EP1771868A1

EP1771868A1 - Electromagnetic control device operating by switching

Info

Publication number: EP1771868A1
Application number: EP05787407A
Authority: EP
Inventors: Jean-Paul Yonnet; Christophe Baldi; Christophe Fageon
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2004-07-16
Filing date: 2005-07-04
Publication date: 2007-04-11
Also published as: JP2008507121A; FR2873232A1; JP4902535B2; FR2873232B1; US7804386B2; US20070247264A1; WO2006016081A1

Abstract

The invention relates to an electromagnetic control device for the opening and closing of a mechanical element, particularly a valve of an internal combustion engine. The positioning of the mechanical element in at least one position (open or closed) is achieved by the action of at least one solenoid (90) acting on a plate controlling the position of the mechanical element. The device has at least two gaps which are closed by the plate on the positioning of the mechanical element in at least one position, the plate being mounted to rotate such that the axis of rotation of the plate is between the two gaps. The device also has at least one permanent magnet (99b) to polarize the device such as to hold the plate in at least one position in the absence of current through the solenoid (90), said permanent magnet (99b) not being crossed by the principal magnetic flux (92) of the solenoid (90).

Description

the

ELECTROMAGNETIC CONTROL DEVICE OPERATING IN TENSION

The present invention relates to an electromagnetic control device for opening and closing a mechanical element, in particular an internal combustion engine valve. In such a device also called an actuator, the positioning of the mechanical element in at least one position (open or closed) is obtained by the action of an electromagnet acting on a plate, including a magnetic material, and controlling the positioning of the mechanical element.

Known devices of this type operate in such a way that the plate moves in translation or in rotation around an axis of rotation situated outside the zone of the airfoils of the electromagnets and thus assimilable to a translational movement of the plate.

The electromagnetic dimensioning of an actuator is conditioned by the force it must exert. This force is related to the course of the plateau and the mass of the latter. In Indeed, the mass of the plate conditions its travel time and therefore imposes the stiffness of the return springs intended to participate in the actuation of the plate. The force of the electromagnetic control device is directly coupled with the force of the return springs since the actuator must be able to exert a force greater than that of the springs to hold the plate in position.

It is observed that the greater the stiffness of the springs to obtain an imposed plateau travel and imposed travel time will be important, the larger the size of the actuator will be important.

The present invention results from the observation that the greater the mechanical performance of a known electromagnetic control device, the more bulky this device.

It relates to a device having at least first and second gaps of variable thickness to be closed by the plate during positioning of the mechanical element in at least one position, the plate being rotated so that the The axis of rotation of the plate passes between the first and second air gaps.

In such a configuration, it is noted that at comparable exerted force, the inertia of the plate is smaller than for a device operating in translation. Indeed, in the devices in translation, the entire plate moves the entire race. Instead, in a device where the plate is rotatably mounted about an axis positioned between the two air gaps, the two ends of the plate move the entire stroke but the points of the plate located on the axis of rotation are immobile. The average displacement is then half that observed in a device in translation. the the

This reduction in inertia results in a reduction in the stiffness of the springs and consequently in the size of the device.

The second position of the mechanical element is such that the gaps are open or said large air gaps. A closed air gap is also called a low air gap.

In one embodiment of the invention, the device includes a third and a fourth gap of variable thickness to be closed by the plate during the positioning of the mechanical element in the second position, the axis of rotation of the plate passing between the first, second, third and fourth gaps.

In this implementation, the two positions of the valve are controlled by the plate which oscillates angularly between two positions controlled by similar means.

Advantageously, the second position of the mechanical element is obtained by the action of a second electromagnet acting on the plate. This first embodiment, without a permanent magnet, is called a non-polarized actuator. In another embodiment, the device comprises at least one permanent magnet for polarizing the device in the absence of current in the electromagnet and to linearize the operation of the system.

In this so-called polarized embodiment, the maintenance of the mechanical element in an open or closed position is ensured by the permanent polarization generated by the permanent magnet even in the absence of a current flowing in the coil. In this case, the actuator is called polarized.

In a polarized embodiment, the magnetic flux generated by the electromagnet passes through the permanent magnet. This embodiment is called series polarization.

Advantageously, the permanent magnet is thin.

In another polarized embodiment, the magnetic flux generated by the electromagnet does not cross the the the

directly the permanent magnet. This embodiment is called parallel polarization.

In another embodiment of the invention, the permanent magnet, although placed out of the magnetic circuit of the electromagnet, is traversed by the magnetic flux generated by

The electromagnet so that said flow passes through two closed air gaps.

Finally, the magnetic material included in the plate is advantageously a ferromagnetic material.

According to another aspect, the invention relates to a device for electromagnetic control of the opening and closing of a mechanical element, the positioning of the mechanical element in at least one position (open or closed) being obtained by the action of at least one electromagnet acting on a plate including a magnetic material and controlling the positioning of the mechanical element, this device comprising: at least a first and a second gap of variable thickness to be closed by the plate during the positioning the mechanical element in at least one position, the plate being mounted in rotation so that the axis of rotation of the plate passes between the first and second air gaps, and - at least one permanent magnet for biasing the device so as to maintain the plate in at least one position in the absence of current in the electromagnet, this permanent magnet not being traversed by the magnetic flux main electromagnet.

According to one embodiment of the invention, the magnetic flux generated by electromagnet passes through an air gap devoid of permanent magnet and located in parallel with an air gap containing a permanent magnet. The fact that the magnetic flux does not pass through the permanent magnet makes it possible not to demagnetize this magnet, since it is not subject to significant demagnetizing fields.

According to one embodiment, the magnetic flux generated by the electromagnet passes, in addition to the air gap located in parallel with the permanent magnet, the two air gaps closed by the plate during its tilting in a position. The closed air gaps traversed by the flux are seen by the coils as relatively small, which makes the contribution of the coils more efficient in terms of efficiency since the magnetic flux thus encounters a smaller reluctance than if it passed through large gaps such as the coils. air gaps left open by the plateau.

Other characteristics and advantages of the invention will become apparent with the description given below, the latter being carried out for descriptive and non-limiting purposes with reference to the following drawings in which:

FIG. 1 illustrates the operation of an electromagnetic control device according to the invention;

Figures 2a and 2b are intended to illustrate the advantage produced by the invention with respect to a device operating in translation;

Figures 3 to 9 show seven embodiments of the invention;

Figure 10 shows a perspective view of an exemplary embodiment of the invention.

In the figures, the magnetic circuits and the magnetic fluxes are represented by a closed curve referenced for the sake of clarity by the same reference. Indeed, the magnetic circuit is a circuit that can channel a magnetic flux. The arrow on such a closed curve indicates the direction of polarization magnetic flux. The magnetic fluxes are represented in the cutting plane of the plate.

The symbols used are identical for all the figures. The double arrows represent the directions of the polarization fluxes in the permanent magnets and the directions of the induction fluxes created by these permanent magnets in the air gaps. The simple arrows represent the directions of the induction fluxes generated by the coils in the air gaps. The devices described preferably have a linear behavior and preferably operate without magnetic saturation to allow a high controllability of the device. Proper sizing of the different elements of the devices allow such behaviors.

FIG. 1 shows the simplest embodiment of the invention in which positioning of the mechanical element 17 in a position (open or closed) is obtained by the action of an electromagnet 10 including a first coil 11 and a first magnetic circuit 12. The electromagnet 10 acts on a plate 13 including a magnetic material, preferably a ferromagnetic material. A permanent magnet may also possibly be included in the tray. The positions 13 ₁ and 13 ₂ of this plate 13 control the positioning of the mechanical element 17. The device has two so-called first air gaps 14a and 14b air gaps. These air gaps 14a and 14b are intended to be closed by the plate 13 during the positioning of the mechanical element in the open or closed position which corresponds in the figure to the position 13i of the plate 13. The plate 13 is rotatably mounted to move from a position 13i to the other 13 ₂ so that the axis of rotation 15 of the plate 13 is between the first and the second gap 14a and 14b.

In the case where the mechanical element 17 is a valve 17, as shown in FIG. 1, the connection of the plate 13 with the valve 17 is performed using a hinge 16 between a valve stem 17a and the plate 13. The hinge 16 is placed at one end of the plate 13. When the plate passes from a position to the other, the valve stem 17a is linearly reciprocated and drives the valve head 17b. Springs 18a and 18b and attachment of the springs 19 allow the return movement of the valve 17.

The setting in position 13i is carried out when a current flows in the first coil 11. The holding in position can be achieved through the circulation of such a stream or, as described later, using a polarization carried out using a permanent magnet inserted in the magnetic circuit 12 of the electromagnet 10 or in its vicinity. Positioning 13 ₂ may be performed by means other than electromagnetic, for example, mechanical or by electromagnetic means other than or similar to that shown in FIG.

To highlight the advantages that a device according to the invention provides, it is firstly noted that the dimensioning of the valve control devices is completely determined with two external parameters: the stroke and the half period (that is, say the time taken by the valve to go from one position to another). The stroke of the valve is defined by the operation of the engine. This race 2zo (see Figure 2a and 2b) is imposed.

Knowing the stiffness of the springs and the race, we obtain directly the force that these springs exert. F = k Z ₀

The electromagnetic device must be able to exert a force greater than that of the springs to maintain the plate in one of the two positions. This electromagnetic force is directly proportional to the section S of the gaps. S = F / α

The coefficient α is classically of the order of 10 N / cm ² , 160 at the most.

The mass of the plate is directly a function of this section of the electromagnetic gaps because the section of the plate must be sized to pass the magnetic flux. m = p β S ^3/2 where p is the density of the material of the plate, and β a form factor.

As for the stiffness k springs, it is directly related to the half period and the mass of the plateau. k = m (2π / T) ²

This half period T / 2 is related to the operation of the engine. It is of the order of 3 ms.

The relations of proportionality presented are only a first approximation.

These relationships show especially that the dimensioning of the device, the mass of the plate and the stiffness of springs are directly related to the course of the plateau and the half-period.

FIGS. 2a and 2b illustrate the advantage that a rotating configuration according to the invention has with respect to a configuration in translation such as those encountered in the state of the art and meeting the problems of inertia explained above.

We will first study the operation of the plate in translation. Its motion is solution of the equation: md ² z / dt ² + kz = 0 The solution, which corresponds to a free oscillation of the plateau, is of the type: z = Z ₀ cos ω t with Where ² = k / m

For speed, we get: dz / dt = Z ₀ ω cos ω t The energy stored by the compressed spring is worth at the end:

E _r = H k Z ₀ ²

As for the kinetic energy, it is maximum at mid-race:

E _ct = H mv ² = H m Where ² Z ₀ ²

The equality of the two energies makes it possible to verify that an oscillating system functions well by exchange between the potential energy stored in the springs and the kinetic energy of the plate.

In the case of a device in rotation (or tilting), to make the comparison with the device in translation, it will be assumed that the valve is pushed by the end of the plate, whose displacement will be between -z ₀ and + z ₀ .

To obtain the same movement time of the valve between the two positions, it is necessary that the tangential speed of the end of the plate is the same as for the devices in translation. By equating the bow with the string, which is justified for the small angles of rotation, we get at the end of the plateau the speed of: dz / dt = Z ₀ ω cos ω t

The "tilting - translation" comparison will be performed at the same stroke and at the same maximum speed. We will compare the kinetic energies stored halfway.

If the plate has a uniform section S and a length 2L (Figure 9), if we set the position of the element dx by its position x (x is between -1 and +1), the speed of this element dx is given by:

V (x) = dz / dt (x) = Z ₀ x ω cos ω t

In the middle of the race, the maximum kinetic energy of this element dx is given by: dE _cb = H (p SL dx) (Z ₀ x ω) ² = H p SLZ ₀ ² Cû ² x ² dx By integrating dE _c for x varying from -1 to +1, we obtain the value of the maximum kinetic energy:

E _cb = H (p S 2 L) Z ₀ ² ω ² (1/3)

The term (p S 2 L) represents the mass m of the plateau, from which:

E _cb = H (m / 3) Z ₀ ² Where ²

In comparison with the system in translation, the equivalent mass of the plate is divided by 3. The inertia is thus divided by 3. With the same plate, to have the same speed, it is necessary that the stiffness of the springs is divided by 3 .

And if we consider the dependence between the force of the springs, the attraction surface of the devices, the mass of the plate, the stiffness of the springs, the introduction in the loop by a factor 1/3 leads to a very notable decrease of the size of the device.

The factor 3 on the mass must however be reduced by a coefficient of effectiveness of the force of the device.

Indeed, on a translational control device, the force of each air gap is a fully usable axial force. It is not the same for a tilting device. If we want to compare the forces, we must reduce the force exerted at the end of the plateau, equivalent torque. The attraction force of the device is exerted on the contact surface between the plate 13 and the part of the magnetic circuit that comes into contact with the low-gap plate.

According to Figure 1, the area in contact varies from x _o L to L.

The equivalent force brought back to the end is then multiplied by a coefficient of efficiency γ = ^ (1 + x ₀ ).

For a real system, the parameter Xo should be around 0.3, which corresponds to 0.65 for the coefficient γ. The real gain is only 2/3 of the gain of 3 obtained on the equivalent mass of the plateau. Overall, this results in a gain of around a factor of 2.

In the worst case, when Xo is very small, this coefficient γ remains greater than 0.5. The overall gain is therefore always greater than 1.5.

As shown in Figure 1, in a tilting device according to the invention, the valve is, for example, connected by a rod-type system at the end of the plate. The return springs are then arranged along the axis of the valve.

In the exemplary embodiments described below, electromagnetic means according to the invention are used for positioning in both positions of the valve. In this case, the plate operates between four gaps that function in attraction two by two and alternately.

The exemplary embodiments are based on the different possibilities of circulation of polarization flux in the air gaps, the different possibilities of circulation of excitation flux generated by the coils in the air gaps when the polarization has been defined, the arrangement of the coils relative to to the device and the arrangement of the permanent polarization magnets of the device.

FIGS. 3, 4 and 5 show three devices operating on a principle similar to that shown in FIG.

FIG. 3 shows a case of non-polarized device with four gaps where the two positions of the plate 33 are controlled by two electromagnets 30 and 36, respectively comprising a first and a second coil 31 and 37 and a first and second magnetic circuit 32 and 38 Four air gaps 34a, 34b and 34c, 34d are therefore present in the two magnetic circuits 32 and 38 and intended to be closed alternately, two by two, depending on the position of the plate 33 and therefore the valve. This unpolarized configuration is in fact a double basic system similar to that described in Figure 1.

In the example of FIG. 4, permanent magnets 49a and 49b have been added to a device as shown in FIG. 3. They allow polarization of the magnetic circuits 42 and 48 of the electromagnets 40 and 46 in the absence of current. circulating in the coils 41 and 47. Such polarization allows a holding position of the plate 43 without additional energy consumption or reduced energy consumption. Indeed, thanks to the polarization, the flow of current in the coils is not necessary during the holding in position.

The polarized control devices thus allow easy control of the intensity of the currents, in particular with a low air gap (or closed air gap) where the plate can be maintained without effort.

The polarization is called series when the flux of a bias magnet is in series with the flow of the coil for performing the actuation of the device. We are dealing with a serial configuration. The configurations shown in Figure 4 and Figure 5 are examples of such polarization. These examples have the advantage of being simple configurations of construction even if the magnetic circuits which carry the coils are rather complex, because crisscrossed.

In the case of serial configurations, it is advantageous for the magnets to be as thin as possible in order to maintain a good efficiency of the ampere turns of the coils. Indeed the magnets constitute an additional gap for the amp turns generated by the coils. On the other hand, the magnets are subjected to demagnetizing fields which can be important when the fields of the coils are in opposition with their magnetization.

The polarization is said to be parallel when the magnetic flux generated by the coil does not cross or passes through only a small part of a polarization magnet. The examples shown in FIGS. 6 to 9 are examples of such polarization. The configuration is then called parallel.

In FIGS. 8 and 9, an optimization of the polarization is obtained thanks to a configuration called a parallel series.

In Figure 4, the permanent magnets are such that the flux generated by their presence in the magnetic circuits 42 and 48 rotate in the same direction. It is assumed, as shown in FIG. 4, that the air gaps 44a and 44b are almost closed and that the position of the plate is such that the air gaps 44c and 44d are substantially equal to the end-of-plate travel, ie say about 8 mm. The permanent bias magnet 49a creates a magnetic flux 42 flowing in a closed circuit. Polarization inductions Bpa and Bpb are therefore high in air gaps 44a and 44b.

In the gaps 44c and 44d, the induction Bpc and Bpd is lower because the magnet 49b sees a relatively large air gap, but it is not zero. This induction generates a fairly weak force which slightly reduces the main attraction force generated by the magnet 49a. The use of rather thin magnets allows this force to be very reduced. When the coil 41 is energized, the inductions Bba and Bbb in the air gaps 44a and 44b add (or retract in the direction of the current) to the induction due to the polarization. The magnetic flux generated by the current in the coil 41 may be in both gyratory directions and follows the same circuit 42 as the polarization magnetic flux. The coil 41 then sees an air gap equivalent to the thickness of the magnet 49a. The thickness of this magnet is therefore advantageously reduced to obtain a high efficiency of actuation by the coil 41. the

In the plate 43, all the streams are added. In particular, the flux generated by the magnet 49a is added to that generated by the magnet 49b. The flux generated by a current in the coil is added to or subtracted from this sum of the polarization fluxes.

FIG. 5 presents a configuration similar to that presented in FIG. 4. These two configuration examples differ in the polarization direction of the permanent magnets 59a and 59b in FIG. 5 which are antiparallel. Thus the magnets are arranged in such a way that the polarization fluxes generated by their presence in the magnetic circuits 52 and 58 rotate in opposite directions. The inversion of the flow of the magnet 59b leads to the reversal of the inductions in the air gaps 54c and 54d. This does not change the forces in the gaps. On the other hand, in the plateau, the two polarization inductions are in opposite directions and the total polarization flux is smaller compared to the configuration of FIG.

In a static position, the study of the operation of the two configurations of FIGS. 4 and 5 shows that the forces generated are identical in both cases. The only difference appears in the polarization. With a very simplified model of uniform flux induction calculation, it can be shown that the induction in air gaps c and d is of the order of one tenth of that existing in air gaps a and b. At the level of the forces, the contribution of the gaps c and d is therefore of the order of one hundredth of that of the gaps a and b. At the level of the flux in the plate, the contribution of the magnet b would be of the order of one tenth of that of the magnet a. With this polarization flux, if we want to be able to circulate the flux of the coil without saturating, it is possible to use a slightly thicker plate than for the configuration of Figure 2b since induction of total polarization is stronger.

In dynamic operation, the flux in the plateau created by the polarization always remains in the same direction in the configuration of Figure 4, while it is reversed in the configuration of Figure 5. This means that the currents induced in the tray are larger in the configuration of Figure 5 that in the configuration of Figure 4. For the rest of the magnetic circuit, the dynamic operation remains unchanged.

In FIG. 6, representing a case of parallel polarization. The magnetic circuit 68 in which circulates the magnetic flux generated by the coil 67 of the electromagnet 66 when it is traversed by a current does not include a permanent polarization magnet. It is the same for the magnetic circuit 62 in which circulates the magnetic flux generated by a current in the coil 61. A single magnet has been shown in FIG. 6, but the system functions in the same way with a second magnet as for Figure 8.

In FIG. 7, the magnetic circuit 72 in which the magnetic flux generated by the coil 71 circulates does not include a permanent polarization magnet. It is the same for the magnetic circuit 78 in which circulates the magnetic flux generated by the coil 77 of the electromagnet 76 when it is traversed by a current. The bias magnet 79 generates a flux 72 '. Only one magnet has been shown in Figure 7, but the system works the same way with a second magnet

(In the dotted lines) as in FIG. 9. In the parallel configurations shown in FIGS. 6 and 7, the air gaps seen by the magnetic circuit of the coils remain relatively large, so that the tower amperes lose their efficiency.

Overall, the control device needs a very high efficiency at low air gap. This efficiency is to be considered in terms of performance but also in terms of ability to create significant forces.

The four examples shown in Figures 3 to 7 work well at low airgap (also called closed air gap). The differences in operation are solely at the level of additional parameters such as plateau sections or induced currents.

Parallel configurations with short magnets advantageously allow parallel-type operation with large air gap (that is to say open air gap) and series type with small air gap (that is to say closed air gap). Such configurations, called parallel serial configurations, are described in the following. They are such that the permanent magnet, although placed out of the shortest magnetic circuit for the electromagnet, is traversed by a portion of the magnetic flux generated by the electromagnet so that said flux passes through two closed air gaps.

FIG. 8 and FIG. 9 respectively show two improved configurations of the configurations shown in FIGS. 6 and 7. The permanent magnets implemented are indeed of reduced size so as to allow the flows generated by the coils to pass through them rather than to traverse a large gap, c or d. Figures 8 and 9 have been shown with two magnets, but a single magnet is sufficient to ensure their operation.

In FIG. 8, compared to the configuration of FIG. 6, the circulation of the polarization flux is unchanged. The tray completely closes the magnetic circuit of the magnets. The difference concerns the circulation of the flow created by the coils. If a flow line 82 generated by the coil 81 is followed, it passes through the gap 84a creating the induced field Bba, then the plate 83, then the gap 84b creating the induced field Bba, then the magnet 89b creating the field induced Bb9b, then returns to the coil 81. The flow line "avoids" therefore in part the large gap c. In principle this flux does not pass through the magnet 89a because the reluctance offered by the plate 83 and the two closed air gaps 84a and 84b is practically zero. Thus the flux generated by a current in the coil 81 borrows a magnetic circuit common to the polarization flux of the magnet 89b. As for the coil 87, its flow plays a symmetrical role in passing through the magnet 89a, then the gap 84a, the plate 83, and the air gap 84b. The system can therefore operate with a single coil, 81 or 87, or with both coils fed simultaneously. If the plate is in the middle position, stable position generally obtained through springs, for which the four air gaps are identical, the device can start alone. Indeed, in this case not shown, the four polarization inductions Bpa, Bpb, Bpc and Bpd are identical, but the induction created by the coils 81 or 87 increases the fields in the air gaps 84a and 84b and reduces the fields in the gaps 84c and 84d, triggering the start of the device.

With respect to the configuration of FIG. 8, the configuration of FIG. 9 is such that the circulation of the polarization flux is close. For the circulation of the fluxes of the coils, the situation remains unchanged with the ampere turns of the two coils which are added and which see as gap only the thickness of a single magnet. If we follow a flow line generated by the coil 91, this line passes through the gap 94a creating the induced field Bba, then the plate 93, then the air gap 94b creating the induced field Bbb, then the magnet 99b creating the field induced Bb9b, then returns to the coil 91. The flow line "avoids" therefore in part the large gap d. In principle this flux does not cross the magnet 99a because the reluctance offered by the plate 93 and the two closed air gaps 94a and 94b is practically zero. As a result, it is possible to use only one coil at a time for control of the device. As for the previous device, if the plate is in the middle position, stable position generally given by springs for which the four gaps are identical, the device can start alone for the same reasons as above.

In the two configurations shown in FIGS. 8 and 9, the stream of the coils can pass through a simple small air gap 98 devoid of magnet and crossed by the ampere turns in parallel with the gap which contains the magnets as shown in a dashed circle in Figure 9. This gap is shown in Figure 9, in parallel of the magnet 99a, but similar air gaps can be used in parallel magnets 89a, 89b and 99b. This allows the use of relatively large sections for permanent magnets. In addition, these magnets may not be subject to significant demagnetizing fields, which allows the use of low-end magnets and large section.

In static operation, in the tray for the configurations of FIGS. 8 and 9, the coils can operate separately, each coil controlling one of the two closed positions. In dynamic operation, the polarization flux is reversed in the configuration of FIG. 9 while it remains in the same direction in the configuration of FIG. 8. This can lead to greater induced currents in the configuration of FIG. 9. Given the directions of the flows created by the coils, it is possible to use only one coil which surrounds the two magnetic circuits.

The magnetic circuit of the so-called parallel series configurations of FIGS. 8 and 9 is quite simple, and it allows a great variety of embodiments. For example, the magnetic flux can pass through two air gaps (84a and 84c) closed by the plate when it tilts to a position. This makes it possible to use air gaps seen by the relatively small coils, and thus to make the contribution of the coils more efficient than for series polarizations. It has therefore been shown that it is advantageous to use devices with a small magnet thickness to obtain a series behavior for small air gaps and parallel for large air gaps. the

However, we must pay attention to the use of these thin magnets, which are relatively fragile, and must be protected against shocks.

The set of configurations presented "flat" in Figures 1 and 3 to 9 can be made in 3 dimensions in a similar manner to that presented in perspective in Figure 10. The configuration more precisely presented "folded" in the figure 10 is similar to the configuration shown in FIG. 8. This configuration advantageously operates with a single magnet 109 of large section and relatively thin, and with a single electromagnet 100 including a coil 101, shown in dashed lines. A plate 103 is rotatably mounted about an axis 105 and intended to be placed between two electromagnet branches to form the four air gaps.

There are many possibilities of making variants of the invention. In particular, there are various alternatives for the common or successive feeding of the coils, the geometric structure of the device, etc. Some examples of embodiments have been described, others are briefly described below.

In all of the figures, the plate is located in the middle of the gaps for reasons of simplicity at the level of the variations of the forces on each side of the plate. However, any other position of the plate such as the latter is mounted in rotation about an axis located between the gaps is concerned by the invention.

As regards the parallel series type configurations, the two coils can also be powered simultaneously.

It is also noted that the applications of the invention may be diverse. The invention and its presented embodiments can also be applied in control devices in which the forces are used to stabilize the moving part at the center of the air gap ("Magnetic Bearing"), and also in different industries such as electromagnetically controlled circuit breakers.

Claims

the CLAIMS

1. Device for electromagnetic control of the opening and closing of a mechanical element (17), the positioning of the mechanical element (17) in at least one position (open or closed) being obtained by the action of at least one electromagnet (80) acting on a plate including a magnetic material and controlling the positioning of the mechanical element (17), characterized in that it comprises: - at least one first (84a) and one second (84b) ) gap of variable thickness to be closed by the plate during positioning of the mechanical element (17) in at least one position, the plate being rotated so that the axis of rotation of the plate passes between the first (84a) and second (84b) air gaps, and

at least one permanent magnet (89a, 99a) for polarizing the device so as to maintain the plate in at least one position in the absence of current in the electromagnet, this permanent magnet not being traversed by the magnetic flux main electromagnet.

2. Device according to claim 1, including a third (84c) and a fourth (84d) air gap of variable thickness to be closed by the plate during positioning of the mechanical element (17) in the second position, the axis of rotation of the plate passing between the first, second, third and fourth gaps.

3. Device according to one of claims 1 and 2, wherein the second position of the mechanical element (17) is obtained by the action of a second electromagnet acting on the plate. the the the

4. Device according to one of claims 1 to 3 wherein the magnetic flux generated by electromagnet through a gap (98) devoid of permanent magnet and located in parallel with a gap containing a permanent magnet.

5. Device according to claim 4 wherein the magnetic flux generated by electromagnet passes, in addition to the gap (98) located in parallel with the permanent magnet, the two gaps closed by the plate (84a and 84c) during its tipping into a position.

6. Device according to any one of the preceding claims, wherein the magnetic material included in the plate is a ferromagnetic material.

7. Device according to any one of the preceding claims, wherein the electromagnet (80) consists of a coil (81) and a magnetic circuit (82) including a magnetic core around which the coil and four arms is wound. whose four ends each constitute one face of an air gap, the other face of the gap being on the plate.

8. Device according to any one of the preceding claims, wherein the mechanical element (17) is a valve.

9. Device according to any one of claims 1 to 7, wherein the mechanical element (17) is an electromagnetically controlled circuit breaker.