JPS60106354A - Brushless motor - Google Patents

Abstract

PURPOSE:To firmly couple an annular magnet with a back yoke by forming a recess or a projection to be engaged with a projection or a recess formed on the outer periphery of the yoke on the inner periphery of the magnet. CONSTITUTION:A brushless motor 1 has an annular permanent magnet rotor 3 magnetized at a plurality of poles on a flat portion 2 and a plurality of phases of stator windings 5 and a rotor position detector 6 formed on a flat stator plate 4. A back yoke 16 is formed to enclose the permanent magnet 3. A projection or a recess 17 is formed on the outer periphery of the yoke 16, and an annular magnet 19 having a recess or a projection 18 to be engaged with the projection or the recess 17 on the inner periphery is formed on the outer periphery of the yoke 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a brushless motor having rotational frequency detection means (hereinafter referred to as FG) that outputs a frequency signal corresponding to the number of rotations of a rotor. It is effective when used as a drive source for audio/visual equipment.

Conventional configurations and their problems Brushless motors are widely used in audio and video equipment, but are often required to have high-precision rotational performance. A frequency detection means corresponding to the rotation of the child, that is, FG is required. Various types of FG structures have been proposed, including electromagnetic induction and binary systems, but
The electromagnetic induction method is often used for reasons such as low cost.

FIG. 1 shows a side sectional view of an example of a conventional brushless motor having such an electromagnetic induction type FC structure, and FIG. 2 shows a cutaway perspective view of the rotor of the brushless motor. In those drawings, this brushless motor 1 includes a circular permanent magnet rotor 3 magnetized to a predetermined number of poles on a first plane portion 2, and a predetermined gap between the first plane portion 2 and the annular permanent magnet rotor 3. 4 stator plates made of magnetic material and facing each other with
The permanent magnet rotor 3 is made of a magnetic material. The second part of the permanent magnet rotor 3 is attached to the back yoke 7.
The motor shaft 9 rotates integrally with the motor shaft 9. The motor rll+ 9 is rotatably supported by a bearing 11 (c) mounted on the motor board 10, and is thrust supported by a thrust receiver 12 mounted on the stator 4.

As shown in FIG. 1, the back yoke 7id is configured to wrap around the permanent magnet rotor 3.

A rotational frequency detection means (FG) 13 that generates a frequency corresponding to the number of rotations of the permanent magnet rotor 3 is an annular magnet attached to the outer circumference of the back yoke 7 and magnetized on the circumference. 14 and a fixed part near the peripheral surface thereof,
It includes a magnetic detection element 15 that detects changes in the magnetic flux generated by the annular magnet 14. The magnetic detection element 16
consists of a magnetic head y-hole element, an fB air resistance element, etc.

In the conventional brushless motor configured as described above, the annular magnet 14 is attached to the outer circumference of the back yoke 7 by means such as press-fitting or gluing.
There is a drawback that when the motor receives a shock, the annular magnet 14 falls out of the back yoke 7.

In addition, when the annular magnet 14 is made of a resin magnet in which a magnetic material is mixed with a resin material, the coefficient of thermal expansion is larger than that of the bank yoke 7 made of a magnetic material, so that even when subjected to temperature changes, The other drawback is that it easily falls off.Purpose of the InventionThe present invention prevents the same annular magnet for FG from unnecessarily detaching from the back yoke even if an external impact is applied or there is a significant temperature change. The purpose of this is to provide a brushless motor with no problems.

Structure of the Invention The present invention provides an annular main permanent magnet whose first plane part is magnetized with a required number of poles, and a main permanent magnet arranged on a second plane part side of the main permanent magnet. A rotor including a back yoke made of a magnetic material configured to wrap around the outer periphery of a permanent magnet, and a stator winding disposed on a stator flat plate facing a first plane portion of the main permanent magnet. a stator, an annular magnet whose outer peripheral surface is magnetized with multiple poles and which rotates integrally with the rotor, and at least one (magnetic magnet) provided near the peripheral surface of the annular magnet. The back yoke is provided with a rotational frequency detection means including a detection element, and the back yoke has a convex portion or four portions or a convex portion on the outer circumferential surface thereof, and the back yoke substantially fits with the convex portion or the concave portion on the outer circumferential surface of the bank yoke. The annular magnet having four portions or convex portions on the inner circumferential surface portion is formed on the outer circumferential surface portion of the back yoke.

Description of examples Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 3 is a side sectional view of one embodiment of the brushless motor of the present invention, and FIG. 4 is a cutaway perspective view of a rotor in the same embodiment. Since the operation of the brushless motor of this embodiment is essentially the same as the operation of the conventional brushless motor shown in FIG. 1 described above, the explanation here will be omitted. The most distinctive feature of the brushless motor of the present invention is the first
The back yoke 16 corresponding to 7 in the figure has a convex part or a concave part on the outer peripheral surface, and a concave part or a convex part 18 that approximately fits with the convex part or concave part 17.
An annular magnet 19 having an inner circumference formed on the outer circumference of the bank yoke 16 is formed on the outer circumference of the bank yoke 16.

Effects of the Invention With the above-described structure, the annular magnet is firmly connected to the outer circumferential surface of the bank yoke, so even if an external impact is applied, the annular magnet will not be unnecessarily removed from the bank yoke. It is possible to obtain a very excellent effect that there is no Furthermore, even if the annular magnet is made of a resin magnet, even if the brushless motor undergoes a significant temperature change and the annular magnet expands by one thermal expansion, it will not fall out of the back yoke due to the unevenness of the St. This effect can also be obtained.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a conventional brushless motor, Fig. 2 is a cutaway perspective view of the rotor of the conventional brushless motor, and Fig. 3 is a cutaway perspective view of the rotor of the conventional brushless motor.
The figure is a side sectional view of a brushless motor according to an embodiment of the present invention.
FIG. 4 is a cutaway perspective view of the rotor of the same embodiment. 2...First plan view, 3...Main permanent magnet, 4...Stator flat plate, 5...Stator winding, 7... ... Back yoke, 8 ... Second plane part, 13 ... Rotation frequency detection means (F
G), 15... Magnetic detection element, 16...
・Back yoke, 17...Convex part or concave part,
18... Concave or convex portion, 19... Annular magnet.

Claims (1)

[Claims] An annular main permanent magnet whose first plane part is magnetized with a required number of poles, and a ring-shaped main permanent magnet arranged on the second plane part side of the main permanent magnet and which wraps around the outer periphery of the main permanent magnet. a rotor including a back yoke made of magnetic material, and a stator having stator windings disposed on a stator flat plate facing the first plane portion of the main permanent magnet; A rotation comprising an annular magnet whose outer peripheral surface is magnetized with multiple poles and which rotates integrally with the rotor, and at least one magnetic detection element provided near the peripheral surface of the annular magnet. The back yoke is provided with a frequency detection means, and the back yoke has a convex portion or a concave portion on an outer circumferential surface portion, and a concave portion or a convex portion on an inner circumferential surface portion that substantially fits with a convex portion or a concave portion on the outer circumferential surface of the back yoke. A brushless motor characterized in that an annular magnet is formed on the outer peripheral surface of the back yoke.