JPS61180539A - Rotary electric machine - Google Patents

Abstract

PURPOSE:To reduce a vibration and a noise by forming grooves or holes at the position where the diameter of a stator is large. CONSTITUTION:A stator core 4 is composed by laminating punched core plates 9 formed by punching strip electromagnetic steel plates 8. The both lateral sides and both continuously punching sides of the outer periphery of punched core plates 9 are flatly cut at punching time to be reduced smaller than the radial size of the flat surfaces 9 to form cutouts 9c on arcuate surfaces 9b. The cutouts 9c formed on the plates 9 are formed as grooves 10 disposed on the stationary surface 4a having large radial size, and a rod member 11 having high magnetic permeability is disposed in the groove 10. The surface 4a formed by the surfaces 9b of the outer periphery of the core 4 is engaged fixedly in contact with the inner periphery of a frame.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rotating electrical machine that aims to reduce vibration and noise when the natural frequency of a stator core resonates with electromagnetic force waves.

[Technical Background of the Invention] In recent years, speed control of various types of equipment using AC motors as drive sources has been increasingly performed using inverters. However, in speed control using an inverter, voltage and current waveforms are distorted, magnetic flux harmonics are generated in the stator and rotor, and the electromagnetic force generates vibrations and noise. In this case, it is known from analysis of vibration and noise that the main cause of the high value is a mechanical resonance phenomenon in which the forced external force due to electromagnetic force and the natural frequency of each part of the motor match. On the other hand, an electric motor can be roughly divided into individual components: frame and stator.

There is a rotor, a bearing bracket, and a bearing. Among these, the stator is directly subjected to forced external force, which has a large effect on the overall imaging and noise.Also, the electromagnetic forced external force includes electromagnetic force due to fundamental wave magnetic flux and electromagnetic force due to high frequency magnetic flux, and has many frequencies. There are characteristics that occur.

From the above, in order to reduce vibration and noise, it is sufficient to create a structure in which the frequency of the electromagnetic forced external force does not match the natural frequency of the stator, and in a motor with a fixed frequency, the natural frequency of the stator core is made to deviate from the frequency of electromagnetic force waves to prevent resonance.

However, in this case, it is difficult to avoid resonance in the natural frequency of the stator because there are multiple frequency ranges of electromagnetic forced external force, and in the case of an inverter, the frequency changes.

[Object of the Invention] An object of the present invention is to provide a rotating electrical machine that can perform imaging and reduce noise.

[Summary of the Invention] The present invention provides a stator in which a plurality of portions of the outer periphery of the stator are cut out to provide portions with a smaller diameter than other portions, and grooves or holes are formed in the portions of the stator with a larger diameter. It is characterized by the formation of

[Embodiment of the Invention] An embodiment in which the present invention is applied to an electric motor will be described below with reference to FIGS. 1 to 6.

First, in FIG. 2, 1 is a cylindrical frame, and bearing brackets 2 and 3 are attached to both sides of the frame.

4 is a stator core fixed within the frame 1, 5 is a rotor core, and a rotating shaft 6 of the rotor core 5 is supported by a bearing bracket 2.3 via a bearing 7. As shown in FIG. 4, the stator core 4 is constructed by laminating core punched plates 9 formed by punching out a band-shaped electromagnetic steel sheet 8. During punching, the number of punched pieces is determined in consideration of material cost. In order to obtain a large amount of material and to make the width of the electromagnetic steel sheet 8 small, both sides of the electromagnetic steel sheet 8 in the width direction and both sides of the continuous punching direction are cut flat out of the outer peripheral part of the core punched 9, and the diameter at this flat surface 9a is cut out flatly. The dimension is made smaller than the diameter of the remaining circular arc surface 9b, and a notch 9C is formed in the circular arc surface 9b. When the stator core 4 shown in FIG. 1 is constructed by stacking such core punches 9, the surface formed by the circular arc surface 9b of the outer peripheral surface of the stator core 4 is attached to the frame as shown in FIG. 1, and a surface formed by the flat surfaces 9a and located between the fixed surfaces 4a is a non-contact surface 4b that does not come into contact with the frame 1. In this stator core 4, the notch 9C formed in the core punched plate 9 has a large diameter fixing surface 4a.
As shown in FIG. 3, a rod-shaped member 11 made of, for example, iron powder having high magnetic permeability is disposed in the groove 10.

Next, the operation of the above structure will be explained while comparing it with that of the conventional structure.

That is, FIG. 8 shows a stator core of a conventional electric motor, and the conventional stator core 21 is not provided with the grooves 10 of this embodiment. In such a conventional stator core 21,
When we examine the natural frequencies in the radial direction, they exist in six locations as shown in Figure 9. Of these, the natural frequencies A1 and A2, Bt
and 82, Ct and C2 appear close to each other. The 10th study further investigated the vibration mode of its natural frequency.
In the figures, FIG. 10(a) shows modes with natural frequencies A1 and A2, and an elliptic mode with two degrees of freedom. FIG. 10(b) shows a mode with a natural frequency of 81 and B2, and a triangular mode with three degrees of freedom. Figure 10 (C) shows the natural frequencies C1 and C.
2 mode indicates a rectangular mode with 4 degrees of freedom. And FIG. 10(a).

The two vibration modes m11 and mu2 shown in (b) and (C). m2, and m22, m3, and m,
2 have a phase angle of α with respect to each other. The reason why the natural frequencies appear close to each other in three locations is that in the stator core 21 shown in FIG. This is because they are different. For this reason, two natural frequencies exist in close proximity, and this means that there are many natural frequencies, which means that resonance is easy, and it is important to reduce vibration and noise. This is inconvenient.

On the other hand, when examining the natural frequencies of the stator core 4 of this embodiment, as shown in FIG. the law of nature,
Only E and F appear. This means that the grooves 10 are formed on the fixed surface 4a, which has a larger diameter and higher rigidity than the non-contact surface 4b, which is formed by cutting off the outer periphery of the stator core 4.
It is thought that this is because, as a result of providing this, the rigidity of the part becomes low, and the rigidity centered on the line AA shown in FIG. 1 and the rigidity centered on the line BB shown in FIG. 1 become equivalent.

Therefore, according to this embodiment, the number of locations where the natural frequency exists is halved, making it difficult for resonance to occur and reducing vibration and noise. In this case, especially if a rod-like member 11 with high magnetic permeability is disposed in the groove 10 as in this embodiment, a vibration damping force acts due to the magnetism of this rod-like member 11, thereby reducing the movement of the stator core 4. be able to.

Incidentally, Fig. 6 shows the results of a comparative experiment on noise values when the speed of an electric motor is controlled by an inverter. As is clear from FIG. 6, the noise level of the present invention is lower and the degree of undulation is smaller, so it is understood that it is not so noisy to human ears.

FIG. 7 shows another embodiment of the present invention, which differs from the previous embodiment in that holes 12 are provided in the fixing surface 4a of the stator core 4. In this way, since the rigidity of the fixing surface 48 can be reduced by using the holes 12 instead of the grooves 10, it is possible to obtain the same effect as in the previous embodiment.

Note that the number of removed portions (non-contact surface 4b in the above embodiment) of the outer circumferential portion of the stator core is not limited to four, but may be provided at three or more than four.

[Effects of the Invention] As described above, the present invention can provide a rotating electric machine in which the natural frequency and therefore the number of common photographic points are reduced, and vibration and noise can be reduced.

[Brief explanation of drawings]

1 to 6 show one embodiment of the present invention, in which FIG. 1 is a perspective view of the stator core, FIG. 2 is a sectional view of the electric motor,
Fig. 3 is a cross-sectional view taken along line m-m in Fig. 2, Fig. 4 is a punched configuration diagram of an iron core tone plate, Fig. 5 is a vibration characteristic diagram, Fig. 6 is a noise characteristic diagram, and Fig. 7 is a diagram of noise characteristics. 1 is a diagram corresponding to another embodiment of the present invention, FIG. 8 is a perspective view of a conventional stator core, FIG. 9 is a photographic characteristic diagram of the same, and FIG. 10 (a>, (b) and ( C) is the same vibration mode diagram. In the figure, 1 is a frame, 4 is a stator core, 5 is a rotor core, 9 is an iron core, 10 is a groove, 11 is a rod-shaped member with high magnetic permeability, and 12 is a It is a hole. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 6 Fig. yL @ Shudehige ＾ 7 Fig. 8 Fig.

Claims (1)

[Claims] 1. In a stator core in which a plurality of portions of the outer periphery of the stator core are cut out to provide portions with a smaller diameter than other portions, grooves or A rotating electrical machine characterized by having holes formed therein. 2. The rotating electric machine according to claim 1, wherein a member with high magnetic permeability is disposed in the groove or hole of the stator core.