JPH0667158B2 - Method for manufacturing saw-shaped casting rotor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a squirrel-cage rotor of an induction motor, particularly an aluminum cast rotor.

(Prior Art) A typical example of a conventional method for manufacturing a squirrel cage rotor will be described with reference to manufacturing process diagrams shown in FIG. In the figure, 1 is a rotor blank assembling step, 2 is an aluminum conductor melting step, 3 is an aluminum die casting step, 4 is a step of taking out an aluminum casting rotor core from a die casting machine, and 6a is a heated aluminum casting step. Step of inserting the rotary shaft into the insert rotor core at a predetermined position and cooling, 5 is a step of turning the outer diameter surface of the aluminum cast rotor core to make a gear cup with the stator, 7 is the completed rotor In the steps of storing, arrows indicate the order of steps.

In the conventional manufacturing method by this step, as shown in FIGS. 6 (a) and 6 (b) in the first step, the shaft hole 9 for fitting the rotor shaft to the electric iron plate and the rotor conductor are housed. The slot 10 for punching is punched with a press machine and the rotor punched 1
Then, a predetermined number of these are stacked to form the rotor core 12. Second
In the process, the conductor aluminum is heated and melted.
In the third step, the molten aluminum is introduced into a die casting machine, high pressure is applied to the molten aluminum to die cast the rotor core 12 assembled in the first step, and in the fourth step, the seventh step is performed.
As shown in the figure, an aluminum cast-in cage rotor core (hereinafter referred to as a cast rotor core) integrally formed with a slot bar 13, a short-circuit ring 14, and a cooling vane 15 is taken out from the die casting machine. In the fifth step, the casting rotor core is heated to a temperature of 200 to 400 ° C at which the rotating shaft can be sufficiently shrink-fitted, and then the rotating shaft is inserted into the inner diameter of the casting rotor core at a predetermined position to form a rotor. Cooling. Further, in the sixth step, the outer diameter surface 12a of the iron core of the rotor having the rotary shaft shrink-fitted is turned to form a gear cup with the fixed shaft. The seventh step is a step of storing the completed rotor.

The rotor of the induction motor obtained by the above steps has the following problems in terms of efficiency and torque characteristics. That is, a rotor core composed of laminated rotor blanks 11
When 12 is cast into aluminum as a rotor conductor by an aluminum die-casting manufacturing method, the aluminum slot bar 13 and the slot 10 of the rotor core 12 are in close contact with each other. Therefore, the slot bar 13 and the slot 10 of the rotor core are electrically connected to each other, and the secondary current flowing through the slot bar 13 during rotation of the rotor causes a short circuit current between the slot bars 13 through the rotor core 12 to cause stray. This causes load loss and stray torque, resulting in deterioration of the efficiency of the induction motor during operation and deterioration of acceleration characteristics at the time of starting.

For this reason, in order to obtain an induction motor with better characteristics than the current one, as shown in FIGS. 8 (a) and 8 (b), the inner peripheral portion of the slot 10 of the rotor blank 11 has a water-soluble inorganic insulating material. After the treatment liquid is adhered, it is dried and solidified to form the rotor slot insulating film 16, and the slot bar 13 and the rotor core.
A method of electrically insulating 12 slots 10 from each other and reducing stray load loss and stray torque has been put into practical use. (For example,
However, as shown in Figures 8 (a) and 8 (b), the semi-closed slot-shaped rotor blank 11 has an outer diameter of the iron core of the rotor in the sixth step. By turning the surface 12a to form a gear gap with the stator, the bridge 17 by turning is formed between the slot bar 13 and the rotor iron core 12 on the outer diameter surface 12a of the iron core.
(Short circuit part) occurs and the slot bar 13 and the rotor core 12 make electrical contact, and the above-mentioned method using the rotor slot insulating coating 16 can sufficiently reduce the stray load loss and stray torque of the induction motor. I can't. As a method of reducing the stray load loss and stray torque generated by turning the outer diameter surface 12a of the rotor iron core, the rotor core 12 is fitted with the rotating shaft, and then the turning process is performed. There is a so-called heat shock treatment method in which the vicinity of the iron core outer diameter surface 12a of the child is heated to a temperature of about 400 ° C. by a gas burner or the like and then water-cooled. FIG. 9 shows a process diagram in which the heat shock process 8 is added to the representative process diagram of the method for manufacturing the squirrel cage rotor described in FIG. The heat shock step 8 is characterized in that it is incorporated as a step subsequent to the step 5 of forming the gear with the stator by turning the iron core outer diameter surface 12a of the rotor as the seventh step. As a result, the tenth
As shown in the rotational speed N-torque T characteristic diagram in the figure, the characteristic c of the electric motor having the squirrel cage rotor subjected to the heat shock treatment as shown in the process chart in FIG. 9 is shown in the process chart in FIG. As shown, the starting curve is significantly improved as compared to the characteristic b of the electric motor having a cage rotor that is not heat-shocked. That is, in the case where the heat shock treatment is not performed, there is a slack in the torque during acceleration, whereas in the case where the heat shock treatment is performed, this slack can be reduced. In addition, in FIG. 10, Ns is a synchronous rotation speed.

(Problems to be Solved by the Invention) The method of adding the heat shock treatment step described above is the extra heat energy for adding the heating / cooling step to the conventional step, the heating / cooling time and the step thereof. There is a disadvantage that the occupied area of the product that is stagnant increases.
Moreover, in the heat shock treatment process, since only the outer surface of the squirrel cage rotor is locally heated by a gas burner or the like, the aluminum slot bar with a low melting point is melted at the outer diameter surface of the iron core of the rotor to induce the heat. There was a problem that the characteristics of the electric motor deteriorate.

The object of the present invention is to prevent the stray load loss and the stray torque of the induction motor from increasing in a squirrel-cage rotor having a semi-closed slot-shaped rotor blank in an extremely simple process without performing heat shock treatment, thereby improving the operating efficiency. To improve acceleration characteristics at the time of starting.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, in the present invention, the outer diameter surface of the cast rotor core after aluminum casting is turned to form a prescribed outer diameter dimension. The temperature of this cast rotor core is 200 to 400 ° C.
(EN) Provided is a squirrel-cage rotor which is heated to a certain position and the rotating shaft is inserted into a predetermined position and then rapidly cooled.

(Working) Since it is configured in this way, the bridging between the slot bar and the rotor core generated by turning the outer diameter surface of the cast rotor core in the fifth step is Due to the difference in the expansion coefficient between aluminum and iron during the rapid cooling after inserting the rotary shaft, the bridging of the slot bar was separated from the rotor core.
An insulating layer is formed in the space to prevent current leakage from the slot bar to the rotor core.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings. First
A manufacturing process diagram is shown in the drawing, and a rotational speed N-torque T characteristic diagram is shown in FIG. 2, and the same parts as in the prior art will be described using the same reference numerals.

In FIG. 1, 1 is a rotor blank assembling process, 2 is an aluminum conductor melting process, 3 is an aluminum die casting process, and 4 is a process.
Is the process of taking out the cast rotor core from the die casting machine, 5
Is a process of turning the outer diameter surface of the cast rotor core to make a gear with the stator, 6 is a process of inserting the rotary shaft into the heated cast rotor core at a predetermined position and water cooling, 7 is completed In the process of storing the rotor, the arrows indicate the order of the process.

The manufacturing method of the present invention differs from the conventional example shown in FIG. 5 in the following points. First, in the fifth step,
With reference to the shaft hole 9 of the cast rotor core in a state in which the rotary shaft is not inserted in the cast rotor core as shown in FIG. 7, the outer diameter surface 12a of the rotor core 12 is turned and the stator ( (Not shown). Subsequently, in a sixth step, after heating the rotor core 12 to 200 to 400 ° C., which is a temperature at which the rotary shaft can be sufficiently shrink-fitted, the rotor core 12 is inserted into a predetermined position of the rotary shaft to form a rotor. Immediately water cooling.

Due to the bridge 17 between the aluminum conductor slot bar 13 and the rotor core 12 on the outer diameter surface 12a of the rotor core 12, which is generated by turning the outer diameter surface 12a of the rotor core 12 in the fifth step. The close electrical contact is released by heating the rotor in the sixth step and then cooling it with water. That is, the step of inserting the rotary shaft into the heated casting rotor core at a predetermined position and water-cooling in the sixth step is a step subsequent to the turning step of the outer diameter surface of the casting rotor core in the fifth step. To do. As a result, the close electrical contact between the aluminum conductor slot bar 13 and the rotor core 12 produced in the fifth step is caused by the rotor being heated to a high temperature in the sixth step and the slot bar 13 and the rotor core 12 are Both of them expand, but they are peeled off due to the difference in expansion coefficient between the aluminum and the iron plate, and immediately thereafter are rapidly cooled to room temperature, so that the above peeling phenomenon is further promoted.

As a result, the rotor core 12 is electrically insulated from the aluminum conductor slot bar 13 on the outer diameter surface 12a of the rotor core 12. Therefore, the secondary current flowing through the slot bar 13 during the rotation of the rotor does not generate a short-circuit current between the slot bars 13 through the rotor iron core 12, and the stray load loss and stray load torque occur in the induction motor, resulting in the efficiency during operation. Does not deteriorate or the acceleration characteristic at the time of starting does not deteriorate. As shown in the rotational speed N-torque T characteristic diagram of FIG. 2, the characteristic a of the induction motor having the squirrel-cage rotor of the present embodiment by the process is the squirrel-cage rotor without heat shock treatment by the conventional manufacturing method. Characteristics b of induction machine with
The starting curve is greatly improved compared to. That is, the characteristic b by the manufacturing process of FIG. 5 has a slack in the torque during acceleration, whereas the characteristic a by the manufacturing process of this embodiment can reduce this slack. Moreover, as shown in FIG. 10, the characteristic a of the induction motor having the squirrel-cage rotor according to the manufacturing process of FIG. 1 which is the manufacturing method of the present embodiment is as shown in FIG. Further, the starting curve could be improved to be approximately equal to or higher than the characteristic c of the induction motor having the squirrel cage rotor by the conventional manufacturing method.

In addition, among the stray load losses of the rotor, one of the means for evaluating the loss caused by the close electrical contact between the rotor iron slot bar 13 of the rotor and the rotor core 12 Examples of the results of measuring the cross current loss are shown in FIGS. 3 and 4. This is the first embodiment shown in FIG.
The rotor cross current loss due to the manufacturing process shown in the figure is about 5w, while the rotor cross current loss due to the conventional manufacturing process shown in Fig. 4 is about 32w when the heat shock process 8 is not performed.
The stray load loss of the rotor is reduced by the manufacturing process of this embodiment. The cross current loss of the rotor by the manufacturing process of this embodiment shown in FIG. 3 is equivalent to that when the heat shock process 8 is performed by the cross current loss of the rotor by the conventional manufacturing process shown in FIG. By the manufacturing process of this embodiment shown in FIG. 1, the stray load loss of the rotor can be improved to the same extent as in the conventional heat-shocked manufacturing process shown in FIG. In addition, since the heat shock process 8 is not added, the extra heat energy for adding the heating / cooling process to the conventional process, the heating / cooling time, and the area occupied by the product stagnant in the process are reduced. There is a benefit to

Further, in the heat shock step 8, since only the vicinity of the outer diameter surface 12a of the rotor is locally heated by the gas burner or the like, the slot bar 13 of the aluminum conductor having a low melting point is melted at the outer diameter surface portion of the rotor and the induction motor Since there is a problem that the characteristics are deteriorated, the present embodiment has an effect that equivalent characteristics can be obtained without performing the heat shock step 8.

As shown in FIGS. 8 (a) and 8 (b), the rotor blank 11
By forming the rotor slot insulating coating 16 on the circumferential portion of the slot 10, the effects of the present invention described above are further improved.

[Effects of the Invention] As described above, according to the present invention, in a squirrel-cage rotor having a semi-closed slot-shaped rotor blank, a stray load of an induction motor can be achieved by an extremely simple process without heat shock treatment. It is possible to prevent loss and increase in stray torque, and improve operating efficiency and acceleration characteristics at the time of starting.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a rotor according to an embodiment of the present invention,
FIG. 2 is a rotational speed-torque characteristic diagram thereof, FIG. 3 is a change diagram of cross current loss according to the manufacturing process of the present invention shown in FIG. 1, FIG. 4 is a change diagram of conventional cross flow loss according to the manufacturing process, and FIG. The figure is equivalent to FIG. 1 of the prior art, FIGS. 6 (a) and 6 (b) are front and sectional views of a rotor blank having a half-closed slot, and FIG. 7 is a conventional cast aluminum cage rotor. FIG. 8 (a) is a front view of a conventional semi-closed slot having an insulating coating formed thereon, FIG. 8 (b) is its cross-sectional view, and FIG. 9 is a conventional manufacturing process shown in FIG. Manufacturing process diagram with heat shock process added to process, 10th
The figure is a rotational speed-torque characteristic diagram. 9 …… Shaft hole, 10 …… Slot, 11 …… Rotor blank, 12 …… Rotor core, 12a …… Outer surface of rotor core, 13 …… Slot bar.

Claims (1)

[Claims] Claim: What is claimed is: 1. A molten rotor is cast into a slot of a rotor core having a semi-closed slot to form a cast rotor core, and the outer diameter of the cast rotor core is turned and heated to a temperature of 200 to 400 ° C. A method for manufacturing a squirrel-cage cast rotor, characterized in that the rotary shaft is inserted into the shaft hole of the cast rotor core and then rapidly cooled.