WO1994000904A1

WO1994000904A1 - Multi-stage type induction motor

Info

Publication number: WO1994000904A1
Application number: PCT/JP1993/000859
Authority: WO
Inventors: Kosei Nakamura; Yoshiyuki Hayashi; Takayuki Tamai
Original assignee: Fanuc Ltd
Priority date: 1992-06-24
Filing date: 1993-06-24
Publication date: 1994-01-06
Also published as: JPH0614506A

Abstract

A high-output induction motor having its stator and rotor elongated without affecting grinding and die-casting while maintaining the flexural rigidity of the articles. The induction motor (10) includes two rotor cores (14) fixed to a spindle with a predetermined gap in an axial direction and two stator cores (24) encompassing the rotor cores (14) and fixed to a sleeve portion (22) of housing means (20). Each rotor core (14) includes a plurality of secondary conductors (36) extending in the axial direction and a pair of end rings (38) connecting each secondary conductor (36) at both ends of the rotor core (14) in the axial direction. Each stator core (24) includes a plurality of windings (26). These rotor cores (14) and stator cores (24) are shaped longer to such an extent that die-casting and grinding are not affected and the flexural rigidity of the articles is maintained.

Description

'-' Description Multi-stage induction motor Technical field

The present invention relates to an induction motor. More specifically, the present invention relates to a multi-stage induction motor in which a plurality of stators and rotors are arranged in the axial direction. This induction motor can be used, for example, as a high-power built-in spindle motor that is directly incorporated into the main shaft of a machine tool. Background art

Induction motors are generally used advantageously as motors that require high output but do not require high-precision controllability, such as motors for driving the spindle of machine tools (so-called spindle motors). In recent years, in the field of machine tools, the speed and output of spindle motors have been increased in order to improve machining capacity.In particular, the frequency of use of the built-in spindle motor with integrated spindle has been increasing. ing. The built-in spindle motor has an advantage that the drive unit has a simple structure because its output shaft is directly connected to the main shaft of the machine tool without passing through a transmission mechanism such as a gear train. However, in general, the output of a motor increases as its size increases, but if the installation space is limited as in the case of a built-in spindle motor, the increase in size and the increase in output are also limited. Therefore, conventionally, in order to increase the output of the spindle motor, it has been necessary to increase the length of the rotor without changing the diameter of the stay and the rotor within a given space limitation. I have.

However, induction motors used as spindle motors "^{; In} order to increase the length, generally a steel core and a core made of a laminated body of magnetic steel sheets are further multilayered, so that both cores have a radius in the radial direction. In addition, in order to insert and fix the core into the sleeve of the motor housing, the outer peripheral surface of the core is smoothly ground after lamination of the electromagnetic steel plates. On the other hand, in the rotor core, slight bending, especially during high-speed rotation, induces uneven rotation and vibration, deteriorating the performance of the motor. In the case of a rotor core provided with a secondary conductor made of metal such as aluminum and an end ring, when the long rotor core is subjected to die casting, the slot in the secondary conductor slot is used. There is a risk that the molten metal flow will be poor and conductor defects will occur due to the formation of cavities after solidification, etc. This is especially true for secondary conductor slots that are inclined in the circumferential direction to avoid abnormal torque at startup. It becomes remarkable when it has.

SUMMARY OF THE INVENTION An object of the present invention is to provide an induction motor that can increase the length of a stay and a rotor without impairing the formability of grinding, die casting, and the like and the bending rigidity of a molded product, and that can achieve high output. Is to do.

Means for Solving the Problems In order to achieve the above object, the present invention provides a shaft, a laminated body of a magnetic material, a central shaft hole engaged with the shaft, and a plurality of through holes arranged around the central shaft hole and extending in the axial direction. A plurality of rotor cores which are fixed to the shaft in parallel in the axial direction, and a plurality of through holes of each rotor core and metal conductors arranged at both ends in the axial direction. Each of the rotor cores is made of a laminated body of magnetic material and has a central hole for accommodating the rotor and a plurality of slots extending in the axial direction along the peripheral surface of the central hole. Surrounding multiple stays , A stage having a core and a plurality of windings arranged in a plurality of slots of each stage core, and a plurality of stage cores of the stage being arranged in the axial direction. And a housing means for fixedly supporting the rotor at a predetermined position and rotatably supporting a shaft of a rotor.

With a rotor having a plurality of rotor cores, the work of stacking and assembling the rotor cores and the work of installing metal conductors can be performed individually. Similarly, in a stay having a plurality of stay cores, the work of stacking and assembling the stay cores and the work of installing the windings can be individually performed. Therefore, the length of each of the mouth and stay cores can be set to a length that does not impair the formability and the radial rigidity of the molded product. Moreover, by arranging a plurality of these rotor cores and stay cores in the axial direction, the output torque of the motor can be increased. BRIEF DESCRIPTION OF THE FIGURES

The above and other objects, features, and advantages of the present invention will be described based on embodiments shown in the accompanying drawings. In the attached drawing,

FIG. 1 is a sectional view of an induction motor according to a first embodiment of the present invention, and FIG. 2 is a sectional view of an induction motor according to a second embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings, FIG. 1 shows a cross-sectional view of a two-stage induction motor 10 according to a first embodiment of the present invention. The induction motor 10 includes a shaft 12, two rotor cores 14 fixed to the shaft 12 at predetermined intervals in the axial direction, and a metal conductor portion 16 provided on each rotor core 14. The rotor core 18 is fixed to the sleeve part 22 of the housing means 20 at a predetermined interval in the axial direction, and each rotor core 1 is inserted through a gap. , 4 are provided, each of which has two stay cores 24 and a plurality of windings 26 provided in each stay core 24. The shaft 12 is rotatably supported by the housing means 20 via a pair of bearings 30 outside the portion supporting the two rotor cores 14. When the induction motor 10 is used as a built-in spindle motor, the shaft 12 is integrally connected to the main shaft (not shown) of the machine tool, and the housing means 20 is integrally connected to the main shaft housing (not shown). Is done.

Each rotor core 14 is made of a laminated body of a magnetic material such as a silicon steel plate, and has one center shaft hole 32 and a plurality of through holes 34 arranged around the center shaft hole 32 and extending in the axial direction. Prepare. The laminated structure of the rotor core 14 is integrally fixed by, for example, die-casting a metal material such as aluminum in a predetermined mold. As a result, the rotor core 14 includes a plurality of secondary conductors 36 extending in the axial direction, and a pair of end rings 38 connecting the respective secondary conductors 36 at both axial ends of the rotor core 14. A metal conductor portion 16 is formed. Each rotor core 14 integrally formed with the metal conductor portion 16 in this manner is fixed to the shaft 12 by shrink fitting, for example.

Each stay core 24 is also made of a laminated body of a magnetic material such as a silicon steel plate, and has a center hole 40 for a rotor and a plurality of shafts extending in the axial direction along the peripheral surface of the center hole 40. And a winding slot 42. The laminated structure of the core 24 is fixed integrally by, for example, a varnish impregnation process after the windings 26 are arranged in the respective slots 42. The axial length of the stay core 24 is substantially the same as the axial length of the corresponding core 14. The outer peripheral surface in the radial direction of each stay core 24 is smoothly polished prior to the winding installation process so as to be in close contact with the inner peripheral surface of the sleeve portion 22. Each stator core with windings 26 installed in this way -, 24 are fixed to sleeve section 22 by shrink fitting, for example. Each of these rotor cores 14 and steering wheels 24 has a length within a range that is acceptable for a conventional single-stage induction motor (that is, does not cause the above-mentioned problems).

As described above, the induction motor 10 according to the first embodiment of the present invention is configured such that two rotor cores 14 and stay cores 24 each having a known structure are arranged side by side at predetermined mutual intervals in the axial direction. 1 and 2 fixed to the sleeve 22. Therefore, the induction motor 10 has a single rotor core 14 without impairing the formability of the rotor core 14 and the stay core 24 during die-casting and grinding and the bending rigidity of the molded product. It can output almost twice the torque of a single-stage induction motor.

FIG. 2 is a sectional view showing a two-stage induction motor 44 according to a second embodiment of the present invention. For simplicity, the same or similar components as in the first embodiment are denoted by the same reference numerals. The induction motor 44 has two mouth cores 46 and two stay cores 48 having substantially the same structure as those in the first embodiment, and are arranged side by side without any gap in the axial direction. It is configured to be fixed to the shaft 12 and the sleeve part 22. Therefore, in the induction motor 44, each rotor core 46 is fixed to the shaft 12 with the end ring 52 of the metal conductor portion 50 facing each other abutting on each other. You.

Each stay core 48 has a predetermined axial length slightly longer than the axial length of the corresponding rotor core 46. Prior to the winding setting step, each of the cores 48 is fixed to a jig in a state in which the magnetic material is laminated to the above-described predetermined length, and the outer peripheral surface in the radial direction is formed on the inner peripheral surface of the sleeve portion 2. Grinding is performed smoothly so as to be in close contact. After the outer peripheral surface is ground, each stay core 48 is concentric in the axial direction, and both winding The windings 56 are installed in a plurality of slots 54 extending over the entire length of the superimposed cores 48. Each stay core 48 and winding 56 are integrally held by the subsequent impregnation step. Each of the stay cores 48 on which the windings 56 are provided in this manner is fixed to the sleeve 22 by, for example, shrink fitting.

It is clear that the induction motor 44 has the same effect as the induction motor 10 according to the first embodiment. Furthermore, the ratio of the output torque to the total length of the motor can be increased by adopting such a configuration of each stage contact type.

In the induction motors 10 and 44 according to the above embodiments, the rigidity of the shaft and the stay after assembly depends on the strength of the shaft 12 and the sleeve 22. It is necessary to select an appropriate material and diameter or thickness for Part 22. At the same time, bearings 30 are also required to have appropriate capabilities. If these various conditions on 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-described embodiment, and can further increase the output. Becomes

Further, in each of the above-described embodiments, the configuration is described in which the rotor in which the metal conductor portion is integrally formed with the rotor core by die casting is used. However, the present invention is not limited thereto. It is also possible to use a cage-shaped mouth which is a combination of independent secondary conductor members inserted in each of the above and independent end ring members arranged at both axial ends of the rotor core. . Industrial applicability

As is evident from the above description, the present invention provides a plurality of rotor cores which are arranged side by side in the axial direction and fixed to the shaft. '-' Since a plurality of rotor cores are surrounded and fixed to the housing with a plurality of rotor cores arranged side by side in the axial direction, the lengths of the rotor core and the stay core are ground. The length of the portion that contributes to the torque generation of the electric motor can be lengthened as a whole after setting the length so as not to impair the formability in processing and die casting, and the bending rigidity of the molded product. Therefore, it is possible to increase the output of the induction motor with high structural reliability. The induction motor according to the present invention contributes to improving the performance of a machine tool, for example, by using it as a spindle motor.

Claims

'The scope of the claims

1. A shaft, comprising a laminated body of a magnetic material, a central shaft engaged with the shaft, and a plurality of through-holes arranged around the central shaft hole and extending in the axial direction. A rotor comprising: a plurality of rotor cores arranged side by side in the direction and fixed to the shaft; and a plurality of the through holes of each of the rotor cores and metal conductors disposed at both ends in the axial direction.

A center hole for accommodating the rotor, and a plurality of slots extending in the axial direction along a peripheral surface of the center hole, each of which is provided with a plurality of slots; A stage comprising: a plurality of stay cores surrounding each; and a plurality of windings disposed in the plurality of slots of each of the stay cores.

Housing means for supporting the plurality of stator cores of the stay at a predetermined position side by side in the axial direction, and rotatably supporting the shaft of the rotor;

And a multi-stage induction motor.

2. The multi-stage induction according to claim 1, wherein the plurality of opening cores are fixed to the shafts such that the metal conductors disposed at one end of each rotor core facing the axial direction are separated from each other. Electric motor.

3. The multi-stage induction according to claim 2, wherein the plurality of stay cores have substantially the same axial length as each of the surrounding mouth cores.

4. The multi-stage induction motor according to claim 2, wherein the axial end faces of the plurality of stay cores and the axial end faces of the corresponding rotor cores are substantially coplanar.

5. The plurality of mouth cores are arranged such that the metal conductors disposed at one end of each rotor core in the opposite axial direction are in contact with each other. 2. The stepped induction motor according to claim 1, which is fixed to a shaft.

6. The plurality of stator cores have a slightly larger axial length than each of the mouth cores surrounding each other, and the opposite axial end faces of the respective stator cores are mutually opposed. 6. The multi-stage induction motor according to claim 5, wherein the plurality of windings are abutted, and the plurality of windings extend continuously between the stay cores arranged in abutment.