JPH0614506A - Multistage-type induction motor - Google Patents

Abstract

PURPOSE:To provide an induction motor wherein its stator and its rotor can be made long without spoiling the shaping property of a cutting and working operation and a die casting operation and without spoiling the flexural rigidity of a shaped product and its output is high. CONSTITUTION:An induction motor 10 is provided with the following: two rotor cores 14 which are fixed to a shaft 12 by keeping a prescribed interval in the axial-line direction; and two stator cores 22 which surround the individual rotor cores 14 respectively and which are fixed to a sleeve part 20 for a motor housing 18. The individual rotor cores 14 are provided with following so as to be shaped integrally: a plurality of aluminum die-cast secondary conductors 16 which are extended to the axial-line direction; and aluminum die-cast end rings 28 which are connected to the individual secondary conductors 16 at both ends of the axial-line direction of the rotor cores 14. The individual stator cores 22 are provided with a plurality of primary windings 24. The rotor cores and the stator cores 22 are formed to be about a length which does not spoil the shaping property of a die casting operation and cutting and working operation and the flexural rigidity of a shaped product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor, and more particularly to a multi-stage induction motor in which a stator and a rotor are elongated in a plurality of stages to obtain a high output. This induction motor can be used as a built-in spindle motor that is directly incorporated in the spindle of a machine tool.

[0002]

2. Description of the Related Art A spindle motor for driving a spindle of a machine tool requires high output, but does not require high-precision controllability, so that an induction motor is generally used. recent years,
In order to improve the capability of machine tools, spindle motors are being increased in speed and output, and in particular, there is an increasing tendency to use a spindle-integrated built-in spindle motor. The built-in spindle motor has the advantage that the entire structure is simple because it is built directly into the main shaft without a gear train or other transmission mechanism, but in order to obtain high output, the structure of the motor itself must be improved. Must be given.
Generally, an electric motor has a larger output when the size is increased, but when the installation space is limited like a spindle motor, the size and the output are also correspondingly limited. Therefore, in order to increase the output of the spindle motor, conventionally, the length of the stator and the rotor has been increased without changing the diameter of the stator and the rotor within a given spatial limit.

[0003]

However, lengthening the induction motor used as the spindle motor exposes various problems mainly relating to the structure of the motor. First, since the stator core and the rotor core of the induction motor are both laminated bodies of electromagnetic steel sheets, the bending in the radial direction is likely to occur by increasing the length, that is, the number of layers. In order to fit and fix the stator core into the sleeve portion of the motor housing, the outer peripheral surface of the core is smoothly ground after laminating the electromagnetic steel plates, but at this time, the bending makes it difficult to perform accurate machining. Further, in the rotor core, a slight bending particularly at high speed induces rotation unevenness and vibration, which deteriorates the performance of the electric motor. Further, in recent years, a rotor core generally has a structure including an aluminum die-cast secondary conductor integrally formed after lamination of electromagnetic steel sheets and an end ring, but when performing die casting on a long rotor core, There is a danger that the molten aluminum flow in the secondary conductor slot will become poor and conductor defects will occur due to the formation of cavities after solidification. This is particularly remarkable when the secondary conductor slot twisted in the circumferential direction is provided in order to avoid a torque abnormality at the time of starting.

The present invention has been devised and devised to solve the above problems in the prior art.
The purpose is to provide an induction motor that can be used as a high-power built-in spindle motor that can lengthen the stator and rotor without impairing the formability during grinding and die casting and the bending rigidity of the molded product. Especially.

[0005]

In order to achieve the above object, the present invention provides a plurality of secondary conductors extending in the axial direction and an end ring for interconnecting the secondary conductors at both ends in the axial direction with aluminum. The rotor core is integrally formed by die-casting on a laminated body of electromagnetic steel sheets, and is fixed to a rotating shaft. A plurality of primary windings are wound around the laminated body of electromagnetic steel sheets to form a rotor core through a gap. In an induction motor including a stator core that is surrounded and fixed to a stationary housing,
A plurality of the rotor cores are arranged side by side in the axial direction and fixed to the rotary shaft, and a plurality of the stator cores surround each of the plurality of rotor cores and are arranged side by side in the axial direction and fixed to the stationary housing. A multi-stage induction motor is provided.

[0006]

Operation: One rotor core is formed to have a length that does not cause defective flow of molten metal during aluminum die casting. At the same time, one stator core is formed to have a length that does not cause bending to the extent that it becomes unworkable during cutting of the outer peripheral surface. Then, the lengths of one rotor core and one stator core are set to be substantially the same. When a plurality of rotor cores and stator cores each having a length set in this way are arranged side by side in the axial direction and are fixed to the rotary shaft and the stationary housing, respectively, the torque extracted from the rotary shaft is substantially the same as the torque produced by one rotor core. Double the number of parallel installations.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail with reference to the preferred embodiments shown in the accompanying drawings. In each drawing, the same reference numeral is given to the same component. Referring to FIG. 1, a two-stage induction motor 1 according to a first embodiment of the present invention.
0 is shown in cross section. The induction motor 10 includes a rotating shaft 12, two rotor cores 14 that are fitted and fixed to the rotating shaft 12 at predetermined intervals in the axial direction, and a plurality of secondary conductors 16 formed in each rotor core 14. , And surrounding each rotor core 14 and fitted and fixed in the sleeve portion 20 of the motor housing 2
The stator includes one stator core 22 and a plurality of primary windings 24 wound around each stator core 22. The rotating shaft 12 is rotatably supported by the motor housing 18 via a pair of bearings 26, and outputs the torque of the rotor rotating in the stator. This induction motor 10
When using as a built-in spindle motor, the rotary shaft 12 is the main shaft of the machine tool and the sleeve 2
0 is integrated with the spindle housing.

The rotor core 14 is formed by laminating a large number of silicon steel plates punched with a slot for a secondary conductor and a center hole for a rotary shaft, and is integrally formed by die-casting aluminum as a secondary conductor 16 in a predetermined die. Fixed. As a result, the rotor core 14 has a plurality of axially extending two
The secondary conductor 16 and an end ring 28 made of aluminum that connects the secondary conductors 16 at both ends in the axial direction of the rotor core 14 are integrally formed. In this way, the rotor core 14 integrally formed with the secondary conductor 16 and the end ring 28 is fixed to the rotating shaft 12 by shrink fitting, for example. Similarly, the stator core 22 is formed by stacking a large number of silicon steel plates punched with slots for primary windings and center holes for rotors.
After winding 4, the varnish is impregnated and fixed integrally. The outer peripheral surface of the stator core 22 is smoothly ground prior to the winding step so as to come into close contact with the inner peripheral surface of the sleeve portion 20. The stator core 22 having the primary winding 24 wound in this manner is fitted into the sleeve portion 2 by shrink fitting, for example.
Fixed at 0. Each of the rotor core 14 and the stator core 22 is formed to have a length within a range that is allowable in the conventional one-stage induction motor (that is, the above-mentioned problems do not occur).

As described above, in the induction motor 10 according to the first embodiment of the present invention, the two rotor cores 14 and the stator cores 22 each having a well-known structure are arranged side by side at a predetermined mutual interval in the axial direction, and the rotary shaft 12 and It is fixed to the sleeve portion 20. Therefore, the induction motor 10 extracts from the rotor a torque that is approximately twice the torque generated by one rotor core 14 without impairing the moldability of the rotor core 14 and the stator core 22 during die casting and grinding, and the flexural rigidity of the molded product. You can

FIG. 2 is a sectional view showing a two-stage induction motor 30 according to a second embodiment of the present invention. The induction motor 30 is
The rotor core 14 and the stator core 22 having the same structure as those in the first embodiment are arranged side by side in the axial direction with no space therebetween and fixed to the rotary shaft 12 and the sleeve portion 20. Therefore, the two stator cores 22 are superposed on each other so that the primary winding slots of the two stator cores 22 are concentric in the axial direction using a predetermined jig after the outer peripheral surface is ground and the primary winding slots are continuous. A plurality of primary windings 24 are wound around. It is clear that the induction motor 30 has the same effect as that of the induction motor 10 according to the first embodiment. Further, by adopting such a configuration of adjacent stages, it is possible to increase the ratio of the output torque to the entire length of the motor. You can

Induction motors 10 and 3 according to the above embodiments
In 0, the rigidity of the rotor and the stator after assembly depends on the strength of the rotary shaft 12 and the sleeve portion 20, so it is necessary to select an appropriate material and thickness (diameter) of the rotary shaft 12 and the sleeve portion 20 during manufacturing. There is. At the same time, the bearing 26 is required to have an appropriate capacity. If the above-mentioned various conditions regarding strength are satisfied, the induction motor according to the present invention can have a multi-stage structure of three or more stages without being limited to the above embodiment, and further higher output is possible.

[0012]

As is apparent from the above description, according to the present invention, a plurality of rotor cores are arranged side by side in the axial direction to be fixed to the rotating shaft, and the stator core is surrounded by each of the plurality of rotor cores. A plurality of rotor cores and stator cores are arranged side by side in the axial direction and fixed to a stationary housing, so that the length of one rotor core and stator core is set to a length that does not impair the formability during die casting and grinding, and the flexural rigidity of the molded product. After the setting, the torque generating resource portions of the stator and the rotor can be lengthened. Therefore, an induction motor that can be used as a built-in spindle motor can be highly reliable and have a high output, which has the effect of contributing to the improvement of the machine tool capability.

[Brief description of drawings]

FIG. 1 is a sectional view of an induction motor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an induction motor according to a second embodiment of the present invention.

[Explanation of symbols]

 12 ... Rotating shaft 14 ... Rotor core 16 ... Secondary conductor 18 ... Motor housing 20 ... Sleeve part 22 ... Stator core 24 ... Primary winding 26 ... Bearing 28 ... End ring

Claims (1)

[Claims] 1. A plurality of secondary conductors extending in the axial direction and an end ring that interconnects the secondary conductors at both ends in the axial direction are integrally formed on a laminate of electromagnetic steel sheets by die casting of aluminum, A rotor core fixed to a rotating shaft, and a plurality of primary windings wound around a laminated body of electromagnetic steel sheets,
In an induction motor, comprising: a stator core that surrounds the rotor core via a gap and is fixed to a stationary housing; a plurality of rotor cores are arranged side by side in the axial direction and are fixed to the rotating shaft; A multi-stage induction motor characterized in that each of the plurality of rotor cores is surrounded, and a plurality of the rotor cores are arranged side by side in the axial direction and fixed to the stationary housing.