JPH0783581B2 - Brushless motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a brushless motor used in video / audio equipment such as a video tape recorder, an audio cassette tape recorder, and a record player.

2. Description of the Related Art Conventional brushless motors include, for example, National Technical Report Vol. 28, No. 3 (June 1982)
There are brushless motors such as those described on page 168. A conventional example will be described below with reference to FIGS. 3 and 4. FIG. 3 is a side sectional view thereof, and FIG. 4 is a side sectional view of a permanent magnet used therein. Referring to FIG. 3, in the brushless motor 1, a first flat surface portion 2 is magnetized with a predetermined number of poles, and a back yoke 4 made of a magnetic material is brought into contact with the second flat surface portion 3 for adhesion or the like. The first flat surface portion 2 of the annular permanent magnet 5 fixed by the above means and the annular or disc-shaped yoke 6 made of a magnetic material that rotates integrally with the permanent magnet 5 are arranged to face each other. To form a magnetic space, and a rotational position detector 8 for detecting the rotational positions of the stator windings 7 of multiple phases and the permanent magnet 5 is arranged in the magnetic space formed between the facing surfaces. It is provided with a stator flat plate 9 made of a non-magnetic material having an electric wiring portion. The permanent magnet 5 is mainly composed of a sintered magnet such as ferrite or rare earth cobalt alloy. Also,
A rotor boss 10 made of a metal material made of aluminum, an aluminum alloy, brass or the like is fixed to the back yoke 4 by means such as caulking, screwing, or adhering, and the permanent magnet 5 is attached to the rotor boss 10. A motor shaft 11 that rotates integrally with the motor shaft 11 is fixed by means such as press-fitting, adhesion, and screwing. The motor shaft 11 is fitted into bearings 13a and 13b of a bearing member 13 mounted on a motor board 12, is rotatably supported, and is thrust supported by abutting against a thrust receiving member 14.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional brushless motor 1 configured as described above, since the permanent magnet 5 is the above-described sintered magnet, the motor after grinding the permanent magnet 5 is used. It had the drawback that it had to be built into. That is, as shown in FIG. 4, the permanent magnet 5 immediately after sintering
Has a large amount of warpage on the surfaces of the first flat surface portion 2 and the second flat surface portion 3, and if the second flat surface portion 3 is mounted on the back yoke 4 without being ground as it is,
Due to the warp of the surface, the adhesive area of the permanent magnet 5 is reduced, and the adhesive strength is reduced. Therefore, at least the second flat surface portion 3 of the permanent magnet 5 needs to be ground into a flat surface in order to eliminate the warp of the surface.

For this reason, the permanent magnet 5 used for the brushless motor has a cost required for grinding in addition to the material cost.
It was preventing the cost reduction of the brushless motor. Since the permanent magnet 5 must allow for a grinding allowance at the time of grinding and the material for the grinding allowance is wasted, the permanent magnet 5 made of an expensive material such as a rare earth cobalt alloy is used for a brushless motor. In that case, it was a cause of cost increase.

Further, in order to reduce the surface runout of the first flat surface portion 2 of the permanent magnet 5 fixed to the back yoke 4 when the motor rotates, aluminum, aluminum alloy, fixed to the back yoke 4, A fixing portion 10a of the rotor boss 10 made of a metal material made of brass or the like to the back yoke 4
It is necessary to reduce the runout in the motor shaft 11
It was necessary to accurately cut the fixing portion 10a with reference to the hole portion 10b of the rotor boss 10 for fixing and holding the fixing portion 10a. Furthermore, in order to fix and hold the rotor boss 10 to the back yoke 4, an assembling step such as caulking, screwing, bonding, etc. was required.

As described above, in the conventional brushless motor 1, since the rotor boss 10 needs to be ground and the rotor boss 10 needs to be assembled to the back yoke 4, the motor cost can be reduced. It was hindering me.

The present invention has been made in view of the above problems, and provides an inexpensive brushless motor.

Means for Solving the Problems In order to solve the problems, the brushless motor of the present invention includes a motor shaft and a motor shaft that rotates integrally with the motor shaft.
An annular or disk-shaped permanent magnet whose predetermined flat portion is magnetized with a predetermined number of poles, a back yoke made of a magnetic material and arranged on the second flat portion side of the permanent magnet, and the motor. A rotor including a shaft boss made of a metal material for fixing and holding the shaft and a rotor boss made of a resin material for holding and holding the shaft boss, and fixed so as to face the first flat surface portion of the permanent magnet. A non-machined permanent magnet having a stator whose winding is provided on a stator flat plate and manufactured by sintering the permanent magnet, wherein the permanent magnet and the back yoke are The rotor boss is formed by molding so as to hold the shaft boss and cover the entire surface of the permanent magnet with the back yoke and the resin.

Effect According to the present invention, with the above configuration, it is possible to realize a brushless motor that does not require grinding and bonding steps for permanent magnets and that allows the rotor boss to be inexpensively configured.

Example Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. In these figures, the third
The same components as those described in FIG. 4 and FIG. 4 are designated by the same reference numerals.

FIG. 1 is a side sectional view showing an embodiment of the present invention. In the figure, in the brushless motor 15 of the first embodiment, the first flat surface portion 2 is magnetized with a plurality of predetermined pole numbers, and
An annular or disc-shaped permanent magnet 5 with which a back yoke 4 made of a magnetic material is in contact with the flat portion 3 of the first flat portion 3 and the first flat portion 2 of the permanent magnet 5 are opposed to each other with a predetermined gap. Then, a stator flat plate 16 having an electric wiring portion, and a rotational position detector for detecting the rotational positions of the stator windings 7 and the permanent magnets 5 on the stator flat plate 16 having a plurality of phases A stator 20 including 8 is provided. The shaft boss 17 made of a metal material for fixing and holding the motor shaft 11, the permanent magnet 5 and the back yoke 4 are formed in advance by a molding die (not shown).
Etc., and is integrally formed with a rotor boss 18 made of synthetic resin by so-called insert molding, so that the rotor boss 18 is fixedly held or held by the rotor boss 18, and the shaft boss 17 and the permanent magnet 5 are The back yoke 4 constitutes a rotor 19 together with the rotor boss 18. The rotor boss
As shown in FIG. 1, a part 18 a of the end face of the rotor boss 18 is the second end of the permanent magnet 5 of the back yoke 4.
A concave portion that holds the permanent magnet 5 together with the end surface portion 4a that is in contact with the flat surface portion 3 and that is provided in a part of the outer peripheral portion of the rotor boss 18 and has a substantially U-shaped cross section. The end face portion 4a and the end face portion 4b of the back yoke 4 are held in the inside of 18b by holding the back yoke 4. Further, the rotor boss 18 is fixedly held by enclosing the shaft boss 17 made of a metal material in a recess 18c provided in a part of the inner peripheral portion thereof and having a substantially U-shaped cross section. ing. The motor shaft 11 is fitted to the bearing 13a and the bearing 13b of the bearing member 13 attached to the motor substrate 12, is rotatably supported, and is a thrust member (not shown) provided on the stator flat plate 16. Is thrust-supported by and also rotates integrally with the rotor 19.

As described above, according to the present embodiment, the permanent magnet 5 includes the end portion 18a of the resin rotor boss 18 formed by insert molding and the second flat surface portion of the permanent magnet 5 of the back yoke 4. Since it is held by the end surface portion 4a which is in contact with the outer peripheral surface 3, the permanent magnet 5 does not need to be bonded at all when it is incorporated into the back yoke 4. Further, since the bonding step is unnecessary, it is possible to use the as-sintered permanent magnet 5 which is not ground, has a large surface warp.
Therefore, the grinding process of the permanent magnet 5 used for the brushless motor can be omitted, the permanent magnet material is not wasted, and the bonding step can be omitted as described above, so that the cost of the brushless motor can be easily reduced. be able to. Further, a part 18 of the end surface of the rotor boss 18
Since a also has a function as an antioxidant film that prevents contact between the first flat surface portion 2 of the permanent magnet 5 and the outside air, it is easy to oxidize a rare earth cobalt alloy or the like (for example, neodymium iron or the like), When the permanent magnet 5 made of a material that easily causes rust is used in the brushless motor, the permanent magnet 5 can be rust-proofed.

Further, in the rotor boss 10 made of a metal material of the conventional example, assembling means such as caulking, screwing, and adhesion for firmly holding the back yoke 4 is required, whereas in this embodiment, it is formed by insert molding. Since the rotor boss 18 made of resin that holds the back yoke 4 directly holds the back yoke 4, the above-mentioned cutting and assembling means are unnecessary, and the cost of the brushless motor can be easily reduced. . Further, the shaft boss 17 fixedly held so as to be wrapped in a recess 18c having a substantially U-shaped cross section provided in a part of the inner peripheral portion of the rotor boss 18,
Since it is made of a metal material, when the motor shaft 11 is fixedly held by press fitting or the like, the pulling strength of the motor shaft 11 from the shaft boss 17 can be increased, and the motor shaft 11 from the rotor 19 can be removed. It can be prevented from coming off. further,
Even if the magnetic vibration of the motor stator 20 propagates to the rotor 19 and the permanent magnet 5 vibrates at a high frequency, the entire surface of the permanent magnet 5 is covered with the resin-molded rotor boss 18. Therefore, the vibration of the permanent magnet 5 is transmitted to the rotor boss 18 made of resin.
Can be suppressed, and the effect of reducing motor noise can be obtained.

Another embodiment of the present invention will be described below with reference to FIG. FIG. 2 is a side sectional view showing another embodiment of the present invention. The difference from the configuration shown in FIG. 1 is that the position of the permanent magnet 5 with respect to the rotor boss 21 made of synthetic resin and the position of the back yoke 22 with respect to the rotor boss 21 are determined by the back yoke 22 and the rotary yoke. Child boss 21
The point is that one or more positioning holes 22a and 21a are provided at positions approximately in contact with the outer circumference of the permanent magnet 5, respectively.

In the brushless motor 24 having the back yoke 22 and the rotor boss 21 configured as described above, the molding die of the rotor boss 21 is inserted into the inner peripheral portion of the shaft boss 17 in advance, and the molding die is positioned. Positioning pins that are inserted respectively into the positioning holes 22a of the back yoke 22 and the positioning holes 21a of the rotor boss 21 are provided on a pin basis, and the shaft boss 17, the back yoke 22, and the permanent magnet 5 are preformed in a molding die. The rotor boss 21 and the shaft boss 17 and the rotor boss 21.
The positions of 21, the permanent magnet 5, and the back yoke 22 can be determined with high dimensional accuracy, and the outer peripheral runout and end face runout of the rotor 25 can be reduced. In this example, the positioning holes 22a and 21a are provided at positions approximately in contact with the outer circumference of the permanent magnet 5, respectively, but may be provided at positions substantially in contact with the inner circumference of the permanent magnet 5.

EFFECTS OF THE INVENTION As described above, the brushless motor of the present invention has a motor shaft and an annular ring or a circle that rotates integrally with the motor shaft and that is magnetized with a predetermined number of poles on the first plane portion. A plate-shaped permanent magnet, a back yoke made of a magnetic material arranged on the second flat surface side of the permanent magnet, a shaft boss made of a metal material for fixing and holding the motor shaft, and a holding support for the shaft boss. A rotor including a rotor boss made of a resin material, and a stator having a stator winding facing a first flat surface portion of the permanent magnet on a stator flat plate, and The permanent magnet is a non-machined permanent magnet manufactured by sintering, holds the permanent magnet, the back yoke, and the shaft boss, and covers the entire surface of the permanent magnet with the back yoke and the resin. Form the rotor boss by molding so as to cover with Thus, the step of grinding the permanent magnet used for the brushless motor and the step of adhering it to the back yoke can be omitted, and the waste of the material of the permanent magnet is eliminated, so that the cost of the brushless motor can be easily reduced. When a permanent magnet made of a material such as neodymium iron that easily oxidizes and easily rusts is used in a brushless motor, an excellent effect that the permanent magnet can also be rust-proofed can be obtained. Further, since the step of cutting the rotor boss and the means for assembling the rotor yoke are unnecessary, the excellent effect of realizing cost reduction of the brushless motor can be obtained. Furthermore, even if the magnetic vibration of the motor stator propagates to the rotor and the permanent magnet vibrates at a high frequency, the entire surface of the permanent magnet is covered by the resin-molded rotor boss, so the vibration of the permanent magnet Is suppressed, and the effect of reducing motor noise can be obtained.

[Brief description of drawings]

FIG. 1 is a side sectional view of an embodiment of the brushless motor of the present invention, FIG. 2 is a side sectional view of another embodiment of the present invention, and FIG. 3 is a side sectional view of a conventional brushless motor. The figure is a side sectional view of a permanent magnet used in a brushless motor. 4 ... Back yoke, 5 ... Permanent magnet, 7 ... Stator winding, 11 ... Motor shaft, 16 ... Stator flat plate, 17 ... Shaft boss, 18, 21 ... Rotor boss, 19, 25 ... rotor, 20 ... stator.

Claims (1)

[Claims] 1. A motor shaft, a ring-shaped or disk-shaped permanent magnet that rotates integrally with the motor shaft, and is magnetized with a predetermined number of poles on a first plane portion, and the permanent magnet. A magnetic material back yoke arranged on the side of the second flat surface, a metallic material shaft boss for fixing and holding the motor shaft, and a resin material rotor boss for fixing and holding the shaft boss. And a stator having a stator winding on a stator flat plate facing the first flat surface of the permanent magnet, and the permanent magnet manufactured by sintering. A non-machined permanent magnet that holds the permanent magnet, the back yoke, and the shaft boss, and covers the entire surface of the permanent magnet with the back yoke and the resin. A brushless motor having a boss formed by molding.