Title of Invention

A STATOR FOR AN ELECTRIC MACHINE

Abstract

In the case of a stator (11) for an electric machine, in particular for a starter motor in motor vehicles, having an exciter winding (22) which is laid in a meander-shaped manner around the poles (14,14') and has a plurality of turns, in order to create great configura- tion freedom for the exciter winding (22) together with a sufficiently high copper factor and an acceptable axial winding overhang, each turn of the exciter winding (22) is designed as a bundle conductor comprising a plurality of parallel-wound round wires (23), which lie next to one another at the ends of the poles (14,14'). The round wires (23) of each bundle conductor run obliquely with respect to the yoke axis in the region from the end of a preceding pole (14) as far as the end of the following pole (14') and are twi.sted with one another through at least 180º here (Figure 1).

Full Text

ROBERT BOSCH GMBH, 70442 Stuttgart Stator for electric machine Prior art The invention is based on a stator for an electric machine, in particular for a starter motor in motor vehicles, of the generic type defined in the preamble of Claim 1. In a known stator of this type (DE 19 08 323 Al) , the exciter winding, which is laid in a meander-shape manner around the poles, is shaped to form an intrinsically closed, curved coil having axially parallel coil sections and two electrical coil connections. The semicircular winding overhangs, which connect the axially parallel coil sections, are situated at end cutouts in the poles, with the result that the axial length of the coil practically coincides with the axial length of the yoke or pole ring. The space between the succeeding poles is completely filled with the axially parallel coil sections. In the production of the meander-shaped coil, an annulus-type coil is taken as a starting point, this coil being banded in a conventional manner and bent to form the meander-type coil. The poles are releasably connected to the yoke. During the assembly of the stator, initially only every second pole is connected to the yoke and afterwards the meander coil is inserted, each second winding overhang of the coil being inserted into the end cutouts in the poles. After this, the remaining poles are inserted into the yoke and axially displaced until their end cutouts engage oyer the remaining winding overhangs. Advantages of the invention The stator according to the invention, having the characterizing features of Claim 1, has the advantage that by using individual round-wire conductors, the exciter winding affords greater freedom for configuration . The pole core can be designed to be higher, as a result of which the winding can spread out more radially and is not built up, axially to such a great extent. Transposing the individual round wires within a bundle conductor, which constitutes a turn, strengthens the winding, with the result that the latter is sufficiently stiff and robust to be able to be produced outside the stator and subsequently inserted into the yoke. The exciter winding according to the invention has a copper factor which is only slightly lower than an exciter winding in which the exciter poles are wound directly with round wire, together with a clear manufacturing advantage by virtue of prefabrication outside the yoke. In addition, the outlay for connecting up a meander-type winding, which has only one winding beginning and one winding end, is distinctly lower than with directly wound exciter poles, where all of the winding connections of the individual poles have to be connected up. Since the round wires lie parallel next to one another at the outer ends of the poles, the winding overhang is kept within acceptable limits and is only 1.5 - 1.7 times greater than in the case of the exciter poles being wound directly. Advantageous developments and improvements of the stator specified in Claim 1 are possible by virtue of the measures cited in the further claims. According to a preferred embodiment of the invention, the transposition of the round wires between two succeeding poles is performed at an angle of rotation of 180° or a whole-number multiple of 180°, At an angle of rotation of 180° or an odd multiple of 180°, the round wires lying next to one another at the ends of succeeding poles exchange places at succeeding poles, and at an angle of rotation of an even multiple of 18 0° they maintain their position at all poles, Transposition of the round wires through 180° already suffices to achieve sufficient stiffness of the meander-type winding and to be able to prefabricate the latter outside the stator and insert it into the stator. For technical winding reasons, the transposition of the round wires of a bundle conductor within two intermediate regions, which directly succeed one another in the winding direction between two poles is, according to an advantageous embodiment of the invention, carried out in opposite senses through the same angle of rotation, that is to say, for example, once through 180° in the clockwise direction and then through 180° in the anticlockwise direction. According to a preferred embodiment of the invention, the poles are connected in a consecutive seqpience first fixedly and then releaseably to the yoke, and the yoke and poles are combined as a stack from a multiplicity of fully stamped laminate sections. This structural measure keeps the material loss during stamping extremely low, above all when the rotor is simultaneously stamped out in the fully stamped section. Drawing The invention is explained in more detail in the following description using exemplary embodiments which are illustrated in the drawing, in which: Figure 1 shows a partially diagrammatic and cut-open, perspective illustration of a starter motor for motor vehicles. Figure 2 shows a perspective illustration of a yoke section of the starter motor in Figure 1, with a pole removed from the yoke. Figure 3 partially shows an end view of a stator for a starter motor according to a further exemplary embodiment, Figure 4 shows a perspective illustration of a winding apparatus to demonstrate the winding structure of the exciter winding of the starter motor in F i gu r e s 1 - 3, Figure 5 shows a perspective illustration of a winding mask for receiving the winding overhangs of the exciter winding in Figure 4/ Figures 6 and 7 each show a section along the line VI-VI and VII-VII, respectively, in Figure 4. Description of the exemplary embodiments The starter motor, perspectively illustrated in Figure 1, for a motor vehicle as an example of any desired electric machine has a stator 11, which is fastened in a housing (not illustrated here), and a rotor 12, which revolves in the stator and is seated in a manner fixed against rotation on an output shaft which is mounted in the housing and is not illustrated here. The stator 11 has a hollow-cylindrical yoke 13, also called pole ring, from which a number of poles 14,14' project radially inwards. Half of all the poles, designated here by 14, are each designed in one piece with the yoke 13, while the other half of the poles 14' can be released from the yoke 13. A fixed pole 14 always alternates with a releasable pole 14' in the peripheral direction of the yoke 13. Each pole 14,14' consists in a known manner of a pole core 15 and a pole shoe 16, which is integrally formed on the free end of the pole core 15, and extends over the axial length of the yoke 13. In the case of the releasable poles 14', the pole core 15 bears an insertion foot 17 on its end facing away from the pole shoe 16, which insertion foot can be pushed in a positively locking manner into an axial foot guide 18 in the yoke 13. In the case of the stator 11 according to Figures 1 and 2, the insertion foot 17 and foot guide 18 are embodied with a known dovetail structure, whereas in Figure 3 the insertion foot 17 is realised by two paral lel ribs 19 having a circular profile and the foot guide 18 is realised by two parallel slots 20 having a circular cross-section in the yoke 13. As is clearly discernible particularly in Figure 3, the internal wall 131 of the yoke is in each case flattened over the tangential width of the pole core 15 of the releasable poles 14', with the result that the pole core 15 bears in a planar manner against the internal wall 131 of the yoke. This produces a large crossover area for the magnetic flux with a very small air gap. The yoke 13, the poles 14,14 with the pole core 15 and pole shoe 16 as well as the rotor 12 are produced from laminations using stamping technology, a lamella of the yoke 13 having the fixed poles 14, a lamella of all the releasable poles 14' and a lamella of the rotor 12 having slotting 121 being produced in a single full section. The individual lamellae are then respectively combined to form a laminate stack. By virtue of the low-waste stamping technology of the full sections, it is possible to design the pole shoes 16 with favourable contours for guiding the magnetic flux, and also to provide cutouts 21 for accommodating threaded screws with little outlay. An exciter winding 22 having a plurality of turns in one or more layers is laid in a meander-shaped manner around the poles 14,14', which exciter winding runs around succeeding poles 14,14' alternately at ends which face away from one another and point axially outwards, and extends between the poles 14,14' along the internal wall 131 of the yoke obliquely with respect to the yoke axis. Each turn of the exciter winding 22 is formed by a so-called bundle conductor, which consists of a plurality of round wires 23 which are next to one another on the ends of the poles 14,14' radially with respect to the yoke axis. In the region extending from the end of a preceding pole 14 as far as the end of the following pole 14' , the round wires 23 are twisted or transposed with one another through 180° in such a way that the individual round wires 23 of a bundle conductor exchange their position on the end of the preceding pole 14 relative to the position on the end of the following pole 14' • On the way to the next pole 14 in the winding direction, the individual round wires 2 3 in the bundle conductor are twisted in the opposite sense, that is to say through -180°, with the express result that they again assume their previous position. This transposition through 180° and through -180° of the individual round wires 23 within the bundle conductor is consecutively repeated in the region between the poles 14,14' and, respectively, in the region between the poles 14',14. At the beginning and at the end of each turn, the individual round wires 2 3 are soldered or welded to form a respective conductor connection. In order to illustrate the structure of the exciter winding 22 which is sketched in Figure 1 and is prefabricated outside the stator 11 as a meander-shaped coil. Figure 4 diagraunmatically illustrates the winding apparatus for the exciter winding 22. A winding drxim 26 bears on its periphery fingers 24 which are arranged offset at both end edges and whose number corresponds to the niimber of poles 14,14' in the stator 11. As an example, an exciter winding 22 for a six-pole stator 11 is illustrated in Figure 4. On each end edge 2 61 and 262 of the winding drum 26, in each case three fingers 24 are arranged offset by 12 0° with respect to one another over the periphery of the drum. Each finger 24 has a guide face 241 for receiving the round wires 23, onto which a plastic mask 25, such as is illustrated in Figure 5, can also be placed. The plastic mask 25 is designed in such a way that it can be pushed with a U-shaped web 251 axially onto the outer end of the poles 14,14', the web 251 being pushed with two limbs 251' and 251" onto those surfaces of the pole cores 15 which extend in the axial direction. On opposite ends radially with respect to the yoke axis, the web 251 in each case bears an axially projecting flange 252' and 252". The winding overhang of the exciter winding 22 is held between the two flanges 252' and 252". In order to illustrate the winding structure. Figure 4 shows two parallel-wound round wires 2 3 of a turn or of a bundle conductor of the exciter winding 22, one round wire 23 being illustrated as a solid line and the other round wire 23 being illustrated as a dot-dashed line. Both round wires 23 are guided at the same time around the individual fingers 24, which are later replaced by the poles 14,14' when the exciter winding 22 is inserted in the stator 11, in which case the said round wires lie next to one another on the guide faces 241 of the fingers 24 in the radial direction of the winding drum axis, run from the preceding finger 24 to the following finger 24 across the external curved surface of the winding drum 2 6 obliquely, that is to say at an acute angle, with respect to the winding drum axis and are twisted through 180 ° with one another in this region. As a result of this twisting or transposition, one round wire 23, illustrated as a dot-dashed line in Figure 4, lies on the inside, that is to say nearest to the curved surface of the drum, on all the guide faces 241 of the fingers 24 which are arranged at the end edge 2 61 of the winding drum 26, and lies on the outside, that is to say further removed from the curved surface of the drum on the guide faces 241 of the fingers 24 which are arranged at the end edge 262 ===of the winding drum 26. Conversely, the other round wire 23, which is illustrated as a solid line in Figure 4 and lies on the outside on the guide faces 241 of the fingers 24 at the end edge 2 61 of the winding drum 2 6, now lies, as a result of the transposition, on the inside on the guide face 241 of the fingers 24 on the end 262 of the winding drum 26. A turn or a bundle conductor of the exciter winding 26 is usually wound in parallel from two to five individual round wires 23. In order to illustrate the effect of the transposition once again. Figures 5 and 7 each illustrate a section along the lines VI-VI and VII-VII, respectively, in Figure 4 through in each case one of two fingers 24, succeeding one another in the winding direction, in the case of an exciter winding 22 having two round wires 23 per turn or bundle conductor and four turns, which are wound on two layers. In each bundle conductor, the individual round wires 23 are marked by rising numbers. Thus, the round wires 23 having the numbers 1 and 2 belong to the first bundle conductor, the round wires 23 having the numbers 3 and 4 belong to the second bundle conductor, the round wires 23 having the numbers 5 and 6 belong to the third bundle conductor and, finally, the round wires having the numbers 7 and 8 belong to the fourth bundle conductor. The round wire 23 of the first bundle conductor which is marked by the number 1 lies on the inside, that is to say nearest the external curved surface of the winding drum 26, on the guide face 241 of the finger 24 at the end edge 261 of the winding drum 26. The round wire 23 having the number 2 lies next to it (Figure 6). After transposition, the two round wires 23 having the numbers 1 and 2 have changed their places at the following finger 24 at the end edge 2 62 of the winding drum 26 (Figure 7) . Correspondingly, the round wires 23 of the next bundle conductor which are marked by the numbers 3 and 4 also exchange their places on the guide faces 241 of succeeding fingers 24 as a result of their transposition. The same applies to the round wires 23 of the third and fourth bundle conductor which are marked by the numbers 5 and 6 and, respectively, 7 and 8. Each bundle conductor is laid with the two round wires 23 continuously around the fingers 24 from the winding beginning to the winding end of the exciter winding 22 and the two round wires 23 are each welded or soldered at the end to form a conductor connection. In order to realise this transposition of the individual round wires 2 3 within the bundle conductor in terms of production engineering, the winding drum 2 6 is assigned a wire nozzle 27 which is illustrated diagram-matically in Figure 4, continuously draws off two round wires 23 in parallel from supply coils and feeds them to the winding drum 2 6 in such a way that they run flat next to one another on each finger 24 to be covered. In the event of the winding drum 2 6 rotating in the anticlockwise direction in Figure 4, the wire nozzle 27 executes a stroke in accordance with arrow 28, which stroke corresponds to the axial distance between two succeeding fingers 24 on the winding drum 26, and rotates through 180° in one direction during each stroke and through the same amount in the opposite direction (arrow 2 9 in Figure 4) during the return stroke, as a result of which the described transposition of the two round wires 23 in the region between two fingers 24 which succeed one another: in the winding direction is achieved. By rotating the wire nozzle 27 in opposite senses during the stroke and return stroke, the transposition of the two round wires 23 in intermediate regions, which directly succeed one another in the winding direction between two poles 14,14' is executed in opposite senses, in other words firstly in the right sense (in the clockwise direction) and then in the left sense (anticlockwise direction) or vice versa. This alternating rotation of the wire nozzle 27 in the direction of the arrow 29 in Figure 4 ensures that the twisting of the round wires 23, drawn off from the supply coils, in the region in front of the wire nozzle 27 is cancelled during each return stroke, and transposition which would make it possible to carry out the winding operation cannot occur here. The two-layer exciter winding 22 completed in this way is removed from the winding drum 2 6, after the fingers 24 have been folded into the winding drum 26, and pushed into the stator 11, the releasable poles 14' of which have previously been removed. Each winding overhang of the exciter winding 22 is laid in the process against the outer ends of the fixed poles 14 in the stator 11. The poles 14' are subsequently pushed by their insertion feet 17 into the foot guides 18 in the yoke 13, the outer ends of these poles 14' now being laid against the still free winding overhangs of the exciter winding 22. The poles 14' are fixed either by caulking or by clamping in between drive bearing and commutator bearing cover. The invention is not restricted to the exemplary embodiment described. Thus, the transposition of the round wires 23 of a txirn or of a bundle conductor can also be carried out through a multiple of 180°, for example through 360°. The round wires then assume the same position on all of the fingers 24. Transpc sition through 180° already suffices, however, to achieve sufficient stiffness of the meander-type winding. A preferred meander-type winding is embodied with three round wires per bundle conductor and six turns. In this case, the wire nozzle 27 must be equipped with three feed openings for three round wires 23 to be drawn off in parallel from supply coils. ROBERT BOSCH GMBH, 70442 Stuttgart We Claim.- 1. Stator for an electric machine, in particular for a starter motor in motor vehicles, having a hollow-cylindrical yoke (13) and poles (14,14'), which proj ect inwards from the said yoke and extend over the axial length of the yoke (13) , and also having an exciter winding (22), which is laid in a meander-shaped manner around the poles (14,14'), consists of a plurality of turns, runs around the succeeding poles (14,14') alternately at ends which face away from one another and point axially outwards, and extends between the poles (14,14') along the internal wall (131) of the yoke, characterized in that each turn of the exciter winding (22) is a bundle conductor comprising a plurality of parallel-wound round wires (23), which lie next to one another at the ends of the poles (14,14'), preferably radially with respect to the yoke axis, and are twisted or transposed with one another in the region between the poles (14,14'). 2. Stator according to Claim 1, characterized in that the transposition of the round wires (23) in the region between two succeeding poles (14,14') is 180** or a whole-number multiple of 180°. 3. Stator according to Claim 1 or 2, characterized in that the direction of rotation of the transposition in regions between two poles (14,14') which directly succeed one another in the winding direction is in mutually opposite senses. 4. Stator according to one of Claims 1-3, characterized in that the poles (14,14') are connected in a consecutive sequence first fixedly and then releasably to the yoke (13) and the yoke (13) and poles (14,14') are combined as a stack from a multiplicity of fully stamped laminate sections. 5. Stator according to Claim 4, characterized in that the poles (14,14') have a pole core (15) , which bears against the yoke (13), and a pole shoe (16), which is formed on the free end of the pole core, and in that an insertion foot (17) is formed on that end of the pole core (15) of the releasable poles (14') which faces away from the pole shoe (15), and an axial foot guide (18) is provided in the yoke (13) , into which foot guide the insertion foot (17) can be pushed in a positively locking manner in the axial direction. 6. Stator according to Claim 5, characterized in that the internal wall (131) of the yoke (13) is in each case flattened over the tangential width of the pole core (15) of the releasable poles (14'), with the result that the pole core (15) bears in a planar manner against the internal wall (131) of the yoke. 7. Stator according to Claim 5 or 6, characterized in that a plastic mask (25) is pushed onto in each case one end of the poles (14,14' ) , which plastic mask receives, between two flanges (252',252") which protrude at right angles from the pole core (15) and are connected by a web (251) clamped onto the pole core (15) , the round wires (23) of the bundle conductors in one or more layers, lying axially next to one another, of the exciter winding (22) . 8o Stator for an electric machine, substantially as herein described with reference to the accompanying drawings•

Documents:

2094-mas-1996-abstract.pdf

2094-mas-1996-claims filed.pdf

2094-mas-1996-claims granted.pdf

2094-mas-1996-correspondnece-others.pdf

2094-mas-1996-correspondnece-po.pdf

2094-mas-1996-description(complete)filed.pdf

2094-mas-1996-description(complete)granted.pdf

2094-mas-1996-drawings.pdf

2094-mas-1996-form 1.pdf

2094-mas-1996-form 26.pdf

2094-mas-1996-form 3.pdf

2094-mas-1996-form 4.pdf