JP5843980B2 - Method for manufacturing cage rotor and method for manufacturing induction motor - Google Patents

Description

  The present invention relates to a method for manufacturing a cage rotor, a method for manufacturing an induction motor, and a cage rotor.

  A squirrel-cage rotor of an induction motor includes a rotor core and a secondary conductor. The rotor core is formed with a plurality of through holes (slots) arranged in the circumferential direction. The secondary conductor includes an aluminum bar formed by filling the slot with aluminum by aluminum die casting.

  With the increasing demand for resource saving and high efficiency in induction motors, reducing losses has become an issue. Induction motor losses include iron loss, primary copper loss, secondary copper loss, mechanical loss, etc. Reduce loss by using high-performance materials or by optimizing the design of the iron core and coil. Efforts are made. In addition to these losses, there are cross current losses in which unnecessary current flows through the rotor.

  Cross current loss is an inherent potential difference between the secondary conductor and the rotor core because a potential difference occurs between the secondary conductor and the rotor core when a skew is applied to the secondary conductor of the cage rotor. It is a loss caused by a current that should not flow.

  As a method of reducing the cross current loss, as disclosed in Patent Document 1, a method of forming an insulating film on the rotor core to insulate from the aluminum, or as disclosed in Patent Document 2, the linear expansion coefficient of the metal The method of forming an air gap between the rotor core and aluminum by heating and cooling after aluminum die casting using the difference between the above and the rotor after aluminum die casting is made alkaline as disclosed in Patent Document 3 There is a method of dipping in a solution to corrode aluminum to insulate it.

Japanese Patent Laid-Open No. 2003-180056 JP-A-56-83250 Japanese Patent No. 2881328

  However, each of these methods requires a process of forming a film, a process of heating and cooling, or a process of immersing in an alkaline solution in terms of production, and each has a problem that it takes time and cost.

  The present invention has been made in view of the above, and is less likely to cause quality problems, and by using a simpler device and procedure, insulation between the secondary conductor and the rotor core is achieved to improve the efficiency of the motor. It is an object of the present invention to obtain a method for manufacturing a cage rotor that can be improved.

  In order to solve the above-described problems and achieve the object, the present invention is a method of manufacturing a cage rotor that rotates about a rotating shaft, and an aluminum die casting process is performed on a slot formed in a rotor core. And forming the aluminum bar and twisting the rotor core around the rotation axis after the formation of the aluminum bar.

  By this invention, the insulation resistance of a rotor core and a secondary conductor increases, it can suppress that an electric current flows into a rotor core from a secondary conductor, and can improve the efficiency of an electric motor.

FIG. 1 is a cross-sectional view of a cage rotor and a stator of an induction motor including a cage rotor manufactured by the manufacturing method according to Embodiment 1 of the present invention, viewed along a rotation axis. FIG. 2 is a perspective view showing a schematic configuration of a rotor core included in the cage rotor. FIG. 3 is a perspective view of a cage rotor. FIG. 4 is a perspective view of a squirrel-cage rotor for explaining a twisting process. FIG. 5 is a perspective view of a squirrel-cage rotor for explaining a twisting back process. FIG. 6 is a diagram for explaining a process of twisting the cage rotor. FIG. 7 is a view of the squirrel-cage rotor as viewed along the rotation axis. FIG. 8 is a side view of the squirrel-cage rotor and shows a state before performing the twisting process. FIG. 9 is a side view of the squirrel-cage rotor and shows a state during the twisting process. FIG. 10 is a partially enlarged view of the skew portion, and shows a state before performing the twisting process. FIG. 11 is a partially enlarged view of the skew portion and shows a state during the twisting process. FIG. 12 is a side view of a cage rotor connected to a shaft. FIG. 13 is a diagram showing the relationship between the rotational speed and torque characteristics of an electric motor using a cage rotor. FIG. 14 is a diagram showing the relationship between the rotational speed of an electric motor using a cage rotor and the efficiency characteristics.

  A method for manufacturing a cage rotor, a method for manufacturing an induction motor, and a cage rotor according to embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view of a cage rotor and a stator of an induction motor including a cage rotor manufactured by the manufacturing method according to Embodiment 1 of the present invention, viewed along a rotation axis. An induction motor 50 shown in FIG. 1 includes a cage rotor 30, a stator 40, and a shaft 11. The cage rotor 30 is rotatable around a rotation axis C that overlaps the shaft 11.

  FIG. 2 is a perspective view showing a schematic configuration of the rotor core 1 provided in the cage rotor 30. A plurality of slots 6 are formed in the rotor core 1 as through holes extending along the rotation axis C. The slots 6 are formed side by side along the circumferential direction.

  The rotor core 1 is configured by laminating a plurality of electromagnetic steel plates 2 punched in the same shape. The electromagnetic steel sheet 2 is formed with a hole for inserting the shaft 11 and a hole for the slot 6. In addition, a groove is formed in the electromagnetic steel sheet 2 from the hole serving as the slot 6 to the outer periphery of the electromagnetic steel sheet 2. By laminating the electromagnetic steel sheets 2 while shifting in the circumferential direction, a skew 5 is formed in the rotor core 1 so that the above-described grooves extend obliquely with respect to the rotation axis C. The electromagnetic steel plates 2 are connected by caulking. In the following description, a portion of the rotor core 1 sandwiched between the slots 6 is referred to as a tooth 3.

  FIG. 3 is a perspective view of the cage rotor 30. The cage rotor 30 includes the rotor core 1 and the die cast part 17 shown in FIG. The die casting portion 17 is formed by performing aluminum die casting on the rotor core 1, and includes an aluminum bar 7 made of aluminum filled in the slot 6 and the skew 5, and the rotor core 1 along the rotation axis C. And end ring portions 16 provided on both sides.

  Here, since the punching section of the rotor core 1 is not insulated, the rotor core 1 and the aluminum bar 7 are in a conductive state inside the slot 6. For this reason, a part of the current flowing through the aluminum bar 7 as the secondary conductor flows unnecessarily through the rotor core 1. Therefore, in the present embodiment, the squirrel-cage rotor 30 is twisted and the aluminum bar 7 is peeled off from the rotor core 1 in a state where the aluminum bar 7 is solid after aluminum die casting.

  FIG. 4 is a perspective view of the squirrel-cage rotor 30 for explaining the twisting process. FIG. 5 is a perspective view of the squirrel-cage rotor 30 for explaining the twisting back process. FIG. 6 is a diagram for explaining a process of twisting the cage rotor 30.

  As shown in FIG. 4, the twisting process of the cage rotor 30 is performed by rotating both ends of the cage rotor 30 in the reverse direction around the rotation axis C. Moreover, as shown in FIG. 5, the both ends of the squirrel-cage rotor 30 are rotated in the opposite direction to the twisting process, and the twisting back process is performed. In this twisting process and twisting-back process, for example, as shown in FIG. 6, the vicinity of both ends of the cage rotor 30 may be held by the chuck 8 and rotated.

  FIG. 7 is a view of the cage rotor 30 as viewed along the rotation axis C. FIG. 8 is a side view of the squirrel-cage rotor 30 and shows a state before performing the twisting process. FIG. 9 is a side view of the cage rotor 30 and shows a state during the twisting process.

  FIG. 7 shows a twist angle 10 in the twisting process. 8 and 9, the angles formed by the plane perpendicular to the rotation axis C and the skew 5 are indicated as skew angles 9a and 9b. In the twisting process for the cage rotor 30, the skew angle 9b during the twisting process is larger than the skew angle 9a before the twisting process.

  FIG. 10 is a partially enlarged view of the skew 5 portion and shows a state before the twisting process is performed. FIG. 11 is a partially enlarged view of the skew 5 portion and shows a state during the twisting process. As shown in FIGS. 10 and 11, the skew angle 9b during the twisting process is larger than the skew angle 9a before the twisting process, so that the aluminum bar 7 bends in the rotational direction, and the aluminum bar 7 and the electrical steel sheet 2 A gap in the circumferential direction is generated between the two. Further, shear is generated between the electromagnetic steel sheet 2 and the aluminum bar 7, and the aluminum bar 7 is peeled from the electromagnetic steel sheet 2 in the axial direction. Due to the occurrence of such gaps and separation between the aluminum bar 7 and the electromagnetic steel sheet 2, the contact resistance increases, and an unnecessary current flowing from the aluminum bar 7 to the rotor core 1 can be suppressed. In other words, the state where the gap or separation occurs can be said to be a state where the step of the skew 5 and the step of the aluminum bar 7 do not match.

  During the twisting process of the cage rotor 30, the cage rotor 30 moves in the direction of the rotation axis C due to an increase in the skew angle. Therefore, a force is also applied to the electromagnetic steel sheet 2 in a direction away from each other. For this reason, the rotor core 1 is pulled in the direction of the rotation axis C in accordance with the twist of the squirrel-cage rotor 30 so that excessive force is not applied to the teeth 3 and the aluminum bar 7 of the rotor core 1 and damage is caused.

  Further, during the untwisting process of the cage rotor 30, the cage rotor 30 tends to contract in the direction of the rotation axis C, contrary to the twisting process, so that the rotor core 1 is moved in the direction of the rotation axis C. By compressing to the same angle, it is possible to return to the same skew angle 9a as before the twisting process.

  Here, the torsion angle 10 shown in FIG. 7 depends on the length along the rotation axis C of the rotor core 1, and it is desirable to increase the torsion angle 10 as the rotor core 1 becomes longer. For example, when the length of the rotor core 1 is 15 to 25 mm, the twist angle 10 may be about 15 ° to 25 °. Note that if the twist angle 10 is too large, the aluminum bar 7 and the teeth 3 may be damaged.

  When it is desired to omit the step of returning the twist, the skew angle 9a can be made smaller than the desired angle in advance, and the skew angle 9b can be set to the desired angle in the twisted state. However, in this case, since a gap is generated between the electromagnetic steel plates 2, there is a possibility that the cage rotor 30 may be deformed when a compression load is applied thereto, so care must be taken.

  Moreover, it is possible not to return the twist at all, but to set the desired skew angle at the point where the twist is returned halfway.

  FIG. 12 is a side view of the cage rotor 30 to which the shaft 11 is connected. The connection of the shaft 11 to the squirrel-cage rotor 30 may be before the twisting process or after the twisting process. When the twisting process is performed after connecting the shaft 11, it is necessary to pay attention to a decrease in the connection strength between the shaft 11 and the cage rotor 30.

  The induction motor 50 is manufactured by performing other processes such as placing the cage rotor 30 manufactured in this way inside the stator 40 and accommodating the cage rotor 30 inside a housing (not shown).

  FIG. 13 is a diagram showing the relationship between the rotational speed and torque characteristics of an electric motor using a cage rotor. It can be confirmed that the torque curve 13 of the cage rotor to which the torsion is applied is larger than the torque curve 12 of the cage rotor to which the torsion is not applied.

  FIG. 14 is a diagram showing the relationship between the rotational speed of an electric motor using a cage rotor and the efficiency characteristics. It can be confirmed that the efficiency curve 15 of the squirrel-cage rotor is improved in efficiency than the efficiency curve 14 of the squirrel-cage rotor to which no twist is applied. As described above, FIGS. 13 and 14 also confirm that by twisting the squirrel cage rotor, it is possible to suppress the eddy current loss and stray load loss of the induction motor and improve the characteristics of the motor.

  As described above, by adding a twist to the cage rotor 30, the eddy current loss and stray load loss of the induction motor can be suppressed to improve the characteristics. Accordingly, since the equipment is simpler than the equipment for heating and cooling, the production line can be inlined and downsized. Further, an insulation process can be performed between the rotor core 1 and the aluminum bar 7 by a simple procedure of applying an impact. Moreover, it is possible to produce the product without increasing the number of inventory items and the number of process days, and it is possible to solve quality problems such as oxidation and thermal deformation due to high temperature.

  As described above, the cage rotor according to the present invention is useful for a method of manufacturing a cage rotor in which an aluminum bar is formed by an aluminum die casting process.

  1 Rotor core, 2 Electrical steel plate, 3 Teeth, 5 Skew, 6 Slot, 7 Aluminum bar, 8 Chuck, 9a, 9b Skew angle, 10 Torsion angle, 11 Shaft, 12, 13 Torque curve, 14, 15 Efficiency curve, 16 End ring part, 17 Die casting part, 30 Cage rotor, 40 Stator, 50 Induction motor, C Rotating shaft.

Claims (8)

A method of manufacturing a squirrel-cage rotor that rotates about a rotation axis,
A step of filling the slot formed in the rotor core with aluminum by an aluminum die casting process to form an aluminum bar;
Twisting the rotor core around the rotation axis after forming the aluminum bar, and
In the rotor core, a skew is formed with an inclination with respect to a plane perpendicular to the rotation axis,
In the step of twisting the rotor core, the rotor core is twisted in a direction in which a skew angle, which is an angle formed by a plane perpendicular to the rotation axis and the skew, is increased . .   The method of manufacturing a cage rotor according to claim 1, wherein in the step of twisting the rotor iron core, the rotor core is moved in the direction of the rotation axis.   The method of manufacturing a cage rotor according to claim 1, further comprising a step of returning the twist after the step of twisting the rotor core.   4. The method of manufacturing a cage rotor according to claim 3, wherein in the step of returning the torsion of the rotor iron core, the rotor core is compressed in the direction of the rotation axis.   The method of manufacturing a squirrel-cage rotor according to any one of claims 1 to 4, further comprising a step of performing an outer diameter finish cutting after the aluminum die casting.   The method for manufacturing a cage rotor according to any one of claims 1 to 5, further comprising a step of connecting a shaft extending along the rotation axis to the rotor core.   The method for manufacturing a cage rotor according to any one of claims 1 to 6, further comprising a step of laminating a plurality of electromagnetic steel plates and connecting them together by caulking to form the rotor core. .   A method for manufacturing an induction motor, comprising: a step of providing a stator so as to surround a cage rotor manufactured by the manufacturing method according to claim 1.

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