JPH0332348A - Brushless motor - Google Patents

Abstract

PURPOSE:To reduce noise of rotor by arranging each pole of a permanent magnet to be secured to a rotor body such that the border thereof in the rotary direction inclines from one axial direction toward the other axial direction. CONSTITUTION:In a permanent magnet 23, opposite end sides 23a, 23b in the rotary direction are arranged in parallel each other and inclining against the axis of a rotor shaft 4. A magnetism detecting element 11 detects magnetism and supplies exciting current to a specific coil. At this time, a portion of N or S pole is facing with that pole and the N or S pole faces entirely with that pole as the rotation proceeds. Consequently, the magnetic force functioning between the permanent magnet 23 of rotor 21 and the pole 6 of stator 5, when the rotor rotates, has an approximately sinusoidal waveform. By such arrangement, deformation or vibration of the rotor body is suppressed and noise can be reduced. Each pole of the permanent magnet has the border in the rotary direction inclining from one axial direction toward the other axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brushless motor in which the rotor is of an external rotor type.

[Prior art] A brushless motor in which the rotor poles are detected by a magnetic detection element to set the timing of energizing each coil, and the rotor is of an external rotor type generally has a configuration as shown in Figure 5. It is.

That is, in the rotor 1, permanent magnets 3 having alternately different polarities are arranged on the inner circumferential surface of a rotor main body 2 having a cylindrical shape with a bottom, and a rotor shaft 4 is fixed to the center of the bottom.

In this case, the permanent magnet 3 is often segmented for each pole when it is desired to increase its magnetic force. The stator 5 has a plurality of magnetic poles 6, 6 . . . facing the permanent magnets 3 of the rotor. - and each magnetic pole has a coil 7.7. −
It is wrapped in Magnetic sensing elements (not shown) are arranged opposite to the permanent magnets 3 of the rotor, and detect the poles of the permanent magnets 3 for each of the coils 7, 7, . - Set the energization timing of the excitation current to -.

The permanent magnets 3 of the rotor 1 are as shown in FIG.
Boundary between adjacent poles, that is, both end sides 3a, 3 in the rotation direction
b is parallel to the axis of the rotor, and the expanded shape is a rectangle. In this example, the permanent magnet is segmented for each pole, but the same is true for cylindrical magnets as well.

[Problem that the invention attempts to solve]

In such a brushless motor, the rotor 1 rotates each time a magnetically attractive force or repulsive force acts between the permanent magnets 3 of the rotor and the magnetic poles 6 of the stator.
During rotation, the rotating main body 2 undergoes radial deformation and vibrates. This deformation and vibration also generates corresponding noise.

The present invention has been made in view of the above circumstances, and its purpose is to provide a brushless motor that can suppress deformation and vibration of the rotor body and reduce noise.

[Means to solve the problem]

In order to solve this problem, the brushless motor of the present invention has a configuration in which the boundaries in the rotation direction of the various types of permanent magnets fixed to the rotor body of the rotor are inclined from one side of the IJ to the other side in the axial direction. It's Nishide.

[Operation] According to the present invention, the magnetic force (magnetic attractive force and repulsive force) that acts between the permanent magnets of the rotor and the magnetic poles of the stator as the rotor rotates has a smooth temporal change. It has a shape close to a sine wave, and noise can be reduced compared to conventional ones.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 4. Incidentally, since the main part of the present invention lies in the structure of the rotor, especially its permanent magnets, other members are given the same symbols as in the section [Prior art i1:i).

The rotation 7-21 has a cylindrical shape with a bottom and is provided with a plurality of (four in this embodiment) permanent magnets 23, 23 . - is arranged, and the rotor shaft 4 is fixed via the bottom central G chamber tea. Each permanent magnet 23.23. For example, it has an arcuate plate shape, and has two types of magnetization in the radial direction: north pole, south pole, and south pole north pole.
The polarity appearing on its surface is alternate.

As shown in FIG. 3, this permanent magnet 23 has both end sides 23a and 23b in the rotation direction that are parallel to each other and are inclined with respect to the axis of the rotor shaft 4.

That is, in the unfolded state, it forms a parallelogram in which the upper and lower sides 23c and 23d are perpendicular to the axis of the rotor shaft 4. Therefore, the end side 23a and the lower side 2 of the lower part in FIG.
The angle θ with respect to 3d is an acute angle. In other words, as for the permanent magnets as a whole, the boundary in the rotation direction of each type is inclined from one direction (L direction or downward direction) to the other direction (downward or upward direction) in the axial direction. As shown in FIG. 4, each permanent magnet 23, 23. - are arranged so that they are alternately different poles. 7 is the axis of the rotor shaft 4.

The stator 5 has a laminated iron core formed by stamping a magnetic material such as a silicon steel plate, and this iron core has a plurality of (six in this embodiment) magnetic poles 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 10, 10, 10, 12, 12, 12, 12, 12, 2 2 3. that ones, 6 and 6 magnetic poles 6, 6, 6 . - are provided protruding from the cylindrical base, and coils 7.7. -It is wrapped in one.

The rotor 21 and stator 5 are assembled with the bearing stand 8 interposed. The bearing stand 8b has a cylindrical portion 8a having a cylindrical shape with a bottom.
The bearing 9 is press-fitted into the inner periphery of the cylindrical portion 8a, and the stator 5 is press-fitted onto the outer periphery of the cylindrical portion 8a.
It is fitted and installed.

Then, the rotor 21 pushes the rotor shaft 4 through the bearing 9, and the C
Can be assembled by controlling the amount of backlash. This bearing stand 8 has a flange-like mounting portion 8b connected to the lower opening of the cylindrical portion 8a.

In addition, the connection board 1 is installed at the same place in the lower center of part 8b.
0 is attached. The magnetic sensing element-11 is connected to the wiring board 1
0 and is fixed, and its detection portion is attached to face the inner circumferential surface of the permanent magnet 23 by passing through the portion 8b. Then, the pole (N pole or S pole) of the permanent magnet 23 is detected to set the timing of supplying the excitation current to each of the 21 coils 77, -.

In such a brushless motor, the magnetic sensing element 11
detects the pole and predetermined:X! When an excitation current is applied, the permanent magnet 23 facing the magnetic pole is a part of the north pole or south pole, and as the rotation progresses, the entire north pole or south pole faces. Therefore, as the rotor rotates, the magnetic force (magnetic attractive force and repulsive force) that acts between the permanent magnet 23 of the rotor 21 and the magnetic pole 6 of the stator 5 has a smooth sinusoidal change over time. It will be close to.

In view of this, in conventional devices, the entire N or S pole is always opposed to the magnetic pole, so there is an effect between the permanent magnet 23 of the rotor 21 and the magnetic pole 6 of the fixed 1r-5. The magnetic force (
The temporal change of the magnetic attraction force and repulsion force is similar to a rectangular wave.

(Effects of the Invention) Since the brushless motor of the present invention is configured as described above, the magnetic force (magnetic attraction force and repulsive force)
In this case, the temporal change becomes smooth and almost like a sine wave, and deformation and vibration of the rotor body can be suppressed compared to the conventional rotor, thereby reducing noise.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing one embodiment of the present invention, Fig. 2 is a cross-sectional view thereof, Fig. 3 is a perspective view of the permanent magnet, and Fig. 4 is an arrangement of the permanent magnet. The explanatory diagram, FIG. 5, is a longitudinal sectional view showing a conventional example, and FIG. 6 is an explanatory diagram of the arrangement of permanent magnets. 21-rotor, 2-rotor main body, 23-permanent magnet, 4-rotor shaft, 5-stator, 6 magnetic pole, 7-': 1-il, 8-bearing stand, 11-magnetic sensing element.

Claims (1)

[Claims] (1) A rotor with permanent magnets of different polarities fixed to the inner circumferential surface of the rotor body, which has a cylindrical shape with a bottom, and a plurality of magnetic poles facing the permanent magnets of the rotor, with each magnetic pole being individually excited. A stator is equipped with a stator wound with a coil that is wound with a magnet, and a magnetic detection element that is disposed opposite to the permanent magnet of the rotor and that detects the pole of the permanent magnet and sets the timing of energizing the excitation current to each coil. A brushless motor characterized in that each pole of the permanent magnet of the rotor has a boundary in its rotation direction that is inclined from one side to the other in the axial direction.