EP0230819A1 - Miniaturised gyromagnetic device and method for assembling the same - Google Patents

Abstract

The invention relates to a gyromagnetic device such as an isolator, operating in very high frequencies (1-40 GHz). The assembly of gyromagnetic devices requires great positioning precision, generally obtained by gluing. In the insulator of the invention, the conductive core (12) and the two ferrite plates (13, 14) are held by two internal ground plates (17, 18) which form a positioned assembly, one of the plates (17) being provided with tongues (22) which position the parts (12, 13, 14) and which cooperate with slots (23) in the other mass plate (18). The assembly is obtained by stacking inside the housing (21) a pressure washer (20), the magnet (19), the positioned assembly (12, 13, 14, 17 , 18), of the base (21bis), and closure of the device by a single electrical weld. Applications to microwave equipment.

Description

The present invention relates to a miniaturized and integrated gyromagnetic device, and to its method of assembly and production. The gyromagnetic device according to the invention operates in the microwave domain, in the range from 1 to more than 40 GHz. By "integrated", it should be understood that this device forms an assembly which is no longer removable, except destruction, when it is completed: it therefore forms a whole, which can be considered as an elementary microwave component.

Microwave devices are experiencing a great development due in part to their increasingly frequent use in all fields in which electrical signals are transmitted in the form of waves in or out of the atmosphere - telecommunications, radar, satellite - but also because that they have taken forms easier to use than tubes and metal waveguides. The microwave sources are now semiconductor pellets - at least for small powers - and the guides are micro-bands, which allows the creation of circuits, hybrid or integrated, but always compact.

However, the production of certain microwave components, such as gyromagnetic components, circulators, gyrators, phase shifters, etc. which combine a conductive core and at least one piece of ferrite and a magnet, requires high precision mechanical mounting: 1 / 100th of a millimeter on the thicknesses and on the respective positions, which leads to assembly difficulties and a high price.

The gyromagnetic device according to the invention has been studied with a view to facilitating its assembly, according to a simple process, therefore rapid and inexpensive.

In addition, it is an object of the invention to have a miniaturized microwave component because its design eliminates all mechanical means such as screws for assembly: miniaturized, it can be integrated on a hybrid circuit.

It is yet another object of the invention to provide means for absorbing thermal expansion during operation of the device. When these compensation means are not provided, the ferrite parts may break.

The gyromagnetic device according to the invention comprises conventional parts: a conductive core provided with external access connections, at least one ferrite part and an absorbent load, at least one magnet and an internal mass, the whole being mounted in a box. . It is characterized in that the parts which must be assembled and positioned with precision - in particular the core and the ferrites - form a whole clamped between two parts of internal mass provided with reciprocal fixing means, the external or internal forms of these different parts being complementary, which ensures precise positioning.

It is also characterized by the magnet positioning part which is a non-flat pressure washer, the elasticity of which absorbs thermal expansion.

The assembly process of the gyromagnetic device according to the invention is characterized by a simple stacking of parts whose external or internal shapes automatically ensure the correct positioning.

It is also characterized by the fact that, when the parts are stacked in the case, a single electrical welding of the cover on the case ensures the closure of the gyromagnetic device in an integrated component.

More specifically, the invention relates to a miniaturized and integrated gyromagnetic device, comprising, inside a case closed by a base, a conductive core, two ferrite plates, an internal mass and a magnet, this device being characterized in that the conductive core and the two ferrite plates are held integral and precisely positioned by two internal ground plates, made of non-magnetic material, one of these plates comprising tabs which cooperate with slots formed in the other plate for reciprocal fixing enclosing the core and the ferrite plates.

• - Figure 1 : vue éclatée d'un dispositif gyromagnétique selon l'art connu,
• - Figure 2 : vue éclatée d'un dispositif gyromagnétique selon l'invention,
• - Figure 3 : vue en coupe d'un dispositif gyromagnétique selon l'invention,
• - Figure 4 : vue de trois quart d'un dispositif gyromagnétique selon l'invention,
• - Figure 5 : vue de trois quart des deux pièces de masse interne,
• - Figure 6 : vue en plan de la pièce dans laquelle l'âme est découpée,
• - Figure 7 : vue dans l'espace du mannequin de prémontage de pièces qui doivent être positionnées avec précision,
• - Figure 8 : vue dans l'espace de l'outillage de fermeture par soudure électrique du dispositif gyromagnétique selon l'invention.

The invention will be better understood from the following description of an example application, this description being based on the appended figures which represent:

• - Figure 1: exploded view of a gyromagnetic device according to known art,
• - Figure 2: exploded view of a gyromagnetic device according to the invention,
• - Figure 3: sectional view of a gyromagnetic device according to the invention,
• - Figure 4: three-quarter view of a gyromagnetic device according to the invention,
• - Figure 5: three-quarter view of the two pieces of internal mass,
• - Figure 6: plan view of the part in which the core is cut,
• - Figure 7: view in space of the pre-assembly dummy of parts which must be precisely positioned,
• - Figure 8: view in space of the closing tool by electrical welding of the gyromagnetic device according to the invention.

In order to simplify the expression in the text, the invention will be explained based on the case of an isolator, which in no way limits the scope of the invention which relates to any gyromagnetic device.

The preliminary review of the structure of a gyromagnetic isolator according to the known art will allow a better understanding of the basis and the advantages of the gyromagnetic device according to the invention. Figure 1 gives an exploded view of an insulator according to the known art.

An insulator comprises a core 1, a metal part in the shape of a three-pointed star, at 120 °, taken between two parts, in the form of a wafer, of ferrite 2 and 3. Two branches of the core 1 terminate in fittings coaxial 4 and 5 which constitute the external access connections to the insulator, the third branch is joined to an absorbent load 6, which is a resistor, one end of which is grounded. The assembly of the metallic core 1 and of the two ferrite plates 2 and 3 is clamped between two parts 7 and 9, forming a ground plane. These two parts 7 and 9 have a sufficient thickness so that two magnets 8 and 10 can be accommodated there. In addition, the thickness of the two parts forming a ground plane 7 and 9 makes it possible to use them as protective casing for the insulator, the coaxial external access connectors 4 and 5 and the connector base 6 in which the absorbent load is found then serving as a means of fixing the two bases relative to each other, by means of the fixing screws of the coaxial connectors. The case is completed by steel plates 11, which are glued on all sides, where there is not a base of coaxial connectors: these steel plates 11 serve on the one hand to make the device relatively watertight, to prevent dust from entering it which could create a short circuit, and on the other hand to form a magnetic shielding around the insulator.

Other embodiments of an insulator than that which is represented in FIG. 1 exist and are known: however, in general, the various constituents, and in particular the core and the ferrite plates, are of first assembled with each other by means of a layer of adhesive, this assembly being very difficult to achieve since the parts of an insulator must be assembled with a positioning precision of the order of 1 / 100th of a millimeter.

In addition, it can be seen that no part can compensate for thermal expansion when the insulator is in operation, since the external as well as internal dimensions are imposed by the bases of the coaxial connectors 4, 5 and 6 which fix the positions of the two parts of ground plane 7 and 9. Finally, the mounting of such an insulator is a relatively long operation which first requires gluing the parts in good position and then screwing the coaxial connectors on the central part previously glued.

These various drawbacks are eliminated by the gyromagnetic isolator which is the subject of the present invention and of which an exploded view is given in FIG. 2.

The function of the different parts constituting this insulator according to the invention is comparable to the function of the parts constituting an insulator according to the prior art, but their external shape is adapted so as to be able to facilitate the mounting and the precise positioning of each part.

An insulator according to the invention comprises a conductive metallic core 12, which is taken between two ferrite plates 13 and 14. These ferrite plates are themselves integral with absorbent charges 15 and 16 and dielectrics 13bis and 14bis. The external shape of the dielectric plates 13bis and 14bis corresponds to an isosceles triangle, each vertex of which is truncated: the positioning of two truncated vertices corresponds to the outputs of the insulator according to the invention, by metal strips and the third truncated vertex corresponds to the branch of the star 12 which conducts the microwave energy towards the absorbent charges 15 and 16.

All of these three parts, that is to say the conductive core 12 and the two subassemblies: ferrite + dielectric + charge, 13 + 13bis + 15 and 14 + 14bis + 16 are kept in contact one on the other by means of two parts 17 and 18 made of copper or brass which constitute the internal mass of the device. FIG. 2 represents an insulator before its assembly: to hold together and reciprocally position the three aforementioned parts, the plate 13bis finds place between three tabs 22 of the lower ground plane 17, then the core 12 is superimposed on the plate 13bis and the plate 14bis takes place between the three tabs 22 of the lower mass: on this stack is placed the plate 18 of higher mass, which comprises three orifices 23 of shape and position adapted so that the tongues 22 pass through these orifices. When the stacking is carried out, it suffices to twist and fold down the tabs 22 to constitute a pre-positioned assembly with precision. In fact, the two plates 17 and 18 of internal mass also have a shape of triangle, the summits of which are truncated, this shape of triangle corresponding to the shape of triangle of the plates 13bis and 14bis, and the assembly being machined and adjusted with an accuracy of the order of 1 / 100th of a millimeter.

The positioning of the metal core 12, which does not have an outer triangle shape whose vertices are truncated, will be explained later, during the assembly process.

In addition, the insulator according to the invention comprises a magnet 19, which is held in place by means of a washer 20 in the housing 21 of the device. This case 21 is closed when the assembly is completed by means of a plate 21bis, the parts 21 and 21bis being made of steel.

The washer 20 is a pressure washer, it is therefore made of steel or of beryllium bronze and it comprises means 23 for holding and centering the magnet 19; these means being folded back on one side of the main plane of the washer 20, and means 24 giving it an elasticity which makes it possible to compensate for thermal expansion or to absorb expansion during closing by electrical welding, these means 24 being formed by tabs folded along another side of the main plane of the washer 20.

The conductive metallic core 12 has two branches 25 and 26 for external access to the insulator, these two branches being constituted by microstrips. It also comprises a branch 27 which is located, inside the completed device, located between the two absorbent fillers 15 and 16. Furthermore, as shown in this FIG. 2, the core is manipulated in the form of a frame 28 in which the soul proper is chemically cut. This frame 28 will be justified later: it serves to center the core with respect to the ferrite plates.

3 shows a sectional view of an insulator according to the invention when the parts of Figure 2 are assembled and compressed. FIG. 3 is only reversed with respect to FIG. 2, that is to say that it rests on its base 21bis as is normal, while FIG. 2 corresponds to the stacking of the parts in the box 21, that is to say during the production of an insulator.

FIG. 4 represents a three-quarter view of a completed insulator: by way of example, while the insulator according to the known art of FIG. 1 constitutes an object three centimeters on one side and one and a half centimeters thickness, approximately, with access by coaxial connections, the insulator according to the invention constitutes an object of substantially cubic shape of approximately 6 mm on a side, not removable since it is electrically welded, provided with a base 21bis just enough large to allow screwing or bonding on a hybrid circuit. The small dimensions allow the microstrip 25 and 26 to be connected to an external circuit without passing through coaxial connectors.

FIG. 5 represents a view of three quarters of the two parts 17 and 18 of the internal mass. As has been said, these two parts are made of a material such as copper or brass and both have an overall shape of an isosceles triangle whose vertices are cut. But one of the two, the part 17 for example, is provided with tabs 22 which are cut from the same plate as the part 17, these tabs being folded at right angles, and one of them being longer than the others so as to allow manipulation of the assembly by means of tweezers. The other internal mass part, part 18, is provided with holes 23 in the form of slots whose position and dimensions correspond to the tongues 22. When the core 12 and the ferrite parts 13 and 14 as well as the absorbent charges 15 and 16 are positioned between the two pieces of internal mass 17 and 18, it suffices to lower the piece 18 by sliding it along the tongue 22 which is the longest to form a sandwich of pieces, then to fold the tabs 22 to form a whole compact and easy to handle. Of course, the dimensions of the parts 17 and 18 are calculated so that the dielectric parts 13bis and 14bis which come to stack between the tongues are positioned to the nearest hundredth of a millimeter.

It is remarkable that the assembly and positioning of all these parts no longer requires any bonding.

FIG. 6 represents a plan view of the frame 28 in which the core 12 is cut. This frame 28, obtained by mass production and by means of chemical cutting, has the particularity of comprising, surrounding the core 12 with its branches 25, 26 and 27, an internal cutting whose edges 29 correspond to the shape outside of the case 21 of the insulator according to the invention. Thus, while the dielectric pieces 13bis and 14bis are centered by means of their outer edge relative to the ground plane pieces 17 and 18, the conductive core 12 is itself centered by means of the inner edge of its frame by compared to the outside edge of the case.

FIG. 7 represents a view in space of the pre-assembly mannequin of the parts which must be positioned: this figure will make it possible to better understand the operations of the method of assembling the insulator according to the invention, as well as the centering of the core 12, and the role that the metal frame 28 plays in this centering.

To ensure the pre-assembly of all the parts 12, 13, 14, 17 and 18 which must be assembled with a precision of the order of a hundredth of a millimeter, a mannequin 30 is used, which has the same external contour 31 as the case 21 of the device. This mannequin 30 has inside its volume an extractor 32, which passes through the base of a mounting tool 33. In the case of FIG. 7 the extractor 32 is shown in the high position for the sole purpose to show it.

The method of assembling a gyromagnetic device according to the invention consists in stacking on the assembly tool of FIG. 7, the extractor 32 being in the low position, the following parts in order:
- the lower ground plane 17,
- a ferrite 13 and dielectric plate 13 bis with its absorbent load 15,
the core 12 supported by its metal plate 28,
- a ferrite 14 and dielectric plate 14bis with its absorbent charge 16,
- the upper ground plane 18.

The parts which have a form of triange whose vertices are truncated pile up automatically inside the mannequin 30: one can thus say that they are centered between them by means of their external contour. On the other hand, the core 12 which does not have a triangle shape is centered on the external contour 31 of the mannequin 30 by means of the internal contour 29 of the cutout in the frame 28.

When all of these parts are positioned in order, it suffices to exert a light pressure on them and to twist the tabs 22 secured to the mass plate 17 to form a compact and homogeneous unit, which can be manipulated.

This compact, homogeneous and prepositioned assembly is extracted from the mounting dummy 30 and is brought as a whole into the assembly of the gyromagnetic circuit according to the invention.

This assembly consists of depositing inside the case 21:
the washer 20 for compensating thermal expansion and the magnet 19 which is held by the lugs 23 of the washer 20,
- the compact and pre-centered unit, previously formed,
- the steel plate 21bis which constitutes the base for fixing the insulator.

The operations for producing an insulator are completed by means of a single electrical weld which fixes the box 21 to the base 21a.

Figure 8 illustrates this electrical welding operation. A base 35 of the electrical welding tool comprises a first housing 36 in which the housing 21 of the insulator takes place with precision, and a second housing 37 which allows to precisely position also the base 21bis relative to the housing. The assembly is pressed between two electrodes between which an electric current passes which ensures the final closure of the gyromagnetic device by welding the base 21bis to the housing 21. This welding is done with respect for positioning dimensions, in particular thanks to a metal edge, supported by the housing 21, which comes to bite into the base 21bis. During the welding operation, the expansion compensation washer is compressed to a predetermined dimension, so that the internal components are subjected to constant pressure.

After closing the case by electrical welding, the frame 28 is cut flush with the microstrips 25 and 26. To make FIG. 8 more readable, this frame 28 is not shown there.

The device according to the invention is essentially used in microwave material, in particular radars and telecommunications systems.

Of course, the invention is not limited to the embodiment described and shown, and includes all the technical equivalents of the means described as well as their combinations if these are carried out according to the spirit of the invention and implemented in the scope of the claims which follow.

Claims (9)

1. Miniaturized and integrated gyromagnetic device, comprising, inside a case (21) closed by a base (21bis), a conductive core (12), two ferrite and dielectric plates (13 + 13bis, 14+ 14bis), an internal mass (17, 18) and a magnet (19), this device being characterized in that the conductive core (12) and the two ferrite plates (13 + 13bis, 14 + 14bis) are held integral and positioned precisely by two internal ground plates (17, 18), made of non-magnetic material, one of these plates (17) having tongues (22) which cooperate with slots (23) formed in the other plate (18) for a reciprocal fixing enclosing the core (12) and the ferrite and dielectric plates (13 + 13bis, 14 + 14bis). 2. Gyromagnetic device according to claim 1, characterized in that the external contour of the ferrite and dielectric plates (13 + 13bis, 14 + 14bis), in the form of an equilateral triangle whose vertices are truncated, corresponds to the internal contour of the two internal ground plates (17, 18), the fixing tabs (22) ensuring the precise positioning of the ferrite and dielectric plates (13 + 13bis, 14 + 14bis). 3. Gyromagnetic device according to claim 1, characterized in that the magnet (19) is positioned in the housing (21) by means of a pressure washer (20), comprising, on one side of the main plane of the washer (20), a plurality of tabs (23) bent at right angles which hold the magnet (19) and, on the other side of the main plane of the washer (20), a plurality of tabs (24), bias, which absorb the thermal expansion of the gyromagnetic device in operation. 4. Gyromagnetic device according to claim 1, characterized in that the conductive core (12) comprises at least two external access connections each constituted by a microstrip (25, 26). 5. Gyromagnetic device according to claim 4, characterized in that the core comprises a branch (27) of energy absorption, placed between two absorbent charges (15, 16) each of the absorbent charges being in the plane of a ferrite plate (13, 14). 6. Gyromagnetic device according to claim 1, characterized in that the housing (21) is welded to the base (21bis), by an electric weld. 7. A method of assembling a gyromagnetic device according to any one of claims 1 to 6, characterized in that it comprises the production of a pre-assembled and positioned assembly, by means of a mannequin (30) having the same shapes and the same dimensions as the case (21) of the gyromagnetic device, this assembly being obtained by stacking in the mannequin (30):
- a first plate (17) of internal mass
- a first ferrite and dielectric plate (13 + 13bis)
- a conductive core (12)
- a second ferrite and dielectric plate (14 + 14bis)
- a second plate (18) of internal mass,
the tabs (22) of the first mass plate (17) being passed through the slots (23) of the second mass plate (18) then folded over to ensure compression and cohesion of the assembly. 8. A method of assembling a gyromagnetic device according to claim 7, characterized in that the core (12) is positioned, in the pre-assembled assembly, via the internal edge (29) of a cut out from a metal frame (28) which comprises said core (12), said internal edge (29) cooperating with the external contour (31) of the mannequin (30) for assembling the pre-assembled assembly. 9. A method of assembling a gyromagnetic device according to any one of claims 1 to 6, characterized in that it comprises the following series of operations:
- in the housing (21), install the washer (20) for pressure and thermal compensation, then the magnet (19),
- on the magnet (19), place the pre-assembled and positioned assembly (17 + 13 + 12 + 14 + 18)
- arrange the housing (21) and its content in the housing (36) provided in a first electrode (35) of an electric welding tool
- deposit the base (21bis) of the gyromagnetic device on the housing (21) and its contents, and in the housing (37) provided in the same electrode (35) of an electric welding tool,
- carry out electrical welding, under pressure, by means of a second electrode,
- remove the gyromagnetic device from the first electrode (35) of the welding tool,
- Cut the microstrips (25, 26) of access connections to the core, to eliminate the metal frame (28) for positioning the core.

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