancelled out and become zero regardless of the annular mode order and the phase α. Therefore, the number of fastening points FP is the same as the number of annular mode orders. １ ~FP ｍ are arranged at equal intervals on a circle of radius r, the resultant moment M Ｘ and M Ｚ is maintained at zero. Therefore, even if multiple sets of fastening points are arranged with a desired angle offset, the resultant moment force can be made zero, thereby increasing the fastening strength. In addition, the offset angle of multiple sets of fastening points can be set arbitrarily, improving the degree of freedom in layout.

[0026] There are two ways to arrange the multiple sets of fastening points: 1) Arrange the multiple sets of fastening points so that the central angles between all adjacent fastening points are equal. 2) Arrange the multiple sets of fastening points so that the central angles between any fastening point and its adjacent fastening points are different. Below, we will explain in detail using examples.

[0027] 2. Examples <Example 1> As shown in FIG. 6, when the greatest common divisor of the number of poles p and the number of slots s, that is, the circular mode order m=2, the same number (n=1 times) of fastening points FP １１ are on the circumference equidistant from the shaft 101 at a central angle θ １ = 360° / m = 180°. From the above formulas (1) and (2), when m = 2, a set of fastening points FP １１ Resultant moment M at Ｘ and M ＺThe respective forces and are cancelled out to zero, reducing vibration and operating noise. The configuration of the brushless motor device 100 according to the first embodiment is shown in FIG. 7. Note that a pair of fastening points FP １１ is on the X-axis for convenience's sake and does not limit the arrangement of the fastening points.

[0028] <Example 2> As illustrated in FIG. 8, a pair of fastening points FP shown in FIG. １１ In addition, another set of fastening points FP １２ Another set of fastening points FP １２ is a set of fastening points FP １１ angle θ ２ In other words, if the greatest common divisor of the number of poles p and the number of slots s is 2, then the number of fastening points FP is twice that (n=2). １１ and FP １２ are arranged equidistantly on the circumference of the shaft 101. That is, any adjacent fastening points have the same central angle θ ２ = 90°.

[0029] From the above equations (1) and (2), when the circular mode order m = 2, the fastening point FP １１ and FP １２ Resultant moment M at Ｘ and M Ｚ and are cancelled out to zero, reducing vibration and operating noise. Furthermore, in this embodiment, the brushless motor device 100 is fastened to the housing 200 at four fastening points, which increases the fastening strength. In addition, the fastening points are arranged at the same central angle θ ２ 9 shows an example of the configuration of the brushless motor device 100 according to the second embodiment. １１ is on the X-axis, and another set of fastening points FP １２ is on the Z axis for convenience's sake and does not limit the arrangement of the fastening points.

[0030] <Example 3> As illustrated in FIG. 10, a pair of fastening points FP shown in FIG. １１ In addition, another set of fastening points FP １３Another set of fastening points FP １３ is a set of fastening points FP １１ angle θ ３ Therefore, the four fastening points FP １１ and FP １３ are arranged on a circumference equidistant from the shaft 101 so that the distance between the adjacent fastening points on both sides is different. In other words, the central angles θ between any fastening point and its adjacent fastening points on both sides are different. ３ Or θ ４ (=180°-θ ３ ) are placed.

[0031] From the above equations (1) and (2), when the circular mode order m = 2, the fastening point FP １１ and FP １３ Resultant moment M at Ｘ and M Ｚ are cancelled out to zero, reducing vibration and operating noise. Furthermore, in this embodiment, the brushless motor device 100 is fastened to the housing 200 at four fastening points, which increases the fastening strength. Furthermore, by setting different central angles θ between any fastening point and its adjacent fastening points, ３ Or θ ４ (=180°-θ ３ ) can be arranged, the degree of freedom in determining the layout of the four fastening points is improved. The configuration of the brushless motor device 100 according to the third embodiment is shown in FIG. 11. Note that one set of fastening points FP １１ is on the X-axis for convenience's sake and does not limit the arrangement of the fastening points.

[0032] In the second and third embodiments described above, the number of fastening points is twice the circular mode order m=2 (n=2), but this is not limiting. As can be seen from the above equations (1) and (2), the same effect can be achieved if the number of fastening points is an integer multiple n (n>2) of the circular mode order m=2 (2n). This arrangement of fastening points for a circular mode order m=2 can be applied to, for example, a brushless motor device with a 10-pole, 12-slot structure.

[0033] Conversely, if the divisors of the circular mode order m include 2 as will be described later, the same effects as those of the first to third embodiments can be obtained by providing fastening points whose number is an integer multiple of that number.

[0034] <Example 4> As shown in FIG. 12, when the greatest common divisor of the number of poles p and the number of slots s, that is, the circular mode order m=3, the same number (n=1 times) of fastening points FP ２１ are on the circumference equidistant from the shaft 101 at a central angle θ ５ = 360° / m = 120°. From the above formulas (1) and (2), when m = 3, a set of fastening points FP ３１ Resultant moment M at Ｘ and M Ｚ The respective forces and are cancelled out to zero, reducing vibration and operating noise. The configuration of the brushless motor device 100 according to the fourth embodiment is shown in FIG. 13. ２１ is on the X-axis for convenience's sake and does not limit the arrangement of the fastening points.

[0035] <Example 5> As illustrated in FIG. 14, a pair of fastening points FP shown in FIG. ２１ In addition, another set of fastening points FP ２２ Another set of fastening points FP ２２ is a set of fastening points FP ２１ angle θ ５ In other words, if the greatest common divisor of the number of poles p and the number of slots s is 3, then the number of fastening points FP is twice that (n=2). ２１ and FP ２２ are arranged equidistantly between adjacent fastening points on a circle equidistant from the shaft 101. That is, any adjacent fastening points are arranged at equal central angles of 60°.

[0036] From the above equations (1) and (2), when the circular mode order m = 3, the fastening point FP ２１ and FP ２２ Resultant moment M at Ｘ and M Ｚand are cancelled out to zero, reducing vibration and operating noise. Furthermore, in this embodiment, the brushless motor device 100 is fastened to the housing 200 at six fastening points, which increases the fastening strength. In addition, adjacent fastening points have the same central angle θ ２ 15 shows an example of the configuration of the brushless motor device 100 according to the fifth embodiment. ２１ and FP ２２ is on the X-axis for convenience's sake and does not limit the arrangement of the fastening points.

[0037] <Example 6> As illustrated in FIG. 16, a pair of fastening points FP shown in FIG. ２１ In addition, another set of fastening points FP ２３ Another set of fastening points FP ２３ is a set of fastening points FP ２１ angle θ ６ Therefore, six fastening points FP ２１ and FP ２３ are arranged on a circumference equidistant from the shaft 101 so that the distance between adjacent fastening points is different. In other words, a given fastening point and its adjacent fastening points on both sides have a different central angle θ ６ Or θ ７ (=120°-θ ６ ) are placed.

[0038] From the above equations (1) and (2), when the circular mode order m = 3, the fastening point FP ２１ and FP ２３ Resultant moment M at Ｘ and M Ｚ and are cancelled out to zero, reducing vibration and operating noise. Furthermore, in this embodiment, the brushless motor device 100 is fastened to the housing 200 at six fastening points, which increases the fastening strength. Furthermore, by setting different central angles θ between any fastening point and its adjacent fastening points, ６ Or θ ７ (=120°-θ ６) can be arranged, the degree of freedom in determining the layout of the six fastening points is improved. The configuration of the brushless motor device 100 according to the sixth embodiment is shown in FIG. 17. ２１ is on the X-axis for convenience's sake and does not limit the arrangement of the fastening points.

[0039] In the above-described fifth and sixth embodiments, the number of fastening points provided is twice the circular mode order m=3 (n=2), but this is not limiting. As can be seen from the above formulas (1) and (2), the same effect can be obtained as long as the number of fastening points is an integer multiple n (n>2) of the circular mode order m=3 (3n).

[0040] Conversely, if the divisors of the circular mode order m include 3, the same effects as those of the above-described embodiments 4 to 6 can be obtained by providing fastening points that are an integral multiple of that number. This embodiment can be applied to, for example, a brushless motor device with a 12-pole, 18-slot structure.

[0041] <Example 7> As shown in FIG. 18, when the greatest common divisor of the number of poles p and the number of slots s, that is, the circular mode order m=4, the same number (n=1 times) of fastening points FP ３１ are on the circumference equidistant from the shaft 101 at a central angle θ ２ From the above equations (1) and (2), when m=4, a set of fastening points FP ３１ Resultant moment M at Ｘ and the Z component M Ｚ are cancelled out to zero, reducing vibration and operating noise.

[0042] Four fastening points FP according to this embodiment ３１ The arrangement of the fastening points FP shown in FIG. １１ and FP １２ (Example 2) Therefore, as in Example 2, the fastening point FP ３１ Resultant moment M at Ｘ and M Ｚ are cancelled out to zero, reducing vibration and operating noise.

[0043] Furthermore, the divisor of the circular mode order m=4 in this embodiment is 2, which is the same as m=2 in the second embodiment. Therefore, an integer multiple of the divisor of the circular mode order m=4 in this embodiment also has the effect of reducing the operating noise, as described in the second embodiment. For example, as shown in FIG. 18, ３１ is the central angle θ ２ Not only when the fastening points are evenly arranged at a central angle θ = 90°, but also when the fastening points on both sides are arranged at a different central angle θ as shown in FIG. ３ Or θ ４ Even when the actuator is arranged in this manner, the same effect of reducing vibration and operating noise can be achieved.

[0044] <Embodiment 8> As illustrated in FIG. 19, a pair of fastening points FP shown in FIG. ３１ In addition, another set of fastening points FP ３２ Another set of fastening points FP ３２ is a set of fastening points FP ３１ angle θ ８ The angle θ ８ is θ ２ / 2 or any other angle. Therefore, there are eight fastening points FP ３１ and FP ３２ are arranged on a circumference equidistant from the shaft 101 so that the distance between any fastening point and its adjacent fastening points is the same or different. In other words, any fastening point and its adjacent fastening points are arranged at the same central angle θ ８ Or a different central angle θ ８ Or θ ９ (=90°-θ ８ ) are placed.

[0045] From the above equations (1) and (2), when the circular mode order m = 4, the fastening point FP ３１ and FP ３２ Resultant moment M at Ｘ and M Ｚ are cancelled out to zero, reducing vibration and operating noise. Furthermore, in this embodiment, the brushless motor device 100 is fastened to the housing 200 at eight fastening points, which increases the fastening strength. The fastening points on both sides have the same central angle θ ８If there is a central angle θ, the motor can be fixed with an appropriate fastening force and airtightness can be ensured. ８ Or θ ９ In this case, the degree of freedom in determining the layout of the eight fastening points is improved.

[0046] In this embodiment, the number of fastening points is twice (n=2) the circular mode order m=4, but this is not limiting. As can be seen from the above formulas (1) and (2), the same effect can be obtained if the number of fastening points is an integer multiple n (n>2) of the circular mode order m=4 (4n).

[0047] Conversely, if the divisors of the circular mode order m include 4, the same effect as in this embodiment can be obtained by providing fastening points equal to an integer multiple of that number. This embodiment can be applied to, for example, a brushless motor device with an 8-pole, 48-slot structure.

[0048] Ninth Embodiment In the first to eighth embodiments described above, the fastening point FP is provided on the outside of the bottom of the case 104, but the present invention is not limited to this.

[0049] As shown in FIG. 20, the plurality of fastening points FP shown in the above-described embodiment ４ The fastening portion 105 may be provided on the inside of the bottom of the case 104. This ensures an appropriate fastening force and also saves space for providing the fastening portion 105.

[0050] 3. Effects As described above, if the greatest common divisor of the number of slots s and the number of poles p is the circular mode order m, the number of fastening points FP is set to an integer multiple of m or an integer multiple of a divisor of m (excluding 1). This cancels out the resultant force of the moments input to the fastening points, making them essentially zero, thereby achieving the effect of reducing vibration and operating noise over a wide range of motor rotation speeds (frequencies).

[0051] 21 shows the results of measuring the operating noise level when vibrating in a vibration mode with a circular mode order m = 2, for each of the numbers of fastening points: 2, 3, and 4. For the two-point fastening according to this embodiment and its multiple, the four-point fastening, the vibration values ​​(dB) are significantly lower than those for the three-point fastening across all frequencies. At a frequency of 370 Hz, the vibration values ​​for the two-point and four-point fastenings were found to be approximately 1 / 8 to 1 / 30 of those for the three-point fastening.

[0052] Figure 22 is a graph showing the distribution of moment resultant forces simulated for 2, 3, and 4 fastening points when the vibration direction is changed in the range of 0° to 150° in a vibration mode with a circular mode order m = 2. In the two-point fastening shown in Figure 22(A), the moment resultant forces in the X and Z directions are zero, and in the four-point fastening shown in Figure 22(C), the moment resultant forces in the X and Z directions are also almost zero. In contrast, in the three-point fastening shown in Figure 22(B), the moment resultant forces in the X and Z directions are widely dispersed. Therefore, it can be seen that in the three-point fastening case, the moments are not canceled out and a circular motion component remains.

[0053] 4. Summary The brushless motor device according to the present invention described above will be summarized below.

[0054] 1 to 4, the brushless motor device 100 includes a shaft 101 and a south pole magnet M Ｓ and N-pole magnet M Ｎ The rotor 102 has a predetermined number of alternating poles, and is coaxial with the shaft 101; a slotted stator 103 has a predetermined number of slots in which windings C can be accommodated; and a case 104 that accommodates the shaft 101, the rotor 102, and the slotted stator 103 and has a fastening portion 105 that fastens the shaft 101, the rotor 102, and the slotted stator 103 to the housing 200.

[0055] See Figures 6 to 19. If the greatest common divisor of the number of slots and the number of poles is the annular mode order m, the number of fastening points FP of the fastening portion is an integer multiple of the annular mode order m or an integer multiple of a divisor (excluding 1) of the annular mode order m. Figure 6 illustrates a case where the number of fastening points FP is 1 x m = 2 (Example 1), while Figures 8 to 11 illustrate a case where the number of fastening points FP is 2 x m = 2 (Examples 2 and 3). Figures 12 to 17 illustrate a case where the number of fastening points FP is 1 x m = 3 (Example 4) and 2 x m = 3 (Examples 5 and 6). Figure 18 illustrates a case where the number of fastening points FP is 1 x m = 4 (Example 7), and Figure 19 illustrates a case where the number of fastening points FP is 2 x m = 4 (Example 8).

[0056] 21 and 22. By setting the number of fastening points FP to an integer multiple of the circular mode order m or an integer multiple of a divisor of m (excluding 1), the resultant force of the moments input to the fastening points is canceled out and becomes essentially zero, making it possible to suppress vibration over a wide range of motor rotation speeds (frequencies) and reduce operating noise.

[0057] See Figures 6, 12, and 18. Secondly, in first brushless motor device 100, when the number of fastening points FP is 1 (the same number) as the circular mode order m, the distance r between each fastening point and the center of shaft 101 is equal, and the central angle between any adjacent fastening points with shaft 101 as the center is equal.

[0058] The resultant force of the moment input to the fastening point FP is cancelled out and becomes essentially zero, thereby reducing vibration and operating noise over a wide range of motor rotation speeds (frequencies).

[0059] See Figures 8, 10, 14, 16, and 19. Thirdly, in first brushless motor device 100, when the number of fastening points FP is n times the circular mode order m (n is a positive integer of 2 or greater), the sets of fastening points that increase with each increment of integer value n by 1 have the same distance between each fastening point of the set and the center of shaft 101, and the same central angle between adjacent fastening points in the set about shaft 101.

[0060] The resultant force of the moment input to the fastening point FP is canceled out and becomes essentially zero, reducing vibration and operating noise over a wide range of motor rotation speeds (frequencies).Furthermore, by providing multiple sets of fastening points, the fastening strength can be improved.

[0061] See Figures 8 and 14. Fourth, in the third brushless motor device 100, the central angles between any adjacent fastening points are equal.

[0062] By providing multiple sets of fastening points evenly, the fastening strength can be improved and airtightness can be ensured.

[0063] See Figures 10, 16 and 19. Fifthly, in the third brushless motor device 100, the central angle between any given fastening point and its adjacent fastening points on both sides is different.

[0064] Fastening points can be provided at different central angles, improving the degree of freedom in the layout of fastening points.

[0065] See Figures 6, 8, 12, and 18. Sixth, in first brushless motor device 100, when the number of fastening points FP is 1 times a divisor of the circular mode order number m, the distance between each fastening point and the center of shaft 101 is equal, and the central angle between any adjacent fastening points about shaft 101 is equal.

[0066] The resultant force of the moment input to the fastening point FP is cancelled out and becomes essentially zero, thereby reducing vibration and operating noise over a wide range of motor rotation speeds (frequencies).

[0067] See Figures 6 to 19. Seventh, in first brushless motor device 100, when the number of fastening points FP is n times a divisor of the circular mode order m (n is a positive integer of 2 or greater), the sets of fastening points that increase with each increment of integer value n by 1 have the same distance between each fastening point of the set and the center of shaft 101, and the same central angle between adjacent fastening points in the set about shaft 101.

[0068] The resultant force of the moment input to the fastening point FP is canceled out and becomes essentially zero, reducing vibration and operating noise over a wide range of motor rotation speeds (frequencies).Furthermore, by providing multiple sets of fastening points, the fastening strength can be improved.

[0069] See Figures 6, 8, 12, 14 and 18. Eighth, in the seventh brushless motor device 100, the central angles between any adjacent fastening points are equal.

[0070] By providing multiple sets of fastening points evenly, the fastening strength can be improved and airtightness can be ensured.

[0071] See Figures 10, 16, and 19. Ninthly, in the seventh brushless motor device 100, the central angle between any given fastening point and its adjacent fastening points on both sides is different.

[0072] Fastening points can be provided at different central angles, improving the degree of freedom in the layout of fastening points.

[0073] 1 to 19. In any one of the first to ninth brushless motor devices 100, the fastening point FP is located outside the cylindrical portion of the case 104.

[0074] It can be fastened with the appropriate fastening force, ensuring airtightness.

[0075] 20, in any one of the first to ninth brushless motor devices 100, the fastening point FP is located inside the cylindrical portion of the case 104.

[0076] It can be fastened with the appropriate fastening force to ensure airtightness. Furthermore, the fastening part is located inside the cylindrical part, which saves space when installing the motor.

[0077] The brushless motor device according to the present invention is not limited to the above-described embodiment and example, as long as the functions and effects of the present invention are achieved.

[0078] The brushless motor device according to the present invention is suitable for, for example, a 10-pole, 12-slot or 8-pole, 12-slot motor for EPS.

[0079] REFERENCE SIGNS LIST 100...Brushless motor device 101...Shaft 102...Rotor 103...Slot stator 104...Case 105...Fastening portion 200...Housing FP...Fastening point M...Permanent magnet S...Slot

Claims

1. A brushless motor device comprising: a shaft; a rotor arranged coaxially with the shaft and having a predetermined number of alternating south and north pole magnets on its outer periphery; a slot stator having a predetermined number of slots to accommodate windings, and in which the shaft and rotor are arranged; and a case that houses the shaft, the rotor, and the slot stator, and is provided with a fastening part having a plurality of fastening points that are fastened to a housing, wherein, when the greatest common divisor of the number of slots in the slot stator and the number of poles of the rotor is defined as a circular mode order, the number of fastening points of the fastening part is an integer multiple of the circular mode order or an integer multiple of a divisor (excluding 1) of the circular mode order.

2. A brushless motor device as described in claim 1, characterized in that when the number of fastening points is 1 times the number of circular mode orders, the distance between each fastening point and the center of the shaft is equal, and the central angle between any adjacent fastening points around the shaft is equal.

3. A brushless motor device as described in claim 1, characterized in that when the number of fastening points is n times the order of the circular mode (n is a positive integer of 2 or greater), the sets of fastening points that increase with each increment of the integer value n by 1 have equal distances between each fastening point of the set and the center of the shaft, and equal central angles between adjacent fastening points in the set about the shaft.

4. A brushless motor device according to claim 3, wherein the central angles between any two adjacent fastening points are equal.

5. A brushless motor device according to claim 3, wherein the central angle between any one fastening point and its adjacent fastening points on both sides is different.

6. A brushless motor device as described in claim 1, characterized in that when the number of fastening points is 1 times a divisor of the circular mode order, the distance between each fastening point and the center of the shaft is equal, and the central angle between any adjacent fastening points around the shaft is equal.

7. A brushless motor device as described in claim 1, characterized in that when the number of fastening points is n times a divisor of the circular mode order (n is a positive integer of 2 or greater), the sets of fastening points that increase with each increment of the integer value n by 1 have equal distances between each fastening point of the set and the center of the shaft, and equal central angles between adjacent fastening points in the set about the shaft.

8. The brushless motor device according to claim 7, wherein the central angles between any two adjacent fastening points are equal.

9. A brushless motor device according to claim 7, wherein the central angle between any one fastening point and its adjacent fastening points on both sides is different.

10. A brushless motor device according to any one of claims 1 to 9, wherein the fastening point is located outside the cylindrical portion of the case.

11. A brushless motor device according to any one of claims 1 to 9, wherein the fastening point is located inside the cylindrical portion of the case.

12. A brushless motor device according to any one of claims 1 to 9, wherein the slot stator is a concentrated winding stator.

13. A steering device equipped with the brushless motor device according to claim 1.

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