JPS6146157A - Brushless dc motor - Google Patents

Abstract

PURPOSE:To obtain a desired output characteristic by arranging a core inside a suitable number of drive coils of drive coils. CONSTITUTION:A cylindrical bearing projection 12 is projected at the center of a base plate 10, a pair of roller bearings 16, 18 are engaged through a spacer 14 in the projection 12, and a rotational shaft 22 of a rotor 20 as a rotor is rotatably supported via roller bearings 16, 18. A plurality of drive coils 32 wound annularly are secured to the surface opposed to the plate 10 of a printed board 28. A core 30 is disposed in the suitable number of drive coils 32 of the coils 32.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a brushless DC motor, and particularly to a technique for obtaining desired motor output characteristics without changing the characteristics of motor parts or drive circuits.

BACKGROUND OF THE INVENTION In order to obtain desired output characteristics in a conventional brushless DC motor, a motor having the desired output characteristics has conventionally been independently designed. In other words, there are two types of brushless DC motors: coreless motors and cored motors. Coreless motors do not have a core (iron core) in the drive coil, so magnetic resistance increases and output torque decreases, but no-load rotation occurs. It is characterized by a large number. Conversely, a motor with a core has a higher output torque, but a lower no-load rotational speed. Therefore, when designing to obtain the desired output characteristics, first select a coreless motor or a cored motor as appropriate, then change the motor components, the number of coils, the number of turns, and the arrangement position, or drive a brushless morph. Desired motor output characteristics have been obtained by changing the output voltage of the drive circuit.

Problems to be Solved by the Invention However, according to such conventional methods, in order to obtain a motor with desired output characteristics, it is necessary to change the design of the motor parts or the design of the drive circuit each time, which is troublesome. Met. In addition, different parts must be used for each motor with different output characteristics, which increases the manufacturing cost of the motor and makes inventory management of the parts troublesome.

Means for Solving the Problems The present invention has been made against the background of the above-mentioned circumstances, and its gist is that the A rotor having a plurality of magnetic poles on one circumference, and a plurality of annular drive coils disposed at fixed positions along one circumferential direction on the outer peripheral surface or end surface of the rotor. The method of manufacturing a brushless DC motor consists in disposing cores inside an appropriate number of the drive coils in order to obtain desired motor output characteristics.

Operation and Effects of the Invention In this way, the desired motor output characteristics can be obtained by appropriately selecting the number of cores to be arranged in the plurality of drive coils, so new parts are required for each motor. A brushless morph with desired output characteristics can be easily obtained without the need for design or circuit design. Furthermore, since brushless DC motors with different output characteristics are constructed from common parts, there are advantages in that manufacturing costs of the motors are suppressed and inventory management of parts is extremely easy.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows a cross section of the flat brushless morph, in which a cylindrical bearing protrusion 12 is protruded from the center of the base plate 10. A pair of roller bearings 16.18 are fitted into the bearing protrusion 12 via a spacer 14, and a rotating shaft 22 protruding from the center of the rotor 2o as a rotor is fitted into the roller bearings 16.18. is rotatably supported by. The rotor 20 has a flat disk shape and includes a bottomed cylindrical case 24 and a permanent magnet 26 fixed within the case 24. As shown in FIG. 2, for example, the permanent magnet 26 is provided with a plurality of magnetic poles on one circumference on its inner circumference, which correspond to drive coils 32, which will be described later. Further, the outer circumferential portion of the permanent magnet 26 is provided with a large number of fine magnetic poles corresponding to a rotational speed detection pattern 34 to be described later for detecting the rotational speed.

The printed circuit board 28 is fixed to the base plate 10 by screws (not shown) while facing the end face of the permanent magnet 26 with a slight gap therebetween.

The surface of the printed circuit board 28 facing the rotor 20 is configured as shown in FIG. A rotational speed detection pattern 34 is provided for detecting the rotational speed of the printed circuit board 2.
8 is also formed with a through hole 37, and a Hall element 38 for detecting the magnetic pole of the permanent magnet 26 of the rotor 20 is disposed within the through hole 37. Further, a through hole 40 is formed in the printed circuit board 28, and the rotor 2 is inserted through the through hole 40.
Reflective photodetector element 4 that detects the mark 36 attached to 0
2 are arranged. This is for detecting the rotational position of the floppy disk when the brushless DC motor is used to rotate the floppy disk, for example.

On the surface of the printed circuit board 28 facing the base plate 10, a plurality (six in this embodiment) of drive coils 32 wound in an annular shape are fixedly provided. FIG. 4 shows the arrangement of the drive coil 32, and although the printed circuit board 28 is interposed between the drive coil 32 and the rotor 20,
They are disposed facing each other along one circumference of the end surface of the rotor 20 at equal angular intervals. An appropriate number of cores 30 shown in FIG. 5 are disposed within the drive coil 32 as required. In the case of this example, the appropriate number means “
It indicates a number within the range of "0" to "6", and the core 3
When the number of 0s is rOJ, rlJ, or "6", there is only one type of arrangement state, but the number of cores 30 is [2J, 13J.

If it is one of "4", there are a plurality of arrangement states as shown in FIGS. 6, 7, and 8, respectively.

The brushless DC motor configured as described above is driven by, for example, a circuit shown in FIG. 9. That is,
The Hall element 38 is connected to a phase switching signal generation circuit 50, and the signal generated by the phase switching signal generation circuit 50 based on the detection signal of the Hall element 38 generated as the rotor 20 rotates is The information is transmitted to the drive circuit 54 via the switch circuit 52 and the drive coil 32 is excited as appropriate, so that the rotor 2 is
0 is rotated. Further, the drive coil 32 is connected to a friction detection signal generation circuit °56, and is connected to the rotor 20.
Outputs a signal according to the rotation speed.

This signal is compared with the reference signal output from the reference signal generation circuit 60 by the comparator 58, and the comparator 58 is turned on and off.
are respectively energized, whereby the rotor 20 is suppressed to a predetermined rotational speed.

When the brushless DC motor is driven as described above, if the number of cores 30 to be disposed in the drive coil 32 is changed, various motor outputs can be obtained as shown in FIG. 10. In the figure, a indicates the number of cores 30 is "0"
in the case of. C is the number of cores 30 is "2", e is the core 3
When the number of 0's is "4", g indicates the case where the number of cores 30 is "6". In order to obtain a brushless morph with desired output characteristics, the number of cores 30 to be disposed in the drive coil 32 may be determined using the output characteristics diagram shown in FIG. As is clear from the figure, core 30
By adjusting the number of , it is possible to obtain a desired output characteristic between the output characteristic of the coreless morph shown in a and the output characteristic of the cored brushless morph shown in g. According to the inventor's experiments, when the number of cores 30 to be arranged in the drive coil 32 is r2J, r3J or "4", there are arrangement states shown in FIGS. 6 to 8, respectively. Although the drive current/rotation torque characteristics and rotational speed/rotation torque characteristics do not change, the wow and flutter characteristics may differ. For example, when the number of cores arranged in the drive coil 32 is "3", the wow and flutter characteristics are better in the arrangement state shown in (a) or (C1) than in the case shown in tb) of FIG.

Although one embodiment of the present invention has been described above, various modifications can be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention. 2 is a front view showing the arrangement of magnetic poles provided on the rotor of the embodiment shown in FIG. 1. FIG. FIG. 3 is a front view of the printed board shown in FIG. 1 on the rotor side. FIG. 4 is a front view showing the arrangement of drive coils fixed to the printed board of FIG. 3. FIG. 5 is a perspective view showing a core disposed within the drive coil of FIG. 4. FIG. FIGS. 6 to 8 are diagrams showing [R] in the respective arrangement states when there are six drive coils and 2.3 or 4 cores are disposed within the drive coils. FIG. 9 is a block diagram showing a circuit for driving the brushless DC motor of the embodiment shown in FIGS. FIG. 10 is a diagram showing motor output characteristics obtained by adjusting the number of cores to be arranged in the drive coil. 20: Rotor (rotor) 30: Core 32: Drive coil Applicant: Brother Industries, Ltd. Figure 1 Figure 2 26 \~-6. -/'' Figure 6 (a) (b) (C)

Claims (1)

[Claims] (1) A rotor that is rotatable around a single axis and has a plurality of magnetic poles on one circumference on the outer peripheral surface or end surface, and A brushless DC motor is equipped with a plurality of annular drive coils arranged in fixed positions, and in order to obtain desired output characteristics, a core is arranged inside an appropriate number of the drive coils. A brushless DC motor characterized by: