Three-phase external rotor motor and method for mounting a stator for a three-phase external rotor motor

Abstract

A three-phase external rotor motor with a rotor (2) and a stator (1) surrounding the rotor (2) is described. The rotor (2) has permanent magnets (2a), and the stator (1) has a stack of laminations (12) with an annular cross-section, end caps (14) arranged at both ends of the stack of laminations (12), and stator windings (11) arranged in slots on a radial outer surface. According to the invention, the stator (1) has grooves (15a, 15b) on a radial inner surface, which extend in a straight line in the axial direction from one of the two end caps (14) across the stack of laminations (12) to the other end cap (14). A method for assembling a stator for a three-phase external rotor motor is also described.

Description

The invention relates to a three-phase electric motor, more particularly to an external rotor motor having the features specified in the preamble of claim 1. Such an electric motor is known from WO 2016 / 115 921 A1.In the case of three-phase external rotor motors, end caps are common, which are arranged at the two axial ends of a sheet metal stack of the stator in order to facilitate the wire guide for forming the windings of the three phases, in particular to ensure a robust production process without waste from a clean winding pattern. In order that incorrect connections are not made with the phase windings, the end caps must be positioned relative to one another in the correct rotational angle position.It is an object of the invention to show a way in which the mounting of a stator for a three-phase external rotor motor can be facilitated.This object is achieved by an external rotor motor having the features specified in claim 1 and by a method according to claim 7. Advantageous refinements of the invention are the subject matter of dependent claims.The stator of an external rotor motor according to the invention has grooves on a radial inner side, which grooves run from one of the two end caps over the sheet metal stack of the stator to the opposite end cap. During assembly, pins of a tool can engage in these grooves and thus ensure a correct positioning of the two end caps with respect to one another and a centering relative to the sheet metal stack.An advantageous further development of the invention provides that the number of slots on the inner side of the stator is an integral multiple of the number 3, and the slots are arranged uniformly distributed in the circumferential direction. In a three-phase electric motor, the windings of the individual phases are arranged in a corresponding rotational symmetry, i.e. a rotation of 120° leads to an identical configuration. If the slots reflect the rotational symmetry of the windings of the individual phases, assembly is simplified as the number of correct configurations in which pins of the tool can engage the slots increases accordingly.A further advantageous development of the invention provides that the grooves have the shape of a segment of a circle at least in the region of their base. In this way, during assembly, pins with a circular cross section can engage without problems in the grooves and position the end caps relative to one another and center them in relation to the sheet metal stack. Advantageously, a plastic deformation of the end cap can be avoided. Pins with a circular cross section are available cost-effectively for a corresponding tool. The method according to the invention can, however, also be carried out with pins of different shape and the grooves can be shaped to fit it.Further details and advantages of the invention are explained on an exemplary embodiment with reference to the attached drawings.Identical and corresponding components are provided with corresponding reference numerals in the different drawings. It shows. FIG. 1 shows a sectional view of an exemplary embodiment of an electric motor according to the invention; FIG. 2 shows the stator of the electric motor shown in FIG. 1 ; FIG. 3 shows a detailed view of FIG. 2 ; and FIG. 4 shows a schematic illustration of the mounting of components of the stator.FIG. 1 shows a sectional view of an electric motor. This electric motor is a three-phase external rotor motor having a stator 1, a rotor 2 radially surrounding the stator 1 and a housing 3. The rotor 2 carries permanent magnets 2a which cooperate with windings 11 of the stator 1. The power supply of the stator windings 11 is controlled by a control electronics 5.FIGS. 2 and 3 show the stator 1 of this electric motor. FIG. 4 schematically shows a step of mounting components of the stator 1. The stator 1 has a stack 12 of stator laminations, for example of electrical steel or other soft magnetic steel, which is annular in cross section. This stack 12 has slots on its radial outer side, for example eighteen slots, in which electrically insulating inserts 13, for example made of paper or plastic, can be arranged. Between the slots, the sheet metal stack 12 forms stator teeth which are directed radially outwards and are surrounded by the stator windings 11.End caps 14 are arranged at the two axial ends of the sheet metal stack 12. The end caps 14 have axial projections 14a, 14b, 14c which form passages and wire guides for winding wire therebetween. The end caps 14 thus facilitate the correct wire guidance between the individual windings 11 and the correct interconnection of the individual windings 11, in particular of the three phases, and additionally serve for the electrical insulation of the phases with respect to one another and with respect to ground. To accomplish this task, the two end caps 14 must be properly positioned and centered relative to each other, particularly with respect to their rotational angle position and the resulting wire clearance between the stator teeth.In order to achieve a correct positioning of the two end caps 14, in the exemplary embodiment shown, grooves 15 aare arranged on a radial inner side of the sheet metal stack 12. The end caps 14 have corresponding grooves 15b on their radial inner side, which grooves continue the grooves 15a of the sheet metal stack 12 in the assembled state. The grooves 15a, 15b extend linearly in the axial direction. For assembly, a tool 20 shown in FIG. 4 is used, which has pins 21, which are first introduced into the grooves 15 bof one of the two end caps 14, then into the grooves 15 aof the sheet metal stack 12 and finally also into the grooves 15 bof the other end cap 14. The pins 21 of the tool 20 thus ensure the rotational angle positioning of the end caps 14 relative to one another and the centering relative to the sheet metal stack 12, it being also possible in this case to center the end caps 14 beforehand using the pins 21 and then to realize the position by axial prestress.In the exemplary embodiment shown, six grooves 15 aand 15 bare arranged equidistantly in each of the end caps 14 and in the sheet metal stack 12, and the tool 20 accordingly has six pins 21. This symmetry is the same as the symmetry of the three-phase windings of the stator 1.In the exemplary embodiment shown, the grooves 15 a, 15 bhave a cross section in the form of a segment of a circle, matching the pins 21 which are circular in cross section. For a simple positioning of the end caps 14 and the sheet metal stack 12 relative to one another, it is sufficient in the case of pins 21 which are circular in cross section if the grooves 15 a, 15 bhave the shape of a segment of a circle in the region of their base, i.e. the grooves 15 a, 15 bmay widen at a greater distance from their base.The depth of the grooves 15 a, 15 bin the radial direction is smaller than the radius of the circle segment in the exemplary embodiment shown and thus also smaller than the radius of the cross section of the pins 21, in order to facilitate the positioning of the pins 21.List of reference characters1 Stator 2 Rotor 2 a Permanentmagnet magnet 3 Housing 4 Shaft 5 Control electronics 11 Winding 12 Stack 13 Insert 14 End cap 14 a 14 b 14 c 15 a Nut 15 b 20 Tool 21 Pin

Claims

Three-phase external rotor motor having a stator (1) and a rotor (2) surrounding the stator (1), wherein the stator (1) has a sheet stack (12) which is annular in cross section, end caps (14) arranged at the two ends of the sheet stack (12) and stator windings (11) arranged in slots on a radial outer side, and the stator (1) has slots (15a, 15b) on a radial inner side, characterized in that the end caps (14) have slots (15b) on a radial inner side and the slots (15a, 15b) run in a straight line in the axial direction from one of the two end caps (14) via the sheet stack (12) to the other end cap (14), and the rotor (2) has permanent magnets (2a).Three-phase external rotor motor according to claim 1, characterised in that the number of slots (15a, 15b) on the inner side of the stator (1) is an integer multiple of the number three and the slots (15a, 15b) are arranged evenly distributed in the circumferential direction.Three-phase external rotor motor according to one of the preceding claims, characterized in that the stator (1) has six slots (15a, 15b) on its inner side.Three-phase external rotor motor according to one of the preceding claims, characterized in that the grooves (15a) have the shape of a segment of a circle at least in the region of their base.Three-phase external rotor motor according to claim 4, characterised in that the grooves (15b) in the end caps (14) have a depth which is smaller than the radius of the segment of a circle.Three-phase external rotor motor according to one of the preceding claims, characterized in that the stator (1) has 18 slots.Method for mounting a stator (1) for a three-phase external rotor motor, wherein stator laminations are stacked to form a plate stack (12) which is annular in cross section and has grooves (15a) running in a straight line on a radial inner side in the axial direction, and end caps (14) which have grooves (15b) on a radial inner side are attached to the plate stack (12) at the two axial ends of the plate stack (12), wherein a tool (20) is used for attaching the end caps (14), said tool having pins (21) which are first introduced into the grooves (15b) of one of the two end caps (14), then are introduced into the grooves (15a) of the plate stack (11) for positioning this end cap (14) relative to the plate stack (11), until these pins (21) protrude from the end of the sheet stack (11) facing away from the tool (20), and thereafter the other end cap (14) is positioned on this end of the sheet stack (12) by inserting the pins (21) into the grooves (15b) of this end cap (14), removing the tool (20) from the sheet stack (12) and fitting stator windings (11) in slots on the outside of the sheet stack (12) and the end caps (14).

Images