Abstract:
A displacement machine for compressible media has two spiral feed chambers ( 11   a   , 11   b ) which are arranged opposite each other in a fixed housing ( 7   a   , 7   b ). Spiral displacement bodies ( 2-4 ) engage in these feed chambers. Said displacement bodies essentially consist of a disk ( 2 ) and spiral strips ( 3   a   , 3   b ) which are attached to each side of the disk. The strips are held in an eccentric manner in relation to the housing, so that during operation each point on the displacement body executes a circular or elliptical movement, depending on the configuration of the guiding device ( 49 ), said movement being limited by the cylinder walls of the feed chamber. One feed chamber ( 11   a ) is configured for compressing the working substance and the other feed chamber ( 11   b ) for expanding said working substance. The feed chambers and the strips ( 3   a   , 3   b ) which engage in said chambers consist of successive circular arc segments. The radii of the circular arc segments in the compression-side feed chambers ( 11   a ) decrease in size, when viewed in a direction of rotation. The radii of the circular arc segments in the expansion-side feed chambers ( 11   b ) increase in size, when viewed in the same direction of rotation.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a displacement machine for compressible media with two spiral feed chambers which are arranged opposite each other in a fixed housing, and with spiral displacement bodies engaging in these feed chambers, consisting essentially of a central disk and of spiral strips which are attached to each side of the disk and which are held in an eccentric manner in relation to the housing, so that during operation each point on the displacement body executes a circular or elliptical movement, depending on the configuration of the guiding device, said movement being limited by the cylinder walls of the feed chamber, and so that the curvature of the strips is dimensioned such that they almost touch the inner cylinder walls and the outer cylinder walls of the feed chamber on in each case at least one sealing line per strip, said sealing line advancing continuously during operation, and, in order to guide the displacement body in relation to the housing, an eccentric arrangement is provided which essentially consists of a drive shaft and of an eccentric disk arranged thereon. 
     DESCRIPTION OF THE PRIOR ART 
     Displacement machines of the spiral structure variety are known for example from DE-C-26 03 462. Machines of this type of structure are used chiefly as compressors for gaseous media. During machine operation, a plurality of approximately sickle-shaped working chambers are enclosed along a displacement chamber between the spiral-shaped displacement body and the two cylinder walls, which working chambers move through the displacement chamber from an inlet to an outlet, their volume continuously decreasing and the pressure of the working substance correspondingly increasing. 
     A machine of the abovementioned type, in which the spirals encompass a total angle of wrap of 360° or more, is known from DE 35 14230 A1. In such a machine, the spiral strips are arranged axially projecting from both sides of a disk which has a hub for supporting the eccentric crank mechanism. Moreover, the arrangement of the spiral strips is such that, during the rotating movement of the disk, the working chambers created on both sides of the disk decrease in volume and compression of the working substance takes place. In general, the strips are arranged symmetrically with respect to the disk. 
     For working processes which are intended to be carried out at a higher pressure than the surrounding pressure and in which only a slight pressure loss occurs in the process itself, expansion machines are also used in addition to the compression machines for the purpose of exploiting the residual pressure difference, and this improves the overall degree of efficiency of the machines. Working processes which preferably operate at a higher pressure than the surrounding atmospheric pressure, and in which a relatively small drop in pressure occurs in the process, are, for example, fuel cell processes. Such processes are run using commercially available compression and expansion machines in order to maintain the high degree of efficiency of the oxidation of hydrogen in the fuel cell. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to configure a machine of the type mentioned at the outset in such a way that the working medium can be both compressed and expanded using just one displacement body revolving in a housing. 
     According to the invention, this object is achieved by the fact that one feed chamber is configured for compressing the working substance and the other opposite feed chamber for expanding said working substance, the feed chambers and the strips engaging in them consisting essentially of successive circular arc segments, the radii of the circular segments in the compression-side feed chambers and strips essentially decreasing in size, when viewed in a direction of rotation, and the radii of the circular arc segments in the expansion-side feed chambers and strips essentially increasing in size, when viewed in the same direction of rotation. 
     The spiral strips attached to both sides of the central disk of the displacement body are accordingly designed such that, in the displacement movement of the displacement body advancing during machine operation, the volume of the working chamber enclosed by these strips and by the associated feed chamber decreases on one side of the disk. On the other side of the disk, the volume of the working chamber enclosed by these strips and by the associated feed chamber increases. Compared with the solutions known from the prior art, the spiral strips attached to both sides of the central disk of the displacement body are in this case arranged asymmetrically in relation to each other. 
     The advantage of the invention is, among other things, that a very simple and therefore cost-effective construction of the machine can be achieved, since both the compression and the expansion take place using just one movable displacement element. 
     The compression-side feed chamber in general extends from a radially outward low-pressure inlet to a radially inward high-pressure outlet. If the expansion-side feed chamber now extends from a radially inward high-pressure chamber to a radially outward low-pressure outlet, the working substance on the compression side, when viewed in the radial direction, is fed counter to the direction of the working substance on the expansion side. This has the advantage that the stresses on the central disk and on the spiral strips caused by the gas pressures are approximately symmetrical on compression side and expansion side. 
     If, by contrast, the expansion-side feed chamber likewise extends from a radially outward inlet to a radially inward low-pressure chamber, the working substance on the compression side, when viewed in the radial direction, is fed in the same direction as the working substance on the expansion side. As a result, the inner ends (when viewed in the radial direction) of the spiral strips on the expansion side come to lie approximately opposite the inner ends (likewise viewed in the radial direction) of the compression-side spiral strips in relation to the central disk. The attachment of the inner ends of the spiral strips to the central disk is subjected to high stresses during machine operation and is more or less hot depending on the pressure ratio on the compression side. This arrangement has the advantage that, when such a machine is used at a high compression pressure ratio, heat can be conveyed from the inner hot end of the compression-side strip through the central disk to the cold inner end of the expansion-side strip. This arrangement is of importance when a good heat-conducting light metal is used to produce the displacement body. Use of such light materials results in a relatively low centrifugal force of the displacement component during machine operation. 
     If the hub of the disk is surrounded by a high-pressure chamber on the compression side, the hub interior is expediently closed off in an airtight manner from this high-pressure chamber by means of a closure piece. By this means, a counterweight, provided to compensate the eccentric movement of the eccentric disk and of the displacement body, can be arranged on the drive shaft advantageously in the expansion-side pressure chamber surrounding the hub. The advantage of such an arrangement is the absolute separation of the lubricant oil from the compressed air. 
     If the rotor of an electric motor driving the displacement body is arranged on a common drive shaft with the eccentric disk and the displacement body, it is expedient that an intermediate housing is attached to the housing of the electric motor, on that side of the electric motor facing away from the displacement body, into which intermediate housing protrudes the drive shaft provided with a lubricant feed device, and if a housing for a lubricant reservoir is secured on the intermediate housing. Such an arrangement with an intermediate housing is advantageous for receiving, for example, a combined reducing and synchronizing gear system which protrudes into the oil reservoir and is thus lubricated. 
     If the displacement component is guided in a known manner by a separate second eccentric arrangement, the two eccentric shafts are provided with gearwheels of identical size. These are driven and synchronized by a third gearwheel. The third gearwheel is preferably smaller and sits on the shaft of the drive motor. The latter is designed as a small rapidly rotating electric motor. The weight of the overall compressor/expander unit is thus lower compared with the use of an electric motor rotating at the same speed as the compressor/expander. 
     It is suitable for the wall of the expansion-side half of the housing to be configured in the area of the outlet in such a way that a container for receiving lubricant is formed together with the outer end of the cylinder wall of the expansion-side feed chamber, said container being connected to the lubricant circuit via external lines. Since the gases leaving the expander have a low temperature, this arrangement of the lubricant oil container at the outer end of the cylinder wall allows the lubricant to cool during machine operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A number of illustrative embodiments of the invention are represented in the drawing. Only the elements essential to an understanding of the invention are shown. The direction of flow of the various working substances is indicated by arrows. Elements having the same functions are labeled with the same reference numbers in the different figures. 
     FIG. 1 shows a longitudinal section through the displacement machine; 
     FIG. 2 shows a partial section from FIG. 1, in an enlarged representation, with the sealing of the strips on the bottom of the sickle-shaped working chambers; 
     FIG. 3 shows a transverse section through the displacement machine according to  3 — 3  in FIG. 1, with the expansion part of the displacement machine; 
     FIG. 4 shows a section through the disk of the armature of the displacement machine according to line  4 — 4  in FIG. 1; 
     FIG. 5 shows a transverse section through the compression part of the displacement machine according to lines  5 — 5  and  5 ′— 5 ′ in FIG. 1; 
     FIG. 6 shows a longitudinal section through an alternative embodiment of the displacement machine with drive motor and circuit for lubricant and coolant; 
     FIG. 7 shows a transverse section through the drive shaft along the line  7 — 7  in FIG. 6; 
     FIG. 8 shows a transverse section through the displacement machine according to line  8 — 8  in FIG. 6, with the expansion part of the displacement machine and a housing half designed as a lubricant and coolant reservoir; 
     FIG. 9 shows the principle of an alternative embodiment in which the expansion is carried out from radially outside to radially inside; 
     FIG. 10 shows the principle of an alternative embodiment according to FIG. 9, with double eccentric drive and synchronizing gearwheels. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purpose of explaining the manner of functioning of the displacement machine, reference is made to DE-C3-26 03 462 already mentioned above. There follows a brief description only of those elements of the machine construction and process which are necessary for understanding the invention: 
     The compressor/expander machine as a whole is designated by  1  in FIGS. 1 and 6. In the references, the “a” suffixes are used for the compression side, while the “b” suffixes are used for the expansion side of  1 . 
     A spirally extending displacement body is arranged on each side of the disk  2 . Said body comprises strips  3   a ,  3   b  which are held vertically on the disk  2 . In the example shown, the spiral itself is made up of a plurality of contiguous circular arcs. Reference number  4  designates a hub with which the disk  2  is mounted on an eccentric bearing  17 . FIGS. 1,  4  and  6  show the bearing  17  which sits on an eccentric disk  23  which in turn constitutes part of a drive shaft  24 . In FIG. 4, reference number  5  designates an eye which is arranged radially outside the strips  3   a ,  3   b  and receives a guide bearing  25  which is mounted on a bolt  26   a . The latter in turn constitutes part of a guiding device  49  which consists for example of an oscillating link  56 , one end of which is mounted in the housing  7   a ,  7   b  by means of bolt  26   b  and bearing  27  so as to swivel about the axis  50 . The other end engages in the eye  5  of the armature via the bolt  26   a  and the bearing  25 . 
     According to FIGS. 1,  5  and  6 , apertures  6   a  are provided at the spiral run-out on the compression side in housing half  7   a , so that the feed medium can be drawn off through the central outlet  13  arranged at one side. 
     FIG. 1 shows the machine housing  7   a ,  7   b  made up of two halves connected to each other via securing brackets  8   a ,  8   b  for receiving screw fittings  8   c . Reference number  11   a  designates the feed chamber on the compression side, which feed chamber is incorporated in the housing half  7   a  in the manner of a spiral slit. It runs parallel from a low-pressure inlet  12 , arranged on the outer circumference of the spiral in housing half  7   a , to a pressure chamber  33   a , provided in the interior of the housing, and to the high-pressure outlet  13 . The feed chamber  11   a  has one or more approximately parallel cylinder walls  51   a  which are arranged roughly at a constant distance from each other and which, in the present case, encompass a spiral like the strip  3   a  of the disk  2 . The strip  3   a  engages between these cylinder walls  51   a , the curvature of the strip  3   a  being dimensioned such that said strip  3   a  almost touches the inner cylinder wall  15   a  and the outer cylinder wall  14   a , for example at in each case one point  21   a  (FIG.  5 ). 
     FIG. 2 shows an embodiment of the lateral sealing of the strip  3   a  relative to the bottom surfaces of the spiral slit incorporated in the housing half  7   a . This is achieved, for example, by means of a contacting sealing tape  28  which is incorporated in a groove provided for this purpose in the strip  3 . 
     The drive mechanism of the disk  2  powers the drive shaft  24  via the eccentric disk  23 . The disk  2  is guided by the guiding device  49  (FIG.  4 ). Depending on whether the guiding device  49  is made up of an oscillating link  56  or of a guide shaft (not shown) running in synchronism with the drive shaft  24 , all points on the strip  3   a  execute an elliptical or a circular displacement movement with an excursion corresponding to the eccentricity “e”. The hub  4  cannot be seen in FIG. 4 since this part of the disk  2  is cut away here. The bearing  17 , with which the disk  2  is guided on the eccentric disk  23 , is represented here by way of example as a rolling bearing. 
     The multiple alternating approximation of the strip  3   a  to the inner cylinder wall  15   a  or outer cylinder wall  14   a  of the associated feed chamber  11   a  results, on both sides of the strip  3   a , in the formation of sickle-shaped working chambers which enclose the working medium and which, during operation of the disk  2 , are moved through the feed chamber  11   a  in the direction toward the pressure chamber  33   a  and the central outlet  13  communicating with the latter. The volumes of these working chambers decrease and the pressure of the working substance correspondingly increases. 
     The arrangement of the strip  3   b  on the expansion side of the machine is analogous to what has been described above. Reference number  11   b  designates the feed chamber on the expansion side, which feed chamber is likewise incorporated into the housing half  7   b  in the manner of a spiral slit. According to FIG. 3, it runs parallel from a low-pressure outlet  20 , arranged on the outer circumference of the spiral in the housing, to an inlet which is provided in the interior of the housing and which forms part of the pressure chamber  33   b  in the housing  7   b . The feed chamber  11   b  likewise has approximately parallel cylinder walls  51   b  which are arranged roughly at a constant distance from each other and which, in the present case, encompass a spiral like the strip  3   b  of the disk  2 . The strip  3   b  engages between these cylinder wails  14   b ,  15   b , the curvature of the strip  3   b  being dimensioned such that said strip  3   b  almost touches the inner cylinder wall  15   b  and the outer cylinder wall  14   b  during operation, for example at in each case one point  21   b.    
     The strip  3   b  is arranged on the disk  2  in such a way that during machine operation, as a result of the multiple alternating approximation of the strip  3   b  to the inner cylinder wall  15   b  or outer cylinder wall  14   b  of the associated feed chamber  11   b , sickle-shaped working chambers which enclose the working medium are formed on both sides of the strip  3   a . During operation of the disk  2 , these working chambers move through the feed chamber  11   b  in the direction toward the outlet  20 . By this means, the volumes of these working chambers increase and the pressure of the working substance decreases in the expander part. As a result of the expansion of the working substance located in the working chambers on the expansion side, work is applied to the strip  3   b  and thus to the eccentric disk  23 . Thus, the compression and expansion functions are combined in a single component rotating in a fixed housing  7   a ,  7   b  and made up of disk  2 , hub  4  and strips  3   a  and  3   b.    
     FIG. 5 shows the arrangement of the strips  3   a  and  3   b  arranged on both sides of the disk  2 . In accordance with the illustrated orientation of the cutting direction  5 — 5  through FIG. 1, the direction of rotation of the drive shaft  24  with the counterweight  16   a  about the center of rotation  30  is in the clockwise direction. The outer edge of the disk  2  and the strip  3   b  of the expander part are indicated by broken lines in accordance with section  5 ′— 5 ′ in FIG.  1 . For the sake of clarity, the spiral wall  51   b  in the housing half  7   b  is not shown. However, the arrangement of the strip  3   a  on the compression side relative to the strip  3   b  on the expansion side is clear. 
     In FIG. 1 the drive shaft is mounted with a journal bearing  9   a  in a bearing seat  52   a  in the housing half  7   a . The bearing seat  52   a  is connected to the housing half via ribs  29   a . The bearing is sealed off from the pressure chamber  33   a  by means of a shaft seal  33   a . The apertures  6   a  are located between the ribs  29   a . The feed medium brought to a higher pressure can leave the compressor part through these apertures. The feed medium can be delivered to a process which is not described here. 
     After this process, in which no particular drop in pressure is assumed to take place, the working substance is intended to flow via the high-pressure inlet  19  into the inner expansion-side pressure chamber  33   b  of the expander part. In housing half  7   b , the drive shaft is guided by means of a journal bearing  9   b  which is supported on housing half  7   b  via a bearing seat  52   b  with the ribs  29   b . Between the ribs are the apertures  6   b  which create the access of the working substance into the expansion-side pressure chamber  33   b.    
     The disk  2  is guided on the eccentric disk  23  via the eccentric bearing  17  onto which the hub  4  is mounted and which is sealed off from the pressure chambers  33   a  and  33   b  for example with shaft seals  18 . Reference number  31  designates the center of the eccentric disk  23 . This center is spaced apart from the center of rotation  30  by an eccentricity “e” Counterweights  16   a  and  16   b  are arranged on the drive shaft  24  and ensure a balanced operation of the machine. 
     FIG. 6 shows an alternative embodiment of the compressor/expander machine with a drive motor, preferably an electric motor. The housing  66  of the motor has threaded brackets  8   b ′ into which screw fittings  8   c  engage. Together with an intermediate housing  54  on the expansion side and the housing halves  7   a  and  7   b , the compressor/expander machine  1  is connected to the electric motor to form one machine. 
     The working substance to be expanded must be guided, at the inlet side of the intermediate housing  54 , in a way which takes account of the fact that the working substance in the expansion part of the compressor/expander machine flows from the inside outward, when viewed in the radial direction; it must be guided in toward the center of the expansion side of the displacement machine. The schematically illustrated solution shows that the working substance enters the intermediate housing  54  at the high-pressure inlet  55  and passes through apertures  99  into an annular chamber  32 . On the side of the compressor/expander machine  1 , this chamber  32  is sealed off from the surrounding pressure prevailing in the interior  63  of the electric motor housing by means of the shaft  24  with a journal bearing  58 , and on the electric motor side it is sealed off by means of a shaft seal  62 . The shaft seal  62  engages on a thickening  44  arranged on the drive shaft. The annular chamber  32  is connected to the pressure chamber  33   b  via apertures  57  in the shaft  24 , so that the working substance to be expanded can pass into the interior  33   b  of the expander part. 
     The passage of the working substance through the apertures in the shaft  24  is expedient for the reason that the whole drive shaft with the rotor  64  of the electric motor is guided only with two journal bearings  58 ,  93 . In addition, in contrast to the embodiment according to FIG. 1, only one counterweight  16  is to be arranged on the shaft  24 , on the expansion side to be precise. To ensure the flexural strength of the drive shaft  24  needed for stable running of the machine, said drive shaft  24  is given a relatively large diameter in the area of the journal bearing  58 . The arrangement of apertures  57  (see also FIGS. 7 and 8) in the rigid part is expedient for introduction of the working substance which is to be expanded. 
     In the example shown in FIG. 6, the journal bearing  58  is designed as a rolling bearing on whose outer ring a positioning ring  59  is attached, which lies in a depression incorporated for example in the housing half  7   b  and is clamped by the intermediate housing  54 . On the drive shaft  24 , the inner ring of the rolling bearing  58  bears on one side on a collar  82  and on the other side on a ring  83 . By means of this arrangement, the drive shaft  24  is guided axially in relation to the housing parts  7   a ,  7   b ,  54  and  66 . 
     On that side of the electric motor remote from the compressor/expander unit  1 , said electric motor consisting essentially of the housing  66  and the rotor  64 , there is a lubricant container  68  with the lubricant reservoir. A device which generates a stream of lubricant for lubricating and cooling the highly stressed eccentric bearing  17  is necessary because the compressor/expander machine is intended to be of small size in relation to the delivered stream of working substance and thus to be operated at high speed. This results in the aforementioned high stressing of the eccentric bearing  17 . The lubricant circuit is as follows. 
     The container  68  surrounds a housing  71  which receives the journal bearing  93  of the shaft  24  facing away from the compressor/expander unit. Moreover., in the housing  71 , a lubricant feed device  72  (not described here) is mounted on the drive shaft  24  and driven by the latter. This lubricant feed device  72  suctions the lubricant from the reservoir  69  via a suction line  79  and feeds it at high pressure into a chamber  73 . 
     In the shaft  24  common to the rotor  64  and to the compressor/expander machine  1 , an insert  75  is introduced into a central bore  76 , which insert  75  for its part has a central feed bore  74 . The latter is connected to the chamber  73  on the side of the lubricant reservoir. On the side of the compressor/expander unit  1 , the feed bore  74 ′ is connected to a bore  88  arranged radially in the eccentric disk  23 . At its radially outer end, the bore  88  opens directly into the eccentric bearing  17  and supplies the latter with lubricant. In FIG. 6, this bearing is designed as a plain bearing; a plain bearing bush  17 ′ is let into the hub  4 . 
     The hub  4  is sealed off from the chamber  33   a  and the outlet  13  by means of a closure piece  60 . This closure piece ensures complete separation of the lubricant from the working substance. The working substance can thus be fed completely free of lubricant. This is in contrast to the embodiment according to FIG. 1 in which the arrangement of the shaft seals  10   a  and  18  can lead, on the compression side, to lubricant escaping into the chamber  33   a ; shaft seals cannot ensure complete sealing. 
     The lubricant can pass from the eccentric bearing  17  into the chamber  80  formed by the closure piece  60 . The lubricant passes from the opposite side of the bearing  17  into an annular chamber  53   c  which is sealed off from the expansion-side pressure chamber  33   b  by means of a shaft seal ring  18 . The lubricant collection chambers  53   c  and  80  are connected in each case via a bore  81  to the lubricant return channel  77  in the shaft  24 . This channel is created by an insert  75  which in its central part is recessed on the outer circumference. In FIG. 7, the recessed portion of the insert  75  is shown in cross section (section  7 — 7  in FIG. 6) and this figure shows, in addition to the center of rotation  30  of the shaft  24 , the feed bore  74 , the annular lubricant return channel  77 , and the central bore  76  for the insert  75 . A radial bore  77   c  is incorporated in the shaft  24  on the side of the lubricant reservoir  69 . The lubricant can pass through this bore into an annular collection chamber  45 . The collection chamber  45  is incorporated in the housing  66  and is formed together with a shaft seal ring  78  and the feed pump housing of the lubricant feed device  72 , and the shaft  24 . Arranged in the housing  66  there is a bore  90  through which the returning lubricant can flow back into the reservoir  69 . 
     The compression of the gaseous working substance (e.g. air) results in a temperature increase in the chamber  33   a  compared with the temperature prevailing in the low-pressure inlet  12 . The higher temperature in the chamber  33   a  acts on the hub portion  4  with closure piece  60  rotating in this chamber. In addition to its primary role of lubricating the bearing  17 , the lubricant also has the role of carrying off heat from the hub portion  4  with closure piece  60 . As has been described above, the lubricant flowing back into the reservoir  69  must be able to give off its accumulated heat there, for example to the environment. 
     An embodiment for heat removal is likewise represented in FIG.  6 . Corresponding to the prior art, electric motors often have a blower wheel  67  which, in the present example, is mounted on the shaft  24 . Through apertures  65  in the housing  66 , the cooling air stream  85  passes into the interior of the electric motor and, depending on the strength of the cooling air stream  85  generated by the blower wheel  67 , experiences a greater or lesser increase in temperature. Assuming that the blower wheel is made powerful enough, this affords an advantageous embodiment for cooling the lubricant in the reservoir container  68 . By diverting the cooling air stream via air guide means  84 , this stream is conveyed past the cooling surfaces  70 , which are arranged on the container  68 , and takes up further heat from the container  68 . 
     An alternative embodiment for removing heat from the lubricant is represented in FIG.  8 . The drawing shows diagrammatically a wall part  94  of the housing  7   b , which wall part  94  is designed such that a container  95  is obtained. This container is located in the area of the outer end  98  of the cylinder wall  51   b , when viewed in the flow direction. The lubricant is delivered to and removed from the container  95  via external lines  96 ,  97  (not described in detail) which can be connected to a lubricant feed device  72 , as is represented in FIG.  6 . This arrangement exploits the fact that the temperature decreases upon expansion of the gaseous working substance. 
     When the compressor/expander machine  1  is used, for example, on fuel cells, the temperature at the inlet of the working substance into the chamber  33   b  is relatively low, assuming that no special devices are used which increase the temperature of the working substance in the high-pressure inlet  19  or  55 ,  33   b  of the expansion machine. Such devices can consist, for example, of heat exchanger which give off the heat of the compressed air after the outlet  13  to the working substance to be expanded before the inlet  19  or  55 ,  33   b  and heat this in order to increase the expansion performance. 
     Since water is an essential oxidation product in fuel cell use, the working substance being enriched with water before the expansion process, it must be assumed that the temperature will drop considerably below the dew point toward the low-pressure outlet  20  and, depending on the starting temperature of the expansion, will also be below the freezing point. If no special measures are taken, ice is able to form in the area of the cylinder walls  98  during machine operation. 
     This is avoided by the fact that the part around the outlet  20 ,  98  is used to apply the lubricant reservoir  95  there. On the one hand, the latter is cooled by this measure, and, on the other hand, ice formation at  20 ,  98  is prevented. 
     FIG. 9 shows an illustrative embodiment in which the expansion of the working substance takes place from radially outside to radially inside. In contrast to the expansion shown in FIGS. 1,  3  and  6 , the high-pressure gas flows through an opening  55  into the high-pressure chamber  33   b . The expanded gas flows out of the low-pressure interior of the expander part through apertures  57  in the shaft  24 . 
     The invention is of course not limited to the machine shown and described above. In the case where two separate eccentric arrangements are used for guiding the displacement body, the electric motor can engage, not on the drive shaft  24 , but instead between two shafts with separate axes of rotation  30  and  104 . Such an arrangement is shown in FIG.  10 . For the sake of clarity, this shows only the displacement body consisting of the disk  23  and the strips  3   b  with the wheel gearing. The latter consists of a drive wheel  100 , a wheel  101  on the drive motor  110 , and a synchronizing wheel  102 . Reference number  103  designates a toothing on the wheel. Identical toothing is also provided for the wheels  101  and  102  but is not shown here. The axis of the drive motor is indicated by  108 , that of the eccentric guiding arrangement is indicated by  104 . The central disk  23  has, for example, a known radially elastic and tangentially rigid attachment  105  to the eye  106 . The eye  106  has its center point at  107  which, during machine operation, rotates round the center of rotation  104  with the eccentricity “e”. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 LIST OF REFERENCE NUMBERS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                 compressor/expander 
               
               
                   
                 2 
                 disk 
               
               
                   
                 3a, 3b 
                 strips, displacement bodies 
               
               
                   
                 4 
                 hub 
               
               
                   
                 5 
                 eye 
               
               
                   
                 6a 
                 aperture in 7a 
               
               
                   
                 6b 
                 aperture in 7b 
               
               
                   
                 7a, 7b 
                 housing half 
               
               
                   
                 8a, 8b, 8b′ 
                 securing bracket 
               
               
                   
                 8c 
                 securing screw 
               
               
                   
                 9a 
                 journal bearing for 24 in 7a 
               
               
                   
                 9b 
                 journal bearing for 24 in 7b 
               
               
                   
                 10a, 10b 
                 shaft seals of 24 
               
               
                   
                 11a 
                 feed chamber in 7a 
               
               
                   
                 11b 
                 teed chamber in 7b 
               
               
                   
                 12 
                 low-pressure inlet 
               
               
                   
                 13 
                 high-pressure outlet 
               
               
                   
                 14a 
                 outer cylinder wall of 11a 
               
               
                   
                 14b 
                 outer cylinder wall of 11b 
               
               
                   
                 15a 
                 inner cylinder wall of 11a 
               
               
                   
                 15b 
                 inner cylinder wall of 11b 
               
               
                   
                 16, 16a, 16b 
                 counterweights on 24 
               
               
                   
                 17, 17′ 
                 eccentric bearings between 4 and 23 
               
               
                   
                 18 
                 shaft seals of 23 
               
               
                   
                 19 
                 high-pressure inlet 
               
               
                   
                 20 
                 low-pressure outlet 
               
               
                   
                 21a, 21b 
                 sealing line in 7a, 7b of 11a, 11b 
               
               
                   
                 22 
                 rib 
               
               
                   
                 23 
                 eccentric disk 
               
               
                   
                 24 
                 drive shaft 
               
               
                   
                 25 
                 guide bearing in 56 on 26a 
               
               
                   
                 26a 
                 guide bolt in 2 
               
               
                   
                 26b 
                 guide bolt between 7a, 7b 
               
               
                   
                 27 
                 guide bearing in 56 on 26b 
               
               
                   
                 28 
                 sealing tape 
               
               
                   
                 29a, 29b 
                 rib 
               
               
                   
                 30 
                 center of rotation of 24 
               
               
                   
                 31 
                 center of 23 
               
               
                   
                 32 
                 annular chamber between 58 and 62 
               
               
                   
                 33a 
                 pressure chamber in 7a (compressor side) 
               
               
                   
                 33b 
                 pressure chamber in 7b (expander part) 
               
               
                   
                 44 
                 collar for 62 on 24 
               
               
                   
                 45 
                 annular collection chamber 
               
               
                   
                 49 
                 guiding device 
               
               
                   
                 50 
                 center axis of 26b 
               
               
                   
                 51a, 51b, 51b′ 
                 strips in 7a, 7b 
               
               
                   
                 52a, 52b 
                 bearing seat in 7a, 7b 
               
               
                   
                 53a 
                 bearing interior of 9a 
               
               
                   
                 53b 
                 bearing interior of 9b 
               
               
                   
                 53c 
                 bearing interior of 17 
               
               
                   
                 54 
                 intermediate housing 
               
               
                   
                 55 
                 high-pressure inlet 
               
               
                   
                 56 
                 oscillating link 
               
               
                   
                 57 
                 aperture in 24 
               
               
                   
                 58 
                 bearing 
               
               
                   
                 59 
                 clamping ring between 54 and 7b 
               
               
                   
                 60 
                 closure disk on 4 
               
               
                   
                 61 
                 high-pressure intermediate chamber 
               
               
                   
                 62 
                 shaft seal between 61 and 63 
               
               
                   
                 63 
                 interior of electric motor 
               
               
                   
                 64 
                 rotor of electric motor 
               
               
                   
                 65 
                 apertures in 66 
               
               
                   
                 66 
                 housing of the electric motor 
               
               
                   
                 67 
                 blower wheel on 24 
               
               
                   
                 68 
                 housing of 69 
               
               
                   
                 69 
                 lubricant reservoir, lubricant 
               
               
                   
                 70 
                 cooling surface 
               
               
                   
                 71 
                 bearing housing 
               
               
                   
                 72 
                 feed pump for 69 
               
               
                   
                 73 
                 pressure chamber of 69 
               
               
                   
                 74, 74′ 
                 pressure line for 69 in 24 
               
               
                   
                 75, 75′ 
                 insert in 24 
               
               
                   
                 76 
                 bore in 24 
               
               
                   
                 77, 77c 
                 lubricant return channel in 24 
               
               
                   
                 78 
                 shaft seal 24, rear 
               
               
                   
                 79 
                 suction line for 69 
               
               
                   
                 80 
                 low-pressure chamber between 60 &amp; 23 
               
               
                   
                 81 
                 low-pressure lines in 23 to 77 
               
               
                   
                 82 
                 shoulder on 24 for 58 
               
               
                   
                 83 
                 positioning ring on 24 for 58 
               
               
                   
                 84 
                 guide means for 85 
               
               
                   
                 85 
                 cooling air stream 
               
               
                   
                 86 
                 screw fitting for 68 
               
               
                   
                 87 
                 filler attachment for 69 with lid 
               
               
                   
                 88 
                 connection between 74 &amp; 17 in 23 
               
               
                   
                 89 
                 screw fitting of 71 to 66 
               
               
                   
                 90 
                 low-pressure outlet in 66 to 69 
               
               
                   
                 93 
                 bearing of 24 in 71 
               
               
                   
                 94 
                 outer wall of 95 
               
               
                   
                 95 
                 lubricant chamber 
               
               
                   
                 96 
                 lubricant return flow 
               
               
                   
                 97 
                 lubricant feed 
               
               
                   
                 98 
                 end portion of 51b 
               
               
                   
                 99 
                 aperture in 54 
               
               
                   
                 e 
                 eccentricity; radial spacing between the 
               
               
                   
                   
                 axis of rotation 30 of 24 and the center 
               
               
                   
                   
                 31 of 23 
               
               
                   
                 100 
                 drive wheel on drive shaft 24 
               
               
                   
                 101 
                 drive wheel on drive motor 
               
               
                   
                 102 
                 synchronizing wheel on second eccentric 
               
               
                   
                   
                 arrangement 
               
               
                   
                 103 
                 toothing 
               
               
                   
                 104 
                 center of rotation of the second 
               
               
                   
                   
                 eccentric arrangement 
               
               
                   
                 105 
                 radially elastic, tangentially rigid 
               
               
                   
                   
                 attachment to 23 
               
               
                   
                 106 
                 eye on 105 
               
               
                   
                 107 
                 center of the second eccentric 
               
               
                   
                   
                 arrangement 
               
               
                   
                 108 
                 center of rotation of the laterally 
               
               
                   
                   
                 built-on drive motor 
               
               
                   
                 109 
                 inner end of 3b in FIG. 10