HK1208289A1 - Element of an electrical machine having a holder and a permanent magnet, component having at least one element, and an electrical machine - Google Patents

Description

Element of an electric machine having a holding device and a permanent magnet, component having at least one element, and electric machine

Technical Field

The invention relates to an element of an electric machine having a holding device with a first end face having a connecting section fixed to a rotor hub and a second end face, and having at least one permanent magnet magnetized in the circumferential direction of the electric machine, which permanent magnet is inserted into a recess of the holding device. The invention further relates to a component of an electric machine, in particular a rotor having a rotor hub, and to an electric machine.

Background

Such an element is known from EP 1166423B 1. A multi-pole, permanent-magnet-excited rotor for a rotating electrical machine is discussed, in which two square, circumferentially magnetized, flat permanent magnets are arranged in a slot-shaped intermediate space, which is arranged in each case between two half-yokes fastened to the rotor body, radially with respect to the rotor axis, in order to produce distinct magnetic poles. Each rotor yoke or pole element is divided in the circumferential direction into two half-yokes each extending over a half-pole pitch. The two half-yokes of two yokes arranged next to one another are connected by means of end plates to form pole elements, and each pole element is itself fastened, in particular screwed, to the rotor body or to the rotor hub. The yoke configuration is also selected such that a cavity is formed between the two circumferentially arranged pole elements, said cavity being able to influence the magnetic flux of the respective yoke halves. However, the shape of the yoke is disadvantageous when the magnetic field is formed not only in the region of the air gap between the rotor and the stator but also in the rotor body.

In the construction of electrical machines, in particular synchronous machines, permanent magnets can be used instead of coils in the rotor and/or stator. The stator represents a stationary component and the rotor represents a moving component of the electric machine. Known materials for producing permanent magnets are, inter alia, bismuth-manganese magnets, alnico magnets, samarium-cobalt magnets and neodymium-iron-boron magnets. The outer armature and the inner armature are distinguished in the synchronous machine. The inner armature is one configuration of a synchronous machine in which the rotor is centrally located and the stator surrounds the rotor. The rotor usually has a plurality of permanent magnets in an inner armature, which are alternately oriented radially and arranged annularly around the rotor axis and move in a circular path in accordance with the rotor axis. The resulting magnetic field in the case of this arrangement of permanent magnets is also referred to as the excitation field. During the movement of the permanent magnets, voltages are induced in the stator coils due to the constant change of the magnetic field acting on the stator coils, as a result of which, during generator operation of the electric machine, currents are generated as a function of the movement of the rotor.

The permanent magnets are usually arranged on the rotor hub of the rotor such that their magnetization direction or pole orientation runs parallel to the radial direction. Various possibilities have already been considered for this purpose for fixing the permanent magnet. One possibility is: the magnets are fixed to the rotor hub by means of specially produced holding devices. Here, the requirements are: the rotor laminations must absorb not only the centrifugal forces of the permanent magnets but also the forces generated by the magnetic interaction between the permanent magnets and the stator coils and also other magnetic components of the rotor or stator in the radial direction during operation. The magnetic force which the rotor laminations must absorb therefore additionally acts on the permanent magnets themselves in the direction of their magnetization. For this reason, the rotor laminations must be constructed both solid and stable in order to take into account the forces mentioned. The permanent magnets are usually inserted into recesses in the rotor laminations, whereby the webs extend between the recesses and the air gap toward the stator. The task of the web is to absorb forces in the radial direction. The magnetic resistance of the connection lug is generally not large, and the wider the connection lug is, the smaller the magnetic resistance is. In order to ensure sufficient mechanical strength, the greater the magnetic field, the weight of the permanent magnets and the rotational speed of the rotor, the more widely the connecting webs must be formed, on the one hand, in order to be able to ensure sufficient mechanical strength, but on the other hand, the more slender the connecting webs must be formed, since the connecting webs otherwise, due to their low magnetic resistance, may short-circuit a significant proportion of the magnetic flux of the permanent magnets and may significantly weaken the remaining magnetic field acting on the stator coils. In other words, this means: the webs should be as slender as possible and therefore have a greater reluctance and therefore a greater effective excitation flux density. The efficiency of the electric machine is decisively influenced by the effective excitation flux density and thus by the width of the webs. In this regard, one major problem is that: the width of the connecting piece is narrowed while at the same time ensuring sufficient mechanical stability and proper distribution of the magnetic flux density. In addition, this shaping of the rotor laminations, in particular in the connecting section, is disadvantageous in view of the magnetic flux density.

To solve this problem, another approach is: permanent magnets magnetized in the direction of extension are arranged in a V-shaped arrangement in the rotor lamination, as can be gathered from DE 102011051947 a 1. In this case, the poles of the permanent magnets are no longer arranged radially and obliquely, which force cannot be completely avoided despite the smaller magnetic force acting in the radial direction between the permanent magnets and the stator. In the present case, moreover, a high armature reaction occurs, which reduces the efficiency of the electric machine.

Disclosure of Invention

Accordingly, the object of the invention is to hold a permanent magnet with poles oriented in the circumferential direction by means of a holding device such that the composition of the magnetic field of the permanent magnet is optimized.

This object is achieved by an element of an electric machine having a holding device and at least one permanent magnet having the features of claim 1.

According to the invention, an element of an electric machine is proposed, comprising a holding device having a first end face with a connecting section for fastening to a rotor hub and a second end face into which the permanent magnets are inserted, and at least one permanent magnet magnetized in the circumferential direction of the pole, wherein the second end face has a recess in the at least one permanent magnet.

Such a recess of the second end face aims at: the material of the holding device is formed as little as possible in the radial region between the at least one permanent magnet and the air gap between the rotor and the stator, so that this region only slightly short-circuits the magnetic flux of the permanent magnet. Furthermore, the width of the air gap between the stator and the rotor is defined by means of the shaping of the recess. The wider the gap, the greater the reluctance at that location. The shape of the transition between the recess and the actual second end face of the holding device is therefore of decisive significance, since the properties of the magnetic field or the distribution of the magnetic flux density in the gap can be determined precisely in this way. Therefore, for example, the center of gravity of the magnetic flux density of the magnetic field can be limited to an appropriate position.

By fitting at least one permanent magnet into the recess, the holding device holds the permanent magnet securely so that it does not become detached from the holding device due to the forces acting in the machine. In this context, it is possible to very effectively avoid that the permanent magnets detach from the rotor hub of the rotor or move accidentally and reduce the air gap existing between the rotor and the stator or even contact the stator, so that the permanent magnets damage the electrical machine.

By means of the magnetization direction of the permanent magnets in the circumferential direction of the electrical machine, the holding device can be designed such that it does not extend between the at least one permanent magnet and the air gap. The recess here transitions into a recess which accommodates at least one permanent magnet. The closed path of the magnetic flux of the permanent magnet or the magnetic circuit in the direction of the stator coil can therefore be stronger, since the magnetic flux of the permanent magnet is not short-circuited by the holding device due to the higher magnetic resistance of the first connecting piece. The advantageous design of the holding device also leads to an improvement in the magnetic flux density distribution, whereby a higher efficiency of the electrical machine is achieved. Since the permanent magnets extend in the radial direction of the rotor such that the largest face of the permanent magnets is parallel to the radial direction, this face of the permanent magnets can be bonded particularly well to the radially extending face of the recess by means of an adhesive, an adhesive or the like. The centrifugal force occurring during rotation is thereby transmitted as a shearing force from the adhesive connection between the permanent magnet and the holding device. The shear stress can in principle be better transmitted as a normal force by means of an adhesive or the like. The safety against failure of the adhesive connection is thus significantly increased.

By virtue of the orientation of the poles of the at least one permanent magnet extending in the circumferential direction, no magnetic forces act on the at least one permanent magnet in the radial direction during operation of the electrical machine, so that the holding device only has to absorb the centrifugal forces acting on the permanent magnet in the radial direction, while the remaining magnetic forces in the circumferential direction can be absorbed more easily by the holding device depending on its orientation.

After the at least one permanent magnet has been inserted into the recess, it can additionally still be fixed in the recess by means of an adhesive or adhesive.

Additionally or alternatively, the first end face and the second end face are connected by two at least segmented, preferably radially inwardly curved flanks. The second end face of the holding device extends in the region of the air gap between the rotor and the stator, i.e. away from the rotor hub. By means of the inwardly curved side faces, the holding device is designed in such a way that it converges funnel-shaped or trumpet-shaped from the second end face to the first end face. In the region of the connecting section between two elements adjacent in the circumferential direction of the rotor, i.e. on the rotor hub, a significantly larger distance can thus be formed than in the region of the second end face. By means of the significantly greater distance in the region of the connecting section between two elements adjacent in the circumferential direction of the rotor, a large magnetic resistance prevails in this region due to air, whereas a lower magnetic resistance exists in the region in which the distance between two elements adjacent in the circumferential direction of the rotor in the region of the air gap between the rotor and the stator is smaller and thus the ferromagnetic material of the holding device is significantly more present. The magnetic flux of the at least one permanent magnet of the holding device can be provided very effectively here in the direction of the air gap between the rotor and the stator, so that the efficiency of the electrical machine is significantly increased. Thus, a preferred direction is predetermined for the magnetic field, wherein the shaping of the end faces decisively influences the magnetic flux density distribution in the direction of the air gap. In addition to this shape, the aspect ratio of the holding means is also critical for the flux density distribution. Furthermore, this illustrated shape of the holding device substantially limits the armature reaction in the holding device, since the armature field excitation generated by the stator current counteracts large magnetic resistances, thereby positively influencing the efficiency of the electrical machine. Furthermore, by this shape design of the holding device, a large weight saving can be achieved due to material savings. This shape design is particularly good, precisely in synchronous machines which can have large diameters, and in the case of holding devices which are arranged in the outermost region of the rotor and where the centrifugal forces act most strongly, in order to reduce the centrifugal forces acting on the rotor. At the same time, the component, in particular the holding device, can be constructed with the aid of a material having a lower strength. It is also advantageous that the rotor starts more quickly at the start of operation due to the lower moment of inertia. By means of such a constructive counter-inductance of the two side faces, it is also possible to provide a magnetic flux such that a current profile which approximates a sine wave particularly well is generated when the rotor rotates.

In one refinement, the first connecting web can extend parallel to the first end face. However, by means of permanent magnets magnetized in the circumferential direction of the rotor extending radially and fitting into the recesses, it can happen that the holding device is deformed unintentionally in the region of the second end face due to centrifugal forces. In order to overcome this deformation, a first connecting web is provided in the region between the air gap and the at least one permanent magnet, which first connecting web ensures the strength and stability of the holding device. It is of course advantageous if the webs are designed as slender as possible, so that they only slightly short-circuit the magnetic flux. Furthermore, the short-circuit effect of the permanent magnets due to the first connecting webs can be compensated by a suitable length of the at least one permanent magnet in the radial direction, since a greater length generally means a greater magnetic flux of the permanent magnet.

In addition or alternatively, the holding device of the component according to the invention can have a second web in the region of the connecting section, which extends parallel to the first end face. The second web is provided in the region of the connecting section in such a way that the material of the permanent magnet and the material of the holding device have different coefficients of expansion at high temperatures. Disengagement of the permanent magnets and/or the holding means from the rotor hub can thus be effectively avoided. It is also advantageous if the second connecting lug is also of relatively slender design, so that it only slightly short-circuits the magnetic flux.

The recess can have at least one spoke extending transversely to the first end face if at least two permanent magnets, which preferably extend radially after the mounting of the holding device on the rotor hub, are accommodated in the recess. The mechanical strength of the holding device is further improved by means of the at least one spoke.

Preferably, the second end face can be formed in sections in an outwardly curved or arched manner. By means of such a configuration of the second end face, a magnetic flux can be provided, so that a particularly well-approximated sinusoidal current profile is generated when the rotor rotates. Thus, when the holding means is used in the inner armature, the circular shape of the rotor can be formed.

Alternatively, the second end face can be formed in sections in an inwardly curved or curved manner. By means of such a configuration of the second end face, a magnetic flux can be provided, so that a particularly well-approximated sinusoidal current profile is generated when the rotor rotates. The circular shape of the stator can thus be formed when using the holding device in the outer armature.

The connection section can also be designed as a dovetail connection. The corresponding dovetail shape of the rotor hub, which is made of a non-ferromagnetic material, precisely surrounds and is embedded in the connection section in a magnetically insulating manner so as to have a high impedance for the magnetic flux. The magnetic resistance is therefore also particularly great, since the largest possible proportion of the material surrounding the permanent magnets in the direction of the rotor axis is formed by the material with poor magnetic conductivity due to the three-sided, spaced-apart surrounding of the radially inner end of the magnet. In contrast, a preferred direction in the direction of the stator is thereby achieved for the magnetic flux, since the holding device has a significantly lower magnetic resistance in this direction. That is, by means of this arrangement of the permanent magnets, the symmetry of the magnetic field is interrupted, so that the magnetic field preferably develops in the direction of the air gap. This measure therefore increases the magnetic flux density in the region of the air gap between the stator and the rotor, which leads to an increase in the efficiency of the machine.

By means of the dovetail connection provided on the connection section, the holding device is firmly connected with the rotor hub. In addition to the high reliability of the connection and the relatively simple production, the mounting of the two components can be performed in a simple manner. The dovetail connection furthermore does not influence the magnetic properties of the permanent magnet itself.

Furthermore, a receptacle for at least one connecting means for the non-positive connection of a plurality of holding devices can be provided on at least one side, wherein the connecting means is insulated with respect to the holding devices. If a plurality of holding devices are arranged along the axial direction of the rotor hub, these holding devices can be connected to each other along the axial direction by means of a connecting mechanism to be arranged as a holding device group. The holding device can be connected in a force-fitting manner by the connection means not only before mounting on the rotor hub but also after mounting on the rotor hub. The connecting means can be, for example, a rod and preferably consist of a non-ferromagnetic material in order to prevent the generation of disturbing magnetic fields. In order to insulate the connection means both magnetically and electrically from the holding device, an insulating medium, for example an adhesive, a resin or the like, is introduced into the receptacle.

It is particularly advantageous if the receptacle can be designed as an eyelet-like depression with a cutout. The connection means can be accommodated particularly well by the formation of the eyelet-shaped receiving portion. The cutout extending over the eyelet-shaped receptacle is preferably designed to avoid possible interfering magnetic fields forming around the eyelet-shaped receptacle.

Furthermore, the holding device can have a north section and a south section, which are connected to one another by a first connecting web. By means of the insertion of at least one permanent magnet magnetized in the circumferential direction of the rotor into the recess of the holding device, the permanent magnet causes: the north and south pole sections of the holding device are also located in the circumferential direction of the rotor. When several, for example two, permanent magnets are inserted into the recess, the arrangement of the north pole section or south pole section is also not changed, since the poles of the permanent magnets are always inserted into the recess in the same manner in an oriented manner (gleichgerichlet). The primary first connecting web is thus designed to ensure the strength of the holding device as a function of the centrifugal forces caused by the rotation. The arrangement of the circumferentially adjacent elements is furthermore selected such that the same poles, i.e. the north pole section and the north pole section of the adjacent element or the south pole section and the south pole section of the adjacent element, face each other, so that the magnetic flux is better formed radially outward.

The holding device can furthermore be formed in one piece or as an integrated component. This makes it possible to generate a particularly good homogeneous magnetic field, since the magnetic field is not interrupted by the multiple-part nature of the holding device. The one-piece construction of the holding device has also proved to be advantageous with regard to its mechanical stability.

In addition to or alternatively to the present inventive concept, the ratio of the length of the permanent magnet in the radial direction to the half-clear width of the holding device in the circumferential direction can be selected such that the material of the holding device and/or of the stator teeth just reaches the region of magnetic saturation. The field flux can thus be set to a suitable maximum value, in particular in the stator teeth.

In addition to or alternatively to the present inventive concept, the connection section and the at least one permanent magnet can be configured such that a face of the at least one permanent magnet facing the end side of the rotor hub is closer to the rotational axis of the rotor than a side face of the rotor hub. This arrangement also results in the magnet being surrounded on three sides at its radially inner end by the material of the rotor hub having a high magnetic resistance. As a result, the distribution of the magnetic flux density, in particular in the region of the permanent magnets facing the rotor hub, is effectively deflected radially outward, i.e. in the direction of the air gap between rotor and stator, as a result of which the magnetic flux density is significantly increased radially outward. By means of this arrangement of the permanent magnets, the symmetry of the magnetic field is interrupted in a similar manner as in the dovetail connection.

In addition to or alternatively to the present inventive concept, the holding device can be configured such that its smallest cross section in the radial direction is configured in a distance extending from the rotational axis of the rotor to the side surface of the rotor hub or less. By forming the smallest cross section possible in height or more in detail in the direction of the axis of rotation, the magnetic field lines are also effectively turned radially outwards so that the available magnetic flux density is increased. The smaller the perpendicular distance between the first end face and the smallest cross section, the more the symmetry of the magnetic field is interrupted and the magnetic field lines are turned radially outwards in this way.

Furthermore, the smallest cross section can have at most five times the thickness of the permanent magnet, preferably at most four times the thickness of the permanent magnet and particularly preferably at most three times the thickness of the permanent magnet. This ratio is particularly suitable for two permanent magnets arranged in the radial direction. In the case of only one permanent magnet inserted into the recess, the smallest cross section can also have at most three times the thickness of the permanent magnet, preferably at most two times the thickness of the permanent magnet, and particularly preferably at most one time the thickness of the permanent magnet. The smaller the smallest cross section is, the more the magnetic field lines are turned radially outwards. However, increasing mechanical loads occur simultaneously in the smallest cross-section of the holding device.

According to a further aspect of the invention, a component of an electric machine, in particular a rotor having a rotor hub, is proposed according to claim 17, wherein a gap is provided between two elements adjacent in the circumferential direction and/or in the axial direction of the component, wherein the gap is either an air gap or an elastic material is introduced therein.

The air gap is able to efficiently conduct away the high temperatures generated by the magnetic field of the permanent magnets and also the stator coils, thereby cooling the motor, taking into account the high temperatures generated by the permanent magnets and also the stator coils. The air gap between two circumferentially adjacent elements is smaller in the region of the second end face than in the region of the first end face. Conversely, the air gap of two elements adjacent in the axial direction is constant.

This results in an elastic support of the two elements relative to one another if the space between two elements adjacent in the circumferential direction and/or in the axial direction of the component is filled with an elastic material.

By separating at least two adjacent elements from one another by means of an air gap, eddy currents (Wirbelst rme) which may arise in the holding device can be insulated in a simple manner. This layered design of the holding device also improves the efficiency of the electric machine.

The formation of an air gap also makes it possible to reduce the armature reaction of the magnetic field of the stator between two circumferentially adjacent elements, in particular the holding device.

The fixing of the elements on the rotor hub can also be performed by means of an adhesive or a combination of both, in addition to the dovetail connection. Screwing, welding and press fitting of the setting element in the rotor hub are also possible. It should also be noted that the rotor hub is constructed of a non-ferromagnetic material.

Furthermore, at least two elements can be spaced apart therebetween in the axial direction by means of the supporting element. The support element thus advantageously makes it possible for at least two elements adjacent in the axial direction to be positioned relative to one another and, in this respect, vibrations, for example rattling of the holding device, are avoided. Vibrations can negatively influence the magnetic field on the one hand and fatigue the material of the component, in particular of the holding device, leading to failure on the other hand. The support elements can be periodically arranged at the same pitch along the circumferential direction. The support elements can furthermore be arranged along the circumferential direction of the rotor in such a way that they each support two circumferentially adjacent elements at a distance from two axially adjacent elements, which are also arranged adjacent to one another in the circumferential direction, and at the same time. In this way, particularly few supporting elements can be provided in the air gap between two elements adjacent in the axial direction, so that the high temperatures of the elements and of the rotor hub can be effectively dissipated. The production costs of the component can also be reduced if the smallest possible number of support elements is used. The support element can likewise be connected to a dovetail connection on the rotor hub of the rotor, but also on a ring provided specifically for the support element, which ring is in turn fixed to the rotor hub. It should also be noted that the holding element is arranged such that the connecting means arranged in the receptacle connect the element in the axial direction in a force-fitting manner, that is to say the holding element does not block the connecting means.

Furthermore, a pressing ring can be provided on the end face of the rotor and/or the rotor hub in order to press the elements against one another in a force-fitting manner. If, in addition to the support elements present in the axial direction of two adjacent elements, a pressing ring is provided on each end face, the elements adjacent in the axial direction are firmly fixed, so that vibrations are largely or even completely avoided. In order to achieve an air gap between the press ring and the holding device spaced therefrom, it is possible to provide further supporting elements. Cooling of the rotor is also effectively promoted in this way.

Furthermore, the at least one supporting element and/or the rotor hub can be composed of a non-ferromagnetic material. By virtue of the rotor hub being designed in a non-ferromagnetic conducting manner or in a highly reluctance manner, the center of gravity of the magnetic flux density can be deflected in a targeted manner radially outward, i.e. in the direction of the air gap between stator and rotor, so that the efficiency of the electric machine is increased. The supporting elements, which are formed non-ferromagnetically, do not further disturb the magnetic field formed by the permanent magnet and the holding device and at the same time support the holding device with respect to one another.

According to a further aspect of the invention, an electrical machine, in particular a generator, is proposed according to claim 21, which has a component, in particular a rotor having a rotor hub. The advantages of such an electric machine have already been described above in the components and in the elements, and reference is made to this for the sake of simplicity.

Drawings

The above-described features and functions of the present invention, as well as other aspects and features, are further described below in the detailed description of the preferred embodiments with reference to the appended drawings. Shown here are:

fig. 1 shows a perspective view of an element according to the invention with a first embodiment of a holding device and two permanent magnets;

fig. 2 shows a cross-sectional view of a rotor hub and a plurality of elements according to the invention arranged in the circumferential direction of the rotor hub;

fig. 3 shows a perspective cross-sectional view of a rotor hub, a plurality of elements according to the invention arranged in the circumferential direction of the rotor hub according to the first embodiment of fig. 1, and an extrusion ring;

fig. 4 shows a sectional view of an element according to the invention according to a second embodiment, arranged on a rotor hub by means of a dovetail connection;

FIG. 5 shows a perspective view of the rotor;

FIG. 6 shows a portion of a cross-sectional view of a magnetic field line diagram of two adjacent elements with one permanent magnet each; and

fig. 7 shows a part of a cross-sectional view of the field line diagram of two adjacent elements with one permanent magnet each longer than in fig. 6.

Detailed Description

Fig. 1 shows a perspective view of an element 1 according to the invention with a first embodiment of one holding device 2 and two permanent magnets 4. The holding device 2 has a funnel-shaped or trumpet-shaped profile in cross section and is made of ferromagnetic material. The holding device 2 can be formed in one piece. However, in order to avoid eddy currents in the holding device 2, the holding device is preferably composed of plates (integrally) layered in sequence in the axial direction of the rotor 100, i.e. in a direction perpendicular to the paper plane of fig. 2. The plates can be provided with a special coating. The stack of plates forming the holding device is made up of the plates that are cut/punched and coated, and the individual plates are subsequently baked onto one another by heating or in the case of a solvent. The coating is therefore also referred to as stoving varnish. Magnetic steel plates are preferably used as the plates.

As can be seen from fig. 1, the connection section 6 is designed as a dovetail 10 in the first end face 8. The dovetail 10 also forms a smallest cross section B when the holding device 2 is viewed from above or along the axial direction a. A substantially trapezoidal recess 14 is formed in the second end face 12 opposite the first end face 8. It should be noted that the recess 14 likewise forms a portion of the second end face 12. The connecting section 13 forms a transition between the recess 14 and the second end face 12. The angle of the connecting section 13 is selected in relation to the position of the desired enhancement of the magnetic field in the recess 14. This position can be either near the rotor 100 or near the stator 200. The significance of the recess 14 is explained separately below. The second end face 12 is also designed to be concave or curved outwardly. The outwardly curved shape of the second end face 12 is related to the diameter of the rotor 100 and/or the stator 200. By means of this convex contour of the second end face, an approximately sinusoidal current profile can be generated during rotation of the rotor. The two end faces 8 and 12 are connected to one another by means of side faces 16 and 18 which are bent in sections inwards, so that the trumpet-like contour mentioned above results. Eyelet-like receptacles 20 and 22 are formed in the inwardly curved sides 16 and 18, respectively. The eyelet-shaped receptacles 20 and 22 each have a cutout 20a and 22a extending in their longitudinal direction, i.e. in the axial direction, so that the generation of disturbing magnetic fields in the circumferential direction of the eyelet-shaped receptacles 20 and 22 is effectively avoided by this interruption. The connection means 20b and 22b can be accommodated in the eyelet-shaped receiving portions 20 and 22. The connection means 20b and 22b are provided for non-positively connecting a plurality of holding devices 2 arranged along the axial direction a of the rotor 100 on the end faces 16 and 18. The connecting means 20b and 22b are in the present case rods with external threads and screws provided on both ends. Furthermore, adhesive is introduced into the eyelet-like receptacles 20 and 22.

The holding device 2 furthermore has a square recess 24, in which two permanent magnets 4 are accommodated. In order to stabilize the holding device 2, a spoke 26 is formed between two accommodated permanent magnets 4 in the radial direction. Although one notch 24 is provided in the present embodiment, a plurality of notches can be easily formed in the holding means. In the course of this, it is also conceivable to form a plurality of spokes in order to ensure the stability of the holding device. By forming the recess 24 in the holding device 2, a first connecting web 28 is produced in the region of the air gap between the rotor 100 and the stator 200 and a second connecting web 30 is produced in the region of the connecting section 6. Specifically, the second web 30 extends between the end-side surface 4a of the permanent magnet 4 and the second end-side 12 of the holding device 2. It should also be noted that the elements 1 are constructed mirror-symmetrically with respect to their respective central axes M not only in the axial direction a but also in the radial direction R.

The two permanent magnets 4 inserted into the recesses 24 have a polar orientation in the circumferential direction U, so that a south pole section 32 and a north pole section 34 are produced. The two permanent magnets 4 are arranged relative to one another such that they are oriented in the same manner in relation to their polarity, i.e. in the case of viewing fig. 1, the two permanent magnets 4 have a north pole N on the right and a south pole S on the left. As already explained above, the two pole sections 32 and 34 are connected to one another by means of the first connecting web 28 and the second connecting web 30 in order to stabilize the holding device 2. By forming the recess 14, the first connecting web 28 extends relatively slender from the north pole section 34 to the south pole section 32, whereby only a small portion of the magnetic field is drawn off in the form of a short circuit by the first connecting web 28. By virtue of the orientation of the poles of the permanent magnet 4 extending in the radial direction R, it is possible for the first connecting web 28 to be of relatively elongate design, since the magnetic forces acting in the circumferential direction U and not in the radial direction R act. The connecting section 13 connecting the end face 12 and the recess 14 is formed at a fixed angle such that the magnetic field lines can be collected in the desired position. As in the case of the first connecting web 28, the second connecting web 30 is also of relatively slender design in order to prevent short-circuit-like removal.

Fig. 2 shows a rotor hub 50 with a side surface 51 after mounting and a sectional view of a plurality of elements 1 according to the invention of the first embodiment arranged in the circumferential direction U of the rotor hub 50. The rotor hub 50 made of a non-ferromagnetic material has a plurality of circular openings 52 arranged in the circumferential direction U for cooling the rotor 100. The elements 1 are periodically fixed in the connecting section 6 at equal distances in the circumferential direction U to the rotor hub 50 by means of the dovetails 10. In addition to the dovetail 10, the element 1 is fixed to the rotor hub 50 by means of an adhesive 36. By means of the fact that the elements 1 are not only attached to the rotor hub 50 in the connecting section 6, as in the prior art, but are also surrounded by non-ferromagnetic material, i.e. the rotor hub 50, by means of the dovetail 10, the magnetic field lines are deflected radially outward, i.e. in the direction of the air gap between the rotor 100 and the stator 200. The dovetail connection 10 thus also contributes to effectively bundling the magnetic field lines, since the magnetic field lines only continue to turn externally in the radial direction before they exit from the holding device 2. The elements 1 are arranged in the circumferential direction U such that a gap 38 is provided between two adjacent elements 1. The gap 38 is designed as an air gap, whereby the armature reaction of the stator magnetic field is reduced and the adjacent holding fixture 2 is cooled by the air flow located therebetween. Furthermore, between adjacent elements 1, support elements 40 are provided, which are arranged offset in the axial direction from elements 1, and a press ring 42 with cooling openings 44, which are illustrated in more detail in fig. 3.

Due to the profiled, i.e. inwardly curved, side faces 16 and 18 of the elements 1, in particular of the holding device 2, the armature reaction caused by the stator 200 is effectively reduced, since the region between two elements 1 adjacent in the circumferential direction U is filled only with air as a magnetic resistance. The armature reaction of the stator 200 is therefore particularly well avoided by this profiling of the holding device 2.

The arrangement shown in fig. 2 of the permanent magnets 4 in the elements 1 arranged along the circumferential direction U of the rotor hub 50 shows: the different poles of the two permanent magnets 4, i.e. the north and south poles, are aligned in the element 1. The polarity of the circumferentially U-adjacent elements 1, and thus the shape of the north sections 34 or south sections 32 of the elements 1, is selected such that the north section 34 of one element 1 faces the north section 34 of the circumferentially U-adjacent element 1 and such that the south section 32 of one element 1 faces the south section 32 of the circumferentially U-adjacent element 1. As a result, the magnetic flux is formed particularly well in the direction of the air gap between the rotor 100 and the stator 200 due to the repulsive effect of the magnetic field formed by the permanent magnets 4 in the circumferential direction.

The permanent magnets 4 are furthermore arranged in the holding device 2 such that their end-side faces 4a are close to the axis of rotation D of the rotor 100, as are the side faces 51 of the rotor hub 50, whereby the magnetic field lines are intensified radially outwards, since the rotor hub 50 is composed of a non-ferromagnetic or highly magnetic-resistant material. In addition to this, the smallest cross section B of the holding device 2 is formed in the radial distance of the side surface 51 of the rotor hub 50. The smallest cross section B is approximately four and one-half times the thickness of the permanent magnet 4 in the circumferential direction U.

Fig. 3 shows a perspective sectional view of a plurality of elements 1 according to the invention and of an extrusion ring 42 of a first embodiment of a rotor hub 50, which elements are arranged in the circumferential direction U of the rotor hub 50. In fig. 3, it can be seen that the pressing ring 42 is arranged at the end of the element group arranged in the circumferential direction U, in other words on the end face 54 of the rotor hub 50. Furthermore, a circumferential lateral surface 51 of the rotor hub 51 can be recognized. A plurality of support elements 38 are arranged at equal distances in the circumferential direction U between the pressing ring 42 and the outermost elements 1 (surrounding element groups) arranged in the circumferential direction U. The support elements 38 are located in such a defined position that they are in contact with two elements 1 adjacent in the circumferential direction U to the same extent, i.e. have a covering of the same two elements 1 adjacent in the circumferential direction U. The layered structure of the elements 1 along the axial direction a of the rotor 100 effectively prevents the formation of eddy currents along the axial direction a of the rotor 100. Fig. 3 also shows that two elements 1 adjacent in the axial direction a are connected to one another in the eyelet-like receptacles 20 and 22 in the axial direction by means of connecting means 20b and 22 b.

Fig. 4 shows a sectional view of an element 1 ' according to the invention of a second embodiment, which is arranged on a rotor hub 50 ' by means of a dovetail connection 10 '. The element 1 'shown in fig. 4 is formed by a holding device 2' which is formed by a part forming the north pole section 34 and a part forming the south pole section 32. North pole section 34 and south pole section 32 depend on the orientation of the poles of permanent magnet 4. The rotor hub 50 'shown in fig. 4 is adapted in comparison to the rotor hub 50 of the above-described exemplary embodiment such that a flange 56 is formed in the region of the permanent magnets 4 of the element 1'. The permanent magnet 4 inserted into the square recess 24 ' of the holding device 2 ' contacts the flange 56 of the hub 50 ' on the end side. Magnetic short circuits are thus effectively avoided both in the air gap between the rotor 100 and the stator 200 due to the absence of the first connecting webs and in the connecting section 6' due to the magnetically insulating rotor hub 50 and the absence of the second connecting webs.

One development of the element 1' shown in fig. 4 consists in: the part forming the north pole section 34 and the part forming the south pole section 32 can be connected to one another via at least one connecting piece on the end side or along the axial direction a.

Although in the second embodiment in fig. 4 no circular openings are provided for cooling the rotor hub 50 ', it is easily conceivable to form such circular openings in the rotor hub 50' as well. In this embodiment, the eyelet-shaped receptacles are not molded into the end-side flanks 16 ', 18'.

Fig. 5 shows a perspective view of the rotor 100 with the axis of rotation D. The rotor shaft 102 has fixed thereto in the following sequence: the first pressing ring 42; a rotor hub 50, the rotor hub 50 having four element groups (four axial element groups) provided on the rotor hub 50 along the axial direction a; a second extrusion ring 42 and a fan wheel 104. The two pressing rings 42 arranged on the end face on the rotor hub 50 press or press the element groups 1 (axial element groups) firmly against one another by means of a not shown pulling mechanism, so that vibrations between the elements 1 are avoided. The pulling means for pressing the pressing rings 42 against one another can be configured similarly to the connecting means 20b and 22b and in the present embodiment pass through the rotor hub 50. Fan wheel 104 is provided to dissipate the high temperature of rotor 100.

Fig. 6 shows a part of a sectional view of two adjacent elements 1 with one permanent magnet 4 each by means of a magnetic field diagram. Further shown is a stator 200 having a plurality of stator teeth 202. From this figure, the magnetic field shown in the form of magnetic field lines is explained below. Wherein the spacing between the magnetic field lines represents the strength of the magnetic flux density. The rotor hub is not shown for a better overview. The shape of the holding device 2 ″ is selected in this embodiment such that it is trapezoidal and forms a dovetail 10 in the region of the connecting section 6.

The magnetic field lines of the permanent magnets 4 shown in fig. 6 are substantially transferred from each permanent magnet 4 to the respective holding means 2 ". The two holding devices 2 ″ then send the magnetic field lines onto the stator teeth 202 of the stator 200 and then back again to the opposite pole of the respective permanent magnet 4. In the region of a stator tooth 202, in particular in the hollow region between two adjacent stator teeth 202, one magnetic field line each can be observed, which can lead to magnetic saturation of the stator tooth 202. In the region of the lower part of the element in the region of the dovetail 10, it can be recognized that only a small proportion of the magnetic field lines leaves in the direction of the rotor hub, not shown. It thus becomes apparent from fig. 6 that the holding means 2 "gathers the magnetic field lines of the permanent magnets 4 and turns them in the direction of the air gap between the rotor 100 and the stator 200. The magnetic field lines in the region of the recess 14 show: only a small fraction of the magnetic field lines of the permanent magnet 4 are magnetically short-circuited by the recesses 14. The recesses 14 thus likewise cause a focusing effect. The ratio of the length l of the permanent magnet 4 in the radial direction R to the half width b of the holding device 2 "is also a measure for the focusing effect or the magnetic flux density of the permanent magnet 4.

Fig. 7 shows a part of a sectional view of two adjacent elements 1 with one permanent magnet 4 each longer relative to fig. 6. Fig. 7 again contains a magnetic field diagram shown in the form of magnetic field lines. The shape of the holding device 2 ″ is selected in this embodiment such that it forms a dovetail connection 10 in the region of the connection section 6, essentially in the manner of a trapezoid. The angle α is here the angle between the first end face 8 of the holding device 2 '"and the first or second end face 16, 18 of the holding device 2'". The trapezoidal shape of the holding means 2 "' substantially expands the height of the permanent magnet 4 again, that is to say the angle a becomes obtuse.

By the illustrated permanent magnets 4 being longer in the radial direction R with respect to fig. 6, the focusing effect in the region of the recesses 14 is enhanced. It thus becomes apparent that the magnetic flux increases with increasing length l, which is discernible in terms of the magnetic flux density. The induction can theoretically continue to increase in this way, but in practice it is limited as seen in fig. 7 by the magnetic saturation that starts primarily in the stator teeth 202. The longer length l selected in the radial direction R of the permanent magnet 4 in fig. 7 relative to the permanent magnet in fig. 6 also shows: the magnetic field line density of the holding device 2 "' of fig. 7 is higher than that of fig. 6. The magnetic saturation of the holding means 2 "' is related to the angle alpha. If the angle α is chosen too sharp, magnetic saturation of the holding means 2 '"occurs and the magnetic field lines exit from the holding means 2'" in a similar manner as is visible in magnetic saturation in the region of the stator teeth 202.

The element configured as a collecting device, consisting of a holding device and a permanent magnet, cannot be magnetized subsequently, since it is not feasible to place the required magnetic flux density on the magnet.

The mounting of the actuator element on the rotor hub is such that a plurality of elements are inserted one after the other along the dovetail of the rotor hub, so that an axial element group, which is preferably connected in a force-fitting manner to the connecting means, is produced. Thereafter, the next element is arranged on the rotor hub with a radial offset of 180 ° until it forms a complete axial element group. According to the division, the elements are initially arranged in a radial sequence such that the dovetail receptacles between two filled dovetail connections or receptacles are not filled. The even number of element groups are regularly arranged opposite to the odd number of element packets. If an element is then introduced between two directly adjacent elements in succession, the polar halves of the same name of the directly adjacent elements repel one another. Thereby, repulsive forces that cancel each other act on the element to be introduced from both sides in the circumferential direction, so that the element to be introduced is not tilted (verkanten). Furthermore, firstly, in each case one guide plate can be positioned on the respective adjacent element, so that the element to be introduced cannot tilt between two adjacent elements and the elements already fixed to the rotor hub.

The invention allows other design approaches in addition to the illustrated embodiments.

Although the elements 1, 1 'are fixed to the rotor hub 5, 5' in the connecting sections 6, 6 'by means of a dovetail connection, it is readily possible to fix the elements to the rotor hub 50, 50' by screwing, welding, gluing or the like.

Although the pulling means in the present exemplary embodiment projects through the rotor hub 50, it is also conceivable that said pulling means is fastened to the rotor shaft 102 in such a way that the two pressure rings 43 are pressed against one another.

Although dovetail connections are used in the present embodiment, other slots and spring connections may be provided to connect the retaining means with the rotor hub as well.

Although the second embodiment of the holding device has no receptacle, this is easily possible. The receptacle can therefore usually also be introduced into the side of the holding device as a recess.

The side faces 16, 18 of the holding device 1, 1'; 16 ', 18' are formed in the present exemplary embodiment with an inward curvature. However, the side faces of the holding device can also be trapezoidal or formed in another shape, which at least preliminarily provides a tangible effect on at least one side face (16, 18; 16 ', 18') for the magnetic flux to be induced in the direction of the air gap between the rotor and the stator.

Although in fig. 7 the length l of the permanent magnet in the radial direction R is longer with the width b of the holding device 2 remaining the same in relation to fig. 6, it is also easily possible to vary the width b of the holding device 2 with a constant length l of the permanent magnet 4 in the radial direction R in order to influence the concentration effect or the magnetic flux density.

Although a synchronous machine is initially described herein, the holding device can also be used in a series of electric motors, such as dc motors and the like. Furthermore, the electric machine can be operated both as a motor and as a generator.

Although the recess 14 is trapezoidal in the first exemplary embodiment, it is also possible for the recess to be circular, concave, triangular, etc.

List of reference numerals

1. 1' element

2. 2' holding device

4 permanent magnet

6. 6' connecting section

8 first end face

10. 10' dovetail connection

12 second end face

13 connecting section

14 recess

16. 16' side surface

18. 18' side surface

20-hole-shaped accommodating part

20a incision

20b connecting mechanism

22-hole-shaped accommodating part

22a cut

22b connection mechanism

24. 24' notch

26 spoke

28. 28' first connecting piece

30 second connecting piece

32 south pole section

34 north pole section

36 adhesive

38 gap

40 support element

42 extrusion ring

44 cooling opening

50. 50' rotor hub

51 side surface

52 circular opening

54 end side of rotor hub

56 projection

100 rotor

102 rotor shaft

104 impeller of fan

200 stator

202 stator tooth

R radial direction

Circumferential direction of U ring

Axial direction A

length of permanent magnet in radial direction

b half width of holding device

Alpha angle between the first end face and the first/second side face

Claims (21)

1. An element (1; 1 ') of an electric machine, which element has a holding device (2, 2'; 2 ') with a first end face (8) having a connection section (6; 6') for fixing to a rotor hub (50; 50 ') and at least one permanent magnet (4) magnetized in a circumferential direction (U) of the electric machine, and a second end face (12) which is fitted into a recess (24, 24') of the holding device (2, 2 '; 2'), characterized in that the second end face (12) has a recess (14) in at least one of the permanent magnets (4).

2. Element according to claim 1, characterized in that the first end face (8) and the second end face (12) are connected by two at least segmented, preferably radially, inwardly curved side faces (16, 18; 16 ', 18').

3. Element according to claim 1 or 2, characterized in that a first connecting web (28, 28') extends parallel to the first end face (8).

4. An element according to any one of claims 1 to 3, characterised in that the holding device (2, 2 '; 2 "; 2" ') has a second connecting piece (30) extending parallel to the first end face (8) in the region of the connecting section (6; 6 ').

5. The element according to any one of claims 1 to 4, characterized in that the holding device (2, 2') has at least one spoke (26) extending transversely to the first end face (8).

6. The element according to claim 1 or 5, characterized in that the second end face (12) is at least sectionally formed outwardly curved.

7. The element according to claim 1 or 5, characterized in that the second end face (12) is at least sectionally formed curved inwards.

8. The element according to any one of claims 1 to 7, characterized in that the connection section (6; 6 ') is configured as a dovetail connection (10; 10').

9. Element according to one of claims 1 to 8, characterized in that a receptacle for at least one connecting means (20b, 22b) for the non-positive connection of a plurality of holding devices (2, 2 '; 2 "; 2"') is provided on at least one side (16, 18; 16 ', 18'),

wherein the connecting means (20b, 22b) are insulated with respect to the holding device (2, 2 '; 2').

10. Element according to claim 9, characterized in that said housing is an eyelet-like housing (20, 22) having a cut-out (20a, 22 a).

11. The element according to any one of claims 3 to 10, characterized in that the holding device (2, 2 '; 2 "; 2" ') has a north pole section (34) and a south pole section (32) which are connected to each other by the first connecting tab (28, 28 ').

12. Element according to any one of claims 1 to 11, characterized in that the holding device (2, 2 '; 2 "; 2"') is integrally formed.

13. An element with a holding device (2, 2 '; 2 "; 2"') and at least one permanent magnet (4) magnetized in the circumferential direction (U) of an electrical machine, in particular an element according to any of claims 1 to 12, the holding device having a first end face (8) with a connecting section (6, 6 ') for fixing to a rotor hub (50; 50'), and a second end face (12), the permanent magnet being fitted into a recess (24, 24 ') of the holding device (2, 2'; 2 "; 2" '), characterized in that the ratio of the length of the permanent magnet (4) in the radial direction (R) to the half-width of the holding device in the circumferential direction (U) is selected such that the holding device (2; 2') and/or the stator teeth reach magnetic saturation.

14. An element with a holding device (2, 2 '; 2 "; 2"') and at least one permanent magnet (4) magnetized in a circumferential direction (U) of the electrical machine, in particular according to any one of claims 1 to 13, the holding device has a first end face (8) and a second end face (12), the first end face having a connecting section (6; 6 ') for fastening to a rotor hub (50; 50 '), the permanent magnets being inserted into recesses (24, 24 ') of the holding device (2, 2 '; 2 '), characterized in that the connecting section (6) and the at least one permanent magnet (4) are designed such that, the face (4a) of at least one permanent magnet (4) facing the end side of the rotor hub (50; 50 ') is brought closer to the axis of rotation (D) of the rotor (100) than the lateral surface (51) of the rotor hub (50; 50').

15. An element having a holding device (2, 2 '; 2') with a first end face (8) having a connecting section (6; 6 ') for fixing to a rotor hub (50; 50') and at least one permanent magnet (4) magnetized in the circumferential direction (U) of an electric machine, in particular an element according to any one of claims 1 to 14, the permanent magnet being inserted into a recess (24, 24 ') of the holding device (2, 2'; 2 '), characterized in that the holding device (2, 2'; 2 ') is designed in such a way that a minimum cross section (B) of the holding device in the radial direction (R) is formed with a spacing which extends from the rotational axis (D) of the rotor (100) up to the side surface (51) of the rotor hub (50; 50') or less .

16. Element according to any one of claims 1 to 15, characterized in that the smallest cross section (B) has at most five times the thickness of the permanent magnet (4), preferably at most four times the thickness of the permanent magnet (4) and particularly preferably at most three times the thickness of the permanent magnet (4).

17. A component of an electrical machine, in particular a rotor (100), having a rotor hub (50; 50 ') and an element (1; 1 ') according to any one of claims 1 to 16, characterized in that a gap (38) is provided between two elements (1; 1 ') which are adjacent in a circumferential direction (U) and/or in an axial direction (A) of the component,

wherein the gap (38) is either an air gap or has a resilient material introduced therein.

18. Component of an electric machine, in particular a rotor (100), according to claim 17, having a rotor hub (50; 50 '), characterized in that at least two elements (1; 1') are spaced apart therebetween along an axial direction (a) by means of a support element (40).

19. Component of an electric machine, in particular a rotor (100), according to claim 17 or 18, having a rotor hub (50; 50 '), characterized in that a pressing ring (42) is respectively provided on the end sides (54) of the rotor hub (50; 50 ') in order to press the elements (1; 1 ') against one another in a force-fitting manner.

20. Component of an electrical machine, in particular a rotor (100), according to one of the claims 17 to 19, having a rotor hub (50; 50 '), characterized in that at least one of the supporting elements (40) and/or the rotor hub (50; 50') is composed of a non-ferromagnetic material.

21. An electrical machine, in particular a generator, characterized in that a component according to at least one of claims 17 to 20 is provided.