Abstract:
The invention relates to a compressor for refrigerant, comprising: an outer housing; a scroll compressor which is disposed in the outer housing; an outlet, which is located in the base of the stationary compressor body and which leads to a high pressure chamber in the outer housing, and; a check valve, which has a valve body and which is disposed between the outlet and the high pressure chamber. The aim of the invention is to improve a compressor of the type described at the beginning in such a way as to ensure that the function of the check valve is as optimal as possible. To this end, the invention provides that the outlet having a center axis which is offset with respect to a center axis of the valve seat for the valve body in a transverse direction in relation to the center axis.

Description:
[0001]     This application is a continuation of international application No. PCT/EP2003/009214 filed on Aug. 20, 2003.  
         [0002]     The present disclosure relates to the subject matter disclosed in international application No. PCT/EP2003/009214 of Aug. 20, 2003 and German application number 102 48 926.2 of Oct. 15, 2002, which are incorporated herein by reference in their entirety and for all purposes. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     The invention relates to a compressor for refrigerant, comprising an outer housing, a scroll compressor which is disposed in the outer housing and has a first compressor body, which is fixedly disposed in the outer housing, and a second compressor body, which is movable in relation to the first compressor body, each of these bodies having a base and respective first and second scroll ribs, which rise above the respective base and engage in one another in such a way that, for the compression of the refrigerant, the second compressor body is movable on an orbital path about a center axis with respect to the first compressor body, thereby forming chambers, comprising an outlet in the base of the stationary compressor body, leading to a high-pressure chamber in the outer housing, and comprising a check valve disposed between the outlet and the high-pressure chamber, with a valve body which is freely movable in a movement space extending between a valve seat and a valve guard, between a closed position, determined by the valve seat, and an open position, determined by the valve guard.  
         [0004]     Such a compressor with a check valve is known from U.S. Pat. No. 5,451,148.  
         [0005]     In the case of such a check valve there is generally the requirement that it opens quickly, closes quickly and, when opening, provides as quickly as possible as large a cross-sectional area as possible for a flow to pass through.  
         [0006]     It is therefore an object of the invention to improve a compressor of the type, described at the beginning in such a way as to ensure that the function of the check valve is as optimal as possible.  
       SUMMARY OF THE INVENTION  
       [0007]     This object is achieved according to the invention in the case of a compressor of the type described at the beginning by the outlet having a center axis which is offset with respect to a center axis of the valve seat for the valve body in a transverse direction in relation to the center axis. This solution has the advantage that the offset arrangement of the outlet with respect to the valve seat makes the valve undergo an asymmetric force from the inflowing refrigerant when it opens, and consequently makes it open quickly.  
         [0008]     The quick opening of the valve body can be achieved particularly advantageously if a cross-sectional area of a through-opening of the valve seat is greater than a cross-sectional area of the outlet, so that a relatively great force can be produced on the valve body by the refrigerant impinging on the valve body.  
         [0009]     To be able to make the through-opening have a cross-sectional area which is greater than the cross-sectional area of the outlet, it is preferably provided that a pre-chamber having a greater cross-sectional area than the outlet is disposed between the valve seat and the outlet.  
         [0010]     This pre-chamber suitably has a cross-sectional area which either corresponds to the cross-sectional area of the through-opening, which for its part is intended to be greater than the cross-sectional area of the outlet, or is greater than the cross-sectional area of the through-opening of the valve seat.  
         [0011]     With regard to the arrangement of the pre-chamber in relation to the outlet, it is suitably provided that a center axis of the pre-chamber is disposed in such a way that it is offset transversely in relation to the center axis of the outlet.  
         [0012]     It is particularly advantageous if the center axis of the pre-chamber substantially coincides with the center axis of the valve seat, and consequently the two are disposed substantially coaxially in relation to each other.  
         [0013]     For receiving and guiding the valve body, the movement space between the valve seat and the valve guard is preferably provided.  
         [0014]     To be able to use a valve body with the smallest possible mass with the greatest possible through-opening through the valve seat, it is preferably provided that the movement space extends in the direction of its center axis from the valve seat to the valve guard with a cross-sectional area which corresponds approximately to the valve seat, that is to say in particular an outside diameter of the same.  
         [0015]     Furthermore, an advantageous force effect is obtained on the valve body when the check valve is opened and held open if the center axis of the movement space substantially coincides with the center axis of the valve seat.  
         [0016]     With regard to the valve body, so far nothing more specific has been stated. So the prior art discloses valve bodies with a central plate-shaped part from which further arms extend or which is enclosed by openings.  
         [0017]     An optimal structural design solution provides that the valve body is formed as a plate with an outer contour corresponding approximately to the valve seat. This solution has the advantage that no additional arms or other elements unnecessarily increasing the mass of the valve body are necessary to guide the valve body. Rather, such a valve body can be optimally held and guided in the movement space defined above, the cross-sectional area of which corresponds approximately to the cross-sectional area of the valve seat.  
         [0018]     In particular in the case of a plate-shaped valve body with an outer contour which corresponds approximately to the valve seat there is the problem that, in the open position of the valve body, the refrigerant entering the movement space via the through-opening of the valve seat must be removed from the movement space.  
         [0019]     It is preferably provided for this purpose that at least one outlet space is disposed laterally with respect to the movement space, in particular radially outside the same, which outlet space opens laterally into the movement space with a mouth opening between the valve guard and the valve seat, and leads to an outlet opening.  
         [0020]     Such an outlet space creates the possibility when the valve body has been lifted off the valve seat, in particular is in the open position, of allowing the refrigerant flow that is spreading out in the direction of the pressure arm to exit into the high-pressure chamber with as large a cross-section as possible and as unhindered as possible. A particularly large cross-section for the mouth opening of the outlet space into the movement space is available whenever the mouth opening of the outlet space extends as far as the valve seat, preferably therefore between the valve guard and the valve seat.  
         [0021]     The outlet opening of the outlet space could be disposed for example opposite the mouth opening. A structurally suitable design solution provides that the outlet opening is disposed in the region of the valve guard.  
         [0022]     The outlet opening is preferably disposed in such a way that it merges into a through-opening in the valve guard, and consequently the emerging refrigerant flow also passes through the valve guard via the outlet spaces and the outlet opening.  
         [0023]     To have optimal flow cross-sections available, it is preferably provided that a number of outlet spaces are disposed around the movement space.  
         [0024]     With regard to the delimitation of the movement space, so far nothing more specific has been stated. So one advantageous solution provides that the movement space is delimited by at least one wall surface lying next to the at least one mouth opening.  
         [0025]     Such a wall surface preferably serves as a guiding surface for the valve body, so that the latter is always held in the intended movement space.  
         [0026]     It is particularly advantageous in this case if the valve body is guided by a number of guiding surfaces disposed at equal angular intervals around the center axis of the movement space.  
         [0027]     In principle it would be possible to support the valve body on the valve guard by a number of points of contact. This has the disadvantage, however, that the valve body must be of a very stable configuration if no damage is to occur to the valve body when it comes against the valve guard, since, when the compressor starts up, the valve body moves at high speed in the direction of the valve guard and is then caught by it.  
         [0028]     For this purpose, the valve body is preferably provided with an end face, which can be made to lie flat against the contact surface of the valve body.  
         [0029]     With regard to the sizes of the contact surface and the end face, so far nothing more specific has been stated.  
         [0030]     So it is preferably provided that the contact surface extends over a surface area which is greater than half the surface area over which the end face extends.  
         [0031]     It is even better if the contact surface extends over a surface area which corresponds approximately to the surface area over which the end face extends.  
         [0032]     So far nothing more specific has been stated with regard to the formation of the end face either. So it is preferably provided that the valve body is formed as a plate and the end face extends over a surface area which corresponds to more than half the extent of the valve body transversely in relation to its center axis.  
         [0033]     The surface area over which the end face extends is preferably so large that it substantially corresponds to the cross-sectional area of the valve body.  
         [0034]     In order to prevent the valve body from remaining attached to the valve guard by adhesion when the pressure in the scroll compressor drops, and not going over quickly enough into the closed position, it is preferably provided that the valve guard is provided with an aperture which extends from a mouth opening lying in the contact surface to a high-pressure side of the valve guard. This achieves the effect that the check valve closes quickly when there is a drop in pressure in the scroll compressor, since, even in the case in which the valve body sticks to the valve guard, the valve body quickly detaches itself from the valve guard on account of the pressure to which it is exposed via the aperture.  
         [0035]     The valve body can detach itself particularly quickly from the valve guard if the aperture lies laterally with respect to the center axis of the movement space, and consequently the force acting first on the valve body via the aperture causes tilting of the valve body.  
         [0036]     In this case, the aperture is suitably disposed in an angular segment which lies on a side of the center axis of the movement space that is opposite from the center axis of the outlet, so that the aperture lies in one semicircle around the center axis of the movement space, while the center axis of the outlet lies in the other semicircle.  
         [0037]     The angular segment in which the aperture lies preferably lies symmetrically in relation to a plane running through the center axis of the outlet and the center axis of the movement space.  
         [0038]     The angular segment could comprise an entire semicircle.  
         [0039]     It is particularly advantageous, however, if the angular segment within which the at least one aperture lies amounts to approximately 150°, even better approximately 120°.  
         [0040]     With regard to the arrangement of the through-openings in the valve guard, so far nothing more specific has been stated. In order not to limit the cross-sectional area available for the refrigerant flow, it is preferably provided that the through-openings in the valve guard lie outside the part of the valve guard that closes off the movement space.  
         [0041]     Further features and advantages are the subject of the description which follows and the graphical representation of a number of exemplary embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0042]      FIG. 1  shows a longitudinal section through an exemplary embodiment of a compressor according to the invention;  
         [0043]      FIG. 2  shows a longitudinal section, turned by an angle of approximately 90°, through the exemplary embodiment of the compressor according to the invention;  
         [0044]      FIG. 3  shows a section along line  3 - 3  in  FIG. 1 ;  
         [0045]      FIG. 4  shows a section along line  4 - 4  in  FIG. 1 ;  
         [0046]      FIG. 5  shows a plan view of a bearing part forming a base of a motor housing;  
         [0047]      FIG. 6  shows a perspective representation of a section in the region of a check valve;  
         [0048]      FIG. 7  shows an enlarged sectional representation similar to  FIG. 1  in the region of the check valve;  
         [0049]      FIG. 8  shows a section along line  8 - 8  in  FIG. 7 ;  
         [0050]      FIG. 9  shows a section along line  9 - 9  in  FIG. 7 ;  
         [0051]      FIG. 10  shows a section corresponding to  FIG. 7  with the valve body in the open position;  
         [0052]      FIG. 11  shows a section along line  11 - 11  in  FIG. 7 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0053]     An exemplary embodiment of a compressor according to the invention, represented in FIGS.  1  to  5 , comprises an outer housing which is designated as a whole by  10  and in which there is disposed a scroll compressor which is designated as a whole by  12  and can be driven by a drive unit which is designated as a whole by  14 .  
         [0054]     The scroll compressor  12  comprises in this case a first compressor body  16  and a second compressor body  18 , the first compressor body  16  having a first scroll rib  22 , which rises above a base  20  of the same and is formed in the shape of an involute of a circle, and the second compressor body  18  having a second scroll rib  26 , which rises above a base  24  of the same and is formed in the shape of an involute of a circle, the scroll ribs  22 ,  26  engaging in one another and in each case lying in a sealing manner against the base surfaces  28  and  30 , respectively, of in each case the other compressor body  18 ,  16 , so that chambers  32  are formed between the scroll ribs  22 ,  26  and the base surfaces  28 ,  30  of the compressor bodies  16 ,  18 , in which chambers there takes place a compression of a refrigerant which flows in at an initial pressure via an intake region  34  surrounding the scroll ribs  22 ,  26  on the radially outer side and, after the compression in the chambers  28 , emerges via an outlet  36  provided in the base  20  of the first compressor body  16 , having been compressed to high pressure.  
         [0055]     In the first exemplary embodiment described, the first compressor body  16  is held fixed in the outer housing  10 , to be precise by means of a separating body  40 , which for its part is held on the outer housing  10  inside the same, reaches over the base  20  of the first compressor body  16  at a spacing from it and is connected in a sealed manner to an annular flange  42  of the first compressor body  16 , which runs around the outlet  36  and protrudes above the base  20  on a side that is opposite from the scroll rib  26 .  
         [0056]     Between the base  20  of the first compressor body  16  and the separating body  40  there is consequently formed a cooling chamber  44 , which is intended for cooling the base  20  of the first compressor body  16  and is for example the subject of WO 02/052205 A2, to the full content of which reference is made with respect to the cooling of the scroll compressor  12 .  
         [0057]     By contrast with the first compressor body  16 , the second compressor body  18  is movable on a orbital path about a center axis  46  in relation to the first compressor body  16 , the scroll ribs  22  and  26  theoretically lying against one another along a line of contact and the line of contact likewise running on the orbital path about the center axis  46  when there is movement of the second compressor body  18 .  
         [0058]     The drive of the second compressor body  18  on the orbital path about the center axis  46  takes place by the already mentioned drive unit  14 , which comprises an eccentric drive  50 , a drive shaft  52  driving the eccentric drive  50 , a drive motor  54  and a bearing unit  56  for bearingly mounting the drive shaft  52 .  
         [0059]     To be specific, the eccentric drive  50  is formed by a driver  62 , which is disposed eccentrically on the drive shaft  52 , and consequently eccentrically in relation to the center axis  46 , and engages in a driver receptacle  64 , which is fixedly connected to the base  24  of the second compressor body  18 , in order in this way to move the second compressor body  18  on the orbital path about the center axis  46 .  
         [0060]     The bearing unit  56  for its part comprises a first bearing body  66 , which represents a main bearing body and with a bearing portion  68  bearingly mounts the drive shaft  52  in a region  70 , and which carries the driver  62 , the driver  62  preferably being disposed in one piece on the region  70 .  
         [0061]     Furthermore, the first bearing body  66  encloses a space  72 , in which the eccentric drive  50  is disposed and in which a compensating mass  74  fixedly connected to the drive shaft  52  moves.  
         [0062]     Moreover, the first bearing body  66  extends laterally with respect to the space  72  in the direction of the base  24  of the second compressor body  18  and has carrying surfaces  78  which run around an opening  76  of the space  72  that is facing the second compressor body  18  and on which the second compressor body  18  rests with a rear side  80  opposite from the second scroll rib  26 , and is consequently supported in such a way that the second compressor body  18  is secured against movement away from the first compressor body  16 .  
         [0063]     The fixing of the first bearing body  66  in the outer housing  10  takes place in this case with mounting arms  82 , which extend radially from the first bearing body  66  as far as the outer housing  10  and precisely hold the first bearing body  66  in the latter.  
         [0064]     The first bearing body  66  also has on a side opposite from the mounting arms  82  an outer surface  84 , on which there is located a housing sleeve  88  of a motor housing  90 , which sleeve extends inside and at a spacing from a cylindrical portion  86  of the outer housing  10 , is preferably likewise cylindrical and extends as far as a second bearing body  92 , which forms a base of the motor housing  90 , is disposed at a distance from the first bearing body  66  and forms a bearing portion  94  in which the drive shaft  52  is mounted with an end region  96  coaxially in relation to the center axis  46 .  
         [0065]     For additional stabilization, the second bearing body  92  is also supported on the outer housing  10  by means of supporting bodies  98 .  
         [0066]     The entire motor housing  90  consequently runs inside the cylindrical portion  86  of the outer housing  10  and at a spacing from it.  
         [0067]     Disposed in the motor housing  90 , between the first bearing body  66  and the second bearing body  92 , is the drive motor  54 , which comprises a rotor  100 , mounted on the drive shaft  52 , and a stator  102 , surrounding the rotor  100 , the stator  102  being held by the housing sleeve  88  of the motor housing  90  so as to be fixed in a stable manner in relation to the outer housing  10 , so that there is a customary gap  104  between the rotor  100  and the stator  102 .  
         [0068]     In addition, the stator  102  is provided on its side facing the housing sleeve  88  with cooling channels  106 , which run parallel to the center axis  46 , for example in the form of outer grooves, in the stator  102  over the entire contact side  108  of the latter, the stator  102  being supported on the housing sleeve  88  via the contact side  108 .  
         [0069]     Provided between the second bearing body  92  and a base part  110  of the outer housing  10  is a free space  112 , which offers the possibility that, with the outer housing  10  rising up above the base part  110  with an approximately vertically running center axis  46 , there forms an oil sump  114 , in which on the one hand lubricating oil collects under the force of gravity and on the other hand lubricating oil is kept ready to lubricate the compressor according to the invention.  
         [0070]     An oil feed pipe  116 , extending from the end region  96  of the drive shaft  52  and coaxially in relation to the latter, dips into the oil sump  114  and has in its interior space  118  a feeding blade  120 , and consequently acts as an oil pump which pumps oil out of the oil sump  114  into a lubricating oil channel  122 , which passes through the drive shaft  52  and allows lubricating oil to leave via a mouth opening  124  on an end face  126  of the driver  62 , in order to lubricate the rotary bearing formed between the driver receptacle  64  and the driver  62  for the movement of the second compressor body  18  on the orbital path.  
         [0071]     Furthermore, a transverse channel  128  branches off from the lubricating oil channel  122 , leads to the rotary bearing formed between the bearing portion  68  of the first bearing body  66  and the region  70  of the drive shaft  52  and lubricates this bearing, and finally a venting channel  130  branches off from the lubricating oil channel  122 .  
         [0072]     The oil used for lubricating the driver  62  in the driver receptacle  64  leaves the driver receptacle  64  in the region of an opening  132  of the driver receptacle  64  that is facing the region  70 , then arrives at a base  134  of the space  70  that is formed by the first bearing body  66  and passes from there via outlet channels  136 , which form an oil guide with the base  134 , into an upper interior space  140  of the motor housing  90 . Furthermore, the oil, which serves for lubricating the region  70  of the drive shaft  52  in the bearing portion  68 , leaves the bearing portion  68  on an underside  142  of the latter, and consequently also enters the upper interior space  140  of the motor housing  90 .  
         [0073]     The supply of refrigerant to be compressed by the scroll compressor  12  to the compressor according to the invention takes place via an intake line  150 , which is brought to an intake connection  152 , which for its part is held on the outer housing  10 , but is brought through the latter to the motor housing  90 .  
         [0074]     The intake connection  152  preferably has a sleeve  154 , which passes through the outer housing  10  of the compressor according to the invention and engages in a receptacle  156  securely connected to the housing sleeve  88  of the motor housing  90 , as represented in  FIGS. 1 and 3 . The receptacle  156  encloses in this case an inlet  158  for the refrigerant that is provided in the housing sleeve  88 , so that said refrigerant can directly enter a lower interior space  160  of the motor housing  90  which lies between the stator  102  and the second bearing body  92 .  
         [0075]     Furthermore, the inlet opening  158  is disposed in the direction of the center axis  46  in such a way that the refrigerant enters the lower interior space  160  at the level of a winding head  162  of the stator  102 , which likewise projects into the interior space  160 .  
         [0076]     For optimum distribution of the refrigerant in the lower interior space  160 , associated with the inlet  158  is a deflecting unit  164 , which has two deflecting surfaces  166  and  168 , which deflect the refrigerant flowing in through the sleeve  154  approximately in a radial direction  170  in relation to the center axis  46 , in such a way that main directions of flow of the supplied gaseous refrigerant run around the winding head  162  in two opposite azimuthal directions  172  and  174  in relation to the center axis  46 , to be precise inside the housing sleeve  88 , the inner wall  176  of which thereby provides further guidance for the refrigerant spreading out in the azimuthal directions  172  and  174  and contributes to separation of oil that is entrained by the supplied refrigerant by it being deposited on the inner wall  176  and running down on the latter in the direction of the second bearing body  92 , which is represented on its own in  FIG. 5 . The bearing body  92  also forms a base  178 , which substantially closes the housing sleeve  88  but is provided with oil outlet openings  180 , from which the oil that is separated can flow into the oil sump  114 .  
         [0077]     As a result of the closed base  178 , the refrigerant entering the lower interior space  160  of the motor housing  90  substantially does not have the possibility of passing into the free space  112  between the second bearing body  92  and the base part  110 , but rather remains substantially in the interior space  160  for the purpose of cooling the winding head  162  and then, proceeding from the interior space  160 , passes through the cooling channels  106  and the gap  104  between the rotor  100  and the stator  102  into the upper interior space  140 , which lies between the first bearing body  66  and the stator  102 , in order to cool the winding heads  182  projecting into the upper interior space  140 .  
         [0078]     At least one outlet opening  184  is provided at the level of the winding head  82  in the housing sleeve  88 , as represented in  FIGS. 1 and 4 , through which opening the refrigerant leaves the upper interior space  140  of the motor housing  90 , to be precise into an intermediate space  188 , which exists between the cylindrical portion  88  and the first bearing body  66 —apart from the mounting arms  82 —and the motor housing  90 , and which is part of an oil separator  190 . In particular, the intermediate space  188  lies substantially between an inner wall surface  192  of the cylindrical portion  86  of the outer housing  10  and an outer wall surface  194  of the cylindrical housing sleeve  88 , the intermediate space  188  preferably extending as a closed annular space around the housing sleeve  88 .  
         [0079]     To generate a flow of the gaseous refrigerant in opposite azimuthal directions  196 ,  198  in the intermediate space  188 , disposed opposite the outlet opening  184  is a deflecting unit  200 , which has deflecting surfaces  202  and  204 , which deflect the gaseous refrigerant leaving the outlet opening  184  into the azimuthal directions  196  and  198 .  
         [0080]     It is, however, also conceivable to provide a number of outlet openings  184 , opening into the intermediate space  188 , and deflecting units  200  associated with them at angular intervals around the center axis  46 .  
         [0081]     As a result of the gaseous refrigerant being guided in the azimuthal directions  196  and  198 , in particular between the inner wall surface  192  and the outer wall surface  194 , an oil separating effect occurs on account of the constantly acting radial acceleration of oil droplets in the gaseous refrigerant, manifested in particular by oil which is entrained by the refrigerant being deposited on the inner wall surface  192  and the outer wall surface  194 , it being possible when the compressor is installed with a substantially vertical center axis  46  for the oil to run down between the outer housing  10  and the motor housing  90 , preferably along the inner wall surfaces  192  and the outer wall surface  194  in the direction of the oil sump  114 , since between the outer housing  10  and the motor housing  90  there is over the entire extent of the motor housing  90  in the direction of the center axis  46  a free intermediate space  206 , which proceeds from the intermediate space  188  to merge into the free space  112  and via which the oil can in the end be supplied to the oil sump  114 .  
         [0082]     The separation of all the oil entrained by the refrigerant on its way through the interior space  160 , through the gap  104  and the cooling channels  106  and also the interior space  140 , and in particular at least partially oil which leaves on the underside  142  of the bearing portion  68  and oil which has been supplied to the interior space  140  via the outlet channels  136 , takes place in the oil separator  190 .  
         [0083]     The refrigerant that is consequently substantially freed of oil in the oil separator  190  then flows to exit from the intermediate space  188  of the oil separator  190  between the mounting arms  82 , and consequently past the first bearing body  66 , on the outside of the same, in the direction of the intake region  34  of the scroll compressor  12 , and is taken in by the latter and compressed, the compressed refrigerant entering through the outlet  36  and a downstream check valve  208  into a high-pressure chamber  210 , which lies between a cover  212  of the outer housing  10  and the separating body  40 , and is discharged from this chamber through a pressure connection  214 .  
         [0084]     The check valve  208  has a pre-chamber  216 , disposed following the outlet  36 , and following this pre-chamber a valve seat  218 , on which a valve body  220  can be placed.  
         [0085]     As can be gathered in particular from  FIG. 8 , a center axis  222  of the outlet  36  is disposed laterally offset with respect to a center axis  224  of the pre-chamber  216 , so that overall the outlet  36  opens out asymmetrically into the pre-chamber  216 .  
         [0086]     For this purpose, the pre-chamber  216  is provided with a cross-sectional area which amounts to a multiple of the cross-sectional area of the outlet  36 , so that the outlet  36  opens with the full cross-sectional area into a base  226  of the pre-chamber  216 .  
         [0087]     The pre-chamber  216  then extends subsequently with its enlarged cross-sectional area in comparison with the outlet  36  as far as the valve seat  218  in the direction of the center axis  224 , so that, with the valve body  220  lifted off, in the region of the valve seat  218  a through-opening  228  with a cross-sectional area corresponding to the cross-sectional area of the pre-chamber  216  is available for the flow to pass through the valve seat  218 .  
         [0088]     The valve body  220  is formed as a plate-shaped body extending continuously, that is to say without openings, as far as an outer contour  238 , the outer contour  238  having a geometrically simple shape, for example a circle, although the shape may also be elliptical or rectangular, possibly formed with rounded corners.  
         [0089]     On a side opposite from the pre-chamber  216 , a movement space  230  for the valve body  220  rises up above the valve seat  218  and has a center axis  232  which coincides with the center axis  224 . The movement space  230  extends along the center axis  232  above the valve seat  218  as far as a valve guard which is designated as a whole by  240  and delimits the movement space  230  on a side opposite from the valve seat  218 .  
         [0090]     The cross-sectional area of the movement space  230  in this case corresponds approximately to the cross-sectional area in the region of the valve seat  218 , so that the valve body  220  can move freely in the movement space  230  between a closed position ( FIG. 7 ), in which the valve body  220  rests on the valve seat  218 , in an open position ( FIG. 10 ), in which the valve body  220  lies against the valve guard  240 .  
         [0091]     For guiding the valve body  220  which is movable in the movement space  230 , the movement space  230  has adjoining the valve seat  218  guiding surfaces  242 , which run parallel to the center axis  232 , in the simplest case are formed by wall surfaces delimiting the movement space  230  and, for example, are disposed at equal angular spacings from one another, in order to guide the valve body  220  in the direction of the center axis  232  of the movement space  230  on its circumferential side  238 , so that it is ensured in particular that the valve body  220  comes to lie on the valve seat  218  with the necessary precision during the transition from the open position into the closed position.  
         [0092]     To make it possible when the valve body  220  is in the open position, as represented in  FIG. 10 , for gaseous refrigerant that has entered the movement space  230  through the pre-chamber  216  and the valve seat  218  to flow out from the movement space  230 , provided laterally with respect to the movement space  230  are outlet spaces  244 , which open laterally via mouth openings  246  into the movement space  230 , the mouth openings  246  preferably extending in the direction of the center axis  232  from the valve guard  240  as far as the valve seat  218  and extending in the circumferential direction about the center axis  232  in each case as far as the guiding surfaces  242 .  
         [0093]     Furthermore, the outlet spaces  244  lead to outlet openings  248  facing the valve guard  240 , which for their part merge into through-openings  250  provided in the valve guard  240 , the through-openings  250  in the valve guard  240  having a cross-sectional area which is greater than the cross-sectional area of the outlet openings  248  of the outlet spaces  244 . Consequently, gaseous refrigerant entering the movement space  230  through the valve seat  218  in the open position of the valve body  220  has the possibility of leaving the movement space  230  via the mouth openings  246 , flowing through the outlet spaces  244  and entering into the high-pressure chamber  210  from the outlet spaces  244  via their outlet openings  248  and the through-opening  250  in the valve guard  240 .  
         [0094]     The flow cross-sections of the outlet spaces  244  and of the outlet openings  248  as well as of the through-openings  250  in the valve guard are in this case chosen such that the gaseous refrigerant flowing through the movement space  230  and the outlet chambers  244  can flow around the valve body  220  in the open position and thereby also contributes to moving the valve body  220  in the direction of the open position, in which the valve body  220  lies for example against the valve guard  240 , when the check valve  208  is opened.  
         [0095]     The valve body  220  has for its part, facing the valve guard  240 , an upper end face  252 , which preferably extends over the entire extent of the valve body  220  transversely in relation to the center axis  232  as far as the outer contour  238  and, in the case of the open position of the valve body  220 —as represented in  FIG. 10 —lies against a contact surface  254  of the valve guard  240 , the contact surface  254  extending over a surface area which substantially corresponds to the surface area over which the end face  252  extends, so that the end face  252  can be made to lie fully flat against the contact surface  254  of the valve guard  244 , in particular to avoid damage to the valve body  220  when there is a quick transition from the closed position into the open position.  
         [0096]     To be able to move the valve body  220  quickly from the open position into the closed position, and in particular to be able quickly to eliminate any kind of adhesion of the valve body  220  to the valve guard  240  by engagement of the end face  252  against the contact surface  254 , the valve guard  240  is provided with an aperture  260 , which extends from a mouth opening  262  lying in the contact surface  254  of the valve guard  240  as far as an upper side  264  of the valve guard  240  that is facing the high-pressure chamber  210 , in order to use the pressure that is present in the high-pressure chamber  210  when there is a drop in the pressure in the movement space  230  for making a force act on the partial region of the end face  252  that is facing the aperture  260  and then, when the valve body  220  detaches itself with the end face  252  from the contact surface  254 , finally use the pressure in the high-pressure chamber  210  for making a force act on the entire end face  252  in order to move the valve body  220  into the movement space  230  so far from the open position in the direction of the closed position that the gaseous refrigerant flow  262  flowing back in the direction of the outlet  36  via the outlet spaces  244  additionally takes the valve body  220  with it and moves it in an accelerated manner in the direction of the closed position, represented in  FIGS. 6 and 7 , in order to achieve quick closing of the check valve  208 .  
         [0097]     The aperture  260  is in this case preferably not disposed symmetrically in relation to the center axis  232 , but offset laterally with respect to it, to be precise on a side of the center axis  232  that is opposite from the center axis  222  of the outlet  36 , and also within an angular range W about the center axis  232  which extends symmetrically in relation to a plane E which runs through the center axis  232  of the movement space  230  and the center axis  222  of the outlet  36 .  
         [0098]     As a result of this arrangement of the aperture  260 , when the end face  252  detaches itself from the contact surface  254 , the valve body  220  is subjected to a force which is unsymmetrical in relation to the center axis  232 , which leads to the effect that the valve body  220  lifts off more quickly from the contact surface  254  with the partial region of the end face  252  lying close to the aperture  260  than with the partial regions lying over the outlet  36 , and consequently the valve body  220  performs a slight tilting movement, which is conducive overall to the detachment of the end face  252  from the contact surface  254  and also moves the valve body  220  more quickly into the refrigerant flow  262 , which runs through the outlet spaces  244  and the movement space  230  in the direction of the pre-chamber  216 , so that this refrigerant flow  262  moves the valve body  220  in an accelerated manner in the direction of the valve seat  218 , and consequently into the closed position.  
         [0099]     In addition, the moving of the valve body  220  from the open position into the closed position can also be accelerated by the outlet  36  opening asymmetrically into the base  226  of the pre-chamber  216 , and consequently forming overall, both in the pre-chamber  216  and in the movement space  230 , a refrigerant flow  266  from the high-pressure chamber  210  in the direction of the outlet  36  that is asymmetrical in relation to the center axis  232 , which additionally contributes to moving the valve body  220  in an accelerated manner into the closed position after leaving the open position.  
         [0100]     According to the invention, the check valve  208  is realized by the outlet  36 , and substantially the pre-chamber  216 , still being located within the base  20  of the compressor body  16 , while the valve seat  216 , the movement space  230  and the outlet spaces  244  are machined into the annular flange  42  formed in one piece on the base  20 , and finally the valve guard  240  rests on the annular flange  42  in the form of a cover.  
         [0101]     In the case of the solution according to the invention, the valve guard  240  not only has the described function but also extends radially in relation to the center axis  232  so far in the direction of the separating body  40  engaging on the annular flange  42  that the valve guard  240  reaches over a seal  270  that is effective between the annular flange  42  and the separating body  40 , lies in a groove  272  enclosing the annular flange  42  and brings about a pressure-resistant connection between the annular flange  42  and the separating body  40 .