POSITIVELY BALANCING AN ARMATURE

Abstract

A method for producing a positively balanceable internal armature to be used in an electric motor, in particular a direct-current electric motor, which makes it possible that the structural group is configured such that a balancing of the internal armature can take place with little technical effort. A manufacturing apparatus which is arranged to execute the proposed method or which can be operated by the proposed method. Further, an internal armature to be used in an electric motor as well as to the electric motor itself. Further, a computer program product is proposed, having control commands which implement the proposed method or operate the proposed manufacturing apparatus.

Claims

1. A method for producing a positively balanceable internal armature to be used in an electric motor, comprising: supplying a rotor sheet pack; overmolding the supplied rotor sheet pack with a thermoplastic, and configuring the plastic overmolding such that on at least one end face of the rotor sheet pack there are shaped recesses for receiving balancing elements.

2. The method according to claim 1, wherein the shaping of recesses is effected during the overmolding.

3. The method according to claim 1, wherein the shaping of recesses is effected subsequently to the overmolding.

4. The method according to claim 3, wherein the shaping of the recesses is effected by drilling.

5. The method according to claim 1, wherein the shaping of the recesses is effected in dependence on a dimension of balancing elements to be incorporated.

6. The method according to claim 1, wherein on at least one end face of the rotor sheet pack there is shaped a disk-shaped contour into which the recesses are incorporated.

7. The method according to claim 1, wherein the recesses are disposed coaxially to the axis of the rotor sheet pack.

8. The method according to claim 1, wherein there is effected a balancing of the overmolded rotor sheet pack such that balancing elements are incorporated into the recesses provided for this purpose.

9. The method according to claim 8, wherein for balancing there are employed spheres as balancing elements.

10. The method according to claim 8, wherein the balancing elements are fixed in the plastic overmolding.

11. The method according to claim 10, wherein the fixing comprises a heat-staking of the balancing elements.

12. A manufacturing apparatus for producing a positively balanceable internal armature to be used in an electric motor, comprising: a manufacturing unit arranged for supplying a rotor sheet pack; an overmolding unit arranged for overmolding the supplied rotor sheet pack with a thermoplastic, characterized in that the manufacturing apparatus is arranged for configuring the plastic overmolding such that on at least one end face of the rotor sheet pack there can be shaped recesses for receiving balancing elements.

13. An internal armature to be used in an electric motor, comprising: a rotor sheet pack, wherein the rotor sheet pack is overmolded with a thermoplastic, wherein on at least one end face of the rotor sheet pack there are shaped recesses for receiving balancing elements in the thermoplastic.

Description

BRIEF DESCRIPTION

[0036] Further advantageous configurations are explained in more detail with reference to the enclosed figures. There are shown:

[0037] FIG. 1: a rotor sheet pack as it is used according to an aspect of the present invention, in an isometric view;

[0038] FIG. 2: a rotor sheet pack which is equipped with permanent magnets, in an end-face view, as it is used according to an aspect of the present invention;

[0039] FIG. 3: an equipped rotor sheet pack with injection-molded geometry for receiving balancing spheres according to an aspect of the present invention;

[0040] FIG. 4: an equipped and overmolded rotor sheet pack, in a longitudinal section according to an aspect of the present invention;

[0041] FIG. 5: an air releasing channel for a recess according to an aspect of the present invention;

[0042] FIG. 6: a balanced rotor with pressed-in balancing sphere according to an aspect of the present invention; and

[0043] FIG. 7: a schematic flowchart of a method for producing a positively balanceable internal armature according to an aspect of the present invention.

DETAILED DESCRIPTION

[0044] FIG. 1 shows a rotor sheet pack equipped with permanent magnets, in the present case with rectangular magnets which are inserted on the end face side. Therefore, in the present rotor sheet pack there is drawn the end face on the left and on the right. The rotor sheet pack serves as an initial part for overmolding and configuring the plastic overmolding such that on one or on both end faces of the rotor sheet pack there are shaped recesses for receiving balancing elements. Here, it is particularly advantageous that the rotor sheet pack shown in FIG. 1 can be configured as a conventional rotor sheet pack.

[0045] FIG. 2 shows on the left side a rotor sheet pack equipped with permanent magnets, which is explained more closely in a detail view according to the section X. In particular the detail on the right side shows, by means of the drawn lines, the longitudinal openings through the rotor sheet pack, into which the plastic is injected later. The injecting is, according to an aspect of the present invention, the overmolding of the supplied rotor sheet pack.

[0046] FIG. 3 shows the already overmolded rotor sheet pack and shows in particular on the right side the end face of the equipped rotor sheet pack with the plastic overmolding. The plastic overmolding comprises on the end face side the injection-molded geometry for receiving the balancing spheres. As can be seen in FIG. 3, it is possible to configure the recesses geometrically such that spheres can be employed as balancing elements. For balancing, there can be incorporated individual balancing elements into the recesses, as they are shown on the right side.

[0047] FIG. 4 shows in a longitudinal section an equipped rotor sheet pack which is already overmolded, in this case with thermoplastic. Here, the present invention is directed to thermoplastic as an overmolding, but merely according to one aspect. On the right side in FIG. 4 in the detailed view Y there is shown a depression for urging air out of the bore upon pressing in the balancing sphere. Therefore, in the recess there is provided a depression which is suitable to allow air to escape, which escapes upon a pressing in of the balancing element or generally upon incorporation of the balancing element. The equipped rotor sheet pack according to FIGS. 3 and 4 can in general also be referred to as an internal armature.

[0048] FIG. 5 shows in a detailed view an air releasing channel and a corresponding depression for allowing air to escape from the bore when the balancing sphere is pressed in.

[0049] FIG. 6 shows a balanced rotor or an internal armature, with pressed-in balancing sphere. Depending on the imbalance to be compensated it can also be necessary to press spheres into several bores. Therefore, in the present FIG. 6 on the left side, i.e. the end face, there are drawn several recesses which are supplied by means of the plastic overmolding.

[0050] While on account of the selected perspectives always merely one end face is shown, it is also possible that respective recesses are provided, for example, also on the end face which is concealed in FIG. 6. Therefore, it is also possible to configure the plastic overmolding such that on two end faces, i.e. both end faces, of the rotor sheet pack there are shaped recesses for receiving balancing elements.

[0051] FIG. 7 shows in a schematic flowchart a method for producing a positively balanceable internal armature to be used in an electric motor, comprising the steps of supplying 100 a rotor sheet pack, overmolding 101 the supplied rotor sheet pack with a thermoplastic, and configuring 102 the plastic overmolding such that on at least one end face of the rotor sheet pack there are shaped recesses for receiving balancing elements. In further optional method steps there is effected a balancing 103 of the internal armature and a fixation 104 of the balancing elements in the plastic overmolding. The person skilled in the art here recognizes that he can execute individual method steps iteratively and/or in a different order.

[0052] Therefore, a skilful usage of the plastic overmolding of a rotor of an electric machine is proposed, in such a way that the overmolding on its end face side is developed such that suitable balancing weights can be received. The balancing weights received in the corresponding openings, preferably spheres which are pressed into circular bores, can subsequently be form-fittingly secured against detaching by heat-staking the plastic. Therefore, the plastic overmolding is heat-staked such that, for example, a metal sphere is fixed in the recess.

[0053] Upon overmolding the rotor sheet pack, which is equipped with the permanent magnets, with the thermoplastic, in the specific application case there is also injection-molded a cylindrical disk-shaped contour on both end faces of the sheet pack. This contour has a row of openings disposed coaxially to the axis of the sheet pack. In the present case, these are simple, circular openings or bores. By means of these bores the finished assembled rotor can be balanced after the overmolded sheet pack was mounted to the motor shaft. The balancing occurs positively by balancing weights, in the present case customary steel spheres, being forced according to the imbalance to be removed into the bore or bores relevant for this purpose. Optionally, the forged-in spheres can also be relatively simply and efficiently secured against loss by hot-stamping or heat-staking.

[0054] The already available overmolding of the rotor with plastic for fixing the permanent magnets inserted in the rotor sheet pack is used, according to the invention, for injection-molding on both end faces of the rotor a geometry for receiving the balancing elements. The balancing is therefore positive. The balancing elements can be simple, very cost-efficient metal spheres. By heat-staking or hot-stamping the balancing elements can additionally be form-fittingly secured against loss in a very simple and efficient fashion. The method thus works cleanly and produces no soiling upon manufacturing or assemblage. This is an essential advantage compared with negative balancing, upon which material is removed. The proposed method is therefore suitable, for example, for a with high demands on cleanness, because no contaminations are caused by the process.