EP0850386A1 - Indirect cooling system for an electrical device - Google Patents

Indirect cooling system for an electrical device

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Publication number
EP0850386A1
EP0850386A1 EP96934396A EP96934396A EP0850386A1 EP 0850386 A1 EP0850386 A1 EP 0850386A1 EP 96934396 A EP96934396 A EP 96934396A EP 96934396 A EP96934396 A EP 96934396A EP 0850386 A1 EP0850386 A1 EP 0850386A1
Authority
EP
European Patent Office
Prior art keywords
section
low
cooling
temperature
cooling device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96934396A
Other languages
German (de)
French (fr)
Inventor
Florian Steinmeyer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP0850386A1 publication Critical patent/EP0850386A1/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C3/00—Vessels not under pressure
    • F17C3/02—Vessels not under pressure with provision for thermal insulation
    • F17C3/08—Vessels not under pressure with provision for thermal insulation by vacuum spaces, e.g. Dewar flask
    • F17C3/085—Cryostats
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D19/00—Arrangement or mounting of refrigeration units with respect to devices or objects to be refrigerated, e.g. infrared detectors
    • F25D19/006—Thermal coupling structure or interface

Definitions

  • the invention relates to a device for the indirect cooling of an electrical device to be kept at low temperature, in particular superconducting device, which is located in an evacuable interior of a vacuum housing, which device contains at least one refrigeration machine part which has a machine section on the room temperature side and a machine section on the low-temperature side, which is arranged in an evacuable space, has - protrudes through an opening of the vacuum housing into its interior, is spring-loaded on the vacuum housing via spring elements and is fastened in a way that seals its opening, and - at its low-temperature end the electrical device is connected with good thermal conductivity.
  • a cooling device is e.g. from US 5 129 232 A.
  • Deep-freezing electrical especially superconducting devices such as the winding of a magnetic coil or a generator or like a superconducting cable requires cooling devices which ensure that the parts to be cooled are operated at the low operating temperature. Bath cooling, forced cooling or, in particular, indirect cooling are possible for the parts to be cooled.
  • Indirect cooling allows the construction of relatively small-volume, refrigerant-free cryostats without a coolant tank and also makes the user independent of the need to replenish a cryogenic liquid.
  • the required refrigeration can for example, from a generally two-stage cryocooler that often works according to the Gifford-McMahon principle. With a corresponding cryocooler, for example, the first stage at approximately 60 K can be loaded with typically 50 W and the second stage at 10 K with 1 W thermal power.
  • Indirect cooling can advantageously be provided for superconducting magnet systems in magnetic resonance imaging systems.
  • a corresponding cooling device should be designed in such a way that with the thermal coupling of its refrigerating machine or a refrigerating machine part to the super-conducting magnet system, vibrations are transmitted to the magnet system to the smallest possible extent.
  • All common refrigeration machines contain mechanically moving parts that cause considerable vibrations in the frequency range from 1 to a few 10 Hz.
  • the pressure vibrations of the working medium typically helium gas of approximately 20 bar, can also contribute to the vibrations. If these vibrations have an undamped effect on the magnet system, undesired eddy currents arise during operation of the magnet system, for example because a magnetic basic field with an induction of 1 T results. However, these eddy currents not only increase the heat load on the cooling device, but also disrupt the imaging system of the magnetic resonance imaging system.
  • a cooling device for a He-cooled superconducting magnet of a nuclear spin tomography system which can be found in EP 0 260 036 A, provides that the magnet and a radiation shield surrounding it are each thermally highly conductive via flexible connecting elements Material is coupled to parts of a chiller.
  • refrigeration machines are generally much higher in the case of magnets for nuclear spin tomography.
  • a cooling device for a superconducting magnet of a nuclear spin tomography system with corresponding vibration-damping thermal connecting elements between a refrigerator and a radiation shield or a superconducting magnet is also known from the US-A document mentioned at the beginning.
  • the refrigeration machine is supported here by spring elements on the vacuum housing enclosing the superconducting winding. Not only the inherent weight of the refrigeration machine has to be absorbed via these suspension elements, but also the pressure force of the external air pressure, which acts on a section of the refrigeration machine on the room temperature side.
  • Compressive force is caused by the fact that the section on the room temperature side is under the normal pressure of the surroundings of the vacuum housing of the superconducting winding, while the section on the low temperature side of the refrigerator is arranged in an evacuated housing unit which projects into the vacuum space of the vacuum housing of the superconducting magnet.
  • the suspension elements are therefore pressed together with a relatively large force and must therefore have an adapted large spring force.
  • the rigidity of the suspension is consequently correspondingly high, so that the vibration damping caused by the known suspension elements is accordingly limited.
  • the object of the present invention is to improve the cooling device with the features mentioned at the outset in such a way that the transmission of oscillations (vibrations) from its refrigeration machine or refrigeration machine parts to the electrical device to be cooled is further reduced.
  • this object is achieved in that the section of the refrigerating machine part on the room temperature side in an evacuable space of a housing unit rigidly connected to the vacuum housing is arranged.
  • FIG. 1 schematically shows a cooling device according to the invention
  • FIG. 2 shows this cooling device with a heat switch in the open state
  • FIG. 3 shows this cooling device with the heat switch in the closed state.
  • the cooling device according to the invention can be particularly advantageously provided for deep-freezing electrical devices which are sensitive to vibrations which are caused by the refrigeration machine part.
  • a corresponding device is, for example, the superconducting magnetic system of a system for magnetic resonance imaging. Self- the cooling device can also be used for other deep-freezing electrical devices.
  • FIG. 1 the part of a corresponding cooling device designed according to the invention is illustrated in section and generally designated 2. Parts of the cooling device, not shown in the figure and not explained in more detail in the following description, are generally known.
  • the device enables the formation of a refrigerant-free cryostat.
  • the cooling device 2 shown contains at least one refrigeration machine 3 with at least one refrigeration machine part 4, which can have two refrigeration stages 5 and 6.
  • the refrigerator 3 is a Gifford-McMahon type cryocooler. Other single- or multi-stage chiller types can also be used.
  • the refrigeration machine part 4 or, if appropriate, the complete refrigeration machine is composed of a machine section 4a located in a room temperature range RT, ie with the room temperature side machine section 4a, and one which comprises the two refrigeration levels 5 and 6, which extends into a low temperature range TT, and thus with the low temperature range 4 machine side.
  • the section 4b on the low-temperature side protrudes through an opening 7 of a vacuum housing 8 into which an interior space 9 which can be evacuated to a residual pressure pl of an insulating vacuum.
  • the opening 7 is so large that the low-temperature-side machine section 4b can move approximately vertically in its vertical direction.
  • the section 4b is thermally coupled to a device 10 to be cooled, for example to a superconducting magnet. Of this magnet surrounded by the insulating vacuum, only an upper part of a structure to be cooled, for example its housing, is indicated in the figure.
  • the low-temperature section 4b of the refrigeration machine part 4 is advantageously located in a separate housing unit 12, the interior 13 of which can be evacuated.
  • the low-temperature section 4b of the Refrigeration machine part 4 can be mounted in a separate lock which is vacuum-tight with respect to the interior 9 of the vacuum housing 8.
  • This sluice which can contain thin-walled VA pipes and the volume of which does not need to be much larger than that of the cold-temperature shield 4b, enables access to the interior 13 from the outside or from above.
  • connecting pieces 15 and 16 with good heat conductivity are provided on the outside of the housing unit 12 and heat contacts 17 and 18, on the inside, which are mechanically detachable.
  • These heat contacts can be formed, for example, with spring-loaded contact lamellae made of Cu, which may be gold-plated, silver-plated and / or coated with indium. They enable heat to be transferred from the respective cold stage of the low-temperature section 4b of the refrigerator part 4 to the thermal connecting pieces 15 and 16 via the wall of the housing unit 12.
  • a switchable heat contact in the radial direction is achieved in this way From the first or second cold stage 5 or 6 there is a warm contact to a radiation shield 20 or to the structure of the magnet 10 via the warm contacts 17 or 18, the thermal connecting pieces 15 or 16 and via flexible thermal To ensure links 21 and 22, respectively.
  • the flexible thermal connecting links can be, for example, copper strands or bands, via which vibrations of the cold machine part 4 are hardly transmitted.
  • the housing unit 12 acting as a lock is at a residual pressure p2 evacuated. It can be ventilated or evacuated for a change of the refrigeration machine part 4 at an inlet 24 of the low-temperature housing unit 12.
  • the room temperature-side section 4a is housed in a separate, evacuable housing unit 26.
  • This housing unit encloses the section 4a of the refrigeration machine part 4 on the room temperature side and is rigidly attached to the outside of the vacuum housing 8 in a sealed manner. Its interior 27 can thus be separated from the insulation vacuum of the magnet 10 and the low-temperature side machine section 4b at an inlet 28 to a suction pressure p3 or vented.
  • the refrigerating machine part 4 is not only pressed against the vacuum housing 8 not only with its weight force Gk of, for example, about 200 N, but also with the force Lk of the external air pressure.
  • Gk weight force
  • Lk force of the external air pressure.
  • This force Lk is absorbed in known cooling devices (cf. US Pat. No. 5,129,232 A) by a correspondingly hard suspension, which is intended to dampen the transmission of vibrations from the cooling machine part to the device 10 to be cooled.
  • the cooling device 2 advantageously only needs to be designed in such a way that practically only the weight Gk of the cooling machine part 4 is absorbed.
  • the shown, correspondingly spring-loaded wear of the refrigeration machine part comprises suspension elements 30, to which elastic damper elements 31 can be arranged in parallel.
  • the elements 30 and 31 are clamped between the vacuum housing 8 and support projections 32 oriented parallel thereto, which are rigid with the cold machine part 4, in particular with the connection area of the section 4a on the room temperature side and the section 4b on the low temperature side. are connected.
  • the support extensions 32 and the elements 30 and 31 not only provide support or, if appropriate, a corresponding suspension, but also the sealing of the interior 9 of the vacuum housing 8 in the region of its opening 7.
  • the support of the cooling machine part 4 springs through to a fixed mechanical stop 33 due to the negative pressure effect on a section on the low-temperature side.
  • the vibration damping is therefore only achieved as soon as the interior 27 of the housing unit 26 is pumped down to an operating pressure p3 of, for example, less than 100 mbar. Typical pressure values are about 10 mbar.
  • Air pressure force Lk reduced to a force of about 20 N.
  • the refrigeration machine part 4 is carried by the spring elements 30 and 31.
  • the corresponding spring constant can thereby be reduced to approximately 1/10 of the value that would be necessary for vibration damping without pumping out.
  • the correspondingly soft suspension allows, in many applications, the cold machine part 4 to be mounted directly on a housing part of a device to be frozen, like a magnet, without the need for further mechanical and heat-conducting connecting elements or links.
  • In the figure are still flexible, vacuum-tight due to the interior Connection space 35 for the refrigeration machine section 4a, for example for helium and electrical connection lines, is shown in the interior space 27 of the housing unit 26 on the room temperature side.
  • the cooling capacity of the second stage 6 of the refrigeration machine part 4, to which the device to be cooled, for example the magnet 10, is thermally coupled, is about 1/5 of the performance of the first stage 5 in a conventional Gifford-McMahon refrigeration machine 3.
  • the heat capacity is one
  • super-conductive magnets amount to at least 2/3 of the thermal mass to be cooled. In order to cool a superconducting magnet from room temperature to operating temperature only with the aid of a refrigeration machine, it is therefore advantageous to use the comparatively high refrigeration capacity of the first stage 5 of the refrigeration machine to precool the magnet.
  • FIGS. 2 and 3 An exemplary embodiment of corresponding releasable heat contacts can be seen in FIGS. 2 and 3, FIG. 2 illustrating the closed state of the heat contacts and FIG. 3 the opened state.
  • the heat contact shown in the figures and generally designated 40 is formed by at least one thermally well-conductive contact plate 41 which is between a well thermally conductive holding structure 43 rigidly connected to the device 10 to be cooled and at least largely at the temperature of the first Part of the low-temperature side Section 4b of the refrigerator is located.
  • This part of the refrigeration machine section 4b can be formed, for example, by the thermal connecting piece 15. Since this connection piece is rigidly connected to the cold machine section 4b or the housing unit 12 arranged around it, the deflection of the resilient elements 30 and 31 follows accordingly. During the cooling process from the room temperature, the interior 27 of the external housing unit 26 initially remains ventilated.
  • the cold machine part 4 is pressed by the external air pressure with the force Lk against the soft wear over the suspension elements 30 and 31 in the direction of the magnet 10 until the warm contact 40 of the first cold stage 5 hits its mechanical stop (see Figure 2).
  • This stop is formed by the contact plates 41 on the holding structure 43 rigidly connected to the magnet 10.
  • the refrigeration machine part 4 Due to an evacuation of the interior 27 to a pressure p3 after the pre-cooling of the magnet to approximately the temperature of the first cooling stage 5, the refrigeration machine part 4 is relieved of the force Lk, so that the suspension elements 30 and 31 expand accordingly with the only existing weight force Gk .
  • the connecting piece 15, which is rigidly connected to the refrigeration machine part 4 is raised by an amount corresponding to this stroke from the plates 41, so that the heat contact 40 can now be opened.
  • FIGS. 1 to 3 a support of a refrigeration machine or a part of it sprung according to the invention is illustrated. A corresponding suspension via suspension elements, which are to be relieved of the air pressure force Lk acting on a machine section on the room temperature side, is just as possible.

Abstract

The system (2) for indirectly cooling a device (10) in a vacuum housing (8), especially a superconducting device, contains at least one refrigerating machine component (4) consisting of sections (4a and 4b) on the ambient and low temperature sides, projects into the vacuum chamber (8), is secured thereto via sprung components (30) and has a heat-conductive connection to the device (10) to be cooled at its low-temperature end. In order to reduce the vibrations transmitted to the device (10), the ambient temperature section (4a) of the refrigerating machine component (4) is to be fitted in an evacuatable compartment (27) of a housing unit (26) rigidly secured to the vacuum housing (8).

Description

Beschreibungdescription
Vorrichtung zur indirekten Kühlung einer elektriεchen Ein¬ richtungDevice for indirect cooling of an electrical device
Die Erfindung bezieht sich auf eine Vorrichtung zur indirek¬ ten Kühlung einer elektrischen, auf Tieftemperatur zu halten¬ den, insbesondere supraleitenden Einrichtung, die sich in einem evakuierbaren Innenraum eines Vakuumgehäuses befindet, welche Vorrichtung wenigstens einen Kältemaschinenteil ent¬ hält, der einen raumtemperaturseitigen Maschinenabschnitt und einen tieftemperaturseitigen Maschinenabschnitt, welcher in einem evakuierbaren Raumbereich angeordnet iεt, aufweist, - durch eine Öffnung des Vakuumgehäuεes beweglich in dessen Innenraum hineinragt, über Federungselemente an dem Vakuumgehäuse federnd und in einer dessen Öffnung abdichtenden Weiεe befestigt ist sowie - an seinem auf Tieftemperatur liegenden Ende mit der elek¬ trischen Einrichtung gut wärmeleitend verbunden ist. Eine derartige Kühlvorrichtung ist z.B. aus der US 5 129 232 A zu entnehmen.The invention relates to a device for the indirect cooling of an electrical device to be kept at low temperature, in particular superconducting device, which is located in an evacuable interior of a vacuum housing, which device contains at least one refrigeration machine part which has a machine section on the room temperature side and a machine section on the low-temperature side, which is arranged in an evacuable space, has - protrudes through an opening of the vacuum housing into its interior, is spring-loaded on the vacuum housing via spring elements and is fastened in a way that seals its opening, and - at its low-temperature end the electrical device is connected with good thermal conductivity. Such a cooling device is e.g. from US 5 129 232 A.
Tiefzukühlende elektrische, insbesondere supraleitende Ein¬ richtungen wie z.B. die Wicklung einer Magnetspule oder eines Generators oder wie ein supraleitendeε Kabel erfordern Kühl¬ vorrichtungen, die einen Betrieb der zu kühlenden Teile auf der tiefen Betriebεtemperatur gewährleiεten. Dabei kommt für dieεe zu kühlenden Teile eine Badkühlung, eine forcierte Küh¬ lung oder insbesondere auch eine indirekte Kühlung in Frage.Deep-freezing electrical, especially superconducting devices such as the winding of a magnetic coil or a generator or like a superconducting cable requires cooling devices which ensure that the parts to be cooled are operated at the low operating temperature. Bath cooling, forced cooling or, in particular, indirect cooling are possible for the parts to be cooled.
Eine indirekte Kühlung erlaubt den Bau verhältnismäßig klein- volumiger, kältemittelfreier Kryostate ohne Kühlmittelbehäl- ter und macht zudem den Anwender unabhängig vom Nachschub einer Kryoflüssigkeit . Die erforderliche Kälteleiεtung läßt sich z.B. von einem im allgemeinen zweistufig ausgebildeten Kryokühler, der häufig nach dem Gifford-McMahon-Prinzip ar¬ beitet, aufbringen. Bei einem entsprechenden Kryokühler kön¬ nen beispielsweise die erste Stufe bei ca. 60 K mit typi- scherweise 50 W und die zweite Stufe bei 10 K mit 1 W thermi¬ scher Leistung belaεtet werden.Indirect cooling allows the construction of relatively small-volume, refrigerant-free cryostats without a coolant tank and also makes the user independent of the need to replenish a cryogenic liquid. The required refrigeration can for example, from a generally two-stage cryocooler that often works according to the Gifford-McMahon principle. With a corresponding cryocooler, for example, the first stage at approximately 60 K can be loaded with typically 50 W and the second stage at 10 K with 1 W thermal power.
Eine indirekte Kühlung läßt sich vorteilhaft für supraleiten¬ de Magnetsysteme von Anlagen zur Kernspintomographie vorse- hen. Dabei sollte eine entsprechende Kühlvorrichtung so aus¬ gelegt werden, daß mit der thermischen Ankopplung ihrer Käl¬ temaschine oder eines Kältemaschinenteils an das εupralei- tende Magnetεystem in möglichεt geringem Umfang Schwingungen auf das Magnetsyεtem übertragen werden. Alle gebräuchlichen Kältemaεchinen enthalten nämlich mechanisch bewegte Teile, die im Frequenzbereich von 1 bis einige 10 Hz beträchtliche Vibrationen verurεachen. Auch die Druckschwingungen deε Ar¬ beitsmediums, typischerweise Heliumgas von ca. 20 bar, können zu den Vibrationen beitragen. Wirken diese Vibrationen unge- dämpft auf das Magnetsyεtem ein, dann entεtehen beim Betrieb deε Magnetεystems, daε beispielεweiεe ein magnetisches Grund¬ feld mit einer Induktion von 1 T hervorruft, unerwünschte Wirbelεtröme . Dieεe Wirbelströme erhöhen aber nicht nur die Wärmelast auf die Kühlvorrichtung, sondern stören auch daε bildgebende System der Kernspintomographie-Anlage.Indirect cooling can advantageously be provided for superconducting magnet systems in magnetic resonance imaging systems. A corresponding cooling device should be designed in such a way that with the thermal coupling of its refrigerating machine or a refrigerating machine part to the super-conducting magnet system, vibrations are transmitted to the magnet system to the smallest possible extent. All common refrigeration machines contain mechanically moving parts that cause considerable vibrations in the frequency range from 1 to a few 10 Hz. The pressure vibrations of the working medium, typically helium gas of approximately 20 bar, can also contribute to the vibrations. If these vibrations have an undamped effect on the magnet system, undesired eddy currents arise during operation of the magnet system, for example because a magnetic basic field with an induction of 1 T results. However, these eddy currents not only increase the heat load on the cooling device, but also disrupt the imaging system of the magnetic resonance imaging system.
Zur Lösung von Problemen hinsichtlich einer Schwingungsüber¬ tragung iεt bei einer auε der EP 0 260 036 A zu entnehmenden Kühlvorrichtung für einen He-gekühlten Supraleitungsmagneten einer Kernεpintomographie-Anlage vorgesehen, daß der Magnet und ein ihn umgebender Strahlungsschild jeweils über flexible Verbindungεglieder auε thermisch gut leitendem Material an Teile einer Kältemaschine angekoppelt sind. Die Anforderungen an die Dämpfungεeigenεchaften einer derartigen, auch mecha- niεch wirkenden Kopplung zwiεchen einem Magneten und einer Kältemaεchine εind jedoch im Falle von Magneten zur Kernεpin- tomographie im allgemeinen weitaus höher.In order to solve problems with regard to vibration transmission, a cooling device for a He-cooled superconducting magnet of a nuclear spin tomography system, which can be found in EP 0 260 036 A, provides that the magnet and a radiation shield surrounding it are each thermally highly conductive via flexible connecting elements Material is coupled to parts of a chiller. The requirements for the damping properties of such a coupling, which also acts mechanically, between a magnet and one However, refrigeration machines are generally much higher in the case of magnets for nuclear spin tomography.
Aus der eingangε genannten US-A-Schrift iεt ferner eine Kühl- Vorrichtung für einen εupraleitenden Magneten einer Kernεpin- tomographie-Anlage mit entsprechenden schwingungsdämpfenden thermischen Verbindungsgliedern zwischen einer Kältemaschine und einem Strahlungεεchild bzw. einem supraleitenden Magneten bekannt . Zur weiteren Verbesεerung der Schwingungsdämpfung stützt εich hier die Kältemaεchine über Federungselemente an dem die εupraleitende Wicklung umεchließenden Vakuumgehäuse ab. Ober diese Federungselemente muß nicht nur das Eigenge¬ wicht der Kältemaschine aufgefangen werden, sondern auch die Druckkraft des äußeren Luftdruckes, der auf einen raumtempe- raturseitigen Abεchnitt der Kältemaεchine einwirkt. DieεeA cooling device for a superconducting magnet of a nuclear spin tomography system with corresponding vibration-damping thermal connecting elements between a refrigerator and a radiation shield or a superconducting magnet is also known from the US-A document mentioned at the beginning. To further improve the vibration damping, the refrigeration machine is supported here by spring elements on the vacuum housing enclosing the superconducting winding. Not only the inherent weight of the refrigeration machine has to be absorbed via these suspension elements, but also the pressure force of the external air pressure, which acts on a section of the refrigeration machine on the room temperature side. This
Druckkraft iεt dadurch hervorgerufen, daß der raumtemperatur¬ seitige Abschnitt εich unter dem Normaldruck der Umgebung des Vakuumgehäuseε der εupraleitenden Wicklung befindet, während der tieftemperaturseitige Abschnitt der Kältemaschine in einer evakuierten Gehäuseeinheit angeordnet iεt, die in den Vakuumraum deε Vakuumgehäuεeε deε εupraleitenden Magneten hineinragt . Die Federungselemente werden deshalb mit einer verhältnismäßig großen Kraft zusammengedrückt und müsεen so¬ mit eine angepaßte große Federkraft aufweisen. Die Steifig- keit der Federung ist folglich entsprechend groß, so daß die von den bekannten Federungεelementen bewirkte Schwingungε- dämpfung dementεprechend begrenzt iεt.Compressive force is caused by the fact that the section on the room temperature side is under the normal pressure of the surroundings of the vacuum housing of the superconducting winding, while the section on the low temperature side of the refrigerator is arranged in an evacuated housing unit which projects into the vacuum space of the vacuum housing of the superconducting magnet. The suspension elements are therefore pressed together with a relatively large force and must therefore have an adapted large spring force. The rigidity of the suspension is consequently correspondingly high, so that the vibration damping caused by the known suspension elements is accordingly limited.
Aufgabe der vorliegenden Erfindung iεt eε, die Kühlvorrich- tung mit den eingangε genannten Merkmalen dahingehend zu ver¬ bessern, daß die Übertragung von Schwingungen (Vibrationen) von ihrer Kältemaεchine oder Kältemaschinenteilen auf die zu kühlende elektrische Einrichtung weiter vermindert wird.The object of the present invention is to improve the cooling device with the features mentioned at the outset in such a way that the transmission of oscillations (vibrations) from its refrigeration machine or refrigeration machine parts to the electrical device to be cooled is further reduced.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß der raumtemperaturseitige Abschnitt des Kältemaεchinenteilε in einem evakuierbaren Raum einer mit dem Vakuumgehäuεe starr verbundenen Gehäuseeinheit angeordnet ist.According to the invention, this object is achieved in that the section of the refrigerating machine part on the room temperature side in an evacuable space of a housing unit rigidly connected to the vacuum housing is arranged.
Die mit dieser Auεgeεtaltung der Kühlvorrichtung verbundenen Vorteile sind insbeεondere darin zu εehen, daß mit der Eva¬ kuierung deε den raumtemperaturεeitigen Abschnitt der Kälte¬ maschine umgebenden Raumes die Federungselemente von der Kraft des äußeren Luftdruckes auf den Kältemaschinenteil ent¬ lastet werden. Die Federkonstante der mit den Federungεele- menten bewirkten Federung kann εomit auf einen Bruchteil deε Werteε reduziert werden, der ohne daε Evakuieren für eine Schwingungεdämpfung nötig wäre. Damit geht eine entεprechende Erhöhung der Vibrationsdämpfung einher.The advantages associated with this configuration of the cooling device can be seen in particular in that, with the evacuation of the space surrounding the section of the refrigeration machine on the room temperature side, the spring elements are relieved of the force of the external air pressure on the refrigerator part. The spring constant of the suspension effected with the suspension elements can thus be reduced to a fraction of the value that would be necessary for vibration damping without the evacuation. This is accompanied by a corresponding increase in vibration damping.
Vorteilhafte Ausgestaltungen der erfindungsgemäßen Kühlvor¬ richtung sind den Unteransprüchen zu entnehmen.Advantageous refinements of the cooling device according to the invention can be found in the subclaims.
Zur weiteren Erläuterung der Erfindung wird nachfolgend auf die Zeichnung Bezug genommen. Es zeigen jeweils εchematisch Figur 1 eine erfindungεgemäße Kühlvorrichtung,To further explain the invention, reference is made below to the drawing. 1 schematically shows a cooling device according to the invention,
Figur 2 dieεe Kühlvorrichtung mit einem Wärmeεchalter im of¬ fenen Zuεtand und Figur 3 diese Kühlvorrichtung mit dem Wärmeschalter im ge- εchloεsenen Zustand.2 shows this cooling device with a heat switch in the open state and FIG. 3 shows this cooling device with the heat switch in the closed state.
Dabei εind in den Figuren εich entsprechende Teile mit den¬ selben Bezugszeichen versehen.Corresponding parts are given the same reference numerals in the figures.
Die erfindungεgemäße Kühlvorrichtung kann wegen der εchwin- gungsgedämpften Abstützung oder Aufhängung ihrer Kältema¬ schine oder eines Kältemaschinenteilε besonderε vorteilhaft für tiefzukühlende elektriεche Einrichtungen vorgeεehen wer¬ den, die empfindlich bezüglich Vibrationen sind, welche von dem Kältemaschinenteil hervorgerufen werden. Eine entεpre- chende Einrichtung iεt beiεpielεweiεe daε supraleitende Ma¬ gnetsyεtem einer Anlage zur Kernspintomographie. Selbεtver- ständlich ist die Kühlvorrichtung auch für andere tiefzuküh¬ lende elektrische Einrichtungen anwendbar.Because of the vibration-damped support or suspension of its refrigeration machine or a refrigeration machine part, the cooling device according to the invention can be particularly advantageously provided for deep-freezing electrical devices which are sensitive to vibrations which are caused by the refrigeration machine part. A corresponding device is, for example, the superconducting magnetic system of a system for magnetic resonance imaging. Self- the cooling device can also be used for other deep-freezing electrical devices.
In Figur 1 ist der erfindungsgemaß gestaltete Teil einer ent- sprechenden Kühlvorrichtung im Schnitt veranschaulicht und allgemein mit 2 bezeichnet. In der Figur nicht dargestellte und in der nachfolgenden Beschreibung nicht näher erläuterte Teile der Kühlvorrichtung εind allgemein bekannt. Die Vor¬ richtung ermöglicht die Auεbildung eineε kältemittelfreien Kryostaten.In FIG. 1, the part of a corresponding cooling device designed according to the invention is illustrated in section and generally designated 2. Parts of the cooling device, not shown in the figure and not explained in more detail in the following description, are generally known. The device enables the formation of a refrigerant-free cryostat.
Die gezeigte Kühlvorrichtung 2 enthält wenigstenε eine Kälte¬ maschine 3 mit mindeεtenε einem Kältemaεchinenteil 4, der zwei Kältestufen 5 und 6 aufweisen kann. Beiεpielεweiεe han- delt eε sich bei der Kältemaschine 3 um einen Kryokühler von Gifford-McMahon-Typ. Ebensogut sind auch andere, ein- oder mehrstufige Kältemaschinentypen einsetzbar. Der Kältemaschi¬ nenteil 4 oder gegebenenfalls die komplette Kältemaschine εetzt sich auε einem in einem Raumtemperaturbereich RT be- findlichen, εomit räumtemperaturεeitigen Maεchinenabschnitt 4a und einem die zwei Kälteεtufen 5 und 6 umfaεεenden, εich biε in einen Tieftemperaturbereich TT erεtreckenden, εomit tieftemperaturεeitigen Maεchinenabεchnitt 4b zusammen. Der tieftemperaturεeitige Abεchnitt 4b ragt durch eine Öffnung 7 eineε Vakuumgehäuεeε 8 in deεεen auf einen Reεtdruck pl eineε Iεoliervakuums evakuierbaren Innenraum 9 hinein. Die Öffnung 7 iεt dabei εo groß bemeεsen, daß εich der tieftempe¬ raturεeitige Maεchinenabεchnitt 4b in ihr in vertikaler Richtung etwaε verεchiebbar bewegen kann. An dem tieftempera- turεeitigen Ende der zweiten Kältestufe 6 ist der Abεchnitt 4b thermiεch an eine zu kühlende Einrichtung 10, beiεpielε¬ weiεe an einen εupraleitenden Magneten, angekoppelt. Von die¬ sem von dem Isoliervakuum umgebenen Magneten ist in der Figur nur ein oberes Teilstück einer zu kühlenden Struktur, bei- εpielεweiεe seines Gehäuεeε, angedeutet. Vorteilhaft befindet sich der tieftemperaturseitige Abschnitt 4b des Kältemaschmenteilε 4 in einer eigenen Gehauseeinheit 12, deren Innenraum 13 evakuierbar lεt . Um nicht das gesamte Vakuumsyεtem deε Vakuumgehäuεeε 8 auf den Normaldruck pO der Umgebung der Kühlvorrichtung 2 belüften und den tiefzuküh¬ lenden Magneten 10 in einer langwierigen Prozedur von bei- εpielsweise während einer Woche aufwärmen und wieder abkühlen zu müssen, kann so der tieftemperaturseitige Abschnitt 4b des Kältemaschmenteils 4 in einer separaten, gegenüber dem In- nenraum 9 deε Vakuumgehäuεes 8 vakuumdichten Schleuse mon¬ tiert sein. Dieεe Schleuεe, die dünnwandige VA-Rohre enthal¬ ten kann und deren Volumen nicht viel großer als das des Käl- temaεchmenabεchmtts 4b zu sein braucht, ermöglicht einen Zugang zu dem Innenraum 13 von außen bzw. oben. Im Bereich der Position der ersten und zweiten Kältestufe 5 bzw. 6 sind an der Außenseite der Gehäuseeinheit 12 gut wärmeleitende Verbindungsstücke 15 bzw. 16 und auf der Innenseite mecha- niεch lösbare Warmekontakte 17 bzw. 18 vorgesehen. Diese War- mekontakte können z.B. mit gefederten Kontaktlamellen aus Cu, die gegebenenfalls vergoldet, versilbert und/oder mit Indium beεchichtet sein können, gebildet werden. Sie ermöglichen einen Wärmeübergang von der jeweiligen Kältestufe des tief- temperaturεeitigen Abεchnittes 4b des Kältemaschinenteils 4 zu den thermischen Verbindungsstücken 15 bzw. 16 über die Wand der Gehauseeinheit 12. Bei der in der Figur veranschau¬ lichten Ausführungsform wird so ein schaltbarer Warmekontakt in radialer Richtung verwirklicht Von der ersten bzw. zwei¬ ten Kälteεtufe 5 bzw. 6 lεt εo ein Warmekontakt zu einem Strahlungεεchild 20 bzw. zu der Struktur des Magneten 10 über die Warmekontakte 17 bzw. 18, die thermiεchen Verbindungs¬ stucke 15 bzw. 16 sowie über flexible thermische Verbindungs¬ glieder 21 bzw. 22 zu gewährleisten. Die flexiblen thermi¬ schen Verbindungsglieder können beispielsweise Kupferlitzen oder -bander sein, über die Vibrationen des Kaltemaεchinen- teils 4 kaum übertragen werden. Im Betriebszustand ist die alε Schleuεe wirkende Gehäuseeinheit 12 auf einen Restdruck p2 evakuiert . Sie kann für einen Wechsel deε Kältemaεchinen- teils 4 an einem Einlaß 24 der tieftemperaturseitigen Gehäu¬ seeinheit 12 belüftet bzw. evakuiert werden.The cooling device 2 shown contains at least one refrigeration machine 3 with at least one refrigeration machine part 4, which can have two refrigeration stages 5 and 6. For example, the refrigerator 3 is a Gifford-McMahon type cryocooler. Other single- or multi-stage chiller types can also be used. The refrigeration machine part 4 or, if appropriate, the complete refrigeration machine is composed of a machine section 4a located in a room temperature range RT, ie with the room temperature side machine section 4a, and one which comprises the two refrigeration levels 5 and 6, which extends into a low temperature range TT, and thus with the low temperature range 4 machine side. The section 4b on the low-temperature side protrudes through an opening 7 of a vacuum housing 8 into which an interior space 9 which can be evacuated to a residual pressure pl of an insulating vacuum. The opening 7 is so large that the low-temperature-side machine section 4b can move approximately vertically in its vertical direction. At the low-temperature end of the second cooling stage 6, the section 4b is thermally coupled to a device 10 to be cooled, for example to a superconducting magnet. Of this magnet surrounded by the insulating vacuum, only an upper part of a structure to be cooled, for example its housing, is indicated in the figure. The low-temperature section 4b of the refrigeration machine part 4 is advantageously located in a separate housing unit 12, the interior 13 of which can be evacuated. In order not to have to ventilate the entire vacuum system of the vacuum housing 8 to the normal pressure pO of the surroundings of the cooling device 2 and to have to warm and cool the magnet 10 to be frozen in a lengthy procedure, for example during a week, the low-temperature section 4b of the Refrigeration machine part 4 can be mounted in a separate lock which is vacuum-tight with respect to the interior 9 of the vacuum housing 8. This sluice, which can contain thin-walled VA pipes and the volume of which does not need to be much larger than that of the cold-temperature shield 4b, enables access to the interior 13 from the outside or from above. In the area of the position of the first and second cooling stages 5 and 6, connecting pieces 15 and 16 with good heat conductivity are provided on the outside of the housing unit 12 and heat contacts 17 and 18, on the inside, which are mechanically detachable. These heat contacts can be formed, for example, with spring-loaded contact lamellae made of Cu, which may be gold-plated, silver-plated and / or coated with indium. They enable heat to be transferred from the respective cold stage of the low-temperature section 4b of the refrigerator part 4 to the thermal connecting pieces 15 and 16 via the wall of the housing unit 12. In the embodiment illustrated in the figure, a switchable heat contact in the radial direction is achieved in this way From the first or second cold stage 5 or 6 there is a warm contact to a radiation shield 20 or to the structure of the magnet 10 via the warm contacts 17 or 18, the thermal connecting pieces 15 or 16 and via flexible thermal To ensure links 21 and 22, respectively. The flexible thermal connecting links can be, for example, copper strands or bands, via which vibrations of the cold machine part 4 are hardly transmitted. In the operating state, the housing unit 12 acting as a lock is at a residual pressure p2 evacuated. It can be ventilated or evacuated for a change of the refrigeration machine part 4 at an inlet 24 of the low-temperature housing unit 12.
Selbstverständlich sind auch Auεführungεformen von Kältema¬ schinen einsetzbar, deren tieftemperaturseitiger Abεchnitt 4b nicht in einem eigenen evakuierbaren Raum 13 einer εpeziellen Gehäuεeeinheit angeordnet ist, sondern direkt in den Innen¬ raum 9 des Vakuumgehäuseε 8 hineinragt. Auf jedem Fall εind die Öffnung 7 und der gegebenenfallε vorhandene evakuierbare Raum 13 über eine Abεtützung oder Aufhängung deε Kältema- schinenteilε 4 vakummfest abgedichtet.Of course, it is also possible to use embodiments of refrigeration machines whose section 4b on the low-temperature side is not arranged in a separate evacuable space 13 of a special housing unit, but projects directly into the interior 9 of the vacuum housing 8. In any case, the opening 7 and the optionally available evacuable space 13 are sealed in a vacuum-tight manner by means of a support or suspension of the refrigerator part 4.
Um den raumtemperaturseitigen Abschnitt 4a des Kältemaschi- nenteilε 4 und damit die Abstützung oder Aufhängung dieses Maschinenteils von dem äußeren Luftdruck zu entlasten, iεt gemäß der Erfindung vorgeεehen, daß der raumtemperaturεeitige Abschnitt 4a in einer εeparaten, evakuierbaren Gehäuεeeinheit 26 untergebracht iεt. Diese Gehäuseeinheit umεchließt den räumtemperaturεeitigen Abεchnitt 4a deε Kältemaεchinenteilε 4 und ist starr auf der Außenseite deε Vakuumgehäuεes 8 in ab¬ gedichteter Weiεe befeεtigt. Ihr Innenraum 27 kann εo ge¬ trennt von dem Isolationsvakuum des Magneten 10 und des tieftemperaturεeitigen Maεchinenabεchnittε 4b an einem Einlaß 28 auf einen Reεtdruck p3 evakuiert bzw. belüftet werden. Im belüfteten Zuεtand wird nämlich der Kältemaεchinenteil 4 nicht nur mit εeiner Gewichtεkraft Gk von beiεpielsweiεe etwa 200 N, εondern auch mit der Kraft Lk deε äußeren Luftdruckes gegen das Vakuumgehäuse 8 gedrückt. Das bedeutet, daß bei einem Durchmesser des Kältemaschinenteils 4 von etwa 160 mm eine zusätzliche Kraft Lk von etwa 2 kN, also etwa dem lOfachen der Gewichtskraft Gk, auftritt. Diese Kraft Lk wird in bekannten Kühlvorrichtungen (vgl. die US 5 129 232 A) durch eine entsprechend harte Federung aufgenommen, die gleichzeitig die Übertragung von Vibrationen deε Kältemaεchi¬ nenteilε auf die zu kühlende Einrichtung 10 dämpfen soll. Bei der erfindungsgemäßen KühlVorrichtung 2 braucht die Federung vorteilhaft lediglich so ausgelegt zu werden, daß praktiεch nur die Gewichtskraft Gk des Kältemaschmenteilε 4 aufgenom¬ men wird. Die gezeigte, entεprechend gefederte Abεtutzung des Kältemaschmenteilε umfaßt hierzu Federungselemente 30, zu denen parallel elastiεche Dampferelemente 31 angeordnet sein können. Die Elemente 30 und 31 sind dabei zwischen dem Va¬ kuumgehäuse 8 und parallel dazu ausgerichteten Abstützungs- fortsätzen 32 eingespannt, die εtarr mit dem Kaltemaschinen- teil 4, insbesondere mit dem Verbindungsbereich des raum- temperaturεeitigen Abεchnittes 4a und des tieftemperatursei- tigen Abεchnitteε 4b, verbunden sind. Über die Abstützungε- fortεätze 32 und die Elemente 30 und 31 erfolgt nicht nur die Abstutzung oder gegebenenfalls eine entsprechende Aufhängung, sondern auch die Abdichtung deε Innenraums 9 des Va- kuumgehauεeε 8 im Bereich seiner Öffnung 7.In order to relieve the ambient temperature-side section 4a of the refrigeration machine part 4 and thus the support or suspension of this machine part from the external air pressure, it is provided according to the invention that the room temperature-side section 4a is housed in a separate, evacuable housing unit 26. This housing unit encloses the section 4a of the refrigeration machine part 4 on the room temperature side and is rigidly attached to the outside of the vacuum housing 8 in a sealed manner. Its interior 27 can thus be separated from the insulation vacuum of the magnet 10 and the low-temperature side machine section 4b at an inlet 28 to a suction pressure p3 or vented. In the ventilated state, the refrigerating machine part 4 is not only pressed against the vacuum housing 8 not only with its weight force Gk of, for example, about 200 N, but also with the force Lk of the external air pressure. This means that with a diameter of the refrigerator part 4 of approximately 160 mm, an additional force Lk of approximately 2 kN, ie approximately 10 times the weight Gk, occurs. This force Lk is absorbed in known cooling devices (cf. US Pat. No. 5,129,232 A) by a correspondingly hard suspension, which is intended to dampen the transmission of vibrations from the cooling machine part to the device 10 to be cooled. at The cooling device 2 according to the invention advantageously only needs to be designed in such a way that practically only the weight Gk of the cooling machine part 4 is absorbed. For this purpose, the shown, correspondingly spring-loaded wear of the refrigeration machine part comprises suspension elements 30, to which elastic damper elements 31 can be arranged in parallel. The elements 30 and 31 are clamped between the vacuum housing 8 and support projections 32 oriented parallel thereto, which are rigid with the cold machine part 4, in particular with the connection area of the section 4a on the room temperature side and the section 4b on the low temperature side. are connected. The support extensions 32 and the elements 30 and 31 not only provide support or, if appropriate, a corresponding suspension, but also the sealing of the interior 9 of the vacuum housing 8 in the region of its opening 7.
Im belüfteten Zustand der Gehauseeinheit 26 federt die Ab¬ Stützung des Kältemaschmenteilε 4 aufgrund der Unterdruck- emwirkung auf εeinen tieftemperaturεeitigen Abεchnitt biε auf einen festen mechanischen Anschlag 33 durch. Die Vibra- tionεdämpmfung wird alεo erst erreicht, sobald der Innenraum 27 der Gehauseeinheit 26 auf einen Betriebsdruck p3 von bei¬ spielweise unter 100 mbar abgepumpt wird. Tpyische Druck- werte sind etwa 10 mbar. Durch die Evakuierung wird dieIn the ventilated state of the housing unit 26, the support of the cooling machine part 4 springs through to a fixed mechanical stop 33 due to the negative pressure effect on a section on the low-temperature side. The vibration damping is therefore only achieved as soon as the interior 27 of the housing unit 26 is pumped down to an operating pressure p3 of, for example, less than 100 mbar. Typical pressure values are about 10 mbar. The evacuation will
Luftdruckkraft Lk auf eine Reεtkraft von etwa 20 N reduziert. In dieεem Zuεtand wird der Kältemaschmenteil 4 von der Fede¬ rung der Elemente 30 und 31 getragen. Die entsprechende Fe¬ derkonstante kann dadurch auf etwa 1/10 des Wertes reduziert werden, der ohne ein Abpumpen für eine Schwingungsdampfung nötig wäre. Die entsprechend weiche Aufhangung erlaubt in vielen Anwendungen eine Montage deε Kaltemaschmenteils 4 di¬ rekt auf einem Gehauεeteil einer tiefzukühlenden Einrichtung wie eineε Magneten, ohne daß weitere mechanische und gut wär- meleitende Verbindungselemente oder -glieder notig waren. In der Figur sind noch flexible, sich vakuumdicht durch den In- nenraum 27 der raumtemperaturseitigen Gehäuεeeinheit 26 er¬ streckende Anschlußleitungen 35 für den raumtemperaturseiti¬ gen Kältemaschinenabschnitt 4a, beispielswieεe für Helium und elektriεche Verbindungεleitungen, angedeutet.Air pressure force Lk reduced to a force of about 20 N. In this state, the refrigeration machine part 4 is carried by the spring elements 30 and 31. The corresponding spring constant can thereby be reduced to approximately 1/10 of the value that would be necessary for vibration damping without pumping out. The correspondingly soft suspension allows, in many applications, the cold machine part 4 to be mounted directly on a housing part of a device to be frozen, like a magnet, without the need for further mechanical and heat-conducting connecting elements or links. In the figure are still flexible, vacuum-tight due to the interior Connection space 35 for the refrigeration machine section 4a, for example for helium and electrical connection lines, is shown in the interior space 27 of the housing unit 26 on the room temperature side.
Die Kälteleistung der zweiten Stufe 6 des Kältemaεchinenteils 4, an die die zu kühlende Einrichtung, beispielsweiεe der Magnet 10, thermiεch angekoppelt iεt, beträgt bei einer gebräuchlichen Gifford-McMahon-Kältemaεchine 3 etwa 1/5 der Leiεtung der erεten Stufe 5. Die Wärmekapazität eineε εupra¬ leitenden Magneten beträgt allerdingε in einer typiεchen Auεlegung mindestens 2/3 zur abzukühlenden thermischen Masεe bei. Um einen εupraleitenden Magneten allein mit Hilfe einer Kältemaεchine von Raumtemperatur biε auf Betriebεtemperatur abzukühlen, iεt es deshalb vorteilhaft, die vergleichsweiεe hohe Kälteleiεtung der erεten Stufe 5 der Kältemaεchine zum Vorkühlen deε Magneten zu nutzen. Daε erfordert einen lösba¬ ren Wärmekontakt, der beim Abkühlen zunächst eine thermisch gut leitende Verbindung zwischen der erεten Kälteεtufe und dem Magneten herεtellt und der erεt bei einem Temperaturni¬ veau nahe der Endtemperatur der erεten Stufe geöffnet wird. Mit der Kälteleiεtung der zweiten Kältestufe erreicht dann der Magnet die Betriebstemperatur. Erforderlich ist hierbei ein sehr hoher thermischer Widerstand im offenen Zustand des Wärmekontaktes, da die zweite Stufe durch einen Leckwärme¬ strom über diesen Widerstand belastet würde. Ein Ausfüh- rungsbeispiel entsprechender lösbarer Warmekontakte geht aus den Figuren 2 und 3 hervor, wobei die Figur 2 den geεchloεεe- nen Zuεtand deε Wärmekontakteε und die Figur 3 den geöffneten Zuεtand veranεchaulichen. Der in den Figuren gezeigte und allgemein mit 40 bezeichnete Wärmekontakt wird durch minde¬ εtenε eine thermiεch gut leitende Kontaktplatte 41 gebildet, die εich zwiεchen einer mit der zu kühlenden Einrichtung 10 εtarr verbundenen, gut wärmeleitenden Halteεtruktur 43 und einem zumindeεt weitgehend auf der Temperatur der erεten Kälteεtufe gehaltenen Teil deε tieftemperaturεeitigen Ab- Schnittes 4b der Kältemaschine befindet. Dieser Teil des Kältemaεchinenabεchnittε 4b kann beiεpielsweise von dem ther¬ mischen Verbindungsεtuck 15 gebildet εein. Da dieεes Verbin- dungεεtück εtarr mit dem Kaltemaschinenabschnitt 4b oder der darum angeordneten Gehauεeeinheit 12 verbunden lεt, folgt eε entεprechend der Auεlenkung der federnden Elemente 30 und 31. Während deε Abkühlvorgangeε von der Raumtemperatur aus bleibt zunächst der Innenraum 27 der externen Gehauseeinheit 26 belüftet. Aufgrund der entsprechenden Druckverhältniεεe pO wird der Kaltemaεchinenteil 4 vom äußeren Luftdruck mit der Kraft Lk gegen die weiche Abεtutzung über die Federungsele- mente 30 und 31 in Richtung auf den Magneten 10 hin gedrückt, biε der Warmekontakt 40 der erεten Kältestufe 5 auf seinen mechanischen Anschlag trifft (vgl. Figur 2) . Dieεer Anεchlag wird von den Kontaktplatten 41 auf der mit dem Magneten 10 starr verbundenen Haltestruktur 43 gebildet. Aufgrund einer Evakuierung deε Innenraumε 27 auf einen Druck p3 nach der Vorkühlung deε Magneten auf etwa die Temperatur der erεten Kälteεtufe 5 wird der Kältemaεchinenteil 4 von der Kraft Lk entlaεtet, so daß εich die Federungεelemente 30 und 31 bei der nur noch vorhandenen Gewichtεkraft Gk entεprechend auεdehnen. Daε mit dem Kältemaεchinenteil 4 εtarr verbundene Verbindungsstück 15 wird so um ein diesem Hub entsprechendes Maß von den Platten 41 angehoben, so daß nunmehr der Wärme- kontakt 40 geöffnet lεt.The cooling capacity of the second stage 6 of the refrigeration machine part 4, to which the device to be cooled, for example the magnet 10, is thermally coupled, is about 1/5 of the performance of the first stage 5 in a conventional Gifford-McMahon refrigeration machine 3. The heat capacity is one However, in a typical design, super-conductive magnets amount to at least 2/3 of the thermal mass to be cooled. In order to cool a superconducting magnet from room temperature to operating temperature only with the aid of a refrigeration machine, it is therefore advantageous to use the comparatively high refrigeration capacity of the first stage 5 of the refrigeration machine to precool the magnet. This requires a releasable thermal contact which, when cooling, first establishes a thermally highly conductive connection between the first cold stage and the magnet and which is opened at a temperature level close to the end temperature of the first stage. With the refrigeration of the second refrigeration stage, the magnet then reaches the operating temperature. A very high thermal resistance in the open state of the heat contact is required here, since the second stage would be loaded by a leakage heat flow through this resistor. An exemplary embodiment of corresponding releasable heat contacts can be seen in FIGS. 2 and 3, FIG. 2 illustrating the closed state of the heat contacts and FIG. 3 the opened state. The heat contact shown in the figures and generally designated 40 is formed by at least one thermally well-conductive contact plate 41 which is between a well thermally conductive holding structure 43 rigidly connected to the device 10 to be cooled and at least largely at the temperature of the first Part of the low-temperature side Section 4b of the refrigerator is located. This part of the refrigeration machine section 4b can be formed, for example, by the thermal connecting piece 15. Since this connection piece is rigidly connected to the cold machine section 4b or the housing unit 12 arranged around it, the deflection of the resilient elements 30 and 31 follows accordingly. During the cooling process from the room temperature, the interior 27 of the external housing unit 26 initially remains ventilated. Due to the corresponding pressure ratio pO, the cold machine part 4 is pressed by the external air pressure with the force Lk against the soft wear over the suspension elements 30 and 31 in the direction of the magnet 10 until the warm contact 40 of the first cold stage 5 hits its mechanical stop (see Figure 2). This stop is formed by the contact plates 41 on the holding structure 43 rigidly connected to the magnet 10. Due to an evacuation of the interior 27 to a pressure p3 after the pre-cooling of the magnet to approximately the temperature of the first cooling stage 5, the refrigeration machine part 4 is relieved of the force Lk, so that the suspension elements 30 and 31 expand accordingly with the only existing weight force Gk . The connecting piece 15, which is rigidly connected to the refrigeration machine part 4, is raised by an amount corresponding to this stroke from the plates 41, so that the heat contact 40 can now be opened.
Im offenen Zuεtand (vgl. Figur 3) ist somit eine vollständige Trennung der zu kühlenden Einrichtung 10 und der mit ihr ver¬ bundenen Haltestruktur 43 von der ersten Kaltestufe 5 des Kältemaschinenabschnittε 4b gewährleiεtet, εo daß die zweite Kälteεtufe 6 dieses Abschnittε mit keinerlei Leckwarme von der wärmeren erεten Stufe belaεtet wird. Verglichen mit be¬ kannten Gaεwarmeεchaltern reicht hier vorteilhaft ein kleines Bauvolumen auε, um dennoch einen niedrigen Warmewiderstand zu ermöglichen. In den Figuren 1 biε 3 iεt eine erfindungεgemäß gefederte Ab- εtützung einer Kältemaεchine oder eines Teilε von ihr veran¬ schaulicht. Eine entεprechende Aufhängung über Federungεele- mente, die von der auf einen raumtemperaturεeitigen Ma¬ schinenabschnitt einwirkenden Luftdruckkraft Lk zu entlasten sind, ist ebensogut möglich. In the open state (cf. FIG. 3), a complete separation of the device 10 to be cooled and the holding structure 43 connected to it from the first cold stage 5 of the refrigeration machine section 4b is thus guaranteed, so that the second cold stage 6 of this section does not have any leak heat the warmer first stage is loaded. Compared to known gas heat switches, a small construction volume is advantageously sufficient here in order to nevertheless enable a low heat resistance. In FIGS. 1 to 3, a support of a refrigeration machine or a part of it sprung according to the invention is illustrated. A corresponding suspension via suspension elements, which are to be relieved of the air pressure force Lk acting on a machine section on the room temperature side, is just as possible.

Claims

Patentansprüche claims
1. Vorrichtung zur indirekten Kühlung einer elektrischen, auf Tieftemperatur zu haltenden, insbesondere supraleitenden Ein- richtung, die εich in einem evakuierbaren Innenraum eineε Va- kuumgehauεeε befindet, welche Vorrichtung wenigεtenε einen Kältemaεchinenteil enthält, der einen raumtemperaturεeitigen Maεchinenabεchnitt und einen tieftemperaturseitigen Maschinenabschnitt, welcher in einem evakuierbaren Raumbereich angeordnet ist, aufweist, durch eine Öffnung des Vakuumgehäuseε beweglich in deεεen Innenraum hineinragt, über Federungεelemente an dem Vakuumgehäuεe federnd und in einer deεεen Öffnung abdichtenden Weiεe befeεtigt lεt εowie an seinem auf Tieftemperatur liegenden Ende mit der elek¬ trischen Einrichtung gut wärmeleitend verbunden iεt, d a d u r c h g e k e n n z e i c h n e t , daß der raum¬ temperaturseitige Abεchnitt (4a) deε Kältemaεchinenteilε (4) in einem evakuierbaren Raum (27) einer mit dem Vakuumgehäuεe (8) εtarr verbundenen Gehauseeinheit (26) angeordnet ist.1. Device for indirect cooling of an electrical, in particular superconducting device to be kept at low temperature, which is located in an evacuable interior of a vacuum housing, which device contains at least one refrigeration machine part, which has a machine section at room temperature and a machine section at low temperature, which in is arranged in an evacuable area, has a movable protrusion into its interior through an opening in the vacuum housing, resiliently attaches to the vacuum housing via suspension elements, and is fixed in a sealing manner in this opening, and is connected to the electrical device with good thermal conductivity at its low-temperature end iεt, characterized in that the room-temperature-side section (4a) of the refrigeration machine part (4) in an evacuable space (27) is rigidly connected to the vacuum housing (8) Housing unit (26) is arranged.
2. Kühlvorrichtung nach Anεpruch 1, d a d u r c h g e ¬ k e n n z e i c h n e t , daß der den tieftemperaturεei- tigen Abεchnitt (4b) deε Kältemaεchinenteilε (4) umgebende Raumbereich Teil deε Innenraums (9) des Vakuumgehäuseε (8) iεt .2. Cooling device according to claim 1, so that the space area surrounding the low-temperature section (4b) of the refrigeration machine part (4) is part of the interior (9) of the vacuum housing (8).
3. Kühlvorrichtung nach Anεpruch 1, d a d u r c h g e - k e n n z e i c h n e t , daß der den tieftemperaturεei- tigen Abεchnitt (4b) deε Kältemaεchinenteilε (4) umgebende Raumbereich der evakuierbare Innenraum (13) einer in den In¬ nenraum (9) deε Vakuumgehauses (8) hineinragenden, gegenüber diesem (9) vakuumdicht abgetrennten Gehäuεeeinheit (12) lεt, die als eine von dem evakuierbaren Raum (27) der Gehäuseein- heit (26) des raumtemperaturseitigen Abεchnitteε (4a) zu¬ gängliche Schleuεe geεtaltet iεt.3. Cooling device according to claim 1, characterized in that the space area surrounding the low-temperature section (4b) of the refrigeration machine part (4) is the evacuable interior space (13), which projects into the interior space (9) of the vacuum housing (8), compared to this (9) vacuum-tightly separated housing unit (12), which acts as one of the evacuable space (27) of the housing unit. Unit (26) of the section (4a) on the room temperature side which is accessible is designed as a lock.
4. Kühlvorrichtung nach Anεpruch 3, d a d u r c h g e - k e n n z e i c h n e t , daß mindestens eine Kälteεtufe (5 oder 6) deε Kältemaschinenteils (4) über lösbare Wärmekontak¬ te (17 bzw. 18) mit benachbarten Teilen der Gehäuεeeinheit (12) thermiεch verbunden iεt.4. Cooling device according to claim 3, so that at least one refrigeration stage (5 or 6) of the refrigeration machine part (4) is thermally connected to adjacent parts of the housing unit (12) via detachable heat contacts (17 or 18).
5. Kühlvorrichtung nach einem der Anεprüche 1 biε 4, d a ¬ d u r c h g e k e n n z e i c h n e t , daß der Kältema¬ εchinenteil (4) über die Federungselemente (30) sich an dem Vakuumgehäuse (8) abstützt oder an diesem aufgehängt iεt.5. Cooling device according to one of claims 1 to 4, so that the cooling machine part (4) is supported by the suspension elements (30) on the vacuum housing (8) or suspended from it.
6. Kühlvorrichtung nach einem der Anεprüche 1 biε 5, d a ¬ d u r c h g e k e n n z e i c h n e t , daß parallel zu den Federungεelementen (30) elaεtiεche Federdämpferelemente (31) angeordnet εind.6. Cooling device according to one of claims 1 to 5, that is, that elastic spring damper elements (31) are arranged parallel to the suspension elements (30).
7. Kühlvorrichtung nach Anεpruch 5 oder 6, d a d u r c h g e k e n n z e i c h n e t , daß zur Abdichtung der Öff¬ nung (7) deε Vakuumgehäuεeε (8) gegenüber dem Kältemaεchi¬ nenteil (4) die Federungεelemente (30) und/oder die Feder¬ dämpferelemente (31) herangezogen εind.7. Cooling device according to claim 5 or 6, characterized in that the spring elements (30) and / or the spring damper elements (31) are used to seal the opening (7) of the vacuum housing (8) with respect to the cooling part (4) are.
8. Kühlvorrichtung nach einem der Anεprüche 1 biε 7, d a ¬ d u r c h g e k e n n z e i c h n e t , daß der tief- temperaturseitige Abschnitt (4b) des Kältemaschinenteilε (4) mindeεtenε zwei Kälteεtufen (5, 6) aufweist.8. Cooling device according to one of the claims 1 to 7, so that the low-temperature side section (4b) of the refrigerator part (4) has at least two cooling stages (5, 6).
9. Kühlvorrichtung nach einem der Ansprüche 1 bis 8, d a ¬ d u r c h g e k e n n z e i c h n e t , daß im belüfteten Zuεtand deε evakuierbaren Raumes (27) um den raumtemperatur¬ seitigen Kältemaεchinenabεchnitt (4a) die Auεlenkung der Fe- derungεelemente (30) durch einen Anεchlag (33) begrenzt iεt. 9. Cooling device according to one of claims 1 to 8, since ¬ characterized in that in the ventilated state of the evacuable space (27) around the room temperature side Kältemaεchinenabεchnitt (4a) limits the deflection of the spring elements (30) by a stop (33) is.
10. Kühlvorrichtung nach den Anεprüchen 8 und 9, d a ¬ d u r c h g e k e n n z e i c h n e t , daß der Anεchlag alε ein Wärmekontakt (40) ausgebildet ist, der nur im belüf¬ teten Zustand deε evakuierbaren Raumeε (27) um den räumtempe- raturεeitigen Kältemaεchinenabεchnitt (4a) eine wärmeleitende Verbindung zwiεchen einer erεten Kälteεtufe (5) und der zu kühlenden Einrichtung (10) herstellt.10. Cooling device according to claims 8 and 9, since ¬ characterized in that the stop is designed as a thermal contact (40), which is only in the ventilated state of the evacuable space (27) around the room temperature-side cooling machine section (4a) a heat-conducting section Establishes connection between a first cold stage (5) and the device (10) to be cooled.
11. Kühlvorrichtung nach einem der Ansprüche 1 biε 10, d a d u r c h g e k e n n z e i c h n e t , daß daε auf Tieftemperatur liegende Ende des tieftemperaturseitigen Käl¬ temaschinenabschnittes (4b) mittels elastischer Verbindungs¬ glieder (22) thermisch mit der auf Tieftemperatur zu halten¬ den Einrichtung (10) verbunden ist. 11. Cooling device according to one of claims 1 to 10, characterized in that the low-temperature end of the low-temperature side of the refrigeration machine section (4b) is thermally connected to the low-temperature device (10) by means of elastic connecting members (22) .
EP96934396A 1995-09-11 1996-08-29 Indirect cooling system for an electrical device Withdrawn EP0850386A1 (en)

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DE19533555A DE19533555A1 (en) 1995-09-11 1995-09-11 Device for indirect cooling of an electrical device
DE19533555 1995-09-11
PCT/DE1996/001606 WO1997010469A1 (en) 1995-09-11 1996-08-29 Indirect cooling system for an electrical device

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US5934082A (en) 1999-08-10

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