FR3083026A1 - METHOD FOR CONNECTING WIRES TO AN ELECTRIC MOTOR MANIFOLD - Google Patents

Abstract

The invention relates mainly to a method of connecting wires to a collector, characterized in that it comprises: - a step of inserting ends of wires (15 ') of a winding inside of notches (23) electrically connected to blades (19) on which are intended to rub brushes, - a step of positioning a ring (30) on the ends of wires (15 ') around the notches (23), said ring (30) comprising at least a portion made of an electrically conductive material, and - a step of applying a magnetic field to project the ring (30) towards the notches (23) of the collector (18), so as to close said notches (23) and deform the ends of wires (15 ') inside the notches (23) to establish an electrical connection between the ends of wires (15') located inside each notch (23) and a corresponding blade (19) of the collector (18).

Description

METHOD FOR CONNECTING WIRES ON AN ELECTRIC MOTOR MANIFOLD

The present invention relates to a method of connecting wires to an electric motor manifold.

Motor vehicle starters are known which are provided with a stator, or inductor, comprising several permanent magnets or wound poles (electromagnets) and a rotor, or armature, provided with a cylindrical body and a formed winding. by conducting wires.

In a manner known per se, the rotor body consists of a bundle of sheets having longitudinal notches. To form the winding, pin-shaped conducting wires are threaded inside the notches, generally on two separate layers.

The rotor further comprises a collector provided with electrically conductive blades which extend side by side on the external periphery of a support made of plastic material. These conductive blades are intended to cooperate with brushes of the electric motor, in order to ensure the switching of current inside the wires of the winding.

Each of the blades is extended by a heel having a notch in which two ends of the winding wires are positioned. The ends of the wires are connected to the collector generally by ultrasonic welding, by hot crimping, or by resistance brazing with the addition of metal. The addition of metal is obtained by the use of a sleeve disposed around the wires or by depositing a tinned coating on the collector. A hoop made of an insulating material is placed on the wires around the collector to reinforce the resistance in centrifugation of the electrical connections previously made.

These known methods induce a long cycle time, insofar as the welding operations must be repeated for each notch of the collector and it is then necessary to install the retaining band. In addition, welding operations can thermally affect the areas around the heat source. The need to provide a supply of material also complicates certain known processes and increases the cost of manufacturing the rotor.

The invention aims to effectively remedy these drawbacks by proposing a method of connecting wires to a collector, characterized in that it comprises:

a step of inserting the ends of the wires of a winding inside notches electrically connected to blades on which are intended to rub brushes,

a step of positioning a ring on the ends of the wires around the notches, said ring comprising at least one portion made of an electrically conductive material, and

a step of applying a magnetic field to project the ring towards the notches of the collector, so as to close said notches and deform the ends of wires inside the notches to establish an electrical connection between the ends of wires located inside each notch and a corresponding blade of the collector.

The invention thus makes it possible to reduce the duration of the rotor manufacturing cycle by having to perform a single connection establishment operation instead of performing a notch welding operation. The invention also avoids having to set up the hoop during a step adding to the welding phase. The invention also has an economic character, insofar as it does not require any welding filler material. In addition, the phase of establishing the electrical connections between the ends of the wires and the blades of the collector is carried out cold, which prevents any deterioration of the collector in the areas located near the connections.

According to one implementation, before the step of applying the magnetic field, at least one end of the wire projects radially from a corresponding notch.

According to one implementation, the ring has an outer portion made of an electrically conductive material and an inner portion made of an electrically insulating material.

According to one implementation, the external portion and the internal portion of the ring form a single piece.

According to one implementation, the ends of the wires are arranged radially one above the other inside a notch.

According to one implementation, the ends of the wires are arranged one next to the other inside a notch.

According to one implementation, a notch is formed in a heel of a blade of the corresponding collector.

According to one implementation, the rotor wires are made of copper or aluminum.

A subject of the invention is also a thermal engine starter rotor comprising:

- a collector provided with a plurality of notches electrically connected to blades on which are intended to rub brushes,

- a winding formed by wires having ends inserted in corresponding notches,

- each notch comprising at least two ends of wires,

- a ring arranged around the notches, characterized in that the ring comprises at least one portion made of an electrically conductive material, said ring maintaining the ends of wires deformed inside the notches to establish an electrical connection between the ends of wires located inside each notch and a corresponding blade of the collector.

According to one embodiment, the ring has an outer portion made of an electrically conductive material and an inner portion made of an electrically insulating material.

According to one embodiment, an external surface of the external portion is devoid of any trace of deformation.

According to one embodiment, the external portion and the internal portion of the ring form a single piece.

The invention further relates to a starter for a motor vehicle, characterized in that it is equipped with a rotor as defined above.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 shows a perspective view of a starter rotor according to the present invention;

Figure 2 is a longitudinal sectional view of the starter rotor according to the present invention;

FIG. 3 is a diagrammatic representation of a cold crimping device by magnetic pulse enabling electrical connections to be made between the wires of the rotor winding and the blades of the collector;

Figures 4a and 4b are schematic representations of a first embodiment of the invention illustrating a positioning of a ring and end wires inside a notch respectively before and after application of a field magnetic;

FIGS. 5a and 5b are schematic representations of a second embodiment of the invention illustrating a positioning of a ring and of end wires inside a notch respectively before and after application of a field magnetic.

Identical, similar or analogous elements keep the same references from one figure to another.

Figures 1 and 2 show a rotor 10 of axis X comprising a body 11 mounted on a shaft 12. This body 11 in the form of a package of laminated sheets has an outer periphery of cylindrical shape. Notches 14 are formed longitudinally at the outer periphery of the body 11. To form the winding, a set of conductive wires 15 are threaded inside these notches 14 to form a rotor winding 16.

More specifically, each wire 15 coated with an electrically insulating layer 15, such as enamel, has two branches connected together by a connecting portion so as to form a U. The wires 15 are inserted inside the notches 14 on two separate layers: the upper layer and the lower layer. If one of the branches of a wire 15 is positioned in the lower layer then the other branch is located in the upper layer and vice versa. The section of the wires 15 can be round, square, or rectangular. The parts of the wires 15 projecting from the end faces of the rotor body 11 form the chignon of the winding 16.

The rotor 10 further comprises a collector 18 provided with electrically conductive blades 19 which extend side by side on an external periphery of an electrically insulating support 20 visible in FIG. 2. The support 20 of the collector 18 secured to the shaft 12 is, for good temperature resistance, of thermosetting plastic, such as a phenolic thermosetting plastic, for example bakelite.

These conductive blades 19 extend substantially longitudinally along the axis X of the rotor 10. Brushes (not shown) are intended to rub against the blades 19. The blades 19 are each extended by a heel 22 of radial orientation with respect to to the axis X of the rotor 10. Each heel 22 comprises a notch 23 in which are positioned two ends of wires 15 ′ of the winding 16. A notch 23 is thus electrically connected to a corresponding blade 19 via a heel 22.

The method of making the connections of the ends of wires inside the notches 23 is described below by means of a cold crimping device 25 by magnetic pulse shown in FIG. 3. This device 25 generates a high electromagnetic force. allowing to mechanically link parts together.

To this end, the device 25 comprises a voltage source 26 connected to a capacitor bank 27 by means of a transformer 28. These capacitors 27 are intended to supply the coil 29 arranged around the parts to be crimp but without being in contact with them.

The cold crimping parts here consist of a ring 30 and the manifold 18. This ring 30 is arranged on the ends of the wires 15 ′ around the notches 23. Two ends of the wires 15 ′ of the winding 16 will have previously been disposed at the inside each notch 23.

The ring 30 of annular shape with axial orientation comprises a radially external portion 31 made of an electrically conductive material and a radially internal portion 32 made of an electrically insulating material, as shown in FIG. 4a.

According to an exemplary embodiment, the outer portion 31 of the ring 30 can be made of copper, silver, gold, aluminum, iron, or steel. Advantageously, copper is used which is a very good conductor and which avoids risks of corrosion due to the support of the ring 30 on the wires of the winding also made of copper. The choice of material is made according to the skin thickness for the circulation of the electric current (the skin thickness is approximately 0.2 mm for copper, 0.1 mm for aluminum, from 0, 9 mm for steel) and the compression speed of the desired material (the compression speed of copper is lower than that of aluminum for example).

The internal portion 32 of the ring 30 is made of an insulating material to avoid short-circuiting of the blades 19 of the collector 18. In the application, the portion is advantageously made of plastic, in particular in a blown injected plastic which is used to make water bottles. Such a material has the advantage of accepting deformations while having a shape memory during the magneto-crimping operation. Another material having a level of intermediate hardness between the rubber (too soft) and the mica (too rigid) is possible.

According to a particular nonlimiting embodiment, the thickness of the external portion 31 of the ring 30 is for example of the order of 1mm. By of the order of, we mean a possible variation of plus or minus 10% around this value. The thickness of the internal portion 32 is for example between 0.5 and 0.8 mm.

Advantageously, the outer portion 31 and the inner portion 32 of the ring 30 form a single piece. The portions 31, 32 can thus be glued, riveted, or welded together. The portions 31, 32 may also be assembled together by latching means or any other means suitable for the application. Alternatively, the outer 31 and inner 32 portions are separate from each other.

Thus, during the magneto-crimping or crimping by magnetic pulse cycle, a large amount of electrical energy is first stored inside the capacitors 27. A control switch 33 is then closed to release this electrical energy. over a very short time between 10 ' ⁷ and 10' ⁴ seconds. The high energy flow crosses the coil 29 which generates a magnetic field inducing eddy currents.

As illustrated by FIGS. 4a and 4b, a high electromagnetic force F is then applied to the ring 30 in the direction of the notches 23 of the manifold 18, so that the ring 30 is projected at high speed towards the notches 23. The ring 30 deforms the ends of wires 15 'inside the notches 23 to establish an electrical connection between the ends of wires 15' located inside each notch 23 and a corresponding blade 19 of the collector 18.

The magnetic pulse and the very high speed of deformation transform the metal of the external portion 31 by passing it from the solid state to an elasto-visco-plastic state, which increases its formability without affecting the initial strength of the material. The external portion 31 is then plasticized in the mass in its final state. This is done without elastic return of the material unlike a mechanical crimping which in time can degrade depending on the stresses submitted.

The ring 30 ensures radial retention to prevent the effects of the centrifugal force being exerted on the connections between the ends of the wires 15 ′ and the heels 22. The internal portion 32 of the ring 30 made of electrically insulating material avoids the formation of a short circuit in the rotor winding 16.

In order to optimize the final assembly, before the step of applying the magnetic field, at least one end of wire 15 ′ protrudes radially from a corresponding notch 23. In the embodiment of FIGS. 4a and 4b, the ends of the wires 15 'are arranged radially one above the other inside a notch 23. A portion of the end of the wire 15' the outermost protrudes from the notch 23. In the embodiment of FIGS. 5a and 5b, the ends of the wires 15 ′ are arranged one next to the other inside a notch 23. Each end of wire 15 ′ then has a portion which protrudes radially from the notch 23.

In an exemplary embodiment, the blades 19 and the heels 22 are made of copper while the wires 15 of the winding 16 can be made of copper or aluminum.

The magnetic pulse crimping process has the advantage of being carried out cold. In fact, the materials do not reach more than 30 ° C. There is therefore no heat affected zone and the material does not lose its properties. Furthermore, the process is based on the generation of a contact pressure to make the electrical connections and not of a heat, so that all conventional welding problems due to the heat cycle and the loss of material properties are avoided.

It is also noted that during the implementation of a conventional mechanical crimping process or a tight fitting, there is systematically a more or less significant deformation of the outer surface of the ring. This deformation is visible depending on the application with the naked eye or with a microscope if the deformation is minimal. On the other hand, in the invention, the external portion 31 of the ring 30 has a reduced diameter after the application of the magnetic field but its external surface is devoid of any trace of deformation.

The rotor 10 may include at one end of its shaft 12 a gear wheel 35 located on the opposite side of the manifold 18 and intended to form a sun gear in a planetary gear reduction system of a starter, as described for example in document FR2787833.

The invention also relates to the starter fitted with the rotor 10 described above.

Of course, the foregoing description has been given by way of example only and does not limit the scope of the invention from which one would not depart by replacing the various elements with any other equivalent.

Furthermore, the various features, variants, and / or embodiments of the present invention can be combined with one another in various combinations, insofar as they are not incompatible or mutually exclusive of one another.

Claims (11)

1. Method for connecting wires to a collector (18), characterized in that it comprises: a step of inserting the ends of the wires (15 ′) of a winding (16) inside the notches (23) electrically connected to the blades (19) on which are intended to rub the brushes, a step of positioning a ring (30) on the ends of the wires (15 ′) around the notches (23), said ring (30) comprising at least one portion made of an electrically conductive material, and - A step of applying a magnetic field to project the ring (30) towards the notches (23) of the collector (18), so as to close said notches (23) and deform the ends of wires (15 ') to the interior of the notches (23) to establish an electrical connection between the ends of the wires (15 ') located inside each notch (23) and a corresponding blade (19) of the collector (18). 2. Method according to claim 1, characterized in that, before the step of applying the magnetic field, at least one end of the wire (15 ') protrudes radially from a corresponding notch (23). 3. Method according to claim 1 or 2, characterized in that the ring (30) comprises an outer portion (31) made of an electrically conductive material and an inner portion (32) made of an electrically insulating material. 4. Method according to claim 3, characterized in that the outer portion (31) and the inner portion (32) of the ring (30) form a single piece. 5. Method according to any one of claims 1 to 4, characterized in that the son ends (15 ') are arranged radially one above the other inside a notch (23) . 6. Method according to any one of claims 1 to 4, characterized in that the ends of son (15 ') are arranged one next to the other inside a notch (23). 7. Method according to any one of claims 1 to 6, characterized in that a notch (23) is formed in a heel (22) of a blade (19) of the corresponding collector (18). 8. Rotor comprising: - a collector (18) provided with a plurality of notches (23) electrically connected to blades (19) on which are intended to rub brushes, - a winding (16) formed by wires (15) having ends (15 ') inserted in corresponding notches (23), - each notch (23) comprising at least two ends of wires (15 ′), - a ring (30) disposed around the notches (23), characterized in that the ring (30) comprises at least one portion made of an electrically conductive material, said ring (30) keeping the ends of the wires (15 ') deformed inside the notches (23) to establish an electrical connection between the ends of the wires (15 ') situated inside each notch (23) and a corresponding blade (19) of the collector (18). 9. Rotor according to claim 8, characterized in that the ring (30) comprises an outer portion (31) made of an electrically conductive material and an inner portion (32) made of an electrically insulating material. 10. Rotor according to claim 8 or 9, characterized in that the outer portion (31) and the inner portion (32) of the ring (30) form a single piece. 11. Starter for a motor vehicle, characterized in that it is equipped with a rotor as defined according to any one of claims 8 to