JPH10108396A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless motor whose permanent magnet is a not damaged. SOLUTION: A brushless motor comprises a stator, which generates a rotating magnetic field, and a rotor, which rotates following up this rotating magnetic field. The rotor is provided with a cylindrical permanent magnet 2, a shaft 1 passing through this cylindrical permanent magnet 2 and balance rings 3, 3 which are provided at both ends of the permanent magnet 2 and through which the shaft 1 is passed. Rounded surfaces 2a are formed at both ends of the inside diameter of the permanent magnet 2 so that the concentration of stress can be dispersed at these round surfaces 2a. This structure prevents the damage to the permanent magnet 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor and, more particularly, to a brushless motor rotation balance mechanism suitable for use as a micromotor used for cutting teeth in dental treatment.

[0002]

2. Description of the Related Art In dental treatment, a micromotor is used for cutting teeth and the like, and a motor with a brush of 2000 to 40,000 rpm is generally used as the micromotor. However, the motor with a brush has a problem that dust is generated from the brush during rotation, which is not only unsanitary but also shortens the life of the motor.

[0003]

For this reason, recently,
Attempts have been made to use brushless motors that do not use brushes.However, it is difficult to balance the rotation of this brushless motor, and if the rotation is not sufficiently balanced, problems such as uneven rotation and noise may occur. there were.

FIG. 2 is a perspective view for explaining an example of a rotor of a brushless motor to which the present invention is applied, and FIG. 3 is a view showing a state where the rotor is disposed in a stator.
In the drawing, 10 is a rotor, 20 is a stator (rotating magnetic field generating unit), and the rotor 10 is composed of a rotating shaft 1, a permanent magnet 2, a balance ring 3, a bearing 4, and the like. The balance ring 3 is integrally attached to the rotating shaft 1 on both sides of the permanent magnet 2. As shown in FIG. 3, the rotor 10 is disposed in a coil (stator) 20 that generates a rotating (or alternating) magnetic field, and rotates following a change in the rotating (or alternating) magnetic field.

[0005]

Thus, in dental treatment, a micromotor is used for cutting teeth.
If the rotational balance is poor, especially when rotating at high speed, the shaft rotates eccentrically and the rotating shaft is bent. As shown by an arrow S in FIG. There is a problem that stress concentration occurs in the portion and the permanent magnet 2 is damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a brushless motor which does not have a possibility that a permanent magnet may be damaged even if a shaft is bent. .

[0007]

According to a first aspect of the present invention, there is provided a brushless motor comprising a stator for generating a rotating magnetic field and a rotor rotating following the rotating magnetic field, wherein the rotor has a cylindrical permanent magnet. And a shaft that penetrates the cylindrical permanent magnet, and a balance ring that is disposed so that the shaft is penetrated at both ends of the permanent magnet.
The two ends of the inner diameter of the permanent magnet are formed on the R surface, so that the permanent magnet is not damaged even if the shaft is bent.

According to a second aspect of the present invention, in the brushless motor according to the first aspect, an end of an outer diameter portion of the balance ring on a side close to the permanent magnet is formed on an R surface, Thus, the permanent magnet is prevented from being damaged by the balance ring.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a main part for explaining an embodiment of the present invention. In FIG. 1, 1 is a shaft, 2 is a cylindrical permanent magnet (magnet), and 3, 3 are In the balancer, as shown in the figure, the shaft 1 penetrates the permanent magnet 2 and the balancers 3, 3, and the permanent magnet 2 is fixed at both ends by the balancers 3, 3, and cuts the balancer 3, 3, etc. , Balancing the whole rotor
This has been done conventionally.

According to the present invention, as shown in FIG. 1, both ends 2 of the inner diameter of the permanent magnet 2 are R surfaces 2a, 2a.
The concentrated stress is distributed on the surfaces 2a, 2a,
The permanent magnet 2 is hardly broken. In addition, the outer diameter end of the balancer 3 on the side close to the permanent magnet 2 is an R surface 3a.
When the shaft 1 is bent, it is possible to prevent the permanent magnet from being damaged by the outer diameter end of the balance ring.

[0011]

As is apparent from the above description, according to the present invention, with a simple structure, a stress applied to both ends of the inner diameter of the permanent magnet can be dispersed, and a brushless motor having no fear of breaking the permanent magnet can be provided. be able to. Further, it is possible to provide a brushless motor that prevents the permanent magnet from being broken by the balancer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a main part for describing an example of a rotor used for carrying out the present invention.

FIG. 2 is a perspective view of a rotor of a brushless motor to which the present invention is applied.

FIG. 3 shows a rotating magnetic field (stator) of the rotor shown in FIG. 2;
FIG. 2 is a cross-sectional configuration diagram of a main part when the device is disposed in the inside.

FIG. 4 is a cross-sectional configuration diagram for explaining stress concentration applied to a permanent magnet when a conventional rotor is decentered on a rotation axis.

[Description of Signs] 1 ... shaft, 2 ... permanent magnet, 2a, 2a ... R surface, 3 ...
Balancer, 3a R surface, 4 bearing, 10 rotor, 20 stator.

Claims (2)

[Claims] 1. A brushless motor comprising a stator for generating a rotating magnetic field and a rotor rotating following the rotating magnetic field, wherein the rotor comprises a cylindrical permanent magnet;
A shaft penetrating the cylindrical permanent magnet, and a balance ring having the shaft penetrated at both ends of the permanent magnet are provided. Both ends of the inner diameter of the permanent magnet are formed on the R surface. A brushless motor. 2. The brushless motor according to claim 1, wherein an outer diameter end of the balance ring on a side close to the permanent magnet is formed on an R surface.