EP2122169B1 - Fluid machine - Google Patents

Description

The invention relates to a fluid working machine for compressing or conveying fluids, in particular for compressing gases to high pressures, with a linear motor, at least one cylinder, a solid-state piston axially movable in the cylinder, at least one between the cylinder and the solid-body piston or the liquid piston formed compression space, and valves for the inlet and the outlet of the fluid, which are arranged in the region of the at least one compression space, wherein the linear motor transmits a translational driving force to the solid-state piston and the solid-state piston is enclosed in the region of the linear motor of a fixed can, so in that a cylinder interior is formed between the solid-body piston and the can.

Fluid power machines are known in various embodiments and variants of the prior art. The fluid working machines can be subdivided first according to whether they are provided for conveying or compressing liquids or gases. Fluid power machines used to convey fluids are also commonly referred to as pumps, while fluid power machines are referred to as compressors for compressing gases. In addition, fluid working machines can also be distinguished by the type of drive force - hydraulic, electric or electro-magnetic - as well as the type of drive movement - rotational or translational.

The present invention relates to a fluid working machine in which the driving force is generated by a linear motor which exerts a translational driving force on a piston guided in a cylinder directly, that is, without converting a rotational movement via a gear. If a gas is to be compressed with such a fluid working machine, then the machine can also be referred to as a piston compressor or as a linear compressor. The linear motor consists essentially of a stator or stator and a rotor or actuator, wherein the linear motor as well as a rotating motor may be formed as an asynchronous or synchronous linear motor. The linear motor then corresponds to a developed asynchronous motor with a squirrel-cage rotor or a permanently excited synchronous motor, wherein a traveling field is generated by the coil or winding of the stator instead of a rotating field. The power transmission takes place, as in induction machines, either by voltage induction in the squirrel-cage rotor of the asynchronous motor or by interaction with the field of the permanent magnets of the synchronous motor.

From the DE 10 2004 055 924 A1 a previously described linear compressor is known in which the magnet of the rotor is fixed to a magnetic frame which is fixedly mounted on an end face of the piston. In the known linear compressor, a cooling channel is provided for cooling the linear motor, by which the coil of the stator mounted on a coil holder is cooled with a coolant. For this purpose, a pump is provided which promotes oil within a hermetically sealing the linear compressor container through the cooling channel to the coil or the bobbin holder. The returning oil is collected in the lower part of the hermetically sealed container.

From the DE 102 14 047 A1 a compressor for a motor vehicle air conditioner with a closed refrigerant circuit is known, which has a compressor housing with a compression space formed therein and a reciprocable in this reciprocating piston, in which a linear motor with variable drive frequency is used as the drive for the compressor to whose reaction part is attached to the compressor chamber side end face of the reciprocating piston. The well-known compressor is simple, consists of only a few components and is relatively small-sized. Storage, lubrication and sealing problems should - at least at a pressure level on the high pressure side between 80 and 160 bar - not occur. The sealing of the reciprocating piston with respect to the compression space wall by means of conventional ring seals on the reciprocating piston. Since in such a moving seals at least over time, in principle occur leaks to the atmosphere, which is from the DE 102 14 047 A1 known compressor at least not suitable for compression to high pressures (> 150 bar) and not provided.

The DE 198 46, 711 C2 discloses a high-pressure pump with a solenoid-linear motor, the bobbin on an inner space sealingly enclosing, high-pressure-resistant, non-magnetic sleeve is seated, which is clamped between two housing flanges. The housing flanges carry on their outer side to the longitudinal axis of the bobbin aligned spinning cylinder, in which a located in the interior of the sleeve Permanentmagnetstab is arranged, at its over the bobbin and the sleeve beyond both ends in each case a pressure piston is arranged. Through the sleeve, the interior is hermetically sealed. From the seals of the pressure piston transmitted leakage flows into the interior, flows around the permanent magnet rod and builds up a back pressure, so the expensive high-pressure seals between the pressure piston and the pressure cylinders can be omitted

The US 3,196,797 A discloses a compressor having a linear motor, a cylinder and two pistons axially movable in the cylinder, which are connected to each other via a piston rod having a wider core. Within the cylinder channels are formed through which the liquid can pass from the inlet to the adjoining the piston compression chambers in the cylinder. In the from the US 3,196,797 A known compressor, the inlet for the liquid to be compressed is provided in the middle of the linear motor between two coil halves, to which a tube is made via a hollow ring between the two coil halves and connected to the channels.

The DE 29 37 157 A1 discloses a Kolbenverdrängerpumpe with two displacer, which are connected to each other via a piston rod and slidably disposed in a cylinder back and forth. The inlet and the outlet of the liquid via valves which are arranged laterally to the delivery-side cylinder head. The known piston displacement pump has a split tube within which the inner body of a magnetic coupling is located. Outside the can, the outer body of the magnetic coupling is arranged. The inner body in this case has a relief bore, which serves to ensure the mobility of the piston rod and the two pistons by leakage liquid from one side of the inner body through the relief hole to the other side of the inner body can flow.

The DE 103 14 007 A1 discloses a piston vacuum pump having a linearly guided piston and a piston driving the controllable magnet assembly having two acted upon by switchable excitation currents, the piston driving working coils.

Initially, it is stated that the fluid working machine has a solid-state piston that is axially movable in the cylinder. In the context of the invention, a solid-state piston should be understood to mean (conventional) solid or solid (metal) pistons, as they have been known for a long time. The compressors described above have such solid-state pistons.

A fluid working machine with a liquid piston is for example from DE 10 2004 046 316 A1 In the case of the compressor disclosed there, an ionic liquid is preferably used, so that the compressor is also referred to as an "ionic compressor". The known compressor has two interconnected cylinders, in each of which a liquid and the gas to be compressed are located. By means of a hydraulic pump, the liquid levels in the two cylinders are varied so that one of the cylinders sucks the gas to be compressed, while in the other cylinder, a compression of the gas takes place.

The present invention has for its object to provide an initially described fluid working machine for compressing or conveying fluids available, the simplest possible structure a leakage and possibly also lubricant-free compression or delivery of fluids, in particular a compression of gases to high Pressures, allows.

This object is achieved in the above-described fluid work machine with the features of claim 1, characterized in that the compression chamber connected to the can is connected via a conduit or a channel to the fluid inlet side, so that the pressure in the cylinder interior surrounding the can is reduced.

According to the invention, the compression chamber connected to the can is connected to the fluid inlet side via a conduit or a channel formed in the cylinder or in the housing. H. connected to the suction side of the fluid work machine. By this measure, the pressure in the region of the can is reduced to the low pressure at the fluid inlet side. Internal leaks that occur along the moving piston seals are released to the suction pressure and discharged to the fluid inlet side. As a result, the required wall thickness of the split tube can be reduced, thereby reducing the electrical losses in an arrangement of the can between the rotor and the coil of the stator. An otherwise required at particularly high pressures thick or double-walled design of the can can be eliminated. Irrespective of this, however, the use of a double-walled split tube is possible in order to increase safety, in particular in the case of particularly dangerous gases (toxic, polluting or radioactive gases).

The arrangement of a split tube can be achieved in a simple way, the freedom from leaks to the atmosphere. The leakage occurring when sealing the solid-state piston to the drive and thus to the atmosphere of moving seals due to the principle are avoided by the can. The arrangement of the split tube can be sealed to the atmosphere only with static seals.

According to a first advantageous embodiment of the invention, the can is arranged in the radial direction between the rotor and the coil of the stator, so that the can encloses the rotor. In this embodiment, the split tube is thus between the stator and the rotor. According to an alternative embodiment of the invention, both the rotor and the coil of the stator are arranged within the can, so that the can encloses the rotor and the stator.

In the first embodiment, the can thus serves as a partition between the electric drive system and the fluid-contacting compression chamber or the moving solid-state piston, wherein the can is penetrated by the magnetic field for energy transfer. This leads to electrical losses as a result of eddy currents in the can and to a heating of the can, so that the efficiency of a linear motor with a gap tube arranged therebetween is lower than the efficiency of a linear motor with an outer gap tube. This disadvantage of greater losses does not occur in the second embodiment in which the can encloses the rotor and the stator. This embodiment is thus - at least theoretically - advantageous unless it is to be compacted with the fluid working machine aggressive media. In this case, the coil would also be exposed to the aggressive medium in the outer split tube, which can lead to an impairment of the life of the coil.

The fluid working machine according to the invention can advantageously be constructed simply by arranging the magnets of the rotor directly on the piston. By attaching the magnets of the rotor directly on the piston eliminates the formation and arrangement of a separate magnetic frame. In addition, the radial dimensions of the fluid working machine, in particular of the cylinder can be reduced by this configuration.

According to a further preferred embodiment of the invention, the fluid working machine is designed in multiple stages, d. H. the compression of a gas takes place in at least two, preferably in four stages. Alternatively, a single-stage compression is possible, in which case preferably a compensation stage is provided in order to keep the resulting forces necessary for the compression low. If the compression of the gas in several stages, it is advantageously provided that the solid-state piston has a plurality of sections with different diameters. The piston can be composed manufacturing technology of several piston sections.

To reduce electrical losses that may occur through the use of the can, it is also possible to make the can not made of metal but of a plastic or ceramic. When selecting the plastic or the ceramic care must be taken to ensure that the canned pipe can withstand the maximum occurring pressure safely.

According to a further embodiment of the invention is - as basically known in the art - at least one heat exchanger for recooling the fluid provided. In a multistage fluid working machine, such a heat exchanger is preferably arranged after each compression stage. The coolant required for the recooling of a gas through the heat exchanger can then preferably also be used for cooling the linear motor. The cooling is preferably carried out from the outside, d. H. via a housing surrounding the linear motor, so that neither the rotor nor the stator comes into direct contact with the coolant. As an alternative to the use of a separate coolant, the fluid itself can be used both for re-cooling the fluid and for cooling the linear motor, provided that this is present in a correspondingly cold state. If the gas to be compressed, for example hydrogen, is present in the liquid phase before deep-freezing, then the gas can be used as coolant in the liquid phase.

The above-described fluid working machine according to the invention is particularly suitable for the compression of gases to high pressures, in particular for the compression of hydrogen to 500 bar or more. Thus, such a linear compressor is particularly suitable for the equipment of hydrogen refueling stations.

Fig. 1

ein erstes Ausführungsbeispiel einer erfindungsgemäßen Fluidarbeitsmaschine,

Fig. 2

eine vergrößerte Darstellung des Teilbereichs A der Fluidarbeitsmaschine gemäß Fig. 1,

Fig. 3

ein zweites Ausführungsbeispiel einer erfindungsgemäßen Fluidarbeitsmaschine,

Fig. 4

eine vergrößerte Darstellung eines Teilbereichs der Fluidarbeitsmaschine gemäß Fig. 3, und

Fig. 5

ein drittes Ausführungsbeispiel einer erfindungsgemäßen Fluidarbeitsmaschine.

In particular, there are a variety of ways to design and develop the fluid working machine according to the invention. Reference is made to the claims subordinate to claim 1 and to the description of preferred embodiments in conjunction with the drawings. In the drawing show

Fig. 1

A first embodiment of a fluid working machine according to the invention,

Fig. 2

an enlarged view of the portion A of the fluid working machine according to Fig. 1 .

Fig. 3

A second embodiment of a fluid working machine according to the invention,

Fig. 4

an enlarged view of a portion of the fluid working machine according to Fig. 3 , and

Fig. 5

A third embodiment of a fluid working machine according to the invention.

The Fig. 1 . 3 and 5 show three different embodiments of a fluid working machine 1 according to the invention, wherein the figures are only simplified representations, so that only the essential components for the present invention are shown. The fluid working machines 1 shown in the figures serve to compress gases, in particular hydrogen, to a high pressure of, for example, 500 bar. Such fluid working machines 1 can therefore be used advantageously in particular for equipping hydrogen refueling stations.

The in the Fig. 1 . 3 and 5 1 each have a linear motor 2 for driving a solid-state piston 4 movably arranged in a cylinder 3. By using the linear motor 2 as a drive, a translatory drive force is exerted on the solid-state piston 4, so that the solid-state piston 4 can move axially back and forth within the cylinder 3, 3 '. Within the cylinder 3 is at least one compression space 5, for the gas to be compressed, wherein the size of the compression space 5 changes depending on the position of the solid-state piston 4.

In the two embodiments according to the Fig. 1 and 3 the fluid working machine 1 is formed in a total of 4 stages, so that the compression of the gas takes place in four successive stages. Accordingly, in these two embodiments, four sections 41, 42, 43, 44, each having different diameters, are formed on the solid-body piston 4. Corresponding thereto, the cylinder 3, 3 'has four different sections with different inner diameters, so that a total of four compression chambers 5 are formed. In contrast, the fluid working machine 1 according to Fig. 5 trained only one stage, but this is a double-acting fluid working machine 1, so that on Both sides of the solid-state piston 4 each have a compression space 5 is formed.

All three embodiments have in common that the solid-state piston 4 is enclosed in the region of the linear motor 2 by a fixedly arranged can 6. The arrangement of the can 6 ensures a secure sealing of the cylinder interior 7, so that overall the desired freedom from leaks of the fluid power tool 1 is achieved in a simple manner. The freedom from leaks to the atmosphere no longer has to be realized by the piston seals 8 arranged on the solid-body piston 4, which due to their arrangement and design as moving seals inherently can not or can not ensure permanent, and in particular non-lubricant-free, sealing properties. The usual implementation of the piston rod to the drive thus eliminated, as well as the required moving sealing systems. The-leakage to the atmosphere is thus ensured only with static seals 18.

The in the FIGS. 1 to 5 shown linear motor 2 has a stator with a coil 9 and a rotor with a plurality of magnets 10, wherein the magnets 10 are arranged directly on the solid-state piston 4.

In the embodiment according to Fig. 1 or according to the enlarged view in FIG Fig. 2 is the can 6 in the radial direction between the rotor, that is, the magnet 10 and the coil 9 of the stator arranged so that the can 6 not only the solid-state piston 4 but also the magnets 10 of the rotor encloses. In this embodiment, the can 6 is thus between the stator and the rotor, so that the can 6 is penetrated by the magnetic field. In contrast, in the embodiment according to Fig. 3 or according to the enlarged view in FIG Fig. 4 Both the rotor, that is, the magnets 10 and the coil 9 of the stator disposed within the can 6. In this embodiment, therefore, not only the magnets 10 but also the coil 9 are exposed to the fluid, which despite the piston seal 8 enters the cylinder interior 7 in the region of the can 6.

In the Fig. 1 . 3 and 5 is indicated that the connected to the can 6 compression space 5 is connected via a line 11 to the fluid inlet side 12 of the fluid power machine 1. As a result, internal leaks, which occur in spite of the piston seals 8 between the outer circumference of the solid-body piston 4 and the inner wall of the cylinder 3, are released to the suction pressure and discharged to the fluid inlet side 12. As a result, the pressure in the space surrounded by the can 6 cylinder interior 7 is reduced, whereby the can 6 in the embodiment according to the Fig. 1 and 2 or the coil 9 and the can 6 in the embodiment according to the Fig. 3 and 4 not be unnecessarily burdened. By thus reducing the pressure in the cylinder inner space 7 surrounded by the can 6, a correspondingly smaller wall thickness can be selected for the can 6, which results in a reduction of eddy current losses occurring in the can 6.

Alternatively, the compression chamber 5 connected to the can 6 may also be connected directly to the fluid inlet side 12, d. H. the fluid inlet takes place in the compression space 5 connected to the can 6. If the fluid to be compressed has a low temperature, cooling of the linear motor 2 can take place at the same time.

As is known in the art, the inlet and the outlet of the gas to be compressed via valves 13, which are arranged in the region of the individual compression chambers 5 and preferably formed as a plate valves. By the applied differential pressures between the compression chamber 5 and the respective inlet and outlet then takes place an automatic opening or closing of the valves 13. Since in the two embodiments according to the Fig. 1 and 3 a four-stage compression of the gas takes place, the fluid working machines 1 also four intake and exhaust valves 13, respectively.

In the Fig. 1 and 3 is also indicated that the individual compression chambers 5 are connected to each other via lines 14, wherein in the individual lines 14 each have a heat exchanger 15 is provided for recooling the compressed gas. In addition, in the Fig. 1 . 3 and 5 still indicated that the fluid work machine 1 a coolant circuit 16 for cooling the coil 9 of the stator and thus for cooling the linear motor 2 has a total. The cooling takes place from the outside, that is, via a housing 9 surrounding the coil 9, so that the coil 9 does not come into direct contact with the coolant. Both for re-cooling of the compressed gas in the heat exchangers 15 and for cooling the linear motor 2 while the same coolant can be used.

Finally, it is still apparent from the figures that the illustrated embodiments of the fluid power machine 1 each have two cylinders 3; 3 ', wherein the linear motor 2 with the split tube 6 or the housing surrounding the linear motor 17 between the two cylinders 3, 3' is arranged. The sealing between the end faces of the two cylinders 3, 3 'and the corresponding end faces of the housing 17 takes place via static seals 18th

The Fig. 3 and 4 In addition, it is also possible to remove that the electrical leads 19 to the arranged inside the can 6 with the help of pressure-tight cable bushings 20 are leak-free led to the connection box 21, wherein the terminal box 21 pressure-tight cable glands 20, so that the freedom gained by the can 6 leakage the atmosphere is not canceled by the connection of the required lines 19.

The fluid working machines 1 shown in the figures are particularly suitable for compressing gases, preferably hydrogen, to high pressures of, for example, 1000 bar, so that such fluid working machines 1 are particularly suitable for equipping hydrogen refueling stations.

Claims (9)

1. Fluid working machine for compressing and/or conveying fluids, in particular for compressing gases to high pressures, having a linear motor (2), at least one cylinder (3), a solid piston (4) which can be moved axially in the cylinder (3), at least one compression space (5) which is formed between the cylinder (3) and the solid piston (4), and valves (13) for the entry and the exit of the fluid, which valves (13) are arranged in the region of the at least one compression space (5), wherein the linear motor (2) transfers a translational driving force to the solid piston (4), and the solid piston (4) being enclosed in the region of the linear motor (2) by a fixedly arranged split pipe (6), so that a cylinder interior space (7) is configured between the solid piston (4) and the split pipe (6),
   characterized in
   that the compression space which is connected to the split pipe (6) is connected via a line (11) or a duct to the fluid entry side (12), so that the pressure is reduced in the cylinder interior space (7) which is surrounded by the split pipe (6).
2. Fluid working machine according to Claim 1, the linear motor (2) having a stator and a rotor, characterized in that the split pipe (6) is arranged in the radial direction between the rotor and the coil (9) of the stator, so that the split pipe (6) encloses the rotor.
3. Fluid working machine according to Claim 1, wherein the linear motor (2) having a stator and a rotor, characterized in that both the rotor and the coil (9) of the stator are arranged within the split pipe (6), so that the split pipe (6) encloses the rotor and the stator.
4. Fluid working machine according to Claim 2 or 3, the rotor having magnets (10), characterized in that the magnets (10) of the rotor are arranged directly on the piston (4).
5. Fluid working machine according to one of Claims 1 to 4, characterized in that the compression of a gas takes place in multiple stages.
6. Fluid working machine according to Claim 5, characterized in that the solid piston (4) has a plurality of sections (41, 42, 43, 44) with different diameters.
7. Fluid working machine according to one of Claims 1 to 6, characterized in that a coolant circuit (16) is provided for cooling the linear motor (2), in particular for cooling the coil (9) of the stator.
8. Fluid working machine according to one of Claims 1 to 7, characterized in that at least one heat exchanger (15) is provided for re-cooling the fluid.
9. Fluid working machine according to Claims 7 and 8, characterized in that the same coolant or the fluid to be compressed is used to cool the linear motor (2) and to recool the fluid..

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