EP0644629B1 - Collector for an alternator, especially for a motor vehicle - Google Patents

Description

The present invention relates generally to alternators in particular for motor vehicles.

It relates more particularly to a new arrangement of slip rings for the excitation winding of such an alternator.

Conventionally, during the manufacture of an alternator, the slip rings are produced directly on an overhanging part of the alternator shaft.

Another known technique consists in making the collector in the form of a separate part, for example by overmolding, and then in bringing this part to the alternator shaft, for example by force fitting.

Such a known attached collector is produced by overmolding of insulating material on electrically conductive elements, and comprises a generally cylindrical body comprising at its outer surface two slip rings, and elements for connecting the rings with the ends of the wires of a winding.

Also conventionally, the collector comprises, on the side of the body on which the fitting force is to be exerted, an extension of the insulating material of the overmolding over a short distance, in order to ensure satisfactory wedging of the adjacent ring. in axial direction.

And during force fitting of the manifold on the alternator shaft, the fitting force is therefore exerted on this extension of insulating material. This effort being significant, it induces a risk of deterioration or rupture of the insulating material in this region, which is of course undesirable. The invention aims in the first place to overcome this drawback.

In addition, in the case where the attached collector has a symmetry of revolution over 180 °, with in particular two wire connection elements diametrically opposite, we generally do not care about the orientation of the collector in one or the other of the two possible angular positions. However, this orientation determines which end, external or internal, of the excitation winding of the alternator, will be connected to which ring, external or internal, of the alternator. And it was unexpectedly found that the two possible connection modes had a different influence on the behavior of the alternator with regard to electromagnetic disturbances, in particular in the radio frequency domain.

The present invention therefore also proposes to ensure that a collector to be fitted on the alternator shaft and having a general symmetry of revolution over 180 ° can adopt a particular orientation among the two possible orientations, in order to ensure a matching of the connection between the two ends of the coil wires and the two collector rings to minimize the above-mentioned disturbances.

Thus, the present invention relates to a manifold intended to be force fitted on an alternator shaft, in particular of a motor vehicle, of the type produced by overmolding of insulating material on electrically conductive elements, and comprising a generally cylindrical body comprising on its outer surface two slip rings connected to two connection elements with the ends of the wires of a winding, the body comprising a bore for said shaft and an extension of insulating material beyond one of the two rings, on a side where a force of fitting must be exerted, characterized in that at least one notch is formed in said extension, throughout its axial thickness, and reveals an edge of the adjacent ring, so that the fitting effort can be exerted directly on said ring through said notch.

• il est prévu au moins deux encoches formées dans toute l'épaisseur axiale du prolongement, et ces encoches sont disposés avec une dissymétrie de révolution sur 180°, de manière à tenir lieu de détrompeurs pour le positionnement angulaire du collecteur dans l'une parmi deux positions possibles, elles-mêmes décalées de 180° l'une par rapport à l'autre.
• il est prévu trois encoches espacées angulairement de 120°.
• deux cannelures diamétralement opposées sont formées dans ledit alésage, et l'une des encoches est angulairement alignée avec l'une desdites cannelures.
• la ou chaque encoche est formée dans toute la largeur radiale du prolongement.

Preferred, but not limiting, aspects of the collector according to the invention are the following:

• at least two notches formed in the entire axial thickness of the extension are provided, and these notches are arranged with an asymmetry of revolution over 180 °, so as to take the place of polarizers for the angular positioning of the manifold in one of two possible positions, themselves offset by 180 ° with respect to each other.
• three notches are provided at an angular distance of 120 °.
• two diametrically opposite grooves are formed in said bore, and one of the notches is angularly aligned with one of said grooves.
• the or each notch is formed over the entire radial width of the extension.

The invention also provides an alternator in particular for a motor vehicle, characterized in that it comprises on a projecting shaft a manifold as defined above.

• la figure 1 est une vue en coupe axiale, selon la ligne I-I de la figure 4, d'une pièce destinée à former un collecteur pour alternateur selon l'invention,
• la figure 2 est une vue en bout selon la flèche II de la figure 1,
• la figure 2a est une vue à échelle agrandie d'une partie de la figure 2,
• la figure 3 est une vue en coupe transversale selon la ligne III-III de la figure 1,
• la figure 4 est une vue en bout selon la flèche IV de la figure 1,
• la figure 5 est une vue en coupe axiale selon la ligne V-V de la figure 4,
• la figure 6 est une vue en élévation selon la flèche VI de la figure 4,
• la figure 7 est une vue en perspective arrachée de la pièce des figures 1 à 6,
• la figure 8 est une vue en perspective non arrachée de la pièce des figures 1 à 7,
• la figure 9 est une vue en perspective de la pièce des figures 1 à 8 terminée et montée sur un alternateur,
• la figure 10 est une vue en coupe axiale verticale d'une partie d'un premier type d'alternateur équipé de la pièce des figures 1 à 8, et
• la figure 11 est une vue en coupe axiale verticale d'une partie d'un deuxième type d'alternateur équipé de la pièce des figures 1 à 8.

Other aspects, aims and advantages of the present invention will appear better on reading the following detailed description of a preferred embodiment thereof, given by way of non-limiting example and made with reference to the accompanying drawings, on which ones :

• FIG. 1 is a view in axial section, along line II of FIG. 4, of a part intended to form a manifold for an alternator according to the invention,
• FIG. 2 is an end view along arrow II of FIG. 1,
• FIG. 2a is an enlarged view of part of FIG. 2,
• FIG. 3 is a cross-sectional view along line III-III of FIG. 1,
• Figure 4 is an end view along arrow IV of Figure 1,
• FIG. 5 is a view in axial section along the line VV of FIG. 4,
• FIG. 6 is an elevation view along arrow VI of FIG. 4,
• FIG. 7 is a cutaway perspective view of the part from FIGS. 1 to 6,
• FIG. 8 is a perspective view, not broken away, of the part from FIGS. 1 to 7,
• FIG. 9 is a perspective view of the part of FIGS. 1 to 8 completed and mounted on an alternator,
• FIG. 10 is a view in vertical axial section of part of a first type of alternator fitted with the part from FIGS. 1 to 8, and
• FIG. 11 is a view in vertical axial section of part of a second type of alternator equipped with the part from FIGS. 1 to 8.

Referring firstly to Figures 1 to 8, there is shown a part forming a collector for an alternator, at an intermediate stage of its manufacture.

The part, generally indicated in 1, is produced by overmolding of plastic material, preferably thermosetting, on conductive parts, for example copper, intended to form firstly two cylindrical contact rings with brushes, secondly two elements connection with two ends of a rotor winding of the alternator, and thirdly two electrical connection elements between the two rings and the two connection elements.

Conventionally, the cylindrical rings are initially made up of a single hollow copper cylinder 10 which, at the end of the production of the part, is cut circularly over its entire thickness in its median region to form the two rings 10a, 10b electrically isolated from each other (Figure 9).

The connection elements, respectively 14a, 14b, comprise two facing tabs 15, 15 which define between them a flared central channel 17 and which are connected together by a part 15 'in the form of a truncated cone sector , defining the bottom of the channel. This channel is intended to receive one end of the winding. The associated connecting element, respectively 12a, 12b, extends radially inwards from the narrowest side of the part 15.

Each tab 15 has, in the region of the bottom of the channel and on its edge turned radially inwards, a notch in this case semi-circular 16.

In addition, as best seen in Figure 2a, each tab 15 has on its inner face a generally rounded boss 151, preferably made by stamping, for purposes explained below.

FIG. 9 illustrates the end of a winding wire FB which has been placed in the connection element 14a, the part 1 occupying in this case an angular position such that the two connection elements 14a, 14b are vertically aligned. The wire is bent over 180 ° and its free, descending end is engaged in the channel defined between the legs 15, while its elbow is housed in one of the notches 16.

Then, a crimping or pinching is carried out by bringing together with a tool the two tabs 15, which pinch the free end portion of the wire, this step being followed by welding, for example electric. It will be observed that the presence of the bosses 151 makes it possible, within the framework of an automated connection, to easily detect the degree of pinching of the wires adequate so that the electric welding operation is then carried out in a satisfactory manner. More precisely, the bosses make it possible to prevent the sharp edges of the lugs 15 from cutting the wire during pinching.

The construction of the connection element such as 14a has many advantages.

First of all, the flared shape of the channel delimited by the lugs 15 and the bottom 15 ′ exerts a guiding effect during the introduction of the free end of the wire. This flared shape also allows, because the channel 17 has its greatest width at the connection of the element 14a or 14b with the rest of the metal part, to limit the necking phenomena when folding the legs 15 to exert the pinch.

Then, before pinching using the tabs 15, the notch 16 which receives the bent region of the wire ensures stabilization of the wire in the position illustrated in FIG. 9, in particular preventing it from disengaging from the channel by its open side.

Finally, the tabs 15 ensure a firm but not sharp pinching of the wire, to ensure good mechanical strength before the welding step.

It will be observed here that a wire clamp element as described above can quite apply to fields other than that of the electrical connection of a collector to an alternator winding.

Finally, the connecting elements 12a, 12b each comprise a part in the form of a cylinder portion, respectively 121a, 121b, welded on the inner face of the part 10 intended to form the rings, a first generally straight intermediate part, respectively 122a, 122b , the section of which is U-shaped at least over a substantial part of its length (see in particular FIG. 3, right part, and FIG. 7), and offset radially inwards relative to the respective associated part 121a, 121b, and a second intermediate part, of flat section, curved at an angle of approximately 90 °, respectively 123a, 123b, the radially oriented end of which extends into the element respective connection 14a, 14b. The profile variations of the parts 121a-123a and 121b-123b take place gradually.

It will be observed here that the parts 121a, 121b are welded to the part 10 respectively in its close region and in its region remote from the connecting elements 12a, 12b, so that after the aforementioned cutting, the connecting element 14a is only connected to the ring 10a, and that the connection element 14b is only connected to the ring 10b.

It will also be noted that the U-shaped section of the straight intermediate parts makes it possible to increase their rigidity, in order to minimize any risk of inadvertent positioning deviation during the overmolding step, and in particular to avoid any risk of short circuit between the part of the cylinder 10 which will become the inner ring 10a and the adjacent intermediate part 122b.

It is further observed that each curved intermediate portion 123a, 123b comprises, in the vicinity of the respective connection element 14a, 14b, a wider region, respectively 124a, 124b, defining two lateral anchoring tabs 1241 and in which is formed a circular through hole 1242. This hole is intended to cooperate with arrangements (fixed or mobile) of the mold so as to precisely position the connection elements 14a, 14b during the overmolding step.

We will now describe the plastic part obtained after the molding step of the aforementioned conductive parts.

First there is a part 20 of generally cylindrical shape, which extends inside the copper cylinder 10 completely covering its inner face as well as the conductive plates 121a, 121b and the sections of the intermediate parts 122a, 122b located at the interior of said cylinder. This cylinder 20 is extended, in the direction of the connection elements 14a, 14b by another cylindrical part 22, the external surface of which comes flush with the external surface of the copper cylinder 10.

The parts 20, 22 define a central cylindrical bore 24 provided over its entire length with two grooves 26, 26 'of generally rectangular section, diametrically opposite and occupying the same angular positions, relative to the axis of the part, as the elements connection 14a, 14b.

This grooved bore is intended to receive a shaft, of complementary shape, from the alternator, on which the part 1 is force fitted.

On the side opposite to the cylindrical part 22, the cylindrical part 20 is extended by a small flange 28 with bevelled outer and inner edges, respectively 28a and 28b. Between the bevelled outer edge 28a and the copper cylinder 10, the part 28 has a cylindrical surface slightly set back from the exterior surface of said cylinder 10.

In this part 28 are formed three notches 30, 30 'and 30' 'whose depth is equal to the length of the part 28 in the axial direction, that is to say that the bottom of these notches reveals the edge of the copper cylinder.

One of these three notches 30 is aligned with the lower groove 26, while the other two, 30 'and 30' ', are angularly offset in this case by 120 ° on either side of the notch 30 .

It is understood that the copper cylinder 10 is firmly trapped in the axial direction between the plastic parts 22, 28.

The notches 30, 30 ', 30''have a dual role. First, the press fit of part 1 on the shaft of the alternator is carried out, for example automatically, by exerting a very large axial force on the part 1 on the side of the part 28. The notches 30, 30 ', 30''are intended to receive three pressure fingers of the automaton, which in this way will exert the force on the part by acting not on its plastic parts, but on the edge, turned towards part 28, of the metal cylinder 10. In this way, this force is exercised without risk of deterioration of the plastic of the part, the mechanical resistance of which is of course much lower than that of copper.

In addition, the notches 30, 30 ', 30' 'make it possible to provide a polarization as for the angular positioning of the part 1 on the alternator before its fitting.

It will be noted here that the two ends of the alternator rotor winding correspond respectively to an interior side of the winding ("current input") and to an exterior side of the winding ("current output").

In the prior art, one of these ends of wires was connected indifferently to one of the rings 10a, 10b, and the other end to the other ring.

However, it was found that the behavior of the alternator in the presence of electromagnetic disturbances radiated for example by radio emissions, and very particularly in the frequency modulation band, was significantly influenced by the way the ends of the winding excitation were connected to the potentials supplied by the regulator circuit of the alternator. More specifically, we will ensure that the inner end of the winding (closest to the alternator shaft, corresponding to the start of the winding when it is made) is connected to the terminal of the regulator which delivers a fixed potential , corresponding to a well-defined one of the rings 10a, 10b while the terminal of the regulator delivering the variable potential, corresponding to the other ring of the collector, will be connected to the outer end of the winding (end of the winding).

The notches 30, 30 ', 30' 'allow the pairing of these connections to be carried out, the correct angular position of the part 1, among its two possible positions offset by 180 °, being determined for example by means of one or more probes associated with robotic assembly equipment, or even visually during manual operations.

The part 1 after overmolding further comprises two plastic branches 32a, 32b in which the connecting conductive parts 122a, 123a and 122b, 123b are entirely embedded, respectively, and a ring-shaped part 34 of axis coinciding with that of the cylindrical parts 10, 20, 22, connected to these parts by said branches and situated at the level of the connection elements 14a, 14b.

More specifically, each branch 32a, 32b comprises a rectilinear section, respectively 321a, 321b, and a section curved over 90 °, respectively 322a, 322b, conforming to the shape of the curved intermediate parts 123a, 123b made of conductive material.

The branches 32a, 32b are connected radially and in positions diametrically opposite the ring 34, at the level of the connection elements 14a, 14b.

It is observed that each branch 32a, 32b, in the transition region between its rectilinear section and its curved section, exhibits an outward offset noted respectively 323a, 323b.

The inner face of each straight section 321a, 321b is located in the extension, in an axial direction, of the inner face of a groove 26, 26 'of the bore 24, while the outer face of each straight section has a profile in the shape of an arc of a circle and is located in the extension, in an axial direction, of the face part 22.

The ring 34 comprises, in two diametrically opposite positions and offset by 90 ° relative to the connection elements 14a, 14b, two thickeners 341 directed outwards, and in the external surface of which two slightly concave recesses 342 are formed respectively.

Two other extra thicknesses 343, also directed outwards, are formed in the ring 34 at the connection elements 14a, 14b, so as to partially trap the anchoring lugs 1241. In these extra thicknesses 343 are also formed respectively two recesses 344 allowing the circular holes 1242 to be left free.

The production of the ring 34 during the overmolding step makes it possible to stiffen the part 1 in the region of the connection elements 14a, 14b, ensuring that their mutual distance in the radial direction is well determined. Indeed, the presence of the alternator fan not far from these elements 14a, 14b after fitting the part requires positioning these elements precisely in the radial direction. Furthermore, the ring 34 makes it possible to guarantee the absence of any contact between the elements 14a, 14b and an enlarged part AR1 of the alternator shaft AR (see FIG. 9), around which the ring comes position, especially during expansion phenomena due to heating or accumulation of dust in this region of the alternator.

In addition, the injection of the overmolding material is preferably carried out at the level of this ring, and in particular at the level of the extra thicknesses 341.

In addition, the concave surfaces 342 provided laterally and diametrically opposite are used for gripping the part by a robot in order to press fitting on an alternator shaft. Thus the part can be gripped according to two possible orientations, mutually offset by 180 °, and it was indicated above how the notches 30, 30 ′, 30 "made it possible to ensure a polarization to choose the orientation which is suitable for supplying winding with the correct polarity.

It will also be noted that the recesses 323a, 323b, which project radially outward from the cylindrical surface defined by the cylinder 10 and its insulating extension 22, make it possible, when mounting the part on certain alternators, to define an axial stop for a ball bearing provided between the alternator shaft and its casing to constitute the rear bearing of the alternator.

Figures 10 and 11 show a part as described above mounted respectively on two alternators A of different models. The alternator shaft is designated by AR, and a bearing for this shaft by R.

We understand the role of the ring 34, which avoids any "floating" of the connection elements 14a, 14b and any risk of short circuit with parts relatively close to the alternator.

It is also observed that a side plate P of the bearing R is in abutment against the shoulders 323a, 323b defined by the part 1.

Of course, the present invention is in no way limited to the embodiment described above and shown in the drawings, but those skilled in the art will know how to make any variant or modification within the scope of the appended claims.

Claims (6)

1. Commutator designed to be forcibly fitted on an alternator shaft, notably for a motor vehicle, of the type produced by moulding insulating material onto electrically conductive elements, and comprising a generally cylindrical body (10a, 10b, 20, 22) having on its external surface two collector rings (10a, 10b) connected to two elements (14a, 14b) for connection with the ends of wires (FB) of a coil, the body having a bore (24) for the said shaft and an extension made of insulating material (28) beyond one of the two rings, on a side where a fitting force is to be exerted, characterised in that at least one notch (30, 30', 30") is formed in the said extension, in its entire axial thickness, and reveals an edge of the adjacent ring (10b), so that the fitting force can be exerted directly on the said ring through the said notch.
2. Commutator according to Claim 1, characterised in that provision is made for at least two notches (30, 30', 30") formed in the entire axial thickness of the extension (28), and in that these notches are disposed with asymmetry of revolution over 180°, so as to take the place of locators for the angular positioning of the commutator (1) in one out of two possible positions, themselves offset by 180° with respect to one another.
3. Commutator according to Claim 2, characterised in that three notches (30, 30', 30") are provided, spaced apart angularly by 120°.
4. Commutator according to Claim 3, characterised in that two diametrically opposed flutes (26, 26') are formed in the said bore (24) and in that one (30) of the notches is angularly aligned with one (26) of the said flutes.
5. Commutator according to one of the preceding claims, characterised in that one or each notch (30, 30', 30") is formed in the entire radial width of the extension.
6. Alternator (A) notably for a motor vehicle, characterised in that it has, on a projecting shaft (AR) a commutator (1) according to one of the preceding claims.

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