Outer body of an electromechanical energy converter

In an electromechanical energy converter having an outer body and an inner body, which are mounted movably relative to one another about an axis of rotation, an outer body according to the invention surrounds an annular structural element, a permanent magnet and a support ring which is received concentrically in the structural element. The support ring comprises a recess to receive the permanent magnet, and the recess has a boundary surface which extends parallel as to a radius of the axis of rotation.

BACKGROUND OF THE INVENTION

An electromagnetic energy converter, which in the form of an electric motor converts an electrical current into a rotational movement or in the form of a generator converts a rotational movement into an electrical current, conventionally comprises two bodies which are arranged so as to be movable relative to one another about an axis of rotation. That body which is static in relation to an observer is referred to as the stator, and the movable body is referred to as the rotor. The stator often comprises a so-called pole pot in which a number of permanent magnets are distributed over a radial inner surface. A rotor which corresponds to the stator comprises a number of electromagnets which interact electromagnetically with the permanent magnets. The permanent magnets are conventionally adhesively bonded in the pole pot and are alternatively or additionally braced by means of elastic elements. The elastic elements are for example spring clips which force adjacent permanent magnets apart in the circumferential direction and lock them on the pole pot.

If an adhesive bond is not possible for example from a manufacturing aspect or from a loading aspect, a fastening of the permanent magnets by means of spring clips may be problematic if the dimensions of the permanent magnets and the spacings thereof lie below certain practically manageable thresholds.

SUMMARY OF THE INVENTION

It is an object of the invention to specify a stator for an electromagnetic energy converter, which realizes an improved fastening of the permanent magnets. It is a further object of the invention to specify a method for assembling the stator.

In an electromechanical energy converter having an outer body and having an inner body which are mounted so as to be movable relative to one another about an axis of rotation, an outer body according to the invention comprises an annular structural element, a permanent magnet and a support ring which is accommodated concentrically in the structural element, wherein the support ring comprises a cutout for receiving the permanent magnet and the cutout has a delimiting surface which extends parallel to a radius of the axis of rotation.

It is advantageously possible for forces between the permanent magnet and the support ring, which may arise for example during the operation of the electromechanical energy converter, to be transmitted by the delimiting surface, such that a fastening of the permanent magnets by means of an adhesive and/or by means of a discrete spring element is not necessary. In this way, the manufacture of the outer body can be simplified and/or the operational reliability of the electromechanical energy converter can be improved.

The permanent magnet may be delimited by a surface which extends in a plane which encompasses the axis of rotation. Here, the permanent magnet may be designed to be curved about the axis of rotation. In another embodiment, the surface which delimits the permanent magnet extends in a plane which runs parallel to, but which does not encompass, the axis of rotation. Here, the permanent magnet may be of non-curved form, that is to say it may comprise substantially only planar surfaces, for example by being of cuboidal form. In both cases, the surface of the permanent magnet bears against the delimiting surface of the support ring and the delimiting surface of the support ring extends in a plane parallel to the axis of rotation.

The structural element preferably has a radial inner surface for mounting the permanent magnet in the radially outward direction, wherein the inner surface of the structural element extends perpendicular to a radius of the axis of rotation. Form-fitting mounting of the permanent magnet, and rotational locking of the support ring, can be realized by means of the thus at least sectionally polygonal form of the radial inner surface of the structural element. Furthermore, in the specified way, a large-area transmission of force between the permanent magnet or the support ring and the structural element is attained, such that locally highly loaded bearing surfaces, which may lead to damage to the permanent magnet, to the support ring and/or to the structural element, can be avoided. The structural element may be in the form of a magnetic yoke element for the permanent magnet, wherein the described areal contact with the permanent magnet advantageously promotes the transmission of a magnetic field.

The permanent magnet may have a planar radial outer surface for engaging with the planar radial inner surface of the structural element; here, the permanent magnet may have an equal thickness and may in particular be cuboidal. The cuboidal form is a standard design for permanent magnets, such that cheap standard permanent magnets can be installed.

The permanent magnet may comprise a lanthanoid (a “rare earth”). Particularly powerful permanent magnets can be produced from lanthanoids, in particular in conjunction with neodymium and/or samarium. Such high-power magnets may be of very compact dimensions, and in particular relatively thin in the radial direction. The fastening according to the invention of the permanent magnet with respect to the structural element may be used particularly advantageously in the case of thin permanent magnets, because a fastening of the permanent magnet by means of spring elements, clips or rivets is difficult owing to the small engagement surfaces.

The support ring and the structural element may have radial elements, which engage into one another, for securing against relative rotation about the axis of rotation. Such radial elements may comprise for example a lug which extends in the radial direction, and a groove which corresponds to the lug. An additional securing action against rotation of the support ring in the structural element can be attained in this way. Furthermore, an axial insertion of the support ring into the structural element can be facilitated by the radial elements which engage into one another.

The support ring may have, in the region of the cutout, a holding element for mounting the permanent magnet in the radially inward direction. By means of the holding element, the permanent magnet can advantageously be prevented from falling into the structural element during assembly and/or during operation of the electromagnetic energy converter. The outer body may comprise an axial closure element for closing off the structural element, wherein the structural element is of pot-shaped form with a base, and the support ring is mounted axially on the base of the structural element and on an inner surface of the closure element. The outer body thus formed, the permanent magnet of which is locked in both axial directions, both radial directions and both circumferential directions, can be assembled easily and quickly.

A method for assembling an outer body comprises the steps of providing an annular structural element, a permanent magnet and a support ring which is designed to be accommodated in the structural element concentrically about an axis of rotation, wherein the support ring comprises a cutout for receiving the permanent magnet and the cutout has a delimiting surface which extends parallel to a radius of the axis of rotation.

The method according to the invention comprises only a small number of simple steps, with which the elements of the outer body can be joined together in a simple and efficient manner. A multiplicity of outer bodies according to the invention can easily be mass-produced manually, in automated fashion or in combined manual and automated fashion.

During the insertion of the permanent magnet, the support ring may be aligned substantially perpendicular to the force of gravity, such that the permanent magnet is inserted perpendicular to the force of gravity. The use of auxiliary devices for temporarily fixing the permanent magnet in the support ring during assembly can thereby be facilitated or eliminated.

The method may furthermore comprise the step of axially closing off the structural element in a closure element, wherein the structural element is of pot-shaped form with a base and the support ring is mounted axially between the base of the structural element and an inner surface of the closure element. Said step may precede an insertion of an inner body of the energy converter, such that both the assembly of the outer body and also the assembly of the energy converter can be completed by means of the described step.

DETAILED DESCRIPTION

FIG. 1shows a stator100of an electric motor in a perspective and partially transparent illustration. The electric motor, as one possible exemplary embodiment of an electromechanical energy converter, comprises an outer body in the form of the stator100and an inner body (not illustrated) which, in the illustration ofFIG. 1, is a rotor.

A pole pot110with a base115and a flange120extends along an axis of rotation105. The flange120extends radially outward at a top end of the pole pot110and has two moldings with in each case one fastening hole125for fastening the electric motor. In the region of an inner delimitation of the flange120, three depressions130in the axial and radial direction are formed into the pole pot110. Lugs135extend in the radially inward direction from a wall of the pole pot110. The lugs135are formed at different distances from the base115.

The pole pot110comprises a number of planar inner surfaces145which interrupt an otherwise circularly curved wall of the pole pot110at regular intervals. The lugs135are formed in each case on curved portions of the pole pot110which are situated between the inner surfaces145. In the pole pot110there is accommodated a support ring150, the radial outer side of which is, in sections, in form-fitting engagement with the radial inner side of the pole pot110. The support ring150bears against the base115of the pole pot110. The support ring150comprises a row of cutouts in which in each case one cuboidal permanent magnet155is accommodated such that the permanent magnet155bears areally against one of the inner surfaces145of the pole pot110. The support ring150furthermore comprises grooves160which run parallel to the axis of rotation105and which are formed so as to correspond with the lugs135in such a way that the support ring150can be inserted into the pole pot110along the axis of rotation105from above until said support ring bears against the base115. Here, a rotation of the support ring150about the axis of rotation105is prevented by an engagement, in the circumferential direction, between the lugs135and the grooves160.

The support ring150is manufactured from a non-magnetic material, for example from a plastic. Forces exerted on the support ring150in the circumferential direction by the permanent magnets155are transmitted to the pole pot110as a result of the form fit of the support ring150with the pole pot110. The lugs135and the grooves160which correspond thereto can likewise transmit forces, which act in the circumferential direction, between the support ring150and the pole pot110. Flanks of the lugs135may bear at one side or at both sides against the corresponding grooves160so as to transmit forces, which arise in the event of a rotation of the pole pot110relative to the support ring150about the axis of rotation105, in one or both directions of rotation.

The pole pot110may be composed of a magnetically soft material, such that it can be used not only for receiving other elements but also for conducting magnetic fields between the permanent magnets155. In the illustrated embodiment, an inner diameter of the pole pot110is approximately 40-65 mm. The permanent magnets155are preferably high-power magnets formed from a neodymium-iron-boron compound or a samarium-cobalt compound. A thickness of the cuboidal permanent magnets155in the radial direction is approximately 1.5 mm-2.5 mm. The stator100illustrated inFIG. 1is part of an electric motor with a power of up to 200 W, preferably of approximately 50-180 W, and is provided for use in an ABS hydraulic system for use in a motor vehicle.

The stator100can be completed to form an electric motor and/or generator by the insertion of a rotor (not illustrated) along the axis of rotation105, and the mounting of a rear cover (likewise not illustrated). The cover may engage into one or more of the depressions130and thus be secured against rotation.

FIG. 2shows a detail view of the stator100fromFIG. 1from a different perspective. It can be clearly seen how the permanent magnet155, the largest planar outer surface of which points radially outward, bears areally against the planar inner surface145of the pole pot110. The support ring150likewise bears areally against the pole pot110in the region of the inner surface145. The support ring150does not bear areally against a curved portion210of the pole pot110adjacent to the inner surface145, but rather forms a groove160for receiving the lug135of the pole pot110. The support ring150can thereby be inserted in the axial direction into the pole pot160, and thereafter conducts forces acting in the circumferential direction into the pole pot110. In the embodiment illustrated, only one flank of the groove160bears against the lug135in the circumferential direction. If forces in the circumferential direction between the support ring150and the pole pot110are to be expected only in one direction, for example because the direction of rotation of the electric motor is invariable, said forces can be transmitted by the one-sided engagement between the lug135and the groove160. At the same time, the groove160is designed to be so wide that a certain clearance remains on that side of the lug135which is not in engagement with the groove160, such that free axial movement of the support ring150is permitted during assembly in the pole pot110, without the need for a highly precise fit between the lug135and the groove160.

FIG. 3shows a further detail of the stator100fromFIGS. 1 and 2from yet another perspective. The support ring150and the permanent magnet155are shown in an exploded illustration from the outside, with the viewing direction toward the axis of rotation105.

The support ring150has a cutout310for receiving the permanent magnet155. The cutout310is defined by two mutually opposite axial delimitations320, and by two mutually opposite delimitations330which run in the circumferential direction, of the support ring150. The delimitations330extend in a plane which runs parallel to the axis of rotation105(not illustrated) but which does not encompass the axis of rotation105. Said embodiment corresponds to the illustrated cuboidal form of the permanent magnet155. In another embodiment, the permanent magnet155is formed so as to be curved about the axis of rotation105in the manner of a shell, and the delimitations330extend in a plane which encompasses the axis of rotation105. Two holding elements340form axial contact surfaces for the permanent magnets155.

When the permanent magnet155has been inserted into the cutouts310, a part of that side of the permanent magnet155which faces away from the viewer, said side bearing against the inner surface145of the pole pot110inFIGS. 1 and 2, rests on the holding elements340in the radially inward direction, such that the permanent magnet155is fixed in the radial direction between the support ring150and the pole pot110. Fixing of the magnet155relative to the support ring150in the circumferential direction and in the axial direction is realized by means of a form fit of the outer edges of the permanent magnets155with the delimitations330and320of the cutout310. The permanent magnet155is thereby fully fixed relative to the pole pot110when the support ring150, as illustrated inFIG. 1, has been pushed axially into the pole pot110and secured in the axial direction against displacement in the upward direction. Said securing is conventionally realized, as explained in more detail above with reference toFIG. 1, by means of a cover which closes off the pole pot axially.

FIG. 4shows a method400for producing the stator100fromFIGS. 1 to 3. In a first step410, the method400is in a starting state. In a subsequent step420, the pole pot110, the permanent magnets155and the support ring150are provided. Then, in a step430, the permanent magnets155are inserted in the radial direction from the outside into the cutouts310of the support ring155. For this purpose, the support ring150may be aligned substantially perpendicular to the force of gravity, that is to say the axis of rotation105runs in the direction of the force of gravity and the permanent magnets are inserted with a movement perpendicular to the force of gravity. Here, the support ring150may be arranged on an assembly mandrel in order to fix it in said position and provide additional strength. The permanent magnets155may be inserted into the cutouts310with a slight force fit, such that no additional securing of the permanent magnets155to prevent them from falling out of the support ring150is required during the further course of the process400.

Subsequently, in a step440, the support ring150with the permanent magnets155and possibly the assembly mandrel is inserted axially into the pole pot110. Alternatively, the pole pot110may also be placed over the support ring150with the permanent magnets155. The assembly mandrel can thereafter be removed from the support ring150.

In a subsequent step445, which is not necessarily encompassed by the method400and which may also be assigned to another method for the final assembly of an electric motor or generator, a rotor is inserted axially into the stator100.

In a subsequent step450, by virtue of a cover being mounted axially, the support ring150is secured axially in the pole pot110, and at the same time the electric motor is completed. The method400terminates in an end state460.