Permanent magnet for a rotor of an electric traction machine and method for mounting a rotor for an electric traction machine

Abstract

The invention relates to a permanent magnet (16) for a rotor (10) of an electric traction machine, which permanent magnet has a different concentration of rare earths in different regions (18, 20), having a marking (22) that can be read out by a detection device and on the basis of which the detection device can clearly determine an orientation of the permanent magnet (16), whereby the permanent magnet (16) can be installed in a recess (14) of a rotor base body (12) of the rotor (10) by means of an installation device on the basis of the determined alignment of the permanent magnet (16) in a defined installation position, which is predetermined as a function of an arrangement of the regions (18, 20) of different concentrations of rare earths in the permanent magnet (16).

Description

[0001] Permanent magnet for a rotor of an electric traction machine and method for mounting a rotor for an electric traction machine

[0002] The invention relates to a permanent magnet for a rotor of an electric traction machine and a method for mounting a rotor for an electric traction machine.

[0003] From DE 695 35 188 T2, a method for manufacturing a permanent magnet rotor is known, comprising a rotor yoke with a large number of laminated steel sheets, two N-magnetic poles on its outer circumference (where N is a positive integer), and slots for inserting electroplated permanent magnets for a field at the bases of the magnetic poles, spaced substantially equidistant from an opening for a rotatable shaft. In this method, rare-earth permanent magnets are inserted into the slots of the rotor yoke. The rotor yoke is then heated to a temperature above the Curie temperature of the permanent magnet, but below a temperature sufficient to maintain the material's performance for the permanent magnet. Finally, the heated rotor yoke is fitted to the rotatable shaft, and the permanent magnets are magnetized.

[0004] The object of the present invention is to provide a solution by which permanent magnets can be used in a rotor with a particularly low proportion of rare earth elements while maintaining particularly high rotor performance.

[0005] This problem is solved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description, and the figures. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0006] The invention relates to a permanent magnet for a rotor of an electric traction machine. The electric traction machine is specifically designed for use in a motor vehicle. In other words, the motor vehicle can be electrically driven by means of the electric traction machine. In addition to the rotor, the electric traction machine particularly comprises a stator relative to which the rotor can be rotated about an axis of rotation during operation. It is specifically provided that the rotor has a base body, which can, for example, be made of a laminated core. This rotor base body has at least one recess, and in particular several recesses, in which at least one permanent magnet, and in particular several permanent magnets, are to be received.A permanent magnet, also known as a permanent magnet, is a magnet made from a single piece of hard magnetic material that exhibits a constant magnetic field without requiring electrical power, unlike electromagnets. Permanent magnets are often made from metallic alloys. In this particular case, the permanent magnet is a rare-earth magnet, which contains varying concentrations of rare earth elements in different regions. A distinction is made between light rare earth elements (e.g., Nd, Pr) and heavy rare earth elements (e.g., Dy, Tr). The concentration of heavy rare earth elements (used for temperature stabilization) is deliberately varied. The term "rare-earth magnet" encompasses a group of permanent magnets that consist primarily of ferrous and rare-earth metals.Rare-earth magnets are characterized by their simultaneous high magnetic remanence flux density and high magnetic coercivity, resulting in high magnetic energy density. In particular, the permanent magnet in question is a neodymium-iron-boron (NdFeB) magnet. This allows for exceptionally high power densities, especially high remanence.

[0007] To protect the high-performance permanent magnets from demagnetization, heavy rare earth elements (HREs) are used. By adding heavy rare earth elements to the magnet base material for the permanent magnet and / or by introducing them via surface diffusion, the coercive field strength can be increased. In particular, materials with a higher proportion of heavy rare earth elements can be used as needed, especially in areas of the rotor that are subject to particularly high stresses due to operating conditions, such as a retarding field from the stator.

[0008] The use of heavy rare earth elements is costly and can be problematic due to issues such as political situations in mining countries, child labor, or environmental pollution. Adding heavy rare earth elements to the magnetic material of the permanent magnet reduces remanence and thus the maximum possible torque of the electric traction motor, or the performance of the permanent magnet itself. To provide a permanent magnet that combines the advantages of added rare earth elements with a particularly low concentration of these elements, the permanent magnet is designed to have a higher concentration of rare earth elements only in specific areas. Depending on these areas of increased rare earth concentration, the permanent magnet is to be installed in a defined position within a recess in the rotor body.This installation position is predetermined by the operating conditions in the rotor body and by the arrangement of the areas with varying rare earth concentrations within the permanent magnet. It is therefore essential that the permanent magnet is correctly oriented within the rotor during assembly. For this purpose, the permanent magnet is provided with a marking that can be read by a detection device, allowing the device to unambiguously determine the magnet's orientation. Based on this determined orientation, the permanent magnet can then be installed in the defined position within the rotor using an installation tool.In other words, the marking ensures that the orientation of the permanent magnet can be determined particularly easily and unambiguously, thus enabling reliable and correct mounting of the permanent magnet in the rotor using the mounting device. Providing the marking on the permanent magnet significantly minimizes the risk of incorrect orientation within the rotor. The marking can be geometric. For example, it can be provided by a geometric contour, such as a chamfer.

[0009] In a possible further development of the invention, the marking is provided by selectively adjusting the color of the permanent magnet. The marking is thus an optical marking characterized by the color of the permanent magnet. The color of the permanent magnet can be detected particularly easily using a camera in the detection device, allowing the orientation of the permanent magnet to be determined particularly easily and reliably based on its color.

[0010] In this context, it may be particularly suitable for the marking to be provided by selectively coloring the material from which the permanent magnet is manufactured. This means that a base material from which the permanent magnet is produced is colored in certain areas, for example, by adding color pigments, thereby providing the optical marking. Coloring the material ensures particularly high durability of the marking. Alternatively or additionally, it is possible for the marking to be provided by coating at least a portion of the permanent magnet's base body. This means that the permanent magnet's base body is manufactured, and then a specific area of ​​the base body is coated to provide the marking.This coating stands out from the base material, particularly in color, making the marking especially easy to read using the camera system. This coating can be, for example, an epoxy coating. Applying the coating allows for particularly simple and precise marking. Alternatively or additionally, the marking can be achieved by selectively creating a passivation layer on the permanent magnet. This means that the permanent magnet is manufactured, and then a specific area of ​​its surface is passivated. This passivated area of ​​the permanent magnet visually distinguishes itself from the surrounding surface, thus forming the marking. Creating the passivation layer allows the marking to be achieved without the use of color pigments.Passivation with different process / environmental parameters can lead to different colorations. This means that it is possible for all areas of the permanent magnet's surface to be passivated—especially under varying process / environmental parameters—and yet differentiation via color is still possible.

[0011] In a further possible embodiment of the invention, the permanent magnet comprises several segments stacked one on top of the other in a stacking direction, one of which projects beyond all adjacent segments in a lateral direction perpendicular to the stacking direction and / or remains behind all adjacent segments. For example, the segment can project beyond the adjacent segments on one side and remain behind the adjacent segments on another side. The permanent magnet can be tangentially segmented, particularly to reduce losses. These segments of the permanent magnet are usually glued together outside the rotor and then glued together before being inserted into the rotor. Because the segment projects beyond the adjacent segments, a raised or protruded section of the permanent magnet can be provided particularly easily.Because the segment is positioned behind all adjacent segments, a recess in the permanent magnet can be easily created. This recess can be easily detected mechanically using a probe, allowing the orientation of the permanent magnet to be determined mechanically. The probe is thus part of the detection device and is designed to read the aforementioned geometric marking in the form of the recess in the permanent magnet. Since the recess is created by arranging the segments relative to each other, the permanent magnet can be easily marked with the biometric identifier during its manufacture by simply aligning the segments accordingly.

[0012] In a further possible embodiment of the invention, the marking is arranged in a region of the permanent magnet where the concentration of heavy rare earth elements is higher than in at least one other region of the permanent magnet. Due to the increased concentration of heavy rare earth elements, the permanent magnet in this region is particularly well protected against demagnetization. Because the marking is located in the region of the permanent magnet where the particularly high concentration of heavy rare earth elements is present, the location of this region within the permanent magnet can be determined particularly easily by reading the marking using the detection device.As a result, the permanent magnet can be mounted in the rotor with exceptional reliability, ensuring that the area of ​​the permanent magnet with the highest concentration of heavy rare earth elements is located in a region of the rotor where, due to operating conditions, the risk of demagnetization is particularly high. This allows for a highly reliable and correctly oriented mounting of the permanent magnet within the rotor.

[0013] The invention further relates to a method for mounting a rotor for an electric traction machine. In this method, the orientation of at least one permanent magnet, as already described in connection with the permanent magnet according to the invention, is determined by a detection device based on its marking. Furthermore, the method provides that the permanent magnet is inserted into a recess of the rotor body in a defined installation position by means of an installation device, depending on the determined orientation. The defined installation position is predetermined by the arrangement of the areas with different rare earth concentrations in the permanent magnet. By reading the marking on the permanent magnet, the orientation of the permanent magnet can be determined simply and reliably with particularly high precision.As a result of precisely determining the orientation of the permanent magnet, the installation device allows the permanent magnet to be mounted with exceptional accuracy in the recess of the rotor body. This makes it possible to use permanent magnets in the rotor that only exhibit high concentrations of rare earth elements, particularly heavy rare earth elements, in areas subject to high stress. Therefore, it is not necessary to equip the entire permanent magnet with a uniform concentration of rare earth elements, especially heavy rare earth elements.Because the permanent magnet only exhibits elevated concentrations of rare earth elements, particularly heavy rare earth elements, in certain areas, the overall proportion of rare earth elements, especially heavy rare earth elements, can be very low, thus enabling particularly cost-effective production. An elevated or high concentration of rare earth elements means that the area in question has a higher concentration of rare earth elements than at least one other area of ​​the permanent magnet.

[0014] In a possible further development of the method, it is envisaged that the marking is optically detected using a camera on the detection device and / or mechanically detected using a button and / or a mask on the detection device. In particular, if the marking is provided by adjusting the color of the permanent magnet, the marking can be detected very easily and reliably using the camera, and the orientation of the permanent magnet can be determined based on the detected marking. Using the button, a geometric marking on the permanent magnet, such as an indentation or a protrusion, can be detected very easily and reliably, which in turn allows the orientation of the permanent magnet to be determined very easily.To determine the orientation of the permanent magnet, it can be guided through an opening in the mask of the detection device, allowing the position of a chamfer to be checked.

[0015] In this context, it can also be provided that the probe is arranged on a gripping device of the installation unit, whereby the orientation of the permanent magnet is determined by the probe when the permanent magnet is gripped by the gripping device. In other words, the permanent magnet can be gripped by the gripping device and its orientation checked by the probe simultaneously. This enables particularly fast and correct mounting of the permanent magnet to the rotor body. Depending on the orientation of the permanent magnet determined by the probe, the gripping device can position the permanent magnet on the rotor body particularly easily and precisely.The sensor thus allows for a particularly simple and precise determination of the orientation of the permanent magnet gripped by the gripping device in its gripped state. Further features of the invention may become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0016] The drawing shows in:

[0017] Fig. 1 shows a schematic sectional view of a section of a rotor base body of a rotor, wherein respective permanent magnets are arranged in recesses of the rotor base body;

[0018] Fig. 2 shows a schematic perspective view of a permanent magnet with a geometric marking; and

[0019] Fig. 3 shows a schematic perspective view of the permanent magnet with an optical marking.

[0020] In the figures, identical and functionally equivalent elements are provided with the same reference symbols.

[0021] Figure 1 shows a sectioned view of a rotor 10 for an electric traction motor of a motor vehicle. The rotor 10 comprises a rotor body 12, which in this case is formed from a laminated core. The rotor body 12 includes several recesses 14, each containing a permanent magnet 16. To protect the permanent magnets 16 from demagnetization, areas of the permanent magnets 16 susceptible to demagnetization are made insensitive to opposing fields from a stator of the electric traction motor by adding heavy rare earth elements. In this case, the respective permanent magnets 16 have a first region 18 and a second region 20, with a higher concentration of heavy rare earth elements in the first region 18 than in the second region 20.It is provided that the respective second region 20 is free of heavy rare earths or has a lower concentration of heavy rare earths than the at least one first region 18. The respective permanent magnets 16 thus exhibit different concentrations of rare earths, particularly heavy rare earths, in different regions. With such a configuration of the permanent magnets 16, featuring regions of varying rare earth concentrations, especially heavy rare earths, it is essential that the permanent magnets 16 are mounted in the correct orientation within the rotor body 12.To facilitate the correct alignment of the permanent magnets 16 in the rotor body 12 or in the recesses 14 of the rotor body 12 provided for the respective permanent magnets 16, each permanent magnet 16 is provided with at least one marking 22 that can be read by a detection device. Based on this marking 22, the detection device can uniquely determine the orientation of the respective permanent magnet 16. This allows the permanent magnet 16 to be installed in the rotor body 12 in a defined installation position, which is determined by an installation device based on the determined orientation of the respective permanent magnet 16. This installation position is predetermined by the arrangement of the areas 18, 20 with different rare earth concentrations in the permanent magnet 16.

[0022] Within the framework of a method for mounting the rotor 10, the orientation of the respective permanent magnet 16 to be mounted can thus be determined by means of the detection device based on the marking 22 and the permanent magnet 16 can be arranged in the defined installation position in the associated recess 14 of the rotor base body 12 by means of the installation device, in particular by means of a gripping device, depending on the determined orientation.

[0023] Figures 2 and 3 show permanent magnets 16, each marked with a different marking 22. Each of these permanent magnets 16 comprises a first region 18 with a higher concentration of rare earth elements, particularly heavy rare earth elements, and a second region 20 with a comparatively lower concentration of rare earth elements, particularly heavy rare earth elements. The proportion or concentration of heavy rare earth elements in the first region 18 can be adjusted, in particular, by diffusion of the surface layer or, when manufacturing the permanent magnet 16 from a plurality of segments 24, by applying a magnet segment with a higher concentration of heavy rare earth elements compared to the other segments 24.In the second area 20, the permanent magnet 16 has a lower proportion of heavy rare earths compared to the first area 18 and therefore exhibits a higher remanence in the second area 20 compared to the first area 18.

[0024] In the embodiment shown in Fig. 2, the marking 22 is provided in the form of a geometric marking. This can be designed as desired, for example, in the form of a chamfer. In the present case, the permanent magnet 16 shown in Fig. 2 is made from several segments 24 stacked on top of each other in a stacking direction 26. To provide the marking 22, one of the segments, which is subsequently designated with the reference numeral 28, is set back behind all adjacent segments 24 in a lateral direction 30 perpendicular to the stacking direction. Alternatively or additionally, to provide the geometric marking 22, one of the segments 24 can be provided to project beyond all adjacent segments 24 in the lateral direction 30.It is possible that the segment marked with reference numeral 28 has a length parallel to the lateral direction 30, which is equal to the length of at least one immediately adjacent segment 24 running in the lateral direction 30. Segment 28 can be arranged offset in the lateral direction 30 compared to the at least one further segment 24 immediately adjacent to it. This allows segment 28 to have the same total magnetic mass as the at least one adjacent segment, so that, despite the provision of the geometric marker 22, the permanent magnet 16 has a particularly large amount of magnetic mass. In the embodiment shown in Fig. 2, the marker 22 is thus provided by a geometric step. This geometrically designed marker 22 can be particularly well mechanically detected by means of a sensor of the detection device.The probe can be arranged, in particular, on a gripping device of the installation unit, whereby the orientation of the permanent magnet 16 can be determined by means of the probe during the gripping of the permanent magnet 16 by the gripping device. Thus, the orientation of the permanent magnet 16 can be checked or its position confirmed by means of the gripping device, which can be automated, via the probe. Alternatively or additionally, the geometric marking 22 can be designed such that, due to its shape, the permanent magnet 16 can only be installed in the correct orientation in the associated recess 14 of the rotor base body 12.

[0025] In the embodiment shown in Fig. 3, the marking 22 is provided by selectively adjusting the color of the permanent magnet 16. In this particular embodiment, the color of at least one segment 24 of the first region 18 is adjusted. This means that the marking 22 identifies the first region 18, which has a higher concentration of rare earth elements, particularly heavy rare earth elements, compared to the second region 20. Providing the marking 22 by adjusting the color of the permanent magnet 16, or its optics, allows the marking 22 to be optically detected by a camera in the detection device.For this purpose, the marking 22 can be provided, in particular, by coloring a portion of the material from which the permanent magnet 16 is made, for example, by coloring at least one segment 24. Alternatively or additionally, the marking 22 can be produced by coating at least a portion of a base body of the permanent magnet 16, in particular by coating at least one segment 24 associated with the first region 18, and / or by producing a passivation layer of the permanent magnet 16 in a portion of the area. In this case, at least one of the segments 24, in particular at least one of the segments 24 associated with the first region 18, can be provided with the passivation layer to produce the marking 22.

[0026] To ensure the correct orientation of the respective permanent magnets 16 in the rotor body 12 and thus to provide the respective marking 22, at least one area of ​​the respective permanent magnet 16 can be highlighted optically and / or geometrically, which enables particularly easy correct orientation of the respective permanent magnet 16. When providing the geometric marking 22, for example by shortening, in particular slightly shortening, one of the segments 24 of the permanent magnet 16 composed of several segments 24, this shortened segment 28 can be detected during automated assembly, in particular by means of a push button.

[0027] The optical marking 22 can be used as a safety feature during automated assembly by means of the camera device. The color of the permanent magnet 16 can be adapted by simple dyeing, by targeted influence during the creation of a passivation layer, or by applying a coating, in particular a colored coating, especially an epoxy coating. Overall, the invention shows how cost / functional optimization of magnets, in particular the permanent magnets 16, can be achieved by using magnet material combinations with poka-yoke.

[0028] Reference symbol list

[0029] 10 Rotor 12 Rotor base

[0030] 14 Exclusion

[0031] 16 permanent magnet

[0032] 18 first area

[0033] 20 second area 22 marking

[0034] 24 segments

[0035] 26 Stacking direction

[0036] 28 segments

[0037] 30 Side direction

Claims

Patent claims 1. Permanent magnet (16) for a rotor (10) of an electric traction machine, which has a different concentration of rare earth elements in different areas (18, 20), with a marking (22) readable by a detection device, by means of which the detection device can uniquely determine an orientation of the permanent magnet (16), whereby, by means of an installation device, the permanent magnet (16) can be installed in a recess (14) of a rotor body (12) of the rotor (10) in a defined installation position, which depends on an arrangement of the areas (18, 20) of different concentrations of rare earth elements in the permanent magnet (16).

2. Permanent magnet (16) according to claim 1 , characterized in that the marking (22) is provided by area-wise adjusting a coloration of the permanent magnet (16).

3. Permanent magnet (16) according to claim 2, characterized in that the marking (22) is provided by coloring a material from which the permanent magnet (16) is made in certain areas, and / or by coating at least a certain area of ​​a base body of the permanent magnet (16) and / or by generating a passivation layer of the permanent magnet (16) in certain areas.

4. Permanent magnet (16) according to one of the preceding claims, characterized in that the permanent magnet (16) comprises several segments (24) stacked on top of each other in a stacking direction (26), one of which a segment (28) extends in a lateral direction (30) perpendicular to the stacking direction (26) beyond all adjacent segments (24) and / or remains behind all adjacent segments (24).

5. Permanent magnet (16) according to one of the preceding claims, characterized in that the marking (22) is arranged in a region (18) of the permanent magnet (16) in which a concentration of heavy rare earths is higher than in at least one further region (20) of the permanent magnet (16).

6. Method for mounting a rotor (10) for an electric traction machine, in which an orientation of at least one permanent magnet (16) according to one of the preceding claims is determined by means of a detection device based on the marking (22) and the permanent magnet (16) is inserted into a recess (14) of a rotor base body (12) of the rotor (10) by means of an installation device in a defined installation position, which is predetermined depending on an arrangement of the areas (18, 20) of different concentrations of rare earths in the permanent magnet (16), depending on the determined orientation.

7. Method according to claim 6, characterized in that the marking (22) is optically detected by means of a camera device of the detection device and / or the marking (22) is mechanically detected by means of a button and / or a mask of the detection device.

8. Method according to claim 7, characterized in that the button is arranged on a gripping device of the installation device, whereby the orientation of the permanent magnet (16) is determined by means of the button when gripping the permanent magnet (16) by means of the gripping device.

Images