JPH0112543Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to the structure of a brushless motor, and particularly to a direct drive type brushless motor used in a capstan motor or the like.

Prior Art FIG. 1 is a sectional view of a brushless motor used as a conventional direct drive capstan motor. The rotor shaft 1 is integrally attached to a dish-shaped rotor yoke 2, and
The stator yoke 3 is rotatably supported by bearings 5, 6, and 7 attached to a bearing support portion 4 attached to the stator yoke 3. A ring-shaped magnet 8 having a rectangular cross section and having NS poles alternately magnetized is fixed to the rotor yoke 2, and the magnet 8 is fixed to the stator yoke 3.
A multi-phase armature coil 9 is installed opposite to.

Further, a position detection element such as a Hall element is attached to the stator yoke 3 to detect the position of the magnetic pole of the magnet 8, and according to this detection signal, a drive current is passed from the drive circuit to the armature coil 9, and the magnet 8 and The rotor rotates as the armature coil 9 repeats attraction and repulsion.

Brushless motors with this type of structure have the advantage of being able to use the rotor shaft 1 itself as a capstan shaft, since uneven rotation of the motor is small due to ease of energization control, etc. Widely used as a stun motor.

However, if the above-mentioned motor is, for example, a 3-phase 8-pole motor, the drive current is switched 3×8=24 (times) during one rotation of the rotor, and the armature coil 9 and magnet 24 attraction/repulsion effects occur during the 8-hour period, and vibrations accompanying the attraction/repulsion force are transmitted to the rotor shaft 1 via the rotor yoke 2 to which the magnet 8 is fixed, resulting in uneven rotation of the motor. This rotational unevenness is calculated by assuming that the motor rotation speed is 1.3 revolutions/second.
This results in uneven rotation with a frequency of 1.3×24=31.2Hz.

In order to solve the above-mentioned difficulties, the present inventors first developed a brushless motor in which a magnet is fixed to a rotor yoke via a vibration-absorbing elastic material in order to absorb the vibration caused by the attraction and repulsion of the magnet. Proposed.

However, in such a structure, since the elastic material is highly flexible, the position of the magnet easily fluctuates, causing the magnet to fluctuate in the radial direction, causing chattering between the magnet and the rotor yoke.
The vibrations are transmitted to the rotor shaft, resulting in uneven rotation of the motor.

Purpose of the invention The purpose of the invention is to reduce the uneven rotation caused by the vibration of the magnet described above, and to improve wow and flutter.

Structure of the invention The present invention has been made to achieve the above object, and it fixes the magnet to the bottom of the rotor yoke via a vibration-damping elastic material, and also prevents radial vibration between the circumferential surface of the magnet and the rotor yoke. This feature is characterized by the provision of a spacing retainer to prevent this.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 2 to 5. Fig. 2 is a cross-sectional view of a brushless motor used as a direct drive capstan motor, Fig. 3 is a cross-sectional view of the rotor portion, and Fig. 4 is a longitudinal cross-sectional view of the rotor portion showing a different embodiment. FIG. 5 is a cross-sectional view of the rotor portion. Note that the same parts as in the conventional example are given the same figure numbers.

3 is a stator yoke to which a multiphase armature coil 9 is applied, constituting the stator. 10 is a rotor, which includes a dish-shaped rotor yoke 2 and a ring-shaped magnet 8 with a rectangular cross section, in which NS poles are alternately magnetized.
, a rotor shaft 1 attached to a rotor yoke 2, and a vibration damping elastic material 11 interposed between the rotor yoke 2 and the magnet 8.

Reference numeral 4 designates a bearing support portion, which is attached to the stator yoke 3, and rotatably supports the rotor shaft 1 with bearings 5, 6, and 7 installed inside.

Now, as mentioned above, the rotor 10 of the present invention
The magnet 8 is fixed to the rotor yoke 2 via a vibration damping elastic material 11, and vibrations caused by the attraction and repulsion action of the magnet 8 are absorbed by the elastic material 11. As the elastic material 11, a rubber having extremely high elastic followability, such as silicone rubber, may be used.

Furthermore, the rotor 10 of the present invention is provided with a spacing retainer 12 between the circumferential surface of the magnet 8 and the rotor yoke 2 to prevent vibration in the radial direction.
As shown in FIGS. 2 and 3, for example, this retainer 12 is provided with several recesses 13 in a facing portion 2a facing the circumferential surface of the magnet 8.
A non-magnetic ball is arranged between the magnet 8 and the circumferential surface of the magnet 8 to suppress vibration of the magnet 8 in the radial direction. That is, the rotation of the ball-shaped retainer 12 absorbs the radial vibration of the magnet 8 and prevents the vibration of the magnet 8 from being transmitted to the rotor shaft 1.

Further, the retainer 12 may be arranged on the inner peripheral surface side of the magnet 8 as shown in FIGS. 4 and 5. In that case, it is necessary to provide a facing portion 2a at a portion of the rotor yoke 2 located on the inner peripheral surface side of the magnet 8.

Incidentally, in the above-described embodiment, a case was described in which the ball-shaped retainer 12 was disposed between the circumferential surface of the magnet 8 and the rotor yoke 2, but the magnet 8 or the rotor yoke 2 may be formed of an elastic material. A retainer 12 having a protruding shape may be attached. Furthermore, since the magnet 8 is strongly pulled between the upper and lower yokes 2 and 3, the structure of the elastic member 11 is designed to minimize vertical deformation. For example, in this embodiment, the diameter of the central portion is made slightly smaller to suppress the elongation in the axial direction.

Effects of the Invention As explained above, the present invention fixes the magnet to the rotor yoke via a vibration-damping elastic material, and also provides a spacing retainer that prevents radial vibration between the circumferential surface of the magnet and the rotor yoke. Since the vibration caused by the attraction and repulsion of the magnet can be absorbed by the elastic material, vibration in the radial direction of the magnet can also be prevented, preventing chattering between the magnet and the rotor yoke, and making it possible to attach the magnet to the rotor yoke. By preventing vibrations from being transmitted to the rotor shaft, it is possible to provide a brushless motor with less uneven rotation, which has great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional brushless motor, Figs. 2 and 3 show an embodiment of the present invention, Fig. 2 is a sectional view, Fig. 3 is a cross-sectional view of the rotor section, and Fig. 4. 5 shows different embodiments, FIG. 4 is a longitudinal sectional view of the rotor section, and FIG. 5 is a transverse sectional view of the rotor section. 1...Rotor shaft, 2...Rotor yoke,
3... Stator yoke, 4... Bearing support part, 5,
6, 7... Bearing, 8... Magnet, 9... Armature coil, 10... Rotor, 11... Elastic material, 1
2...Retainer.

Claims (1)

[Claims for Utility Model Registration] Consisting of a stator provided with a multiphase armature coil, and a rotor that faces the stator with an axial gap in between, the rotor is arranged facing the stator and has NS poles. magnets are alternately magnetized, and a dish-shaped rotor yoke to which the magnets are fixed, a rotor shaft is attached, and has an opposing portion facing the circumferential surface of the magnets, and the magnets are connected to each other through an elastic material. A brushless motor characterized in that a spacing retainer made of a non-magnetic material is fixed to the bottom surface of the rotor yoke and is arranged between the circumferential surface of the magnet and the rotor yoke.