EP3764384A1 - Electromechanical actuator with self-regulated control - Google Patents

Abstract

Electromechanical actuator comprising a control coil (5), a magnetic core (2), a movable armature (3) movable between a working state and a resting state towards which it is returned by elastic return means (9). The moving armature is attracted by the magnetic core when the latter conducts the magnetic field generated by the powered coil. A Hall effect sensor (101) is crossed by a part of the magnetic flux of leakage in the vicinity of the movable armature (3), and controls a switch (102) connected in series with the control coil (5) so as to block power to the control coil (5) when the leakage magnetic flux exceeds a high threshold value, and so as to supply the control coil (5) again when the leakage magnetic flux falls below a low threshold of value. Regulation of the mean value of the supply voltage of the control coil (5) is thus achieved, by preferably choosing an average value just sufficient to maintain the electromechanical actuator in its working state.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to electromechanical actuators with a control coil, in particular those used in motor vehicles, to fulfill various control or safety functions.

An electromechanical actuator with a control coil comprises a control coil, consisting of the winding of an electrical conductor intended to be supplied according to a nominal control voltage by a voltage or electric current source, a fixed armature with a magnetic core placed in an axial passage of the control coil and intended to conduct a magnetic field generated by an electric current flowing through the conductor of the control coil, and a movable armature to form with the fixed armature a closed magnetic circuit.

According to a first possibility, the movable frame comprises a part intended to be mechanically coupled to an external element intended to be moved. In this case, the movable armature can be movable by translation or by rotation, and the actuator is used to produce a mechanical movement, for example the movement of a solenoid valve shutter.

According to a second possibility, the movable armature comprises a part carrying an electrical contact, to constitute an electromechanical relay. In this second possibility, the mobile frame is generally movable by rotation, a first end of the mobile frame being articulated according to a fixed hinge on the fixed frame.

In both cases, the mobile armature comprises an intermediate section of the mobile armature, which is located opposite one end of the magnetic core, and which is made of a material capable of being attracted by the magnetic core when the control coil is supplied with electrical energy. Elastic return means urge the movable armature to bring it back to a state of rest.

When the control coil is not supplied with electrical energy, the movable armature is in its rest state, in which the intermediate section of the movable armature is away from the magnetic core. The movable frame is maintained in this state of rest by the elastic return means. When the control coil is supplied with electrical energy according to a sufficient excitation electrical voltage, at least equal to a voltage which is designated by the expression switching voltage, the intermediate section of the movable armature is attracted by the core magnetic and the movable armature is moved against the elastic return means and comes into a working state, in which the intermediate section of the movable armature is near or in contact with the magnetic core.

In its displacement between the rest state and the working state, the movable armature produces either the displacement of the external element in the case of an actuator intended to produce a mechanical displacement, or the modification of the state of electrical conduction of an electrical contact in the case of an electromechanical relay.

In particular, in the case of an electromechanical relay, a free end of a contact section integral with the intermediate section of the movable armature is supported by a contact pad against a fixed working contact with an appropriate working force . The working force is used to avoid any rebounds when the electromechanical relay is activated, to avoid any untimely electrical trips under the effect of vibrations, and to guarantee the achievement of a low contact resistance.

In the field of automotive application, there is a need for electromechanical actuators to be able to switch reliably to their working state even when the voltage of the on-board network of the vehicle is relatively low, of the order of 8 V. This means that the switch-on voltage must be less than 8 V.

During the operation of a motor vehicle, an electromechanical actuator, installed in this vehicle to fulfill its control or safety functions, is normally in the working state, so that the control coil must be supplied with electrical energy, generally under the voltage of the on-board network. In this state, the control coil is a resistive element having an electrical resistance R and receiving the voltage U from the on-board network of the vehicle. The result is that the control coil consumes a power P which depends on the voltage U according to the formula P = U ² / R. The power consumed by the control coil when the electromechanical actuator is in its working state therefore varies as the square of the voltage of the on-board network, so that an on-board network voltage higher than the switch-on voltage leads to a large consumption of excess energy. In addition, when the ambient temperature is low, the electrical resistance R equivalent of the control coil tends to decrease, which further increases the power consumed by the electromechanical actuator.

However, there is a permanent need for energy saving in motor vehicles, and an increasingly sensitive need to avoid or reduce the heating of electronic components used in motor vehicles in the vicinity of electromechanical actuators.

According to the present invention, it is considered that the electromechanical actuators implemented in motor vehicles constitute a non-negligible source of energy loss, and a non-negligible source of heating of the surrounding electronic components, so that there is an advantage in reduce the energy consumption of electromechanical actuators, and reduce the inevitable heating that results.

It is therefore necessary that the electromechanical actuators consume little energy when they are in the working state and that the voltage of the on-board network takes a usual value which, for its part, is generally significantly higher than the switching voltage. , of the order of 13.5 V to 15 V for a vehicle with a nominal battery voltage of 12 V.

To reduce the consumption of electromechanical actuators, it has already been proposed to regulate their control voltage by a width-modulated power supply (PWM) made from electronic components such as microcontrollers driving field-effect transistors, so as to power the control coil under an average voltage slightly higher than the cut-in voltage. This solution is, however, excessively expensive, since each electromechanical actuator must be supplied independently by a width-modulated power supply, and electronic components of the microcontroller type and field-effect transistors are relatively expensive. In addition, width modulated power supplies have reaction rates, following changes in the input voltage, which are slower than the switching speed of electromechanical actuators such as electromechanical relays. This results in a lack of reliability, since a delay in the reaction of the width modulation power supply to a modification of the input voltage can cause an untimely switching of an electromechanical actuator supplied by said width modulation power supply.

The document EP 0172712 describes a plunger actuator which moves longitudinally inside a control coil equipped with a fixed magnetic armature. The control coil is energized so as to maintain constant the magnetic flux during the movement of the plunger. For this, the coil control is associated with a freewheeling diode and is supplied by means of a transistor driven by a magnetic flux sensor disposed inside an additional air gap of the fixed magnetic armature. An inexpensive control circuit is thus produced which enables the control coil to be supplied with a modulated voltage. However, the additional air gap significantly increases the reluctance of the magnetic circuit, and requires supplying the control coil with additional electrical energy which defeats the need to reduce the energy consumed by the actuator in applications. automobiles.

On the other hand, this same document EP 0172712 describes an embodiment comprising a potentiometer and an additional coil for modifying and adjusting the magnetic flux detected by the magnetic flux sensor. This solution is however expensive, and imposes a constant supply voltage, which is not the case with the on-board voltage of a motor vehicle.

The document US 4,608,620 describes an electromechanical relay in which a magnetic shunt is placed in a fixed position in the vicinity of an operational air gap of the magnetic circuit, and a magnetic field sensor is placed between one end of the magnetic circuit and one end of the magnetic shunt. The magnetic field sensor is thus placed in a bypass of the main magnetic field flowing through the magnetic circuit. When the control coil is energized and the magnetic circuit is not closed, the magnetic field detected by the sensor is high. When the control coil is energized and the magnetic circuit is closed, the magnetic field detected by the sensor is almost zero. On the other hand, when the voltage of the power source drops, the detected magnetic field is also reduced. This requires complex control electronics. In addition, the magnetic shunt reduces the efficiency of the magnetic circuit, and generates on the mobile armature a harmful attraction force because it is perpendicular to its displacement.

The document GB 2 259 188 describes a solenoid valve in which the control coil is supplied by an electronic circuit as a function of a signal communicated by a magnetic field sensor placed against a side branch of a fixed armature, away from the movable armature. The electronic circuit associated with the magnetic field sensor makes it possible to reduce the power supply to the control coil after closing the magnetic circuit, to reduce the electrical energy consumed. The position of the magnetic field sensor as illustrated in this document does not make it possible to have a signal to noise ratio allowing reliable control of the supply of the control coil in an environment disturbed by external magnetic fields as is the case in automotive applications.

DISCLOSURE OF THE INVENTION

A problem proposed by the present invention is to design inexpensive means for substantially reducing the energy losses generated in an electromechanical actuator capable of being driven from a source of continuous electrical energy at variable voltage, in particular such an electromechanical actuator. integrated into a motor vehicle, while ensuring good operating reliability of the electromechanical actuator.

In particular, the invention aims to reliably and inexpensively control the power supply to the actuation control coil of the electromechanical actuator, without reducing the efficiency of the magnetic circuit, and without risk of disturbance or malfunction caused. by the external magnetic fields of automotive applications.

• un circuit magnétique, ayant une armature fixe apte à conduire un flux magnétique principal entre une première extrémité et une seconde extrémité, et ayant une armature mobile engagée entre la première extrémité et la seconde extrémité de l'armature fixe, l'armature mobile étant apte à être déplacée selon un mouvement relatif vis-à-vis de l'armature fixe entre un état de travail et un état de repos vers lequel elle est rappelée par des moyens de rappel, l'armature mobile étant apte à conduire la majeure partie dudit flux magnétique principal, un flux magnétique de fuite traversant l'espace environnant le circuit magnétique,
• une bobine de commande, agencée de façon à générer, lorsqu'elle est alimentée à partir d'une source d'énergie électrique continue, un flux magnétique comprenant ledit flux magnétique principal conduit par l'armature fixe du circuit magnétique et comprenant ledit flux magnétique de fuite traversant l'espace environnant le circuit magnétique,
• un capteur de champ magnétique, placé de façon à être sollicité par ledit flux magnétique généré par la bobine de commande,
• le capteur de champ magnétique étant structuré de façon à produire un signal de sortie ayant une première valeur de signal et une seconde valeur de signal, le signal de sortie basculant vers sa première valeur de signal si le champ magnétique détecté devient supérieur à un premier seuil de champ magnétique, le signal de sortie basculant vers sa seconde valeur de signal si le champ magnétique détecté devient inférieur à un second seuil de champ magnétique, le premier seuil de champ magnétique étant supérieur au second seuil de champ magnétique,
• un commutateur de commande, connecté en série entre ladite source d'énergie électrique continue et ladite bobine de commande, et piloté par le signal provenant du capteur de champ magnétique, de façon à être dans un état bloqué lorsque ledit champ magnétique détecté est supérieur au premier seuil de champ magnétique, et de façon à être dans un état passant lorsque ledit champ magnétique détecté est inférieur au second seuil de champ magnétique,
• une diode de roue libre, connectée en parallèle sur la bobine de commande,
• de sorte que le capteur de champ magnétique et le commutateur de commande alimentent la bobine de commande selon une tension découpée et modulée lorsque l'ensemble est connecté à ladite source d'énergie électrique continue dans lequel :
• le capteur de champ magnétique est placé dans l'espace environnant le circuit magnétique pour être traversé par le flux magnétique de fuite,
• le capteur de champ magnétique est placé, par rapport au circuit magnétique, en une position dans laquelle le champ magnétique de fuite est fortement variable lorsque l'armature mobile se déplace au voisinage de son état de travail.

To achieve these and other objects, the present invention provides an electromechanical actuator comprising:

• a magnetic circuit, having a fixed armature capable of conducting a main magnetic flux between a first end and a second end, and having a movable armature engaged between the first end and the second end of the fixed armature, the movable armature being suitable to be moved according to a relative movement with respect to the fixed armature between a working state and a rest state towards which it is recalled by return means, the movable armature being able to drive the major part of said main magnetic flux, a leakage magnetic flux passing through the space surrounding the magnetic circuit,
• a control coil, arranged so as to generate, when supplied from a source of continuous electrical energy, a magnetic flux comprising said main magnetic flux conducted by the fixed armature of the magnetic circuit and comprising said magnetic flux leakage passing through the space surrounding the magnetic circuit,
• a magnetic field sensor, placed so as to be biased by said magnetic flux generated by the control coil,
• the magnetic field sensor being structured to produce an output signal having a first signal value and a second signal value, the output signal switching to its first signal value if the detected magnetic field becomes greater than a first threshold magnetic field, the output signal switching to its second signal value if the magnetic field detected becomes less than a second magnetic field threshold, the first magnetic field threshold being greater than the second magnetic field threshold,
• a control switch, connected in series between said source of continuous electrical energy and said control coil, and driven by the signal from the magnetic field sensor, so as to be in an off state when said detected magnetic field is greater than first magnetic field threshold, and so as to be in an on state when said detected magnetic field is less than the second magnetic field threshold,
• a freewheeling diode, connected in parallel on the control coil,
• so that the magnetic field sensor and the control switch supply the control coil with a cut and modulated voltage when the assembly is connected to said source of continuous electrical energy in which:
• the magnetic field sensor is placed in the space surrounding the magnetic circuit to be crossed by the leakage magnetic flux,
• the magnetic field sensor is placed, relative to the magnetic circuit, in a position in which the leakage magnetic field is highly variable when the movable armature moves in the vicinity of its working state.

By such an arrangement, the magnetic field sensor and the control switch constitute, by their combination, an interface which is particularly economical and reliable, while being able to ensure effective regulation of the average control voltage of the control coil. so as to make it independent of the voltage of the continuous electric energy source such as the voltage of the on-board network of a motor vehicle. Indeed, both the magnetic field sensor and the control switch can be inexpensive electronic components.

In addition, by its position in the leakage magnetic flux, the magnetic field sensor does not modify the structure or the efficiency of the magnetic circuit, so that the energy required to power the control coil is reduced.

The particular choice of the position of the magnetic flux sensor makes it possible to guarantee a good sensitivity of the detection of the variations of the magnetic flux passing through the magnetic circuit, despite the fact that the detection is carried out in the leakage magnetic flux, which is lower than the main stream. This results in good operating reliability of the electromechanical actuator.

According to a first embodiment, the magnetic field sensor is placed in the space surrounding the movable armature, preferably opposite the first end of the fixed armature relative to the movable armature.

This position of the magnetic field sensor provides good detection sensitivity of the magnetic flux, and facilitates the manufacture of the electromechanical actuator while avoiding any discomfort in its assembly and possible adjustment.

• l'armature fixe comprend un noyau magnétique, engagé dans un passage axial de la bobine de commande, ayant une première extrémité formant ladite première extrémité de l'armature fixe, et ayant une deuxième extrémité,
• l'armature fixe comprend un circuit magnétique de retour, raccordé magnétiquement à la deuxième extrémité du noyau magnétique, et conformé pour conduire le champ magnétique principal entre la deuxième extrémité du noyau magnétique et l'armature mobile.

A second embodiment is also advantageous in the case of an electromechanical actuator in which:

• the fixed armature comprises a magnetic core, engaged in an axial passage of the control coil, having a first end forming said first end of the fixed armature, and having a second end,
• the fixed armature comprises a return magnetic circuit, magnetically connected to the second end of the magnetic core, and shaped to conduct the main magnetic field between the second end of the magnetic core and the movable armature.

In this case, the magnetic field sensor can be placed in the space surrounding the fixed armature in the vicinity of the second end of the magnetic core. This position of the magnetic field sensor provides good detection sensitivity of the magnetic flux.

Preferably, the first and second magnetic field thresholds are chosen so that, when the assembly is connected to the source of direct electrical energy, the voltage of which exceeds a cut-in voltage according to which the movable armature is moved to 'in its working state, the control coil is supplied with a chopped voltage having an average value little greater than said switch-on voltage.

In this way, the consumption of the electromechanical actuator is effectively reduced during the operating stages in the working state, while ensuring reliable operation, that is to say certain switching to the working state, and maintaining this working state, provided that the voltage of the continuous electric power source remains greater than the trigger voltage of the electromechanical actuator according to which the latter returns to the rest state.

According to an advantageous embodiment, the electromechanical actuator further comprises an element for adjusting the magnetic flux of leakage stressing the magnetic field sensor. For example, this leakage magnetic flux adjustment element urging the magnetic field sensor may comprise a part made of a material capable of conducting a magnetic field, said part being placed in an adjustable position in the vicinity of the magnetic field sensor. so as to modify the part of the leakage magnetic flux passing through the magnetic field sensor.

In this way, it is possible to adjust the value of the average supply voltage of the control coil during the stages during which the electromechanical actuator is in the working state, in particular in order to compensate for any dispersion of the thresholds. switching of magnetic field sensors.

To prevent the leakage magnetic flux adjustment element from reducing the efficiency of the magnetic circuit and / or inducing parasitic mechanical stresses on the moving armature, it is preferably placed away from any operational air gap. of the magnetic circuit.

Preferably, the electromechanical actuator according to the invention further comprises a magnetic shielding element, arranged opposite the magnetic circuit with respect to the magnetic field sensor. External disturbances liable to modify the magnetic field thresholds and the mean value of the supply voltage of the control coil which result therefrom are thus avoided.

It will be noted that the part constituting the flux adjustment element can itself fulfill the function of magnetic shielding.

In practice, in applications to electromechanical actuators in use in motor vehicles, the first magnetic field threshold can be chosen at a value of about 10 mT, and the second magnetic field threshold can be chosen at a value of about 8 mT.

Economically, the magnetic field sensor can advantageously be produced in the form of a digital Hall effect sensor, since such a component is reliable and inexpensive.

In this case, the control switch can advantageously be a bipolar transistor, the base of which receives the output signal from the digital Hall effect sensor, and the emitter-collector circuit of which is connected in series with the control coil. Indeed, such a control switch is reliable and inexpensive.

According to a first application, the electromechanical actuator according to the invention can comprise a movable armature having a part shaped to be mechanically coupled to an external element intended to be driven in movement by the electromechanical actuator.

According to a second application, in which the electromechanical actuator constitutes an electromechanical relay, the mobile armature can comprise a magnetic section of mobile armature, said magnetic section having a first end articulated according to a fixed hinge on the second end of the fixed frame to allow rotation of the movable frame between a working state and a resting state towards which it is returned by said return means, said magnetic section having a second end disposed opposite the first end of the fixed armature to be attracted by said first end of the fixed armature when the control coil is energized, the movable armature having a contact beam which extends up to a free contact end able to come to rest on a fixed working contact when the movable armature is in the working state.

BRIEF DESCRIPTION OF THE DRAWINGS

• [Fig.1] La figure 1 est une vue de côté en coupe selon l'axe de la bobine de commande, illustrant un actionneur électromécanique sous forme de relais électromécanique selon un mode de réalisation de l'invention, en état de repos ;
• [Fig.2] La figure 2 est un schéma électrique illustrant les composants électroniques d'une interface d'alimentation de la bobine de commande selon un mode de réalisation de la présente invention, et la connexion de ces composants entre la source d'alimentation à tension continue et la bobine de commande ;
• [Fig.3] La figure 3 est un schéma temporel illustrant l'effet de la présente invention sur la puissance consommée par la bobine de commande ;
• [Fig.4] La figure 4 est un schéma temporel illustrant la variation temporelle des courants électriques, tensions électriques et champ magnétique en divers points de l'interface d'alimentation de la figure 2 ;
• [Fig.5]. La figure 5 est une vue de côté en coupe selon l'axe de la bobine de commande, illustrant le flux magnétique dans un actionneur électromécanique à l'état de repos, selon un mode de réalisation à armature mobile à déplacement linéaire ;
• [Fig.6]. La figure 6 est une vue de côté en coupe selon l'axe de la bobine de commande, illustrant le flux magnétique dans l'actionneur électromécanique de la figure 5 à l'état de travail ;
• [Fig.7]. La figure 7 est une vue de côté en coupe selon l'axe de la bobine de commande, illustrant le flux magnétique dans un actionneur électromécanique à l'état de travail, selon un mode de réalisation à armature mobile à déplacement linéaire et muni d'un élément de réglage de seuil de champ magnétique, ledit élément de réglage étant en position d'action faible ;
• [Fig.8]. La figure 8 est une vue de côté en coupe selon l'axe de la bobine de commande, illustrant le flux magnétique dans l'actionneur électromécanique de la figure 7 à l'état de travail, l'élément de réglage de seuil de champ magnétique étant en position d'action forte ; et
• [Fig.9]. La figure 9 est une vue de côté en coupe selon l'axe de la bobine de commande, illustrant plusieurs choix de position et d'orientation du capteur de champ magnétique dans le flux magnétique de fuite environnant le circuit magnétique.

Other objects, characteristics and advantages of the present invention will emerge from the following description of particular embodiments, given in relation to the accompanying figures, among which:

• [ Fig. 1 ] The figure 1 is a side view in section along the axis of the control coil, illustrating an electromechanical actuator in the form of an electromechanical relay according to one embodiment of the invention, in the rest state;
• [ Fig. 2 ] The figure 2 is an electrical diagram illustrating the electronic components of a power supply interface of the control coil according to an embodiment of the present invention, and the connection of these components between the DC power source and the control coil ;
• [ Fig. 3 ] The figure 3 is a timing diagram illustrating the effect of the present invention on the power consumed by the control coil;
• [ Fig. 4 ] The figure 4 is a temporal diagram illustrating the temporal variation of electric currents, electric voltages and magnetic field at various points of the power supply interface of the figure 2 ;
• [ Fig. 5 ]. The figure 5 is a side view in section along the axis of the control coil, illustrating the magnetic flux in an electromechanical actuator in the rest state, according to an embodiment with a movable armature with linear displacement;
• [ Fig. 6 ]. The figure 6 is a side view in section along the axis of the control coil, illustrating the magnetic flux in the electromechanical actuator of the figure 5 in working state;
• [ Fig. 7 ]. The figure 7 is a side view in section along the axis of the control coil, illustrating the magnetic flux in an electromechanical actuator in the working state, according to an embodiment with a movable displacement armature linear and provided with a magnetic field threshold adjustment element, said adjustment element being in the low action position;
• [ Fig. 8 ]. The figure 8 is a side view in section along the axis of the control coil, illustrating the magnetic flux in the electromechanical actuator of the figure 7 in the working state, the magnetic field threshold adjusting element being in the strong action position; and
• [ Fig. 9 ]. The figure 9 is a side view in section along the axis of the control coil, illustrating several choices of position and orientation of the magnetic field sensor in the leakage magnetic flux surrounding the magnetic circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

On the figure 1 is schematically illustrated the structure of an electromechanical relay according to an embodiment of the present invention.

The electromechanical relay as shown on the figure 1 comprises a fixed armature 1, part of which is in the form of a magnetic core 2, a movable armature 3, a fixed working contact 4, a control coil 5, a contact beam 6 which forms a distal section of the armature movable 3 to a free contact end 7. The fixed armature 1 and the movable armature 3 together form the magnetic circuit of the electromechanical relay.

The control coil 5 comprises a coil carcass 51, integral with the fixed armature 1, and comprising a cylindrical axial passage 52 developing along a longitudinal axis II and in which the magnetic core 2 is engaged. A coil winding 53, consisting of an electrical conductor wound around the coil casing 51, is intended to be connected to an external source of nominal control voltage not shown in the figure.

A first end 21 of the fixed armature 1, or free end of the magnetic core 2, protrudes outside a first end of the axial passage 52 of the control coil 5, and constitutes an attractive pole capable of stressing the movable armature 3 A second end 22 of the magnetic core 2 protrudes out of a second end of the axial passage 52 of the control coil 5, and connects to a return magnetic circuit 1a which conducts the magnetic flux from the second end 22 of the magnetic core. 2 up to the mobile armature 3

The return magnetic circuit 1a comprises a transverse branch 1b of fixed armature 1 and a longitudinal arm 1c of fixed armature 1. The transverse arm 1b extends radially away from the second end 22 of the magnetic core 2, and is connected to the longitudinal branch 1c of fixed reinforcement which extends parallel to the longitudinal axis II as far as a second end 1d of a fixed frame against which a first end 31 of the mobile frame 3 bears.

The movable frame 3 comprises, from its first end 31, a magnetic section 32, developing parallel to the transverse branch 1b of the fixed frame 1, facing the first end 21 of the fixed frame 1, and structured so as to be attracted by the magnetic core 2 when the latter conducts a magnetic field generated by the control coil 5 which has been supplied with electrical energy. The magnetic section 32 has the general shape of a bar, having a second end 33 disposed facing the magnetic core 2.

The fixed armature 1 comprises a ferromagnetic material capable of conducting a magnetic flux generated by the control coil 5 in the magnetic core 2. The movable armature 3 itself comprises, in its magnetic section 32, a ferromagnetic material, and closes thus at least partially the magnetic flux generated in the magnetic core 2.

The contact beam 6, which extends the magnetic section 32 of the mobile armature 3, extends beyond the magnetic section 32 of the mobile armature 3, away from the first end 31 of the mobile armature 3, up to a free contact end 7 which is located opposite the fixed working contact 4, itself integral with the coil casing 51.

The contact beam 6, in the illustrated embodiment, comprises a leaf spring 61, in the form of a flat strip made of bronze / beryllium alloy, which has the advantage of good elastic properties and good electrical conduction properties. The leaf spring 61 is fixed by fixing means, along one of its two main faces, on the magnetic section 32 of the movable armature 3. In the embodiment illustrated in FIG. figure 1 , the fixing means comprise a lug 35 of the magnetic section 32 engaged by force in a slot 62 of the leaf spring 61.

The leaf spring 61 is extended beyond said second end 33 of the magnetic section 32, away from the free contact end 7, by an arcuate section 64 followed by a longitudinal section 65 generally parallel to the longitudinal branch 1c of the fixed armature 1 and to which it is fixed with the interposition of a common plug 8 forming one of the terminals of the electric power circuit of the electromechanical relay. By this arrangement, the leaf spring 61 constitutes elastic return means 9 of the movable armature 3.

Because of its support by its first end 31 on the second end 1d of the fixed frame 1, and because of its retention by the elastic return means 9, the movable frame 3 is articulated by its first end 31 according to hinge means constituted by the second end 1d of the fixed frame 1, and can thus pivot between a state of rest illustrated on figure 1 and a working state in which the mobile armature 3 has pivoted and comes into contact with the first end 21 of the mobile armature 1. The elastic return means 9 ensure the return of the mobile armature 3 to its rest state . The hinge means also ensure the conduction of the magnetic flux between the fixed armature 1 and the mobile armature 3.

The free contact end 7 of the contact beam 6 is provided with a contact pad 71 made of an electrically conductive material and having good anti-wear properties. Likewise, the fixed working contact 4 is formed by a fixed pad 41 made of an electrically conductive material and having good anti-wear properties. The fixed pad 41 is secured to a work plug 10 constituting the second connection terminal of the power circuit of the electromechanical relay.

In the illustrated embodiment, a rest stop 11 limits the movement of the free contact end 7 away from the fixed working contact 4.

In the state of rest shown on the figure 1 , the control coil 5 is not powered, and does not produce any magnetic field in the magnetic core 2. Thus, the movable armature 3 is not attracted by the magnetic core 2, and, by the stressing of the means of elastic return 9, remains away from the magnetic core 2 and comes to bear against the rest stop 11. This results in the presence of an operational air gap 200, that is to say of an air gap whose presence or the dimension is necessary for the operation of the electromechanical actuator.

In the working state, the control coil 5 is supplied with a nominal control voltage, and produces in the magnetic core 2 a magnetic field sufficient to attract the movable armature 3, against the return stress exerted. by the elastic return means 9, until the movable armature 3 comes into contact with the first end 21 of the fixed armature 1, thus closing the magnetic circuit 1, 3. In this position, the contact pad 71 of the free contact end 7 bears against the fixed pad 41 of the fixed working contact 4, causing a bending or bending of the adjacent section of the leaf spring 61 located between the free contact end 7 and the fixing means 35, 62.

In this way, in the working state, the contact pad 71 of the free contact end 7 bears against the fixed pad 41 of the fixed work contact 4 according to a working force determined essentially by the stiffness characteristics. leaf spring 61, and by the length and amount of bending of the adjacent section of leaf spring 61.

According to the present invention, the control coil 5 is supplied from a source of continuous electrical energy through an interface 100 ensuring the regulation of its average supply voltage, whatever the variations of the voltage d. 'input from the DC voltage power source.

The interface 100 comprises a magnetic field sensor, advantageously of the digital Hall effect sensor 101 type, and a switch 102. In the embodiment illustrated in FIG. figure 1 , the digital Hall-effect sensor 101 is arranged in the space surrounding the mobile armature 3, away from the operational air gap 200 between the mobile armature 3 and the magnetic core 2, opposite the magnetic core 2 relative to the movable armature 3, to be stressed by the magnetic flux of leakage passing through this zone. The digital Hall effect sensor 101 drives the switch 102, which is connected in series with the control coil 5. The digital Hall effect sensor 101 is of a type which produces at its output Vout a zero voltage when the magnetic flux which the traverse exceeds a first magnetic field threshold, and which produces at its output Vout a maximum voltage when the magnetic flux which passes through it is less than a second magnetic field threshold.

An example of interface circuit 100 is illustrated in figure 2 . The input terminals 103 and 104 of the interface circuit 100 are respectively connected to the positive terminal Vcc and to the negative terminal GND of a direct voltage electric power source such as the on-board network of the motor vehicle, with interposition of an external switch T2 such as a bipolar transistor which is not part of the interface 100. The output terminals 105 and 106 of the interface 100 are connected to the terminals of the control coil 5.

In the interface circuit 100 shown in figure 2 , the digital Hall effect sensor 101 is supplied between the positive 103 and negative 104 input terminals with the interposition of a resistor Rs. The output Vout of the digital Hall effect sensor 101 is connected to the positive terminal 103 via of a resistor R, and is connected to the base of a bipolar switching transistor T1 whose emitter is connected to the negative terminal 104 and whose collector is connected to one of the terminals of the control coil 5. A freewheeling diode D is connected in anti-parallel to the terminals of the control coil 5.

We now consider the figures 5 and 6 , illustrating the magnetic leakage flux passing through the digital Hall effect sensor 101, respectively in the rest state and in the working state of an electromechanical actuator according to an embodiment of the present invention. In this embodiment, the Hall effect sensor digital 101 is arranged in the same position as in the embodiment of the figure 1 . On the figure 5 , from the rest state, the control coil 5 is first of all weakly supplied, according to a supply which increases to pass to the working state illustrated in the figure. figure 6 . So on the figure 5 , the magnetic flux of leakage passing through the digital Hall effect sensor 101 is almost nonexistent, or remains weak, and the digital Hall effect sensor 101 produces on its output Vout a high voltage which saturates the switching transistor T1 to enable the power supply control coil 5 and to put the electromechanical actuator in its working state.

In the working state shown on the figure 6 , the digital Hall effect sensor 101 is crossed by a magnetic flux of higher value leakage. The digital Hall effect sensor 101 produces at its output a voltage Vout which becomes zero and which turns off the switching transistor T1 when the leakage magnetic flux exceeds a first magnetic flux threshold, and produces at its output a higher voltage Vout which saturates the switching transistor T1 when the leakage magnetic flux drops below a second magnetic flux threshold which is itself lower than the first magnetic flux threshold.

As a result, the switching transistor T1 blocks the power supply to the control coil 5 when the magnetic field detected by the digital Hall effect sensor 101 exceeds a first magnetic field threshold S1 ( figure 4 ), and the switching transistor T1 powers the control coil 5 again when the magnetic field detected by the digital Hall effect sensor 101 drops below a second magnetic field threshold S2 ( figure 4 ). The value of the first magnetic field threshold S1 and the value of the second magnetic field threshold S2 together determine the average value of the control voltage applied to the control coil 5 during the work sequences. This achieves a regulation of the average value of the leakage magnetic field passing through the Hall effect sensor 101, and simultaneously a regulation of the average value of the main magnetic field produced by the control coil 5.

By correctly choosing the values of the first S1 and second S2 magnetic field thresholds, it is thus possible to adjust to an appropriate value the main magnetic field produced by the control coil 5 during the working steps. This magnetic field can advantageously be chosen to be slightly greater than the magnetic field producing the switching of the electromechanical actuator towards a working state.

On the other hand, it will be advantageous to choose first and second magnetic field thresholds relatively close to each other, to avoid the risk of an untimely tilting of the electromechanical actuator towards its rest state.

On the figure 3 , the limitation of power P consumed by the control coil 5 of the electromechanical actuator in the working state during a variation of the voltage Vcc of the DC voltage supply source has been illustrated. It can be seen that the power consumed by the control coil 5, illustrated by the dotted curve, follows the variations in the voltage Vcc of the power source when the latter is less than a regulation limit voltage VR, in the species equal to approximately 9 V, but remains constant at a value PM when the voltage Vcc exceeds the regulation limit voltage VR, thus avoiding overconsumption of energy while correctly maintaining the electromechanical actuator in its working state.

On the figure 4 , there is shown, in correspondence with each other, time diagrams illustrating the operation of the regulation interface of the figure 2 . Diagram A illustrates a possible variation of the voltage Vcc of the DC voltage supply source, with an A1 sequence at the usual voltage of an on-board motor vehicle network, for example 13 V, with an A2 sequence at plus voltage high, with an A3 sequence at lower voltage, and with an A4 sequence at decreasing voltage. Diagram B illustrates the external control signal, for example the voltage on negative terminal 104 produced by transistor T2, indicating by a negative voltage step the instant from which the external control controls the switching of the electromechanical actuator towards his working state. Diagram C illustrates the waveform of the magnetic field seen by digital Hall effect sensor 101. Diagram D illustrates the idle or working state of the electromechanical actuator. Diagram E illustrates the waveform of the output signal Vout of digital Hall effect sensor 101. Diagram F illustrates the conduction state of transistor T1 supplying control coil 5. Diagram G illustrates the waveform of the electric current flowing through the control coil 5. Diagram H illustrates the variation in the average value of the electric current flowing in the control coil 5. Diagram I illustrates the waveform of the electric voltage at the terminals of the control coil 5.

We can consider in particular the diagram C, on which we see the variation of the magnetic field seen by the digital Hall effect sensor 101, this variation taking place between the first magnetic field threshold S1 and the second magnetic field threshold S2. The variation of the magnetic field is relatively slow during the first sequence A1 at medium voltage Vcc from the power source, while it is relatively fast during the second sequence A2 at higher voltage Vcc from the power source, and becomes even slower during the third sequence A3 at lower voltage Vcc.

We can also consider the diagram G, illustrating the electric current passing through the control coil 5, and which has the same waveform as the diagram C of the magnetic field. The falling edges of the current correspond to the periods of blocking of the transistor T1 and of conduction of the freewheeling diode D. This sequence has a substantially constant duration whatever the value of the voltage Vcc of the power source. On the other hand, the rising edges of the electric current are more or less rapid depending on the supply voltage Vcc.

The diagrams show how the interface according to the invention produces a modulated and regulated supply of the control coil 5 during the driving periods in the working state.

We now consider the figures 7 and 8 , illustrating the effect obtained by an adjustment element 110 such as a plate made of a material capable of conducting a magnetic field and placed in the vicinity of the Hall effect sensor 101, opposite the movable armature 3. On the figure 7 , when the adjustment element 110 is relatively far from the Hall effect sensor 101, the leakage magnetic flux is not affected by the adjustment element 110, and passes through the Hall effect sensor 101 at a low flux value . On the other hand, when the adjustment element 110 is closer to the Hall effect sensor 101, as illustrated in figure 8 , the flux lines are deflected by the adjustment element 110 and as a result the magnetic leakage flux which passes through the Hall effect sensor 101 is higher. It is therefore understood that the adjustment element 110 makes it possible to modify the first magnetic field threshold S1, and therefore to modify the average value of the voltage applied to the control coil 5 during the working steps.

We now consider the figure 9 , illustrating several choices of position and orientation of the magnetic field sensor in the leakage magnetic flux surrounding the magnetic circuit in the embodiment of figures 5 and 6 .

Position 101 is the position chosen in the embodiments of the figures 1 , 5 and 6 , In this case, the magnetic field sensor 101 is in the vicinity of the movable armature 3, opposite the magnetic core 2 with respect to the movable armature 3. The position 1010 is opposite with respect to the circuit magnetic 1, 3, that is to say in the space surrounding the fixed armature 1 in the vicinity of the second end 22 of the magnetic core 2. Position 1011 is in space surrounding the fixed frame 1 in the vicinity of an intermediate portion of the longitudinal branch 1c, a position similar to that described in the document GB 2 259 188 . Position 1012 is close to position 1011, but with a perpendicular orientation of the magnetic field sensor. Position 1013 is in the space surrounding a junction air gap between the fixed armature 1 and the movable armature 3. Position 1014 is similar to position 1013, but with a perpendicular orientation of the magnetic field sensor.

Tests were carried out on an electromechanical relay having a structure as described on the figure 9 , by measuring the magnetic field picked up by a Hall effect magnetic field sensor placed in the various positions defined above, by varying the electric voltage applied to the control coil 5, successively from a low voltage in which the electromechanical relay is in the rest position (rep), then a voltage producing the movement of the mobile armature to the electric contact position (Tr), then an increasing series of voltages by which the magnetic circuit remains closed (Mag1, Mag2, Mag3 , Mag4) by the contact between the mobile armature 3 and the fixed armature 1.

The table below gives the result of the measured magnetic field values (in Gauss) as a function of the coil voltage (in Volts) producing the various successive positions of the moving armature 3: 101 1010 1011 1012 1013 1014 position Ubobin Hall 101 Hall 1010 Hall 1011 Hall 1012 Hall 1013 Hall 1014 rep 4 2 38 20 5 13 30 Tr 4.15 20 48 20 8 15 24 Mag1 4.3 44 70 24 10 19 15 Mag2 6 65 96 25 13 28 36 Mag3 8 80 124 25 16 32 43 Mag4 10 105 168 25 19 35 46

These results show that the positions 101 and 1010 are clearly preferable to the other positions 1011, 1012, 1013 and 1014, because the magnetic field is highly variable there (more than 30%) when the mobile armature 3 moves in the vicinity of its state. working, that is to say in the vicinity of the positions Tr and Mag1. This is the reason why we will choose to place the magnetic field sensor in a position close to position 101 or in a position close to position 1010. A position close to position 101 may be preferred if it is necessary to leave l access to the second end 22 of the magnetic core 2 during assembly of the electromechanical relay.

The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variations and generalizations contained within the scope of the following claims.

Claims (15)

Electromechanical actuator comprising: - a magnetic circuit (1, 3), having a fixed armature (1) capable of conducting a main magnetic flux between a first end (21) and a second end (1c), and having a movable armature (3) engaged between the first end (21) and the second end (1c) of the fixed frame (1), the mobile frame (3) being able to be moved according to a relative movement with respect to the fixed frame (1) between a working state and a rest state towards which it is recalled by return means (9), the magnetic circuit (1, 3) being able to conduct the major part of said main magnetic flux, a leakage magnetic flux passing through the space surrounding the magnetic circuit (1, 3), - a control coil (5), arranged so as to generate, when supplied from a continuous electrical energy source, a magnetic flux comprising said main magnetic flux conducted by the magnetic circuit (1, 3) and comprising said leakage magnetic flux passing through the space surrounding the magnetic circuit (1, 3), - a magnetic field sensor (101), placed so as to be biased by said magnetic flux generated by the control coil (5), - the magnetic field sensor (101) being structured to produce an output signal having a first signal value and a second signal value, the output signal switching to its first signal value if the detected magnetic field becomes greater at a first magnetic field threshold (S1), the output signal switching to its second signal value if the detected magnetic field becomes less than a second magnetic field threshold (S2), the first magnetic field threshold (S1) being greater than the second magnetic field threshold (S2), - a control switch (T1), connected in series between said source of continuous electrical energy and said control coil (5), and controlled by the signal from the magnetic field sensor (101), so as to be in a off state when said detected magnetic field is greater than the first magnetic field threshold (S1), and so as to be in an on state when said detected magnetic field is below the second magnetic field threshold (S2), - a freewheeling diode (D), connected in parallel on the control coil (5), - so that the magnetic field sensor (101) and the switch control (T1) supply the control coil (5) with a chopped and modulated voltage when the assembly is connected to said source of continuous electrical energy characterized in that : - the magnetic field sensor (101) is placed in the space surrounding the magnetic circuit (1, 3) to be crossed by the leakage magnetic flux, - the magnetic field sensor (101) is placed, relative to the magnetic circuit (1, 3), in a position in which the leakage magnetic field is highly variable when the movable armature (3) moves in the vicinity of its working state. Electromechanical actuator according to Claim 1, characterized in that the magnetic field sensor (101) is placed in the space surrounding the movable armature (3). Electromechanical actuator according to claim 1, characterized in that the magnetic field sensor (101) is placed in the space surrounding the movable armature (3), opposite to the first end (21) of the fixed armature (1) relative to the movable frame (3). Electromechanical actuator according to Claim 1, characterized in that : - the fixed armature (1) comprises a magnetic core (2), engaged in an axial passage of the control coil (5), having a first end forming said first end (21) of the fixed armature (1), and having a second end (22), - the fixed armature (1) comprises a return magnetic circuit (1a), magnetically connected to the second end (22) of the magnetic core (2), and shaped to conduct the main magnetic field between the second end (22) of the magnetic core (2) and the mobile armature (3), - the magnetic field sensor (101) is placed in the space surrounding the fixed armature (1) in the vicinity of the second end (22) of the magnetic core (2). Electromechanical actuator according to any one of claims 1 to 4, characterized in that the first and second magnetic field thresholds (S1, S2) are chosen such that, when the assembly is connected to the source of continuous electrical energy whose voltage exceeds a cut-in voltage according to which the movable armature (3) is moved to its working state, the control coil (5) is supplied according to a cut-off voltage having an average value little greater than said cut-in voltage. Electromechanical actuator according to any one of claims 1 to 5, characterized in that it comprises an element (110) for adjusting the leakage magnetic flux stressing the magnetic field sensor (101). Electromechanical actuator according to Claim 6, characterized in that said element (110) for adjusting the leakage magnetic flux urging the magnetic field sensor (101) comprises a part made of a material capable of conducting a magnetic field and placed in an adjustable position. in the vicinity of the magnetic field sensor (101) so as to change the part of the leakage magnetic flux passing through the magnetic field sensor (101). Electromechanical actuator according to Claim 7, characterized in that said magnetic leakage flux adjustment element (110) is away from any operational air gap (200) of the magnetic circuit (1, 3). Electromechanical actuator according to any one of Claims 1 to 8, characterized in that it comprises a magnetic shielding element arranged opposite the magnetic circuit (1, 3) with respect to the magnetic field sensor (101). Electromechanical actuator according to Claim 9 in its attachment to Claims 7 or 8, characterized in that the shielding element is produced by the element (110) for adjusting the magnetic leakage flux. Electromechanical actuator according to any one of claims 1 to 10, characterized in that the first magnetic field threshold (S1) is chosen at a value of approximately 10 mT, and in that the second magnetic field threshold (S2) is chosen at a value of about 8 mT. Electromechanical actuator according to any one of claims 1 to 11, characterized in that the magnetic field sensor (101) is a digital Hall effect sensor. Electromechanical actuator according to Claim 12, characterized in that the control switch (T1) is a bipolar transistor whose base receives the output signal from the digital Hall effect sensor (101) and whose emitter-collector circuit is connected in series with the control coil (5). Electromechanical actuator according to any one of Claims 1 to 13, characterized in that the movable armature (3) comprises a part shaped to be mechanically coupled to an external element intended to be driven in movement by the electromechanical actuator. Electromechanical actuator according to any one of claims 1 to 13, characterized in that the movable armature (3) comprises a magnetic section (32) of movable armature, said magnetic section (32) having a first end (31) articulated according to a fixed hinge on the second end (1d) of the fixed frame to allow rotation of the movable frame (3) between a working state and a rest state towards which it is returned by said return means (9) , said magnetic section (32) having a second end (33) disposed opposite the first end (21) of the fixed armature (1) to be attracted by said first end (21) of the fixed armature when the coil of control (5) is supplied, the mobile armature (3) having a contact beam (6) which extends to a free contact end (7) able to come to bear on a fixed working contact (4) ) when the movable armature (3) is in the working state, the electromechanical actuator constitutes a t then an electromechanical relay.

Images