EP1421590B1 - Electromagnetic actuator with two stable end-of-travel positions, in particular for controlling air intake duct valves for internal combustion engines - Google Patents

Description

The invention relates to an electromagnetic actuator comprising a stator structure consisting of two ferromagnetic circuits provided with at least one electrical excitation coil and between which is mounted movably, between two stable end-of-travel positions and against the action of resilient return, an armature of soft ferromagnetic material connected to a load to be controlled, the armature and the stator structure being symmetrical with respect to the axis of rotation of the armature.

The present invention will find application in the field of electromagnetic actuators more particularly intended to bring a load, simply, from a first in a second position and vice versa.

In many fields of application is the problem of bringing a load, very often in the form of a flap or valve, in two stable end positions, one opening and one closing. This is particularly the case in the case of an internal combustion engine having a combustion air intake pipe which, under certain conditions, must be closed to prevent the arrival of air at the engine or, on the contrary, completely open to allow the free passage of the air flow.

In fact, this management of the combustion air inlet is generally effected through the control of the intake valves that comprises such an engine and it is known, for these particular applications, solenoid electromagnetic actuators or pallet. These solutions, however, remain very complex and have a direct implication on the constituent elements of such an internal combustion engine.

If there are, moreover, electromagnetic actuators of rotary type for these same applications, they are considered, in most cases, as particularly bulky and / or complex with respect to the function they are asked ensure. In addition, they cause parasitic forces at the controlled load.

He is still known, by the document US A.6.262.498 an electromagnetic actuator comprising two electromagnets arranged in opposition to one another and between which is able to move an armature of ferromagnetic material held in an intermediate position by means of resilient return means, more particularly in the form of a torsion spring. Thus, depending on the electromagnet that is powered, the armature is pulled in one or other of its stable end positions against the action of these elastic return means. To this frame is connected a transmission rod located in the axial extension of a valve of an internal combustion engine, valve which is secured.

To return to the electromagnets, these comprise a substantially U-shaped ferromagnetic circuit on which is mounted an electric excitation coil, this circuit defining two stator poles against which it is capable of being applied by electromagnetic bonding. frame.

He is also known, by the document WO 97/15061 , an electromagnetic actuator comprising a stator structure consisting of two ferromagnetic circuits each provided with two electrical excitation coils surrounding a stator pole disposed symmetrically on either side of a central pole. In this regard, the central poles of each of these ferromagnetic circuits of the stator structure ensures the maintenance of rotation of the axis of a movable armature connected to a load to be controlled.

WO 27/15061 describes the preamble of claim 1.

Also, in the context of this stator structure, as described in this prior document, the magnetic induction flux flows through the axis of the armature, so that; when controlling the actuator, a single pole of each ferromagnetic circuit contributes to the force of appeal of the armature.

If, thanks to this structure, a substantial torque is generated over the entire angular travel of the element due to the presence of only two main gaps at the two active poles, such an actuator is unable to offer optimal performance for bonding the frame.

In the end, in this prior document a solution is described to obtain a rapid displacement of the armature under the influence of the single magnetic circuit, so that it has been sought the production of a substantial torque over the entire race of this frame.

In the context of a first inventive step, it has been imagined to entrust the displacement control function due to the moving armature, from a stable position to another, to elastic return means and not, essentially, to the torque pair. recall that produces the electromagnetic force, so that it is no longer necessary for the latter to ensure a significant torque over the entire stroke of the movable member. Then, in a second inventive step, it was imagined that the maximum torque produced by the electromagnetic force intervenes in bonding position to, this time, overcome the elastic restoring forces and ensure the perfect maintenance of the armature in the any of its end positions.

It has been found that the control in displacement of the armature under the impulsion of one or the other electromagnet, generates parasitic forces on this armature and in particular of radial forces which deteriorate the efficiency of this actuator, in that they do not optimize the torque / driving ratio ratio.

For this purpose, the invention relates to an electromagnetic actuator comprising a stator structure consisting of two ferromagnetic circuits provided with at least one electrical excitation coil and between which is mounted movably, between two stable end-of-travel positions, a reinforcement soft ferromagnetic material connected to a load to be controlled, the armature and the stator structure being symmetrical with respect to the axis of rotation of the armature, characterized in that each ferromagnetic circuit comprises four stator poles with which two two the frame in one or other of its stable end positions and the frame is mounted movably against the action of elastic return means.

According to an advantageous embodiment, the elastic return means are designed capable of acting on the axis of rotation of the armature.

Very particularly and according to a first embodiment, the elastic return means are defined by a spiral spring acting on the axis of rotation of the armature and mounted in a plane parallel to the stator structure.

According to a second embodiment, said elastic return means are defined by a torsion bar.

In fact, if a spiral spring significantly increases the moving mass of the actuator, so its inertia and, therefore, the travel time for the armature to move from one to the other of its stable positions of end of stroke, the use of a torsion bar only may have the disadvantage of making the actuator particularly cumbersome because of the length of this bar. Also and advantageously, these means of resilient return consist of a combination of the two previous solutions, namely a spiral spring and a torsion bar, each being determined with adequate stiffness.

The advantages that flow from the present invention consist in that, through the symmetry of the stator structure, an equilibrium of parasitic forces results in the control of the actuator, besides the fact that such a configuration makes it possible to optimize the ratio torque / driving inertia. Furthermore, this design, in combination with suitable resilient return means, leads to a compact actuator, thus reduced size for better integration in the environment where the load to be controlled. Another advantage resulting from the suppression of the radial forces consists of increased durability of the different parts making up this actuator.

Other objects and advantages of the present invention will become apparent from the following description relating to embodiments given as indicative and non-limiting examples.

• la figure 1 est une représentation schématisée et vue en plan d'un actionneur électromagnétique conforme à l'invention ;
• la figure 2 est une représentation similaire à la figure 1 illustrant ce même actionneur équipé de moyens de rappel élastiques sous forme d'un ressort spiral ;
• la figure 3 est une représentation schématisée et en perspective de ce ressort en spirale ;
• la figure 4 est une représentation schématisée et en coupe d'un actionneur conforme à l'invention comportant, en tant que moyens de rappels élastiques, à la fois, un ressort spiral et une barre de torsion ;
• la figure 5 est une représentation schématisée et en plan de l'actionneur dépourvu de sa structure support ;
• la figure 6 est une représentation schématisée et en plan d'un actionneur conforme à un second mode de réalisation ;
• la figure 7 est une représentation schématisée et en élévation d'un actionneur électromagnétique conforme à l'invention auquel est associé un capteur de position de l'armature ;
• les figures 8 et 9 illustrent, de manière schématisée, deux types de clapets de vanne prévus aptes à être commandés au travers d'un actionneur électromagnétique, conforme à l'invention.

The understanding of this description will be facilitated by reference to the accompanying drawings in which:

• the figure 1 is a schematic and plan view of an electromagnetic actuator according to the invention;
• the figure 2 is a representation similar to the figure 1 illustrating this same actuator equipped with elastic return means in the form of a spiral spring;
• the figure 3 is a schematic and perspective representation of this spiral spring;
• the figure 4 is a schematic representation in section of an actuator according to the invention comprising, as means of elastic recalls, both a spiral spring and a torsion bar;
• the figure 5 is a schematic representation in plan of the actuator devoid of its support structure;
• the figure 6 is a schematic representation in plan of an actuator according to a second embodiment;
• the figure 7 is a schematic representation in elevation of an electromagnetic actuator according to the invention which is associated with a position sensor of the armature;
• the Figures 8 and 9 schematically illustrate two types of valve valves provided adapted to be controlled through an electromagnetic actuator according to the invention.

The present invention relates to an electromagnetic actuator 1 as illustrated in the Figures 1 to 7 .

More particularly, this actuator 1 comprises a stator structure 2 consisting of two ferromagnetic circuits 3, 4, each comprising at least one electrical excitation coil 5, 5A; 6, 6A.

Between these two ferromagnetic circuits, arranged opposite one another, is mounted a frame 7 of soft ferromagnetic material. This is caused to move between two stable end-of-travel positions 8, 9, under the impulse of the magnetic fluxes generated through one and / or the other of the ferromagnetic circuits 3, 4.

In the end, this armature 7 moves in this position 8 or 9 against the action of resilient biasing means 10 having a tendency, in the absence of magnetic flux, to maintain it in an intermediate position, between these positions of ends. race 8, 9.

The armature 7 is rotated about an axis 12 corresponding to its axis of symmetry, knowing, moreover, that the stator structure 2 and, in particular, the ferromagnetic circuits 3, 4 adopt, themselves, a provision symmetrical with respect to this axis 12.

Thus, each of these ferromagnetic circuits 3; 4 have four stator poles P1, P2, P3, P4; P'1, P'2, P'3, P'4 with which is cooperated two by two (P1, P2, P'3, P'4, P'1, P'2, P3, P4) the frame 7 in one or other of its stable end positions 8, 9.

In sum, each ferromagnetic circuit 3, 4 is moreover symmetrical with respect to a median plane 13 passing through the axis 12.

More particularly and according to the embodiment corresponding to Figures 1, 2 and 5 a ferromagnetic circuit 3, 4 has a W-shaped configuration, the two lateral branches 14, 15 defining the stator poles of ends P1, P4; P'1, P'4 each carry an electrical excitation coil 5, 5A; 6, 6A. While the middle branch 16 of this W structure, it defines the two central stator poles P2, P3; P'2, P'3 respecting, between them, an angle α at least equal to the amplitude of rotation of the armature 7, plus 180 °. Finally, this angle α is the one respected by the two planes in which the stator poles are inscribed respectively, P1, P2; P'1, P'2 and P3, P4; P'3, P'4 of these ferromagnetic circuits 3, 4.

It will be noted that, for better circulation of the magnetic fluxes and in particular to prevent this flow from closing up through the axis of rotation 12 of the armature 7, the median branch 16 adopts a V-shaped structure and consequently, it subdivides itself into two branches 16 ', 16 "for the definition of the poles P2, P3; P'2, P'3.

As for the armature 7, in the form of a blade, it comprises, at its axis of rotation 12, a cylindrical blister 17 in the manner of a sleeve for the passage of an axis 18, which may or may not be a ferromagnetic material, the ends 19, 20 are maintained in rotation through a support structure 21, preferably non-magnetic. This is, more particularly, visible in the figures 4 and 7 .

On this structure 21 are still fixed the ferromagnetic circuits 3, 4 via appropriate means.

The elastic return means 10 are constituted, according to a first embodiment visible in the Figures 2, 4 and 7 by at least one spiral spring 22, 22 'mounted on at least one of the ends 19, 20 of the axis 18 corresponding to the armature 7.

So, as visible in the figure 3 , this spiral spring 22, 22 'can be provided with one or more arms in the form of a turn, this according to the desired stiffness and / or the available space, so the section of this spring 22, 22'.

According to a second embodiment, illustrated in the figure 4 , the elastic return means 10 consist of a torsion bar 30 which is secured to the axis 18 corresponding to the armature 7. This axis 18 is preferably of tubular type, the torsion bar 30 being fixed, by the one of its ends 31, at the end 19 of this axis 18. Moreover, it extends through the latter to emerge at the end 20 opposite thereof to come rigidly into a housing 32 of the support structure 21 of the actuator.

As it is still visible in this figure 4 , the elastic return means 10 may correspond to the combination of at least one spiral spring 22 and a torsion bar 30 whose stiffness is chosen in line with the restoring force to be produced. This spiral spring 22 and this torsion bar 30 both act, either in parallel or in series on the axis 18 of the frame 7. Such a design makes it possible to compensate for the disadvantages of one by the advantages of the other. In particular, a spiral spring has the disadvantage of increasing the moving mass of the actuator, while the use of a torsion bar alone can have the inconvenient effect a significant increase in its size.

The figure 7 is intended to illustrate that on one of the ends 19 of the axis of rotation 18 corresponding to the frame 7 may be mounted a position sensor 23, preferably a non-contact sensor hall effect or the type of potentiometer or other, to know the position of this armature 7 at any time, to control, via an electronic control control unit 24, the engagement of the current in the coils and minimize the impact speed at the end of the race. this frame 7.

To this provos, if we return to the embodiment corresponding to the figures 1 2 and 5 , the coils 5 and 6A, as well as 5A and 6, ferromagnetic circuits 3 and 4 are connected in series or in parallel, allowing when the bonding of the frame 7 is performed, that is to say when this frame 7 is called in one or other of its end-of-travel positions 8, 9, to symmetrize the radial forces applied on the axis of rotation 18. Thus, the balance of forces applied to this axis is zero.

Moreover, it will be noted that this axis of rotation 18 corresponding to the armature 7 is held at its ends 19, 20 by bearings or, ideally, by ball or needle bearings that comprise the support structure 21 to limit the friction. In this respect, thanks to the suppression of the radial forces on the axis of rotation 18, as mentioned above, this results in increased durability of these bearings or bearings.

To return to the power supply of the electric excitation coils in the embodiment corresponding to these Figures 1, 2 and 5 and starting from the intermediate position 11 occupied by the armature 7 of the actuator 1 at rest, the alternating activation of the two sets of coils 5, 6A and 5A, 6, respectively, makes it possible, in a first step, to bring the frame 7 made of a ferromagnetic material when bonded to the stator poles P1, P2, P'3, P'4;P'1,P'2, P3, P4 in an end position 8, 9 predetermined by the selected electrical control. It should be noted that the alternative activation of the coils according to the resonance mode of the system makes it possible to perform this operation in a time dependent on the current used.

In a second step, this alternative activation of the two sets of coils 5, 6A; 5A, 6 allows the passage from one end position to another.

It should be noted that in these end-of-travel positions 8, 9 the reinforcement 7 does not necessarily come to the physical bonding on the stator poles, as the case may be, P1, P2, P'3, P'4 or P ' 1, P'2, P3, P4, especially in the presence of external mechanical stops. These stops may correspond, for example, to the arrival at the end of the mechanical stroke of the controlled load. By thus avoiding the impacts of the armature 7 on these stator poles, the wear of the electromagnetic actuator 1 is limited, and the noise resulting from such impacts is avoided. In addition damping means can be associated with the load itself to limit the noise resulting from mechanical stops.

If we go back, now, to the figure 6 , there is shown a second embodiment of an electromagnetic actuator 1 according to the invention. In fact, it differs from the embodiment described above in that the ferromagnetic circuits 3, 4, while being arranged symmetrically about the axis of rotation 12 of the frame 7 and while having, moreover, a symmetry with respect to a transverse median plane passing through this axis 12, each comprises only one electric excitation coil 5, 6. This is mounted on the middle branch 16 of these ferromagnetic circuits 3, 4 in the shape of W.

However, it will be observed that in this particular case this median branch 16 terminates in a point through two inclined planes corresponding to the central poles P2, P3; P'2, P'3 and respecting between them an angle α at least equal to the rotation amplitude of the armature 7, plus 180 °. Under these conditions and to ensure proper circulation of the magnetic flux through the frame 7, it is mounted on an axis 18 of ferromagnetic material. For example, on either side of the blade, defining this armature 7, can extend axis sections kept rotated through the support structure 21 of non-magnetic material of the actuator 1.

However, it will be noted that this median branch 16 of these ferromagnetic circuits 3, 4 can end, again, in V and be subdivided into two branches 16 ', 16 "for the definition of the poles P2, P3; P'2 , P'3.

Specifically, when the electromagnetic actuator has only two coils, they are connected in series or in parallel and their activation according to the position of the armature 7 allows the passage of a stable end position to a another according to the electrical control envisaged. Note, however, that in an intermediate position of the frame 7 no magnetic circuit is preferred so that the frame 7 can not be driven. Also and according to the invention, a dissymmetry is introduced at the level of the resulting actuator, according to a first example of embodiment, of an asymmetrical shape of the armature 7 or else by an adapted preload of the spring or springs defining the elastic return means 10 so that this armature 7, in the rest position of these elastic return means 10 and in the absence of supply of the coils 5, 6, occupy an intermediate equilibrium position 11 which is asymmetrical by relative to the median plane 25 of the stator structure of this electromagnetic actuator 1.

The Figures 8 and 9 illustrate diagrammatically two types of valves or flaps 26, 26A corresponding to charges that can be controlled by the electromagnetic actuator 1 according to the invention. In fact, it will find a particular application for controlling the opening and closing of the valve of a valve, such as a valve for combustion air intake duct in an internal combustion engine. So, the figure 7 shows a first variant having an axis of rotation 27 of the valve 26 which is offset relative to its plane. This has the effect of substantially increasing the inertia of the load to be actuated with respect to any other valve, in particular of the butterfly type corresponding to the figure 8 whose axis of rotation 28 lies in the plane of the valve 26A.

Claims (19)

1. Electromagnetic actuator, including a stator structure (2) comprised of two ferromagnetic circuits (3, 4) provided with at least one electrical excitation coil (5, 5A, 6, 6A) and between which an armature (7) made of soft ferromagnetic material connected to a load to be controlled is mounted movably between two stable end positions (8, 9), the armature (7) and the stator structure (2) being symmetrical with respect to the axis (12) of rotation of the armature (7), wherein each ferromagnetic circuit (3, 4) includes four stator poles (P1, P2, P3, P4 ; P'1, P'2, P'3, P'4), which the armature (7) in either one of its stable end positions (8, 9) cooperates with two by two (P1, P2, P'3, P'4 ; P'1, P'2, P3, P4), and the armature (7) is mounted movable against the action of springy restoring means (10).
2. Electromagnetic actuator according to claim 1, wherein a ferromagnetic circuit (3, 4) is symmetrical with respect to a median plane (13) passing through the axis of symmetry (12).
3. Electromagnetic actuator according to any one of the preceding claims, wherein the stator poles (P1, P2 ; P'1, P'2), on the one hand, and the stator poles (P3, P4 ; P '3, P'4), on the other, are inscribed, for each ferromagnetic circuit (3, 4), in planes forming between them an angle (α) at least equal to the amplitude of rotation of the armature (7), plus 180°.
4. Electromagnetic actuator according to any one of the preceding claims, wherein a ferromagnetic circuit (3, 4) adopts a W-shaped configuration, the two lateral legs (14, 15) of which defining end stator poles (P1, P4 ; P'1, P'4) each carry an electric excitation coil (5, 5A ; 6, 6A), while the median leg (16) defines two central stator poles (P2, P3 ; P'2, P'3).
5. Electromagnetic actuator according to claim 4, wherein the median leg (16) adopts a V-shaped structure and is subdivided into two legs (16', 16") for defining the central stator poles (P2, P3, P'2, P'3).
6. Electromagnetic actuator according to any one of claims 3 to 5, wherein the electrical excitation coils (5, 6) as well as (5A and 6A) of the ferromagnetic circuits (3, 4) are connected in series or in parallel in order to symmetrize the radial forces applied on the axis of rotation of the armature (7) when the latter is brought into either of these end positions (8, 9).
7. Electromagnetic actuator according to any one of claims 1 to 3, wherein a ferromagnetic circuit (3, 4) adopts a W-shaped configuration including two lateral legs (14, 15) and a median leg (16), the latter carrying an electric excitation coil (5, 6).
8. Electromagnetic actuator according to claim 7, wherein the median leg (16) tapers through two inclined planes corresponding to the central poles (P2, P3 ; P'2, P'3) and forming between them an angle at least equal to the amplitude of rotation of the armature 7, plus 180°.
9. Electromagnetic actuator according to claim 7, wherein the median leg (16) adopts a V-shaped structure and is subdivided into two legs (16', 16") for defining the central stator poles (P₂, P₃, P'2, P'3).
10. Electromagnetic actuator according to any one of claims 7 to 9, wherein the electrical excitation coils (5, 6) of the ferromagnetic circuit (3, 4) are connected in series or in parallel.
11. Electromagnetic actuator according to any one of claims 7 to 10, wherein the armature (7) has a dissymmetrical shape with respect to its axis of rotation (12) or the springy restoring means (10) have a pre-stress adapted for providing said frame (7) an intermediate balance position (11), in resting position of these springy restoring means (10) and in the absence of current supply to the coils (5, 6), which is dissymmetrical with respect to the median plane (25) of the stator structure (2).
12. Electromagnetic actuator according to any one of the preceding claims, wherein the armature (7) is in the form of a blade rotatably mounted on an axis (8) of ferromagnetic or non-ferromagnetic material, the ends (19, 20) of which are held in rotation through a support structure (21) to which the ferromagnetic circuits (3, 4) are also fixed through adequate means.
13. Electromagnetic actuator according to any one of the preceding claims, wherein the springy restoring means (10) are designed capable of acting on the axis of rotation (18) of the armature (7).
14. Electromagnetic actuator according to any one of the preceding claims, wherein the springy restoring means (10) are formed of at least one spiral spring (22, 22') mounted on at least one end (19, 20) of the axis (18) corresponding to the armature (7).
15. Electromagnetic actuator according to any one of the preceding claims, wherein the springy restoring means (10) are formed of a torsion bar (30), which the axis (18) corresponding to the armature (7) is made integral with.
16. Electromagnetic actuator according to claim 13, wherein the springy restoring means (10) are formed of the combination of at least one spiral spring (22) and one torsion bar (30) acting, either in parallel or in series, on the armature (7).
17. Electromagnetic actuator according to claim 15, wherein the axis (18) of the armature (7) is of a tubular type, the torsion bar (30) being fastened by one of its end (31) to one end (19) of said axis (18), and extends through the latter in order to protrude at the opposite end (20) thereof and to be anchored rigidly in a recess (32) of the support structure (21) of the actuator.
18. Electromagnetic actuator according to any one of the preceding claims, wherein on one end (19) of the axis of rotation (18) corresponding to the armature (7) is mounted a position sensor (23), more particularly a contactless sensor with Hall effect or similar, in order to control, through an electronic control unit (24), the switching-on of the current in the coils (5, 5A, 6, 6A) and to minimize the speed of impact at the travel end of the armature (7).
19. Application of the electromagnetic actuator according to any of the preceding claims, to the control of a throttle valve of the combustion-air intake conduit of an internal combustion engine.

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