JPS58207848A - Rotor core for induction motor - Google Patents

Abstract

PURPOSE:To increase the torque of an induction motor by providing a semi- closed slot having the size of an opening of the prescribed length at the time of punching cores. CONSTITUTION:A semi-closed slot 3 is set in the total area of the slot 3 to the total area of a rotor core 1, i.e., the area ratio to 0.25 or less, and the opening having the size W of 0.2-0.6mm. is formed at the time of punching the core 1. Thus, the opening of the slot is specified to the size W, thereby eliminating the cutting work of the outer periphery of the rotor to enhance the productivity, and removing the cause of lowering the insulation of the rotor slot. Accordingly, the torque can be enhanced and the efficiency can be raised.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotor core of an induction motor, which has high performance and
Moreover, the present invention relates to a rotor core of an induction motor, which is used to obtain an induction motor with good productivity.

The rotor core of a conventional induction motor has an opening size of 08 to 1.5 fl, and there are two types: a half-closed slot type and a fully closed slot type.

The former half-closed slot type has the disadvantage that the opening reduces the area through which the magnetic flux passes, increasing the excitation current, resulting in high power consumption and high noise.

On the other hand, the latter fully closed slot type Monazu has the feature of low noise because it is fully open and has no opening, but it has the disadvantage of increased leakage magnetic flux and low output. .

Conventionally, the rotor core and the stator core were generally manufactured by simultaneous punching from silicon steel sheets, and after die-casting the secondary conductor on the laminated material, the gap size (usually 0.20 to 0.30 wn) was fabricated. ) was used to cut the outer diameter of the rotor by machining.

In this case, as shown in Fig. 1, the semi-closed slot type rotor core mentioned earlier is cut out in advance as a fully closed slot type, laminated, die-cast the secondary conductor, and then machined into half. It was designed to have a closed slot shape.

That is, the slots 3a of the rotor core 1a are in the form of fully closed slots on the outer periphery of the rotor core 1a, and after stacking and die-casting, the slots 3a of the rotor core 1a are cut to a rotor outer diameter of 4, and the opening size is An opening W-1 is formed.

This is because if a semi-closed slot type is first formed, the hot water will leak from the opening during die casting, causing hot water to form on the outside diameter, resulting in a marked decrease in productivity due to mold galling, and furthermore, performance will be reduced due to eddy current loss. This is to prevent inferiority.

On the other hand, in the case of induction motors, it is said that a decrease in the groove insulation performance of the rotor slot is a major factor that significantly reduces the performance.As a result of detailed experimental investigation of the cause, the following was clarified. Ta.

- First, the first factor is that during die casting, the rotor slots are filled with molten aluminum under high pressure (500 K9/'cm2 or more) in an extremely short time (0.1 to 0.15 SeC), but the inside of the slots It was confirmed that air is trapped within the aluminum at high pressure, which causes the conductor to adhere tightly to the slot's inner wall, reducing insulation resistance.

However, in the current die-casting technology, this is unavoidable, so conventionally a method of insulating the inner wall of the slot has been adopted.

Next, the second factor is that the conductor and the slot inner wall come into close contact with each other due to the strain caused when cutting the outer diameter of the rotor, resulting in a decrease in insulation resistance.

In order to recover from the deterioration caused by this second factor, heat treatment after processing has generally been used, but this method is not necessarily effective against the deterioration caused by the first factor mentioned earlier. Conventional induction motors have the disadvantage that their performance is much lower than the theoretical value and also has large variations.

An object of the present invention is to provide a rotor core for an induction motor, which eliminates the drawbacks of the prior art as described above and is used to obtain a high-performance and highly productive induction motor. It is.

The main point of the present invention is that in the rotor core of an induction motor, 0
．． By providing a half-open slot having an opening size of 2 to 0.6 nun when punching the core, a high-performance induction motor with low power consumption can be obtained at a low price.

A feature of the present invention is that, before die-casting the two-inductor receptacle, a semi-closed slot with an opening is formed in the rotor core of an induction motor.
The rotor core of an induction motor has a half-open slot having an opening size of 2 to 0.6 trm.

Next, an embodiment according to the present invention will be described with reference to FIG. 2.3.

Here, FIG. 2 is a partial plan view of a rotor core of an induction motor according to an embodiment of the present invention, and FIG. 3 shows slot opening dimensions, no-load input, and occurrence of cast burrs during die casting. It is a characteristic diagram.

In Fig. 2, 1 is the rotor core, 2 is the tooth, and 3 is the rotor core.
is a semi-closed slot, and W indicates the opening size.

Therefore, the total area of the half-open slots 3 to the total area of the rotor core 1, that is, the area ratio of the half-open slots 3 is set within 0.25, and when the rotor core 10 is punched out, the opening dimensions shown in the figure are An opening indicated by W is formed.

Although this may be a little different, as mentioned earlier, in the conventional type shown in FIG. Thereafter, the rotor was cut to an outer diameter of 4 to form an opening having an opening dimension W-1 of 0.8 to 1.5 m.

In contrast, in this embodiment, as described above,
An opening is formed during punching, and the opening dimension W is 0.
It was set to 2 to 0.6 ran.

The opening dimensions were selected from the viewpoint of both power consumption characteristics and productivity during die casting.

In other words, as mentioned above, Fig. 3 is a characteristic diagram showing the slot opening size, no-load input, and the occurrence of burrs during die-casting, but the no-load current in this data is for the same slot shape. The results were obtained through experiments in which only the opening method W was changed from a completely closed type (opening size 0) to 1.4 mm.

As shown in the figure, the no-load input decreases as the opening size W becomes smaller, reaching a minimum around 0.4 m+, but increases as the opening size W becomes smaller.

This is because as the opening size W becomes smaller, the leakage magnetic flux due to the secondary current increases and the loss increases, and at the same time, the torque also decreases.

Further, in this example, since an opening is provided before die casting, burrs A and B indicate the occurrence of cast burrs generated from this opening.

C, and this data shows the values of cast burr for each opening size W when the ratio of the total slot area to the total area of the rotor core (area ratio) is varied in the range of 0.15 to 0.35. These are the experimental results of the occurrence situation.

Rank A is a range where there is almost no occurrence of cast burrs, rank B is a range where some cast burrs are generated but it does not pose a practical problem, and porcelain C is a range where cast burrs are generated, resulting in post-processing. This indicates the range that cannot be put to practical use unless these steps are taken.

As described above, according to FIG. 3, when the opening dimension W is set in the range of 0.6 to 0.2 m with the lowest power consumption, if the above-mentioned area ratio is set within 0.25, during die casting. It was confirmed that the problem of casting burrs did not occur.

By the way, when the specific area becomes smaller, the solidification time is shortened due to the relationship between the heat capacity of the low-temperature rotor core and the heat capacity of the high-temperature aluminum filled in the slot during die-casting. Although the occurrence of casting burrs is reduced, at the same time, the flowability of the metal is reduced.

That is, in the past, in order to insulate the groove between the secondary conductor and the rotor core, it was necessary to cover the core with phenol or other material and then perform die casting. If the area ratio is small (slot area is small), the coating phenol etc. will gasify during die casting, which will obstruct the flow of the molten metal.

For this reason, conventionally, the area ratio has been set to a large value of about 0.2 to 0.35.

On the other hand, according to the present embodiment, a coating treatment such as a phenol treatment is not required for the reason described below, so that the area ratio can be reduced.

In other words, during die casting, air and gas are released from the opening of the slot, so the internal pressure of the secondary conductor inside the slot does not increase, and as the temperature decreases, the conductor with a large coefficient of thermal expansion contracts more. As a result, it was observed that a gap was formed between the slot and the inner wall, and it was confirmed that the insulation resistance was maintained at an extremely high level.

Note that if the slot area is made smaller, the secondary resistance can be maintained the same by making the end ring larger, so there is no problem in practice.

As described above, according to this embodiment, it is possible to eliminate the cutting process on the outer diameter portion of the rotor, which not only increases the productivity, but also eliminates the cutting process in this way. Since the factors that reduce the groove insulation of the rotor slots can be completely eliminated, it is possible to provide an induction motor with high torque and high efficiency with good productivity.

Regarding this decrease in groove insulation, in the conventional semi-closed slot type and fully closed slot type, during die casting, since there is no opening in the slot, the air in the slot and the scum in the molten aluminum are under high pressure. Insulation resistance decreases due to the conductor sticking to the slot inner wall due to being trapped in the slot, and furthermore, during outer diameter machining, the conductor and rotor core come into close contact, causing a decrease in insulation resistance and a decrease in torque. However, in this example, as mentioned earlier, air and gas are released from the slot opening during die casting, and there is no cutting on the outer diameter part, so the conductor There is no adhesion to the inner wall of the slot, no close contact between the conductor and the rotor core, and a gap is created between the conductor and the inner wall of the slot, allowing an extremely high insulation resistance to be maintained.

Taking all of the above into account, the present invention can provide a rotor core for an induction motor that can provide a high-performance and highly productive induction motor, and is practical. It can be said that this invention is highly effective.

[Brief explanation of drawings]

FIG. 1 is a partial plan view of a rotor core of a conventional induction motor, FIG. 2 is a partial plan view of a rotor core of an induction motor according to an embodiment of the present invention, and FIG. 3 is a slot opening size. FIG. 3 is a characteristic diagram showing the no-load input, and the occurrence of cast burrs during die casting. 1... Rotor core, 2... Teeth, 3... Half-closed slot, W... Opening dimension. Agent Patent attorney Kosaku Fukuda (and 1 other person) Figure 1 Figure 1α Figure 2

Claims (1)

[Claims] 1. Before die-casting the secondary conductor casting reservoir, the slot in the rotor core of a small induction motor, which is designed to form a half-open slot with an opening, is 0.2-0.
A rotor core for an induction motor, characterized in that it has a semi-closed slot having six opening dimensions. 2. A rotor core of an induction motor according to claim 1, wherein the total slot area is set such that the ratio of the total slot area to the total area of the rotor core is within 0.25. .