JP2007252096A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a motor in size and to cut down on the cost of a material by contracting the diameter of a sensor magnet in the brushless motor that uses a two-pole Hall IC. <P>SOLUTION: In the brushless motor using the two-pole Hall IC 69 arranged with two pieces of Hall elements Q1, Q2 at a prescribed interval, the Hall elements Q1, Q2 are arranged on circumferences at difference distances from the rotation center of a rotor, respectively. The Hall IC 69 is arranged on a board 24 in a state that a segment L connecting the magnetism detection elements Q1, Q2 is inclined with respect to a connecting line T in the center M of a circle that passes the center M of the magnetism detection elements Q1, Q2. An angle θ1 between the segment L and the connecting line T is set in a range of 30° to 60°. By this, a circumferential directional distance Y between the magnetism detection elements is shortened compared with a conventional brushless motor, and the diameter of the sensor magnet 19 can be contracted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brushless motor, and more particularly, to an arrangement of a magnetic detection element used for detecting a rotor rotational position of the brushless motor.

  In general, in a brushless motor, a change in the magnetic pole of a magnet provided on the rotor side is detected by a magnetic detection element to detect the rotational position of the rotor, and based on the detected rotor rotational position, the stator side coil is sequentially excited to rotate the rotor. Driven. FIG. 9 is a cross-sectional view showing a configuration of a conventional brushless motor. As shown in FIG. 9, the brushless motor 51 (hereinafter abbreviated as “motor 51”) includes a motor unit 52 and a sensor unit 53. The motor unit 52 includes a rotor 54 and a stator 55, and a sensor unit 53. Are provided with Hall ICs 68 and 69, respectively.

  The rotor 54 includes a rotor core 57 fixed to the rotor shaft 56 and a magnet holder 58 attached to the outer periphery of the rotor core 57. A rotor magnet 59 is attached to the magnet holder 58, and the rotor magnet 59 is bonded and fixed to the outer periphery of the rotor core 57. The rotor shaft 56 is rotatably supported by bearings 61a and 61b. The stator 55 includes a stator core 63 around which the winding 62 is wound, and a metal housing 64 that houses the stator core 63. The housing 64 has a bottomed cylindrical shape, and a bracket 65 of the sensor unit 53 is fixed to an opening end thereof.

  The sensor unit 53 has a double multipole sensor structure, and is provided with ring-shaped sensor magnets 66 and 67 and Hall ICs 68 and 69. 10 and 10 are explanatory diagrams showing the configuration of the sensor unit 53. FIG. The sensor magnets 66 and 67 are attached to a disk-shaped magnet plate 71 fixed to the rotor shaft 56 and rotate together with the rotor shaft 56. On the other hand, the Hall ICs 68 and 69 are placed on the substrate 72 fixed in the bracket 65 and are arranged on the substrate so as to face the sensor magnets 66 and 67. The sensor magnet 66 has a smaller diameter than the sensor magnet 67 and is disposed concentrically on the inner peripheral side of the sensor magnet 67. The sensor magnet 66 is magnetized to have the same number of poles (six poles) as the rotor magnet 59, and the sensor magnet 67 is finer than the sensor magnet 66 and is magnetized to 72 poles at a 5 ° pitch.

Three Hall ICs 68 (68a to 68c) are provided at equal intervals along the circumferential direction, and sequentially output detection signals as the sensor magnet 66 rotates. The Hall IC 69 (magnetic detection device) uses a two-pole Hall IC in which two Hall elements (Q1, Q2: magnetic detection elements) are arranged in one IC package, and each Hall element Q1, A detection signal is also output from Q2 as the sensor magnet 67 rotates. In this case, a detection signal corresponding to the sensor magnet 66 with 6 poles and 60 ° pitch is obtained from the Hall IC 68. On the other hand, a detection signal corresponding to the sensor magnet 67 having 72 poles and 5 ° pitch is obtained from the Hall IC 69. That is, the Hall IC 69 outputs a signal obtained by sensing the rotational position more finely. Accordingly, in the motor 51, the rotational position of the rotor 54 is detected by interpolating the detection signal of the Hall IC 68 using the detection signal of the Hall IC 69 while grasping the rotational position of the rotor 54 from the detection signal of the Hall IC 68. And the timing of energizing the winding 62 is controlled.
U.S. Patent No. 6826499

  However, in the 2-pole Hall IC 69, the sensor pitch between the Hall elements Q1, Q2 is determined in advance (a commercially available 2-pole Hall IC is approximately 1 mm). For this reason, when the Hall IC 69 is arranged so that both Hall elements Q1 and Q2 are on the same diameter along the circumferential direction, there is a problem that the outer diameter of the sensor magnet 67 is restricted and the magnet diameter cannot be made smaller than a certain value. . FIG. 12 is an explanatory diagram showing the positional relationship between the Hall elements Q1 and Q2. Here, the output signals from the Hall elements Q1 and Q2 are preferably out of phase with each other in order to detect the rotational direction, rotational speed, and the like. Therefore, as shown in FIG. 11, when the detection signal is output in a form shifted from the Hall elements Q1 and Q2 by a half cycle, the magnetic poles of the sensor magnet 67 have a pitch of 5 °, so that the distance between Q1 and Q2 is 2.5. It is necessary to set the interval. Therefore, when the sensor pitch is 1 mm as described above, the sensor magnet 67 needs to have a diameter of 2.5 ° or more corresponding to 1 mm.

  That is, in order to satisfy the above-described conditions, if the pitch circle diameter of each element Q1, Q2 is D1, πD1 × (2.5 / 360) = 1 mm, so D1 = 45.9 mm. Further, considering the size and detection accuracy of the elements Q1 and Q2, the outer diameter of the sensor magnet 67 is not sufficient with the pitch circle diameter D1, and a width of about 2 mm is required on the outer diameter side of D1, and the magnet diameter needs to be 50 mm. Become. This hinders miniaturization of the motor and limits the layout of the sensor unit 53, resulting in a low degree of design freedom. Further, since the diameter of the sensor magnet 67 is increased, the material cost is increased accordingly, which is a cause of the increase in cost. In particular, when a rare earth magnet is used for the sensor magnet 67, the cost required for the magnet is large, and improvement thereof has been demanded. When the magnetizing pitch of the sensor magnet 67 is other than 5 °, the value of D1 also changes accordingly.

  An object of the present invention is to reduce the diameter of a sensor magnet in a brushless motor using a two-pole Hall IC, thereby reducing the size of the motor and reducing material costs.

  In the brushless motor of the present invention, a stator including armature windings, a rotor including a permanent magnet and rotatably disposed inside or outside the stator, and a plurality of magnetic poles are disposed along the circumferential direction. A brushless motor comprising: a sensor magnet that rotates together with the rotor; and a magnetic detection device in which at least two magnetic detection elements that output detection signals in accordance with a change in polarity of the sensor magnet are arranged at predetermined intervals. The magnetic detection device is disposed at a predetermined interval with respect to the axial end surface of the sensor magnet, and the magnetic detection elements are respectively disposed on the circumferences at different distances from the rotation center of the rotor. Features.

  In the brushless motor, the conventional brushless motor in which at least two magnetic detection elements are arranged on the circumferences at different distances from the rotation center of the rotor, and the magnetic detection elements are arranged on the same circumference. In comparison, the circumferential distance between the magnetic detection elements is shortened. Therefore, when using sensor magnets having the same magnetization pitch, the magnetic detection element can be arranged closer to the center of rotation. For this reason, the diameter of the sensor magnet can be reduced, the layout of the brushless motor can be improved, and the magnet material cost can be reduced. Further, when using sensor magnets having the same diameter, a sensor magnet having a smaller magnetization pitch can be used, and the resolution of detecting the rotor rotational position can be increased without changing the magnet diameter.

  Another brushless motor according to the present invention includes a stator having armature windings, a rotor having a permanent magnet and rotatably arranged inside or outside the stator, and a plurality of magnetic poles arranged in the circumferential direction. A brushless motor comprising: a sensor magnet that rotates together with the rotor; and a magnetic detection device in which at least two magnetic detection elements that output detection signals in accordance with a change in polarity of the sensor magnet are arranged at predetermined intervals. The magnetic detection device is disposed at a predetermined interval with respect to the outer peripheral surface of the sensor magnet, and the magnetic detection elements are respectively disposed on different rotation planes around the rotation center of the rotor. It is characterized by that.

  In the brushless motor, the conventional brushless motor in which at least two magnetic detection elements are arranged on different rotation planes around the rotation center of the rotor, and the magnetic detection elements are arranged on the same plane. In comparison, the circumferential distance between the magnetic detection elements is shortened. Therefore, when using a sensor magnet having the same diameter, a sensor magnet having a smaller magnetization pitch can be used, and the resolution of detecting the rotor rotational position can be increased without changing the magnet diameter. Even when sensor magnets with the same magnetization pitch are used, the magnetism detection element can be placed closer to the center of rotation, so the sensor magnet can be reduced in diameter to improve the layout of brushless motors and reduce magnet material costs. It becomes possible.

  Another brushless motor according to the present invention includes a stator having armature windings, a rotor having a permanent magnet and rotatably arranged inside or outside the stator, and a plurality of magnetic poles arranged in the circumferential direction. The brushless motor includes a sensor magnet that rotates together with the rotor, and a magnetic detection device in which two magnetic detection elements that output detection signals according to a change in polarity of the sensor magnet are arranged at a predetermined interval. A line segment L connecting the two magnetic detection elements Q1 and Q2 with respect to a tangent line T at the midpoint M of a circle centered on the rotation center O and passing through the midpoint M of the magnetic detection elements Q1 and Q2. A brushless motor, wherein the magnetic detection device is arranged in an inclined state.

  In this case, the angle θ1 between the line segment L and the tangent line T at the midpoint M may be set to 30 ° to 60 °, preferably 45 ° ± 10 °, more preferably 45 ° ± 5 °. good. Further, the magnetic detection device may be arranged on the axial direction side of the sensor magnet, and may be opposed to the axial end surface of the sensor magnet with a predetermined interval. Further, the magnetic detection device may be disposed on the outer side in the radial direction of the sensor magnet and may be opposed to the outer peripheral surface of the sensor magnet with a predetermined interval.

  In the brushless motor, the conventional magnetic detection device is arranged with the line segment L inclined with respect to the tangent line T at the midpoint M of the circle passing through the midpoint M of the magnetic detection elements Q1 and Q2. Compared with the brushless motor, the circumferential distance between the magnetic detection elements is shortened. Therefore, when using sensor magnets having the same magnetization pitch, the magnetic detection element can be arranged closer to the center of rotation. For this reason, the diameter of the sensor magnet can be reduced, the layout of the brushless motor can be improved, and the magnet material cost can be reduced. Further, when using sensor magnets having the same diameter, a sensor magnet having a smaller magnetization pitch can be used, and the resolution of detecting the rotor rotational position can be increased without changing the magnet diameter.

  Still another brushless motor according to the present invention includes a stator having an armature winding, a rotor having a permanent magnet and rotatably arranged inside or outside the stator, and a plurality of magnetic poles along the circumferential direction. A brushless motor having a sensor magnet arranged and rotating together with the rotor, and a magnetic detection device having two magnetic detection elements that output detection signals in accordance with a change in polarity of the sensor magnet at predetermined intervals. An angle θ2 between a line segment L connecting the two magnetic detection elements Q1 and Q2 and a center line N2 passing through the center M of the magnetic detection elements Q1 and Q2 and the rotation center O is 30 ° to 60 °. The magnetic detection device is arranged in a state where the angle is. In this case, θ2 may be set to 45 ° ± 10 °, more preferably 45 ° ± 5 °.

  In the brushless motor, the magnetic detection device is operated in a state where the angle θ2 between the line segment L and the center line N2 passing through the center M of the magnetic detection elements Q1 and Q2 and the rotation center O is 30 ° to 60 °. By arranging, the circumferential distance between the magnetic detection elements is shortened as compared with the conventional brushless motor. Therefore, when using sensor magnets having the same magnetization pitch, the magnetic detection element can be arranged closer to the center of rotation. For this reason, the diameter of the sensor magnet can be reduced, the layout of the brushless motor can be improved, and the magnet material cost can be reduced. Further, when using sensor magnets having the same diameter, a sensor magnet having a smaller magnetization pitch can be used, and the resolution of detecting the rotor rotational position can be increased without changing the magnet diameter.

  According to the brushless motor of the present invention, a stator having armature windings, a rotor having permanent magnets and rotatably arranged inside or outside the stator, and a plurality of magnetic poles are arranged along the circumferential direction. A brushless motor having a sensor magnet that rotates together with the rotor and a magnetic detection device in which at least two magnetic detection elements that output a detection signal according to a change in polarity of the sensor magnet are arranged at a predetermined interval. Since the detection device is arranged at a predetermined interval with respect to the axial end surface of the sensor magnet, and the magnetic detection elements are arranged on different circumferences from the rotation center of the rotor, the magnetic detection elements are arranged on the same circumference. Compared to a conventional brushless motor, the circumferential distance between the magnetic detection elements can be shortened. For this reason, when using sensor magnets having the same magnetization pitch, the magnetic detection element can be arranged closer to the rotation center. Therefore, the diameter of the sensor magnet can be further reduced, and the layout of the brushless motor can be improved and the magnet material cost can be reduced. Further, when using a sensor magnet having the same diameter, a sensor magnet having a smaller magnetization pitch can be used, and the resolution of detecting the rotor rotational position can be improved without changing the magnet diameter.

  According to another brushless motor of the present invention, a stator having an armature winding, a rotor having a permanent magnet and rotatably disposed inside or outside the stator, and a plurality of magnetic poles along the circumferential direction. A brushless motor having a sensor magnet arranged and rotated together with a rotor, and a magnetic detection device having at least two magnetic detection elements that output detection signals in accordance with a change in polarity of the sensor magnet at predetermined intervals. Since the magnetic detection device is arranged at a predetermined interval with respect to the outer peripheral surface of the sensor magnet, and the magnetic detection elements are arranged on different rotation planes around the rotation center of the rotor, the magnetic detection elements are arranged on the same plane. As compared with the conventional brushless motor arranged in the above, the circumferential distance between the magnetic detection elements can be shortened. For this reason, when a sensor magnet having the same diameter is used, a sensor magnet having a smaller magnetization pitch can be used, and the resolution of detecting the rotor rotational position can be improved without changing the magnet diameter. In addition, when using sensor magnets with the same magnetization pitch, it is possible to place the magnetism detection element closer to the rotation center side, the sensor magnet can be made smaller in diameter, improving the layout of the brushless motor, It becomes possible to reduce the magnet material cost.

  According to another brushless motor of the present invention, a stator having an armature winding, a rotor having a permanent magnet and rotatably disposed inside or outside the stator, and a plurality of magnetic poles along the circumferential direction. A brushless motor having a sensor magnet arranged and rotated together with the rotor, and a magnetic detection device in which two magnetic detection elements that output a detection signal according to a change in polarity of the sensor magnet are arranged at a predetermined interval. Magnetization is performed in a state where the line segment L connecting the two magnetic detection elements Q1 and Q2 is inclined with respect to the tangent T at the midpoint M of the circle passing through the midpoint M of the magnetic detection elements Q1 and Q2 with the rotation center O as the center. Since the detection device is arranged, the circumferential distance between the magnetic detection elements can be shortened as compared with the conventional brushless motor. For this reason, when using sensor magnets having the same magnetization pitch, the magnetic detection element can be arranged closer to the rotation center. Therefore, the diameter of the sensor magnet can be further reduced, and the layout of the brushless motor can be improved and the magnet material cost can be reduced. Further, when using a sensor magnet having the same diameter, a sensor magnet having a smaller magnetization pitch can be used, and the resolution of detecting the rotor rotational position can be improved without changing the magnet diameter.

  According to still another brushless motor of the present invention, a stator having an armature winding, a rotor having a permanent magnet and rotatably disposed inside or outside the stator, and a plurality of magnetic poles along the circumferential direction A brushless motor comprising a sensor magnet that rotates together with the rotor and a magnetic detection device in which two magnetic detection elements that output detection signals in accordance with a change in polarity of the sensor magnet are arranged at predetermined intervals. In a state where the angle θ2 between the line segment L connecting the two magnetic detection elements Q1 and Q2 and the center line N2 passing through the midpoint M of the magnetic detection elements Q1 and Q2 and the rotation center O is 30 ° to 60 °. Since the magnetic detection device is arranged, the circumferential distance between the magnetic detection elements can be shortened as compared with the conventional brushless motor. For this reason, when using sensor magnets having the same magnetization pitch, the magnetic detection element can be arranged closer to the rotation center. Therefore, the diameter of the sensor magnet can be further reduced, and the layout of the brushless motor can be improved and the magnet material cost can be reduced. Further, when using a sensor magnet having the same diameter, a sensor magnet having a smaller magnetization pitch can be used, and the resolution of detecting the rotor rotational position can be improved without changing the magnet diameter.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a configuration of a brushless motor that is Embodiment 1 of the present invention. A brushless motor 1 (hereinafter abbreviated as “motor 1”) in FIG. 1 is used as a power source of a column assist type electric power steering device (EPS) and applies an operation assisting force to a steering shaft of an automobile. The motor 1 is attached to a speed reduction mechanism provided on the steering shaft, and the rotation of the motor 1 is transmitted to the steering shaft by being decelerated by the speed reduction mechanism.

  As shown in FIG. 1, the motor 1 is composed of a motor unit 2 and a sensor unit 3, similarly to the motor 51 of FIG. 9. The motor unit 2 is provided with a rotor 4 and a stator 5, and the motor 1 is an inner rotor type brushless motor in which the rotor 4 is disposed on the inner side and the stator 5 is disposed on the outer side. The stator 5 includes a housing 6, a stator core 7 fixed to the inner peripheral side of the housing 6, and a winding 8 wound around the stator core 7. The housing 6 is formed in a bottomed cylindrical shape with iron or the like, and a bracket 9 made of synthetic resin is attached to the opening thereof. The stator core 7 has a structure in which a large number of steel plates are laminated, and a plurality of teeth protrude from the inner peripheral side of the stator core 7.

  The rotor 4 is disposed inside the stator 5, and has a configuration in which the rotor shaft 11, the rotor core 12, and the rotor magnet 13 are arranged coaxially. A cylindrical rotor core 12 in which a large number of steel plates are laminated is attached to the outer periphery of the rotor shaft 11. A segment type rotor magnet 13 is disposed on the outer periphery of the rotor core 12. The rotor magnets 13 are attached to a magnet holder 14 fixed to the rotor shaft 11, and six rotor magnets 13 are arranged along the circumferential direction.

  One end of the rotor shaft 11 is rotatably supported by a bearing 15 a press-fitted into the bottom of the housing 6. The other end of the rotor shaft 11 is rotatably supported by a bearing 15 b attached to the bracket 9. A spline portion 16 is formed at an end portion (left end portion in FIG. 1) of the rotor shaft 11, and is attached to one end portion side of the joint 17. The other end of the joint 17 is connected to a worm shaft (not shown) of the speed reduction mechanism. A worm is formed on the worm shaft and meshes with a worm wheel attached to the steering shaft, whereby the rotation of the motor 1 is decelerated and transmitted to the steering shaft.

  FIG. 2 is an explanatory diagram showing the configuration of the sensor unit 3. As shown in FIG. 2, the sensor unit 3 also has a double multipolar sensor structure similar to the motor 51, and is provided with ring-shaped sensor magnets 18 and 19 and Hall ICs 21 and 22. The basic configuration of the sensor unit 3 is the same as that of the sensor unit 53 shown in FIG. 11, and the sensor magnets 18 and 19 are attached to a disk-shaped magnet plate 23 fixed to the rotor shaft 11. The Hall ICs 21 and 22 are disposed on the axial direction side of the sensor magnets 18 and 19, and face the axial end surfaces of the sensor magnets 18 and 19 with a predetermined interval. As a result, the sensor magnets 18 and 19 rotate so as to face the Hall ICs 21 and 22 with a predetermined clearance as the rotor 4 rotates.

  On the other hand, the Hall ICs 21 and 22 are placed on a substrate 24 fixed in the bracket 9, and are disposed on the substrate so as to face the sensor magnets 18 and 19. The sensor magnet 18 is arranged concentrically on the inner peripheral side of the sensor magnet 19, is magnetized with the same number of poles (six poles) as the rotor magnet 13, and magnetic poles are arranged along the circumferential direction. The sensor magnet 19 is also provided with magnetic poles along the circumferential direction, but is finer than the sensor magnet 18 and is magnetized to 72 poles at a pitch of 5 °. However, as shown in FIG. 2, in the motor 1, unlike the motor 51 of FIG. 9, the Hall IC 22 is disposed obliquely with respect to the rotation direction of the sensor magnet 19, and the outer diameter of the sensor magnet 19 is 35 mm ( The motor 51 is 50 mm).

  Three Hall ICs 21 (21a to 21c) are provided at equal intervals along the circumferential direction, and sequentially output detection signals as the sensor magnet 18 rotates. The number of Hall ICs 21 is not limited to three and may be two. On the other hand, a two-pole Hall IC is used for the Hall IC 22 in the same manner as the motor 51 of FIG. 9, and detection signals are sent from the Hall elements Q1 and Q2 (magnetic detection elements) as the sensor magnet 19 rotates. Is output. When the rotor shaft 11 rotates, the sensor magnets 18 and 19 also rotate, and the rotation position detection signals are output from the Hall ICs 21 and 22. In the motor 1 as well as the motor 51, the rotational position of the rotor 4 is grasped by the detection signal of the Hall IC 21 and the energization timing for the winding 8 is controlled by using the detection signal of the Hall IC 22 to rotate the rotor 4. Let

  FIG. 3 is an explanatory diagram comparing the arrangement of the Hall ICs 22 and 69 of the motors 1 and 51. As described above, in the motor 1, the Hall IC 22 is disposed obliquely with respect to the rotation direction of the sensor magnet 19. In this case, in the motor 51, the hall elements Q1 and Q2 are arranged along the rotation direction of the sensor magnet 67 as shown in FIG. That is, the Hall elements Q1 and Q2 are arranged on the same circumference, and the line segment L connecting the Hall elements Q1 and Q2 and the tangent line T passing through the midpoint M of the Hall elements Q1 and Q2 coincide with each other, and the angle therebetween θ1 is 0 °. On the other hand, in the motor 1, the Hall IC 22 of the motor 51 is arranged in the form rotated in the X direction in the drawing. That is, the Hall elements Q1 and Q2 are respectively arranged on the circumferences having different diameters, and an angle θ1 between a line segment L connecting the Hall elements Q1 and Q2 and a tangent line T passing through the midpoint M of the Hall elements Q1 and Q2 is 45. It is °.

  On the other hand, when the arrangement of the Hall elements Q1 and Q2 in relation to the line segment L with respect to the center line N1 and N2 passing through the center M of the Hall elements Q1 and Q2 and the rotation center O and the line segment L, , Q2 is 90 ° (L and N1 are orthogonal) between the center point M of Q2 and the center line N1 passing through the rotation center O. On the other hand, in the motor 1, the angle θ2 between the line segment L connecting the Hall elements Q1 and Q2 and the center line N2 passing through the center M of the Hall elements Q1 and Q2 and the rotation center O is 45 °. . In this case, θ1 and θ2 are angles obtained by dividing the angle (90 °) between the tangent line T and the center line N (N1, N2) by the line segment L, and θ1 + θ2 = 90 °.

  Here, the Hall ICs 22 and 69 are the same as the IC, and the distance P between the Hall elements Q1 and Q2 does not change between the motor 1 and the motor 51 (P = 1 mm). When θ2 is 45 °, the center angle between the MUs is 1.25 degrees as shown in the enlarged view at the lower right of FIG. 3, so the MU can be regarded as a substantially straight line, and the distance between the MUs in the triangle MUQ2 S is S = MQ2 (P / 2 = 0.5 mm) × sin θ2 ′. Assuming that the distance between MUs is a straight line, θ2 ′ is also 45 °, so S = 0.5 × sin45 ° = 0.35 mm. Therefore, if the center is O and the diameter of a circle passing through M is D2, the magnetizing pitch of the sensor magnet 19 is 2.5 °, so that πD2 × (2.5 / 360) = 0.35 mm × 2 It becomes. Solving this for D2, D2 = (2S / π) × (360 / 2.5) = 32.1 mm. In other words, the diameter of the circle passing through M is 32.1 mm, and considering the position of element Q1 (positioned 0.35 mm outside diameter from D2) and the size of elements Q1 and Q2, the sensor magnet A suitable outer diameter of 19 is 35 mm.

  As described above, when the Hall IC 22 is arranged obliquely with respect to the rotation direction of the sensor magnet 19, the circumferential distance Y between the Hall elements Q1 and Q2 becomes smaller than that of the conventional motor 51 as shown in FIG. (Motor 51: P = 1 mm → Motor 1: about 2S = 0.7 mm). For this reason, when using a sensor magnet having the same magnetization pitch, the outer diameter of the sensor magnet can be reduced as Y decreases (50 mm → 35 mm). When the diameter of the sensor magnet is reduced, the layout of the sensor unit 3 is improved and the degree of freedom in design is increased. For example, as shown in FIG. 4, the sensor magnet 19 can be arranged on the motor unit 2 side (inside the bearing 15 b), and the motor can be shortened (the overall length can be shortened).

  In addition, with the miniaturization of the magnet, the material cost of the magnet can be reduced. When the size is changed from 50 mm to 35 mm, the material can be reduced by about 1/3. For this reason, the cost required for the magnet can be reduced. In particular, when a rare earth magnet is used, the effect of saving is great. Furthermore, since the diameter of the magnet is reduced, the inertia of the rotor 4 is reduced, and the motor performance is improved, for example, the control response is improved. In addition, the present invention can reduce the diameter of the sensor magnet by simply rearranging the Hall ICs 22 on the substrate 24 without any major design change, and does not increase the number of parts, man-hours, or the like.

  On the other hand, when the Hall IC 22 is disposed obliquely as described above, when a sensor magnet having the same diameter (diameter 50 mm) as in the conventional case is used, the pitch angle of the sensor portion becomes small. FIGS. 5A and 5B are explanatory views showing the sensor pitch in that case in comparison with the conventional configuration. FIG. 5A shows the case where the Hall IC 22 is inclined, and FIG. 5B shows the case of the conventional arrangement. . As shown in FIG. 5A, when the Hall IC 22 is arranged at a position having a diameter of 45.9 mm as in the prior art, the pitch angle is 1.5 ° when θ2 = 45 °, as described above. Therefore, the magnetization pitch of the sensor magnets 19 can be made finer (5 ° → 3 °) than the conventional arrangement shown in FIG. For this reason, the resolution can be increased without changing the diameter of the sensor magnet 19, and the detection accuracy of the rotor rotational position can be improved.

  FIG. 6 is a cross-sectional view showing a configuration of a brushless motor that is Embodiment 2 of the present invention. The brushless motor 25 in FIG. 6 (hereinafter abbreviated as “motor 25”) is also used as a power source for the EPS. The motor 25 is also composed of a motor unit 26 and a sensor unit 27. The motor unit 26 is provided with a rotor 28 and a stator 29. The stator 29 includes a housing 31, a stator core 32 fixed to the inner peripheral side of the housing 31, and a winding 33 wound around the stator core 32. The housing 31 is formed of a bottomed cylinder with iron or the like, and a synthetic resin bracket 34 is attached to the opening.

  The rotor 28 is disposed inside the stator 29, and has a configuration in which a rotor shaft 35, a rotor core 36, and a rotor magnet 37 are arranged coaxially. A rotor core 36 is attached to the outer periphery of the rotor shaft 35, and a rotor magnet 37 is disposed on the outer periphery of the rotor core 12. The rotor magnet 37 is attached to a magnet holder 38 fixed to the rotor shaft 35, and six rotor magnets 37 are arranged along the circumferential direction. A metal magnet cover 39 is attached to the outside of the rotor magnet 37.

  One end of the rotor shaft 35 is rotatably supported by a bearing 41 a fixed to the bottom of the housing 31. The other end of the rotor shaft 35 is rotatably supported by a bearing 41 b attached to the bracket 34. A spline portion 42 is formed at an end portion (left end portion in FIG. 6) of the rotor shaft 35, and a joint 43 is attached thereto. The other end of the joint 43 is connected to a worm shaft (not shown) of the speed reduction mechanism.

  FIG. 7 is an explanatory diagram showing the configuration of the sensor unit 27. As shown in FIG. 7, the sensor unit 27 also has a double multipolar sensor structure, and is provided with ring-shaped sensor magnets 44 and 45 and Hall ICs 46 and 47. The sensor magnets 44 and 45 are attached to a notch 38a formed at the left end of the magnet holder 38 in the drawing. The Hall ICs 46 and 47 are fixed to a sensor holder 48 attached to the bracket 34. As shown in FIG. 7, the sensor holder 48 is provided with arm portions 48a to 48c. The arm portions 48a and 48c each have one Hall IC 46a and 46c, and the arm portion 48b has a Hall IC 46b. Hall IC 47 is disposed.

  In the motor 25, unlike the motor 1 in FIG. 1, the sensor magnets 44 and 45 are magnetized so that a plurality of magnetic poles are formed along the outer peripheral surface, as shown in FIG. The Hall ICs 46 and 47 are installed on the outer side in the radial direction of the sensor magnets 44 and 45, and face the outer peripheral surfaces of the sensor magnets 44 and 45 with a predetermined interval. Here, the Hall ICs 46 a to 46 c are arranged to face the sensor magnet 44, and the Hall IC 47 is arranged to face the sensor magnet 45. Thereby, as the rotor 28 rotates, the sensor magnets 44 and 45 rotate while facing the Hall ICs 46 and 47 with a predetermined clearance.

  Also in the motor 25, a two-pole Hall IC is used for the Hall IC 47 (magnetic detection device), and detection signals are output from the Hall elements Q1 and Q2 (Magnetic detection elements) as the sensor magnet 45 rotates. Is done. Here, the Hall IC 47 is arranged obliquely with respect to the rotation direction of the sensor magnet 45 as shown in FIG. FIG. 8 is an explanatory diagram showing the arrangement of the Hall ICs 47 in the motor 25. As shown in FIG. 8A, the Hall IC 47 is arranged by rotating a conventional Hall IC arranged in the same direction as the Hall IC 46 in the Z direction shown in the figure. Here, as shown in FIG. 8B, the Hall elements Q1 and Q2 of the Hall IC 47 are respectively arranged on different rotation planes A1 and A2 that are separated from each other in the axial direction with the rotation center O of the rotor 28 as the center. Is done. Also in this case, the angle θ1 between the line segment L connecting the Hall elements Q1 and Q2 and the tangent line T passing through the midpoint M of the Hall elements Q1 and Q2 is 45 °.

  Thereby, compared with the conventional motor using the sensor magnet of the same diameter, the magnetization pitch of the sensor magnet 45 can be set finely (refer FIG. 5). For this reason, the resolution can be increased without changing the diameter of the sensor magnet 45, and the detection accuracy of the rotor rotational position can be improved. Also, when using sensor magnets with the same magnetization pitch, the magnetism detection element may be placed closer to the center of rotation, reducing the diameter of the sensor magnet, improving the layout of brushless motors and reducing magnet material costs. It becomes possible to plan.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, the outer diameter and magnetization pitch of the sensor magnet 19, θ 1, θ 2 and the like relating to the placement of the Hall IC 22 are not limited to the above-mentioned numerical values, and various changes can be made according to design specifications. If θ2 is too small (closer to 0 °; θ1 approaches 90 °), the circumferential distance of the elements Q1 and Q2 becomes smaller, and the outer diameter of the sensor magnet 19 can be reduced. On the other hand, the pulse period of the detection signals from the elements Q1 and Q2 becomes too small, and the detection accuracy decreases. Further, if the value is large (approaching 90 °; θ1 approaches 0 °), the effect of reducing the diameter of the magnet is reduced. Therefore, according to the experiments by the present inventors, a range of approximately 30 ° (sensor magnet outer diameter: φ26) to 60 ° (same: φ43) is appropriate, preferably 45 ° ± 7.5 ° (same as above). : Φ31 to φ40), particularly preferably 45 ° ± 5 ° (same as φ33 to φ38).

  In the above-described embodiments, the inner rotor type brushless motor has been described as an example. However, the present invention can also be applied to an outer rotor type brushless motor in which a rotor is disposed outside the stator. Further, in the above-described embodiment, the brushless motor used in the column assist type EPS is shown. However, the assist force is applied to the rack assist type in which the motor is arranged coaxially with the rack shaft and the pinion gear meshing with the rack shaft. It is also applicable to a pinion assist type EPS motor. In addition, the present invention is widely applicable to general brushless motors as well as motors for EPS and various in-vehicle electric products.

It is sectional drawing which shows the structure of the brushless motor which is Example 1 of this invention. It is explanatory drawing which shows the structure of the sensor part in the brushless motor of FIG. It is explanatory drawing which compared arrangement | positioning of Hall IC of the brushless motor of FIG. 1 and the conventional brushless motor (FIG. 9). It is sectional drawing which shows the structure of the brushless motor which is the other Example of this invention, and is the modification which distribute | arranged the sensor magnet to the motor part side. It is explanatory drawing which showed the hall | hole IC diagonally, and showed the sensor pitch in the case of using the sensor magnet of the same diameter as the past compared with the conventional structure, (a), when hall | hole IC is diagonally arranged, (B) has each shown the case of the conventional arrangement | positioning. It is sectional drawing which shows the structure of the brushless motor which is Example 2 of this invention. It is explanatory drawing which shows the structure of the sensor part in the brushless motor of FIG. It is explanatory drawing which shows arrangement | positioning of Hall IC in the brushless motor of FIG. It is sectional drawing which shows the structure of the conventional brushless motor. It is explanatory drawing which shows the structure of the sensor part in the brushless motor of FIG. It is explanatory drawing which shows the structure of the sensor part in the brushless motor of FIG. It is explanatory drawing which shows the arrangement | positioning relationship of the Hall element in the brushless motor of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Motor part 3 Sensor part 4 Rotor 5 Stator 6 Housing 7 Stator core 8 Winding 9 Bracket 11 Rotor shaft 12 Rotor core 13 Rotor magnet 14 Magnet holder 15a, 15b Bearing 16 Spline part 17 Joint 18 Sensor magnet 19 Sensor magnet 21 Hole IC
22 Hall IC (Magnetic Detector)
23 Magnet plate 24 Substrate 25 Brushless motor 26 Motor unit 27 Sensor unit 28 Rotor 29 Stator 31 Housing 32 Stator core 33 Winding 34 Bracket 35 Rotor shaft 36 Rotor core 37 Rotor magnet 38 Magnet holder 38a Notch 39 Magnet cover 41a, 41b Bearing 42 Spline Part 43 Joint 44 Sensor magnet 45 Sensor magnet 46 Hall IC
46a-46c Hall IC
47 Hall IC (Magnetic Detector)
48 Sensor holders 48a to 48c Arm part 51 Brushless motor 52 Motor part 53 Sensor part 54 Rotor 55 Stator 56 Rotor shaft 57 Rotor core 58 Magnet holder 59 Rotor magnet 61a, 61b Bearing 62 Winding 63 Stator core 64 Housing 65 Bracket 66 Sensor magnet 67 Sensor Magnet 68 Hall IC
69 Hall IC
71 Magnet plate 72 Substrate Q1, Q2 Hall element (magnetic detection element)

Claims (7)

A stator with armature windings;
A rotor having a permanent magnet and arranged rotatably inside or outside the stator;
A plurality of magnetic poles are arranged along the circumferential direction, and a sensor magnet that rotates with the rotor;
A brushless motor having a magnetic detection device in which at least two magnetic detection elements that output a detection signal in accordance with a change in polarity of the sensor magnet are arranged at a predetermined interval;
The magnetic detection device is arranged at a predetermined interval with respect to the axial end surface of the sensor magnet,
The brushless motor, wherein the magnetic detection elements are respectively arranged on different circumferences from a rotation center of the rotor. A stator with armature windings;
A rotor having a permanent magnet and arranged rotatably inside or outside the stator;
A plurality of magnetic poles are arranged along the circumferential direction, and a sensor magnet that rotates with the rotor;
A brushless motor having a magnetic detection device in which at least two magnetic detection elements that output a detection signal in accordance with a change in polarity of the sensor magnet are arranged at a predetermined interval;
The magnetic detection device is disposed at a predetermined interval with respect to the outer peripheral surface of the sensor magnet,
The brushless motor according to claim 1, wherein the magnetic detection elements are respectively arranged on different planes of rotation about the rotation center of the rotor. A stator with armature windings;
A rotor having a permanent magnet and arranged rotatably inside or outside the stator;
A plurality of magnetic poles are arranged along the circumferential direction, and a sensor magnet that rotates with the rotor;
A brushless motor having a magnetic detection device in which two magnetic detection elements that output detection signals in accordance with a change in polarity of the sensor magnet are arranged at a predetermined interval;
A line segment L connecting the two magnetic detection elements Q1 and Q2 is inclined with respect to the tangent line T at the midpoint M of the circle passing through the midpoint M of the magnetic detection elements Q1 and Q2 with the rotation center O as the center. A brushless motor, wherein the magnetic detection device is arranged in a state.   4. The brushless motor according to claim 3, wherein an angle [theta] 1 between the line segment L and the tangent line T at the midpoint M is 30 [deg.] To 60 [deg.].   5. The brushless motor according to claim 3, wherein the magnetic detection device is disposed on an axial direction side of the sensor magnet and faces the axial end surface of the sensor magnet with a predetermined interval. Brushless motor.   5. The brushless motor according to claim 3, wherein the magnetic detection device is disposed on a radially outer side of the sensor magnet and faces the outer peripheral surface of the sensor magnet with a predetermined interval. motor. A stator with armature windings;
A rotor having a permanent magnet and arranged rotatably inside or outside the stator;
A plurality of magnetic poles are arranged along the circumferential direction, and a sensor magnet that rotates with the rotor;
A brushless motor having a magnetic detection device in which two magnetic detection elements that output detection signals in accordance with a change in polarity of the sensor magnet are arranged at a predetermined interval;
An angle θ2 between a line segment L connecting the two magnetic detection elements Q1, Q2 and a center line N2 passing through the center M of the magnetic detection elements Q1, Q2 and the rotation center O is 30 ° to 60 °. A brushless motor, wherein the magnetic detection device is arranged in a state.

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