Commutator for an electrical machine, armature assembly and electrical machine with an armature assembly

Abstract

Commutator (15) for an electrical machine (100), in particular for a DC motor, comprising an insulating body (20) and a plurality of commutator segments (21) secured in the insulating body (20) and arranged side by side in the circumferential direction with a gap spacing, each of which carries a connecting hook (22) at one segment end for connecting an armature winding (13), wherein the insulating body (20) has, on the side of the commutator segments (21) facing away from the connecting hooks (22), a region (25) which is conical with respect to the longitudinal axis of the insulating body (20) and has a preferably constant slope, the diameter of which decreases in the direction towards the side facing away from the connecting hooks (22), wherein longitudinal slots (31) are formed between the commutator segments (21) in the circumferential direction, such that the longitudinal slots (31) extend into the conical region (25), and such that the commutator segments (21) are guided through the longitudinal slots (31) are formed from a sleeve-shaped body,so that the commutator segments (21) are separated from one another by the longitudinal slots (31), the transition region between the conical region (25) and the cylindrical region (30) being provided with a rounding (29), and the commutator segments (21) adjoining the cylindrical region (30) in the longitudinal direction without a gap.

Description

State of the art

[0001] The invention relates to a commutator for an electrical machine according to the preamble of claim 1. Furthermore, the invention relates to an armature assembly with a commutator according to the invention and to an electrical machine with an armature assembly.

[0002] A commutator according to the preamble of claim 1 is known from DE 100 34 517 A1. The commutator shown therein has, on the side of the insulating body facing away from the connecting hook, a conical region relative to the longitudinal axis of the insulating body, over which the carbon brushes can be moved radially outward during assembly of the commutator. This enables particularly simple assembly of the commutator in an electric motor.

[0003] Another commutator is known from DE 10 2010 028 666 A1, issued by the applicant. Such a commutator supplies current to the windings of an armature assembly by means of carbon brushes that rest against the commutator segments. The carbon brushes, in turn, are typically attached to a brush holder that is fixedly arranged in a housing that houses the electric motor. To install the commutator, which is a component of the armature assembly, the latter is inserted into the housing, whereby the carbon brushes come into operative connection with the commutator segments. The carbon brushes are spring-loaded against the commutator segments.This makes it necessary for the carbon brushes to be pushed radially outwards against the spring force of the spring elements when inserting the armature assembly axially to prevent the carbon brushes from striking the commutator with their sides, which would prevent further insertion of the armature assembly and could also damage the carbon brushes. Therefore, it is common practice in the state of the art to slide a conical additional body onto the armature shaft of the armature assembly. When the armature assembly is inserted, this additional body comes into active contact with the carbon brushes and pushes them radially outwards until they reach the area of ​​the commutator bars. The disadvantages of this are that, on the one hand, the separate additional body increases the construction and assembly effort, and on the other hand, it must be ensured that the additional body does not impair the functionality of the electric motor during operation.Therefore, the additional body must either be fixed in place on the armature shaft, or it must be ensured by the design that an axial movement of the additional body during operation does not lead to any impairment of the function of the electric motor.

[0004] DE 101 15 601 C1 discloses another commutator in which carbon elements adjoin the commutator segments in the axial direction, with the commutator segments and the carbon elements being arranged in a plastic insulating body. The commutator segments are separated from one another in the circumferential direction by the plastic of the insulating body. Longitudinal slots extending from one end face of the carbon elements (on the side facing away from the commutator segments) into the area of ​​the insulating body serve to electrically separate the carbon elements. On the side facing away from the commutator segments, the insulating body has a radially circumferential flange that projects slightly beyond the end face of the carbon elements in the axial direction.

[0005] US 3,129,350 shows a commutator arranged on a rotor shaft, wherein a conical contact surface is arranged from the commutator to the rotor body, on which the winding head of the rotor winding rests radially.

[0006] DE 602 11 780 T2 and DE 33 44 305 A1 show the production of a commutator in which a metal sleeve is applied to an insulating base body, and then axial slots are sawn into the metal sleeve in order to form the commutator segments which are insulated from one another. Disclosure of the invention

[0007] Based on the prior art described, the object of the invention is to develop a commutator for an electrical machine according to the preamble of claim 1 in such a way that a separate additional body for radially moving the carbon brushes during assembly of the armature assembly can be dispensed with. This object is achieved according to the invention in a commutator for an electrical machine with the features of claim 1 in that the insulating body, on which the commutator bars are arranged, has, on the side of the commutator bars facing away from the connecting hooks, a region which is conical in relation to the longitudinal axis of the insulating body and has a preferably constant bevel, the diameter of which decreases in the direction towards the side facing away from the connecting hooks. In other words, this means that, in contrast to the prior art, a separate element (additional body) for spreading orradial separation of the carbon brushes can be dispensed with, and that this function is fulfilled by the insulating body on which the commutator bars are arranged or fastened, in that the insulating body has a conically shaped area which ensures the spreading or radially outward movement of the carbon brushes during assembly of the armature assembly. Such a conical area also has the advantage that it can be formed integrally onto the insulating body, with the insulating body usually being formed using an injection molding process, so that the manufacturing effort in relation to the conical area is minimized. In particular, there is no additional assembly effort, and no design measures need to be taken which would otherwise be necessary with an additional body for spreading the carbon brushes which is arranged so as to be movable axially on the armature shaft.

[0008] Further optimization or minimization of the load on the carbon brushes is achieved if, according to the invention, the transition area between the conical and cylindrical regions is provided with a rounded section. This minimizes, in particular, linear loads on the surfaces of the carbon brushes that are in contact with the commutator segments.

[0009] A further optimization or protection of the carbon brushes during assembly according to the invention is achieved if the commutator bars are connected to the cylindrical area of ​​the insulating body without a gap in the longitudinal direction.

[0010] Advantageous developments of the commutator according to the invention for an electrical machine are set forth in the subclaims. All combinations of at least two of the features disclosed in the claims, the description, and / or the figures fall within the scope of the invention.

[0011] To prevent damage to the side surfaces of the carbon brushes and, furthermore, to minimize the loads on the carbon brushes when they impact the conical area of ​​the insulating body from the side, it is preferably provided that the insulating body has a through-bore for an armature shaft, and that the conical area extends radially at least almost to the through-bore. This prevents transverse forces or transverse loads on the carbon brushes, particularly when the side surfaces of the carbon brushes on the side facing the armature shaft are provided with a corresponding bevel or chamfer, thus also preventing damage or pre-damage.

[0012] In order to enable a smooth transition from the conical area of ​​the insulating body to the commutator bars, in which in particular no damage can occur to the surfaces of the carbon brushes that are in contact with the commutator bars, it is further proposed that the conical area, on the side facing the bar ends with the connecting hooks, transitions into a cylindrical area whose diameter corresponds to the diameter of the commutator bars arranged on the insulating body.

[0013] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings.

[0014] This shows in: Fig. 1 an armature assembly using a commutator according to the invention in a side view and Fig. 2 one in the armature assembly according to Fig. 1 used commutator in a perspective single view.

[0015] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0016] In the Fig. 1 shows a part of an electrical machine 100 in the form of a DC motor, as it is in particular a component of a comfort drive in a motor vehicle, in particular a window lift drive, a seat adjustment drive, a sunroof drive or the like.

[0017] The electric machine 100 comprises an armature assembly 10 with an armature shaft 11. The armature shaft 11 carries an armature or rotor body 12 with an armature winding 13 with multiple wire windings inserted into slots in the rotor body 12. The wire windings of the armature winding 13 are electrically connected to a commutator 15 according to the invention. The commutator 15 serves to supply current to the individual wire windings of the armature winding 13 and, for this purpose, interacts with carbon brushes 16, which act on the circumference of the commutator 15 and are pressed against the commutator 15 by spring force. For this purpose, the carbon brushes 16 are arranged in a stationary manner on a brush holder in a manner known per se and therefore not further shown. The brush holder has holders 17 for the carbon brushes 16, in which the carbon brushes 16 are arranged so as to be axially displaceable in the direction of the double arrow 18 by means of spring force.

[0018] As best seen from a summary of the Fig. 1 and Fig. 2, the commutator 15, which is arranged in a rotationally fixed manner on the armature shaft 11, comprises an insulating body 20 made of plastic by injection molding, on the outer circumference of which a plurality of commutator segments 21 are arranged, which are fixed in the insulating body 20 and arranged next to one another in the circumferential direction with a gap spacing. The commutator segments 21, which are usually made of copper, have connection hooks 22 at the segment ends on the side facing the rotor body 12, to which connection hooks the individual wire windings of the armature winding 13 are fastened, in particular soldered or welded.

[0019] According to the invention, the insulating body 20 has, on the side facing away from the rotor body 12, a region 25 which is conically formed with respect to the longitudinal axis of the insulating body 20 or the armature shaft 11. As can be seen in particular from the Fig. 2, the insulating body 20 furthermore has a through-bore 26 in which the armature shaft 11 is arranged; the insulating body 20 is thus sleeve-shaped.

[0020] The diameter of the conical region 25 decreases in the direction towards the side facing away from the rotor body 12 up to a front end face 27, at which the conical region 25 has an (outer) diameter which almost corresponds to the diameter of the armature shaft 11, ie the conical region 25 extends radially almost up to the armature shaft 11.

[0021] The conical region 25 has a radially encircling, conical spreading surface 28, which in the illustrated embodiment is formed with a constant slope. On the side facing the rotor body 12, the region 25 transitions into a cylindrical region 30 via a region provided with a rounded portion 29. The outer diameter of the cylindrical region 30 corresponds to the outer diameter of the commutator 15 in the region of the commutator segments 21. Furthermore, the commutator segments 21 adjoin the cylindrical region 30 of the insulating body 20 directly, i.e., without a gap.

[0022] The production of such an insulating body 20 with the commutator segments 21 is carried out in practice by inserting a sleeve-shaped component, from which the commutator segments 21 are formed, into an injection mold for the insulating body 20 and the insulating body 20 is formed by injecting liquefied plastic under high pressure into the injection mold. Subsequently, the individual commutator segments 21 are formed from the sleeve-shaped body by forming longitudinal slots 31, wherein the longitudinal slots 31, as shown in the Fig. 2, extend beyond the cylindrical region 30 into the conical region 25.

[0023] During assembly of the armature assembly 10 in the electrical machine 100, the armature assembly 10 is pushed into the electrical machine 100 in the direction of arrow 32. The carbon brushes 16, which are loaded by the spring force and pressed towards the armature shaft 11, come into operative connection with the conical region 25 of the insulating body 20 and, upon movement of the armature assembly 10 in the direction of arrow 32, are pressed radially outwards, sliding along the spreading surface 28. The carbon brushes 16 then move over the conical region 25, the rounding 29 and the cylindrical region 30 into the region of the commutator segments 21, as shown in the Fig. 1, where the axial end position of the armature assembly 10 in relation to the commutator carbons 16 is shown.

[0024] The armature assembly 10 described so far and the electric machine 100 can be modified in a variety of ways without deviating from the inventive concept. This consists in the formation of a conical region 25 on the insulating body 20, which serves to press the carbon brushes 16, which are loaded radially inward by spring force, radially outward during assembly of the armature assembly 10 until they are operatively connected to the commutator segments 21.

Claims

[1] A commutator (15) for an electrical machine (100), in particular for a DC motor, comprising an insulating body (20) and a plurality of commutator segments (21) secured in the insulating body (20) and arranged side by side in the circumferential direction with a gap spacing therebetween, each segment carrying a connecting hook (22) at one segment end for connecting an armature winding (13), wherein the insulating body (20) has, on the side of the commutator segments (21) facing away from the connecting hooks (22), a region (25) which is conical with respect to the longitudinal axis of the insulating body (20) and has a preferably constant slope, the diameter of which decreases in the direction towards the side facing away from the connecting hooks (22), wherein longitudinal slots (31) are formed between the commutator segments (21) in the circumferential direction, such that the longitudinal slots (31) extend into the conical region (25),and that the commutator laminations (21) are formed from a sleeve-shaped body by the longitudinal slots (31), so that the commutator laminations (21) are separated from one another by the longitudinal slots (31), wherein the transition region between the conical region (25) and the cylindrical region (30) is provided with a rounding (29), and the commutator laminations (21) adjoin the cylindrical region (30) in the longitudinal direction without a gap. [2] Commutator according to claim 1, characterized by that the insulating body (20) has a through-bore (26) for an armature shaft (11), and that the conical region (25) extends radially at least almost to the through-bore (26). [3] Commutator according to claim 1 or 2, characterized bythat the conical region (25) on the side facing the connecting hooks (22) merges into a cylindrical region (30) whose diameter corresponds to the diameter of the commutator segments (21) arranged on the insulating body (20). [4] Commutator according to one of claims 1 to 3, characterized by that the conical region (25) is formed integrally with the insulating body (20) - in particular made of plastic - and is preferably produced by injection molding. [5] An armature assembly (10) comprising an armature shaft (11) with a rotor body (12) connected to the armature shaft (11) in a rotationally fixed manner, with armature windings (13), and a commutator (15) arranged on the armature shaft (11) according to one of claims 1 to 4. [6] Electrical machine (100), in particular a DC motor, with an armature assembly (10) according to claim 5 and an arrangement of carbon brushes (16) which are arranged to be radially movable with respect to the longitudinal axis of the armature shaft (11).

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