Compressor Device and a Cooling Device Having the Compressor Device

Abstract

A cooling device with a novel compressor includes a cylinder, a connector, a working gas line, a cryocooler, a piston, a drive device and a compressor element. The connector is disposed at the end of the cylinder. The working gas line connects the connector to the cryocooler. The piston is movable back and forth inside the cylinder. A transfer space exists inside the cylinder between the piston and the end of the cylinder. A portion of the transfer space contains a transfer fluid. The drive device is adapted to move the piston back and forth inside the cylinder. The compressor element is disposed inside the transfer space. A working space that contains a working gas exists inside the compressor element. The working gas contained in the working space inside the compressor element is periodically compressed by the transfer fluid as the piston periodically moves back and forth inside the cylinder.

Claims

1. A compressor device, comprising: a cylinder; a piston arranged inside the cylinder and which delimits a transfer space filled with a transfer fluid and is periodically movable back and forth via a drive device; a compressor element arranged inside the transfer space, in particular metal bellows, which delimits a working space filled with a working gas; and a connector, via which the working space is connectable with a working gas line to a Gifford-McMahon cooler or a pulse tube cooler, wherein the compressor element and the working gas contained therein are periodically compressed indirectly via the transfer fluid displaced by the piston.

2. The compressor device of claim 1, wherein a volume of a fluid space enclosed by the piston, the compressor element and the cylinder is constant.

3. The compressor device of one of claim 1 or 2, wherein the transfer space and the working space are completely configured in the cylinder.

4. The compressor device of one of claims 1 to 3, wherein a pressure of the working medium in the working space corresponds to a pressure of the transfer fluid in the transfer space at any point in time.

5. The compressor device of claim 4, wherein the pressure of the working medium and the pressure of the transfer fluid are greater than an ambient pressure of an environment surrounding the compressor device.

6. The compressor device of one of claims 1 to 5, wherein a maximum piston stroke is greater than a maximum compressor-element stroke (L).

7. The compressor device of one of claims 1 to 6, wherein the piston is periodically movable back and forth by a connector rod.

8. The compressor device of one of claims 1 to 7, wherein the compressor element is guided in a stroke direction.

9. The compressor device of one of claims 1 to 8, wherein a closed displacer element is configured in the working space.

10. A cooling device with a compressor device of one of claims 1 to 9 and with a Gifford-McMahon cooler or a pulse tube cooler.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.

[0013] FIG. 1 is a schematic illustration of a compressor device according to the invention in a general embodiment.

[0014] FIG. 2 is a schematic illustration of the compressor device according to the invention in a special embodiment.

[0015] FIG. 3 is a schematic illustration of a structure of a cooling device according to the invention in a first embodiment.

[0016] FIG. 4 is a schematic illustration of a structure of the cooling device according to the invention in a second embodiment.

[0017] FIG. 5 is a schematic illustration of a compressor device according to the invention in a first alternative embodiment.

[0018] FIG. 6 is a schematic illustration of a compressor device according to the invention in a second alternative embodiment.

[0019] FIG. 7 is a schematic illustration of a compressor device according to the invention in a third alternative embodiment.

[0020] FIG. 8 is a schematic illustration of a compressor device according to the invention in a fourth alternative embodiment.

DETAILED DESCRIPTION

[0021] Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

[0022] Specifically, the object is solved by a compressor device with a cylinder, a piston arranged inside the cylinder and which delimits a transfer space filled with a transfer fluid and is periodically movable back and forth via a drive device, a compressor element arranged inside the transfer space, preferably bellows, in particular metal bellows, which delimits a working space (compression space) filled with a working gas, and a connector, via which the working space is connectable with a working gas line (pressure line) to a Gifford-McMahon cooler or a pulse tube cooler, in particular a two-stage 4K (four Kelvin) cooler, wherein the compressor element and the working gas contained therein are periodically compressed/compacted indirectly via the transfer fluid displaced by the piston.

[0023] In other words, the compressor device includes the cylinder with a cylinder track configured on the inside of the cylinder and the piston running in the cylinder with a piston skirt configured in the circumferential direction of the piston. The piston skirt slides in a sealing manner on the cylinder track of the cylinder. Preferably, at least one annular seal/piston ring is configured between the piston skirt and the cylinder track. The piston also includes a piston roof, which faces the transfer space filled with the transfer fluid and delimits it. The piston is provided and configured to perform a periodic linear movement in a direction of a central cylinder fiber (central cylinder axis), which extends in a longitudinal direction of the cylinder. The compressor element is configured in the transfer space and includes at least one, preferably accordion-shaped, wall. In other words, the compressor element is preferably configured as a bellows. The compressor element surrounds the working space filled with the working gas. In other words, the compressor element separates the working space from the transfer space. The working space is configured with the connector, which firmly or detachably connects the working space to the working gas line. The connector is preferably configured on a side of the compressor element facing away from the piston. The working gas line is provided and configured to connect the working space to the Gifford-McMahon cooler or to the pulse tube cooler or to any other suitable cooler. The working space is variable in volume due to the preferably accordion-shaped wall. The linear movement of the piston exerts/transmits a force on the compressor element via the transfer fluid and the working gas contained in the working space is periodically compressed/compacted and expanded.

[0024] Accordingly, the core of the invention is to periodically compress and expand the working gas contained in the compressor element of the compressor device via the displacement of the piston indirectly via the transfer fluid.

[0025] Furthermore, the core of the invention is that a pressure generating location (force generating location) and a compression location are configured in a cylinder.

[0026] Another core of the invention is that the piston and the compressor element are mechanically decoupled.

[0027] In other words, the piston and the compressor element are arranged in the cylinder in such a way that they do not touch each other at any time. Furthermore, the force acting on the piston or the force to be transmitted by the piston is transmitted exclusively hydraulically to the compressor element. The present invention dispenses with a mechanical connection between the piston and compressor element for power transmission.

[0028] By configuring the compressor device in this way, a rotary valve can be dispensed with, thereby reducing losses and significantly increasing the efficiency of the compressor device. In addition, such a compressor device can be configured more compactly, since a single-cylinder configuration of the compressor device is possible. A further advantage of such a compressor device is that the reliability of the compressor device can be increased by reducing the number of assemblies.

[0029] The configuration of the working space in the compressor element, in particular the configuration of the compressor element as metal bellows, can also prevent water, transfer fluid, oil or any other foreign substance from penetrating/diffusing into the working gas and contaminating it/causing impurities. Contamination of the working gas with the foreign substance could lead to freezing of the working gas and to damaging of seals. In particular, the configuration of the compressor element as metal bellows has the advantage over a configuration of the compressor element made of rubber, for example, that the working gas cannot escape from the compressor element or through the compressor element into the transfer space.

[0030] In a first aspect, a volume of a space/fluid space enclosed by the piston, the compressor element and the cylinder may be constant.

[0031] In other words, an area of the transfer space outside the compressor element/working space may be completely filled with the transfer fluid, wherein the transfer fluid may be a substantially incompressible fluid.

[0032] This ensures that the force exerted by the piston on the transfer fluid can be transmitted to the bellows evenly and without localized force peaks. This ensures that the compressor element is exclusively compressed and expanded in the intended manner, which considerably extends the service life of the compressor element and prevents premature failure of the compressor element. Furthermore, completely filling the transfer space with the transfer fluid prevents the transfer fluid from foaming during operation or the formation of foam.

[0033] Furthermore, the transfer space and the working space may be completely configured in the cylinder without any protrusion.

[0034] In a further aspect, a pressure of the working medium in the working space may correspond to a pressure of the transfer fluid in the transfer space at any point in time.

[0035] In other words, the pressure in the compressor element corresponds to the pressure surrounding the compressor element at all times. In yet other words, the working medium in the working space and the transfer fluid in the transfer space are in pressure equilibrium.

[0036] In this way, it can be ensured that the compressor element itself does not experience or absorb large loads/forces and that the compressor element may be configured with thin walls, which further reduces losses during compression of the compressor element.

[0037] In a further aspect, the pressure of the working medium and the pressure of the transfer fluid may be greater than an ambient pressure of an environment surrounding the compressor device.

[0038] In other words, the compressor device is pre-tensioned so that in every position of the piston in the cylinder there is an overpressure of the working medium and of the transfer medium compared to the environment.

[0039] In a further aspect, a maximum piston stroke may be greater than a maximum compressor-element stroke.

[0040] In other words, an amplitude that the piston performs in the periodic reciprocating motion in a piston moving direction may be larger than a maximum change of a compressor element extension of the compressor element in the piston moving direction.

[0041] A lower maximum compressor element stroke may be used to minimize mechanical stress on the compressor element, in particular in kinks/folds of the compressor element, which extends the service life of the compressor element and reduces the risk of failure.

[0042] In a further aspect, the piston may be periodically movable back and forth by a connector rod. By using the connector rod to move the piston, a conventional electric motor may be used as the drive device. Alternatively, the piston may be movable back and forth by a threaded rod or the like.

[0043] In a further aspect, the compressor element may be guided in a stroke direction.

[0044] In other words, the compressor device may include at least one guiding element which is provided and configured to guide the compressor element during compression and extension and to prevent the compressor element from buckling or collapsing in an uncontrolled manner. The guiding element may, for example, be configured in the form of a rod or sleeve. Preferably, more than one guiding element may be configured in the compressor device.

[0045] In a further aspect, a closed displacer (dome element) may be configured in the working space.

[0046] In other words, the displacer element may be configured on an inner side of the compressor element facing the working space, preferably on an end face of the compressor element close to the piston. The displacer element may be a gas-tight, closed, in particular cylindrical, element, which may be configured to be firmly connected to the compressor element.

[0047] Such a displacer element in the working space may reduce the (gas) volume of the working space. This allows the working space to have a (dead/residual) volume of almost zero in the compressed state, which reduces the displacement of the compressor element and thus the load on the compressor element.

[0048] In a further aspect, a maximum longitudinal extension of the compressor element in the stroke direction in the expanded state may be more than twice as large as a minimum longitudinal extension in the stroke direction of the compressor element in the compressed state.

[0049] In a further aspect, the transfer space and/or the working space may be connected to at least one compensation tank, optionally via a valve, in order to pre-tension the compressor device and to compensate for any changes in volume, in particular during start-up or commissioning of the compressor device.

[0050] In a further aspect, the compression of the compressor element is reversible. This means that the compressor element only changes its geometry within a predefined range during operation and then returns to its original geometry.

[0051] In a further aspect, a wall thickness of the compressor element may be constant. Preferably, the wall thickness of the compressor element may be less than 0.2 mm.

[0052] In a further aspect, the compressor element may be configured from a plurality of membrane pairs. Preferably, the compressor element may be configured from at least 30membrane pairs. Particularly preferably, the compressor element may be configured from at least 40 membrane pairs.

[0053] By configuring the compressor element with a large number of membrane pairs, it can be ensured that each of the membrane pairs only experiences a small deflection during the stroke movement of the compressor element, which considerably reduces the mechanical load on the compressor element.

[0054] In a further aspect, the transfer space may be configured with a multi-stepped geometry, in particular a two-stepped geometry. In other words, the transfer space may have a jump in diameter, wherein a first diameter in a region of the piston may preferably be smaller than a second diameter in a region of the compressor element. In this way, the force to be applied by the piston to displace the transfer fluid may be adapted to the drive force or drive torque of the drive device.

[0055] In a further aspect, the drive device may be configured with a control apparatus and/or may be connected to the control apparatus which controls the compression/compacting and the expansion of the working medium in the working space via the periodic longitudinal movement of the piston, in particular via a rotational speed of the drive device.

[0056] In a further aspect, a displacement volume displaced by the piston during movement of the piston may correspond to a working space volume change, thereby significantly simplifying control of the compressor device.

[0057] In a further aspect, a filter may be connected downstream of the compressor device.

[0058] In a further aspect, the working medium may be helium.

[0059] It is advantageous if the movement profile of the piston is not a linear or sinusoidal profile, but follows a step function in which the working gas is quickly compressed, the pressure is maintained and then the working gas is quickly expanded again. This movement profile may be achieved by corresponding variable driving of the drive device.

[0060] Alternatively, the drive device may be driven uniformly and the step-functional movement of the piston may be achieved via a corresponding transfer element, such as a cam. In other words, a linear movement of the drive device may be translated into an almost step-functional movement of the piston by a cam-shaped transfer element. In other words, the transfer element may be asymmetrical to an axis of rotation of the transfer element.

[0061] In a further aspect, the one drive device may drive more than one compressor device. Preferably, in such a configuration, the cylinders may be arranged in a boxer formation. In other words, for example, two cylinders may be configured diametrically opposite the drive device, wherein the cylinders may have an identical structure. Each of the cylinders may be configured with a piston and a compressor element.

[0062] In a further aspect, the transfer fluid may (also) be used as a lubricant for the drive device. In other words, on a side of the piston facing away from the transfer space, the transfer fluid may be configured as a lubricant. In particular, the transfer fluid may lubricate a pairing of motor and connector rod and a pairing of connector rod and piston. By configuring the transfer fluid as a lubricant, possible leakages of the transfer fluid via the piston in the direction of the drive device may be prevented from having a negative effect on the drive device.

[0063] In a further aspect, the compressor device may be configured for an operating frequency range between 0.1 and 10 Hz and in particular for an operating frequency range between 0.5 and 5 Hz.

[0064] The object is further solved by a cooling device comprising a compressor device according to one of the above aspects and a Gifford-McMahon cooler or a pulse tube cooler.

[0065] In other words, the cooling device comprises a compressor device according to one of the above aspects and the Gifford-McMahon cooler or the pulse tube cooler connected via the connector. Optionally, a heat exchanger for cooling the working gas may be configured between the cooling device and the Gifford-McMahon cooler or the pulse tube cooler, or a cooling device may be configured directly on the Gifford-McMahon cooler or the pulse tube cooler.

[0066] In this way, it is possible to dispense with a rotary valve and to create a pressure curve directly with the compressor device. The Gifford-McMahon cooler or the pulse tube cooler may be connected directly to the compressor device. Extremely clean helium gas (6N=99.9999% helium) is required to operate the Gifford-McMahon cooler or the pulse tube cooler.

[0067] In one aspect, the compressor device and the Gifford-McMahon cooler or the pulse tube cooler may be connected via a high pressure connection.

[0068] In a further aspect, the cooling device or the compressor device may be preloaded with 16 bar. A working area of the compressor device may be between 8 bar and 24bar.

[0069] Furthermore, a compressor refrigeration machine may be configured with a compressor device according to one of the above aspects, an evaporator and a condenser.

[0070] FIG. 1 shows a compressor device 2 according to the invention, comprising a gas-tight cylinder 4, a piston 6 arranged in the cylinder 4, a compressor element in the form of a (metal) bellows 8 and a connector 10, wherein the compressor device 2 is provided and configured to be coupled to a cooling device or to form part of the cooling device. The cylinder 4 includes a (cylinder) running surface 12 configured on an inner side of the cylinder 4. The piston 6 includes a piston skirt 14 configured on an outer circumferential surface of the piston 6, wherein the running surface 12 of the cylinder 4 and the piston skirt 14 of the piston 6 are matched such that the piston 6 is sealingly movable in the cylinder 4 linearly along a central cylinder axis ZM. The piston 6 and the cylinder 4 delimit a transfer space 16. The transfer space 16 is filled with a transfer fluid. The bellows 8 is arranged in the transfer space 16 and surrounded by the (incompressible) transfer fluid. Specifically, the transfer fluid is disposed in a fluid space 18 encapsulated/enclosed between the cylinder 4, the piston 6 and the bellows 8. A volume of the fluid space 18 is substantially invariable, wherein a geometry of the fluid space 18 may change.

[0071] The bellows 8 contains and limits a working space 20. The working space 20 is filled with a working gas, preferably helium. In the embodiment shown here, the bellows 8 is configured as a bellows with an accordion-shaped wall 22. The bellows 8 separates the transfer space 16 and the working space 20 from each other in a gas-tight and fluid-tight manner. The connector 10 is configured on a side of the working space 20 facing away from the piston 6. The connector 10 is provided and configured to connect the compressor device 2 to a cold head 38 of a cryocooler (see FIG. 3), for example a Gifford-McMahon cooler or a pulse tube cooler.

[0072] FIG. 2 shows the compressor device 2 in an embodiment, wherein the piston 6 is linearly movable along the central cylinder axis ZM via a connector rod 24.

[0073] A functional principle of the compressor device 2 according to the invention is described below with reference to FIG. 2. The drive of the piston 6 via the connector rod 24 is exemplary. Of course, other types of drive for the piston 6, which are suitable for periodically moving the piston 6 back and forth along the central cylinder axis ZM, are to be regarded as equivalent.

[0074] A drive device in the form of an electric motor 26 driven by a corresponding control device (not shown) rotates a disk 28 on which the connector rod 24 is mounted eccentrically at a first bearing point 30. The connector rod 24 is also mounted and fixed on the piston 6 at a second bearing point 32. The connector rod 24 converts a rotational and circular movement of the disk 28 into a linear movement of the piston 6 along the central cylinder axis ZM. In other words, a force generated by the electric motor 26 is transmitted to the piston 6 via the disk 28 and the connector rod 24.

[0075] When the piston 6 moves along the central cylinder axis ZM in a direction toward the bellows 8, the force is transferred to the transfer fluid in the fluid space 18. The transfer fluid, which surrounds the bellows 8, transmits the force to the bellows 8 and compresses the working gas contained in the bellows 8. Since the transfer fluid is an approximately incompressible fluid, the force applied by the electric motor 26 (minus any frictional losses) is substantially completely converted into compression of the bellows 8 and of the working gas contained in the working space 20. In other words, the working gas in the working space 20 is periodically compressed by the force of the electric motor 26. A working area of the bellows 8 lies between a first length L1 in the compressed state and a second length L2 in the relaxed state. A (maximum) change in length L of the bellows 8, which corresponds to a difference between the first length L1 and the second length L2, is much smaller than the first length L1 or the second length L2.

[0076] FIG. 3 shows a cooling device 34 according to the invention with the compressor device 2 in a first embodiment. The working space 20 of the compressor device 2 is connected to a pressure line 36 via the connector 10. The pressure line 36 connects the compressor device 2 in a gas-tight manner to a cold head 38 of a cryocooler configured as a Gifford-McMahon cooler or a pulse tube cooler. For operation of such a cold head 38, a specific working gas volume is periodically compressed and expanded by the compressor device 2 in a predetermined frequency range.

[0077] FIG. 4 shows the cooling device 34 according to the invention with the compressor device 2 in a second embodiment. The cooling device 34 of the second embodiment corresponds substantially to the cooling device 34 of the first embodiment. In the second embodiment, a heat exchanger 40 is configured between the connector 10 of the compressor device 2 and the cold head 38, which is provided and configured to cool down the working gas, in particular after compression.

[0078] Alternative embodiments of the compressor device 2 are explained below with reference to FIGS. 5-8. Elements corresponding to the general embodiment described in FIG. 1 are not described again below.

[0079] The first alternative embodiment of the compressor device 2 shown in FIG. 5 includes a dome element 42 in the bellows 8. The dome element 42 is configured in the working space 20 on an end face of the bellows 8 facing the piston 6. The dome element 42 reduces a gas volume/internal volume of the working space 20. The dome element 42 is sealed gas-tight with respect to the working space 20.

[0080] FIG. 6 shows a second alternative embodiment of the compressor device 2 with a shaft-shaped or rod-shaped guiding element 44. The rod-shaped guiding element 44 is configured in the transfer space 16 on the end face of the bellows 8 facing the piston 6. The rod-shaped guiding element 44 extends away from the bellows 8 toward the piston 6 and is mounted in the piston 6. The rod-shaped guiding element 44 is linearly guided or mounted in the piston 6. Preferably, the rod-shaped guiding element 44 is guided or mounted in a bushing in the piston 6. Optionally, more than one rod-shaped guiding element 44 is configured on the bellows 8. The rod-shaped guiding element 44 prevents the bellows 8 from tilting relative to the piston 6.

[0081] FIG. 7 shows a third alternative embodiment of the compressor device 2 with a flat guiding element 46. The flat guiding element 46 is configured in the transfer space 16 on the end face of the bellows 8 facing the piston 6. The flat guiding element 46 extends radially outward toward the running surface 12 and guides the bellows 8 relative to the running surface 12. Bore holes 48 are configured in the flat guiding element 46, which ensure an unimpeded flow of the transfer fluid in the transfer space. The flat guiding element 46 prevents the bellows 8 from tilting relative to the cylinder 4.

[0082] FIG. 8 shows a fourth alternative embodiment of the compressor device 2, wherein the cylinder 4 is configured in two stages. The cylinder 4 includes a first cylinder portion 50, in which the bellows 8 is configured, and a second cylinder portion 52, in which the piston 6 is configured. A first diameter of the first cylinder portion 50 is larger than a second diameter of the second cylinder portion 52. In other words, a pressure ratio is implemented in the cylinder 4 by the first cylinder portion 50 and the second cylinder portion 52.

[0083] Of course, the features of all embodiments described may be combined as desired within the claims, if technically possible.

[0084] For example, it is conceivable that the compression device 2 is configured with the dome element 42 in the working space 20 and the bellows 8 is additionally configured with the rod-shaped guiding element 44 and/or the flat guiding element 46.

[0085] It is also conceivable that the compression device 2 is configured with the cylinder 4, which has the first cylinder portion 50 and the second cylinder portion 52, and the dome element 42.

[0086] Furthermore, it is conceivable that the compressor device is configured with the cylinder 4, which has the first cylinder portion 50 and the second cylinder portion 52, the dome element 42 and the rod-shaped guiding element 44 and/or the flat guiding element 46.

REFERENCE NUMERALS

[0087] 2 compressor device [0088] 4 cylinder [0089] 6 piston [0090] 8 bellows [0091] 10 connector [0092] 12 (cylinder) running surface [0093] 14 piston skirt [0094] 16 transfer space [0095] 18 fluid space [0096] 20 working space [0097] 22 wall [0098] 24 connector rod [0099] 26 electric motor [0100] 28 disk [0101] 30 first bearing point [0102] 32 second bearing point [0103] 34 cooling device [0104] 36 pressure line [0105] 38 cold head [0106] 40 heat exchanger [0107] 42 dome element/displacer element [0108] 44 rod-shaped guiding element [0109] 46 flat guiding element [0110] 48 bore hole [0111] 50 first cylinder portion [0112] 52 second cylinder portion [0113] ZM central cylinder axis [0114] L1 first length [0115] L2 second length

[0116] L change in length

[0117] Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.