JP2008206354A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fix sensor magnets to a magnet plate without using an adhesive, facilitate a process management, and improve the reliability of a product. <P>SOLUTION: The ring sensor magnets 18, 19 are concentrically attached to the magnet plate 23 fixed to a rotor shaft. These sensor magnets 18, 19 are made formed from a plastic magnet, and integrally formed with the magnet plate 23 by injection molding without using the adhesive. Tapered retaining holes 26, 27 are provided in the magnet plate 23. Tapered retaining sections 28, 29 integrally formed with the sensor magnets 18, 19 by injection molding are loaded and engaged with the retaining holes 26, 27. The sensor magnets 18, 19 are retained in the magnet plate 23, and prevented from being rotated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a brushless motor, and more particularly to a magnet fixing structure used for detecting a rotor rotational position of a 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. 7 is a cross-sectional view showing a configuration of a conventional brushless motor. As shown in FIG. 7, 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 (magnetic detection elements), 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. FIG. 8 is an explanatory view showing a mounting structure of the sensor magnets 66 and 67. FIG. As shown in FIG. 8, the sensor magnets 66 and 67 are attached to a disk-shaped magnet plate 71 fixed to the rotor shaft 56. The sensor magnets 66 and 67 and the magnet plate 71 are fixed with an adhesive, and the sensor magnets 66 and 67 rotate together with the rotor shaft 56. The motor 51 detects the rotation direction of the rotor 54 using the detection signal of the Hall IC 69 while detecting the rotation direction of the rotor 54 by combining the detection signals of the Hall ICs 68 and 69, and controls the energization timing for the winding 62. .
Japanese Patent Application No. 2004-72404

  However, with conventional brushless motors, it is difficult to manage the adhesive, and there is a problem that the adhesive may adhere to other parts due to protrusion or splashing. It was. Also. When the motor is assembled, an adhesion process is required. Therefore, the number of assembling steps is increased, and there is a problem that the cost is increased. Further, since the sensor magnets 66 and 67 and the magnet plate 71 are not mechanically fixed, there is a case where there is a concern about reliability against vibration and impact.

  An object of the present invention is to fix a sensor magnet to a magnet plate without using an adhesive, thereby facilitating process management.

  The brushless motor of the present invention includes a stator, a rotor having a rotor shaft, and a rotor rotatably disposed with respect to the stator, a magnet plate fixed to the rotor shaft, and a ring shape attached to one end surface of the magnet plate. A first sensor magnet, and a ring-shaped second sensor magnet that is formed larger in diameter than the first sensor magnet and is concentrically attached to one end surface of the magnet plate. The first and second sensor magnets are formed of plastic magnets and are integrally formed with the magnet plate by injection molding.

  In the present invention, the first and second sensor magnets are formed of plastic magnets and injection-molded integrally with the magnet plate, and the sensor magnet is fixed to the magnet plate without using an adhesive. Thereby, management of an adhesive agent becomes unnecessary, process management becomes easy, an adhesive process becomes unnecessary, and an assembling man-hour is reduced.

  In the brushless motor, the magnet plate is provided with a taper-shaped through hole formed along the axial direction and having an inner diameter on the other end surface side larger than an inner diameter on the one end surface side. And the taper-shaped projection part extended in the axial direction formed integrally with the 2nd sensor magnet may be fitted. As a result, the sensor magnet can be prevented from coming off and prevented from rotating around the magnet plate together with the injection molding, and the sensor magnet can be easily and mechanically fixed to the magnet plate.

  Further, in the brushless motor, the protrusions are formed at positions corresponding to the first and second sensor magnets, respectively, and the protrusions are boundaries between the magnetic poles formed on the first and second sensor magnets. You may arrange | position in positions other than a part. Thereby, the influence of the magnetic flux disturbance by a projection part is suppressed, and the magnetic pole change of a sensor magnet can be caught correctly. In this case, if the magnetic pole pitch of one sensor magnet is small and the protrusion cannot be placed at a position other than the boundary of each magnetic pole, the magnetic pole pitch is large and the protrusion can be placed at a position other than the boundary of each magnetic pole. Only the protrusion corresponding to the sensor magnet may be arranged at a position other than the boundary between the magnetic poles of the sensor magnet. For example, the magnetic pole pitch of the second sensor magnet is small, and the protrusion cannot be arranged at a position other than the boundary of each magnetic pole. However, the first sensor magnet has a large magnetic pole pitch and the protrusion is at a position other than the boundary of each magnetic pole. If it can be arranged, only the protrusion provided on the inner peripheral side corresponding to the first sensor magnet may be arranged at a position other than the boundary of each magnetic pole of the first sensor magnet.

  According to the brushless motor of the present invention, the first and second sensor magnets are made of plastic with a brushless motor in which a ring-shaped first sensor magnet and a second sensor magnet are concentrically attached to a magnet plate fixed to the rotor shaft. Since it is formed of a magnet and formed integrally with the magnet plate by injection molding, the sensor magnet can be fixed to the magnet plate without using an adhesive. For this reason, management of an adhesive agent becomes unnecessary at the time of manufacturing a brushless motor, and process management becomes easy. In addition, since the bonding step is not necessary, the number of assembling steps is reduced, and the manufacturing cost is reduced.

  In addition, a tapered through hole is provided in the magnet plate, and a tapered projection formed integrally with the first and second sensor magnets is fitted into the through hole, whereby the sensor magnet is mounted together with the injection molding. The magnet plate can be prevented from coming off and prevented from rotating, and the sensor magnet can be easily and mechanically fixed to the magnet plate.

  Furthermore, the protrusions for retaining and preventing rotation may be arranged at positions other than the boundary portions of the magnetic poles formed on the sensor magnet. Thereby, the influence of magnetic flux disturbance by a projection part is suppressed, and the magnetic pole change of a 1st sensor magnet can be caught correctly.

  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 also composed of a motor unit 2 and a sensor unit 3, similarly to the motor 51 of FIG. 7. 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.

  The sensor unit 3 also has a double multipolar sensor structure similar to the motor 51 described above. The sensor unit 3 is provided with ring-shaped sensor magnets 18 and 19 and Hall ICs 21 and 22. The sensor magnet 18 is concentrically disposed on the inner peripheral side of the sensor magnet 19, and the inner sensor side first sensor 10 is formed by the Hall IC 21 and the sensor magnet (first sensor magnet) 18. The Hall IC 22 and the sensor magnet (second sensor magnet) 19 form a second sensor 20 on the outer peripheral side. The sensor magnet 18 is magnetized to have the same number of poles (six poles) as the rotor magnet 13, and magnetic poles are arranged along the circumferential direction. On the other hand, the sensor magnet 19 is magnetized more finely than the sensor magnet 18 at a pitch of 5 °, and 72 magnetic poles are arranged along the circumferential direction.

  The sensor magnets 18 and 19 are formed by so-called plastic magnets formed by mixing synthetic resin with ferrite magnet or rare earth magnet powder. The sensor magnets 18 and 19 are integrally formed on one end face side of a disk-shaped metal magnet plate 23 to form a sensor magnet unit 25. 2 is a cross-sectional view showing the configuration of the sensor magnet unit 25, FIG. 3 is a perspective view showing the configuration of the left side of the sensor magnet unit 25 in FIG. 2, and FIG. 4 is a perspective view showing the configuration of the right side. is there. 2 corresponds to a cross-sectional view taken along the line AA in FIG.

  As shown in FIG. 2, the sensor magnets 18, 19 are fixed to the end surface on the right side of the magnet plate 23 in the drawing so as not to come off and to be prevented from rotating. In this case, the magnet plate 23 is provided with six retaining holes (through holes) 26, 27 equally on the inner and outer peripheries corresponding to the sensor magnets 18, 19. The retaining holes 26 and 27 are tapered holes, and the inner diameter is larger on the left side (the other end surface side) in FIG. 2 than on the right side (the one end surface side). Retaining portions (protrusions) 28 and 29 extending in the axial direction from the back side (magnet plate side) of the sensor magnets 18 and 19 are fitted in the retaining holes 26 and 27. The retaining portions 28 and 29 are formed integrally with the sensor magnets 18 and 19 by filling and filling the resin into the retaining holes 26 and 27 during molding. Accordingly, the sensor magnets 18 and 19 are prevented from coming off in the axial direction and are also prevented from rotating in the circumferential direction.

  The magnet plate 23 is also provided with three gate holes 31 equally along the circumferential direction. The gate hole 31 is used as a gate for supplying resin into the mold when the sensor magnet is molded. At the time of molding, the synthetic resin also flows into the gate hole 31 to form the gate portion 32. The gate portion 32 also functions as a detent for the sensor magnets 18 and 19. The magnet plate 23 is further provided with a positioning hole 33. The positioning hole 33 is used as a reference hole for aligning the sensor position and the rotor magnet 13 when the sensor magnets 18 and 19 are magnetized or when the motor is assembled.

  The sensor magnets 18 and 19 are formed integrally with the magnet plate 23 and then magnetized in the above-described manner by a magnetizing device. In the magnetizing process, the sensor magnet unit 25 is set in the magnetizing yoke with the positioning hole 33 as a reference, and the inner sensor magnet 18 is first magnetized first. After magnetizing the sensor magnet 18 (six poles), the sensor magnet unit 25 is removed from the magnetizing yoke, and the outer sensor magnet 19 is magnetized. That is, with the positioning hole 33 as a reference, the sensor magnet unit 25 is set in another magnetizing yoke, and the outer 72 poles are magnetized. In this case, if the outer sensor magnet 19 (72 poles) is magnetized first, when the inner sensor magnet 18 (six poles) is magnetized, the influence will be exerted on the sensor magnet 19 side. The inner sensor magnet 18 is first magnetized. As shown in FIG. 2, the sensor magnets 18 and 19 are continuous with each other. However, according to the experiments by the inventors, the portion between the two is magnetized even by the above-described magnetization process. There was no influence on the detection of the rotor rotational position or the like.

  As described above, in the motor 1 according to the present invention, the sensor magnets 18 and 19 are formed of plastic magnets and are integrally formed with the magnet plate 23. Therefore, the sensor magnets 18 and 19 can be attached to the magnet plate 23 without using an adhesive. Can be fixed. This eliminates the need for management of the adhesive, eliminates the possibility of the adhesive adhering to other parts due to protrusion or scattering, and facilitates process management. Also. When the motor is assembled, the bonding process is not necessary, and accordingly, the number of assembling steps can be reduced and the product cost can be reduced. Further, by providing the taper hole-shaped retaining portions 28 and 29, the sensor magnets 18 and 19 can be prevented from coming off and stopped at a stretch by injection molding. Can be fixed. For this reason, the sensor magnets 18 and 19 can be securely fixed to the magnet plate 23, and the reliability against vibration and impact can be improved.

  On the other hand, such a sensor magnet unit 25 is fixed to the rotor shaft 11 and rotates together with the rotor 4. Here, the magnet plate 23 is press-fitted and fixed to the rotor shaft 11, whereby the sensor magnets 18 and 19 rotate together with the rotor shaft 11. On the other hand, the Hall ICs 21 and 22 that detect magnetic pole changes of the sensor magnets 18 and 19 are placed on a substrate 24 fixed in the bracket 9. The Hall ICs 21 and 22 are disposed on the substrate so as to face the sensor magnets 18 and 19, and a magnetic detection element is disposed in each Hall IC 21 and 22.

  When the rotor shaft 11 rotates, the sensor magnets 18 and 19 also rotate so as to face the Hall ICs 21 and 22 through a predetermined distance. When the magnetic poles of the opposing sensor magnets 18 and 19 change with the rotation of the sensor magnets 18 and 19, a predetermined rotational position detection signal (ON / OFF signal) is output from the Hall ICs 21 and 22. Also in the motor 1, the rotation direction / rotation position of the rotor 4 is grasped using the detection signals of the Hall ICs 21 and 22, and the energization timing for the winding 8 is controlled. In this case, the rotation direction of the rotor 4 is detected by a combination of detection signals from the Hall ICs 21 and 22. Further, the rotational position of the rotor 4 is detected exclusively using the detection signal of the Hall IC 22, and the rotor 4 is driven to rotate based on the detection information.

  Next, as a second embodiment of the present invention, a sensor magnet unit that takes into account the disturbance of the magnetic spacing due to the retaining portion will be described. FIG. 5 is a perspective view showing the configuration of the left side surface of the sensor magnet unit 35 used in the brushless motor that is Embodiment 2 of the present invention, and FIG. 6 is an explanatory view showing the relationship between the retaining portion and the magnetic pole. . In addition, the brushless motor which is Example 2 has the same configuration as the motor 1 of Example 1 except for the sensor magnet unit. Moreover, in Example 2, the same code | symbol is attached | subjected about the member similar to Example 1, and the description is abbreviate | omitted.

  In the sensor magnet unit 25 of the first embodiment, the retaining portions 28 and 29 are located just at the boundary between the magnetic poles, as indicated by the alternate long and short dash line (reference P portion) in FIG. In the portion where the retaining portions 28 and 29 are present, the thickness of the sensor magnets 18 and 19 is different from that of other portions. For this reason, when the retaining portions 28 and 29 come to the magnetic pole boundary portion as shown in FIG. 6, there is a possibility that the Hall ICs 21 and 22 cannot accurately detect the magnetic pole change. Therefore, in the sensor magnet unit 35 of the second embodiment, the retaining portion 28 is arranged by being shifted by 30 ° in the circumferential direction (a broken line position in FIG. 6: a portion Q), and the retaining portion 29 is other than the boundary portion of each magnetic pole. I try to come to the position. As a result, the influence of the magnetic flux disturbance due to the retaining portion 28 is suppressed, and the magnetic pole change of the sensor magnet 18 can be accurately captured.

  With respect to the retaining portion 29, the magnetic pole pitch of the sensor magnet 19 is small (the interval between the magnetic poles is small), so that the retaining portion 29 comes to the magnetic pole boundary even if the position of the retaining portion is shifted. For this reason, here, only the retaining portion 28 is shifted in the circumferential direction. Therefore, in the motor of the second embodiment, the influence of the retaining portion 29 on the sensor magnet 19 side is unavoidable. However, according to the experiments by the inventors, the influence of the magnetic flux disturbance is considerable only by shifting the sensor magnet 18 side. I was able to improve. However, when the magnetic pole pitch of the sensor magnet 19 is large and the retaining portion 29 can be disposed at a position other than the boundary portion of each magnetic pole, the retaining portion 29 is shifted in the circumferential direction and disposed at a position other than the magnetic pole boundary portion. Is preferable.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the second embodiment, the influence of the magnetic flux disturbance at the retaining portions is reduced by shifting the positions of the retaining portions 28 and 29 in the circumferential direction. It is also possible to reduce the influence of the retaining portions 28 and 29 by shifting the positions of the Hall ICs 21 and 22. For example, the magnetized patterns of the sensor magnets 18 and 19 may be shifted in the circumferential direction by 30 ° with respect to the positioning hole 33. Further, by shifting the magnetizing positions of the sensor magnets 18 and 19 in the radial direction, the retaining portions 28 and 29 are removed from the center position in the radial direction of the magnet, and the influence of the retaining portions 28 and 29 is reduced. Hall ICs 21 and 22 may be arranged. Of course, if there is a margin in the radial direction, the retaining portions 28 and 29 may be shifted in the radial direction so as not to be applied to the sensor magnets 18 and 19.

  On the other hand, in the above-described embodiments, the inner rotor type brushless motor has been described as an example. However, the present invention is also applicable to an outer rotor type brushless motor in which a rotor is disposed outside the stator. In the above-described embodiment, the brushless motor used for 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. Furthermore, 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 sectional drawing which shows the structure of a sensor magnet unit, and is equivalent to sectional drawing along the AA line in FIG. It is a perspective view which shows the structure of the left side surface in FIG. 2 of a sensor magnet unit. It is a perspective view which shows the structure of the right side in FIG. 2 of a sensor magnet unit. It is a perspective view which shows the structure of the left side surface of the sensor magnet unit used for the brushless motor which is Example 2 of this invention. It is explanatory drawing which shows the relationship between a retaining part and a magnetic pole. It is sectional drawing which shows the structure of the conventional brushless motor. It is explanatory drawing which shows the attachment structure of the sensor magnet in the conventional brushless motor.

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 10 1st sensor 11 Rotor shaft 12 Rotor core 13 Rotor magnet 14 Magnet holder 15a, 15b Bearing 16 Spline part 17 Joint 18 Sensor magnet ( First sensor magnet)
19 Sensor magnet (second sensor magnet)
20 Second sensor 21 Hall IC
22 Hall IC
23 Magnet plate 24 Substrate 25 Sensor magnet unit 26 Retaining hole (through hole)
27 Retaining hole (through hole)
28 Retaining part (protrusion)
29 Retaining part (protrusion)
31 Gate hole 32 Gate part 33 Positioning hole 35 Sensor magnet unit 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

Claims (3)

A stator, a rotor provided with a rotor shaft and rotatably arranged with respect to the stator; a magnet plate fixed to the rotor shaft; a ring-shaped first sensor magnet attached to one end surface of the magnet plate; A brushless motor having a ring-shaped second sensor magnet formed on a larger diameter than the first sensor magnet and concentrically attached to one end surface of the magnet plate. ,
The brushless motor, wherein the first and second sensor magnets are formed of plastic magnets and are integrally formed with the magnet plate by injection molding.   2. The brushless motor according to claim 1, wherein the magnet plate has a tapered through hole formed along an axial direction and having an inner diameter on the other end surface side larger than an inner diameter on the one end surface side. Is a brushless motor in which an axially extending tapered protrusion formed integrally with the first and second sensor magnets is fitted.   3. The brushless motor according to claim 1, wherein the protrusion is formed at a position corresponding to each of the first and second sensor magnets, and is provided on an inner peripheral side corresponding to the first sensor magnet. The protrusion is disposed at a position other than the boundary between the magnetic poles formed on the first sensor magnet.

Images