Patent Application
20250129977
The present disclosure relates to a compressor device and a cooling device comprising the compressor device and a Gifford-McMahon cooler or a pulse tube cooler.
Cryocoolers such as pulse tube coolers and Gifford-McMahon coolers are widely used to cool magnetic resonance scanners, cryogenic pumps, quantum computers, quantum communication systems and the like. Gas compressors and, in particular, helium compressors are used in combination with rotary valves or spin valves. A helium compressor is connected to a rotary valve via a high-pressure line and a low-pressure line. On the output side, the rotary valve is connected via a gas line to a cryocooler in the form of a Gifford-McMahon cooler or a pulse tube cooler. The high or low pressure side of the gas compressor is alternately connected to the pulse tube cooler or to the Gifford-McMahon cooler via the rotary valve. The rate at which the compressed helium is fed into the cooling device and discharged again is in the range of 1-2 Hz. The disadvantage of such cooling or compressor systems is that the motor-driven rotary valve causes losses of approximately 50% of the input power of the compressor.
Cooling devices with pulse tube coolers or Gifford-McMahon coolers are known from DE 10137552C1.
DE 633104A discloses a compressor device with a compression apparatus in which a working medium is periodically compressed and expanded again by a reciprocating compressor element in the form of a piston. The drive device comprises a pressure cylinder with a reciprocating piston. The drive device is mechanically coupled to the compressor element. Both the drive device and the compressor element are constructed with individual pressure cylinders in which a compressor piston or compression piston is mounted. The drive device and compressor element are mechanically connected, wherein the feed-throughs from the pressure cylinders are sealed. This configuration means that the apparatus requires a relatively large amount of space, since the pressure cylinders are arranged in series. In addition, the configuration necessitates the use of two pistons and two feed-throughs, which are structurally complex and prone to failure with regard to tightness.
The object of the present invention is to eliminate or at least reduce the disadvantages of the prior art. Specifically, the object of the present invention is to provide a compressor device and a cooling system that minimize losses and installation space.
This object is solved by the novel compressor device disclosed herein and by a cooling device having the compressor device.
The present invention relates to a compressor device comprising a cylinder, a piston that is situated within the cylinder and that delimits a transfer space filled with a transfer fluid and which can be periodically reciprocatingly moved by means of a drive device, a compressor element, in particular a (metal) bellows, which is arranged within the transfer space and which delimits a working space/compression space filled with a working gas, and comprising a connector through which the working space can be connected to 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 by way of the transfer fluid that is displaced by the piston.
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 cryocooler is a Gifford-McMahon cooler or a pulse tube cooler. The piston is arranged inside the cylinder and 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 and is enclosed between the piston, the compressor element and the cylinder. The portion of the transfer space that contains the transfer fluid defines a fluid space whose volume remains constant. The drive device is adapted to move the piston back and forth inside the cylinder. The compressor element is disposed inside the transfer space. In one embodiment, the compressor element is a metal bellows. In one embodiment, a guiding element is adapted to guide the compressor element parallel to the central axial axis of the cylinder as the compressor element is compressed and extended. A working space that contains a working gas exists inside the compressor element. The working gas can be helium.
The working gas contained in the working space inside the compressor element is periodically and indirectly compressed by the transfer fluid as the piston periodically moves back and forth inside the cylinder. The working gas contained in the compressor element of the compressor device is periodically compressed and expanded indirectly through the displacement of the piston via the transfer fluid. 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. At any point in time as the piston periodically moves back and forth inside the cylinder, the working gas in the working space has a pressure equal to that of the transfer fluid in the transfer space.
Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.
The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.
Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.
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.
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.
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.
Furthermore, the core of the invention is that a pressure generating location (force generating location) and a compression location are configured in a cylinder.
Another core of the invention is that the piston and the compressor element are mechanically decoupled.
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.
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.
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.
In a first aspect, a volume of a space/fluid space enclosed by the piston, the compressor element and the cylinder may be constant.
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.
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.
Furthermore, the transfer space and the working space may be completely configured in the cylinder without any protrusion.
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.
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.
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.
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.
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.
In a further aspect, a maximum piston stroke may be greater than a maximum compressor-element stroke.
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.
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.
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.
In a further aspect, the compressor element may be guided in a stroke direction.
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.
In a further aspect, a closed displacer (dome element) may be configured in the working space.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
In a further aspect, a filter may be connected downstream of the compressor device.
In a further aspect, the working medium may be helium.
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.
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.
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.
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.
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.
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.
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.
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.
In one aspect, the compressor device and the Gifford-McMahon cooler or the pulse tube cooler may be connected via a high pressure connection.
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.
Furthermore, a compressor refrigeration machine may be configured with a compressor device according to one of the above aspects, an evaporator and a condenser.
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
A functional principle of the compressor device 2 according to the invention is described below with reference to
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.
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 ΔL 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.
Alternative embodiments of the compressor device 2 are explained below with reference to
The first alternative embodiment of the compressor device 2 shown in
Of course, the features of all embodiments described may be combined as desired within the claims, if technically possible.
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.
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.
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.
ΔL change in length
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022115715.6 | Jun 2022 | DE | national |
| PCT/EP2023/065892 | Jun 2023 | WO | international |
This application is filed under 35 U.S.C. § 111(a) and is based on and hereby claims priority under 35 U.S.C. § 120 and § 365 (c) from International Application No. PCT/EP2023/065892, filed on Jun. 14, 2023, and published as WO 2023/247277 A1 on Dec. 28, 2023, which in turn claims priority from German Application No. 102022115715.6, filed in Germany on Jun. 23, 2022. This application is a continuation-in-part of International Application No. PCT/EP2023/065892, which is a continuation of German Application No. 102022115715.6. International Application No. PCT/EP2023/065892 is pending as of the filing date of this application, and the United States is an elected state in International Application No. PCT/EP2023/065892. This application claims the benefit under 35 U.S.C. § 119 from German Application No. 102022115715.6. The disclosure of each of the foregoing documents is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2021/065892 | Jun 2023 | WO |
| Child | 18986722 | US |
