JPS6240944B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a rotor by aluminum casting, such as a squirrel cage induction motor.

The rotor of a conventional squirrel-cage induction motor has a rotor core fixed to the outer periphery of a rotating shaft, and semi-closed slots, typically made of copper, are carved into the outer periphery of the rotor core parallel to the shaft. Conductive bars are attached, and both ends of these conductive bars are commonly connected by an end ring. However, forming the rotor as described above involves difficult work such as welding the end rings after inserting the conductive bars into the slots, resulting in low productivity and high cost. Therefore, recently, in order to eliminate the above-mentioned problems, small electric motors have been filled with aluminum by casting into the slots 2 carved near the surface of the rotor core 1, as shown in Figure 1. However, a so-called cast rotor in which this rotor-side conductor 3 is used is employed.

However, even with the new type of rotor formed as described above, the following questions were raised. That is, the slot 2 is normally formed in a semi-closed shape, and when aluminum is cast into the slot 2, the surface of the rotor core 1 and the surface of the aluminum cast into the slot 2 are located on the same circumference. As shown in FIG. If the rotor side conductor is provided sufficiently close to the surface of the rotor core 1 in this way, when operating with a sine wave power supply, the current will be concentrated at the step portion 4 near the rotor surface due to the skin effect during startup. This makes it difficult for leakage magnetic flux to pass through and increases the starting current to reduce leakage reactance due to local magnetic saturation. Since the tape portion 4 forms an opening and is related to the magnetic flux distribution of the gap 5, it is difficult to increase its width. Therefore, since the narrow tab portion 4 has a large electric resistance, the resistance loss at the time of starting becomes large locally, which is not preferable. On the other hand, when driving with a non-sinusoidal power source for AC variable speed,
For example, in addition to the fundamental wave, 6l±1st order (l=1, 2,
It contains time harmonic components such as 3,......). Therefore, during operation, a large skin effect due to time harmonics such as the 5th and 7th harmonics constantly occurs, and most of these harmonic power sources are mainly distributed in the tape section 4, but as mentioned above, the aperture width Since it is narrow, there was a problem that the resistance loss due to harmonics was increased.

In this way, the extra aluminum filled in the tape part 4 causes a decline in the electrical characteristics and temperature characteristics of the induction motor. Conventionally, in order to remove the aluminum in this tape part, cutting treatment is performed after casting, or molding is performed. In some cases, the tape portion was occluded, but both methods had the disadvantage of increasing the cost of the product.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a simple and inexpensive manufacturing method for a squirrel cage rotor in which narrow parts such as tape parts are not filled with aluminum.

The details of the present invention will be explained below with reference to an embodiment shown in FIGS. 2 and 3.

FIG. 2 shows a partial cross section of the rotor of the rotating electric machine according to the present invention. This rotor has a plurality of slots 2 formed in the outer peripheral edge of the rotor core 1 in parallel with an axis (not shown), and the tape portions 6 of these slots 2 are not cast with aluminum; It is cast only on the main part 7. An example of the manufacturing method of this rotor will be explained with reference to FIG.
Before the casting process, a fine-grain material such as red iron oxide (ferric oxide Fe ₂ O ₃ ), which has heat resistance and does not melt or peel off during aluminum die casting, is used as an adhesive liquid with good workability, such as water glass. Only the tape portions 6 of the slots 2 are sequentially immersed in the dissolved mixed liquid 8, so that all the slots of the tape portions 6 are filled with the mixed liquid 8. If the viscosity of this mixed liquid 8 is appropriately adjusted to the slot opening width W, it is possible to completely fill the tape portion 6. Solidification can be achieved by a chemical reaction by spraying carbon dioxide gas after all the slots of the rotor have been filled with the mixed liquid into the tape portion 6, or after each slot has been filled with the mixed liquid. If aluminum is cast after the liquid mixture 8 in all the tape parts is solidified, the molten aluminum will not enter the tape part 6 and will only fill the main slot part 7. Therefore, the solidified mixture 8 can be easily removed by subjecting the tape portion 6 to shot blasting or sand blasting after the casting process is completed. In this way, it is possible to manufacture a rotor as shown in FIG. 2 in which the tape portion 6 is not filled with aluminum. The material for the fine particles is not limited to red iron, but also fine silica sand or alumina, and the adhesive liquid may be, for example, urethane organic resin dissolved with thinner in addition to water glass. Let the thinner evaporate.

Next, a fourth example of a modified embodiment of the present invention will be described.
This will be explained using the diagram and FIG. This is the case for a double squirrel cage slot, with upper conductor 9 and lower conductor 1
A slit 11 is provided in the middle of 0. If the mixed liquid 8 is adjusted to a viscosity suitable for both the opening width W of the tape portion 6 and the width of the slit 11, the upper conductor 9 can be accommodated even if it is immersed in the mixed liquid 8 up to the bottom of the slit 11 of the slot 2. Mixed liquid 8 in the upper slot
is difficult to adhere to, and even if it remains, it can be easily removed before solidification. Therefore, after solidifying the mixed liquid 8 remaining in the tape portion 6 and the slit portion 11 with carbon dioxide gas, the liquid mixture 8 remaining in the tape portion 6 and the slit portion 11 is
If a cut is made in the end ring on the side surface of the core end corresponding to , and cast with a mold such that the upper end ring 12 is connected to the upper conductor 9 and the lower short ring 13 is connected to the lower conductor 10, the taped portion 6 can be formed. At the same time, the solidified mixture in the slit portion 11 can be removed by shot blasting or the like. In this way, a cast rotor with characteristics comparable to a bar rotor can be made. Moreover, since the upper and lower conductors are not connected, no circulating current is generated between the upper and lower conductors, which further reduces stray loss.

A liquid mixture of water glass or urethane-based organic resin mixed with red iron, silica sand, or alumina has high adhesion to the rotor core. The solidified mixture withstands the heat of aluminum casting. Since it is hard and brittle, it can be easily removed by shotblasting or sandblasting.

Furthermore, if the solidified mixture remains attached, it may peel off during rotation of the rotor, so it should be removed manually in advance. Removal in this manner is also advantageous for cooling the aluminum rottle bar and iron core.

As detailed above, according to the present invention, it is possible to inexpensively and easily manufacture a squirrel-cage rotor for a rotating electrical machine that can maximize the characteristics of a cast roll and improve starting characteristics and operating characteristics. method can be provided.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a conventional squirrel cage rotor, FIG. 2 is a partial sectional view of a rotor manufactured according to an embodiment of the present invention, and FIG. 3 is a manufacturing example of the embodiment shown in FIG. Figures 4 and 5, which illustrate the method, are a cross-sectional view and a vertical cross-sectional view, respectively, of a rotor manufactured according to another embodiment of the present invention. 1... Rotor core, 2... Slot, 3, 9,
DESCRIPTION OF SYMBOLS 10... Conductor, 4, 6... Tape, 5... Air gap, 7... Slot main part, 8... Mixed liquid, 11... Slit, 12, 13... End ring.

Claims (1)

[Claims] 1. In a method for manufacturing a squirrel-cage rotor by aluminum casting, a heat-resistant particulate material that does not melt and peel off during casting is dissolved in a sticky liquid in advance in a narrow area adjacent to the slot where aluminum is not desired to be filled. 1. A method for manufacturing a squirrel cage rotor, which comprises filling and solidifying a mixed liquid, then casting aluminum into the slots, and removing the solidified mixture by grinding after cooling. 2. The method for manufacturing a squirrel cage rotor according to claim 1, wherein the narrow portion is a tape portion or a slit. 3. The method for manufacturing a squirrel cage rotor according to claim 1, wherein the heat-resistant fine particulate material is red iron oxide, silica sand, or alumina. 4. The method for manufacturing a squirrel cage rotor according to claim 1, wherein the adhesive liquid is water glass or urethane organic resin dissolved with thinner.