JPH0775269A - Rotor of permanent magnet motor - Google Patents

Abstract

PURPOSE:To provide a rotor having excellent vibration-proof characteristic for reducing vibration in the rotating direction which is generated on the rotor by rotating magnetic field of a stator of a permanent magnet motor. CONSTITUTION:A rotor having excellent vibration-proof characteristic can be obtained by comprising an external circumference 1 which fixedly couples a permanent magnet 5 to a rotor iron core and an internal circumference 2 coupled to an axis, moreover coupling these two portions with a plurality of coupling members 3 to provide gaps and then inserting viscous and elastic materials 4 into these gaps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-vibration structure for an electric motor, and more particularly to an anti-vibration device for a rotor of an electric motor used in air conditioners, water heaters and the like.

[0002]

2. Description of the Related Art In recent years, permanent magnet motors have been widely used for fan motors because of their good controllability.

A rotor of a conventional permanent magnet motor will be described below with reference to FIG. FIG. 7 shows a DC brushless motor, which is a kind of permanent magnet motor, and is composed of a stator core 11 and a rotor core 8. A permanent magnet 5 is arranged on the outer circumference of the rotor core 8, a shaft 9 is fixed at the center, and a rotor core 11 is rotatably assembled to a stator frame 11 through a bearing 10. Has been.
A fan 12 is fixed to the end of the shaft 9 by a nut 13. Further, the rotor core 8 and the permanent magnet 5 are shown in FIG.
It is configured as shown in.

According to this structure, since the vibration damping property of the rotor core is poor, the vibration in the rotation direction generated in the rotor by the rotating magnetic field of the stator is transmitted to the fan 12 via the shaft 9, and the fan 12 vibrates. And caused an unpleasant sound.

As a countermeasure against this unpleasant sound, an elastic body 41 is inserted between the outer peripheral portion 1 for fixing the permanent magnet 5 and the central portion 2 for fastening the shaft as shown in FIG. To prevent the transmission of vibrations to the motor to reduce the noise generated by the electric motor, and as shown in FIG. 10, a gap 6 is formed between the outer peripheral portion 1 to which the permanent magnet 5 is fixed and the central portion 2 to which the shaft is fastened.
And a method of connecting the outer peripheral portion 1 and the central portion 2 with a plurality of fastening members 3 to prevent vibration transmission in the same manner as described above and reduce the sound generated by the electric motor.

[0006]

However, the conventional method as shown in FIG. 9 has problems such as heat resistance of the elastic body, dimensional accuracy, and difficulty in setting the spring constant. Therefore, the conventional method as shown in FIG. However, when the vibration frequency of the electric motor matches the natural frequency of the rotor in the direction of rotation, the rotor resonates and a large vibration is generated.

On the other hand, as a method for reducing the generated sound, skew magnetization may be performed electrically. However, in that case, the efficiency and the output are reduced due to the loss of the magnetic flux, which is not preferable.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a rotor of an electric motor in which vibration is further reduced as compared with the prior art.

[0009]

In order to achieve this object, a rotor of a permanent magnet electric motor of the present invention has a permanent magnet fixed to an outer peripheral portion, a shaft is fastened to the central portion, and the outer peripheral portion and the central portion are connected. A plurality of fastening members are connected to each other to form a void, and a viscoelastic body is inserted into the void.

[0010]

In general, the vibration in the rotational direction generated in the rotor by the rotating magnetic field of the stator resonates when the frequency of the vibration matches the natural frequency of the rotor to generate the maximum amplitude. According to the above configuration of the present invention, this maximum amplitude can be greatly reduced by the damping action due to the internal friction of the viscoelastic body that is in contact with the fastening material, and it becomes difficult to transmit the vibration in the rotational direction to the shaft. .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The same numbers are used for the same components as those described in the conventional example.

As shown in the figure, the rotor core is a permanent magnet 5
Has an outer peripheral portion 1 for fixing and coupling with each other, and a central portion 2 for fastening the rotor core around the shaft. The outer peripheral portion 1 and the central portion 2 are connected by a fastening material 3, and the viscoelastic body 4 is inserted into the space between them. Is configured. Further, the rotor core is formed by laminating a plurality of iron plates in which the outer peripheral portion 1, the central portion 2 and the fastening material 3 are integrally formed.

The operation of the rotor of the permanent magnet motor constructed as described above will be described with reference to FIG. FIG. 2A is an enlarged view of the portion of the fastening material 3, and FIG.
[Fig. 4] is a perspective view for explaining the action of the fastening member 3. The rigidity of the fastening member 3 can be selected according to the width W and the length L.

[0014] The fastening member rigid with second moment I = bW ^3/12 according to the shape shown in FIG. 2 (b), is determined by the Young's modulus E of the material. Therefore, the stiffness K'is generally expressed as K '= EI. Finally, the spring constant K of the equation (1) is obtained by considering the length L of the fastening material 3 in K ', and the natural frequency is determined by appropriately selecting K.

Natural frequency = (K (J ₁ + J ₂ ) / J ₁ J ₂ )
^0.5 / 2π (Hz) (1) J ₁ : Inertia of the rotor J ₂ : Inertia considering the shaft and fan K: In this case, connect the outer peripheral part and the central part of the rotor core with multiple fasteners. The torsional spring constant of the rotor in the direction of rotation resonates when the natural frequency of the rotor and the frequency of the vibration in the direction of rotation generated by the rotating magnetic field of the stator coincide with each other. The amplitude at the time of resonance is generally expressed as shown in FIG. It can be seen from FIG. 3 that the amplitude magnification with respect to the vibration ratio f / f ₀ decreases as the damping ratio ζ increases. In FIG. 3, f is the frequency of vibration in the rotational direction generated by the rotating magnetic field of the stator in the rotor, f ₀ is the natural frequency of the rotor, and ζ is the degree of energy loss due to viscosity. It is a thing.

From the above, by appropriately selecting the material of the viscoelastic body 4 that is in contact with the fastening material 3, the damping ratio ζ is increased and the maximum amplitude when resonating at the natural frequency is reduced. be able to.

4 and 5 show another embodiment in which the shape of the viscoelastic body 4 in contact with the fastening material 3 is changed to leave a void 6 in a part thereof. FIG. The viscoelastic body 4 is installed only around the material 3, and the viscoelastic body 4 is installed between the respective fastening materials 3 in FIG. Further, FIG. 6 shows an embodiment of the rotor for an induction motor in which the void is filled with the viscoelastic body 4 and the secondary conductor 14 is penetrated in the outer peripheral portion.

Further, in the rotor core as shown in FIG. 1 in which the rotor core is formed by laminating iron plates, the iron plates are shifted one by one or several by one in the rotational direction. There are other laminated examples, and in that case as well, the same effect can be obtained by inserting the viscoelastic body into the void.

[0019]

As is apparent from the above description of the embodiments of the present invention, a permanent magnet is fixedly coupled to the outer peripheral portion of the rotor iron core and is coupled to the shaft at the central portion, and the space between the outer peripheral portion and the central portion is provided. Vibration can be effectively reduced by connecting a plurality of fasteners to provide a void, inserting a viscoelastic body into the void, and selecting the shape of the fastener and the viscosity of the viscoelastic body appropriately. Also,
It is possible to provide a rotor of a permanent magnet electric motor, which is capable of achieving high efficiency and high output without loss of magnetic flux due to skew magnetization, and which is excellent in vibration isolation.

[Brief description of drawings]

FIG. 1A is a plan view of a rotor of a permanent magnet motor according to an embodiment of the present invention. FIG. 1B is a sectional view taken along the line AA ′ in FIG.

FIG. 2A is an enlarged cross-sectional view of a rotor of a permanent magnet motor according to an embodiment of the present invention. FIG. 2B is a perspective view of a fastening material portion 3.

FIG. 3 is a characteristic diagram showing an amplitude magnification with respect to a vibration ratio f / f ₀ .

FIG. 4 is a sectional view of a rotor according to another embodiment of the present invention.

FIG. 5 is a sectional view of a rotor according to another embodiment of the present invention.

FIG. 6 is a sectional view of a rotor according to still another embodiment of the present invention.

FIG. 7 is a sectional view of a conventional permanent magnet electric motor with a fan.

FIG. 8A is a plan view of a rotor of a conventional permanent magnet motor, and FIG. 8B is a sectional view of the same.

FIG. 9 (a) is a plan view of a conventional rotor provided with vibration damping means, and FIG. 9 (b) is a sectional view of the same.

FIG. 10 (a) is a plan view of a rotor provided with another conventional vibration isolator (b) is a sectional view thereof

[Explanation of symbols]

 1 Outer peripheral part 2 Center part 3 Fastening material 4 Viscoelastic body 5 Permanent magnet 6 Void

Claims (1)

[Claims] 1. A permanent magnet is fixed to the outer peripheral portion, a shaft is fastened to the central portion, a plurality of fastening members are connected between the outer peripheral portion and the central portion to form a void, and a viscoelastic body is provided in the void. The rotor of the permanent magnet motor that is obtained by inserting.