JP2012060811A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily reduce or prevent electrostatic charge.SOLUTION: A motor includes a cover member 14 formed by a conductive material, a bearing part, a shaft, a rotor magnet rotating with the shaft, an annular stator facing the rotor magnet in the radial direction in the cover member, a circuit board 32 arranged perpendicular to a central axis J1 in the cover member, and an electric power line 431 and a ground line 432 connecting to the circuit board. The circuit board includes a conductive pattern 41 and an electronic component mounted on the conductive pattern, and the conductive pattern includes a driving circuit pattern 411 supplying electric power from the electric power line to the stator, a ground pattern 412 to which the ground line is connected, and a cover antistatic pattern 413 which is located closer to the cover member than the driving circuit pattern and the ground pattern or contacts with the cover member. The circuit board includes a resistance electrically connecting the ground pattern with the cover antistatic pattern.

Description

  The present invention relates to an electric motor.

  Conventionally, an inner rotor type motor is used as a drive source in various office automation (OA) devices. A brushless motor disclosed in Japanese Patent Laid-Open No. 2005-229698 includes a substantially cylindrical covered housing, a cover plate, a stator, a rotor magnet, a rotor yoke, and a rotating shaft. The housing includes a cylindrical peripheral wall and an end plate portion provided at one end of the cylindrical peripheral wall. A cover plate is fixed to the other end of the housing. The stator is fixed to the inner peripheral surface of the cylindrical peripheral wall. A rotor yoke having a cylindrical portion and a lid portion is disposed inside the stator. A rotor magnet is fixed to the outer peripheral surface of the cylindrical portion of the rotor yoke. The rotor magnet and the stator face each other. A shaft is fixed to the lid portion of the rotor yoke. The shaft is rotatably supported with respect to the housing via bearings provided on the end plate portion and the cover plate.

A molded motor disclosed in Japanese Patent Laid-Open No. 11-75337 includes a stator, a conductive bracket, and a conductive rubber bush. The bracket is attached to the axial end surface of the stator via resin. The rubber bush is disposed between a hole formed in the axial end surface of the stator and a recess provided in the surface of the bracket on the stator side. In the molded motor, the stator is grounded to the bracket via a rubber bush.
JP 2005-229698 A JP-A-11-75337

  By the way, in a motor, the cover member which covers a rotation part and a stationary part normally is provided. When the housing of the device to which the motor is attached is grounded, the cover member of the motor is easily grounded by screwing the cover member of the motor to the housing of the device. Thereby, charging of the cover member is prevented. However, if the housing is made of a non-conductive material such as resin, or if the housing cannot be grounded, a complicated grounding structure is required to prevent the motor cover member from being charged. It becomes. In particular, in an OA device in which paper is transported, static electricity is likely to be generated due to friction with the paper, and the charge removal of the cover member is important. In the method disclosed in JP-A-11-75337, the number of parts increases. The assembly of the motor is also complicated.

  In the case of a brushless motor, a circuit board on which electronic components such as integrated circuits and transistors are mounted is provided, and it is necessary to reliably prevent the influence of the static electricity on the electronic components and the driving circuit pattern.

  An object of the present invention is to easily reduce or prevent charging of a cover member.

  A motor according to an exemplary aspect of the present invention includes a cover member formed of a conductive material, a bearing portion, a shaft that is rotatably supported by the bearing portion around a central axis, and the cover. A rotor magnet that rotates together with the shaft in the member, an annular stator that faces the rotor magnet in the radial direction in the cover member, and a circuit board that is disposed perpendicular to the central axis in the cover member And a power line and a ground line connected to the circuit board, and the circuit board comprises a conductive pattern and an electronic component mounted on the conductive pattern, and the conductive pattern extends from the power line. A drive circuit pattern for supplying the power to the stator, a ground pattern to which the ground line is connected, and the drive circuit pattern and the ground pattern. Close to the serial cover member, or, and a cover neutralization pattern in contact with the cover member, the circuit board further comprises a resistor electrically connecting the cover neutralization pattern and the ground pattern.

  According to the present invention, charging of the cover member can be easily reduced or prevented.

FIG. 1 is a front view of the motor. FIG. 2 is a sectional view of the motor. FIG. 3 is a plan view of the stator. FIG. 4 is a plan view of the circuit board. FIG. 5 is a cross-sectional view of a motor according to another example.

  In this specification, the upper side in FIG. 1 of the motor is simply referred to as “upper side”, and the lower side is simply referred to as “lower side”. Note that the vertical direction does not indicate the positional relationship or direction when incorporated in an actual device. The radial direction centered on the central axis is simply referred to as “radial direction”.

  FIG. 1 is a front view of a motor 1 according to an exemplary embodiment of the present invention. The motor 1 is mounted, for example, on an OA (Office Automation) device such as a printer or a time recorder, or a device that transports paper such as a bill validator. In these devices, paper is conveyed by the power of the motor 1. The motor 1 can be mounted on a device that does not transport paper. FIG. 2 is a cross-sectional view of the motor 1. The motor 1 is an inner rotor type, and includes a rotating part 11, a stationary part 12, two sintered oil-impregnated bearings 13, a cover member 14, and a cap member 15. The rotating unit 11 rotates around a central axis J1 that faces in the vertical direction. The rotating part 11 is located inside the stationary part 12.

  The cover member 14 includes a cylindrical portion 141 and a bottom portion 142, and is formed by metal pressing. The bottom 142 extends perpendicular to the central axis J1. The bottom 142 includes a central hole 142a and a plurality of mounting holes 142b. The cylindrical portion 141 extends upward from the outer edge portion of the bottom portion 142. The inner diameter of the cylindrical portion 141 is about 23 mm.

  The cap member 15 extends perpendicularly to the central axis J1 and is fixed to the upper end of the cylindrical portion 141 of the cover member 14. The rotating part 11 and the stationary part 12 are arranged inside the cover member 14 and the cap member 15. A hole 151 is formed in the center of the cap member 15. The sintered oil-impregnated bearing 13 is fixed to the hole 142 a of the bottom 142 of the cover member 14 and the hole 151 of the cap member 15. The motor 1 is attached to the housing by inserting screws into the attachment holes 142b and the attachment holes provided in the equipment housing.

  The rotating unit 11 includes a shaft 21, a rotor holder 22, and a rotor magnet 23. The shaft 21 is inserted into the sintered oil-impregnated bearing 13 and is supported by the sintered oil-impregnated bearing 13 so as to be rotatable about the central axis J1. In FIG. 2, the output side end of the shaft 21 faces downward. The rotor holder 22 includes a shaft fixing portion 221, a connection portion 222, and a cylindrical portion 223. The rotor holder 22 is formed by pressing a thin metal plate. The shaft 21 is fixed inside the shaft fixing portion 221. The connection part 222 extends radially outward from the shaft fixing part 221. The cylindrical portion 223 extends upward from the outer edge of the connecting portion 222. The rotor magnet 23 is fixed to the outer surface of the cylindrical portion 223. The rotor magnet 23 may be cylindrical, or a plurality of magnets arranged in a circumferential direction around the central axis J1.

  The stationary part 12 includes a stator 31 and a circuit board 32. The stator 31 has an annular shape centered on the central axis J1. The stator 31 includes a stator core 311, an insulator 312, and a coil 313. The stator core 311 is fixed to the inner surface 141a of the cylindrical portion 141 of the cover member 14 by press fitting. The rotor magnet 23 is located inside the stator 31 in the radial direction. The stator 31 and the rotor magnet 23 are opposed to each other in the radial direction. The stator core 311 is formed by stacking a plurality of magnetic steel plates in the vertical direction. The insulator 312 covers the upper and lower portions of the stator core 311. FIG. 3 is a plan view of the stator 31. A coil 313 of each phase of U, V, and W is formed on the stator core 311 by winding a conducting wire via an insulator 312.

  When the motor 1 is driven, torque is generated between the stator 31 and the rotor magnet 23 shown in FIG. 2, and the rotor magnet 23 rotates with the shaft 21 in the cover member 14.

  FIG. 4 is a plan view of the circuit board 32. In FIG. 4, the cylindrical portion 141 of the cover member 14 is also shown. The circuit board 32 has a disk shape and is formed by punching a plate member (hereinafter referred to as “original member”) as a base. The circuit board 32 is disposed perpendicular to the central axis J1 in the cover member 14. An edge 321 on the outer periphery of the circuit board 32 is close to or abuts on the inner side surface 141 a of the cylindrical portion 141. The circuit board 32 includes a conductive pattern 41, an integrated circuit 42, a connector 44, a resistor 45, and a Hall element 46 shown in FIG. In addition to the integrated circuit 42, the resistor 45, and the Hall element 46, various electronic components such as a resistor, a capacitor, a transistor, and a photo encoder are mounted on the circuit board 32. The wiring part 43 is connected to the connector 44. The conductive pattern 41 includes a drive circuit pattern 411, a ground pattern 412, and a cover charge removal pattern 413. The circuit board 32 is a double-sided wiring board, and the driving circuit pattern 411 and the ground pattern 412 are connected to the back side of the circuit board 32 through electronic components as appropriate. The circuit board 32 may be a multilayer board having three or more layers.

  The integrated circuit 42 is electrically connected to the driving circuit pattern 411 and the ground pattern 412. The integrated circuit 42 stores a matrix. The matrix indicates the timing of the voltage applied to the coil 313 based on the rotational position of the rotor magnet 23 detected by the Hall element 46 shown in FIG. The wiring unit 43 includes a power line 431, a ground line 432, and two signal lines 433. The signal line 433 is connected to the integrated circuit 42 via the connector 44 and the driving circuit pattern 411. When the motor 1 is driven, a signal for controlling the rotation of the motor 1 is input from the signal line 433 to the integrated circuit 42. Further, power from the power line 431 is supplied to the coils 313 of the respective phases of the stator 31 in FIG. 3 via the driving circuit pattern 411 and various electronic components. The power from the power line 431 may be directly input to the integrated circuit 42.

  The ground line 432 is connected to the ground pattern 412 via the connector 44. The ground pattern 412 is electrically connected to the cover charge removal pattern 413 through the resistor 45. In the present embodiment, the resistance value of the resistor 45 is 100Ω. An outer edge 413 a in the radial direction of the cover charge removal pattern 413 overlaps with an edge 321 on the outer periphery of the circuit board 32. When the circuit board 32 is manufactured, the cover discharging pattern 413 formed on the original member of the circuit board 32 is punched together with the original member, so that the edge 413a of the cover discharging pattern 413 easily matches the edge 321 of the circuit board 32. be able to. Further, the edge 413 a of the cover static elimination pattern 413 is in contact with the inner side surface 141 a of the cylindrical portion 141, or closer to the inner side surface 141 a than the drive circuit pattern 411 and the ground pattern 412.

  By the way, in a device in which the motor 1 is mounted, static electricity is likely to be generated. For example, static electricity is generated when transporting paper or a card. However, in the motor 1, the cover neutralization pattern 413 is provided, thereby preventing or suppressing an increase in the potential of the cover member 14. Specifically, when the cover static electricity removal pattern 413 is in contact with the cover member 14, when the cover member 14 is charged, a current is immediately supplied from the cover static electricity removal pattern 413 to the resistor 45, the ground pattern 412, the connector 44 and the ground wire 432. To the outside of the motor 1. Note that an increase in potential indicates an increase in the absolute value of the potential.

  When the cover charge removal pattern 413 is separated from the cylindrical portion 141, a current flows from the cover member 14 to the cover charge removal pattern 413 due to discharge before the cover member 14 is excessively charged. In addition, by providing the resistor 45 between the cover charge removal pattern 413 and the ground pattern 412, a large current is prevented from flowing through the ground pattern 412 during discharge. As a result, it is possible to prevent the potential of the ground pattern 412 from rising temporarily. This prevents damage to electronic components and driving circuit pattern 411 that are susceptible to electrical damage, such as integrated circuit 42 and Hall element 46 in FIG. When the grounding wire 432 of the motor 1 is grounded together with the grounding wires of other components such as other motors and electronic circuits, the influence on the other components due to the rise of the ground potential is also prevented.

  Although the structure of the motor 1 has been described above, in the motor 1, even when the casing is formed of a non-conductive material such as resin or when the casing cannot be grounded, the cover static elimination pattern By providing 413, charging of the cover member 14 due to static electricity is easily reduced or prevented.

  Further, in the motor 1, the grounding of the cover member 14 is easily realized as compared with the case where the lug terminal is screwed separately to the cover member. Furthermore, the number of parts of the motor 1 can be reduced. It is also possible to easily assemble the motor 1.

  When the outer peripheral edge 321 of the circuit board 32 is separated from the cylindrical portion 141 of the cover member 14, the shortest distance between the cover charge removal pattern 413 and the inner surface 141a of the cylindrical portion 141 is 0.5 mm or less, more preferably It is 0.25 mm or less.

  For example, when the distance between the cover charge removal pattern 413 and the cylindrical portion 141 is 0.24 mm, the maximum value of the charging potential of the cover member 14 in an environment where the electric field intensity at which discharge occurs is approximately 30 kV / cm is 720V. Conventionally, for example, even when static electricity having a potential of about 3 kV to 5 kV is applied, the electronic component is damaged, but in the motor 1, even if static potential of about 10 kV is applied, damage to the electronic component is prevented. It has been confirmed by experiments. Thus, when the distance between the cover charge removal pattern 413 and the cylindrical portion 141 is within the above range, the potential of the cover member 14 is prevented from excessively rising. When it is necessary to further suppress the potential increase of the cover member 14, the shortest distance between the cover charge removal pattern 413 and the cylindrical portion 141 is set to 0.1 mm or less.

  In the motor 1, the cover discharging pattern 413 may be separated from the outer edge 321 of the circuit board 32 as long as it is closer to the cover member 14 than the driving circuit pattern 411 and the ground pattern 412. However, the conductive pattern that does not contribute to the driving of the motor 1 may be provided outside the cover charge removal pattern 413. Also in this case, as described above, the shortest distance between the cover charge removal pattern 413 and the cylindrical portion 141 is 0.5 mm or less, more preferably 0.25 mm or less. This prevents the potential of the cover member 14 from rising excessively. When it is necessary to further suppress the increase in the potential of the cover member 14, the distance is 0.1 mm or less.

  In the circuit board 32, the resistance value of the resistor 45 may be other than 100Ω, and is set to 50Ω or more to suppress the amount of current on the ground pattern 412, and is set to 500Ω or less to prevent damage to the resistor 45. The

  FIG. 5 is a diagram illustrating a motor according to another example. In the motor 1a, a cylindrical bearing holding portion 143 extending upward is provided inside the bottom portion 142 of the cover member 14a. The two sintered oil-impregnated bearings 13 support the central portion of the shaft 21 inside the bearing holding portion 143. An encoder 17 that detects the rotational speed of the shaft 21 is provided on the circuit board 32. The other structure of the motor 1a is almost the same as that of the motor 1. When the potential of the cover member 14a rises due to charging, a current flows from the cover discharging pattern 413 shown in FIG. 4 to the outside of the motor 1a via the resistor 45, the ground pattern 412, the connector 44, and the ground wire 432. Also in the motor 1a, by providing the cover static elimination pattern 413, charging of the cover member 14a can be easily reduced or prevented.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible.

  In the above embodiment, the Hall element 46 may not be provided on the circuit board 32. In this case, for example, the position of the rotor magnet 23 is detected based on the back electromotive force generated between the rotor magnet 23 and the coil 313. The method of providing the cover static elimination pattern 413 on the circuit board 32 may be applied to an outer rotor type motor in which the rotor magnet 23 is located on the radially outer side of the stator 31. In the circuit board 32, the connector 44 may be omitted, and the wiring portion 43 may be directly connected to the driving circuit pattern 411 and the ground pattern 412.

  In the above embodiment, a ground pattern dedicated to the cover charge removal pattern 413 may be provided separately from the ground of the drive circuit pattern 411. However, the structure in which the cover charge removal pattern 413 and the ground pattern 412 are connected via a resistor is particularly suitable when there is no ground pattern dedicated to cover charge removal. In the motor 1, a conductive material other than metal can be used as the cover member 14. A sliding bearing other than a ball bearing or a sintered oil-impregnated bearing may be used as the bearing mechanism for the motors 1 and 1a. The motors 1 and 1a may be mounted on various other devices such as home appliances.

  The configurations in the above embodiment and each modification may be appropriately combined as long as they do not contradict each other.

  The present invention can be used for motors for various purposes.

DESCRIPTION OF SYMBOLS 1 Motor 13 Sintered oil-impregnated bearing 14 Cover member 21 Shaft 23 Rotor magnet 31 Stator 32 Circuit board 41 Conductive pattern 42 Integrated circuit 45 Resistance 46 Hall element 141 Cylindrical part 141a (Cylinder part) inner surface 311 Stator core 321 (Circuit board) Edge 411 Drive circuit pattern 412 Ground pattern 413 Cover static elimination pattern 413a Edge (of cover static elimination pattern) 431 Power line 432 Ground line J1 Central axis

Claims (7)

A cover member formed of a conductive material;
A bearing portion;
A shaft that is rotatably supported about the central axis by the bearing portion;
A rotor magnet that rotates with the shaft in the cover member;
An annular stator radially facing the rotor magnet in the cover member;
A circuit board disposed perpendicular to the central axis in the cover member;
A power line and a ground line connected to the circuit board;
With
The circuit board is
A conductive pattern;
An electronic component mounted on the conductive pattern;
With
The conductive pattern is
A driving circuit pattern for supplying power from the power line to the stator;
A ground pattern to which the ground wire is connected;
A cover static elimination pattern that is closer to or in contact with the cover member than the driving circuit pattern and the ground pattern;
With
The motor, wherein the circuit board further includes a resistor that electrically connects the ground pattern and the cover charge removal pattern.   The motor according to claim 1, wherein the electronic component is an integrated circuit or a transistor.   3. The motor according to claim 1, wherein a part of an edge of the cover charge removal pattern overlaps with an outer peripheral edge of the circuit board.   The motor according to any one of claims 1 to 3, wherein a shortest distance between an inner surface of the cover member and the cover charge removal pattern is 0.5 mm or less.   The motor according to any one of claims 1 to 4, wherein a resistance value of the resistor is 50Ω or more and 500Ω or less.   The motor according to claim 1, which is used for transporting paper.   The motor according to any one of claims 1 to 6, wherein the rotor magnet is positioned on a radially inner side of the stator, and a core of the stator is press-fitted into an inner surface of the cover member.

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