EP3234452B1 - Cut-off mechanism including a strip actuated by an electromagnet comprising two air-gaps - Google Patents

Description

The field of the present invention is that of light projectors and, more particularly, that of motor vehicle headlights.

Motor vehicle headlamps generally comprise a reflector in which are arranged a light source and means for controlling the shape of the beam to adapt it to the driving circumstances.

It is known to use a cut-off strip allowing various phases of occultation of the light beam. The strip is electrically actuated to move, on command, between at least two angular positions in which it more or less obscures the light beam. This makes it possible to limit the range of the headlamp, for example to that of dipped beam headlights, called low beam position, so as not to dazzle drivers traveling in the opposite direction, or even to that of main beam headlights, called high beam position, in which it does not there is no concealment.

The devices of the prior art which control the position of the bar generally consist of an actuation motor associated with a sensor of the position of the cut-off bar or with a stop which defines the rest position of the bar. For safety reasons, this rest position is associated with the dipped position, in order to avoid dazzling drivers coming in the opposite direction in the event of a failure of the bar actuating device. The return to the stop position or to the extreme position is generally ensured by a spring.

For the realization of the actuation motors it is known to use an electromagnet which exerts, against a return spring, an attraction force on a moving assembly connected to the cut-off bar. It also includes a metal carcass which forms a cradle for the electromagnet and which ensures its magnetic looping. The electromagnet comprises an induction coil formed by turns which are supplied with electric current to actuate the motor, and a ferromagnetic core which is placed in the center of the coil. This core is fixed longitudinally in the coil and has the function of serving as a point of attraction for the moving assembly when the coil is energized.

The document EP 2 180 245 A1 describes a cut-off mechanism for headlights comprising a bar carried by a moving assembly and a motor for actuating said assembly with an electromagnet.

One of the problems encountered with such an electromagnet is that the ferromagnetic core, even if it is made of iron or mild steel, becomes somewhat magnetized during the passage of the current and that it retains a remanent magnetism after the current has been cut. There is then a phenomenon of sticking of the moving assembly for a time which, even if it is very short, remains incompatible with the reaction times which are required for the rotation of a strip of a cut-off mechanism.

Solutions have been proposed, such as the introduction of a non-ferromagnetic material, such as copper, between the core of the electromagnet and the moving assembly, or else an arrangement which tends to increase the restoring torque on this moving crew. It may be, for this, an increase in the return force of the spring or an increase in the lever arm by which this spring acts. These solutions have the disadvantage either of being relatively expensive (case of copper), or of requiring an electromagnet of greater size, which is undesirable both in terms of price and size.

The object of the present invention is therefore to propose a control mechanism for a switch bar which does not have the drawbacks of the prior art and in particular which, while remaining low cost, is not sensitive to the phenomenon of magnetic remanence. and, consequently, does not exhibit any sticking of the moving assembly when the current is cut off.

To this end, the subject of the invention is a switch-off mechanism for a motor vehicle headlamp comprising a bar carried by a mobile rotating element and shaped to more or less block a light beam so as to change the optical operating mode of said headlamp. , said mechanism further comprising a motor for actuating said movable assembly using an electromagnet comprising an induction coil associated with a fixed ferromagnetic core positioned at its center and with a metal frame surrounding said coil, said movable assembly being movable, between a position in contact in which said movable assembly is in contact with the ferromagnetic core under the action of said electromagnet, against a return spring and a remote position in which said assembly moving part is at a distance from said ferromagnetic core via a first air gap under the action of the return spring, characterized in that said moving part is a a ferromagnetic plate formed by an upper plate and a lower plate extending on either side of the axis of rotation of the movable assembly, said axis of rotation being placed, without contact, in alignment with a upper branch of the metal carcass, said mobile assembly being shaped, when a current flows in the coil to create a second air gap in the magnetic circuit formed by said ferromagnetic core, said metal carcass and said assembly movable, the upper plate then coming into contact with said ferromagnetic core by the attraction of the ferromagnetic core on the upper plate of the moving assembly against the return spring, the lower plate approaching a central branch of the metallic carcass without contact until said second air gap is created, the first air gap being reduced to nothing.

This break prevents the ferromagnetic parts constituting the control motor from becoming magnetized during the activation of this motor and from remaining stuck, even temporarily, to each other when this activation is stopped.

Said break in continuity forms a second air gap h2 in said magnetic circuit.

More preferably, said magnetic circuit generates in said second air gap a force of attraction on the moving assembly which tends to keep it in contact with the ferromagnetic core. This additional force allows the main attraction force to be sized to a smaller value, without reducing the ability of the ferromagnetic parts to remain in contact during motor activation.

Advantageously, said movable assembly is a ferromagnetic plate formed by an upper plate and a lower plate extending on either side of an axis of rotation, said axis of rotation being placed, without contact, in alignment with a branch of the metal carcass.

More advantageously, the upper plate extends substantially in alignment with said branch of the metal carcass.

According to the invention, said lower plate approaches a branch of the metal carcass, until said second air gap h2 is created, in the rotation bringing the upper plate into contact with the ferromagnetic core.

Preferably, the lower plate extends, in the rest position, substantially parallel to the axis of symmetry of said induction coil.

Advantageously said axis of rotation is positioned above said induction coil. The lever arm for actuating the moving assembly then being weak, the force of attraction thereon may be weak and the induction coil dimensioned accordingly.

The invention also relates to a headlamp for a motor vehicle comprising a cut-off mechanism as described above.

The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly during the detailed explanatory description which follows, of an embodiment of the invention given by way of example. purely illustrative and non-limiting example, with reference to the accompanying schematic drawings.

• la figure 1 est une vue en perspective d'un élément d'un phare de véhicule comportant un mécanisme de coupure,
• les figures 2 et 3 sont des vues de face du mécanisme de coupure de la figure 1, positionné sur une armature, respectivement dans la position de route et de code,
• la figure 4 est une vue en perspective d'un mécanisme de coupure selon un mode de réalisation de l'invention, en version assemblée,
• la figure 5 est une vue éclatée montrant, en perspective, les divers éléments constituant le mécanisme de coupure de la figure 4,
• la figure 6 est une vue schématique du moteur du mécanisme de coupure, en position de repos, et
• la figure 7 est une vue schématique du moteur du mécanisme de coupure, en position d'activation.

In these drawings:

• the figure 1 is a perspective view of an element of a vehicle headlight comprising a cut-off mechanism,
• the figures 2 and 3 are front views of the cut-off mechanism of the figure 1 , positioned on an armature, respectively in the route and code position,
• the figure 4 is a perspective view of a cut-off mechanism according to one embodiment of the invention, in the assembled version,
• the figure 5 is an exploded view showing, in perspective, the various elements constituting the cut-off mechanism of the figure 4 ,
• the figure 6 is a schematic view of the cut-off mechanism motor, in the rest position, and
• the figure 7 is a schematic view of the cut-off mechanism motor, in the activation position.

In the following description, the longitudinal or lateral references are understood with reference to the optical axis of the reflector and the terms front or rear refer to the direction in which the light beam propagates.

By referring to the figure 1 , we see the front part of a motor vehicle headlamp comprising a lens holder 1 of cylindrical shape which extends forwards from a frame 2 of rectangular shape. This extends in a plane perpendicular to the optical axis of the beam and is cut out at its center to allow said beam to pass. On this frame is fixed the cut-off mechanism whose function is to more or less block the beam depending on the vehicle traffic conditions. In a non-visible way, are arranged behind this frame, a light source generating the beam and a reflector which directs this beam forwards and towards the lens (not shown) which is installed at the front end of the lens holder 1.

By referring to figures 2 and 3 we see, in front view, respectively in the driving position and in the low position, the cut-off mechanism 3 which is mounted in the low position on the armature 2. This armature comprises, here in the lower part of its central cutout, a fixed cover 4 which partially closes off this cutout and in front of which a cut-off bar 5 can move to modulate the shape of the beam exiting from the headlamp. This bar 5 is rotatable in a plane perpendicular to the light beam and is driven by an actuating motor 6.

On the figure 2 , corresponding to the road position, the bar is retracted, that is to say it is inclined downwards and reveals the fixed cover 4, which allows almost all of the light beam to pass. On the picture 3 , corresponding to the code position, the bar is raised and it cuts the beam over a greater height than would the single fixed cover 4. After its reversal by the lens, the beam is then oriented downwards, which avoids dazzling the drivers of vehicles coming reverse.

The figure 4 and 5 show the cut-off mechanism 3 according to one embodiment, respectively, in the assembled position and in the exploded position.

This cut-off mechanism according to the invention comprises a cut-off strip 5 which is rotatable around a first tenon 31 attached to a fixed structure 30 linked to the armature 2. It pivots around the first tenon 31, in response to a control of the actuating motor, under the action of a lever arm 42 of a moving element 40, as will be explained later.

This fixed structure 30 firstly comprises a plate 32 to which is attached an electromagnet coil 61 which is supplied, as needed, with electric current to rotate or release the mobile assembly and the bar of cut 5. It also comprises two supports 33, which are linked to the plate 32, and which have the function of receiving an axis of rotation 41 linked to the mobile assembly 40 which drives the bar 5. It finally comprises an electrical connector 34 through which the electromagnet control current flows.

The two supports 33 each have the shape of a V-piece with two uprights which gradually move away from each other to form a guide during the introduction of the axis of rotation 41 of the moving crew. The bottom of the V has a cylindrical cutout serving as a housing for this axis of rotation once it is placed on the fixed structure 30. The diameter of this cylindrical cutout is slightly greater than the spacing of the two branches at the bottom of the V, so as to form a retaining clip for this axis after its introduction.

The motor 6 for actuating the bar 5 is conventionally constituted by the winding 61, which is attached to the plate 32 at its upper part and to a second plate 32b at its lower part, and by a fixed ferromagnetic core 62, substantially cylindrical , which is placed in the center of this winding, along its axis of symmetry. This ferromagnetic core 62 carries at its upper end a circular plate 63, of diameter greater than that of the core 62, which protrudes from the plate 32 and serves as a pole of attraction for the mobile assembly 40. This core is positioned so fixed inside the winding 61 and serves as a guide, inside the winding, for the lines of force electromagnetic waves which are generated by the passage of a current in the electromagnet of motor 6. These lines of force are used to generate an attraction of the mobile assembly 40 by the circular plate 63.

The motor 6 further comprises a metal frame 64, in the shape of a U, which surrounds the coil 61 and which is conventionally intended to serve as a guide for the electromagnetic lines of force outside the coil 61. While the central branch of the carcass, formed by the bottom of the U, extends parallel to the axis of the coil 61, its lower branch comes into contact with the second plate 32b, at the level of the foot of the ferromagnetic core 62, and its upper branch returns towards the axis of the coil 61, in its upper part, while remaining however at a distance from the circular plate 63 of the core 62.

Between the terminal part of the upper branch of the carcass 64 and the circular plate 63 is positioned the moving assembly 40, the characteristics of which are described below. The moving assembly 40 consists mainly of an L-shaped ferromagnetic plate 43, the purpose of which is on the one hand to ensure continuity in the guiding of the electromagnetic lines of force, in the extension of the metal carcass 64 and in particular in the direction of the axis of the coil 61, and, on the other hand, to maintain an open air gap in this circuit, whether or not this movable plate 43 is in contact with the fixed circular plate 63 of the core of the coil d induction 61. For this one of the branches of the movable plate, called upper plate 43a, is substantially aligned with the upper branch of the metal carcass 64, between the terminal edge of this branch and the ferromagnetic core 62 while its other branch, said lower plate 43b, is substantially parallel to the central branch of this metal carcass. This quasi-parallelism of the two parts of the movable ferromagnetic plate 43 with the central and upper branches of the metal carcass 64 makes it possible to give a certain continuity to the magnetic circuit around the coil 61 of the electromagnet.

The ferromagnetic plate 43 is mobile and carries for this, on its upper plate 43a, an axis of rotation 41, around which the entire mobile assembly 40 rotates. This axis is located at a relatively short distance from the end of the upper plate. 43a, which is located opposite the circular plate 63, so as to reduce the actuating lever arm of the movable assembly by the force of attraction exerted by the ferromagnetic core 62. This short lever arm makes it possible to reduce the size of the electromagnet, which is one of the aims pursued by the invention. Preferably, the axis of rotation is located laterally above the coil 61, inside the extension of the cylinder formed by the latter.

On this axis of rotation is positioned a return spring 45, which rests on the fixed structure 30 and which tends to return the upper plate 43a of the movable assembly away from the circular plate 63 of the ferromagnetic core 62 when no current circulates in the winding.

Finally, from this axis of rotation 41 extends radially, on the side of the movable plate 43, an arm 42 forming a lever for the rotation of the cut-off bar 5, simultaneously with the movable assembly 40. To this end the bar 5 comprises a first cylindrical hole 51 in which is housed the first pin 31 which serves as a pivot for the bar 5, and a second cylindrical hole 54 in which is housed a second pin 44 which extends at the end of this arm 42, parallel to the axis of rotation 41, to serve as an actuating means for said bar.

The figures 6 and 7 show the relative arrangement of the movable plate 43 and of the metal carcass 64, respectively, in the two positions that the movable assembly 40 can take, that is to say, on the one hand, in the rest position ( figure 6 ) and, on the other hand, under the action of the passage of a current in the coil 61 ( figure 7 ).

In the rest position ( figure 6 ), no current passes through the winding 61 and the ferromagnetic core 62 exerts no attraction on the movable plate 43. The upper plate 43a thereof is then moved away from the circular plate 63 of the ferromagnetic core 62, under the action of the return spring 45. There is no contact between these two parts which are separated from each other by an air gap h1. The lines of force of the magnetic circuit starting from the ferromagnetic core 62, thus pass through the metal carcass 64 then through the upper plate 43a and close on the core 62 through the air gap h1

In the activation position ( figure 7 ) where a current flows in the coil 61, the ferromagnetic core 62 attracts the upper plate 43a of the movable plate which comes into contact with it against the return spring 45. The air gap h1 is then reduced to nothing. On the other hand, the lower plate 43b approaches the central branch of the metal carcass 64 to the point of creating with it a second air gap h2, without contact. In this configuration, the lines of force starting from the ferromagnetic core 62, pass through the lower branch then through the lower part of the central branch of the metal carcass 64; they then cross the air gap h2 to then follow the lower 43b then upper 43a plates and close the circuit by the contact between this upper plate and the circular plate 63.

In both cases the magnetic circuit has an air gap (h1 or h2) which opens the magnetic circuit and prevents its components from magnetizing when the winding is energized, which eliminates the risk of the upper plate 43a sticking against the circular plate 63 .

We will now describe the operation of the cut-off mechanism according to the invention. Mobile assembly 40, in its rest position, is moved away from ferromagnetic core 62 under the action of return spring 45 and leaves an air gap h1 between its upper plate 43a and circular plate 63 of this core. This air gap is chosen to be of a relatively small size so that the upper plate 43a can be attracted by the magnetic core thanks to a low intensity current in the coil 61. The coil 61 of the electromagnet can thus be chosen of small size, which is, here again, one of the aims pursued by the invention. At the same time, the lower plate 43b is relatively far from the metal carcass 64.

When a current is sent through the coil 61 to trigger the switch to the driving position for the headlight, the upper plate 43a is attracted against the circular plate 63. The two parts then come into contact but the magnetic circuit generated by the electromagnet does not close for all that, since the moving assembly 40 is shaped so that the lower plate 43b does not come into contact with the metal carcass 64. The gap remaining between these two parts forms the second air gap h2. This avoids magnetization of this movable plate 43 and remanence which would produce a sticking effect of the movable plate 43 on the circular plate 63.

Furthermore, the space left free between the lower plate 43b and the central branch of the metal carcass 64 is calibrated so as to form a relatively small air gap h2 between these two parts. Because the magnetic circuit, in the activation position of the cut-off mechanism, passes through this lower plate and this central branch, an attraction is created between these two parts. This force is added to that of attraction of the upper plate 43a towards the circular plate 63 and makes it possible to guarantee permanent contact between the movable plate and the ferromagnetic core. This additional force makes it possible, for example, to take into account the jolts due to bumps in the road, which could separate these two parts. There is then no need to oversize the main force of attraction linked to the first air gap h1 to take these hazards into account.

The double attraction created by the two air gaps makes it possible to reduce the size of the coil 61 and overall of the entire electromagnet, and therefore of the actuating motor 3 of the cut-off bar 5.

Finally, it is noted that the mobile assembly 40 is in the rest position or in the activation position, that the magnetic circuit passes through the axis of rotation 41. In one case, this runs along the upper branch of the carcass to join the upper plate 43a at this axis of rotation; in the other case it circulates on the lower part of the central branch of the metal carcass 64 then on the movable plate 43 and therefore passes through the axis of rotation 41. This situation gives complete freedom to position the axis of rotation laterally 41, as long as it remains in this magnetic circuit. The invention thus makes it possible to place it as close as possible to the circular plate 63 and therefore to greatly reduce the lever arm which actuates the rotation of the mobile assembly 40. In a preferential mode (not illustrated on the figures 6 and 7 ), the axis of rotation 41 is positioned laterally above the coil 61, secantly with the cylinder extending the latter upwards or downwards. And by arranging to balance the masses of the mobile assembly and of the cut-off bar around this axis of rotation 41, the force of attraction necessary to rotate this assembly can be relatively low. The invention then only requires a coil 61 of small size, contrary to what the prior art proposes.

Claims (6)

1. A cut-off mechanism for an automotive vehicle headlamp comprising a bar (5) carried by a movable assembly (40) movable in rotation and is shaped to block greater or less a light beam so as to change the optical operating mode of said headlamp, said mechanism comprising further a motor (6) for actuating said movable assembly (40) using an electromagnet comprising an inductive coil (61) associated with a fixed ferromagnetic core (62) positioned in its centre and with a metal carcass (64) surrounding said coil (61), said movable assembly (40) being movable, between a contact position in which said movable assembly (40) is in contact with the ferromagnetic core (62) under the action of said electromagnet, against the action of a return spring (45), and a distance position in which said movable assembly (40) is distant from said ferromagnetic core (62) via a first air gap (h1) under the action of the return spring (45),
   characterised in that said movable assembly (40) is a ferromagnetic plate (43) formed by an upper plate (43a) and a lower plate (43b) extending on either side of the axis of rotation (41) of the movable assembly (40), said axis of rotation (41) being placed without contact, in alignment with an upper branch of the metal carcass (64), said movable assembly (40) being shaped, when a current flows in the coil (61), to create a second air gap (h2) in the magnetic circuit formed by said ferromagnetic core (62), said metal carcass (64) and said movable assembly (40), the upper plate coming then into contact with said ferromagnetic core (62) by the attraction of the ferromagnetic core (62) on the upper plate (43a) of the movable assembly (40) against the return spring (45), the lower plate (43b) approaching a central branch of the metal carcass (64) in a noncontacting manner until said second air gap (h2) is created, the first air gap (h1) being reduced to zero.
2. The mechanism according to claim 1 wherein said magnetic circuit generates in said second air gap (h2) an attractive force on the movable assembly (40) which tends to keep it in contact with the ferromagnetic core (62).
3. The mechanism according to claim 1 wherein the upper plate (43a) extends substantially in alignment with said upper branch of the metal carcass (64).
4. The mechanism according to claim 1 wherein the lower plate (43b) extends, in a rest position, substantially parallel to the axis of symmetry of said inductive coil (61).
5. The mechanism according to one of claims 1 to 4 wherein said axis of rotation (41) is positioned above said inductive coil (61).
6. An automotive vehicle headlamp comprising a cut-off mechanism according to one of claims 1 to 5.

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