EP0860667B1 - Conditioning system of components operating at cryogenic temperature - Google Patents

Description

The present invention relates to a system for packaging intended in particular for cooling electronic components during operation, from type comprising for this a cryogenic cooler suitable for implementing a thermodynamic cycle periodically involving alternative phases of compression and expansion of a working gas such as helium. Such a system is known from documents EP-A-0 672 873 and US-A-5,275,002.

It will advantageously find application in all equipment using electronic components which see their performance improved when they are maintained at cryogenic temperature, generally understood between 80 ° K and 200 ° K. Among these components, we can cite more particularly components based on materials high critical temperature superconductors, as well as magnetoelectric components, for which the bass temperatures lengthen the magnetic relaxation time.

To take full advantage of the improved component performance as it results directly keeping them at such low temperatures it appeared highly desirable to design systems and cryogenic cooling devices specially adapted. Rather than risk limiting or disrupt these performances, they are able to receive components in conditions that bring their own contribution in the same direction tending to increase performance, in particular by improving characteristics electric, increased sensitivity for weak signals, reduction of background noise.

To do this, the invention essentially aims to ensure the integration of components into a packaging which, while allowing their cooling at cryogenic temperature under particularly conditions advantageous, also constitutes their station reception, particularly from the point of view of resistance mechanical and thermal stability. It also has aim to always place better in the current race to miniaturization, by providing for a construction of the whole in an extremely compact form, and nevertheless solid, reliable for long periods of use, and competetive price. We will see later that it even allows escape from the classic arrangements where the component is placed at the end of a cold finger opposite a compressor generating pressure variations.

In its preferred embodiments, the invention responds better to the objectives set out here because, for a pneumatically controlled cooler as is the case with pulsed gas tube coolers derived from coolers more generally applying a Stirling cycle, it avoids the need for a gas buffer chamber maintained at constant pressure. It thus allows overcome the limitation of conventional solutions in this which concerns the volume of the cooler. Furthermore, such design removes most parts mobile mechanics, with the difficulties of their adjustment, which goes in the direction of better quality in reliability of construction and operation and in longevity.

To find explanations on solutions known to date, we can usefully refer to a Damien Feger's article entitled "Cooling of optoelectronic detectors "published in" Techniques of Engineer, Electronic Treaty "pages E4070-1 to 11. This article often remains at the level of principles, we can have an interest in referring in addition to achievements concrete described in patent texts filed by the Applicant company.

We will simply recall here that the process thermodynamics applied in coolers of the kind considered consists, at the theoretical level, in subjecting gas a repetitive closed circuit cycle including a compression phase and an expansion phase, both on the other, a thermal regenerator which ensures delayed thermal recovery between gases relaxed cold and hot compressed gas. The regenerator therefore constitutes a thermal sponge which, alternatively, retains heat from the gas resulting from the compression by accumulating it, and then restores it to gas from the relaxation phase.

The regenerator is conventionally produced in the form an elongated tube at one end of which is the area cold in thermal contact with the component to be cooled. It is filled with a porous structure, bringing great specific surface for heat exchange, which is made of a material with low thermal conductivity clean.

The presence of such a regenerator being general of known Stirling cycle coolers, the solution of pulsed gas coolers basically consists of replace the displacer regenerator (then mounted mobile at sliding in the cold finger) by a regenerative exchanger fixed, and to complete the working gas circuit by a tube called pulsed gas, or pulsation, which receives the pressure change pulses from the pressure oscillator compressor via an appropriate pneumatic connection. In operation it a corresponding dynamic pressure variation is established there to that of a gas piston, thanks to the introduction a phase shift between pressure variations and variations in flow created by reference to a low buffer tank pressure whose volume is constant.

In practice, this phase shift is ensured thanks to the presence of one or two valves on the connection circuit pneumatic between the pulsation tube and on the one hand the compressor generating pressure oscillations, other share the buffer tank at constant pressure and volume. These valves are generally simple calibrated orifices, in the concern to avoid moving mechanical parts.

In the context of the prior art which has just been recalled, the invention therefore relates to a packaging system components operating at temperature cryogenic, cooled by subject working gas to a closed circuit thermodynamic cycle, according to a periodically repetitive cycle involving alternative phases compression and expansion, in a cooler of the pulsed gas type including the working gas circuit has a pulsation tube extending between an exchanger cold in thermal contact with the component to be cooled and a hot heat rejection exchanger to the outside.

To meet the main objectives set out previously, the system according to the invention presents a series of characteristics according to claims 1 and 17.

According to one of its main characteristics, the invention consists essentially in providing the tubes to pulsations in a block of parallelepiped shape or equivalent, constituting the core of the cooler and made of a thermally insulating material, which supports the cold heat exchanger and the hot heat exchanger attached respectively against two opposite lateral faces of said block, and which also supports, on a so-called face top of the same block, a transfer device thermal between expanded cold gas and compressed hot gas.

According to another of its main characteristics, the invention proposes to avoid the conventional valves of flow / pressure regulation at a circuit supply single pulsed gas, by placing its tube in series pulsations and its thermal transfer device between cold expanded gas and compressed hot gas, consisting of a leads to delayed heat transfer regenerator in time, between two supply channels under periodically variable pressures in phase opposition.

According to yet another of its characteristics main, which will generally be preferred, the invention proposes that the cooler comprises two similar working gas circuits, operating in opposition phase, whose pulsation tubes are arranged at within a single block of thermally insulating material supporting the cold exchanger and the hot exchanger, these being common to both circuits, as well as a device for heat transfer between expanded cold gas and hot gas compressed, consisting of a recovery exchanger with counter-current between the two gas flows supplying the pulse tubes belonging to the two respectively working gas circuits.

The main block integrating the hot exchanger and the cold exchanger constitutes with the transfer device thermal (especially the recovery exchanger) what we will call here the passive module of the system. It is advantageously enclosed in an encapsulation module forming a waterproof and insulating housing, including a bottom wall supports the component to be cooled against the cold exchanger.

In contrast, the recovery exchanger is preferably made integral with the main block, against a upper side of it which is oriented parallel to a common plane of the two pulsation tubes. In progress practical, the block is then of rectangular shape, and the cold and hot exchangers are attached to its faces side.

Furthermore, and according to an implementation mode preferred of the invention, it is expected to close the housing by a cover which at the same time constitutes a plate of heat rejection deviating from the block itself in the extension of the hot exchanger. This can happen at best by a flat plate of thermally material conductor which is mounted directly on the hot exchanger, insofar as this, in accordance with another characteristic of the invention, is produced in the form of a angled thermally conductive structure, covering the left side face of the block, and partially its face upper in its left part.

Naturally, it should be understood here that all expressions that refer to orientation (such that upper or lower, front or rear, right or left, horizontal or vertical) are used exclusively to make it easier for the reader to understand. Indeed, the operation remains the same regardless of the layout of the system in space.

With the same concern aimed at a manufacturing compact and high-efficiency miniature, the cold heat exchanger is preferably formed by an angled structure thermally conductive covering the right side face of the cooler block, and partially its underside in its right part.

While the lower portion, called horizontal, of this bracket receives the component to be cooled, it is so particularly convenient to use the interface between its vertical portion and the main block to provide communication channels belonging to each of the circuits working gas between the countercurrent recovery exchanger and their respective pulse tubes, or the case if necessary, between regenerator and pulsation tube of the same circuit. It is always desirable that the flow (s) gaseous have to cross an area with exchange surface important against the end section of the gas tube, this which is advantageously obtained by appropriate micro-machining of the material of the cold exchanger at this location.

All the features of the invention which just mentioned lend themselves to different configuration variants for the two gas circuits of work coupled by exchangers.

According to a first variant, each circuit includes, as usual, an accumulation regenerator and delayed thermal restitution between expanded gas and gas compressed, which is placed in series in the extension of the tube pulsation on the corresponding circuit. The configuration geometric may vary, especially depending on whether regenerative and pulse tube are in line on both sides of the cold exchanger, or that they are arranged in parallel one next to the other, according to the so-called U-shaped configuration, or that they are in a concentric arrangement.

The preferred solution in the context of the invention corresponding to the U-shaped configuration. The two regenerators, belonging respectively to each of the circuits of working gas, are then arranged in parallel with one the other in the thickness of the recovery exchanger as that it has been defined above. In series with the tubes, they receive the pressure pulses in phase opposition. The gas inlet channels and orifices are arranged at a same end, and the output ones at the other end, this which ensures the local effect of counter-current circulation.

According to a second variant, which will be preferred in most applications of the invention, the working gas circuits no longer have this kind of regenerator. In this case, the recovery exchanger thermal against the current only has its proper role in fill. In accordance with one of the modes of implementation preferred of the invention, it is sufficient that it is configured to force the working gas, in each of the two circuits, to follow a laminar serpentine path between an orifice of communication with pressure oscillator means and a communication orifice with one end of the tube to corresponding pulsations.

Such an exchanger can advantageously be produced by a three-layer composite assembly, comprising a intermediate layer of conductive material forming separator between appropriate corrugations dug into two outer layers to form the desired paths.

Other features of the invention relate to more specifically a so-called active module which is combined with system to generate the pressure oscillations intended to the periodically variable pressure supply in phase opposition, either of the regenerator and the tube pulsations of the same working gas circuit, i.e. preferably, one or the other of the two gas circuits of job.

Essentially, this generator or oscillator of pressure, advantageously attached to the housing or encapsulation module, in particular against a plate of heat rejection forming the cover face of the housing, is preferably of the type comprising a flexible element dividing a cavity formed within it into two chambers different, complementary volumes, which are in pneumatic communication with the supply channels, therefore preferably with each of the tubes respectively pulsations through the heat exchanger recovery against the current.

Such a flexible element, whether in the form a pivoting blade or under that of a fixed disc in sound perimeter, can be ordered in particular in its deformations (on either side of a middle position in said cavity) by any appropriate electrical means in relation with its constitution.

Other modes of implementing this invention result in a packaging system cryogenic components with the same characteristics with regard to the core of the cooler, with its associated cold and hot exchangers, and respecting the same principles for combining the three modules, but where one of the tubes in the passive module serves as regenerator for the other, on the same gas circuit job.

In the absence of a special recovery exchanger, a constant pressure tank can be provided in the active module containing the pressure generator, in particular behind a simple moving piston compressor. Else hand, the communication channels between the generator pressure and cooler can be adapted for offer a calibrated passage section ensuring a phase shift between flow and pressure in the gas circuit and put the two tubes in series.

The system of the invention responding to above features can be adapted to a single circuit working gas, as soon as it passes through a tube pressure pulsations formed in the heart block of the cooler and by a regenerative tube attached against it block in the passive module. The notion of tube must be understood here to extend to all forms of sections for a tubular conduit. In particular, the tube or integrated regenerative material conduit in the form of a plate attached to the main block will preferably present a rectangular section.

This same embodiment with a single gas circuit of work takes advantage, according to the invention, not only different characteristics regarding mechanical arrangements, the design of parts and their method of assembly, but also of the combination with a pressure generator with two complementary chambers. he it is no longer a question of supplying two opposing circuits phase, but to supply the pulsation tube with a room, the regenerator by the other.

• la figure 1 représente schématiquement un système de conditionnement réfrigéré à deux circuits de gaz de travail, vu suivant une coupe longitudinale décalée par rapport à son axe médian ;
• la figure 2 est une coupe schématique de son oscillateur de pression considéré en vue de dessus par rapport à la figure 1 ;
• la figure 3 montre plutôt l'échangeur de récupération dans le même genre de coupe schématique ;
• la figure 4 montre les trois modules principaux du système dans leur apparence extérieure suivant une vue éclatée avant assemblage ;
• et la figure 5 illustre en perspective la constitution du module passif d'un système à un seul circuit de gaz de travail.

The invention will now be more fully described in the context of its preferred characteristics and their advantages, with reference to the figures of the appended drawings which illustrate two particular embodiments thereof, and in which:

• Figure 1 schematically shows a refrigerated packaging system with two working gas circuits, seen in a longitudinal section offset from its median axis;
• Figure 2 is a schematic section of its pressure oscillator considered in plan view with respect to Figure 1;
• Figure 3 rather shows the recovery exchanger in the same kind of schematic section;
• Figure 4 shows the three main modules of the system in their external appearance in an exploded view before assembly;
• and FIG. 5 illustrates in perspective the constitution of the passive module of a system with a single working gas circuit.

• les fonctions d'un refroidisseur cryogénique à cycle thermodynamique mis en oeuvre dans un circuit fermé de gaz de travail au voisinage immédiat d'un composant électronique à refroidir,
• celles donc d'un générateur de pression associé, imposant périodiquement détentes et compressions alternatives du gaz de travail dans ce circuit,
• celles d'un boítier de protection formant aussi station d'accueil thermiquement isolante pour le composant et supportant ses connexions électriques avec l'extérieur.

The figures illustrate the component packaging system according to the invention in a particularly complete embodiment, integrating in the same mechanical, compact and solid assembly, all the mechanical and pneumatic means for ensuring:

• the functions of a cryogenic cooler with a thermodynamic cycle implemented in a closed working gas circuit in the immediate vicinity of an electronic component to be cooled,
• those of an associated pressure generator, periodically requiring expansion and alternative compressions of the working gas in this circuit,
• those of a protective housing also forming a thermally insulating docking station for the component and supporting its electrical connections with the outside.

Figures 1 to 4 relate to a system with two coupled pulsed gas circuits. In accordance with the invention, cooler and pressure generator define in actually two separate working gas circuits, which operate according to the same thermodynamic cycle, but in phase opposition to each other.

The two circuits combine with multiple levels, mainly through an interaction of their effects thermal in the cooler and their connections respective to the same oscillator generating variations pressure, but also at the heat exchangers on the one hand with the component to be cooled, on the other hand with the outside in heat rejection, plus the case which is common to them.

The two circuits are identical in their definition out of operation, and arranged in parallel between them. Their different parts will be referenced by the same numbers, followed by the letter a or b respectively. They stand behind each other in the arrangement of the section of figure 1

• un module dit passif 10, qui constitue le refroidisseur proprement dit,
• un module dit actif 20, qui comporte l'oscillateur de pression intégré,
• et un module d'encapsulation 30 formant boítier pour le refroidisseur avec ses échangeurs.

In the mechanical design of the assembly, we distinguish:

• a so-called passive module 10, which constitutes the cooler proper,
• a so-called active module 20, which includes the integrated pressure oscillator,
• and an encapsulation module 30 forming a housing for the cooler with its exchangers.

In the passive module 10, the core of the cooler is essentially formed by a parallelepipedic block 11, made of a solid material with good properties thermal insulation. Glass can be used for this purpose such as Pyrex or a ceramic material.

Two blind tubes 1a and 1b are dug in this block 11. They respectively belong to each of working gas circuits, only the tube being visible on the section of figure 1. In operation, each of tubes constitutes the pulsation tube of its own circuit, by transmitting pressure waves from one end to the other generated from the oscillator, according to the operation of a gas piston in a cycle thermodynamics of the pulsed gas type.

As it should be of a miniaturized construction for the implementation of such a cycle, the cooler integrates with it two exchangers, one 14 in the area hot, the other 16 in the cold zone. However, it is note that, in accordance with the invention, these two exchangers are common to the two working gas circuits. They are both made of a material with strong thermal conductivity, made in particular of a metal or a metallic compound, such as aluminum, silicon, sapphire, oxide beryllium, aluminum nitride, cupro-tungsten, molybdenum.

The cold exchanger 16 is in direct contact thermal with the component to be cooled 40, the latter being applied to it, and possibly attached to it by gluing. Naturally, it could be several components of the same electronic circuit. A particularly material well suited to constitute this exchanger is silicon monocrystalline orientation (110). This conductive support can also be pierced with micro-machined channels improving the heat exchange conditions. This is so in the example described for its zone which is located against the section end of the pulsation tubes.

As for the hot exchanger 14, it has the role, as it is conventional to provide heat rejection to outside. Like the cold heat exchanger, it is attached flat on one side of the block it at the end of the tubes 1a-1b, but at its opposite compared to these. For a cooler two horizontal tubes like the one in figure 1, the exchangers 14 and 16 cover the side faces of the block 11, respectively the one on the right, and the one on the left, here of the closed side of the pulsation tubes.

According to the invention, the passive module 10 additionally includes a third exchanger 13. Its function first is to ensure heat transfer between gases hot compressed and cold gas relaxed. It is therefore a thermal recovery. However, to the extent that the system has two coupled working gas circuits to operate in interaction, this exchanger of recovery is a counter-current exchanger between two parallel conduits guiding the gas flows supplying the two pulsation tubes. For this purpose, the gas pipes internal to the exchanger 13 are pneumatically connected, by communication channels which will be discussed later, with tube 1a or 1b of the same circuit on its open side, so right on figure 1.

From the point of view of mechanical manufacturing, this exchanger 13 is in the form of a flat plate, more or less thick depending on the passage section necessary for gas flows. And this plate is attached fixed on one of the faces of block 11. It therefore forms part integral of the cooler, i.e. of the passive module 10. It can even be formed directly by machining the same material as block 11 in some cases.

In one of the forms of implementation of the invention, which however is not the subject of a figure special in the accompanying drawings, the exchanger 13 plays simultaneously the role which is devolved, in a conventional manner, to the regenerator of Stirling cycle coolers. We here speaks of a fixed regenerator, since the thermodynamic cycle applied is of the pulsed gas type.

Such a cycle with thermal regeneration implies storage and return of heat so alternative during the cycle within the same tube, on each individual working gas circuit. To this end, the tube is filled with glass beads, or a structure analogous to high ρCp offering a large specific surface in a reduced space, so as to constitute a "sponge thermal".

In the context of the invention, the tubes regenerators are formed in two parallel conduits formed within the exchanger. Like gas flows circulate in phase opposition (from right to left one in one direction the other in the other in Figure 1), the effect regenerative combines with the specific regenerative effect that exchange provides against the tide. This is insured for example by microchannels which locally increase the thermal conduction through the mass of the exchanger.

However, the solution illustrated here is that of a exclusively recuperative cycle, in order to avoid constraints of filling with a regenerative material. We is then content to impose separately on the two gas flows respective traffic paths through the interchange such that an efficient heat exchange is established between them. In addition, the conduits in the exchanger are parallel by their inputs and outputs. In this way, the exchange is goes against the grain of the fact that at the same time two gas flows move there locally under the effect of pressure pulses they receive in opposition to phase.

In the case of the example chosen, the exchanger is in practical in the form of a mass of material thermally conductor in which two conduits are formed describing parallel serpentine paths. These two conduits are defined for a flow essentially laminar licking suitably oriented corrugations.

More precisely, the exchanger 13, of miniature construction, consists of a plate composite in three layers. The conduits 6a-6b are dug on the surface of the outer layers facing the intermediate layer. The latter serves as separator and conductor between the two circuits. The two layers exterior need not be conductive. Through photolithographic machining and assembly of the layers by bonding (chemical or electrochemical), we were able to achieve the exchanger under a thickness not exceeding 1 millimeter.

Now returning to the cold and hot exchangers, we can observe figures that they are constructed of particular way. Each is shaped like a structure flat folded square around an edge of the block 11 forming the heart of the cooler.

Thus, the square structure forming the exchanger cold 16 extends from the right lateral face of block 11 to the right side of its underside. The component to cool 40 is fixed in thermal contact above, preferably by gluing. In contrast, the square structure 14 forming a hot exchanger envelops the block on its part left, covering both a fraction of its face upper and all of its lateral face.

Indeed, it is expected that in operation, the left side of block 11, on the side where tubes la and 1b are closed, constitutes the hot zone of the cooler. The area cold is the opposite of the right side of block 11, where the tubes la and 1b open to be put in communication with the means which make it possible to generate pulsations of pressure (oscillator 20) via the exchanger against the current 13.

In addition, a flat plate 15, produced in a highly thermal conductive material, is reported on block 11 to better ensure heat rejection to outside. Still in the layout of Figure 1. it is actually located away from the upper side of the block 11 in its entire right part, while on the left it is sealed on the hot exchanger, by electrochemical process or by collage. It is therefore an extension of the hot exchanger for the evacuation of the heat to from block 11.

As can be seen in the figures, and as we have already indicated, the core of the cooler, integral exchangers forming with it the passive module 10, and with the component glued on its underside, is mounted inside the encapsulation module 30.

The latter forms a waterproof case which is closed by a cover constituted by the plate 15 for rejection of heat. The dimensions of the latter are sufficient for cover the upper edge 31 of the walls of the housing shown vertical.

The wall forming its bottom 32 supports a circuit printed 33 which provides the electrical connections between the component 40 and outlet tabs 34, via of waterproof insulating bushings 36. It is schematically illustrated that outside of the assembly, the legs 34 are connect to a printed circuit 35 supplying the component 40 and electronic signal processing that it provides.

Furthermore, the dimensions of the housing 30 match those of block 11 in width (depth in FIG. 1), plus the thickness of the exchangers in width. Subject a tight bond between the facing surfaces, can fill the environment closed by the hot exchanger a heavy inert gas, such as a mixture of xenon and krypton. However, it is preferable to have the empty in the space below block 11. As a variant, we can also plan to fill these empty spaces with a filling material or by height variations the rectangular section of the main block.

On the right side of this block, orifices and channels 2a and 2b are delimited in the structure of the cold exchanger 16, more precisely here at its interface with the block main, so as to ensure communication between each of the open ends of the tubes la and 1b respectively and the right end of the counterflow heat exchanger 13. At the left end of the same exchanger, we finds holes 3a and 3b respectively, which are drilled from him through the cover plate 15 up the pressure oscillator.

For convenience of interpretation, Figure 1 shows the channels and orifices 2a and 3a in the same plane diametral of the pulsation tube la, before and after the convolutions in the exchanger 13. Their counterparts in the other working gas circuit are assumed to be located behind. For reasons of parallelism of the paths to inside the exchanger 13 and identity between their lengths, we may prefer a distribution of inputs and outputs.

From another point of view, we notice in the figures only on the warm side, the two pulsation tubes la and 1b, there where they are closed blind with left, are nevertheless connected between them by a capillary piercing. This capillary 61 is shown pierced through the material of block 11. It could just as easily be arranged at the interface between this block and material of the hot exchanger 14. Its presence enough to play a role of phase shifter similar to that of conventional valves for pulsed tube coolers, in the phase shift regulation between flow and pressure at the supply of the pulsed tube, taking into account the fact that this feed is itself out of phase in one of the tubes by compared to each other.

The active module 20, generating the pulsations of pressure, is mounted on the cover plate 15 as it is shown in the figures. It is made up of a mass of thermally conductive material, generally in shape parallelepiped which is applied on the face upper side of the encapsulated passive module. However, it extends beyond the housing 30 on the hot side of the cooler, and it is notched in this place to form fins 22 which contribute effectively to the evacuation of heat towards outside.

The mass 21 encloses a sealed cavity 23, which contains a flexible element which divides it into two chambers of variable volume in addition to each other, in part and on the other side of a median position of rest of said element where they are in pressure balance. The two bedrooms 4a and 4b belong respectively to each of the gas circuits of work. For this, the bottom wall of the module is pierced by two holes 5a and 5b which are placed exactly in correspondence with the homologous orifices 3a-3b of the plate 15.

In the embodiment shown, the element flexible that separates the two complementary chambers is consisting of a pivoting blade 26. It is a blade rectangular which is embedded waterproof in the mass of the module at one of its ends, at 27 right on the Fig. Its other end is free; during deformations of the blade, it slides in contact on the wall opposite internal cavity 23, which is curved for this purpose.

On either side of its median rest position, the blade 26 goes to symmetrical extreme positions where it is applied against the wall of the cavity 23. A shape adapted from this wall reduces the corresponding room to a zero volume at maximum pressure in its circuit. In practical, functional play on the three free slots of the slide is of the order of 50 microns.

According to an implementation variant of the invention, the blade 26 is replaced by a disc circular which is flexible to be deformed by its center and which is built-in waterproof all around its perimeter wall of the cavity 23, which is then of section circular, at least in this place, that is to say in its vertical median plane.

The blade 26 is associated with control means electric which give it a deformation movement periodic, alternately on either side of the plane median of the cavity 23. These means are illustrated on the Figure 2 by two pairs of electrodes. Each couple comprising an electrode 27a-27b integral with the blade 26 which is brought to the reference voltage, and an electrode in look 28a-28b in the wall of the cavity 23. The electrodes of each pair, 28a and 28b, are subject to opposite periodic voltages, which combine their effects in blade attraction and repulsion 26.

We have shown schematically in the figure 2, wires 24 and 29 for the electrical supply of electrodes. A control circuit, not shown, ensures the regulation of the deformations of the blade 26; it is fixed plated on the oscillator housing. In Figure 2, the external electrodes appear in volume in the mass of the oscillator housing, but they are preferably made by simple conductive coatings deposited on the surface of the cavity walls 23, and supplied as the internal electrodes from the right side of the oscillator.

While remaining within the framework of this invention, the mode of control of the deformations of the element flexible generating pressure oscillations can be materialize under different variants. In particular we can use a rectangular blade made of piezoresistive material multi-layered in which are embedded two electrodes in Kovar, the electrical contacts being provided by metallic deposits at the level of its embedding in the oscillator housing.

The casing 21 of the active module is for example in alumina, material with good thermal conduction and high electrical resistance. It is metallic on its face lower to be sealed by welding on the plate 15.

For example, a packaging system such as described and illustrated by the figures can be achieved, by view of a cooling power of 100 mW at 180 ° K for a ambient temperature of 30 ° C, in dimensions of 35 mm by 25 mm by: 25 mm, with a ceramic case with a wall thickness of 1.5 to 2 millimeters, and an oscillator providing pressure pulses at a maximum excursion of 20% compared to a pressure of loading of 2 bars.

The invention is not limited to the mode of preferred embodiment described above with reference to Figures 1 to 4, it will be recalled that the exchanger 13, described in part of a purely regenerative cycle, can be replaced by a delayed heat transfer device between gases relaxed cold and hot compressed gas, involving filling gas conduits of energy-storing material thermal to then restore it during the phases of the cycle. The conduit belonging to each circuit then plays the role of a regenerative tube, in series with the corresponding pulses between communication channels with the associated chamber of the pressure generator. Yes necessary, the different channels can be calibrated in the passage section they offer to the working gas.

Figure 5 of the accompanying drawings illustrates a variant of the system of the invention in which the oscillator as already described is used in combination with a passive module similarly encapsulated in its case, but in which the core of the cooler does not has more than one working gas circuit, including a pulsation tube in series with a device for regenerative type thermal recovery.

The cooler core has a tube single pulsation 51 dug longitudinally in the block principal 11. The general structure of the passive module is constructed as above. The tube 51 opens out the interface with the cold exchanger 16, in an area where its material is micro-machined to increase its surface specific in communication with a vertical channel 52. From opposite side, we see the hot exchanger 14, which is formed here in one piece with the plate 53 of the recovery over block 11.

Unlike the previous case, the tube 51 opens also on the left side of block 11, in a channel 54 which closes the gas circuit by communication with one of the pressure oscillator chambers (chamber 4a of the figure 2). The other bedroom, via channel 55, communicates with the left end of the regenerator 56 formed in the plate 53, on the hot side of the cooler. On the cold side, the gas circuit closes between regenerator 56 and tube 51 via channel 52 already mentioned.

Regenerator 56 forms a section duct flattened in the plate 53. The regeneration effect by recovery from the work developed at the hot spring is obtained by constituting it by a material made of a mosaic of glass blocks micro-machined by photolithography in surface of a glass plate, in dimensions from 100 to 200 microns. The plate 53 is therefore actually constituted by two glass plates assembled, with a full plate 58 covering the micromachined plate 57.

In the cooler thus formed, the operation in accordance with a regenerative pulsed gas cycle is provided by the oscillator as it would be by a second double-acting compressor piston instead phase shift valves and solution buffer tank classics. Among the advantages obtained, this thus removes dead volumes, which are always penalizing, especially at miniature scales.

Finally, we will have understood in all forms of realization described, it will be convenient to do widely use of chemical or electrochemical bonding techniques to assemble the different parts constituting the modules of the system of the invention, to the techniques of photolithography and ultrasonic drilling to carry out the machining, and glass / metal welding techniques or ceramic / metal for electrical bushings waterproof.

Claims (24)

1. System for conditioning components operating at a cryogenic temperature, with cooling by a working gas undergoing a thermodynamic cycle in a closed circuit, following a periodically repetitive cycle involving alternating compression and expansion phases, in a cooler of the pulsed-gas type whose working-gas circuit comprises a pulse tube (1a, 1b) lying between a cold exchanger (16) in thermal contact with the component to be cooled and a hot exchanger (14) for removing heat to the outside,
   characterized in that the said cooler (30) comprises two similar working-gas circuits operating in phase opposition, whose pulse tubes (1a, 1b) are made within the same block (11) of thermally insulating material supporting the said cold exchanger (16) and the said hot exchanger (14), both of the latter being common to the two circuits,
   and a recovery device (13) for countercurrent heat transfer between the two gas streams feeding the pulse tubes belonging respectively to the two working-gas circuits.
2. System according to Claim 1, characterized in that the said block is enclosed, with the said hot exchanger and the said cold exchanger, in an encapsulation module forming a sealed casing and which has a bottom forming a support for the component to be cooled against the said cold exchanger.
3. System according to Claim 1 or 2, characterized in that the said recovery device is an exchanger configured to force the working gas, in each of the two circuits, to follow in parallel a laminar coiled path between a channel communicating with pressure oscillation means and a channel communicating with one of the ends of the corresponding pulse tube.
4. System according to Claim 1 or 2, characterized in that the said recovery device (13) consists of a solid block of thermally conducting material incorporating heat accumulation regenerators and delayed exchange between a hot gas and a cold gas which belong respectively to each of the said working-gas circuits and which are arranged in parallel between an orifice communicating with pressure oscillation means and an orifice communicating with one of the ends of the corresponding pulse tube.
5. System according to Claim 3 or 4, characterized in that the said recovery device (13) is formed so as to be securely fastened to the said block (11) against an upper face thereof parallel to a plane common to the two pulse tubes of the said working-gas circuits.
6. System according to any one of Claims 2 to 5, characterized in that it comprises a wall forming a lid closing the said casing, which wall is formed by a heat-removal plate (15) made of a thermally conducting material, separated from the said block (11) by the extension of the said hot exchanger (14).
7. System according to any one of Claims 1 to 6, characterized in that the said hot exchanger (14) is formed by a thermally conducting angle bracket overlapping a left lateral face and, partially, the left part of an upper face of the said block.
8. System according to Claim 7 combined with Claim 6, characterized in that the heat-removal plate (15) is mounted on the hot exchanger in the shape of an angle bracket (14) in its part partially overlapping the said upper face of the block (11).
9. System according to any one of Claims 1 to 8, characterized in that the said cold exchanger (16) is formed by a thermally conducting angle bracket overlapping a right lateral face and, partially, the right part of a lower face of the said block (11).
10. System according to Claim 9, characterized in that communication channels belonging to each of the working-gas circuits between the countercurrent recuperator exchanger (13) and their respective pulse tubes (1a, 1b) are made at the interface between the said block (11) and the cold exchanger (16) in its portion overlapping its right lateral face.
11. System according to any one of Claims 2 to 6, characterized in that it comprises a pressure oscillator in order to generate pulses of varying pressure in each of the said circuits in phase opposition, alternating between compression and expansion, which oscillator is securely fastened to the said casing.
12. System according to Claim 11, characterized in that the said pressure oscillator is fastened against a heat-removal plate (15) forming the lid of the casing according to Claim 6.
13. System according to Claim 11 or 12, characterized in that the pressure oscillator is of the type comprising a flexible element (26) dividing a cavity (23) made in the said oscillator into two different chambers (4a-4b), of complementary volumes, which are in pneumatic communication with each of the pulse tubes respectively via the countercurrent recuperator exchanger (15).
14. System according to Claim 13, characterized in that the said flexible element (26) is combined with electrical means for controlling its deformations on either side of a mid-position in the said cavity (23), in order to create periodic pressure pulses in the said circuits which alternate between high pressure in one and low pressure in the other.
15. System according to Claim 14, characterized in that the said electrical control means comprise fixed electrodes (28a-28b) for attracting opposite electrodes (27a-27b) respectively, borne by the said flexible element (26), and circuits for powering the electrodes and for control, these being fastened to the said solid block.
16. System according to any one of Claims 11 to 15, characterized in that the pressure oscillator is in the form of a solid block (21) of parallelepipedal shape having heat distribution fins in a part placed so as to overlap the casing (30) on the side of the hot exchanger when it is fastened to the heat-removal plate (15) according to Claim 6.
17. System for conditioning components operating at cryogenic temperature, with a cooler of the pulsed-gas type whose working-gas circuit comprises a pressure pulse tube (51) lying between a cold exchanger (16) in thermal contact with the component to be cooled and a hot exchanger (14) for removing heat to the outside, characterized in that the said pulse tube (51) is made within a block of thermally insulating material (11) supporting the said cold exchanger and the said hot exchanger, and in that another tubular duct (56) made in parallel against the said block is connected in series with the said pulse tube (51) on the said circuit and filled with a regenerating material providing heat recovery delayed in time.
18. System according to Claim 17, characterized in that the said block (11) is enclosed, in an encapsulation module forming a sealed casing and which has a bottom forming a support for the component to be cooled against the said cold exchanger.
19. System according to Claim 18, characterized in that it comprises a wall forming a lid closing the casing, which wall is formed by a heat-removal plate (15) made of a thermally conducting material, separated from the said block (11) by the extension of the said hot exchanger (14).
20. System according to either of Claims 18 or 19, characterized in that it comprises, mounted securely to the said casing, a double-acting pressure oscillator in order to generate periodic pressure pulses alternating between compression and expansion, which occur in phase opposition at the ends of the said pulse tube (51) and of the said regenerating duct (56), respectively, away from the ends where they are in communication with each other.
21. System according to Claim 20, characterized in that the said pressure oscillator is fastened against a lid thereof also forming a heat-removal plate for the cooling block.
22. System according to one of Claims 17 to 21, characterized in that the said hot exchanger (14) is formed by a thermally conducting angle bracket overlapping a left lateral face and, partially, the left part of an upper face of the said block.
23. System according to Claim 19 combined with Claim 22, characterized in that the heat-removal plate (15) is mounted on the hot exchanger in the shape of an angle bracket (14) in its part partially overlapping the said upper face of the block (11).
24. System according to one of Claims 17 to 23, characterized in that the said cold exchanger (16) is formed by a thermally conducting angle bracket overlapping a right lateral face and, partially, the right part of a lower face of the said block (11).

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