Insulator

An insulator includes a main body portion for axially covering one side face of a core that includes a plurality of teeth portions extending in a radial direction, and a plurality of extending portions extending from the main body portion in an axis direction of the core and covering a plurality of slots respectively formed between the teeth portions adjacent to each other. An extending length of one of the extending portions from the main body portion is specified longer than other extending portions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2005-184072, filed on Jun. 23, 2005, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention generally relates to an insulator. More particularly, this invention pertains to an insulator attached to a core of an electric motor, and the like.

BACKGROUND

Various kinds of insulators attached to a core of an electric motor, and the like, have been proposed. For example, an insulator disclosed in JP2003-61287A is made of insulating resin material and includes a main body portion and multiple extending portions. The main body portion axially covers one side face of a core that includes multiple teeth portions extending in a radial direction. The extending portions extend from the main body portion in parallel with an axis of the core so as to cover multiple slots that are formed respectively between the teeth portions adjacent to each other. A pair of such insulators are attached axially to the core from both sides respectively, for mainly ensuring insulation between the core and a winding wire.

The core of the electric motor, and the like has a complicated structure of multiple teeth portions (or multiple slots), which may cause difficulty in attaching the resin-molded insulator to the core. This is because all of the multiple extending portions that may slightly vary in shape are required to make simultaneously contact with the slots respectively for positioning when the insulator is assembled on the core.

Thus, a need exists for an insulator that can provide improved assembly performance relative to a core.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an insulator includes a main body portion for axially covering one side face of a core that includes a plurality of teeth portions extending in a radial direction, and a plurality of extending portions extending from the main body portion in an axis direction of the core and covering a plurality of slots respectively formed between the teeth portions adjacent to each other. An extending length of one of the extending portions from the main body portion is specified longer than other extending portions.

DETAILED DESCRIPTION

An embodiment of the present invention, employed in a stator of a brushless motor, is explained with reference to the attached drawings.FIG. 2Ais a plan view drawing andFIG. 2Bis a side view drawing respectively, of a stator10. The stator10includes a core11and a pair of insulators12that are made of insulating material and that are attached to the core11.

The core11, which is made of a steel plate lamination layer for example, includes a core main body11ahaving a cylindrical shape, and multiple (twelve, for example) teeth portions11bextending radially in an inward direction from an inner face of the core main body11a.The multiple teeth portions11bare integrally connected to each other by means of the core main body11aand arranged at equal spaces in a circumferential direction. In addition, multiple (twelve, for example) slots11care formed respectively between the teeth portions11badjacent to each other.

FIGS. 1A to 1Care a plan view, a side view, and a partial perspective view respectively of each insulator12. Each insulator12is molded by insulating resin material (for example, aromatic nylon). The insulator12includes a main body portion21and multiple (twelve, for example) extending portions22extending from the main body portion21in an axis direction of the core11. InFIG. 1B, only six of the extending portions22are shown as the other six of the extending portions22are arranged therebehind.

The main body portion21integrally includes an annular portion21ahaving substantially the same inner diameter as that of the core main body11a,and multiple projecting portions21bextending radially in an inward direction from an inner face of the annular portion21aso as to correspond to the teeth portions11b.The main body portion21covers axially one side face of the core11.

Each extending portion22is molded in a cylindrical shape so as to extend along a wall face of the slot11cin the axis direction of the core11. A radial inner side of the extending portion22is open across a full length thereof in an axial direction. The multiple extending portions22respectively cover corresponding multiple slots11c.

As shown inFIG. 1B, the multiple extending portions22are constituted by four types of extending portions22a,22b,22c,and22dhaving different extending lengths from each other from the main body portion21. Precisely, the extending portions22a,22b,22c,and22dhave extending lengths L1, L2, L3, and L4, (L1>L2>L3>L4) respectively. As a result, the multiple extending portions22are divided into groups, each of which is constituted by three extending portions having the same extending length from the main body portion21(i.e. three extending portions22a,three extending portions22b,three extending portions22c,and three extending portions22d). In addition, the extending portions22in the same extending length in each group are arranged at equal spaces in a circumferential direction as shown inFIG. 1. The multiple extending portions22are formed in such a way that extending lengths thereof are not equal to each other and are different from each other by a predetermined length.

Further, as shown inFIG. 1C, a chamfering portion23is formed on an end portion of each extending portion22so that the extending length of each extending portion22from the main body portion21is shorter on an inner circumferential side than an outer circumferential side.

Next, an assembly operation, in case of attaching the insulator12to the core11, is explained with reference toFIGS. 3A to 3D. InFIGS. 3A to 3D, only one of the insulators12is only shown in order to simplify explanations. An assembly operation for the other insulators12is the same and thus the explanation thereof is omitted.

As shown inFIG. 3A, in the cases where the insulator12is moved towards the core11along the axis of the core11, first, three extending portions22ahaving the longest extending length L1make contact with the corresponding slots11cof the core11for positioning. Then, when the insulator12is further moved towards the core11in this state, the extending portions22aare inserted into the corresponding slots11cwhile three extending portions22bhaving the second longest extending length L2are making contact with corresponding slots11cfor positioning as shown inFIG. 3B.

When the insulator12is still further moved towards the core11, in this state, the extending portions22aand22bare inserted into the corresponding slots11cwhile three extending portions22c,having the third longest extending length L3, are making contact with the corresponding slots11cfor positioning as shown inFIG. 3C. When the insulator12is still further moved towards the core11, the extending portions22ato22care inserted into the corresponding slots11cwhile three extending portions22d,having the shortest extending length L4, are making contact with the corresponding slots11cfor positioning. Finally, all extending portions22ato22dare inserted into the corresponding slots11calong with the further movement of the insulator12towards the core11, which leads to completion of assembly operation of the insulator12relative to the core11as shown inFIG. 3D.

According to the aforementioned embodiment, the following effects can be obtained. When the insulator12is attached to the core11, the multiple extending portions22(i.e.22ato22d,precisely) make sequentially contact with the corresponding slots11cfor positioning in the order of longest to shortest of the extending length from the main body portion21. Accordingly, all of the extending portions22are not required to make simultaneously contact with the corresponding slots11cfor positioning when the insulator12is assembled on the core11. As a result, the assembly performance may be improved.

Further, according to the aforementioned embodiment, the insulator12is assembled on the core11in such a manner that three extending portions22afirst make contact with the corresponding slots11cfor positioning. In this case, so-called statically determinate condition in a mechanical view is satisfied. The insulator12can be assembled on the core11in a stable state.

Furthermore, according to the aforementioned embodiment, the number of extending portions22is multiples of three (i.e. twelve). Then, the extending portions22are divided into groups of; three extending portions22a,three extending portions22b,three extending portions22c,and three extending portions22dbased on the extending length from the main body portion21. The insulator12is attached to the core11so that three extending portions22a,22b,22cor22d,in the same group, make sequentially contact with the corresponding slots11cfor positioning in the order of longest to shortest of the extending length. Accordingly, the insulator12can be assembled on the core11in the statically-determinated condition in each group.

Furthermore, according to the aforementioned embodiment, the extending portions22first make contact with the corresponding slots11cfor positioning at portions where the chamfering portions23are not formed (i.e. outer circumferential side). Thus, assembly performance of the insulator12relative to the core11can be further improved.

The aforementioned embodiment can be modified as follows. That is, the chamfering portions23can only be formed on the extending portions22a,which are first to make contact with the slots11c.

Further, the number of extending portions22(and the slots11c) may be multiples of three, not limited to twelve. Alternatively, the number of extending portions22(and the slots11c) may be appropriately changed to the number except multiples of three.

Furthermore, the extending portions22except three extending portions22athat first make contact with the slots11c(i.e.22a) may have identical extending lengths to each other or have different extending lengths from each other. In this case, it is optional whether the extending portions22, except three extending portions22a,can be divided into multiple groups or not.

Furthermore, the number of extending portions22athat first make contact with the slots11cmay be equal to or more than 1 with the exception of a total number, i.e. twelve. In this case, it is optional whether the multiple extending portions can be divided into multiple groups or not.

Furthermore, the present embodiment may be employed in a rotor of a brushless motor. In this case, a core of the rotor may include multiple teeth portions extending in a radial outward direction, and an insulator may cover slots formed between the teeth portions adjacent to each other in the same way as the aforementioned embodiment.