JPH0865946A - Rotary electric machine - Google Patents

Abstract

PURPOSE: To realize the simple and effective reduction sin vibration and noise by gradually decreasing the thickness of the inner peripheral wall of a housing from the large inner diameter part of one end to the other end. CONSTITUTION: When a stator core 3a is shrink-fit within a housing 1 to be mounted, the shrink-fit allowances of the housing 1 and the core 3 are gradually increased from the large inner diameter part side to the small inner diameter part side. In this case, the atmospheric pressure of the core 3a received by the housing 1 is operated as reaction to the housing 1 as it is, and the thickness of the housing 1 is gradually decreased from the large inner diameter part side of one end to the small inner diameter part side of the other end, and hence the outer periphery of the housing 1 varied as the thickness is gradually decreased to absorb the axial displacement of the core 3a. As a result, it prevents the air gap size between the stator and the rotor from becoming unequilibrated, and since it can be axially made uniform, the increases in the vibration and noise can be effectively prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary electric machine such as an induction motor, and more particularly to a rotary electric machine suitable for use as a general-purpose induction motor having a relatively small capacity and having an aluminum housing.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the structure of a rotary electric machine composed of a general-purpose induction motor having a relatively small capacity. In the figure, reference numeral 1 denotes a housing, which is formed into a substantially cylindrical shape by casting an iron-based material such as cast iron, and constitutes a casing of the electric motor.
Reference numeral 1a denotes a heat radiating fin, which is radially formed integrally with the outer periphery of the housing 1 so as to have a length along the axial direction. Two
A and 2B are end brackets which are attached to the openings on both sides of the housing 1 by spigot fitting. Reference numeral 3 denotes a stator, which includes a stator core 3a formed by laminating a plurality of silicon steel plates, and a stator coil 3b wound around a plurality of slots formed on the inner peripheral portion of the stator core 3a. It is configured and is fitted and fixed to the inner peripheral portion of the housing 1. Reference numeral 5 is a rotor, and 6 is a rotary shaft to which the rotor 5 is attached. The rotor 5 is mounted on the outer peripheral portion of the rotary shaft 6 at a position facing the stator 2, and has a secondary conductor bar (not shown) and end rings 7 on both end surfaces thereof. It has an internal cooling fan (hereinafter referred to as an internal fan) 8 formed. The rotary shaft 6 is rotatably held by the end brackets 2A and 2B via bearings 4A and 4B. Further, one end (right side in the figure) of the rotary shaft 6 is inserted through the end bracket 2B and protrudes to the outside to form an output shaft, and the other end (left side in the figure) is inserted through the end bracket 2A for external cooling. Fan 9
(Hereinafter referred to as an external fan). An end cover 10 covers the outer fan 9, and has an opening 10a for taking in outside air on one side surface thereof. Further, the other end of the end cover 10 opposite to the opening 10a is formed into an open cylindrical shape, and the end cover 10 is attached to the end bracket 2.
When assembled to A, a radial gap 10b is formed between the end bracket 2A and the outer diameter portion of the housing 1.

In this rotary electric machine, a stator 3 is fitted and fixed to an inner peripheral wall of a housing 1 in advance, and then a rotor 5 having a rotary shaft 6 is inserted into the stator 3 and rotated. The shaft 6 has bearings 4A, 4 in the end brackets 4A, 4B.
The end brackets 4A and 4B are fitted on both ends of the housing 1 so that B can be fitted, and the end brackets 4A and 4B are attached thereto by a plurality of bolts (not shown). When the outer fan 9 is rotated by driving the rotating shaft 6, the outer force is sucked from the opening 10a of the end cover 10 as indicated by the arrow A, and the sucked air is absorbed by the gap 10
It is blown out from b to the outside on the other end side of the end cover 10,
A cooling action is obtained by ventilating the surfaces of the end bracket 2A, the housing 1, and the end bracket 2B. On the other hand, inside the rotating electric machine,
When the rotor 5 rotates, the inner fan 8 rotates accordingly to generate the circulation of the internal air. The generated circulation air is generated by the rotor 5, the end ring 7, and the stator coil 3b.
After passing through while cooling the stator core 3a, the stator core 3a is cooled by passing through the inside of the end brackets 2A and 2B whose temperature rise is relatively lower than that of the housing 1. As a known example related to this type, there is JP-A-61-251440.

By the way, today, there is a strong demand for downsizing and weight reduction of rotating electric machines. In such a case, as a material of the housing 1, a lightweight and highly heat conductive aluminum or aluminum alloy material (specific gravity is about 1/3, Young's modulus is about 1/3, non-heat is about 2 times that of steel, It is easily conceivable to use a light metal such as having a thermal conductivity of about 3 times) to improve the cooling by well transmitting the heat generated inside the rotating electric machine to the housing, and to obtain a small size and a light weight. At this time, the housing is manufactured by a die-casting die having high productivity, but it is important to properly remove the housing 1 from the die-casting die. In the prior art, in order to easily remove the die casting mold from the inside of the housing 1, the inner diameter portion of the housing 1 is provided with a draft, so that the inner diameter of the housing 1 has a large diameter portion on one end side in the axial direction. At the same time, the other end side has a small diameter portion, and has a shape that gradually decreases from one end side to the other end side.

[0005]

However, in the above-mentioned prior art, no consideration is given to the problem that occurs when the stator 3 is attached to the inner peripheral wall of the housing 1. That is, the stator 3 has a uniform outer diameter as shown in FIG. 6, and when it is attached to the housing 1 by shrink fitting, the stator 3
Axial displacement occurs on the inner circumference of. This is because the outer diameter of the stator 3 is mounted by interference fitting slightly larger than the inner diameter of the housing 1, but the inner diameter of the housing 1 is from the large inner diameter portion 1b at one end to the small inner diameter at the other end as described above. Since it gradually becomes smaller as it reaches the portion 1c, when the tightening margins of the stator 3 and the housing 1 are observed in the axial direction, the vicinity of the large inner diameter portion 1b of the housing 1 is looser than the vicinity of the small inner diameter portion 1c. Become. The difference in the tightening margin between the two 1b and 1c is the difference in the external pressure of the stator 3. As a result, when examining the displacement that occurs on the inner circumference of the stator in the axial direction, it goes without saying that the part with a loose interference has a small displacement, the part with a tight interference has a large displacement, and the smaller one has the larger displacement. Will gradually change. Therefore, the rotor 5 is
Since the stator 3 has the same uniform outer diameter, the dimension between the stator 3 and the air gap, that is, the air gap, is unbalanced in the axial direction. For example, in a general-purpose induction motor with an output of about 3.7 KW-4P, as a result of analysis using the finite element method, the displacement of the inner diameter portion of the stator 3 goes from one end to the other as shown in FIG. Axial increase, up to about 20
There is also μmm. This value is large enough to correspond to 7% of the air gap. Thus, when the air gap between the stator 3 and the rotor 5 is unbalanced in the axial direction, there arises a problem that vibration and noise increase when the rotating electric machine is driven. 5 is displaced so as to be sucked, and the rotating shaft 6 is displaced to act as a load on the bearings 4A and 4B, so that there is a problem that the life of the bearing is shortened.

An object of the present invention is to provide a rotating electric machine that can easily and reliably realize low vibration and low noise in view of the above problems of the prior art.

[0007]

According to the present invention, the inner peripheral wall is formed by die casting, and one end in the axial direction of the inner peripheral wall forms a large inner diameter portion, and the inner diameter dimension is gradually narrowed from one end to the other end. In a rotary electric machine having a housing, the thickness forming the inner peripheral wall of the housing is
It is characterized in that the inner peripheral wall is gradually thinned from the large inner diameter portion at one end to the other end.

[0008]

When the stator is shrink-fitted and mounted in the housing, one end in the axial direction of the inner peripheral wall of the housing forms a large inner diameter portion and the other end forms a small inner diameter portion, and further, from the large inner diameter portion to the small inner diameter portion. Since the diameter is gradually reduced, the tightening margin (shrinkage fitting margin) between the housing and the stator gradually decreases as the inner diameter of the housing gradually decreases, that is, from the large inner diameter side to the small inner diameter side. To increase. At that time, the external pressure of the stator received by the housing acts as a reaction force on the housing as it is, but the wall thickness of the housing is, as described above, from the large inner diameter side at one end to the small inner diameter side at the other end. Since the outer periphery of the housing is displaced as the wall thickness is gradually reduced, the axial displacement of the stator can be absorbed. In this case, if the difference in the thickness of the housing in the axial direction is appropriately selected, it is possible to prevent the air gap dimensions between the stator and the rotor from becoming unbalanced, and to achieve a uniform air gap in the axial direction. Because you can
It is possible to reliably prevent an increase in vibration and noise.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is an overall view of an upper half of an embodiment in which a rotary electric machine according to the present invention is applied to a general-purpose induction motor, FIG. 2 is a front view of a housing, and FIG. 3 is an explanatory view showing a main part of the housing. 4 is an explanatory view showing the relationship between the stacking thickness direction of the stator and the axial displacement of the housing inner diameter. In these drawings, the same reference numerals as those in the prior art shown in FIGS. 5 to 7 are the same or equivalent. Represents something.
As shown in FIG. 1, the rotating electric machine of the embodiment has a housing 1, end brackets 2A and 2B, a stator 3, and a bearing 4A.
4B, rotor 5, rotating shaft 6, outer fan 9, and end cover 10. The housing 1 is formed into a cylindrical shape having an appropriate wall thickness 1d by die-casting aluminum or an aluminum alloy material, and one end of the inner peripheral wall in the axial direction is the large inner diameter portion 1b.
In addition, the other end forms a small inner diameter portion 1c smaller than the large inner diameter portion 1b, and the large inner diameter portion 1b to the small inner diameter portion 1c.
The diameter is gradually narrowed to reach a taper shape, and this taper shape has a draft when the die casting is performed. This point is similar to the conventional technique. And in this embodiment, what is different from the above-mentioned prior art is that
When the stator 3 is attached to the housing 1, the shape of the housing 1 is changed so that the stator 3 cannot be displaced. Specifically, as shown in FIGS. 2 and 3, the wall thickness 1d forming the inner peripheral wall of the housing 1 is
The large inner diameter portion 1b which is one end in the axial direction has the same size as it is, and is gradually thinned from the large inner diameter portion 1b to the small inner diameter portion 1c at the other end. Therefore, thickness 1
The outer peripheral surface of d is from the large inner diameter portion 1b at one end to the small inner diameter portion 1 at the other end.
It is getting thinner toward c.

When the stator core 3a is shrink-fitted and mounted in the housing 1 formed as described above, one end in the axial direction of the housing inner peripheral wall forms the large inner diameter portion 1b and the other end forms the small inner diameter portion 1c. Moreover, since the diameter is gradually reduced from the large inner diameter portion 1b to the small inner diameter portion 1c, the tightening margin (shrinkage fitting margin) 1e between the housing 1 and the stator core 3a.
As shown in FIG. 3, as the inner diameter of the housing 1 gradually decreases, that is, gradually increases from the large inner diameter portion 1b side to the small inner diameter portion 1c side. At this time, the external pressure of the stator core 3a received by the housing 1 acts as a reaction force on the housing 1 as it is, but the wall thickness 1d of the housing 1 is the large inner diameter portion 1 at one end as described above.
Since it is formed in a shape that gradually becomes thinner from the side b to the side of the small inner diameter portion 1c which is the other end, the outer periphery of the housing 1 is displaced as the wall thickness 1d is gradually reduced, and as shown in FIG. As shown, the axial displacement of the stator core 3a can be absorbed. In this case, if the difference in the thickness of the housing wall thickness 1d in the axial direction is appropriately selected, it is possible to prevent the air gap dimension between the stator core 3a and the rotor 5 from becoming unbalanced, and to make the axial direction uniform. Since it is possible to form a large air gap, it is possible to reliably prevent an increase in vibration and noise. In addition, the stress in the fitting portion between the housing 1 and the stator 3 becomes constant, and the strength of the housing can be stabilized, so that it is possible to limit design. Further, in the illustrated embodiment, as shown in FIG.
By arranging the small inner diameter portion 1c side of d on the end bracket 2A side and forming the housing wall thickness 1d as described above, one end side of the heat radiation fin 1a communicating with the gap portion 10b of the end cover 10 is on the end bracket 2B side. Is longer in the radial direction than the other end. Therefore, the amount of air flowing into the radiation fin 1b from the gap 10b can be increased by that much, and the outer periphery of the housing wall thickness 1d is at one end (on the side of the small inner diameter portion 1c).
From the other end (on the side of the large inner diameter portion 1b), the air flows along the entire outer circumference of the housing in the axial direction, and the cooling effect of the housing becomes good.

[0011]

As described above, according to the present invention, the thickness of the housing is formed so as to gradually decrease from the large inner diameter portion side which is one end to the small inner diameter portion side which is the other end, Since the axial displacement of the stator can be absorbed as the wall thickness gradually decreases, it is possible to prevent the air gap between the stator and the rotor from becoming unbalanced. As a result of making a uniform air gap in all directions, it is possible to reliably prevent vibration and noise from increasing, and because the limit design can be made by stabilizing the housing strength, it is possible to reduce the manufacturing cost and further to mold the housing by die casting. Not only is the precision of the parts good, manufacturing is easy, but the bearing life can be extended.

[Brief description of drawings]

FIG. 1 is an overall partially broken view showing an embodiment in which a rotating electric machine according to the present invention is applied to a general-purpose induction motor.

FIG. 2 is a partially cutaway front view showing a housing.

FIG. 3 is an enlarged explanatory view showing a main part of a housing.

FIG. 4 is an explanatory diagram showing a relationship between a stacking thickness direction of a stator and an axial displacement of a housing inner diameter.

FIG. 5 is an overall partially broken view showing a general-purpose general-purpose induction motor.

FIG. 6 is an enlarged explanatory view showing a relationship between a housing and a stator according to a conventional technique.

7 is an explanatory view showing a relationship between a stacking thickness direction of the stator shown in FIG. 6 and an axial direction of a housing inner diameter.

[Explanation of symbols]

1 ... housing, 1b ... large inner diameter portion of the inner peripheral wall of the housing,
1c ... a small inner diameter portion of the inner peripheral wall of the housing, 1d ... wall thickness of the housing, 3 ... stator.

Claims (1)

[Claims] 1. A rotary electric machine having a housing formed by die casting, wherein one end in the axial direction of the inner peripheral wall forms a large inner diameter portion, and the inner diameter dimension is gradually narrowed from one end to the other end, A rotary electric machine, wherein the thickness of the inner peripheral wall of the housing is gradually reduced from the large inner diameter portion at one end of the inner peripheral wall to the other end.