JP2009273292A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless motor capable of preventing, with a simple structure, sticking of dust to an optical encoder and preventing contact between a shaft and an insert member such as wiring inserted into the shaft. <P>SOLUTION: A brushless motor 1 is attached with a motor cover 50. The motor cover 50 comprises a shaft cover 18 which is almost cylindrical and arranged inside the shaft 4, and an encoder cover 17 which is integrally formed at an outer side substantially in radial direction from one end part 18c forming one opening 18c of the shaft cover 18. The shaft cover 18 prevents a wiring 19 from slidingly contacting the shaft 4. The encoder cover 17 covers an encoder 13, to prevent dust from sticking to the encoder 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a brushless motor having a hollow shaft.

  The brushless motor includes an annular stator main body attached to the inner side of the motor case, and a stator having a plurality of salient poles integrally protruding from the inner peripheral surface of the stator main body. And a rotor disposed rotatably inside the stator. The rotor has a cylindrical shaft and a magnet attached to the outer peripheral surface of the shaft. In general, the shaft has a solid cylindrical shape, but there is a brushless motor in which the shaft has a hollow cylindrical shape, a space portion is provided inside the shaft, and the space portion is effectively used. For example, in the brushless motor of Patent Document 1, a lens that is a driven body is arranged in a space portion inside a shaft to reduce the size of the motor system.

  Thus, various utilization forms of the space portion of the hollow cylindrical shaft can be considered. For example, when a brushless motor having a hollow shaft is used as a drive source for an arm of an industrial robot, an insertion member such as a wiring of various sensors is introduced from one end of the hollow cylindrical shaft, and from the other end. The usage form to discharge is also considered.

On the other hand, when used as an arm drive source for an industrial robot, it is necessary to detect the rotational position of the rotor with higher accuracy. In such a case, an optical encoder using an optical sensor is used as a highly accurate rotation detection means. Optical encoders are required to sense light with high sensitivity, and need to be finely adjusted after the sensation motor is assembled. Therefore, after the motor is assembled, it is necessary to have a structure in which an encoder ring is attached to the shaft from the outside of the motor and an optical sensor is attached to the motor body from the outside of the motor.
Japanese Patent Laid-Open No. 6-22519

  However, in the case of the utilization form in which the insertion member such as the wiring is inserted into the shaft as described above, the shaft opening and the inner peripheral surface are in sliding contact with the wiring due to the rotation of the shaft, and the coating of the wiring is performed. There is a risk of damage.

  On the other hand, in the optical encoder, when dust or the like from the outside adheres to the encoder ring, the waveform signal of the reflected light is distorted and the rotational position cannot be detected with high accuracy. Therefore, it is also required to have a structure in which dust or the like from outside does not adhere to the encoder ring of the optical encoder.

  Therefore, an object of the present invention is a brushless motor that has a simple structure and can prevent dust and the like from adhering to the optical encoder, and can prevent contact between the shaft and an insertion member such as wiring inserted into the shaft. It is to provide.

  In order to solve the above-described problems, a brushless motor according to the present invention includes a stator case formed in a substantially cylindrical shape, a substantially disk shape formed with a through hole in a central portion, and the opening of the stator case is closed. A pair of brackets, a stator body formed in a substantially annular shape and attached to the inner wall of the stator case, and a plurality of salient poles projecting radially inward from the inner peripheral surface of the stator body. A stator, a coil wound around each of the salient poles of the stator, and a shaft that is formed in a hollow cylindrical shape and is rotatably supported by the pair of brackets through the through holes of the pair of brackets. A brushless motor comprising: a magnet supported by the shaft; and a rotor disposed opposite to the salient poles of the stator. The shaft of the siles motor includes a protruding portion protruding to the outside from a through hole of one bracket of the bracket, and the brushless motor includes a substantially disc-shaped slit plate on an outer peripheral surface of the protruding portion of the shaft. An encoder ring having an attached sensor ring, a sensor element, the sensor element facing the slit plate of the encoder ring, and an optical sensor attached to the one bracket, and a substantially cylindrical shape A shaft cover portion disposed inside the shaft, and an encoder that is integrally formed with the shaft cover portion substantially radially outward from one end portion that forms one opening of the shaft cover portion and covers the encoder And a motor cover attached to the one bracket on the outside of the encoder. Provided with a door.

  In this way, by adopting a structure in which the motor cover that is integrally provided with the encoder cover portion and the shaft cover portion is attached to the brushless motor, dust and the like can be prevented from adhering to the optical encoder with a simple structure, and the inside of the shaft can be prevented. Contact between the insertion member such as the inserted wiring and the shaft can be prevented.

  Next, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of the brushless motor according to the first embodiment. FIG. 2 is a perspective view illustrating attachment of the motor cover to the brushless motor. FIG. 3 is a longitudinal sectional view of the brushless motor of the first embodiment indicated by the A plane in FIG. FIG. 4 is a cross-sectional view of the brushless motor of the first embodiment indicated by the B plane in FIG.

  The brushless motor 1 includes a motor case 7, a stator 2 attached to the inside of the motor case 7, and a rotor 3 that is rotatably arranged inside the stator 2. The motor case has a substantially cylindrical stator case 8 and a rear bracket (bracket) 9 which is formed in a substantially disk shape and has a through hole 9a formed in the center, and is closed at one end of the stator case 8. And a front bracket (bracket) 10 that is formed in a substantially disk shape, has a through hole 10a at the center, and is disposed with the opening closed at the other end of the stator case. Note that the stator case 8, the rear bracket 9, and the front bracket 10 are formed of an aluminum alloy in order to reduce the weight and efficiently dissipate heat generated in the stator 2.

  The stator 2 is formed by laminating thin magnetic steel plates, and has a substantially annular stator body 2a and 15 salient poles integrally projecting radially inward from the inner peripheral surface of the stator body 2a. ing. The stator 2 is press-fitted into the stator case 8 and attached to the inner wall of the stator case 8 by the stator body 2a.

  The rotor 3 includes a hollow cylindrical shaft 4 made of a magnetic material, and a ring magnet (magnet) 5 attached and fixed to the outer peripheral surface of the shaft 4 with an adhesive. The ring magnet 5 is formed of, for example, a rare earth element such as neodymium (Nd—Fe—B), and is magnetized alternately in the circumferential direction in the order of N pole, S pole,. Is the pole. An insertion member such as a wiring is inserted through the hollow cylindrical shaft 4.

  A concave portion 9 b is provided in the central portion of the rear bracket 9, an outer race of the bearing 11 is inserted into the concave portion 9 b, and the bearing 11 is attached to the rear bracket 9. On the other hand, a recess 10 b is provided at the center of the front bracket 10, and an outer race of the bearing 12 is inserted into the recess 10 b, and the bearing 12 is attached to the front bracket 10.

  The reduced diameter portion 4 d on the rear bracket 9 side of the shaft 4 is inserted into the inner race of the bearing 11, and the reduced diameter portion 4 e on the front bracket 10 side is inserted into the inner race of the bearing 12. As described above, the shaft 4 of the rotor 3 is supported by the bearings 11 and 12 attached to the rear and front brackets 9 and 10, and the rotor 3 is rotatably arranged inside the salient pole 2 b of the stator 2.

  The shaft 4 includes a cylindrical projecting portion 4 a integrally projecting from one end of the shaft 4 from the through hole 9 a of the rear bracket 9 to the outside of the motor case 7, and the shaft from the through hole 10 a of the front bracket 10 to the outside of the motor case 7. 4 is provided with a cylindrical output portion 4b integrally projecting from the other end of 4. A planetary speed reducer (not shown) is attached to the output unit 4b, and the rotation of the shaft 4 is decelerated by the speed reducer and output to the outside.

  A resin insulator 20 is attached to each of the 15 salient poles 2b of the stator 2 to ensure insulation. And the conducting wire is wound around the outer peripheral surface of the insulator 20 by concentrated winding, and the coil 6 is formed on each of the salient poles 2b. The conducting wire at the beginning and end of winding of each coil 6 is entangled with a pin 20 a integrally formed at one end of the insulator 20, and the pin 20 a is electrically and mechanically connected to the power distribution board 21. .

  A power distribution pattern is formed on the power distribution board 21. The power distribution pattern in which the circumferentially arranged coils 6 become a U-phase coil 6a, a V-phase coil 6b, a W-phase coil 6c,. It has become. A lead wire 18 is connected to the power distribution board 21, and a control signal corresponding to the rotational position of the rotor 3 is supplied to an external driver (not shown) to the U-phase coil 6a, V-phase coil 6b, and W-phase coil 6c. Supplied from

  As described above, since the control signal corresponding to the rotational position of the rotor 3 is supplied to the U-phase coil 6a, the V-phase coil 6b, and the W-phase coil 6c, it is necessary to accurately detect the rotational position of the rotor 3. Here, the brushless motor 1 according to the present embodiment is used as an actuator for driving an arm of an industrial robot or the like that is required to drive with high accuracy in positioning, and detects the rotational position of the rotor 3 with high accuracy. There is a need. Therefore, the brushless motor 1 of the present embodiment uses the optical encoder 13 as the rotational position detection means.

  The optical encoder 13 includes an encoder disk 14 and an optical sensor 15. The encoder ring 14 includes a ring-shaped encoder ring main body 14a and a disk-shaped slit plate 14b attached to an end surface of the encoder ring main body 14a. A male screw is formed on the outer peripheral surface of the first protrusion 4a, while a female screw is formed on the inner peripheral surface of the encoder ring body 14a, and the reflective disk main body 14a is a screw on the outer peripheral surface of the first protrusion 4a. Installed by fitting. Note that 1024 slits are formed in the slit plate 14b.

  The optical sensor 15 includes a sensor element 15a attached to the sensor substrate 15b and a sensor wiring 15c that outputs a signal from the sensor substrate 15b to the outside. The optical sensor 15 is fixed to the rear bracket 9, and at this time, the sensor element 15 a is arranged at a position away from the slit plate 14 b of the encoder disk 14 and facing the slit plate 14 b. The sensor element 15a includes a light emitting unit (not shown) that emits irradiation light to the slit plate 14b and a light receiving unit (not shown) that receives reflected light from the slit plate 14b. The rotational position signal of the rotor 3 is detected from the waveform signals of the light and the reflected light.

  In order to protect the optical encoder 13 from external dust and the like, and to prevent sliding contact between the insertion member such as wiring inserted into the hollow cylindrical shaft 4 and the shaft 4, A motor cover 50 is used. As shown in FIG. 2, the motor cover 50 is formed in a substantially cylindrical shape, and includes a shaft cover portion 18 disposed inside the shaft 4 and an encoder cover portion 17 formed integrally with the shaft cover portion 18.

  The shaft cover portion 18 is set to be slightly longer than the axial length of the shaft 4, and the end portions 18 a and 18 b of the shaft cover portion 18 slightly protrude from the end surfaces of the protruding portion 4 a and the output portion 4 b of the shaft 4. .

  The encoder cover portion 17 includes a substantially disc shape and a bottom portion 17b integrally formed radially outward from one opening end (one end portion) 18a forming one opening 18c of the shaft cover portion, and an outer periphery 17c of the bottom portion. And a cylindrical portion 17a integrally formed in the direction of the rear bracket 9. Further, a flange-shaped opening 17d is formed in the opening of the cylindrical portion 17a. As shown in FIG. 2, the shaft cover portion 18 is inserted into the shaft 4 from the rear bracket 9 side, and the opening portion is opened. It is attached to the rear bracket 9 at 17d.

  By attaching the motor cover 51 in which the shaft cover portion 18 and the encoder cover portion 17 having such a structure are integrally formed to the brushless motor 1, the following effects are obtained. That is, the sliding contact between the insertion member 30 and the shaft 4 can be prevented by interposing the shaft cover portion 18 between the insertion member 30 and the inner periphery of the shaft 4. Further, by covering the optical encoder 13 with the encoder cover portion, it is possible to prevent dust and the like from adhering to the optical encoder 13. Furthermore, these effects can be performed only by the motor cover 51, and the structure is simple.

  A second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a longitudinal sectional view of a second embodiment of the brushless motor indicated by the A plane in FIG. The second embodiment differs from the first embodiment only in the structure between the shaft 4 and the shaft cover part 18 and between the shaft 4 and the shaft cover part, and the other structures are the same. Therefore, only the structure of the shaft 4 and the shaft cover part 18 and the structure between the shaft 4 and the shaft cover part will be described, and the description of the other structures will be omitted.

  As shown in FIG. 5, the inner peripheral portion 4 c of the output portion 4 b of the shaft 4 has a larger diameter than the other inner periphery of the shaft 4. The outer race of the first rolling bearing (first sliding member) 31 is inserted into the inner periphery of the circumferential portion 4 c, while the first rolling bearing (first sliding member) 31 is inserted. The outer periphery of the shaft cover portion 18 is inserted into the inner periphery of the inner race. In this manner, the first rolling bearing 31 is disposed between the inner periphery of the shaft 4 and the outer periphery of the shaft cover portion 18 in the vicinity of the other opening 18d of the shaft cover portion 18.

  As described above, the first rolling bearing 31 is disposed between the inner periphery of the shaft 4 and the outer periphery of the shaft cover portion 18 in the vicinity of the other opening 18d of the shaft cover portion 18, whereby the shaft It is possible to prevent sliding contact between the inner periphery of the shaft 4 and the outer periphery of the shaft cover portion 18.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a longitudinal sectional view of a third embodiment of the brushless motor indicated by the A plane in FIG. The third embodiment differs from the first embodiment only in the structure between the shaft 4 and the shaft cover part 18 and between the shaft 4 and the shaft cover part, and the other structures are the same. Therefore, as in the first embodiment, only the structure of the shaft 4 and the shaft cover part 18 and the structure between the shaft 4 and the shaft cover part will be described, and the description of the other structures will be omitted.

  As shown in FIG. 5, the first rolling bearing (first sliding member) 31 is located in the vicinity of the other opening 18 d of the shaft cover portion 18, and the inner periphery of the shaft 4 and the outer periphery of the shaft cover portion 18. The second rolling bearing (second sliding member) 32 is disposed between the inner periphery of the shaft 4 and the outer periphery of the shaft cover portion 18 in the vicinity of the one opening 18c of the shaft cover portion 18. Between.

  As described above, the shaft cover portion 18 is held with respect to the shaft 4 by the first and second rolling bearings 31 and 32, so that the space between the inner periphery of the shaft 4 and the outer periphery of the shaft cover portion 18 is increased. This sliding contact can be appropriately prevented not only near the first opening end 18a but also near the second opening end 18b.

It is a perspective view of the brushless motor in the 1st embodiment of the present invention. It is a perspective view explaining attachment to a brushless motor of a motor cover. It is a longitudinal cross-sectional view of the brushless motor of 1st Embodiment instruct | indicated by A in FIG. It is a cross-sectional view of the brushless motor of the first embodiment indicated by B in FIG. It is a longitudinal cross-sectional view of the brushless motor of 2nd Embodiment instruct | indicated by A in FIG. It is a longitudinal cross-sectional view of the brushless motor of 3rd Embodiment instruct | indicated by A in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Stator 2a Stator main body 2b Salient pole 3 Rotor 4 Shaft 4a Projection part 4b Output part 4c Inner peripheral part 5 (Ring) Magnet 6 Coil 7 Motor case 8 Stator case 9 Rear bracket (bracket)
9a First through hole (through hole)
10 Front bracket (bracket)
10a Second through hole (through hole)
13 Optical encoder 14 Encoder ring 14a Encoder ring body 14b Slit plate 15 Optical sensor 15a Sensor element 17 Encoder cover portion 17a Cylindrical portion 17b Disc portion 17c Outer periphery 17d Opening portion 18 Shaft cover portion 18a First open end (one end portion) )
18b Second opening end 18c One opening 18d The other opening 31 First rolling bearing (sliding member)
32 Second rolling bearing (sliding member)
50 Motor cover

Claims (5)

A stator case formed in a substantially cylindrical shape;
A pair of brackets formed in a substantially disk shape, with a through hole formed in the center, and disposed with the opening of the stator case closed;
A stator having a substantially annular shape and having a stator body attached to the inner wall of the stator case, and a plurality of salient poles projecting radially inward from the inner peripheral surface of the stator body;
A coil wound around each of the salient poles of the stator;
A shaft formed in a hollow cylindrical shape, inserted through the through holes of the pair of brackets and rotatably supported by the pair of brackets, and a magnet supported by the shafts, In a brushless motor comprising a rotor disposed oppositely,
The shaft of the brushless motor includes a protruding portion that protrudes to the outside from a through hole of one bracket of the bracket,
The brushless motor is
An encoder ring attached to the outer peripheral surface of the projecting portion of the shaft; and a sensor element, the sensor element facing the slit plate of the encoder ring, An encoder having an optical sensor attached to one of the brackets;
A shaft cover part formed in a substantially cylindrical shape, and integrally formed with the shaft cover part substantially radially outward from one end forming one opening of the shaft cover part; A brushless motor, comprising: an encoder cover portion that covers the encoder; and a motor cover attached to the one bracket on the outside of the encoder.   2. The brushless motor according to claim 1, wherein the encoder carver portion includes a substantially disk-shaped bottom portion integrally formed radially outward from one end portion that forms the one opening, and the one side from the outer periphery of the bottom portion. And a cylindrical portion integrally formed in the bracket direction, and an opening of the cylindrical portion is attached to the one bracket.   3. The brushless motor according to claim 2, further comprising at least one sliding member formed in a substantially annular shape and disposed between an inner periphery of the shaft and an outer periphery of the shaft cover portion. Brushless motor.   4. The brushless motor according to claim 3, further comprising a first sliding member, wherein the first sliding member is disposed in the vicinity of the other opening of the shaft cover portion. 5. The brushless motor according to claim 4, further comprising a second sliding member, wherein the second sliding member is disposed in the vicinity of the one opening of the shaft cover portion. .

Images