EP1678732B1 - Contactor contact device for an electric starter - Google Patents

Abstract

A contactor for an electric starter, comprising two fixed contact elements (36A,36B) having contact heads (52), and a moveable contact (30) in the form of a conducting plate bridge cooperating with the contact heads (52), and having a recess (50) at both opposite ends, the profile of said recess being oriented inwards i.e. concave, whereby said recess engages with a portion of the contact head (52) in order to create a contact area which can ensure angular immobilization of the plate when in a closed position.

Description

Technical field of the invention

• deux éléments de contacts fixes en liaison avec le circuit principal d'alimentation du moteur de démarreur,
• un contact mobile en forme de pont à plaquette conductrice coopérant avec des têtes de contact des contacts fixes,
• et un électroaimant d'actionnement du contact mobile entre des positions d'ouverture et de fermeture selon une direction sensiblement perpendiculaire au plan dans lequel sont situées les têtes de contact.

The invention relates to a contactor for an electric starter of a motor vehicle, comprising a contact device having:

• two fixed contact elements in connection with the main power supply circuit of the starter motor,
• a movable bridge-shaped contact with a conductive plate cooperating with contact heads of the fixed contacts,
• and an electromagnet actuating the movable contact between opening and closing positions in a direction substantially perpendicular to the plane in which the contact heads are located.

State of the art

In FIGS. 1 and 2, an electric starter contactor 10 of the type described in document FR 2714521, comprises an electromagnet with a movable core 12 actuated in translation against a fixed core 24, 26 during the excitation of a coil 20, 22 of tubular form. The contactor 10 is equipped with a movable contact 30 and two fixed contact elements 36A, 36B respectively connected with the battery, and the electric motor of the starter. The coil 20, 22 is housed in a sleeve 18, and the gap 32 between the two cores 12, 26, is axial. The movable contact 30 is constituted by a bridge-shaped plate made by cutting. The two fixed contact elements 36A, 36B are arranged in an insulating cover 34 connected to the yoke 14, and are each provided with a convex contact head 40A, 40B mounted on a pad 38A, 38B. A control rod 28 is integral with the plate of the movable contact 30, and is actuated by the movable core 12 during its attraction against the fixed core 26.

The plate of the movable contact 30 comprises a central orifice 42 for the passage of the control rod 28, and two oblong holes 44A, 44B whose edges come into contact with the convex contact head 40A, 40B shaped spherical cap. The parallel edges of the two holes 44A, 44B extend in perpendicular directions. Each hole 44A, 44B delimits with the curved contact head 40A, corresponding 40B, two point contact zones to avoid any risk of contact failure due to fouling resulting from the presence of particles of insulating material. The orientation of the holes 44A, 44B in two perpendicular directions allows a slight oscillation effect favoring the self-cleaning of the mechanical contact areas during the docking of the edge of the two holes 44A, 44B oblong on the convex contact head 40A, 40B. This perpendicular orientation of the holes 44A, 44B makes it possible, on the other hand, to compensate for the manufacturing tolerances of the various components of the contactor, so as to guarantee the presence of two points of mechanical and electrical contact on each of the curved contact heads 40A, 40B.

After establishing the contact, the wafer connection and curved contact head 40A, 40B is stable. The wafer must nevertheless have a large size in the length direction, since the presence at the opposite ends of the oblong holes 44A, 44B requires a length greater than the spacing between the convex contact heads 40A, 40B.

According to a known contactor illustrated in FIG. 3, the contact surface of the two fixed contact elements 36A, 36B and the plate of the movable contact 30 is completely flat, and may possibly comprise streaks 37 which serve to ensure the clearance of insulating particles or to a possible layer frost likely to be at the interface of the parts. The insulating particles are all the more difficult to evacuate as the contact surfaces are worn out and the streaks are faded. The electric arcs that occur during closure and opening of the movable contact accelerate the erosion of the contact surfaces, and also tend to deposit an insulating oxide layer thereon. Even when the contact is established, the occurrence of arcing remains possible due to possible micro-displacement of the wafer relative to the fixed contacts 36A, 36B, due for example to vibrations or shocks. In the case of a flat contact, the wafer-fixed contacts link 36A, 36B in the closed position, has at least three degrees of freedom, namely displacements with respect to x and y and a rotation with respect to z . These two defects can cause an increase in the contact resistance, or even a total electrical insulation of the contact.

In another known contactor shown in FIG. 4, the plate of the movable contact 30 comprises at each end an inclined surface 37A with respect to the direction of displacement z. The heads of the fixed contacts 36A, 36B also have an inclined surface opposite that of the wafer. Contact on these inclined surfaces promotes mechanical cleaning of the contact areas by the tangential sliding component during docking. In the closed position, the mobile contact connection 30 and fixed contacts 36A, 36B is more stable, since only one degree of freedom remains, namely a translation along the y axis. The risk of occurrence of electric arcs is limited, which reduces the oxidation and wear of the contact surfaces. The method of manufacturing the wafer is more expensive than that of a flat contact, because a resumption of machining is necessary to obtain the inclined surfaces. The thickness of the wafer must also be greater to be able to contain these surfaces. Another disadvantage is the need to properly orient the fixed contacts 36A, 36B and the wafer assembly, under penalty of a defect of very high quality (non-operation of the product or short circuit) permanent...). The reduced space does not always make it possible to provide effective keys on the parts.

Document DE 4301056 discloses a contactor, in which the prismatic plate is replaced by a truncated cone centered on the Z axis of the direction of displacement. The fixed contacts have a complementary frustoconical shape, itself centered on the Z axis. The wafer can thus rotate about the Z axis, to distribute the wear of contact during successive operations of the contactor. However, this lack of immobilization may cause electric arcs detrimental to the performance and durability of the contactor.

Object of the invention

The object of the invention is to provide an electric contactor for a motor vehicle starter, to overcome the aforementioned drawbacks, and to ensure good mechanical and electrical resistance of the contactor, and to reduce the contact resistance over time .

According to the invention, this object is achieved by the fact that the plate of the movable contact comprises, at each of the two opposite ends, a recess with a reentrant profile engaging with a portion of the contact head to create a suitable contact zone. to ensure the angular immobilization of said wafer in the closed position. The contact zone may consist of a contact line, or a succession of contact points, to improve the mechanical and electrical resistance, with a reduction in time of the contact resistance.

According to a preferred embodiment, each recess of the wafer of the movable contact has a curvilinear profile and concave, especially in a circular arc. The contact head of the fixed contacts has a conical structure, the angle formed by the cone and the wafer at a predetermined contact point having a slope of between 5 ° and 80 °, and preferably between 30 ° and 60 °.

The shape of the contacts favors the mechanical cleaning of the surfaces during the docking which is done without vibrations with a tangential component. Once in contact with the contact heads, the wafer is immobilized in translation and rotation in all directions x, y and z, which reduces the occurrence of arcing by relative movement of the parts in contact. This results in an increase in the duration of the contactor, and a contact resistance limited in time.

According to an alternative embodiment, each recess of the wafer of the movable contact has a profile cut along a broken line, in particular V-shaped.

According to another variant, the contact head of the fixed contacts may have a curved structure, in particular spherical, or a multi-faceted inclined structure.

Preferably, each recess opens at the two opposite planar faces of the wafer by chamfers, each extending over a distance less than half the thickness of the wafer. The presence of these chamfers makes it possible to reduce the heating that may occur when the current passes after the contactor closes.

Brief description of the drawings

• la figure 1 est une vue en coupe d'un contacteur de démarreur selon l'art antérieur, les contacts étant représentés en position de fermeture;
• la figure 2 montre une vue en perspective à échelle agrandie du dispositif de contacts de la figure 1 ;
• les figures 3 et 4 représentent des vues identiques de la figure 2, de deux autres dispositifs de contacts selon l'art antérieur ;
• la figure 5 est une vue schématique en perspective d'un dispositif de contacts selon l'invention;
• la figure 6 montre une vue partielle du dispositif de la figure 5 avec la localisation du point de contact de la plaquette avec un contact fixe;
• la figure 6A représente une vue dans le plan P de la zone de contact ;
• les figures 7 à 9 illustrent des variantes de réalisation de la figure 5.

Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention. given as non-limiting examples and shown in the accompanying drawings, in which:

• Figure 1 is a sectional view of a starter contactor according to the prior art, the contacts being shown in the closed position;
• Figure 2 shows an enlarged perspective view of the contact device of Figure 1;
• Figures 3 and 4 show identical views of Figure 2, two other contact devices according to the prior art;
• Figure 5 is a schematic perspective view of a contact device according to the invention;
• Figure 6 shows a partial view of the device of Figure 5 with the location of the point of contact of the wafer with a fixed contact;
• Fig. 6A shows a view in the plane P of the contact area;
• Figures 7 to 9 illustrate alternative embodiments of Figure 5.

Description of particular embodiments.

Referring to Figures 5, 6 and 6A, the conductive plate of the movable contact 30 of the contactor is shaped according to a bridge having at each of its opposite ends, a recess 50 -presentant a curvilinear profile, especially in a circular arc. Each fixed contact 36A, 36B comprises a base 51 in the form of a substantially rectangular pad, said base being surmounted by a conical contact head 52, intended to cooperate with the corresponding recess 50 when closing the contactor.

Preferably, the two recesses 50 of the wafer have identical profiles, and are symmetrical with respect to the median axis coinciding with the z axis of displacement of wafer 30.

The engagement of the contact head 52 with the conductive plate of the movable contact 30 takes place along a line of contact in a circular arc. At this point, the edge of the plate of the movable contact 30 is preferably provided with a striking chamfer 53 on the two opposite faces. The presence of the lower chamfer makes it possible to increase the exchange surface along the line of contact in an arc of circle, so as to reduce the heating that may occur when the current passes. The upper chamfer is preferably identical to the lower chamfer, but does not come into engagement with the contact head 52. The symmetry of the wafer thus makes it possible to overcome the orientation of the wafer at the time of assembly of the contactor.

In FIG. 6A, the angle A formed by the cone of the contact head 52 and the wafer promotes the tangential docking effect when the contactor closes. The rectangular shape of the base 51 makes it possible to cash the torque of screwing the nuts on the connection terminals of the fixed contacts 36A, 36B.

The curvilinear profile of the recess 50 can of course have another concave shape, preferably having a shape complementary to the contact head 52. The enveloping shape of the two recesses 50 allows the angular immobilization of the wafer on the contact heads 52.

In FIG. 6, the plane P passing through the vertical axis Z 'of the fixed contact 36B and any point PC of the nip is considered. The axis W is at the intersection of the plane P and a plane parallel to XY passing through the point of contact PC. The angle A formed by the cone of the contact head 52 in the plane P, has a slope that can be between 5 ° and 80 °, and preferably between 30 ° and 60 °, depending on the structure of the fixed contact 36B.

The chamfer 53 does not exceed half the thickness of the plate of the movable contact 30, and the angle of this chamfer 53 is close to that of the angle A of the cone of the contact head 52. optimum heat exchange surface along the nip when the contactor is in the closed position.

The shape of the contacts favors the mechanical cleaning of the surfaces during the docking which is done without vibrations with a tangential component. Once in contact with the contact heads 52, the wafer 30 is immobilized in translation and rotation in all directions x, y and z, which reduces the occurrence of arcing by a relative movement of the parts in contact. These two characteristics make it possible to obtain a longer life of the parts, and to reduce the increase of the contact resistance over time.

The forms envisaged are feasible by inexpensive manufacturing processes for mass production, and also allow to significantly reduce the amount of material used. No orientation of the fixed contacts 36A, 36B or the wafer 30 is necessary for mounting, eliminating any risk of quality defect.

Figures 7-9 show different embodiments of the geometry of the fixed contacts and the ends of the wafer.

In FIG. 7, the contact heads 52 of the fixed contacts 36A, 36B have curved or spherical tops, and not planar surface tops as in FIG. 6. The plate of the movable contact 30 has arcuate concave recesses 50 circle. The mechanical and electrical resistance of the contactor is similar to that obtained with the contact heads 52 of FIG. 6. Thus the contact zone makes it possible to ensure the angular immobilization of said wafer in the closed position.

In FIG. 8, the contact heads 52 of the fixed contacts 36A, 36B are conical like those of FIG. 5, but the recesses 50 instead of being circular arcs, are cut along a V with a recessed dihedral profile. The vertices of the two V-shaped recesses are directed toward each other, and aligned in a direction passing through the longitudinal median plane of symmetry of the wafer 30. The two edges of the dihedron of each recess 50 come into engagement with the head contact 52 at two points of contact disposed on either side of the longitudinal median plane of symmetry. The size of the wafer in the longitudinal direction is substantially identical to that of Figure 6 or 7. The mechanical and electrical resistance of the contactor is also retained. Thus the contact zone makes it possible to ensure the angular immobilization of said wafer in the closed position.

In FIG. 9, the plate of the movable contact 30 is identical to that of FIG. 8, but the contact heads 52 of the fixed contacts 36A, 36B are provided with a plurality of plane facets, instead of being conical. The zone of contact with the recesses 50 in V is carried out according to points or lines according to the degree of inclination of the facets with respect to the edges of the dihedral of each recess 50. The mechanical and electrical resistance of the contactor is also preserved in this variant of execution. Thus the contact zone makes it possible to ensure the angular immobilization of said wafer in the closed position.

Claims (13)

1. Contactor for an electric starter comprising a contact device having:

   - two fixed contact elements (36A, 36B) connected to the main supply circuit of the starter motor,

   - a moving contact (30) in the form of a bridge with a conductive plate cooperating with contact heads (52) on the fixed contact (36a, 36b),

   - and an electromagnet actuating the moving contact (30) between open and closed positions in a direction substantially perpendicular to the plane in which the contact heads (52) are situated,

   characterised in that the plate of the moving contact (30) has, at each of the two opposite ends, a recess (50) with a re-entrant profile coming into engagement with a portion of the contact head (52) in order to create a contact zone able to ensure the angular immobilisation of the said plate in the closed position.
2. Contactor according to claim 1, characterised in that the contact zone is formed by a contact line or a succession of contact points.
3. Contactor according to claim 1, characterised in that each recess (50) in the plate of the moving contact (30) has a curvilinear profile.
4. Contactor according to claim 3, characterised in that each recess (50) in the plate of the moving contact (30) has a concave profile in an arc of a circle.
5. Contactor according to claim 1, characterised in that each recess (50) in the plate of the moving contact (30) has a profile cut along a broken line.
6. Contactor according to claim 4, characterised in that the profile of the two recesses (50) in the plate is in a V.
7. Contactor according to one of claims 1 to 6, characterised in that the contact head (52) of the fixed contacts (36a, 36b) has a conical structure, the angle A formed by the cone and the plate at predetermined contact point having a slope of between 5° and 80°, preferably between 30° and 60°.
8. Contactor according to one of claims 1 to 6, characterised in that the contact head (52) of the fixed contacts (36a, 36b) has a curved structure, in particular spherical.
9. Contactor according to one of claims 1 to 6, characterised in that the contact head (52) of the fixed contacts (36a, 36b) has a structure with several facets.
10. Contactor according to claim 1, characterised in that each recess (50) opens out on the two opposite planar faces of the plate through bevels (53).
11. Contactor according to claim 10, characterised in that each bevel (53) extends over a distance less than half the thickness of the plate.
12. Contactor according to claim 10 or 11, characterised in that the angle of the bevel (53) is close to or equal to that of the slope of the contact head (52).
13. Contactor according to claim 11, characterised in that the contact head (52) of each fixed contact (36a, 36b) is mounted on a base (51) arranged in a rectangular stud.

Images