Method of fabricating a stator structure of built-in motor

Abstract: The stator of a built-in motor must be correctly secured to the spindle head housing of a machine tool. For this purpose, the periphery of a stator core (10) which is a main portion of the stator is partly welded and is held by a mandrel or the like from the inside to grind the outer circumference (14) maintaining precision. After the mandrel and the like are removed, however, the stator core (10) may undergo deformation with the passage of time. To prevent this, a thermosetting adhesive is applied to the surface of the constituent element plates (12) of the stator core (10) to bond them together, or the constituent element plates (12) are provided with a protuberance (22) as the outer circumference (14) is welded to bond them together, or a serration bar (26) is forcibly inserted in a hole (24) of the element plates (12) instead of providing the protuberance (22) to bond them together.

Description: The present invention relates to a stator structure of a built-in motor to be incorporated into the spindle or the like of a machine tool. A built-in type spindle motor for driving the spindle of a machine tool or the like has been increasingly used recently, to meet the demand for cost reductions, floor space reductions, and miniaturization. The stator of a built-in motor for such a purpose must be accurately fixed to the spindle head housing or the like of a machine tool, and a stator core is built up by superposing high-permeability steel laminations and fixedly uniting the superposed laminations by welding the circumference thereof, and then the stator core is finished to an accurate external size by grinding. As the laminations of the stator core are welded only in the circumference of the stator core, however, the laminations are not fastened together in the inside portion of the stator core, and thus the inside portion of the stator core has a low rigidity but the outside portion of the stator core has a high rigidity. Therefore, it is possible that the stator core is deformed with a lapse of time when the stator core having such a construction and held by a mandrel is ground and is removed from the mandrel after grinding. It is also possible for the stator core to be deformed during transportation or when subjected to a winding process or a varnish-impregnating process. Accordingly, an object of the present invention is to provide a stator structure having the least possibility of deformation after manufacture. BE-A-694510 discloses a method of fabricating a core-comprising the steps of applying a thermosetting adhesive to the entire surfaces of high permeability laminations in a film, superposing the laminations to form a laminated structure, and heating the laminated structure at a temperature of substantially 150°C for a predetermined time to join the laminations firmly together, and according to the present invention, such a method is characterised by grinding the outer circumference of the laminated structure-held by a mandrel to improve the accuracy of the outside diameter of the laminated structure, and in that the core is a stator core. The rigidity of the inside portion of the stator is enhanced, as well as the outside portion of the same, by the adhesive, so that the difference in the rigidity of the outside portion and the inside portion is small, and consequently, the stator is less liable to be deformed. The difference in the rigidity of the outside portion and the inside portion is reduced to the smallest extent possible, and the stator has a high rigidity. In the accompanying drawings: Figure 1 is a front view of a rotor core according to the present invention; Figure 2 is a sectional view of the rotor core taken along the line II-II Fig. 1; Referring to Figs 1 and 2, a stator core 10, i.e., the body of a stator for a motor, is built up by superposing a plurality of high-permeability steel laminations 12. The stator core 10 is fabricated by applying a thermosetting adhesive, such as an epoxy resin, to the surfaces of the high-permeability laminations 12 in a film having a thickness of several microns, superposing the high-permeability laminations 12 to form a laminated structure, compressing the laminated structure with a jig for temporary fixing, heating the laminated structure at a temperature of about 150°C for a predetermined time, to join the high-permeability laminations 12 firmly together, and grinding the outer circumference 14 of the laminated structure held by a mandrel to improve the accuracy of the outside diameter of the laminated structure. Since the component laminations 12 of the stator core 10 are coated entirely with the adhesive, the stator core 10 has a uniform rigidity, and since the component laminations 12 are joined firmly together, the stator core 10 is not deformed and the given outside diameter sized by grinding is maintained after the mandrel has removed. Accordingly, the stator core 10 can be accurately incorporated into the spindle head housing (not shown) to the like of a machine tool, for example, by a shrinkage fit, so that an accurate rotative driving of the spindle can be effected. The outer circumference of the stator core does not need the welding essential to the conventional stator core. As apparent from the foregoing description, the present invention reduces the difference in the rigidity of the outside portion and the inside portion of a stator core and enhances the general rigidity of the stator core, and thus the possibility of deformation with a lapse of time is significantly reduced when a mandrel is removed after grinding the circumference of the stator core held on the mandrel. Thus, the present invention provides a stator finished to a high accuracy and having a high reliability for a built-in motor.

Claims: A method of fabricating a core comprising the steps of applying a thermosetting adhesive to the entire surfaces of high permeability laminations (12) in a film, superposing' the laminations (12) to form a laminated structure, and heating the laminated structure at a temperature of substantially 150°C for a predetermined time to join the laminations (12) firmly together, characterised by grinding' the outer circumference (14) of the laminated structure held by a mandrel to improve the accuracy of the outside diameter of the laminated structure, and in that the core is a stator core.

Inventors: HAYASHI YOSHIYUKI FANUC MANSIO, KIMIJIMA MASAMI FANUC DAI- VIR, NAKAMURA KOSEI, NUMAI KAZUHISA FANUC DAI- VIRA, HAYASHI, YOSHIYUKI,FANUC MANSION HARIMOMI 7-310, KIMIJIMA, MASAMI,  FANUC DAI-3 VIRA-KARAMATSU, NAKAMURA, KOSEI, NUMAI, KAZUHISA,  FANUC DAI-3 VIRA-KARAMATSU, KIMIJIMA, Masami, FANUC Dai-3 Vira-karamatsu, NUMAI, Kazuhisa, FANUC Dai-3 Vira-karamatsu
Applicants: FANUC LTD, FANUC LTD.
Application year: 1990
Main classification: H02K15
IPC codes: H02K15, H02K1, B23B19