WO2011104265A2

WO2011104265A2 - Electric machine comprising a rotor device and rotor device with an optimised magnetic flux and method for operating said electric machine

Info

Publication number: WO2011104265A2
Application number: PCT/EP2011/052661
Authority: WO
Inventors: Juergen Fridrich; Julien Roger; Kurt Reutlinger
Original assignee: Robert Bosch Gmbh
Priority date: 2010-02-26
Filing date: 2011-02-23
Publication date: 2011-09-01
Also published as: DE102010002390A1; WO2011104265A3

Abstract

The invention relates to a method for operating an electric machine (10), and to an electric machine (10) comprising a stator and a rotor (20), especially a hybrid-excited rotor (20), and a rotor device (1), especially a rotor plate, for a generator (10) of a motor vehicle, especially for a hybrid-excited generator, comprising a base body having a plurality of magnetic pockets (41) and embodied in such a way as to guide a magnetic flux induced in permanent magnets (24, 25) arranged in the magnetic pockets (41). At least one recess (2) is provided in the region of a main magnetic flux, for influencing said main magnetic flux.

Description

description

title

Electric machine with rotor device and rotor device with optimized magnetic flux and method for operating the electric machine

The invention relates to a rotor device, in particular a rotor plate, for a generator of a motor vehicle, in particular for a claw pole generator, according to the preamble of claim 1.

Furthermore, the invention relates to an electrical machine according to the preamble of claim 5.

In addition, the invention relates to a method for operating an electric machine according to the preamble of claim 8.

State of the art

The invention relates to an electrical machine, such as a motor vehicle generator, for converting mechanical energy into electrical energy with a rotor having a rotor device, and a method for operating a motor vehicle generator according to the preamble of the independent claims.

The present invention relates to electrical machines such as motor vehicle generators, in particular motor vehicle generators such as AC generators with rectifiers for DC voltage supply of vehicle electrical systems.

From the prior art alternators for motor vehicles are known. Such alternators are usually designed as Klauenpolgeneratoren. In these generators, a field winding in the rotor is cylindrical around a core. The rotor includes two, among others Claw pole, on whose outer circumference in each case extending in the axial direction Klauenpolfinger are arranged. Both claw-pole plates are arranged around the rotor such that their claw-pole fingers extending in the axial direction alternate at the periphery of the rotor as north and south poles. This results in magnetically required Klauenpolzwischenräume between the oppositely magnetized Klauenpolfingern, which extend slightly oblique to an axis of the electric machine because of the tapering towards their free ends claw-pole fingers.

Further hybrid-excited generators with entrepchendem rotor are known from the prior art. The rotors comprise rotor devices, which are designed, for example, as rotor laminations. Such rotor laminations comprise magnet pockets for accommodating permanent magnets. In addition, the rotor plate is designed to conduct a magnetic flux. Such rotor laminations are known from the prior art.

For example, WO 2004/017496 A2 and US 2006/0119206 disclose rotor laminations which have recesses. The recesses are configured to receive fasteners to interconnect a plurality of rotor laminations into a package. In addition, further recesses are formed near the rotor shaft.

For example, DE 10 207 025 971 A1 also discloses electrical machines which operate as a hybrid-excited machine. The hybrid-excited machine is controlled by the excitation current in the rotor winding. The stator winding is designed for a higher number of poles. If an exciting current is fed, resulting in a number of poles that coincides with the stator winding, a strong voltage in the stator winding of the machine is induced and the machine can feed a power to the electrical system. If, on the other hand, the exciter current is reversed in its direction, the smaller number of poles is produced in the rotor, which in the stator winding leads to no voltage being induced and the machine outputting no power. However, this leads to the stator yoke in the machine being dimensioned to the smaller number of poles. A magnetic flux in the stator yoke is significantly larger at the smaller number of poles than at the higher number of poles. Thus, the machine requires a significantly larger yoke for a good control of the performance. For operation under full load, a significantly lower yoke would be sufficient. Disclosure of the invention

The electric machine according to the invention with the rotor device according to the invention and the inventive method for operating the electric machine with the features of the corresponding main claim or the corresponding independent claim have the advantage over the prior art that the rotor plate is adapted to the magnetic flux guide within the rotor. By suitable recesses of the magnetic flux at a smaller number of poles, that is at a Abregulation of the generator limited. By limiting the flow in the rotor at the smaller number of poles, a better regulation of the generator is realized and / or the stator yoke is smaller interpretable. In addition, the recesses in the rotor save material and weight. In this way, the total weight of the rotor is reduced. The recesses serving as magnetic flux limiting means are arranged in a main flux of a magnetic flux through the rotor. The main flow takes place between the magnet pockets, more precisely between the permanent magnets. Wherein the flow passes through the rotor sheet material in an area around the pockets. The

Recesses reduce the area through which the magnetic flux passes, so that a limitation by the material recess and the associated cross-sectional constriction is realized. The measures listed in the dependent claims are advantageous

Further developments and improvements of the predetermined in the independent and independent claims devices possible.

In an advantageous embodiment, it is provided that the recess in the direction of a rotor shaft recess between the magnet pocket and the

Rotor shaft recess is arranged. The electrically generated magnetic flux extends around the magnetic pockets and thus also between the magnetic pockets and a centric rotor shaft recess. Preferably, the recess is formed closer to the magnet pocket, since a greater influence on the magnetic flux of the permanent magnets is effected here. With a positive excitation current, the main magnetic flux is near the magnet pocket. With regard to the formation of the recesses is to pay attention to a sufficient cross section, the one sufficient magnetic flux allows. In addition, a sufficient distance between magnet pocket and recess for reasons of strength to ensure.

In the case of a negative excitation current, the excitation current acts field-amplifying in the permanent magnet. This directly affects the overall flow in the rotor device. The recess is designed in this case to counteract the rise of the magnetic field.

It is advantageous that a distance between the recess and the magnet pocket is less than or equal to a width of the magnet pocket. It has been found that this distance ensures optimum magnetic flux limitation with sufficient strength. The radial distance range has been determined by means of complex finite element calculation. In particular, an advantageous distance range is about 50% to 30% of the pocket width. At the ends of the recess, the distance between the recess and the magnet pocket is less than about 30% of the width of the magnet pocket.

In an advantageous embodiment, it is provided that a width of the recess is smaller than or equal to the width of the magnet pocket. Also, this width has been found to be optimal with respect to a magnetic flux with sufficient strength of the rotor blade by means of finite element methods. There are provided in preferred embodiments, a plurality of recesses. The recesses are the same in further embodiments. In yet other embodiments, the recesses are formed differently shaped. Preferably, the recesses are formed adjacent to rotor grooves different from the recesses under the centrally seated magnet.

In an electric machine according to the invention comprising a stator and a rotor, in particular a hybrid-excited rotor, it is provided that the rotor comprises at least one rotor device according to the invention described above. Preferably, a plurality of rotor devices are provided.

In a method according to the invention for operating an electrical machine with permanent magnets arranged in magnetic pockets of a rotor, provision is made in particular for a magnetic flux between the permanent magnets to have a maximum magnetic flux through a material taper in the region of the magnetic flux is limited. The material taper is realized by means of recesses. Recesses are formed as depressions or as passage openings.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it:

1 schematically shows a longitudinal section through an alternator for motor vehicles with a hybrid-excited rotor in Polwechselanordnung,

2 schematically shows a circuit diagram of a bridge circuit of a 5-phase stator in a configuration as a five-pointed star,

3 is a schematic diagram of a rotor device designed as a rotor plate with recesses in a first embodiment,

4 shows schematically the rotor plate according to FIG. 3 with a reference stress drawn in at a load of approximately 20,000 revolutions per minute, FIG.

5 schematically shows a rotor plate designed as a rotor device with recesses in a second embodiment with marked magnetic flux image at full load and positive excitation current,

6 shows schematically the tube sheet according to FIG. 5 with a drawn magnetic flux diagram at full load and negative exciter current,

7 shows schematically a further embodiment of a rotor device designed as a rotor plate,

8 schematically shows the rotor plate according to FIG. 7 with magnetic flux drawn in at full excitation with 5 A, FIG. Fig. 9 shows schematically the rotor plate of Fig. 7 with marked magnetic flux at a counter-excitation with -5 A and

Fig. 10 shows schematically the rotor plate of FIG. 7 with marked reference voltages at a load of about 20,000 revolutions per minute.

Description of the embodiment

In Fig. 1 is a section through an alternator 10 for motor vehicles is shown. This has inter alia a two-part housing 13. This consists of a first bearing plate 13.1 and a second bearing plate 13.2. The bearing plate 13.1 and the bearing plate 13.2 take in a stator 16, with an annular stator lamination 17, in which inwardly open and axially extending grooves 19, a stator winding 18 is inserted, the annular stator 16 surrounds with its radially inwardly facing surface electromagnetically excited rotor 20, which is designed as a hybrid-excited rotor. The stator 16 acts in this case via a working air gap with the rotatably mounted in the stator 16 rotor 20.

The rotor 20 has over its circumference in a predetermined sequence a plurality of north poles N and south poles S, which are formed by polbildende permanent magnets 24, 25, as well as by the exciter winding 29. In this case, the number of poles of the rotor 20 can be reversed depending on the strength and direction of an excitation current in the field winding 29. The rotor 20 is constructed from a magnetically conductive body which can be formed as a laminated core with a plurality of rotor devices 1 designed as a rotor plate. The rotor core 21 is preferably laminated in the axial direction with a plate thickness between 0.1 mm and 2.0 mm. Below 0.1 mm, the resistance of the laminated core 21 against

Centrifugal forces too low. Above 2.0 mm, the reduction of the eddy current losses on the outer surface of the rotor 20 is no longer sufficient, so that the permanent magnets 24, 25 installed in the rotor can be damaged or demagnetized. The axial length of the rotor laminated core 21 preferably corresponds to the axial length of the annular stator lamination 17, or is for a tolerance compensation up to 2 mm longer or shorter than the annular stator lamination 17. The laminated core 21 is preferably held together by welds. It can also welds and rivets, or knobs be used. The excitation winding 29 is in this case designed as a diameter coil and is located in recessed grooves 40 which are punched out of the laminated core 21. The excitation winding 29 may, for. B. as a flyer wrap (double flyer) are wrapped directly into the rotor core 21 lamination. Furthermore, areas 41 are recessed in the rotor laminated core, in which permanent magnets 24, 25 can be used. According to the invention, the magnets 24, 25 are inserted into stamped (magnetic) pockets 41 in the rotor laminated core 21. This makes it possible to absorb the centrifugal forces by the geometric shape of the pockets 41 and thereby ensure a secure hold of the magnets 24, 25 on the rotor 20. As a magnetic material, a material with a remanence of greater than 1 T proves to be particularly advantageous. These magnetic properties in particular have permanent magnets 24, 25 of rare earths. The magnets 24, 25 are in this case installed in the rotor 20 such that they generate a substantially radial field. This field then passes from the rotor 20 through the air gap in the stator core and thus forms upon rotation of the rotor 20, a voltage induction in the windings of the rotor 20th

The rotor 20 is rotatably supported in the respective end shields 13.1 and 13.2, respectively, by means of a (rotor) shaft 27 and one respective rolling bearing 28 located on each side of the rotor. It has two axial end faces, on each of which a fan 30 is attached. These fans 30 essentially consist of a plate-shaped or disk-shaped section, starting from the fan blades in a known manner. These fans 30 serve to allow an air exchange between the outside and the interior of the electric machine 10 via openings 48 in the end shields 13.1 and 13.2. For this purpose, the openings 48 are provided at the axial ends of the bearing plates 13.1 and 13.2, via which 30 cooling air is sucked into the interior of the electric machine 10 by means of the fan. This cooling air is accelerated radially outward by the rotation of the fans 30, so that they can pass through the cool air-permeable winding heads 50 on the drive side and 51 on the electronics side. By this effect, the winding heads 50, 51 are cooled. The cooling air takes after passing through the winding heads 50, 51, or after the flow around these end windings 50, 51 a way radially outward through openings not shown. In Figure 1 on the right side there is a protective cap 47, which protects various components against environmental influences. Thus, this protective cap 47 covers, for example, a slip ring assembly 49, which supplies a field winding 29 with exciting current. Around this slip ring assembly 49 around a heat sink 53 is arranged, which acts here as a plus heat sink, are mounted on the positive diodes 59. As so-called Minus heat sink acts the bearing plate 13.2. between the bearing plate 13.2 and the heat sink 53, a connection plate 56 is arranged, which in the bearing plate 13.2 attached minus diodes 58 and not shown in this illustration plus diodes 59 in the heat sink 53 in the form of a bridge circuit 69 interconnects.

FIG. 2 shows an AC generator 10 with five phase-forming winding phases 70, 71, 72, 73, 74 on the basis of a circuit diagram. The totality of all winding strands 70, 71, 72, 73, 74 forms the stator or stator winding 18. The five phase-forming winding strands 70, 71, 72, 73, 74 are connected to a basic circuit as a five-pointed star (Drudenfuß), wherein each in the strands of the star interconnected strands enclose an angle of about 36 ° el. At the points of interconnection of the prongs 80, 81, 82, 83, 84 of the five-pointed star, the rectifier bridge circuit 69 is connected. The winding strands are interconnected as follows. The winding sub-string 70 is connected to the winding sub-string 71 at the connection point 80. The winding strand 71 is connected to the winding strand 72 at its opposite end at the connection point 81. The winding strand 72 is connected to the winding strand 73 at its opposite end at the connection point 82. The winding sub-string 73 is connected to the winding strand 74 at its opposite end at the connection point 83. The winding strand 74 is connected at its opposite end at the connection point 84 with the winding strand 70. The Verschaltungspunkte are preferably axially on or adjacent to the electronics side winding 51 to realize the shortest possible Verschaltungswege. For this purpose, the connecting wires of the winding strands 70, 71, 72, 73, 74 of a connection point 80, 81, 82, 83, 84, which are to be interconnected, preferably emerge from grooves 19 which are directly adjacent in the circumferential direction. The connection points 80, 81, 82, 83, 84 of the winding strands 70, 71, 72, 73, 74 are connected to a separate bridge rectifier 69, which is composed of five minus diodes 58 and five plus diodes 59. On the DC voltage side, a voltage regulator 66 is connected in parallel, which regulates the voltage of the generator by influencing the current through the exciter winding 29. The voltage regulator may additionally have a connection to the rectifier in order to measure the voltage drop across a diode and to determine therefrom the current rotational speed of the generator. The electrical system is shown schematically by the vehicle battery 61 and by vehicle consumers 62. It is also possible for better control, the excitation winding 29 by means of four power amplifiers, which are connected to an H-bridge circuit to control. This makes it possible to impress in the excitation winding 29 and negative excitation currents. This gives advantages in Reference to the Leistungsabregelungsverhalten the generator, or in relation to the control speed, as well as for fast de-energizing negative voltages to the exciter winding 29 can be applied. Of course, other phase numbers and Verschaltungsarten can be displayed in a known manner. Particularly noteworthy are three-phase systems in star or delta connection.

Fig. 3 shows schematically a rotor formed as a rotor plate 1 for a laminated core 21 with grooves 40 for the field winding according to FIG. 1 and recesses 2 in a first embodiment. The rotor plate is formed as a circular disc which is formed like a tab at its peripheral edge. Magnetic pockets 41 for receiving the permanent magnets 24, 25 shown in FIG. 1 are formed in the tab-like areas. In the illustrated embodiment, 14 tab-like areas are formed, wherein six magnetic pockets 41 are provided. In the radial direction, that is to say towards a circular disk center point, recesses 2 for limiting a main magnetic flux between the permanent magnets 24, 25 shown in FIG. 1 are formed underneath the magnetic pockets 41. The two central recesses 2a in the 12 o'clock position and 6 o'clock position are trapezoidal in shape. The four other recesses 2b on the left side and the right side to the trapezoidal recesses 2a are slit-like formed as a slot. The recesses 2 are designed and arranged such that the magnetic flux through the permanent magnets 24, 25 is limited to a maximum value. The flux guiding area under the magnetic pockets 41 is restricted by the recesses 2 so that the magnetic flux through the narrowed

Cross section and the saturation induction of the sheet material is determined. At full electrical excitation, the exciter flux and the permanent magnet 24, 25 work in the opposite direction. The magnetic flux through the permanent magnet 24, 25 is weakened in this case. The induction in the laminated core at the side of the recesses (necking areas) is still below the

Saturation induction. Only with a counter-excitation of the generator, the flooding of the exciter winding and the magnets work in the same direction. The induction in the magnet increases until the saturation of the necking areas is achieved and a further increase of the induction in the magnet or the magnetic flux through the magnet is prevented. Accordingly, a width B is the

Recess 2 radially below the magnetic pockets in a range between about 40% and 100% of the pocket width T of the magnet pockets 41, preferably between 40% and 100%. At the right and left end of the recesses 2 is the distance D. between the recesses 2 and the magnetic pockets 41 at approximately less than or equal to 30% of the width of the magnets or the magnetic pocket 41. The recesses 2a, 2b have, as described above, different geometries. This is necessary in the embodiment for reasons of strength and flow control. For this reason, the recesses 2 among the magnet pockets 41 adjacent to the tube grooves 40 are different in size from the recesses 2 among the centrally seated magnets at 6 o'clock and 12 o'clock positions, respectively.

FIG. 4 schematically shows the rotor plate according to FIG. 3 with a reference stress drawn in at a load of approximately 20,000 revolutions per minute. The comparison voltage is indicated by the different hatching, wherein discrete reference voltage ranges are shown. It is clear from FIG. 4 that the recesses 2 have no significant influence on the strength of the rotor sheet at maximum load. Because the comparison stresses in the area around the recesses, which are shown here as a grid-like hatching, are essentially in a common reference voltage range. The comparison stress regions around the recesses 40, in particular on the end regions of the recesses 40 arranged inside the rotor lamination, are substantially unchanged with respect to a rotor lamination without recesses 2. The maximum load values, that is, the maximum reference voltages thus occur at the approximately triangular recesses 40 for the coils in the 3 o'clock and 9 o'clock positions, namely at the two corner regions arranged adjacent to the rotor shaft recesses 5.

5 schematically shows a rotor device 1 designed as a rotor plate with recesses 2 in a second embodiment with a drawn magnetic flux diagram at full load and positive exciter current. The strains due to the magnetic flux are indicated by corresponding hatching subdivided into magnetic flux areas. The recesses 2 are formed as circular passage openings. The representation of the rotor device 1 according to FIG. 5 is shown rotated in relation to the illustration according to FIGS. 3 and 4 by 90 °. These are arranged in a region in which a minimal magnetic flux flows without the recesses 2. By the recess 2 thus the magnetic flux is hardly affected at full excitation. The main flow of the rotor device 1 is reduced only slightly with positive excitation, so that the performance of the rotor device is maintained under full load. Fig. 6 shows schematically the rotor plate of Fig. 5 with marked magnetic flux image at negative excitation current. The strains caused by the magnetic flux are here also identified and, analogously to FIG. 5, subdivided into magnetic flux regions by corresponding hatching. Same hatching area are hatched the same. Opposite a rotor plate without recesses 2 here is the

Magnetic flux between the magnet pocket 41 and the recess 2 is reduced, so that here an effective limitation of the magnetic flux is effected.

FIG. 7 shows schematically a further embodiment of a rotor device 1 designed as a rotor plate similar to FIGS. 3 and 4 in a rotation through 90 °

Presentation. The recesses 2 are formed here as slots or slots. The central recesses 2a are slightly larger than the laterally adjacent oblong holes 2b. With this embodiment, the magnetic flux image shown in Fig. 8 results.

Fig. 8 shows schematically the rotor plate of Fig. 7 with marked magnetic flux at a full excitation of 5 A. At full excitation with 5A results in no magnetic flux limit at the end portions of the recesses 2. Here, the magnetic flux is not limited. By forming the recesses 2 as slots, as in Fig. 8 and also in Fig. 9, one obtains more favorable conditions than in circular

Recesses 2 according to FIGS. 5 and 6, as can be seen clearly from the magnetic flux regions.

Fig. 9 shows schematically the rotor plate of FIG. 7 with marked magnetic flux at a counter-excitation with -5 A. Here, the effective limitation of

Magnetic flux in the region of the end portions of the recesses 2 clearly.

10 schematically shows the rotor plate according to FIG. 7 with reference stresses shown at a load of approximately 20,000 revolutions per minute. It can be clearly seen from this tension diagram that the appropriate

Forming the recesses 2 no significant impairment in terms of strength at full load in the rotor plate is formed.

Claims

claims

1. Rotor device (1), in particular a rotor plate, for a generator (10) of a motor vehicle, in particular for a hybrid-excited generator, comprising a base body with a plurality of magnetic pockets (41) arranged to conduct one of the magnet pockets (41) permanent magnets ( 24, 25)

Magnet flux is formed, characterized in that

in the region of a main magnetic flux at least one recess (2) for

Influencing the magnetic main flux is provided.

2. rotor device (1) according to claim 1, characterized in that the recess (2) in the direction of a rotor shaft recess (5) between the magnet pocket (41) and the rotor shaft recess (5) is arranged.

3. Rotor device (1) according to claim 1 or 2, characterized in that a distance (D) between the recess (2) and the magnet pocket (41) is less than or equal to a width (T) of the magnet pocket (41).

4. Rotor device (1) according to one of the preceding claims 1 to 3, characterized in that

a width of the recess (2) is less than or equal to the width (T) of the magnet pocket (41).

5. Electrical machine (10) comprising a stator and a rotor (20), in particular a hybrid-excited rotor (20), characterized in that the rotor (20) comprises at least one rotor device (1) according to one of the preceding claims 1 to 4.

6. Electrical machine (10) according to claim 5, characterized in that in the magnetic pockets (41) permanent magnets (24, 25) are arranged, which cooperate with corresponding excitation coils (29).

7. Electrical machine (10) according to claim 5 or 6, characterized in that

the permanent magnets (24, 25) are magnetized in the radial direction.

8. A method for operating an electrical machine (10) with in magnetic pockets (41) of a rotor (20) arranged permanent magnet (24, 25), characterized in that

a magnetic flux through the permanent magnet (24, 25) is limited to a maximum magnetic flux through a material taper in the region of the magnetic flux.