EP0736882A1 - Control device for electromagnet with core without friction and application for valves with continuous control - Google Patents

Abstract

The electromagnetic transducer drives an inner hub (4) laterally. The hub has a rear chamfer with shoulders on the armature channel holding it in place in the rest position. The armature (2) has electrical winding mounted coaxially around the hub centre. The hub is attached to a front and rear flexible section (14,15) covering the front and rear of the armature. The magnetic field moves the hub forward, displacing the flexible section.

Description

The present invention relates to control devices of the electromechanical transducer type, in which an electromagnet transforms an electrical control signal into a displacement or a force applied to a sliding core.

Such control devices with a sliding core electromagnet are known, such as those described in the documents US-A-4,954,799, FR-A-1,053,825, US-A-4,463,332. In such a device, the electromagnet comprises a fixed armature, integral with the frame of the device in which the electromagnet is inserted. The armature, made of material sensitive to the magnetic field, comprises an axial channel in which axially slides a generally cylindrical core made of material sensitive to the magnetic field. The core slides in a first magnetic pole with a radial air gap, the second pole closing the axial channel and defining with the core a variable axial air gap. An electrical coil, connectable to an external source of electrical energy, generates in the armature, and in particular in the axial channel between the two poles of the armature, a magnetic field tending to drive the core in axial sliding in the channel axial along the longitudinal axis.

In its sliding, the core is guided by two elements with flexible radial blades comprising a peripheral part fixedly mounted on the fixed frame and connected by said flexible radial blades to a central part integral with the sliding core, to keep the core apart walls of the axial channel while allowing its axial displacement in an appropriate stroke between a first and a second extreme axial positions. In these previous documents, by the fact that the second pole closes the axial channel, the two elements with flexible radial blades are arranged on the same side of the axial channel, or inside the axial channel. This results in a relatively complex construction, as well as a relatively small stroke of the sliding core between the extreme axial positions.

The problem proposed by the present invention is to design a new structure of control devices with electromagnet and sliding core, which is of simpler construction, which allows a greater axial stroke of the sliding core between its axial positions extremes, in order to better control the forces and strokes for better progressiveness of the control device as a function of the electric current flowing through the electric winding.

• une armature fixe, munie d'un bobinage électrique et d'un canal axial, générant dans ledit canal axial, entre un premier pôle et un second pôle, un champ magnétique lors du passage d'un courant électrique dans son bobinage,
• un noyau mobile sensible au champ magnétique, entraîné en coulissement axial dans ledit canal axial par ledit champ magnétique et guidé par au moins deux éléments à lames radiales flexibles comportant une partie périphérique montée fixe par rapport à l'armature fixe et reliée par lesdites lames radiales flexibles à une partie centrale solidaire du noyau coulissant, pour maintenir le noyau à l'écart des parois du canal axial tout en autorisant son déplacement axial selon une course appropriée entre une première et une seconde positions axiales extrêmes ; en outre :
• le canal axial traverse de part en part le bobinage électrique,
• les éléments à lames radiales flexibles sont disposés respectivement de part et d'autre des extrémités du canal axial.

To achieve these and other objects, a sliding-core electromagnet control device according to the invention comprises:

• a fixed armature, provided with an electric coil and an axial channel, generating in said axial channel, between a first pole and a second pole, a magnetic field during the passage of an electric current in its coil,
• a movable core sensitive to the magnetic field, driven in axial sliding in said axial channel by said magnetic field and guided by at least two elements with flexible radial blades comprising a peripheral part mounted fixed relative to the fixed frame and connected by said radial blades flexible to a central part integral with the sliding core, to keep the core away from the walls of the axial channel while allowing its axial displacement according to an appropriate stroke between a first and a second extreme axial positions; in addition :
• the axial channel runs right through the electrical winding,
• the elements with flexible radial blades are disposed respectively on either side of the ends of the axial channel.

Preferably, the axial guide means comprise two elements with flexible blades offset axially on the core, to the exclusion of any guide sliding in the axial channel.

Preferably, the flexible blades have, in the first extreme axial position in the absence of a magnetic field produced by the fixed armature, a permanent deformation in bending in the direction of the axial displacement of the core in a first direction, the magnetic field causing the displacement of the core in the opposite direction to said first direction.

According to an advantageous embodiment, in the second extreme axial position, the flexible blades of at least one of the elements with flexible blades are substantially flat. This arrangement makes it possible to ensure better radial rigidity, to guarantee a more effective retention of the core in the position in which the magnetic field is maximum, preventing the magnetic forces from pressing the core radially against one of the magnetic poles.

According to a first application, the core carries a movable closure element housed in the opening of a fixed seat of a duct fluid conduction to modify the open section of said fluid conduction conduit as a function of the axial position of the closure element in said seat. An electrically operated valve is thus produced.

• la figure 1 illustre, en vue de côté en coupe longitudinale, une structure de dispositif de commande à électroaimant selon un mode de réalisation de la présente invention, en première position axiale extrême;
• la figure 2 illustre, en vue de côté en coupe longitudinale, le dispositif de la figure 1 en seconde position axiale extrême ;
• la figure 3 illustre, en vue de côté, le dispositif des figures 1 et 2 associé à un élément d'obturation ;
• les figures 4 à 6 illustrent trois modes de réalisation des éléments à lames radiales élastiquement flexibles selon l'invention ;
• la figure 7 illustre, en vue de côté en coupe longitudinale, un dispositif de commande selon un second mode de réalisation de la présente invention, en première position axiale extrême ;
• la figure 8 illustre, en vue de côté en coupe longitudinale, le dispositif de la figure 7 en seconde position axiale extrême ; et
• la figure 9 illustre, en vue de face, un autre mode de réalisation de l'élément à lames radiales élastiquement flexibles selon l'invention.

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

• FIG. 1 illustrates, in side view in longitudinal section, a structure of an electromagnet control device according to an embodiment of the present invention, in the first extreme axial position;
• Figure 2 illustrates, in side view in longitudinal section, the device of Figure 1 in second extreme axial position;
• Figure 3 illustrates, in side view, the device of Figures 1 and 2 associated with a closure element;
• Figures 4 to 6 illustrate three embodiments of the elements with elastically flexible radial blades according to the invention;
• FIG. 7 illustrates, in side view in longitudinal section, a control device according to a second embodiment of the present invention, in the first extreme axial position;
• Figure 8 illustrates, in side view in longitudinal section, the device of Figure 7 in second extreme axial position; and
• FIG. 9 illustrates, in front view, another embodiment of the element with elastically flexible radial blades according to the invention.

In the embodiments illustrated in FIGS. 1 to 3, 7 and 8, a control device with an electromagnet and a sliding core according to the invention comprises a fixed armature 1, provided with an electric coil 7 and an axial channel 3 which runs right through the electrical winding 7. The fixed frame 1 is integral with the frame 2 of the device in which it is arranged. A core 4 is slidably mounted in the axial channel 3.

The frame 1, made of a material sensitive to the magnetic field, is formed of a peripheral stirrup 9 the ends of which are folded radially inwards to form end flanges 10 and 11 each connecting to a first coaxial tubular element 5 and a second coaxial tubular element 6, respectively forming a first pole 5 and a second pole 6 of the armature 1. The frame 1 may consist of one or more assembled parts, comprising for example two opposite side members forming a double stirrup 9 while being connected by the end flanges 10 and 11. The poles 5 and 6 are shaped so that their respective inner faces 12 and 13 are opposite the core 4 and separated from the latter by a generally radial air gap of small thickness.

The winding 7 is adapted so that, when an electric current flows through it, it produces a magnetic field in the axial channel 3 between the poles 5 and 6. Under the action of the magnetic field, the core 4 tends to move axially sliding in the axial channel 3 in the direction producing the reduction of the air gaps. For this, the core 4 is made of a material sensitive to the magnetic field, and it is guided in sliding in the axial channel 3 by guide means capable of allowing its sliding without introducing friction opposing this sliding.

The guide means according to the invention comprise a first element 14 with flexible radial blades, and a second element 15 with flexible radial blades, arranged respectively on either side of the ends of the axial channel 3, at a sufficient distance from the armature 1 to allow the free bending of the flexible radial blades during the axial sliding of the core 4.

Each element with flexible radial blades such as the element 14 comprises a peripheral part 16 mounted fixed relative to the fixed frame 1, that is to say integral with either the fixed frame 1 or directly from the frame 2 of the 'apparatus. The element 14 with flexible radial blades has a central part 17 integral with the sliding core 4. The peripheral part 16 is connected to the central part 17 by flexible radial blades 18.

The flexible radial blades 18 are arranged to have great flexibility in the direction of axial sliding of the core as represented by arrow 19, and to simultaneously exhibit great rigidity in the direction of the radial movements of the core 4, so as to maintain the core 4 away from the walls of the axial channel 3, and in particular from the poles 5 and 6, while allowing its axial displacement along the axis II according to an appropriate stroke. The flexibility of the blades 18 is chosen so that the appropriate stroke can be suitable for a possible displacement of the core 4 between two extreme axial control positions illustrated respectively in FIGS. 1 or 7 and 2 or 8.

Thus, in the embodiments shown, the core 4 is held by the two elements 14 and 15 with flexible blades offset axially on the core 4, to the exclusion of any sliding guide in the axial channel 3.

Other embodiments are however possible, by providing that the core is further guided by one or more sliding bearings.

One can imagine many possible forms for the elements 14 and 15 with flexible blades.

To ensure an equal distribution of the resistance to radial bending, thus ensuring good retention of the core in alignment with the longitudinal axis II of the frame 1, at least three flexible blades are regularly provided at the periphery of the central part 17 of element 14. The flexible blades 18 are flat blades, widened in the transverse plane, and of reduced thickness in the axial direction of the core 4.

Various forms can be given to the flexible blades 18, making it possible in particular to lengthen their length to increase the possibilities of bending allowing axial sliding of the core 4.

For example, in the embodiments of Figures 4 and 9, the flexible blades comprise three blades, respectively 180, 181 and 182, having a general shape in a spiral around the longitudinal axis of the core.

In the embodiment of FIG. 5, the flexible blades comprise three blades 180, 181 and 182 each comprising at least one portion 184 substantially in an arc of circle centered on the longitudinal axis of the core, and one or more generally radial portions of connection: in the example shown, the blade 180 comprises two portions in an arc 184 and 185, connecting respectively to the peripheral ring 16 by a generally radial connection portion 186, and to the central ring 17 by a generally radial portion 187 of connection, and connecting to each other by a third generally radial portion 188 of connection.

In the embodiment illustrated in FIG. 6, each of the three flexible blades such as the blade 180 also comprises two portions in an arc of a circle, 184 and 185 respectively, connecting one to the other by the generally radial portion 188, and connecting respectively to the peripheral ring 16 by the generally radial portion 186 and to the central ring 17 by the generally radial portion 187.

Preferably, the respective flexible blades 18 of the elements 14 and 15 with flexible blades are wound in the same direction around the longitudinal axis I-I of the device. Thus, during the axial movement of the core 4, the flexible blades of the elements 14 and 15 impart to the core 4, simultaneously with its axial translation, a slight rotation around the longitudinal axis I-I, promoting a harmonious deformation of the flexible blades 18.

It is understood that the elements with flexible blades such as the element 14 can be made from a flat disc of steel or other material, from which are cut openings to form the flexible blades as shown.

Thanks to their position outside the axial channel 3, the elements 14 and 15 with flexible radial blades 18 can advantageously have a diameter significantly greater than that of the axial channel 3. For example, as illustrated in the figures, the peripheral ring 16 elements 14 and 15 can be fixed directly to the frame 2, thus having a diameter at least equal to the outside diameter of the frame 1. This thus favors the possibilities of bending of the flexible blades, in order to increase the admissible axial travel of the core 4.

Figures 1 and 7 illustrate a device according to the invention in a first extreme axial position. Preferably, in this first position, in the absence of a magnetic field produced by the fixed armature 1, the flexible blades 18 have a permanent bending deformation in the direction II of axial displacement of the core 4 in a first direction 20. In this position, the core 4 is relatively far from the second pole 6 of the frame 1.

According to a first possibility, illustrated by FIG. 1, the permanent bending deformation of the flexible blades 18 in the first extreme axial position can result from a preforming of the flexible blades 18.

According to a second possibility, illustrated by FIGS. 3, 7 and 8, the permanent bending deformation of the flexible blades 18 in the first extreme axial position may result from the thrust of an axial spring 31 urging the core 4 towards its first extreme axial position.

Under the action of a magnetic field created by the passage of an electric current in the winding 7, the core 4 moves axially in the direction 19 opposite to said first direction 20 until in a second extreme axial position as illustrated on Figures 2 and 8, position in which the core 4 has approached the second pole 6 of the frame 1. During this movement, the elements 14 and 15 with flexible blades are deformed as illustrated in Figure 2, by bending flexible blades 18 of each element. It is noted that, between the two extreme positions illustrated in FIGS. 1 or 7 and 2 or 8, the core 4 can move while remaining permanently away from the poles 5 and 6 of the armature 1, so that 'No friction disturbs the axial movement of the core 4.

Preferably, as illustrated in FIG. 8, in the second extreme axial position, the flexible blades 18 of at least one of the elements 14 and 15 with flexible blades, are substantially flat, that is to say in a plane generally perpendicular to axis II of the device. In Figure 2, the two elements 14 and 15 are substantially flat. This improves the radial rigidity of the blades in this second extreme axial position where the core undergoes maximum mechanical stress under the effect of the maximum magnetic field generated by the coil 7.

In the embodiment illustrated in Figures 1 to 3, the first end of the core 4 is cylindrical, and slides in the first pole 5 whose respective inner surface 12 is cylindrical. Thus, the first pole 5 defines with the core 4 a first constant radial air gap, independent of the axial position of the core 4 in the axial channel 3.

In this same embodiment, the second end of the core 4 is shaped as a cone 22, to cooperate with a corresponding conical part 23 of the second pole 6 in which it engages. The second pole 6 thus defines with the core 4 a second radial air gap which decreases as a function of the axial displacement of the core 4 from the first to the second extreme axial position. The axial displacement of the core 4 progressively modifies the air gap 21 between the cone 22 of the core 4 and the conical part 23 of the pole 6. It is thus possible to produce a progressive movement of the core in the presence of the magnetic field generated by the coil 7.

In the embodiment of Figures 7 and 8, the first pole 5 also has a cylindrical interior surface defining a first constant air gap, as in the previous embodiments. On the other hand, the second pole 6 has a cylindrical interior surface, and cooperates with a portion of core 4 of variable diameter, defining a second variable radial air gap.

Another alternative may consist in the presence of two poles 5 and 6 with cylindrical interior surfaces opposite cylindrical parts of core 4, defining two constant radial air gaps independent of the axial position of core 4.

The control device according to the invention can be associated with shutter means, to constitute a continuously electrically controlled valve. For this, the core 4 carries or constitutes by itself a closure element making it possible to modify the open section of a fluid conduction channel as a function of the axial position of the core 4 in the frame 1.

Thus, FIG. 3 represents an embodiment of such a continuously electrically controlled valve, comprising an electromagnet control device identical to that of FIGS. 1 and 2, in which the same elements have been identified by the same reference numerals . The same is true of FIGS. 7 and 8, which show another embodiment of such a continuously electrically controlled valve. The core 4 carries a shutter element 24 coaxial of revolution which is received in the opening 25 of a seat 26 coaxial with a fluid conduction conduit.

The closure element 24 advantageously has a shape of revolution tapering progressively towards its end 27, so that the closure element 24 produces a continuous variation of the open section of the fluid conduction conduit as a function of the position axial of the core 4 and of the closure element 24 in the seat 26.

An elastomer seal 28 can be interposed between a front facet 29 of the seat 26 and a front facet 30 of the closure element 24, to ensure a sealed closure when the device is in the first extreme axial position illustrated in FIGS. 1, 3 and 7.

The core 4 is biased in axial translation by elastic means such as a compression spring 31, pushing it towards its first extreme axial position shown in FIGS. 1, 3 and 7, against the bias exerted by the field magnetic generated by the winding 7. The spring 31 must have a return force greater than the axial force possibly exerted by the elements 14 and 15 with flexible blades, and less than the axial stress produced on the core by the magnetic field generated by the winding 7.

In the embodiment illustrated in FIGS. 7 and 8, the core 4 made of magnetic material occupies only part of the length of the axial channel 3. Its first end, fixed to the first element 14 with flexible blades, has an axial extension 40 force-fitted in a corresponding axial bore of the part forming the closure element 24. The second end of the axial core 4 has a diameter which is slightly reduced, and comprises a threaded axial bore 41 into which a tie rod 42 for connection with the second element 15 with flexible blades. A barrel 43 is engaged on the tie rod 42 between the second end of the axial core 4 and a first face of the central part of the second element 15 with flexible blades. A nut 44 is screwed onto the end of the tie rod 42 and comes to bear on the other face of the central part of the second element 15 with elastic blades. The spring 31 is a compression spring engaged between the nut 44 and an end flange 45 of the frame 2.

The invention finds in particular applications in the control of gas flow.

The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field of claims below.

Claims (10)

Sliding core electromagnet control device (4), in which: - a fixed armature (1), provided with an electric winding (7) and an axial channel (3), generates in said axial channel (3), between a first pole (5) and a second pole (6) , a magnetic field during the passage of an electric current in its winding (7), - a movable core (4) sensitive to the magnetic field is driven in axial sliding in said axial channel (3) by said magnetic field and is guided by at least two elements (14, 15) with flexible radial blades (18) comprising a part peripheral (16) mounted fixed relative to the fixed frame (1) and connected by said flexible radial blades (18) to a central part (17) integral with the sliding core (4), to hold the core (4) at the separation of the walls of the axial channel (3) while allowing its axial displacement according to an appropriate stroke between a first and a second extreme axial positions, characterized in that: - the axial channel (3) passes right through the electric winding (7), - The elements (14, 15) with flexible radial blades (18) are disposed respectively on either side of the ends of the axial channel (3). Device according to claim 1, characterized in that the axial guide means comprise two elements (14, 15) with flexible blades offset axially on the core (4), to the exclusion of any guide sliding in the axial channel (3) . Device according to one of claims 1 or 2, characterized in that the flexible blades (18) have, in the first extreme axial position in the absence of magnetic field produced by the fixed armature (1), a permanent deformation in bending in the direction of axial movement (II) of the core (4) in a first direction (20), the magnetic field causing the displacement of the core (4) in the opposite direction (19) to said first direction (20). Device according to claim 3, characterized in that, in the second extreme axial position, the flexible blades (18) of at least one of the elements (14, 15) with flexible blades are substantially flat, in order to have better radial rigidity. Device according to any one of Claims 1 to 4, characterized in that: the first pole (5) defines with the core (4) a first constant radial air gap independent of the axial position of the core (4) in said axial channel (3), - The second pole (6) defines with the core (4) a second constant radial air gap independent of the axial position of the core (4) in said axial channel (3). Device according to any one of Claims 1 to 4, characterized in that: the first pole (5) defines with the core (4) a first constant radial air gap independent of the axial position of the core (4) in said axial channel (3), - The second pole (6) defines with the core (4) a second radial air gap which decreases as a function of the axial displacement of the core (4) from the first extreme axial position towards the second extreme axial position. Device according to any one of Claims 1 to 6, characterized in that the core (4) carries a closure element (24) housed in the opening (25) of a seat (26) of a duct for fluid conduction for modifying the open section of said fluid conduction conduit as a function of the axial position of the closure element (24) in said seat (26), constituting an electrically controlled valve. Device according to any one of Claims 1 to 7, characterized in that the respective flexible blades (18) of the elements (14, 15) with flexible blades wind in the same direction around the longitudinal axis (II) of the device. Device according to any one of Claims 1 to 8, characterized in that the core (4) is biased in axial translation by elastic means (31) pushing it towards the first extreme axial position against the bias exerted by the magnetic field generated by the coil (7). Device according to any one of claims 1 to 9, characterized in that the peripheral part (16) of the elements (14, 15) with flexible radial blades (18) is directly attached to the frame (2).

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