JP4801713B2 - Brushless DC motor - Google Patents

Description

  The present invention relates to an axial gap type brushless DC motor (hereinafter referred to as a motor) in which a magnet serving as a rotor and an air core coil serving as a stator are opposed to each other via an air gap in the motor axial direction.

Japanese Patent Application Laid-Open No. 59-194647 proposes a configuration in which a transmissive optical sensor is mounted on a motor. In this system, the components that make up a transmission type optical sensor for speed detection are arranged on the outer periphery of motor parts such as magnets (field magnets) that make up the rotor and air core coils (armature coils) that make up the stator. Therefore, it can be seen that the outer diameter of the motor is larger than necessary.

In Japanese Patent Laid-Open No. 6-113495, a Hall element for detecting the magnetic pole position of a magnet is arranged near the center of the air-core coil. If the Hall element is disposed on the outer periphery of the air-core coil, it may be necessary to increase the outer diameter of the motor. Currently, there are many motors in which the Hall element is disposed near the center of the air-core coil.

A speed sensor is required to operate the motor at a constant rotational speed against changes in load, temperature, and power supply voltage.
Conventionally, many frequency generators (hereinafter referred to as FG) have been adopted. The FG amplifies the sinusoidal minute induced voltage obtained by the magnetic flux interlinking with the printed wiring pattern, detects the frequency, and uses it to control the speed of the motor.
Since the radiation of FG is composed of a thin flexible substrate and is inserted between the magnet and the air-core coil, a space-saving arrangement is possible.
In this FG, since the voltage value of the output induced voltage is proportional to the rotation speed of the motor, the induced voltage value becomes even smaller when the motor rotation speed is low, and the SN ratio for disturbance is deteriorated even if amplified. There is a disadvantage that it can not.

  Other speed detection methods built into the motor include transmission and reflection optical sensors and magnetic sensors using MR elements. In any case, the outside of the rotor and stator constituting the motor, that is, the portion other than the rotor and stator is extended in the motor axial direction, and an extra space is secured in the inner and outer diameter directions of the motor. It is necessary to arrange a sensor of the formula, and as a result, the motor volume becomes large. That was a serious drawback.

JP 59-194647 A Japanese Patent Laid-Open No. 6-113495

  In direct drive (DD) motors that directly drive equipment, the rotational speed of the motor is low, so it is necessary to arrange optical and magnetic sensors in a space-saving manner that provide stable output regardless of speed. is there.

  An object of the present invention is to stabilize a motor at a low speed in a motor composed of a ring magnet magnetized with N and S poles at equal intervals in the circumferential direction and a plurality of air-core coils arranged opposite to each other through a gap. Another object of the present invention is to provide a speed sensor capable of outputting the rotation pulse between the stator and the rotor inside the motor, and to provide the motor volume at a low cost with a configuration that does not increase the motor volume more than necessary.

  In order to solve the above-mentioned problem to be solved, the present invention includes a ring magnet having N poles and S poles magnetized at equal intervals in the circumferential direction, and a plurality of ring magnets arranged opposite to each other via a gap. In a motor composed of a single air core coil, a reflective photosensor is built in the air core part of the air core coil, and a disk-shaped reflector with a radiation slit is arranged on the surface facing the air core coil of the ring magnet. The configuration was set up.

According to the present invention, a motor having the following excellent features can be configured.
(1) Speed detection is possible as a relatively high pulse number encoder even at low speeds.
(2) Since the photosensor is built in the air-core coil, the motor can be miniaturized.
(3) Space saving can be achieved by mounting the air-core coil and the photo sensor / Hall element on the same printed circuit board.
(4) A pulse can be generated with high accuracy by attaching a reflector to a magnet.
(5) The distance between the reflector and the photosensor can be set appropriately by the spacer, and pulses can be generated stably.
(6) By separating the area where the photo sensor and hall element are placed from the area where the air core coil is placed, soldering work for the inner lead wire of the air core coil is facilitated, and the motor can be further miniaturized. The wiring of the flexible printed wiring board can be made uniform and can be configured at low cost.
(7) By mounting on a portable infusion pump, the entire apparatus can be reduced in size, and can be configured as a highly reliable device with less vibration.

  Embodiments of the present invention will be described below with reference to the drawings.

A first embodiment of a motor according to the present invention will be described with reference to FIGS.
FIG. 1 shows a cross section of a first embodiment of a motor according to the present invention, wherein 1 is a motor shaft, 2 is a holder including a bearing, 3 is a stator yoke made of a soft magnetic material, and 4 is a motor made of a soft magnetic material. Rotor yoke fixed to the shaft, 5 is a ring magnet in which N poles and S poles are magnetized at equal intervals in the circumferential direction, 6 is an air-core coil, 7 is a reflective photosensor, 8 is a disc-shaped radiation slit , 9 is a printed wiring board made of a flexible material, 10 is a spacer, and 11 is a Hall element that detects the magnetic pole position of the ring-shaped magnet 5.

  FIG. 2 is a set of printed wiring boards for a motor according to the present invention. Reference numeral 12 denotes a round land to which the terminal of the air-core coil 6 is soldered. Reference numeral 19 denotes a deformed land disposed in the air core portion of the air core coil 6, and a round land cannot be formed in the space where the hall element 11 or the photosensor 7 is disposed in the air core coil 6. Reference numeral 13 denotes a slit portion provided in the printed wiring board 9, which is provided in a portion where the photosensor 7 is mounted, and has a structure in which the photosensor 7 can move. Reference numeral 17 denotes a soldering portion at the winding start portion, and 20 denotes a soldering portion at the winding end portion.

  In FIG. 1, a reflecting plate 8 is made of a special metal plate having an outer diameter of 30 mm and a thickness of 0.07 mm, and slits are radially processed with a pitch of 0.1 pitch. A pulse signal can be obtained. Since the reflecting plate 8 is thin and easily deformed, it is generally used by being attached to a reinforcing plate or the like and fixed to the motor shaft. In the present invention, in consideration of space saving, it is indirectly fixed to the motor shaft by being attached to the surface of the ring-shaped magnet 5 made of a sintered material. The surface of the ring-shaped magnet 5 in the motor axial direction is finished very smoothly by polishing, and thin and flat parts such as the reflector 8 can be securely fixed without any distortion. it can.

  In FIG. 2, it can be seen that the hall element 11 and the photosensor 7 are arranged at the center of the air-core coil 6, and all of the motor components that need to be electrically connected are mounted on the printed wiring board 9.

Reference numeral 7 denotes a reflection type photosensor, which basically comprises a photodiode and a phototransistor. In order to generate pulses stably, the air gap between the photosensor 7 and the reflector 8 needs to be set appropriately. Therefore, a slit 13 is provided in the printed wiring board 9 so that the height of the photosensor 7 can be adjusted. Therefore, the spacer 10 is disposed below the photosensor 7.

  FIG. 3 shows a cross section of a second embodiment of the motor according to the present invention, in which a set of printed wiring boards on which electric components are mounted is arranged between the stator yoke 3 and the air core coil 6. The same effect as in the first embodiment can be obtained.

In the embodiment described above, the Hall element 11 or the photosensor 7 is disposed in the air core portion of the air core coil 6, and the winding start portion of the air core coil 6 is soldered. When the motor is further reduced in size, the shape of the air core coil 6 becomes smaller, and in the place where the hall element 11 or the photosensor 7 is arranged in the air core portion of the air core coil 6, the round land 12 cannot be formed because there is little empty space. Since the land 19 is formed, the work of the soldering portion 17 at the beginning of winding becomes difficult. Further, since the soldered portion of the terminal lead wire of the air-core coil is close to the arrangement of the photosensor and the Hall element, there are many cross portions of those wirings, and the pattern of the printed wiring board requires double-sided wiring.

FIG. 5 shows a cross section of a third embodiment of the motor according to the present invention, which is an application example in the case of using it for a further miniaturized motor. FIG. 4 shows a single flexible printed wiring board 18 having a first region 14 in which the photosensor 7 and the Hall element 11 are disposed, a second region 15 in which the air-core coil 6 is disposed, and a connecting portion 16.
When the connecting portion 16 of the flexible printed wiring board 18 is bent, the Hall element 11 and the photosensor 7 are housed in the air core portion of the air core coil 6 where the soldering operation at the beginning and end of winding is completed and is designed in a positional relationship. ing.
Further, since the pattern wiring of the flexible printed wiring board 18 in the third embodiment can be separated into the air-core coil 6, the photo sensor 7 and the hall element 11, the pattern wiring can be performed on one side and can be manufactured at low cost.

  By mounting the motor of the present invention on a portable infusion pump such as a medical device that is strongly required to be small and light, it is possible to drive with little cogging torque and small torque pulsation by taking advantage of the characteristics of the coreless motor. Because the speed sensor is a photo system, it is resistant to electromagnetic noise and is less likely to malfunction. In addition, although the rotational speed of the motor is reduced due to the DD method, a relatively large number of pulses can be obtained from the photosensor, a stable low-speed constant speed control system can be configured, and the constant speed rotation can be maintained, so reliability Higher size and weight can be realized.

  Furthermore, the rotational direction of the motor can be determined by a method of discriminating the phase by using the photosensor 7 as a two-phase output and a rotational direction in two systems in which the phase of the output of the Hall element 11 for the three phases of the motor is determined. Reliability can be improved in a system such as an infusion pump such as a medical device that does not allow reverse rotation during treatment.

According to the present invention, it is possible to detect the speed of a motor as an encoder having a relatively high pulse number even at a low rotational speed while being small. In addition, a photo sensor is built into the air-core coil of an axial gap type coreless brushless DC motor, and a reflector is attached to the surface of the ring-shaped magnet to stabilize the speed without increasing the external dimensions of the motor. It is possible to configure a control system that can detect and maintain constant rotation.
If such a motor is used in a device having a portable infusion pump function, it has a special effect of being small and light and having high rotational reliability, and can be widely applied.

Structure diagram of motor of first embodiment according to the present invention Assembly diagram of printed wiring board of motor of first embodiment according to the present invention Structural diagram of a motor according to a second embodiment of the present invention. Assembly drawing of flexible printed wiring board of motor of third embodiment according to the present invention Structural diagram of a motor according to a third embodiment of the present invention.

Explanation of symbols

1: Motor shaft
2: Holder including bearing 3: Stator yoke
4: Rotor yoke 5: Ring magnet 6: Air core coil 7: Photo sensor 8: Reflector 9: Printed wiring board 10: Spacer 11: Hall element 12: Round land 13: Slit 14: First region 15: Second Area 16: connecting portion 17: winding start soldering portion 18: flexible printed circuit board 19: deformation land 20: winding end soldering portion

Claims (6)

In an axial gap type brushless DC motor composed of a ring-shaped magnet having N poles and S poles magnetized at equal intervals in the circumferential direction and a plurality of air-core coils disposed opposite to the ring-shaped magnets through a gap, the photosensor of the reflection type in the air-core portion of the air-core coil is disposed, the a surface of the ring-shaped magnet is opposed to the air-core coil, and disposing a reflector plate having a disk-shaped radial slits, said photosensor and said The air-core coil is mounted on one printed wiring board, and a slit is provided in a part of the printed wiring board so that the height of the mounting portion of the photosensor on the printed wiring board can be adjusted. An axial gap type brushless DC motor characterized in that the distance of the photosensor can be adjusted . A hall element for detecting the magnetic pole position of the magnet is provided, the hall element is mounted on the one printed wiring board together with the air core coil and the photosensor, and the hall element is disposed in the air core portion of the air core coil. axial gap type brushless DC motor according to claim 1, characterized in that the. 3. The axial gap type brushless DC motor according to claim 1, wherein the printed wiring board is disposed on the surface of the air-core coil supported by a stator yoke so as to face the reflecting plate . 3. The axial gap type brushless DC motor according to claim 1, wherein the printed wiring board is disposed between the air-core coil and a stator yoke that supports the air-core coil . The one printed wiring board is connected to a first region in which the photosensor and the Hall element are disposed, a second region in which the air-core coil is disposed, and the first region and the second region. A flexible printed wiring board having a connecting part to be bent, the connecting part of the flexible printed wiring board is bent, and the photo sensor and the Hall element are positioned on the upper surface of the air core part of the air core coil. The axial gap type brushless DC motor according to claim 1 , wherein the axial gap type brushless DC motor is arranged . The axial portion according to any one of claims 1 to 5, wherein a mounting portion of the photosensor on the printed wiring board is supported by a spacer that appropriately sets a distance of the photosensor with respect to the reflection plate. Gap type brushless DC motor.

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