JP2011182569A - Inner rotor type motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner rotor type motor capable of suppressing attraction in an axial line direction of a rotor by reducing the length of a drive magnet and suppressing the occurrence of vibration and noise of the rotor due to deviation of magnetic balance. <P>SOLUTION: The inner rotor type motor 50 includes a rotor 60 having an output shaft 4, a rotor yoke 5, an FG magnet 7, and a drive magnet 6, a stator 70 having a stator core 1 formed by laminating a plurality of soft magnetic steel plates oppositely to the drive magnet 6 at a predetermined spacing, and a circuit board 8 having hall elements 10 and an FG pattern 9 opposite to at least a part of the FG magnet 7 at a predetermined spacing, and fixed on the stator core 1. In the motor 50, the rotor 60 is supported rotatably for the circuit board 8, and frequencies are generated by the pattern system. The FG magnet 7 has position detection magnetic poles 7p whose number is equal to that of magnetic poles of the drive magnet 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inner rotor type motor used as a main motor for driving various mechanisms such as a copying machine and a laser beam printer.

  Conventionally, inventions relating to various inner rotor type motors have been disclosed. Among them, an inner rotor type motor as disclosed in Patent Document 1 is disclosed. In Patent Document 1, a rotor having an output shaft, a yoke formed in a bottomed hollow cylindrical shape and fixed to the output shaft, a drive magnet fixed to the outer surface of the yoke, and an FG magnet fixed to the bottom surface of the yoke. An inner rotor type motor provided is disclosed. The inner rotor type motor further includes a circuit board that is disposed on the end side of the output shaft and faces the FG magnet.

  Moreover, although it is an example of the invention regarding an outer rotor type | mold motor, the structure described in the patent document 2 which avoids the interference of the Hall element and FG pattern which are provided in a circuit board is disclosed. That is, Patent Document 2 discloses an outer rotor type motor in which an FG pattern is provided on a first surface of a circuit board and a Hall element is provided on a second surface of the circuit board. Of these Patent Documents 1 and 2, the inner rotor type motor described in Patent Document 1 will be described below with reference to FIG.

  FIG. 3A is a cross-sectional view showing a configuration of a conventional inner rotor type motor 150. This inner rotor type motor 150 is a DC servo motor. As shown in FIG. 3A, the inner rotor type motor 150 includes a housing 102. A rotor 160 and a stator 170 are provided inside the housing 102. The rotor 160 includes an output shaft 104, a bottomed hollow cylindrical rotor yoke 105 fixed to the output shaft 104, a drive magnet 106 fixed to the outer peripheral surface of the rotor yoke 105, and an FG magnet 107 fixed to the bottom surface of the rotor yoke 105. ing. The stator 170 includes a stator core 101. The stator core 101 is formed by laminating a plurality of soft magnetic steel plates and has a plurality of salient poles (not shown) extending in the radial direction. Each of the plurality of salient poles. The coil is wound around. The drive magnet 106 and the stator core 101 are opposed to each other. Note that the output shaft 4 is rotatable on the inner peripheral side of the inner wall portion 102a of the casing 102 via a bearing 103. For this reason, the rotor 160 including the output shaft 4 is rotatable.

  Further, the circuit board 108 provided with the FG pattern 109 is arranged so as to face the FG magnet 107 with a predetermined interval (see FIG. 3C). A Hall element 110 is mounted on the circuit board 108 so as to face the end face side of the drive magnet 106 with a predetermined interval. Note that the coil 111 is energized by the connector 111 via the circuit board 108.

  FIG. 3B is a plan view showing the configuration of the conventional drive magnet 106 and FG magnet 107. As shown in FIG. 3B, the drive magnet 106 is NS magnetized with different drive magnetic poles in the circumferential direction. Further, an FG magnet 107 is arranged at the center side of the drive magnet 106, and the FG magnet 107 is NS-polarized with frequency generating magnetic poles for detecting rotational speeds different in the circumferential direction.

  FIG. 3C is a plan view showing the configuration of the conventional circuit board 108. As shown in FIG. 3C, the circuit board 108 includes an FG pattern 109 and a Hall element 110. The FG pattern 109 is provided on the surface of the circuit board 108 facing the FG magnet 107. The hall element 110 faces the end face side of the drive magnet 6 with a predetermined interval, and is arranged so as not to interfere with the outer periphery of the FG pattern 109.

  In the inner rotor type motor 150 having such a configuration, it is necessary to detect the rotation frequency of the rotor 160 in order to control the rotation of the rotor 160. For this purpose, the frequency generating magnetic pole is NS multipolarly magnetized (hereinafter referred to as FG magnetization) on the surface of the FG magnet 107 (frequency generating magnet) (see FIG. 3B). A power generation element group (hereinafter referred to as FG pattern 109) is provided on the surface of the circuit board 108 (refer to FIG. 3C) facing this. When the rotor 160 rotates, a speed detection signal (hereinafter referred to as an FG signal) having a frequency proportional to the number of rotations of the rotor 160 generated in the FG pattern 109 is obtained. The speed detection means of the FG pattern method supplies the generated voltage of the FG pattern 109 by FG magnetization to the drive circuit to control the driving of the inner rotor type motor 150.

  Here, since it is necessary to detect the position of the drive magnet 106 by the Hall element 110 (position detection element), the drive magnet 106 must be elongated to the vicinity of the mounting position of the Hall element 110.

JP 2006-109575 A JP 2006-025537 A

  However, if the drive magnet 106 is longer than the stator core 101, the rotor 160 is attracted in the axial direction, so that there is a problem that vibration and noise are generated in the rotor 160 due to the magnetic balance being shifted.

  In view of the above situation, the present invention realizes shortening of the length of the drive magnet to suppress the attraction in the axial direction of the rotor, and can suppress the vibration and noise of the rotor due to the magnetic balance shift. It is an object to provide an inner rotor type motor.

  To achieve the above object, an inner rotor type motor includes an output shaft, a rotor yoke arranged around the output shaft and rotating together with the output shaft, and an FG arranged around the output shaft and rotated together with the output shaft. A magnet, a rotor having a drive magnet disposed around the rotor yoke and rotating together with the rotor yoke, and a stator core formed by laminating a plurality of soft magnetic steel plates facing the drive magnet at a predetermined interval And a circuit board having a Hall element and having an FG pattern facing the FG magnet at a predetermined interval and fixed to the stator core, the rotor being rotatable with respect to the circuit board Is an inner rotor type motor that generates a frequency by a pattern method, Tsu DOO is characterized in that it comprises as many position detecting magnetic pole of the magnetic poles of the drive magnet.

  According to the present invention, the FG magnet includes the same number of position detection magnetic poles as the number of magnetic poles of the drive magnet. Therefore, the necessity for increasing the length of the drive magnet is reduced. As a result, shortening of the length of the drive magnet is realized, the attraction in the axial direction of the rotor is suppressed, and the occurrence of vibration and noise of the rotor due to the deviation of the magnetic balance is suppressed.

It is sectional drawing which shows the structure of the inner rotor type | mold motor which concerns on the Example of this invention. It is a top view etc. which show the structure of the magnetic pole of FG magnet. It is sectional drawing etc. which show the structure of the conventional inner rotor type | mold motor.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, since the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, there is no specific description. As long as the scope of the invention is not limited to these, it is not intended.

  FIG. 1 is a cross-sectional view showing a configuration of an inner rotor type motor 50 according to Embodiment 1 of the present invention. As shown in FIG. 1, the inner rotor type motor 50 includes a housing 2. A rotor 60 and a stator 70 are disposed inside the housing 2. The housing 2 has an inner wall portion 2a and an outer wall portion 2b. The output shaft 4 that is a part of the rotor 60 arranged along the rotational axis direction is inserted inside the inner wall portion 2a. Therefore, the surface of the inner wall 2a and the output shaft 4 are opposed to each other with a predetermined distance. A plurality, that is, two bearings 3 are provided between the inner wall 2a and the output shaft 4, and the output shaft 4 is rotatable in the inner wall 2a.

  The stator 70 includes the stator core 1. In the space between the inner wall portion 2a and the outer wall portion 2b, the stator core 1 provided in the stator 70 is disposed facing the wall surface of the outer wall portion 2b. The stator core 1 is formed by laminating a plurality of soft magnetic steel plates (silicon steel plates or the like) so as to face a drive magnet 6 described later at a predetermined interval. The stator core 1 has a plurality of salient poles (not shown) extending in the radial direction, and a coil is wound around each of the plurality of salient poles.

  The rotor 60 includes a rotor yoke 5, an FG magnet 7, and a drive magnet 6 in addition to the output shaft 4 described above. The rotor yoke 5 is fixedly disposed around the output shaft 4 and rotates together with the output shaft 4. Specifically, the rotor yoke 5 is formed in a bottomed hollow cylindrical shape, and is fixed to the output shaft 4. The disk portion 5 q extends from the periphery of the fixed portion 5 p in the direction orthogonal to the output shaft 4. It has a hollow cylindrical part 5r extending in parallel with the output shaft 4 from the outer edge part of 5q.

  The FG magnet 7 is disposed around the output shaft 4 and rotates together with the output shaft 4. Specifically, the FG magnet 7 is a disc-shaped magnet having a hole formed in the center side, and is formed on the bottom portion of the bottomed hollow cylindrical shape, that is, the disc portion 5q on the end surface side in the rotation axis direction of the rotor yoke 5. Fixed and arranged. The FG magnet 7 rotates integrally with the output shaft 4 and the rotor yoke 5. Note that FG (an abbreviation for FREQUENCY GENERATOR) means a frequency generator.

  On the other hand, the drive magnet 6 is disposed around the rotor yoke 5 and rotates together with the rotor yoke 5. Specifically, the drive magnet 6 is a hollow cylindrical magnet, is fixedly disposed on the outer peripheral surface of the hollow cylindrical portion 5r of the rotor yoke 5, faces the stator core 1 at a predetermined interval, and is connected to the output shaft 4 and the rotor yoke 5. Rotates integrally.

  The length of the drive magnet 6 in the direction parallel to the output shaft 4 is set to be substantially the same as the length of the stator core 1 in the direction parallel to the output shaft 4. The length of the drive magnet 6 in the direction parallel to the output shaft 4 may be set to be equal to or shorter than the length of the stator core 1 in the direction parallel to the output shaft 4.

  The circuit board 8 has a Hall element 10 and an FG pattern 9 that faces the FG magnet 7 at a predetermined interval, and is fixed to the stator core 1. Specifically, an FG pattern 9 is provided on the first surface 8a (see FIG. 2C) of the circuit board 8, and the FG pattern 9 is spaced from the frequency generating magnetic pole 7q (see FIG. 2A) by a predetermined distance. Are facing each other. A Hall element 10 is provided on the second surface 8b (see FIG. 2D) opposite to the first surface 8a of the circuit board 8, and this Hall element 10 is used for position detection in a direction parallel to the output shaft 4. It is arranged at a position corresponding to the magnetic pole 7p.

  The rotor 60 is rotatably supported via the bearing 3 held by the housing 2, and thus the rotor 60 is rotatably supported with respect to the circuit board 8. The inner rotor type motor 50 generates a frequency by a pattern method. Note that the coil 11 is energized by the connector 11 via the circuit board 8.

  FIG. 2A is a plan view showing the configuration of the FG magnet 7. FIG. 2B is a plan view showing the configuration of the drive magnet 6 and the rotor yoke 5. FIG. 2B corresponds to a plan view showing a state in which the FG magnet 7 of FIG. As shown in FIG. 2A and FIG. 2B, the FG magnet 7 includes position detection magnetic poles 7p for position detection of the same number as the number of magnetic poles of the drive magnet 6 on the inner side in the radial direction. A frequency generating magnetic pole 7q for rotational speed detection is NS multi-pole magnetized outward in the direction. The outer diameter of the FG magnet 7 is set larger than the outer diameter of the hollow cylindrical drive magnet 6.

  FIG. 2C is a plan view showing the configuration of the first surface 8 a of the circuit board 8. As shown in FIG. 2C, the FG pattern 9 is provided on the first surface 8 a of the circuit board 8 so as to face the frequency generating magnetic pole 7 q of the FG magnet 7. Note that a noise cancellation pattern 9k is formed on the innermost peripheral side of the FG pattern 9 on the first surface 8a of the circuit board 8.

  FIG. 2D is a plan view showing the configuration of the second surface 8 b of the circuit board 8. As shown in FIG. 2D, the Hall element 10 is provided on the second surface 8 b of the circuit board 8 at a position corresponding to the position detection magnetic pole 7 p in a direction parallel to the output shaft 4. Here, the Hall element 10 is arranged closer to the output shaft 4 than in the case of the Hall element 110 provided on the conventional circuit board 108. This corresponds to the fact that the above-described position detection magnetic pole 7p is disposed closer to the output shaft 4 in the radial direction than in the prior art.

  In the past, in order to reduce the influence of eccentricity or deflection of the FG magnet 107 when the rotor 160 rotates, the radial length of the FG pattern 109 in the radial direction of the FG magnet 107 is equal to the radial direction of the FG magnet 107. It had to be set larger than the length. However, if the radial length of the FG pattern 109 is set large, the FG pattern 109 interferes with the Hall element 110, so the outer diameter of the FG magnet 107 and the radial length of the FG pattern 109 cannot be increased. There was a problem that high pulses could not be realized. In contrast, the configuration of the embodiment has an advantage that the radial length of the FG pattern 109 can be formed long because the Hall element 10 is provided on the second surface 8b of the circuit board 8.

  According to the configuration of the embodiment, the FG magnet 7 includes the same number of position detection magnetic poles 7p as the number of magnetic poles of the drive magnet 6. Therefore, the necessity for increasing the length of the drive magnet 6 is reduced. As a result, the length of the drive magnet 6 is shortened, the attraction of the rotor 60 in the axial direction is suppressed, and the occurrence of vibration and noise of the rotor 60 due to the magnetic balance shift is suppressed.

  The FG magnet 7 has a frequency generating magnetic pole 7q magnetized in a large number on the outer peripheral side, a position detecting magnetic pole 7p formed on the inner peripheral side, and the outer diameter of the frequency generating magnetic pole 7q is outside the drive magnet 6. It is larger than the diameter. Accordingly, the radial length of the frequency generating magnetic pole 7q can be set large, thereby realizing a high pulse, and a controller, which is a control unit (not shown), can perform fine and highly accurate rotation control.

  Further, since the length of the drive magnet 6 in the direction parallel to the output shaft 4 is set to be equal to or less than the length of the stator core 1 in the direction parallel to the output shaft 4, the material of the drive magnet 6 is reduced. The reason why the length of the drive magnet 6 may be set to be equal to or less than the length of the stator core 1 is as follows.

  That is, when the drive magnet 6 is longer than the stator core 1, the rotor 60 is attracted to the circuit board 8 in the axial direction. For this reason, the magnetic balance is shifted, and vibration and noise are generated in the rotor 60. When the position detection magnetic pole 7p is provided in the FG magnet 7 as in the embodiment, the position detection by the drive magnet 6 becomes unnecessary. Therefore, there is no problem even if the length of the drive magnet 6 is shortened. As a result, the rotor 60 is not attracted in the axial direction, so that the magnetic balance in the axial direction can be achieved, and vibration and noise are not generated in the rotor 60. The drive magnet 6 is made of a rare earth material such as neodymium or ferrite, but if the drive magnet 6 is shortened, the material of the expensive drive magnet 6 is reduced. , Cost is reduced.

  An FG pattern 9 is provided on the first surface 8a so as to face the FG magnet 7, and a Hall element 10 is provided on the second surface 8b. Therefore, interference between the Hall element 10 and the FG pattern 9 is suppressed, high-precision control is realized, and vibration and noise of the rotor 60 that adversely affect the motor characteristics are reduced. As a result, the diameter of the FG magnet 7 can be set large, so that a high pulse is realized, and fine and highly accurate rotation control is possible. Further, the Hall element 10 is provided on the second surface 8 b of the circuit board 8, so that the Hall element 10 is disposed outside the inner rotor type motor 50. Therefore, even if the heat generated by the coil wound around the stator core 1 is accumulated in the inner rotor type motor 50, the Hall element 10 outside the inner rotor type motor 50 is not affected by heat. As a result, the reliability of the Hall element 10 is improved.

  Further, by arranging the Hall element 10 on the second surface 8b opposite to the first surface 8a on which the FG pattern 9 and the noise cancellation pattern 9k of the circuit board 8 are formed, interference between the Hall element 10 and the FG pattern 9 is prevented. Can be solved reliably.

(Modification)
In the embodiment, the Hall element 10 is a position detection element, but the present invention is not limited to this configuration. That is, even if the Hall IC is a position detection element, the same can be implemented.

  Further, the present invention can be similarly implemented with a motor provided with a drive circuit for rotating the rotor 60 on the circuit board 8 and a control circuit for controlling the rotation of the rotor 60.

DESCRIPTION OF SYMBOLS 1 Stator core 4 Output shaft 5 Rotor yoke 6 Drive magnet 7 FG magnet 7p Position detection magnetic pole 8 Circuit board 10 Hall element 50 Inner rotor type motor 60 Rotor 70 Stator

Claims (4)

An output shaft, a rotor yoke arranged around the output shaft and rotating together with the output shaft, an FG magnet arranged around the output shaft and rotating together with the output shaft, and a rotor yoke arranged around the rotor yoke A rotor having a drive magnet that rotates with the
A stator having a stator core formed by laminating a plurality of soft magnetic steel plates facing the drive magnet at a predetermined interval;
A circuit board having a Hall element and having an FG pattern facing the FG magnet at a predetermined interval and fixed to the stator core,
The rotor is supported rotatably with respect to the circuit board, and is an inner rotor type motor that generates a frequency in a pattern system,
The FG magnet is provided with the same number of position detection magnetic poles as the number of magnetic poles of the drive magnet. The FG magnet is a disk-shaped magnet in which a large number of NS magnetized frequency generating magnetic poles are formed on the outer peripheral side, and the position detecting magnetic pole is formed on the inner peripheral side,
The drive magnet is a hollow cylindrical magnet,
The inner rotor type motor according to claim 1, wherein an outer diameter of the frequency generating magnetic pole is larger than an outer diameter of the drive magnet.   The FG pattern is provided on the first surface of the circuit board so as to oppose the frequency generating magnetic pole, and the Hall element is provided on the second surface of the circuit board opposite to the first surface. The inner rotor type motor according to claim 2, wherein the inner rotor type motor is provided at a position corresponding to the position detection magnetic pole in a direction parallel to the output shaft.   The length of the drive magnet in the direction parallel to the output shaft is set to be equal to or less than the length of the stator core in the direction parallel to the output shaft. The inner rotor type motor described in the item.

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