WO2017134387A1

WO2017134387A1 - Coil outputs connected to an electrical connection bridge by means of ultrasonic welding

Info

Publication number: WO2017134387A1
Application number: PCT/FR2017/050228
Authority: WO
Inventors: Eric Vernay
Original assignee: Valeo Equipements Electriques Moteur
Priority date: 2016-02-05
Filing date: 2017-02-02
Publication date: 2017-08-10
Also published as: FR3047618B1; FR3047618A1

Abstract

The invention relates to an electric motor for a motor vehicle starter, comprising: at least two positive-polarity brushes; at least one electrical connection bridge (91, 92) in the form of a flat section (961) connecting to the positive brushes; at least two field coils, each coil comprising an output (Sb) in the form a flat section (960) connected electrically to the electrical connection bridge (91, 92); and a welded portion (107) between part of the flat section (961) of the electrical connection bridge (91, 92) and part of the flat section (960) of the coil output (Sb), said welded portion (107) including a cavity (95) on a face opposite the welded contact face (970, 971), the height (L3) of said cavity (95) being at least 20% of a thickness of the flat section (960, 961) containing the cavity (95).

Description

SPOOL OUTPUTS CONNECTED TO AN ULTRASOUND ELECTRICAL CONNECTION BRIDGE

The present invention relates to a motor vehicle starter with coil outputs connected to an electrical connection bridge by ultrasonic welding.

In a manner known per se, a brush holder comprises brushes mounted sliding inside open cages on the side of a manifold of the electrical collector. Elastic means, such as springs urge the brushes against the collector blades.

The braids of the brushes are electrically connected to the positive output terminal of the contactor via an electrical connection bridge. In addition, the bridge is also connected to electrical coil outputs. In order to make the connection between these two elements, the bridge and the coil outlets have a flat shape and are welded by an ultrasonic method of moving one of the two parts relative to the other which is held fixed. Pressure applied perpendicularly to the contact plane of the parts will cause, by friction, the fusion assembly of the two parts without adding material. However, there were significant variations in the tensile strength of the ultrasonic welds, in a weld lot tested for pull-out, tearing was found to be below the threshold required to withstand vibration, including identified 109 and 140 Newtons tearing. There is therefore a risk of desoldering between the bridge and the braid of the brushes. This is explained in particular by variations in the hardness of the materials or the level of wear of the welding device.

The invention aims at increasing the mechanical strength of the welds to guarantee an optimum quality of welding irrespective of the variation of the abovementioned parameters by proposing an electric motor for a motor vehicle, in particular for a starter, characterized in that it comprises:

- brushes of positive polarity, at least one flat-shaped electrical connection bridge connecting at least two brushes of positive polarity,

at least two inductive coils, each of the two inductor coils having a flat-shaped output electrically connected to said electrical connection bridge,

a welded portion comprising a part of the flat part of said electrical connection bridge and a part of the coil exit flat part welded together, these two parts of the flats each comprising a welded contact face,

and in that said welded portion has, on a face opposite to the welded contact face of one of the two flats, a hollow having a height of at least 20% of a thickness of the flat in which said hollow is made. .

The presence of the hollow at the welded portion corresponds to the presence of a boss on the opposite side which allows to focus the energy at the weld to increase the holding. The invention therefore makes it possible to increase a pull-out strength. In fact, during a test, with the same ultrasonic welding machine welding two flats of aluminum, the average resistance to tearing of the welds of the flats comprising a boss before welding was 280 Newtons against an average of 180 N when the welds of the two aluminum flats were made without boss. In another test, the average resistance to tearing of the welds of the flats comprising a boss before ultrasound welding was 220 Newtons against an average of 140 N when the welds of the two aluminum flats were made without boss according to the welds the invention. In addition, there was a disparity in the tear resistance values of the smaller welds with boss than without boss.

According to one embodiment, said welded portion comprises traces of resistance of the flats during ultrasonic welding such that the ultrasound has been oriented parallel to the two faces in welded contact of each of the two flats.

According to one embodiment, said welded portion comprises traces of holding flats during ultrasonic welding on the two opposite faces of welded contact faces of each of the two flats. This implies that the weld was performed by ultrasound vibrating the flats in a direction parallel to the faces in welded contact. According to one embodiment, each face opposite to the welded contact face of each flat has a striated imprint. These impressions come from the held flats during the ultrasonic welding process.

According to one embodiment, said welded portion comprises ultrasonic welding traces such that the ultrasound has been oriented parallel to the two faces in welded contact of each of the two flats. According to one embodiment, said welded portion comprises ultrasonic welding traces such that the vibrations due to ultrasound have been oriented parallel to the two faces in welded contact of each of the two flats.

According to one embodiment, said hollow has a height of between 25% and 60% of the thickness of the flat in which said hollow is made.

According to one embodiment, said hollow has a height of between 25% and 40% of the thickness of the flat in which said hollow is formed.

In one embodiment, each flat has a thickness of between 1 and 3 mm. According to one embodiment, the flat surface of the coil outlets has a thickness of the order of 1 .2 mm.

According to one embodiment, the flat part of the electrical connection bridge has a thickness of the order of 2.6 mm.

According to one embodiment, said hollow extends only in said welded portion.

In one embodiment, said recess extends beyond said welded portion. In one embodiment, said hollow has a shape of sphere portion. According to one embodiment, said hollow has a cylindrical portion shape. According to one embodiment, said electrical connection bridge and said outputs of the conductive coils are made of aluminum.

The invention also relates to a motor vehicle engine starter characterized in that it comprises an electric motor as previously defined.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given for illustrative but not limiting of the invention.

Figure 1 is a longitudinal sectional view of a motor vehicle engine starter according to the present invention;

FIG. 2 represents a perspective view of a brush holder according to the invention belonging to the starter of FIG. 2;

Figure 3 shows the assembly formed by the inductor coils, the electrical connection bridges and the brushes of positive polarity; FIG. 4 is a representation of the circuit diagram for mounting the inductor coils in the starter according to the present invention;

Figure 5a shows a front view of a coil exit flat surface having a spherical boss and a back view showing the shape of the corresponding hollow; Figure 5b shows a welded portion between the coil flat of Figure 5a and a flat of a corresponding bridge showing the shape of the visible hollow after the welding operation of the two parts;

FIG. 6a shows a front view of a coil exit flat surface comprising an elongated boss and a back view showing the shape of the corresponding recess;

Figure 6b shows a welded portion between the coil flat of Figure 6a and a flat of a corresponding bridge showing the shape of the visible hollow after the welding operation of the two parts; Fig. 7 is a schematic representation of an ultrasonic welding machine for assuring assembly between an inductor coil output and an electrical connection bridge.

Identical, similar or similar elements retain the same reference from one figure to another.

Referring to Figure 1, the starter 1 1 according to the invention comprises in particular a drive shaft 12, a launcher 13 mounted on the drive shaft 12, and an electric motor 15 composed of an inductor stator 16 and an armature rotor 17 integral with a shaft 18. The motor 15 comprises a carcass 21 mounted on a support 22 of the starter 1 1 intended to be fixed on a fixed part of the motor vehicle.

An epicyclic gear type speed reducer 23 is preferably interposed between a rear end of the drive shaft 12 and the shaft 18 of the electric motor 15. The starter 1 1 also comprises an electromagnetic contactor 25 having a tank metal 28 equipped with a set of excitation coils 29a, 29b. Terminals 31, 32 are shaped to each form a fixed contact inside the tank 28. One of the terminals 31 is intended to be connected to the positive terminal of the vehicle battery. The other terminal 32, called positive output terminal, is connected to the stator winding of the stator 16 and the brushes 35 of positive polarity, as is explained in more detail below.

These brushes 35 rub on conductive blades 38 of a manifold 39 to feed the rotor winding. The brushes 35 belong to a brush holder 42 equipped with cages 43 for guiding and receiving the brushes 35. These brushes 35 are biased towards the conductive blades 38 by resilient means 44 of the spring type. A bearing 45 of the rear flange serves for rotatably mounting one end of the shaft 18 of the electric motor 15.

In known manner, during the excitation of the call coil 29a, a mobile core 48 is attracted by magnetic attraction towards a fixed core 49 of the contactor 25 to, firstly, act after catching a game on a rod 50 carrying a movable contact 51 to cause the closing of the contacts 31, 32 of the contactor 25 and power the electric motor 15, and secondly, actuate a control lever 52 acting on the launcher 13. The upper end of the lever 52 is mounted in a known manner to articulation on a movable rod 55 elastically connected to the movable core 48 via a spring 56, said spring tooth against tooth, housed in the movable core 48.

The launcher 13 can thus move from a rest position in which a drive pinion 60 is located away from the starting ring of the heat engine to an active position in which the drive pinion 60 cooperates with the starter ring. of the engine. The drive shaft 12 then transmits a torque from the electric motor 15 to the drive pinion 60 through a pinion body 61, via a freewheel device 62.

When the launcher 13 is in an active position, the pinion body 61 is driven, via the freewheel device 62, by a driver 65. For this purpose, the pinion body 61 is mounted on the drive shaft by via two pads 68, 69 of annular shape. The pinion body 61 is rotatably mounted in a front bearing 70 of the support 22. This bearing 70 is constituted for example by a ball bearing or alternatively by a needle bearing, or a plain bearing.

A spring 71 biases the drive sprocket 60 towards an axial stop 72. The spring 71 will be compressed so that the pinion 60 moves back in the event of an impact of the pinion 60 with the starter ring.

FIG. 2 is a detailed view of the X-axis brush holder 42 comprising a substantially annular support plate 75 on which is fixed the set of stands 43 each serving as a housing for a brush 35.

The support plate 75 and the cages 43 that it carries are fixed on the flange forming the rear bearing 45 for the shaft 18 of the electric motor 15. In addition, the central part of the plate 75 has an opening 78 through which the assembly that it forms with the cages 43 and the brushes 35 is mounted around the shaft 18 of the electric motor 15. Each blade 35 is slidably mounted inside a cage 43, which is open on the X-axis side to allow the brushes 35 to be brought into electrical contact with the blades 38 of the manifold 39. One of the side walls has an indentation to allow the passage of the arm of a corresponding spring 44. Each spring 44 is in this case mounted around a holding system 87 formed by a pin extending axially with respect to the axis X.

As can be seen in FIGS. 3 and 4, a set of inductive electrical coils B1-B4 of the stator 16 is electrically connected between the positive output terminal 32 of the contactor and the brushes 35. The set of coils comprises two halves assemblies connected in parallel, each half assembly comprising coils B1 and B2, B3 and B4 connected in series. The outputs of the coils B1 and B3 corresponding to the ends of the coil wires are electrically connected to the positive output terminal 32 of the contactor 25 via the bridge 91. The outputs Sb of the coils B2 and B4 are electrically connected to the brushes 35 via the bridge 92. The bridges 91, 92 are constituted by an electrical conductor having a shape that is curved so as to extend along a circumference of the support plate 75. number of coils is here equal to four, but may be adapted depending on the application. The number of positive brushes is equal to two in FIGS. 2 and 4, and to four in FIG. 3. This number of brushes 35 can be adapted according to the application.

In order to facilitate the realization of the welds between each coil output Sb and the bridge 91, 92, said outputs Sb and said bridges 91, 92 comprise a flat shape referenced respectively 960 and 961. At least the outputs Sb and the bridges 91, 92 are made of aluminum. Alternatively, all the coils B1-B4 is made of aluminum. In addition, a boss 94, 94 'is made on a part of the flat part 960, 961 of one of the parts intended to be welded with a corresponding part of the flat part 960, 961 of the other part. The deformation 94, 94 'can be achieved by an embossing process.

As shown in Figure 5a, the boss 94 may have a sphere shape, which reveals a hollow 95 of shape corresponding on the opposite side. Alternatively, as shown in Figure 6a, the boss 94 'may have an elongated shape of cylinder portion, which reveals a hollow 95' of corresponding shape on the opposite side. Any other shape, for example of rectangular or triangular section, may be considered. In Figures 5a and 6a, there is shown a boss 94, 94 'made in the flat 960 of a coil output Sb. Alternatively, the boss 94, 94 'can be made in the flat 961 of the corresponding bridge 91, 92.

The boss 94, 94 'has a height L1 of at least 20% of the thickness L2 of the flat measured in a direction D1 perpendicular to the plane in which the flat 960 extends. The boss 94, 94' has a height L1 between 25% and 60% of the thickness of the corresponding flat 960. This height L1 is for example between 25% and 40% of the thickness of the flat 960 corresponding. Each flat 960, 961 may have a thickness L2 without the boss between 1 and 3mmm. In an exemplary embodiment, the flat 960 of the coil outputs Sb has a thickness L2 of the order of 1 .2 mm; while the flat surface 961 of the electric bridges 91, 92 has a thickness L2 of the order of 2.6 mm.

As can be seen in FIG. 7, the weld is produced by a high frequency displacement of the upper part (for example the coil output Sb) by a sonotrode 100 on the fixed lower part (for example the bridge 91, 92). maintained by an anvil 101. Of course, it would be possible to reverse the positioning of the two parts relative to each other. More specifically, the portion of the flat portion 961 of the bridge 91, 92 and the portion of the flat portion 960 of the coil outputs Sb intended to be soldered together each comprise a contact face referenced 970 for the coil output Sb and 971 for the corresponding face of the 91, 92. The boss 94 or 94 'is positioned on the side of the contact faces 970, 971. The boss 94, 94 'may be carried by the contact face of the movable upper part (the coil output Sb in Figure 7).

The two members 100, 101 include ridges 105 which respectively allow gripping and holding the lower piece for the anvil 101 and to drive the upper part in the longitudinal movement of the sonotrode 100. This longitudinal movement has a direction D2 parallel to the contact faces 970, 971 of the two flats 960, 961. A pressure P applied perpendicular to the contact faces 970, 971 makes it possible, by friction, to cause the fusion assembly of the two parts in contact without the addition of material. The presence of the boss 94, 94 'allows to focus the energy at the weld to increase the hold. The positioning of the two flats 960, 961 may be performed in such a way that the two flats 960, 961 have elongation directions D3 and D4 substantially perpendicular to each other (see FIG. 5b).

On the finished product, there is thus observed the presence of a welded portion 107 shown in Figures 5b and 6b having a portion of the flat portion 961 of the bridge 91, 92 and a portion of the flat portion 960 of the coil exit Sb welded together. The two welded portions of the flats 960, 961 each comprise a welded contact face 970, 971 which is not visible because of the overlap between these two faces 970, 971. Only the hollow 95, 95 'corresponding to the boss 94, 94' is visible and is positioned on the face opposite to the welded contact face 970 or 971 of one of the flats. The hollow 95, 95 'has dimensions corresponding to those of the boss 94, 94'. In particular, the hollow 95, 95 'has a height L3 corresponding to the height L1 of the boss 94, 94' described above.

The hollow 95, 95 'may extend only in the welded portion 107 as is the case for the hollow 95 having a shape of sphere portion (see Figure 5b). Alternatively, the recess 95, 95 'extends beyond the welded portion 107, as is the case for the elongate recess 95' (see Figure 6b).

In addition, each face opposite to the welded contact face 970 or 971 of each flat portion 960, 961 has a serrated imprint 108 due to the deformation applied by the striations during the welding operation.

Claims

1. Electric motor for a motor vehicle, especially for a starter, characterized in that it comprises:

brushes (35) of positive polarity,

at least one flat-shaped electrical connection bridge (91, 92) connecting at least two brushes of positive polarity,

at least two inductive coils (B1-B4), each of the two inductor coils having a flat-shaped output (Sb) (960) electrically connected to said electrical connection bridge (91, 92),

- a welded portion (107) having a portion of the flat (961) of said electrical connection bridge (91, 92) and a portion of the coil exit flat (960) (Sb) welded together, said two portions of the flats (960). 961) each having a welded contact face (970, 971),

- and in that said welded portion (107) has, on a face opposite to the welded contact face (970, 971) of one of the two flats (960,

961), a recess (95, 95 ') having a height (L3) of at least 20% of a thickness of the flat (960, 961) in which said recess (95, 95') is formed.

2. Electric motor according to claim 1, characterized in that each face opposite to the welded contact face (970, 971) of each flat (960, 961) has a striated imprint (108).

3. Electric motor according to claim 1 or 2, characterized in that said recess (95, 95 ') has a height (L3) between 25% and 60% of the thickness (L2) of the flat (960, 961) wherein said recess (95, 95 ') is formed.

4. Electric motor according to claim 3, characterized in that said recess (95, 95 ') has a height (L3) of between 25% and 40% of the thickness (L2) of the flat (960, 961) in which said hollow (95, 95 ') is formed.

5. Electric motor according to any one of claims 1 to 4, characterized in that each flat (960, 961) has a thickness (L2) of between 1 and 3 mmm.

6. Electric motor according to claim 5, characterized in that the flat (960) of the coil outputs (Sb) has a thickness of the order of 1 .2mm.

7. Electric motor according to claim 5, characterized in that the flat part of the electrical connection bridge (91, 92) has a thickness of the order of 2.6mm.

8. Electric motor according to any one of claims 1 to 7, characterized in that said recess (95, 95 ') extends only in said welded portion (107).

9. Electric motor according to any one of claims 1 to 8, characterized in that said recess (95, 95 ') extends beyond said welded portion (107).

10. Electric motor according to any one of claims 1 to 9, characterized in that said recess (95) has a shape of sphere portion.

1 1. Electric motor according to any one of claims 1 to 9, characterized in that said recess (95 ') has a cylindrical portion shape.

12. Electric motor according to any one of claims 1 to 1 1, characterized in that said welded portion (107) comprises ultrasonic welding traces such that the ultrasound has been oriented parallel to the two faces in welded contact (970, 971) of each of the two flats (960, 961).

13. Electric motor according to any one of claims 1 to 12, characterized in that said electrical connection bridge (91, 92) and said outputs (Sb) of the conductive coils are made of aluminum.

14. Motor vehicle engine starter characterized in that it comprises an electric motor as defined in any one of the preceding claims.