JP2000023427A - Manufacture of induction motor rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an induction motor rotor in which the increase of the density of a secondary conductor formed by aluminum die-cast is realized and a secondary resistance is reduced easily by a method wherein the secondary conductor is deformed by plastic deformation to compress gas pockets in the secondary conductor while an electrical short-circuit between a rotor bar of which the secondary conductor consists and a core consisting of layered electrical sheets and the specific electrical resistance of the secondary conductor are not changed. SOLUTION: After a secondary conductor 2 is formed by aluminum die- casting, the secondary conductor 2 is heated by the heat transmission from a fixed side heating unit 9 and a movable side heating unit 10. A forming pressure is applied to the secondary conductor in the axial direction of the rotary shaft of an induction motor rotor 1 through both heating units to deform the secondary conductor by plastic deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an induction motor rotor.

[0002]

2. Description of the Related Art A conventional induction motor rotor is obtained by molding a secondary conductor by aluminum die-casting. A gate is provided at a fixed-side end ring, and molten aluminum is injected at a high speed.

A method for manufacturing an induction motor rotor in which cavities generated inside a secondary conductor are reduced by aluminum die casting is disclosed in Japanese Patent Application Laid-Open No. Hei 6-133506. FIG. 2 shows a conventional manufacturing method. As shown in FIG. 2, molten aluminum is simultaneously injected from a fixed gate 11 provided on a fixed end ring and a movable gate 12 provided on a movable end ring. And a method for manufacturing an induction motor rotor for forming the secondary conductor 13. In this manufacturing method, since molten aluminum is injected from the fixed-side gate 11 and the movable-side gate 12, the molten metal flow distance is less than half that in the case of single-sided injection.
The injection speed of the molten aluminum is reduced and the secondary conductor 13
It is possible to obtain a high-density secondary conductor by suppressing gas entrainment, which is a main cause of nest generation.

The induction motor rotor with reduced nests disclosed in Japanese Patent Application Laid-Open No. 7-298582 has a core formed by laminating electromagnetic steel sheets, and connects the inside and outside of the slot between the laminations. A high-density secondary conductor is obtained by providing a gap and discharging gas from the gap during aluminum die casting.

[0005]

This induction motor rotor has a rotor bar and a magnetic steel sheet which can easily reduce nests inside a secondary conductor formed by aluminum die-casting. It is required to easily manufacture an induction motor rotor having a high secondary conductor density and a low secondary resistance without changing an electrical short-circuit state with a laminated core. I have.

However, in the above-mentioned conventional motor rotor manufacturing method for forming a secondary conductor by aluminum die casting, since a molten metal is injected at a high speed by providing a gate at a fixed end ring, the molten aluminum is in a turbulent state. The gas is injected into the molding chamber and entrains the gas present in the molding chamber, so that a cavity is formed inside the secondary conductor. In addition, when the release agent used during aluminum die casting comes into contact with the molten aluminum, it is vaporized and causes cavities.
Therefore, it is difficult for conventional aluminum die casting to reduce cavities generated inside the secondary conductor.

Further, by injecting the molten aluminum, the gas present in the molding chamber flows toward the gate. Therefore, in a method of manufacturing a motor rotor in which a sprue is provided on the fixed side and the movable side end ring portions and molten aluminum is simultaneously injected from each sprue, the gas is confined in the slot, and the rotation formed by aluminum die casting in the slot. The child bar can be discontinuous, making it difficult to obtain a complete secondary conductor. Further, it is difficult to remove the solidified aluminum present in the movable runner after the aluminum die casting. Therefore, the mold structure becomes complicated, which leads to an increase in mold cost. Further, the mold structure becomes complicated to enable injection from the movable side end ring portion, which leads to an increase in mold cost.

In order to obtain a high-density secondary conductor, it is important to release gas from the entire molding chamber. A gap is provided between the inside and the outside of the slot, and the gas existing inside the slot is made of aluminum. Even if the gas can be released to the outside of the slot during die casting, the released gas enters the end ring molding chamber on at least one side, and if the gas cannot be released from the end ring molding chamber, nests are generated inside the end ring. . Therefore, it is difficult to obtain a high-density secondary conductor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and provides an electrical short-circuit between a rotor bar constituting a secondary conductor and a core formed by laminating electromagnetic steel sheets. The secondary conductor formed by aluminum die casting is plastically deformed without changing the electrical resistivity of the conductor, and the nest existing inside the secondary conductor is compressed and reduced, realizing a high density of the secondary conductor. Another object of the present invention is to easily manufacture an induction motor rotor having a reduced secondary resistance.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a heating element arranged on an end surface or a side surface of at least one end ring after aluminum die-casting a secondary conductor formed by aluminum die-casting. Heating within the temperature range of the recrystallization temperature of aluminum, which is the material of the secondary conductor, and below the liquid phase generation temperature due to the heat conduction, and applying molding pressure from the rotation axis direction of the induction motor rotor via the heating element This is a method for manufacturing an induction motor rotor to be deformed.

According to the above-mentioned means, the aluminum die-casting can be performed without changing the electrical short-circuit state between the rotor bar constituting the secondary conductor and the core formed by laminating the electromagnetic steel sheets, and the electrical resistivity of the secondary conductor. By plastically deforming the secondary conductor formed by, and compressing and reducing the nests inside the secondary conductor, the density of the secondary conductor is increased and the induction motor rotor with reduced secondary resistance is easily manufactured. It is possible to manufacture.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to an induction motor rotor made of aluminum die-cast, in which a secondary conductor formed by aluminum die-casting is rotated by a heating element via a heating element. A method for manufacturing an induction motor rotor characterized by plastic deformation by applying a molding pressure from a direction, plastically deforms a secondary conductor formed by aluminum die casting, and compresses nests inside the secondary conductor. It has the effect that it can be reduced.

According to a second aspect of the present invention, there is provided the method of manufacturing an induction motor rotor according to the first aspect, wherein a secondary conductor formed by aluminum die casting is heated. The effect is that the strength of the secondary conductor can be reduced.

According to a third aspect of the present invention, the secondary conductor formed by aluminum die-casting is heated within a temperature range from the recrystallization temperature of aluminum, which is the secondary conductor material, to the liquid phase generation temperature. The method of manufacturing an induction motor rotor according to claim 2, which has an effect that it is possible to suppress distortion generated inside a secondary conductor that is plastically deformed by molding pressure.

According to a fourth aspect of the present invention, a secondary conductor formed by aluminum die casting is heated by heat conduction of a heating element disposed on an end surface or a side surface of at least one side of an induction motor rotor. 3. The method for manufacturing an induction motor rotor according to claim 2, wherein the end ring on at least one side of the secondary conductor can be preferentially heated as compared with the rotor bar. It has the effect of being.

[0016]

FIG. 1 shows a method of manufacturing an induction motor rotor according to the present invention. In FIG.
Is a secondary conductor, 3 is a fixed end ring that constitutes a secondary conductor, 4 is a movable end ring that constitutes a secondary conductor, 5 is a rotor bar that constitutes a secondary conductor, 6 is a core, and 7 is fixed. A side end ring forming jig, 8 is a movable side end ring forming jig, 9 is a fixed side heating element, and 10 is a movable side heating element.

The induction motor rotor 1 is formed by laminating a secondary conductor 2 (fixed end ring 3, movable end ring 4, and rotor bar 5) formed by pure aluminum die casting, and an electromagnetic steel plate. It is constituted by a core 6. The volumes of the fixed-side end ring 3 and the movable-side end ring 4 after the aluminum die-casting are slightly larger than the volume of the finished product, and the amounts thereof are the fixed-side end ring 3 and the movable-side end ring 3 formed by aluminum die-casting. The ratio of a value obtained by subtracting the actual density of the end ring from the theoretical density of pure aluminum as a material of the ring 4 and the theoretical density, or a value obtained by subtracting the actual density of the end ring from the target density and the target density The ratio was used. For example, theory (goal)
Assuming that the density is 2.7 and the actual density is 2.6, the end ring volume is increased by 3.7%. In this case, the volume is increased by increasing the end ring height (in the direction of the rotation axis of the induction motor rotor) of both the fixed end ring 3 and the movable end ring 4.

As described above, in the induction motor rotor 1 in which the volumes of the fixed end ring 3 and the movable end ring 4 are increased, the fixed end ring forming jig 7 is attached to the fixed end ring 3 and the movable end ring 4 is fixed. The movable-side end ring forming jig 8 is set on the end surface of the end ring forming jig, and the induction motor rotor is provided via the fixed-side heating element 9 and the movable-side heating element 10 arranged on the end surface of the end ring forming jig (the end ring side). The fixed end ring 3 and the movable end ring 4 were plastically deformed by a pressurizing and heating device (not shown in FIG. 1) capable of applying a molding pressure from the rotation axis direction. Further, the heating element is heated by direct energization to the fixed-side heating element 9 and the movable-side heating element 10, and the fixed-side end ring 3 and the movable-side end ring are preferentially compared with the rotor bar 5 by the heat conduction. 4 was heated. The molding conditions are a molding pressure of 40 MPa, a heating temperature of the secondary conductor 2 (surface temperature of the fixed-side end ring molding jig 7) 300 ° C. or more and 450 ° C.
It was as follows. At a molding pressure of 40 MPa, when the heating temperature of the secondary conductor 2 is higher than 450 ° C., the gas pressure in the cavity generated inside the fixed end ring 3 and the movable end ring 4 increases, and the plastic deformation of the end ring decreases. The result was disturbing.

In the induction motor rotor 1 manufactured by the above method, the density of the fixed side end ring 3 is 3.0%,
It was possible to improve the density of the movable side end ring 4 by 4.4%. No change was observed in the density of the rotor bar 5. Therefore, the density of the secondary conductor 2 can be increased without changing the electrical short-circuit state between the rotor bar 5 and the core 6 (average of the fixed end ring 3, the movable end ring 4, and the rotor bar 5). Density improvement), and an induction motor rotor with a reduced secondary resistance was obtained. As a result, it has become possible to improve the motor efficiency.

The case where the fixed end ring and the movable end ring are heated preferentially and plastically deformed as compared with the rotor bar has been described. However, the end ring on one side is compared with the rotor bar. In the case of preferential heating, only the heating element on the heated side may be used, and the same result is obtained for the end ring on the heated side. Also, the case where direct heating to the heating element is used as the heating means has been described, but similar results can be obtained by using induction heating. Further, if it is possible to prevent the characteristics of the induction motor rotor from deteriorating due to a change in the electrical short-circuit state between the rotor bar 5 constituting the secondary conductor and the core 6 formed by laminating the magnetic steel sheets, By increasing the molding pressure and the heating temperature of the secondary conductor 2, it is possible to increase the density of the secondary conductor and shorten the molding time more than this time.

[0021]

As described above, according to the first aspect of the present invention, the densities existing inside the secondary conductor formed by aluminum die casting are compressed and reduced, thereby realizing a high density of the secondary conductor. In addition, it is possible to easily manufacture an induction motor rotor having a reduced secondary resistance. In addition, in the case of aluminum die casting, since molten aluminum is injected only from the fixed side end ring portion as in the past, it is possible to obtain a continuous rotor bar shape. Also, the mold structure can be made simple as before.

Further, according to the second aspect of the invention, the secondary conductor can be easily plastically deformed, and the first aspect of the invention can be implemented.

Further, according to the third aspect of the invention, it is possible to prevent an increase in the electrical resistivity of the secondary conductor, and it is possible to more easily implement the second aspect of the invention.

Further, according to the invention of claim 4, without changing the electrical short-circuit state between the rotor bar constituting the secondary conductor and the core formed by laminating the magnetic steel sheets, The first and second aspects of the invention can be implemented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a method of manufacturing an induction motor rotor according to the present invention.

FIG. 2 is a sectional view showing a method for manufacturing a conventional induction motor rotor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Induction motor rotor 2 Secondary conductor 3 Fixed side end ring which comprises a secondary conductor 4 Movable side end ring which comprises a secondary conductor 5 Rotor bar which comprises a secondary conductor 6 Core 7 Fixed side end ring forming jig Tool 8 Movable end ring jig 9 Fixed heating element 10 Movable heating element

Claims (4)

[Claims] 1. An induction motor rotor in which an aluminum die-casting induction motor rotor is characterized in that a secondary conductor formed by aluminum die-casting is plastically deformed by applying a molding pressure in a direction of a rotation axis of the induction motor rotor. Child manufacturing method. 2. The method for manufacturing an induction motor rotor according to claim 1, wherein a secondary conductor formed by aluminum die casting is heated. 3. The method according to claim 2, wherein the secondary conductor formed by aluminum die-casting is heated within a temperature range not lower than a recrystallization temperature of aluminum as a secondary conductor material and lower than a liquid phase generation temperature. Manufacturing method of induction motor rotor. 4. A secondary conductor formed by aluminum die casting is heated by heat conduction of a heating element disposed on an end surface or a side surface of at least one side of an induction motor rotor. 3. The method for manufacturing an induction motor rotor according to item 2.