JPH07298582A - induction motor - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a compact induction motor with high performance and low noise. [Structure] In an induction motor, wherein a slot of a rotor core has a bridge portion that closes the end of the slot on the side facing the stator core, the bridge portion has a gap that connects the inside and the outside of the slot between the laminated electromagnetic steel sheets. Is provided. [Effect] Gas is released during die casting from the gap that connects the inside and the outside of the slot provided between the laminated layers,
A uniform secondary conductor with no nest is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor, and more particularly to a small induction motor which can be operated with less noise even if phase control is performed.

[0002]

2. Description of the Related Art Small induction motors have a simple structure and high reliability, and are widely used as a drive source for consumer equipment. However, there is a strong market need for higher performance and lower noise. For example, fan motors used in air conditioners and the like are required to have particularly low noise. In the case where the speed control is performed by the phase control, the noise is large, and thus the demand for noise reduction is particularly strong.

Generally, the shape of the slot provided in the rotor of a small induction motor includes a semi-open slot shape and an enclosed slot shape as shown in FIG. In the open slot type, the magnetic flux density in the air gap between the stator and rotor decreases locally at the groove of the rotor slot tip, so not only is noise generated during operation, but the maximum magnetic flux density is high. Therefore, there is a drawback that the efficiency is low.

For this reason, an enclosed slot improved on this point has been used for an air conditioning fan motor or the like. However, in the case of the enclosed slot, there is a large amount of leakage magnetic flux that passes through the bridge portion at the top of the slot without interlinking with the secondary conductor among the magnetic flux incident from the stator core, so it has the drawback of poor motor characteristics. Was. Further, in the case of the enclosed slot, when the secondary conductor is formed by die casting of aluminum or the like, the conductor in each slot becomes non-uniform. Along with this, there were problems such as the generation of humming noise, variations in torque characteristics, and loud noise.

The cause of non-uniformity of the conductor in each slot was investigated. FIG. 6 shows the contents of observation of hot water flow during die casting to the slot portion of the rotor. This figure shows a die-cast product in which the amount of hot water is insufficient in advance, and a cross section of the slot portion along the circumferential direction of the rotor. Some slots are completely filled with aluminum and some slots are filled only at both ends. It is observed that in a slot filled only at both ends, dead air is trapped within the slot. The rotor core is generally provided with 30 to 40 slots, but the number of gates is limited to about 10 at most, so that there are slots close to the gate and slots distant from the gate. There is a huge difference in the flow. At the time of die casting, the hot water is ejected from the gate at an extremely high speed, so the hot water filled in the slots near the gate reaches the end ring on the opposite side of the gate while the slots far from the gate cannot be filled with the hot water. The other slots are also filled from the side opposite to the gate, and air is trapped in the slots. In die casting under normal conditions, a sufficient amount of hot water is die cast,
The air trapped in the slots is compressed and miniaturized by the pressure during die casting.Therefore, it is possible to avoid the difference in the density and resistance between the secondary conductors even in the slots that cannot be seen as air bubbles. I didn't. For this reason, there is a big problem that the generation of noise due to this is unavoidable in an air-conditioning fan motor that performs phase control, in particular, in a case where there is a large variation in characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks of the prior art and to provide a compact induction motor with high performance and low noise.

[0007]

According to the present invention, there is provided a stator core, a rotor core formed by laminating thin electromagnetic steel sheets,
A stator coil provided in the stator core, an enclosed slot formed in the rotor core, and a rotor conductor embedded in the slot by die casting are provided, and the slot end is closed on the side facing the stator core. An induction motor having a bridge portion is characterized in that the bridge portion is provided with a gap for communicating the inside and the outside of the slot between the laminated electromagnetic steel plates.

[0008]

By forming a gap in the bridge portion in the laminated state, the air trapped in the slot is released during die casting, so that a uniform conductor can be formed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical cross-sectional view in which the present invention is applied to a blower motor of an air conditioning fan unit. In the figure, 1 is a small motor, which is an inner rotor type induction motor. Reference numeral 2 denotes a housing, which has a stator core 3 fixed inside by a method such as hot fitting. A primary winding 4 as a stator coil is mounted on the stator core 3. 5 is an end bracket and tightening screw 6
Thus, the housing 2 is fastened and fixed. Reference numeral 7 denotes a rotor, which is a rotor core 8 formed by laminating thin electromagnetic steel plates.
And a rotor secondary conductor 9 and an end ring 10 formed by aluminum die casting. The rotor 7 has a rotating shaft 11 and a ball bearing 12,
13 is rotatably supported. 1 for bearings 12 and 13
4, 15 are supported by a motor mounting base 17 via absorbers 14, 15 and absorber fastening members 16, 16. Reference numeral 18 denotes a base of the fan unit, and the motor mounting base 17 is attached to the base 18 of the fan unit.

The rotary shaft 11 is attached to the fan shaft 20 via a coupling 19. A fan 21 is attached to the fan shaft 20, and a fan casing 22 surrounding the fan 21 is attached to the base 18. FIG. 2 shows the rotor 7 viewed from the axial direction of the rotary shaft 11.

FIG. 3 is a circuit diagram showing the main winding 23 and the auxiliary winding 2
4 shows a circuit of a capacitor run induction motor with 4 and a capacitor 25. The phase of this motor is controlled by the phase control means of the thyristor 26. In the phase control, the waveform of the power source is cut off as shown in FIG. At low speed, only the shaded portion in the figure is energized, so that the voltage of the power supply containing many harmonic components is applied. The phase control including many harmonic components easily causes electromagnetic noise of the motor.

Here, in order to deepen the understanding of the present invention, the problems of the prior art will be described in more detail. FIG. 5 shows a conventional type enclosed slot, in which the rotor core 8 and the slot 27 have a bridge 28 at the tip end facing the stator core. In such a conventional rotor core having the slots 27, gas is left in the slots 27 by laminating thin electromagnetic steel plates and then injecting aluminum for the rotor conductor into the slots 27 by die casting. This will be described with reference to FIG. FIG. 6 corresponds to the VI-VI section of FIG. The molten metal injected at high speed from the casting gate 29 runs so as to spread to the end ring 10, enters the slot 27, and reaches the end ring 10 on the opposite side. Here, the hot water in the slot 27 facing the gate 29 runs fast and returns from the end ring 10 on the opposite side to the inside of the slot 27 not facing the gate 29. This is because there is hot water at the gate 29 to run in the slot 27 that does not face the gate 29.
This is because it will be slower than the one facing. Therefore, the hot water flows from both sides into the slot 27 not facing the gate 29, so that the gas body 30 is trapped as shown in FIG. The gas body 30 causes a problem that a cavity is formed in the rotor conductor in the slot 27.

The gas body 30 contains not only the air in the mold but also a gas or the like which is vaporized by the release agent coming into contact with hot water.

The rotor core 8a shown in FIG.
The bridge 31 is provided at the tip of 7a (the part facing the stator core). The bridge 31 has a thickness in the stacking direction in which thin electromagnetic steel plates are stacked.
It is formed to be thinner than the plate thickness of the electromagnetic steel sheet in the entire width range of the part or in part. FIG. 8 shows a cross section in which the rotor core 8a having such a configuration is set in the mold. The electromagnetic steel plates forming the rotor core 8a are in close contact with each other so that there is no gap on the inner peripheral side of the slot 27a, but there is a gap 32 on the bridge 31 portion on the outer peripheral side.
Is formed. The gap 32 is formed because the bridge 31 is thinner than the electromagnetic steel plate.

Since the gap 32 is formed in this manner, the hot water injected from the gate 29 at a high speed is filled with the slots 2 from both sides of the end ring 10 as described with reference to FIG.
Since the unnecessary gas body 30 escapes from the gap 32 to the outside even when flowing into 7a, it is difficult to form a cavity in the rotor conductor in the slot 27a. For this reason, the rotor conductor of the secondary conductor has a slot 27a.
One has no cavities and the other has cavities less, so that the electromagnetic noise of the motor can be reduced and the variation in the rotation characteristics of the motor can also be reduced.

Slot 27 of rotor core 8b shown in FIG.
In b, the bridge portion 35 is provided at the tip portion,
The portion connected to the base of the bridge portion 35 has a strong structure. That is, although the bridge portion 35 is formed to be extremely thin, the portion connected to the root of the bridge portion 35 has the reinforcement portion 3 having a long depth in the radial direction of the rotor core 8b.
4 are provided.

Since the overall shape of the slot 27b is divergent toward the outer peripheral direction, the centrifugal force of the rotor conductor due to the rotation of the rotor core 8b is applied to the tip portion of the slot 27b. Since this centrifugal force is received by the reinforcing portion 34, it is not applied to the bridge portion 35 formed to be extremely thin. Although the reinforcing portion 34 has a long depth, the extremely thin bridge portion 35 suppresses the leakage magnetic flux to prevent the deterioration of the motor characteristics.

Next, how to make the bridge portion 35 will be described. In the embodiment of FIG. 8 described above, the method of making is not particularly described, but it can be made by pressing and crushing the bridge portion 35. A method of making the bridge portion 35 shown in FIG. 9 will be described in detail with reference to FIGS.

The bridge portion 35 is automatically formed in the punching process of the rotor core. In the punching, first, the slot 27b is formed and then the outer periphery of the rotor core 8b is formed. The punching directions of the slot 27b and the outer periphery of the rotor core 8b are opposite to each other. Rotor core 8
When the outer periphery of b is punched out, a shearing portion 36, a breaking portion 37, and a drooping portion 38 are generated, which causes the bridge portion 3
5 is thinly formed in the stacking direction. The rotor core is manufactured by a progressive die through several drawing steps. The drawing step of the bridge portion will be described in more detail with reference to FIG. As shown in the figure, first, in the step (1), the slot 27b is punched out in the direction of the arrow, and at this time, the drooping portion 38 is formed. Next, in step (2), the outer peripheral portion 39 of the rotor core is punched in the direction of the arrow. At this time, a compressive force is applied to the outer peripheral portion 39 of the rotor core in the opposite direction, but since the bridge portion 35 is thin, this compression is performed. The force will reduce the plate thickness. The bridge portion 35 is formed by the reduction in the plate thickness direction. When laminated as a rotor core, a gap is created by the bridge portion 35.

Although the bridging portion 35 is thinly formed due to the drooping sag, it has been confirmed that the size of the sagging droop does not change much even if the type of the electromagnetic steel sheet is different. Table 1 is a comparative display of the size of the droop when punching by changing the type of electromagnetic steel sheet. The clearance was tested with a mold having a thickness of 5%.

[0022]

[Table 1]

Next, the dimensional relationship of the bridge portion 35 will be described from the viewpoint of electrical characteristics.

In FIG. 12, the size of the bridge portion 35 is set such that the radial thickness T at both ends thereof is 0.1 times the width B or more and 0.25 mm or less. If it is 0.25 mm or more, it is not possible to fully utilize the reduction in plate thickness due to punching sagging during punching. On the other hand, if it is less than 0.1 times, magnetic saturation occurs at the bridge part. The magnetic flux 40 enters through the air gap with the stator core, but the magnetic flux density of the air gap is generally 0.35 to 0.5T (Tesla),
The magnetic flux density Bt at both ends of the bridge is Bt = (0.35-
0.5) × L / 2T. On the other hand, magnetic steel sheet is magnetically saturated when it exceeds 1.7T, so T ≧ (0.35-0.5) / 1.
It is necessary that 7 × L / 2 = (0.1 to 0.15) × L. Therefore, magnetic saturation occurs below 0.1 times.

Further, dimensions related to the bridge portion will be described.

The thickness of the electromagnetic steel sheet c = 0.5 mm, the maximum width of the outer peripheral side of the slot = 2.7 mm, the width B in the front direction of the bridge =
0.6 mm, radial thickness T = 0.13 mm, bridge drop depth d (for clearance) = 0.1 mm, rotary shaft insertion hole diameter = 15
mm. A rotor core using an electromagnetic steel plate punched out in such a size may be included in terms of manufacturing.

A gap having a drop depth d of 0.1 mm is formed between the laminated rotor cores of electromagnetic steel sheets. The gap communicates the inside and outside of the slot 27b and the shaft of the slot 27b. Over the entire length of the direction,
Since the gaps are evenly formed, the gas body 30 is discharged from the gaps in the die casting process. A secondary conductor having less nests and less variation can be obtained in the slots. As a result, the characteristics of the motor are improved and the variation in the quality of the secondary conductor is reduced, so that the noise can be reduced.

FIG. 13 shows the relationship between the radial thickness T of the bridge portion and (efficiency / maximum torque / noise level). This shows the best range based on that of the embodiment shown in FIGS. That is, it can be seen that when the radial thickness T is 0.25 mm or less, the maximum torque and efficiency are high and the noise is low. Further, when the thickness T in the radial direction is 0.05 mm or less, the maximum torque and efficiency are low, and the noise is high. Therefore, it is desirable that the thickness T be 0.06 mm or more. Further, in the embodiment shown in FIG. 7, when the thickness T in the radial direction is 0.25 mm, the characteristics relating to the maximum torque, efficiency and noise are higher than those of the embodiments shown in FIGS. It turns out to be inferior. This is shown in Figure 7.
In the embodiment shown in (1), magnetic saturation is considered to occur at the root of the bridge.

14 and 15 show the results of frequency analysis of noise. FIG. 14 shows a frequency analysis result of noise when driven by a conventional motor, and FIG. 15 shows a frequency analysis result of noise when driven by a motor according to an embodiment of the present invention. It can be seen that the motor according to the embodiment of the present invention has a low noise level as a whole and the peak noise level is significantly low.

Although the mechanism for the gas body 30 to escape is described above with reference to FIG. 8, it will be described from still another viewpoint based on this figure.

When the rotor core is set in the die-casting die and hot water of aluminum is injected at high speed, the gas body 30 escapes from the gap 32, and the hot water also flows into the gap 32, and the gap 32 is filled with the conductor of aluminum. .
On the outer circumference of the rotor core and the inner circumference of the die casting mold 33,
Since there is a gap G of 0.01 mm to 0.03 mm, hot water leaks into this gap G as well. However, since the gap 32 is small as described above, the amount of leakage into the gap G is small, and the head can be seen slightly beyond the gap 32. In the conventional open-slot rotor core, since the tip end side (outer peripheral side) of the slot is large and continuously opened, a large amount of hot water leaks into the gap G and spreads and adheres to the outer periphery of the rotor core. You can burr in the condition that it does. This burr impairs the performance of the motor and must be removed. According to the present invention, since the aluminum conductor allows the head to be slightly seen through the gap 32, the performance of the motor is not affected and deburring as in the conventional example is unnecessary. It is a hassle-free one. Further, in the conventional open slot rotor core, the gap G must be made as small as possible so that the burr is reduced as much as possible. However, if the gap G is reduced, the rotor core and the die-casting die 33 are tightly fitted to each other, so that the rotor core cannot be smoothly taken in and out of the die-casting die 33. In the present invention, since there is no inconvenience of burr generation,
It is not necessary to reduce the gap G, and the die casting mold 3
The rotor core can be smoothly put in and taken out from the No. 3, and the productivity is good. Further, the bridge portion is thin and weak in mechanical strength, but since the aluminum conductor filled in the gap 32 is coupled with the thin bridge portion, the bridge portion is reinforced. When the aluminum conductor can barely look into the gap 32, the connection between the aluminum conductor and the thin bridge portion is further strengthened, so that the bridge portion is further reinforced.

The motor described above has a motor capacity of 1
The example is for 5 to 150 W. 15
The outer diameter of the W rotor core is 20 mm, and the outer diameter of the 150 W rotor core is 60 mm. The present invention can be applied to motors other than this capacity.

[0033]

As described above, according to the present invention, not only the characteristics can be improved without increasing the cost, but also the noise can be reduced. Furthermore, conventionally, when shifting by phase control,
Although the application range was limited due to the large noise, the present invention has a great practical effect such that the application range can be expanded because the noise can be greatly reduced even during the phase control.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a blower motor using a small induction motor according to an embodiment of the present invention in an air conditioning fan unit.

FIG. 2 is a plan view of a rotor core according to an embodiment of the present invention.

FIG. 3 is a connection diagram according to an embodiment of the present invention.

FIG. 4 is a waveform diagram of a power supply according to an embodiment of the present invention.

FIG. 5 is a detailed view of a conventional enclosed slot portion.

FIG. 6 is an explanatory diagram of a molten metal flow during die casting of a rotor core having a conventional enclosed slot portion.

FIG. 7 is a detailed view of a slot portion according to an embodiment of the present invention.

FIG. 8 is an explanatory diagram of die casting of the rotor core according to the embodiment of FIG.

FIG. 9 is a detailed view of slots of a rotor core according to another embodiment of the present invention.

10 is an enlarged view of a bridge portion of the rotor core according to the embodiment of FIG.

11 is an explanatory view showing punching of the rotor core according to the embodiment of FIG. 9. FIG.

FIG. 12 is an explanatory diagram showing the relationship between the dimensions of the bridge portion and the magnetic flux of the rotor core according to the embodiment of FIG.

FIG. 13 is a comparative diagram showing noise, maximum torque, and efficiency of the motor of the embodiment of FIG. 9 and the conventional motor.

FIG. 14 is a frequency analysis diagram in which noise of a conventional motor is analyzed.

FIG. 15 is a frequency analysis diagram in which noise is analyzed in the motor according to the embodiment of the present invention.

[Explanation of symbols]

8 ... Rotor core, 27, 27a, 27b ... Slot, 2
8, 31, 35 ... Bridge, 32 ... Gap, 38 ... Drainage.

Claims (8)

[Claims] 1. A rotor core formed by laminating a stator core, a thin electromagnetic steel plate, a stator coil provided in the stator core, an enclosed slot formed in the rotor core, and a rotor embedded in the slot by die casting. An induction motor having a bridge portion that closes an end of the slot on a side facing the stator core in the slot, the bridge portion includes an inner side and an outer side of the slot between the laminated electromagnetic steel sheets. An induction motor characterized by having a communicating gap. 2. A rotor core formed by laminating a stator core, a thin electromagnetic steel sheet, a stator coil provided on the stator core, an enclosed slot formed in the rotor core, and a rotor embedded in the slot by die casting. In the induction motor, comprising: a conductor for use, and the slot having a bridge portion that closes an end of the slot on a side facing the stator core, the bridge portion has a thickness corresponding to a laminating direction of the electromagnetic steel sheets. An induction motor having a thin portion thinner than the plate thickness. 3. A rotor core formed by laminating a stator core, a thin electromagnetic steel plate, a stator coil provided on the stator core, an enclosed slot formed in the rotor core, and a rotor embedded in the slot by die casting. An induction motor having a bridge portion that closes an end of the slot on a side facing the stator core in the slot, the bridge portion includes an inner side and an outer side of the slot between the laminated electromagnetic steel sheets. An induction motor characterized by being provided with a communicating air gap for air release during die casting. 4. A stator core, a rotor core formed by laminating thin electromagnetic steel plates, a stator coil provided in the stator core, an enclosed slot formed in the rotor core, and an aluminum embedded in the slot by die casting. And a rotor conductor, wherein the slot has a bridge portion that closes the end of the slot on the side facing the stator core, wherein the bridge portion has an inner side of the slot between the laminated magnetic steel sheets. An induction motor characterized by having a gap communicating with the outside. 5. A stator core, a rotor core formed by laminating thin electromagnetic steel sheets, a stator coil provided in the stator core, an enclosed slot formed in the rotor core, and aluminum which is embedded in the slot by die casting. And a rotor conductor, wherein the slot has a bridge portion that closes the end of the slot on the side facing the stator core, wherein the bridge portion has an inner side of the slot between the laminated magnetic steel sheets. An induction motor, characterized in that a gap communicating with the outside is provided, and the gap is filled with aluminum of a rotor conductor embedded in a slot. 6. A rotor core formed by laminating a stator core, a thin electromagnetic steel plate, a stator coil provided in the stator core, an enclosed slot formed in the rotor core, and a rotor embedded in the slot by die casting. In the induction motor, comprising: a conductor for use, and the slot having a bridge portion that closes an end of the slot on a side facing the stator core, the bridge portion has a thickness corresponding to a laminating direction of the electromagnetic steel sheets. An induction motor characterized in that a thin-walled portion thinner than the plate thickness is provided, and the thin-walled portion is formed by punching sag generated when punching an electromagnetic steel sheet. 7. A rotor core formed by laminating a stator core, a thin electromagnetic steel plate, a stator coil provided in the stator core, an enclosed slot formed in the rotor core, and a rotor embedded in the slot by die casting. In the induction motor, comprising: a conductor for use, and the slot having a bridge portion that closes an end of the slot on a side facing the stator core, the bridge portion has a thickness corresponding to a laminating direction of the electromagnetic steel sheets. A thin portion thinner than the plate thickness is provided, and the thickness of the thin portion is 0.1 to 0.1 of the front width of the bridge portion.
An induction motor characterized in that the number is 25 or less. 8. A rotor core formed by laminating a stator core, a thin electromagnetic steel plate, a stator coil provided in the stator core, an enclosed slot formed in the rotor core, and a rotor embedded in the slot by die casting. And a phase control means,
In the induction motor, wherein the slot has a bridge portion that closes the end of the slot on the side facing the stator core, the bridge portion is provided with a gap that communicates the inside and the outside of the slot during lamination of electromagnetic steel sheets. An induction motor characterized in that