JP2005229698A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To downsize a motor, which is equipped with a means of detecting its position in rotational direction or its rotational speed, while improving the detection accuracy. <P>SOLUTION: A brushless motor comprises a housing (2); an annular stator (4) which is equipped with a drive coil fixed to its internal perimeter; a circuit board (7) which is arranged in the vicinity of the axial end of the stator and where a drive circuit for controlling the current application to the drive coil is made; a rotor magnet (5) which is arranged diametrically opposite to the stator (4); a rotating shaft (3) which is positioned at the center of the rotor magnet (5) and is supported rotatably to the housing (2); and a rotor yoke (6) which is equipped with a cylinder (6a) centering upon the rotating shaft and is mounted on the internal perimeter of the rotor magnet (5). Furthermore, the brushless motor includes an optical rotation detector comprising a rotation part (8a) which rotates in a body with the rotating shaft (3), being arranged inside the cylinder (6a) of the rotor yoke (6), and detection parts (8b and 8c) which detect the rotation of the rotation part (8a), being arranged on the circuit board (7). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a brushless motor having a rotation detection device.

  Many electronic devices are powered by a motor. In recent years, with the miniaturization and performance enhancement of electronic devices, high rotational accuracy is required for motors used in such devices. Especially when used in a device where the load on the motor fluctuates frequently, the change in the rotation speed of the motor due to the load is detected, and the rotation speed is controlled based on the detected speed change. It is required to quickly return to the steady rotational speed.

  For this purpose, first, it is necessary to detect the position in the rotational direction of the rotor relative to the stator and the rotational speed (rotational speed) at a certain moment with high accuracy.

There are several means for detecting the position and rotational speed of the rotor with respect to the stator.

  For example, as disclosed in Patent Document 1, a magnet having a plurality of magnetic poles that rotate integrally with a rotor is provided, and a current induced in a coil disposed opposite to the magnet or a voltage at an end point is measured to determine the position. There is something to detect. In this case, the detection means can be disposed inside the rotor magnet, and can be miniaturized. However, since a coil for position detection is required in addition to driving, the number of parts is increased.

  Further, in a brushless motor, it is common to detect the position of a rotor magnet using a Hall element or Hall IC to control energization. As an example, Patent Document 2 discloses a device in which a Hall IC is arranged on the inner periphery of a rotor magnet to detect the position of the rotor. If this is the case, the size can be reduced, and the Hall element provided in a general brushless motor can be used effectively.

  However, these methods using a rotating magnet have a limit on the number of magnetized poles, and the number of pulses per rotation cannot be increased. Further, when a rotor magnet used for driving a motor is used for position detection, if the number of magnetized poles is increased in order to obtain rotational torque, the required torque cannot be obtained.

  Therefore, when a particularly high rotational accuracy is required, it is common to use an optical position / speed detector.

  An example is disclosed in Patent Document 3. In the motor of Patent Document 3, a disc with a slit is attached to a rotating shaft, and light incident from the surface of the disc with a slit is read by a light receiving means attached to the back side. The optical rotation detector using the disk with slits can increase detection accuracy by increasing the number of slits carved in the disk with slits.

  However, conventionally, it has been difficult to arrange the rotary detection device inside the motor. This is because the widely used brush motor has an iron core at the center of the coil constituting the rotating body, and therefore the detection means must be arranged outward in the axial direction of the motor unit. In addition, since the light emitting element and the light receiving element are on the front and back of the slit, it is difficult to downsize the detection device in the axial direction.

Japanese Utility Model Publication No. 60-151267 JP 2003-319631 A JP-A-3-78457

  The problem to be solved by the present invention is the improvement and miniaturization of the detection accuracy of a motor provided with detection means for detecting the rotational direction position and rotational speed.

The brushless motor according to claim 1, which is the first invention,
A housing having a cylindrical peripheral wall and an annular stator fixed to the inner peripheral surface of the cylindrical peripheral wall and provided with a drive coil are provided. Further, the brushless motor has a rotating shaft disposed at the center in the radial direction of the cylindrical peripheral wall and rotatably supported via a housing and a bearing, and a cylindrical portion centered on the rotating shaft, and is integrated with the rotating shaft. The rotor yoke has a substantially hollow cylindrical shape that rotates, and a rotor magnet that is attached to the outer peripheral surface of the rotor yoke and faces the stator in the radial direction. The rotation shaft, the rotor yoke, and the rotor magnet constitute a rotor. This brushless motor includes a circuit board on which a drive circuit for controlling energization to a drive coil is disposed near one axial end of a stator, and an optical for detecting the rotational position and / or rotational speed of the rotor. Type rotation detection device. The rotation detection device is housed inside the cylindrical portion of the rotor yoke, and the rotation detection device is configured to determine the rotation direction position and / or rotation speed of the rotation unit mounted on the circuit board and the rotation unit that rotates integrally with the rotation shaft. And a detecting unit for detecting.

Moreover, in claim 2 which is the second invention,
The brushless motor according to the first aspect of the present invention includes a light emitting element that generates light included in a range from infrared to visible light, and a light receiving element that receives the light and converts it into an electrical signal. The rotating portion has a disk shape having a reflecting portion that reflects the light and a slit portion that does not reflect the light.

Moreover, in claim 3 which is the third invention,
The brushless motor of the first or second invention is
In the stator, an insulator having an insulating property is formed at least at an end on the circuit board side in the axial direction end, and the circuit board and the stator are positioned by the insulator.

Moreover, in claim 4 which is the fourth invention,
The brushless motor of the first to third inventions
The rotor yoke is integrally formed with a lid at one end of the cylindrical portion, and a rotation shaft is inserted through the rotation center of the lid of the rotor yoke, and the rotation shaft is fixed relative to the rotor yoke.

In the fifth aspect of the present invention,
The brushless motors of the first to fourth inventions
The housing is constituted by a covered cylindrical housing body integrally formed with an end plate at one end of the cylindrical peripheral wall, and a cover plate attached to the other end opening of the cylindrical peripheral wall. The part is attached close to the end plate part.

In claim 6, which is the sixth invention,
The brushless motors of the first to fifth inventions
A circuit board is arranged at the cover side end of the housing near the axial end of the stator.

  Since the brushless motor of the present invention has the structure as described above, the following operations and effects are achieved.

That is, in the first invention,
This motor is a brushless motor. In the brushless motor, energization is controlled by an electric circuit, and unlike the motor with a brush, the brush and the commutator do not slide to make electrical contact. Therefore, the electric noise generated by the sliding portion does not affect the rotation detection device and the control circuit, and it is possible to prevent the detection accuracy from being lowered. Further, since the rotor is not a winding but a magnet, it is not necessary to arrange an iron core at the center of the motor. Therefore, a columnar space is formed inside the cylindrical portion of the rotor yoke fixed in contact with the inner peripheral surface of the rotor magnet. In addition, since the winding is arranged on the inner peripheral surface of the cylindrical peripheral wall portion of the motor housing, the brushless motor can be thinner in the radial direction than in the inner periphery, and the cylindrical space can be set in the radial direction. Can be further expanded. In this space, the rotating part of the detecting means for measuring the position and rotation speed of the motor can be arranged, so that the motor having the rotation detecting device can be miniaturized. Further, the brushless motor has a circuit board for driving at one end of the stator and the rotor magnet, and it is easy to arrange the detector of the detector on the circuit board.

In the second invention,
Since the rotation detection device uses light included in the range from infrared to visible light, detection is easy. In addition, since the reflection of the light is used, the light emitting element and the light receiving element can be arranged on the same circuit board. Therefore, the position of the light receiving element with respect to the light emitting element is easily fixed, and the motor including the rotation detecting device can be reduced in size and can be easily produced.

In addition, the number of pulses per rotation can be easily changed depending on the number of slits provided in the reflector, and when the motor's specified revolution is low, high accuracy is achieved by using a reflector with a large number of slits in advance. The pulse signal transmission can be maintained.

In addition, the number of pulses per rotation can be increased compared to a rotation detection device that detects the magnetic pole of the rotor magnet using a Hall element / Hall IC, etc., and more accurate detection of the rotational position and rotational speed is possible. Is possible. Also, the jitter accuracy of the output pulse signal is clearer and higher in the optical type than in the case of using the magnetism.

  In the third invention, the position of the circuit board is determined by an insulator fixed to the stator. As a result, the detection unit of the rotation detection device arranged on the circuit board is accurately positioned with respect to the rotation unit, and the accuracy of rotation detection can be ensured.

  In the fourth invention, the rotor yoke is provided with a lid at one end thereof, and the rotor shaft is inserted into the center of the lid, whereby the rotor yoke is fixed relative to the rotation shaft. This makes it possible to expand the space formed in the cylindrical portion of the rotor yoke in the axial direction while securing the engagement length between the rotating shaft and the rotor yoke. As a result, the rotating part of the rotation detecting device can be arranged inside the rotor yoke, and the entire motor is reduced in size.

  In the fifth invention, an end plate portion is integrally formed at one end of the cylindrical peripheral wall of the housing, and a cover plate is attached to the other end. The end plate portion and the lid portion of the rotor yoke are disposed so as to be close to each other. Thereby, since the cylindrical part of a rotor yoke will open one end, the edge part which opens can be used effectively.

  If a ball bearing is used as the bearing of the brushless motor, the outer ring of the ball bearing is fixed to the end plate of the housing. A rotating shaft is inserted through the center of the lid of the rotor yoke, and an elastic body such as a spring is interposed between the lid of the rotor yoke and the inner ring of the ball bearing in order to apply a preload to the inner ring of the ball bearing. Let When the end plate portion of the housing and the lid portion of the rotor yoke are arranged close to each other, the preload applied to the ball bearing becomes constant and the rotation of the rotor becomes stable. Since the rotation accuracy is improved by stabilizing the rotation, the detection accuracy by the rotation detection device can also be improved.

  In the sixth invention, the circuit board is disposed in the vicinity of the end of the housing on the side where the cover plate is attached. This makes it possible to attach the circuit board after attaching the stator and the rotor to the inside of the housing, connect the ends of the windings on the circuit board and connect them, and attach the cover plate. This improves productivity and efficiency during production work. Also, when pulling out the lead wire connected to the equipment on which this brushless motor is mounted from the circuit board, it is easier to pull out the lead wire outside by arranging the circuit board on the cover side, and work to prevent disconnection of the lead wire It becomes possible to improve the property.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view of a brushless motor embodying the present invention.

(1) Configuration of Brushless Motor The brushless motor 1 according to the first embodiment having the configuration according to the present invention includes:
A housing 2 having a cylindrical peripheral wall 2a and an end plate portion 2b at one end thereof, a cover plate 2c fixed to the other end of the housing 2, a stator 4 fixed to the inner peripheral surface of the housing 2, and a housing A rotating shaft 3 positioned at the center of the cylindrical peripheral wall 2a and rotatably supported by the housing 2 via bearings 11a and 11b, and a cylindrical shape centered on the rotating shaft 3 and having an outer peripheral surface of the pole teeth of the stator 4 , The rotor yoke 6 having a cylindrical portion 6a disposed in contact with the inner peripheral surface of the rotor magnet 5, the axial ends of the stator 4 and the rotor magnet 5, and the cover plate A housing 2 near 2c is provided with a circuit board 7 on which a drive circuit for controlling the drive of the brushless motor 1 is formed.

  A disc-shaped reflecting mirror 8 a is attached to the rotating shaft 3. The reflecting mirror 8a is provided with reflecting portions 8a1 that reflect light and slit portions 8a2 that do not reflect light alternately in the circumferential direction. A light emitting element 8b that emits infrared rays toward the reflecting mirror 8a and a light receiving element 8c that generates a pulse signal when receiving light generated by the light emitting element 8b and reflected by the reflecting mirror 8a are provided on the circuit board 7. Has been implemented.

  A hall sensor 10 is mounted on a circuit board 7 on a virtual line extending from the rotor magnet 5 in a direction parallel to the rotation axis 3, and detects the rotational position of the magnetic poles of the rotor magnet 5.

  An insulating insulator 9 is attached to the axial end of the stator 4, and a circuit board 7 is fixed to the insulator 9. The insulator 9 not only provides insulation between the stator 4 and the periphery of the stator 4, but also has an effect of positioning the circuit board 7 on the stator 4.

(2) Rotation Detection Device The brushless motor 1 of the present invention includes a rotation detection device 8 that detects the rotation speed. The rotation detection device 8 includes a reflecting mirror 8 a, a light emitting element 8 b, a light receiving element 8 c, and a control IC 12 disposed on the circuit board 7.

  FIG. 2 is a plan view of the reflecting mirror 8a of the rotation detecting device. When the brushless motor 1 starts rotating, the light emitting element 8b emits infrared light having a wavelength longer than that of visible light. Infrared rays are less likely to be scattered than visible light, and since less light energy is required than visible light, it is possible to reduce power consumption, which is suitable for a rotation detection device that requires high accuracy. Infrared light emitted from the light emitting element 8 b is incident on the reflecting mirror 8 a that rotates integrally with the rotating shaft 3. In the reflecting mirror 8a, reflecting portions 8a1 that reflect infrared rays incident from the light emitting element 8b at a predetermined angle and slit portions 8a2 that absorb or transmit incident infrared rays are alternately provided in the circumferential direction. Infrared light reflected by the reflecting portion 8a1 of the reflecting mirror 8a enters the light receiving element 8c. When the light receiving element 8c senses an infrared ray having a certain intensity or higher, an emitter current is generated in the light receiving element 8c, and a light receiving signal is transmitted. Upon receiving the light reception signal, the control IC 12 transmits one pulse signal. The time from the transmission of one pulse signal to the transmission of the next pulse signal is such that the angle between the two adjacent slits 8a2 of the reflecting mirror 8a is rotated by the reflecting mirror 8a and the entire rotor rotating integrally therewith. It corresponds to time. That is, when the angle between adjacent slits 8a2 arranged at predetermined angular intervals is divided by the time from when one pulse signal is transmitted until the next pulse signal is transmitted, the two pulse signals are The average number of rotations per unit time (rotation speed) during transmission can be calculated. The number of pulses per rotation can be easily changed by using the reflecting mirror 8a having different intervals between the slits 8a2. For example, when the rotation accuracy at low rotation is required, the number of pulses per rotation may be increased by using the reflecting mirror 8a having a large number of slits 8a2 per rotation. As the number of slits 8a2 per round increases, more accurate rotation detection can be performed. However, due to problems such as the processing accuracy of the slits 8a2, a reflecting mirror 8a having about 20 to 100 slits 8a2 per round is used. Used accordingly.

  The pulse signal transmitted from the rotation detection device 8 is input as rotation speed information to a device in which the brushless motor 1 is used, and can be used to measure, for example, a load applied to the brushless motor 1. It can also be used to control the energization of the brushless motor 1 by detecting the difference from the specified rotational speed of the brushless motor 1.

  If slits 8a2 having different angular intervals are arranged on a plurality of circumferences and provided with the same number of detectors as the number of circumferences, not only the rotational speed of the rotor but also the rotational direction of the rotor relative to the stator is provided. Since the absolute position can also be detected, it can be used when information on the position of the rotor in the rotational direction is required, or when energization of the brushless motor 1 is controlled at startup.

(3) When the stator 4 of the rotating brushless motor 1 of the motor is energized, the Hall sensor 10 on the circuit board 7 detects the position of the rotor magnet 5, and a starting current is passed at a predetermined interval. Simultaneously with the energization, the light emitting element 8b starts to emit light.

Compare the difference between the number of revolutions per unit time (hereinafter referred to simply as the number of revolutions) and the steady-state or expected number of revolutions, and if the current number of revolutions is too high, decrease the current value. Deceleration control such as delaying the phase is performed, and acceleration control such as increasing the current value or advancing the phase is performed when the rotational speed is too low.

In addition, signals such as the number of rotations and the position in the rotational direction of the rotor are transmitted to a device in which the motor is incorporated, and are used for controlling a motor in the device and for controlling other devices mounted on the device.

(Other embodiments)
The above example is one of the embodiments of the present invention. Therefore, the present invention is not limited to such an embodiment, and can be modified within the scope of the present invention.

Sectional view of a motor embodying the present invention The top view of the reflective mirror which comprises the rotation detection apparatus of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Brushless motor 2 ... Housing 2a ... Cylindrical peripheral wall 2b ... End plate part 2c ... Cover plate 3 ... Rotating shaft 4 ... Stator 5 ... Rotor magnet 6 ... Rotor yoke 6a ··· Cylindrical portion 6b ·· Lid 7 · · · Circuit board 8 · · · Rotation detector 8a · · Reflector 8b · · Light emitting element 8c · · Light receiving element 9 · · · insulator 10 · · · Hall sensor 11 ... Bearing 12 ... Control IC

Claims (6)

A housing having a cylindrical peripheral wall;
An annular stator fixed to the inner peripheral surface of the cylindrical peripheral wall of the housing and provided with a drive coil;
Arranged at the radial center of the cylindrical peripheral wall of the housing;
A rotating shaft rotatably supported via the housing and a bearing;
A substantially hollow cylindrical rotor yoke having a cylindrical portion around the rotation shaft and rotating integrally with the rotation shaft;
A rotor magnet mounted on the outer peripheral surface of the rotor yoke and facing the stator in the radial direction;
A rotor composed of the rotating shaft, the rotor yoke, and the rotor magnet;
A circuit board formed near the one axial end of the stator and formed with a drive circuit for controlling energization to the drive coil;
An optical rotation detection device that detects a rotational direction position and / or rotational speed of the rotor,
The rotation detection device
A rotating part that is housed inside the cylindrical part of the rotor yoke and rotates integrally with the rotating shaft;
A brushless motor comprising: a detection unit that is mounted on the circuit board and detects a rotation direction position and / or a rotation speed of the rotation unit. The detection unit of the rotation detection device includes a light emitting element that emits light included in a range of infrared to visible light, and a light receiving element that receives the light and converts it into an electrical signal.
The rotation portion of the rotation detection device is substantially disc-shaped provided with a reflection portion that reflects the light generated from the light emitting element and a slit portion that does not reflect the light. The brushless motor according to 1. Among the axial end portions of the stator, an insulator is formed at least on the end portion on the circuit board side,
The insulator has an insulating property,
The brushless motor according to claim 1, wherein the circuit board is positioned by the insulator. The rotor yoke is integrally formed with a lid at one end of the cylindrical portion,
The rotation shaft is inserted through the rotation center of the lid portion of the rotor yoke,
4. The brushless motor according to claim 1, wherein the brushless motor is fixed relative to the rotor yoke. The housing is
A covered cylindrical housing body integrally formed with an end plate at one end of the cylindrical peripheral wall;
A cover plate attached to the opening on the other end of the cylindrical peripheral wall;
The brushless motor according to any one of claims 1 to 4, wherein the rotor yoke is attached in such a manner that a lid portion thereof is close to the end plate portion. The circuit board disposed near the axial end of the stator is
The brushless motor according to claim 1, wherein the brushless motor is disposed in the housing at an end portion on the cover plate side.

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