Abstract:
Improvement for a refrigerant compressor comprising a compressor housing having at least two cylinder bores, pistons in the cylinder bores, a drive shaft chamber and a piston drive shaft in the drive shaft chamber such that this can operate with amounts of lubricant which are as small as possible, it is suggested that in the installed position of the refrigerant compressor the drive shaft chamber form a collection chamber for lubricant with an area which extends over only part of the extension of the drive shaft chamber and is located at the lowest point in the direction of gravity, that the drive shaft chamber have wall surfaces which adjoin the collection chamber and guide the lubricant accumulating in the drive shaft chamber to the collection chamber, and that a lubricant conveying device take up the lubricant from the collection chamber and convey it to lubrication points.

Description:
[0001]     This patent application is a continuation of International application No. PCT/EP2004/012839 filed on Nov. 12, 2004.  
         [0002]     This patent application claims the benefit of International application No. PCT/EP2004/012839 of Nov. 12, 2004 and German applications No. 103 54 529.8 of Nov. 17, 2003 and No. 103 58 471.4 of Dec. 10, 2003, the teachings and disclosure of which are hereby incorporated in their entirety by reference thereto.  
       BACKGROUND OF THE INVENTION  
       [0003]     The invention relates to a refrigerant compressor for motor vehicles comprising a compressor housing, at least two cylinder bores which are arranged in the compressor housing, pistons arranged in the cylinder bores, a drive shaft chamber arranged in the compressor housing as well as a piston drive shaft arranged in the drive shaft chamber.  
         [0004]     Refrigerant compressors of this type are known from the state of the art.  
         [0005]     The problem with them is that they require very large amounts of lubricant in order to ensure reliable lubrication at all the lubrication points.  
         [0006]     Large amounts of lubricant have, however, the disadvantage that refrigerant is dissolved in the large amounts of lubricant and this is outgassed again when the compressor is started and, therefore, leads to lubrication problems on account of the frothing of the lubricant.  
         [0007]     Furthermore, the refrigerant dissolving in the lubricant leads to a deterioration in the lubricating properties of the lubricant.  
         [0008]     The object underlying the invention is, therefore, to improve a refrigerant compressor of the type described at the outset in such a manner that this can operate with amounts of lubricant which are as small as possible.  
       SUMMARY OF THE INVENTION  
       [0009]     This object is accomplished in accordance with the invention, in a refrigerant compressor of the type described at the outset, in that in the installed position of the refrigerant compressor the drive shaft chamber forms a collection chamber for lubricant with an area which extends over only part of the extension of the drive shaft chamber and is located at the lowest point in the direction of gravity, that the drive shaft chamber has wall surfaces which adjoin the collection chamber and supply the lubricant accumulating in the drive shaft chamber to the collection chamber and that a lubricant conveying device takes up the lubricant from the collection chamber and conveys it to lubrication points.  
         [0010]     With the collection chamber according to the invention, which extends over only part of the extension of the drive shaft chamber, it is possible to reduce the amount of lubricant required for functioning of the lubricant conveying device and, therefore, to likewise diminish the problems inherent in the known, large amounts of lubricant.  
         [0011]     A particularly favorable solution provides for the wall surfaces to essentially guide all the lubricant accumulating in the drive shaft chamber to the collection chamber so that it is ensured, as a result, that lubricant, which cannot be taken up by the lubricant conveying device in recesses provided next to the collection chamber but would lead to an increase in the amount of lubricant required, does not collect in these recesses.  
         [0012]     A particularly expedient solution provides for some of the wall surfaces to extend at an angle to a drive shaft axis of the piston drive shaft in order to reduce the extension of the collection chamber in the direction of the drive shaft axis as a result.  
         [0013]     A solution which can be accomplished particularly favorably from a constructional point of view provides for the collection chamber to border on a housing cover of the compressor housing.  
         [0014]     In order to be able to assemble the compressor housing in a simple manner, the housing cover is preferably arranged such that it extends transversely to the drive shaft axis of the piston drive shaft.  
         [0015]     In order to also be able to collect all the lubricant accumulating in the compressor housing via the drive shaft chamber, it is provided for the drive shaft chamber to be located beneath a cylinder chamber of the compressor housing in the direction of gravity in the installed position of the compressor.  
         [0016]     The cylinder chamber is also preferably designed in such a manner that lubricant accumulating in it essentially enters the drive shaft chamber and, therefore, essentially no additional collection chambers whatsoever, which retain the lubricant and, therefore, contribute altogether to an increase in the amount of lubricant without improving the lubrication of the refrigerant compressor according to the invention, are formed in the cylinder chamber.  
         [0017]     In principle, it would be conceivable with the solution according to the invention to form the wall surfaces and the collection chamber by way of an insert provided in the compressor.  
         [0018]     A particularly favorable solution from a constructional point of view provides, however, for the collection chamber to be integrally formed in a drive shaft section of the compressor housing.  
         [0019]     Furthermore, it is likewise favorable when the wall surfaces guiding the lubricant to the collection chamber are integrally formed in the drive shaft section.  
         [0020]     A particularly expedient solution from a constructional point of view provides for the drive shaft section of the compressor housing to form a pan inclined towards the collection chamber.  
         [0021]     In order to be able to insert the refrigerant compressor according to the invention into motor vehicles without any problem, it has proven to be particularly expedient when the collection chamber always remains the subsection of the drive shaft section located at the lowest point with an inclination of a drive shaft axis of up to at the most plus/minus 35°, in particular, up to at the most plus/minus 15° in relation to the installed position.  
         [0022]     In addition, it is also favorable when the collection chamber always collects the lubricant with an inclination of the compressor housing about the drive shaft axis of the piston drive shaft of up to at the most plus/minus 90°, in particular, at the most plus/minus 45° in relation to the installed position.  
         [0023]     With respect to the design of the lubricant conveying device, no further details have so far been given. In principle, it would be conceivable to use any conventional lubricant conveying device.  
         [0024]     A solution which is particularly favorable on account of its constructional simplicity provides for the lubricant conveying device to comprise a lubricant pitching disk engaging in the collection chamber.  
         [0025]     Such a lubricant pitching disk could be driven by means of a suitable drive. A particularly expedient solution provides for the lubricant pitching disk to be arranged by the piston drive shaft.  
         [0026]     It is particularly simple from a constructional point of view when the piston drive shaft bears the lubricant pitching disk.  
         [0027]     With respect to the arrangement of the lubricant pitching disk, no further details have so far been given. For reasons of an advantageous overall concept, it has proven to be expedient when the lubricant pitching disk is arranged close to the compressor housing cover located nearest to the collection chamber.  
         [0028]     The lubricant pitching disk is preferably located such that it extends essentially vertically in the installed position.  
         [0029]     In the case where a lubricant pitching disk is provided, the lubricant conveying device is designed in such a manner that it preferably has, in the compressor housing, a receiving chamber for lubricant pitched by the lubricant pitching disk.  
         [0030]     In order to fill the receiving chamber with lubricant, the receiving chamber is preferably arranged such that lubricant pitched against a collecting surface and running down it enters this chamber.  
         [0031]     In principle, it would be conceivable to arrange the collecting surface and the receiving chamber at any suitable location of the compressor housing.  
         [0032]     One particularly advantageous solution provides for the receiving chamber to be arranged in the housing cover.  
         [0033]     Furthermore, an additional, advantageous solution provides for the collecting surface to be arranged on the housing cover.  
         [0034]     In order to improve the introduction of the lubricant collected by the collecting surfaces into the receiving chamber, it is preferably provided, in addition, for the lubricant conveying device to have guide ribs which guide the lubricant into the receiving chamber.  
         [0035]     The supply of lubricant to at least some of the lubrication points could be brought about, for example, by way of channels provided in the compressor housing.  
         [0036]     One particularly favorable solution provides, however, for the lubricant conveying device to comprise a central lubricant channel integrated into the piston drive shaft. The individual lubrication points of the piston drive shaft may be supplied with lubricant in a particularly simple manner due to such a central lubricant channel of the piston drive shaft.  
         [0037]     The supply of lubricant to the central lubricant channel may be realized, in particular, from a constructional point of view when lubricant can be supplied to the central lubricant channel from the receiving chamber.  
         [0038]     In this respect, it is particularly favorable when the receiving chamber borders directly on the piston drive shaft at its end side and, therefore, the lubricant channel opens directly into the receiving chamber.  
         [0039]     In order to supply the individual lubrication points of the piston drive shaft, it has proven to be expedient when the central lubricant channel is provided with lubricant supply channels for lubrication points of the piston drive shaft which extend transversely to the lubricant channel.  
         [0040]     These lubricant supply channels extending transversely to the central lubricant channel improve the conveyance of lubricant since a centrifugal force acts on the lubricant located in the lubricant supply channels as a result of the rotation of the piston drive shaft and this force conveys the lubricant to the respective lubrication points radially to the central lubricant channel and so a pumping action results thereby.  
         [0041]     With respect to the filling amount of lubricant present altogether in the refrigerant compressor according to the invention, no further details have so far been given. The filling amount may be advantageously reduced in the case of the solution according to the invention in such a manner that this is less than double the capacity of the refrigerant compressor.  
         [0042]     It is even more advantageous when the filling amount of the lubricant is less than 1.5 times the capacity of the refrigerant compressor.  
         [0043]     Alternatively or in addition to the embodiments described thus far, the object cited at the outset is also accomplished in accordance with the invention by a refrigerant compressor of the type described at the outset in that the piston drive shaft is mounted in the compressor housing only in slide bearings and that the slide bearings have slide coatings with lubrication deficiency properties.  
         [0044]     As a result of such slide coatings with lubrication deficiency properties it is possible to reduce the filling amount of lubricant to such an extent that even interruptions in the supply of lubricant can occur from time to time without damage resulting in the area of the slide bearings.  
         [0045]     In addition, the slide bearings have the advantage that they have an improved stability with respect to vibrations, in particular, idle time vibrations.  
         [0046]     In order to form additional lubrication points with lubrication deficiency properties with the solution according to the invention, it is also preferably provided for drive elements for the pistons to be mounted on the piston drive shaft with slide bearings which have slide coatings with lubrication deficiency properties.  
         [0047]     Slide coatings of this type with lubrication deficiency properties may be provided, for example, on the piston drive shaft, for example, eccentric members thereof.  
         [0048]     It is, however, particularly favorable when the slide coatings with lubrication deficiency properties are provided on the drive elements.  
         [0049]     These drive elements are, for example, connecting rods, slide coatings of this type being provided in the connecting rod eye of these connecting rods which engages on the piston drive shaft.  
         [0050]     In addition, it is preferably provided for the drive elements to be mounted on the pistons with slide bearings which have slide coatings with lubrication deficiency properties.  
         [0051]     In this case, as well, a piston pin with a slide coating having such lubrication deficiency properties could be provided, for example, when connecting rods are used as drive elements.  
         [0052]     A solution which is expedient with respect to the production does, however, provide for a connecting rod eye which engages on the piston pin and has a slide coating with lubrication deficiency properties to be provided.  
         [0053]     The guidance of the pistons also requires customary lubrication.  
         [0054]     In the solution according to the invention it is, however, likewise provided for the pistons to be guided on the cylinder working surfaces in a manner with lubrication deficiency properties.  
         [0055]     Such a guidance of the pistons with lubrication deficiency properties could, for example, be realized in that the cylinder working surfaces are provided with a slide coating with lubrication deficiency properties.  
         [0056]     A constructionally expedient solution provides for the pistons to have piston rings with lubrication deficiency properties which can then run directly on the cylinder working surfaces.  
         [0057]     In addition or alternatively thereto, it is conceivable for the pistons to be provided with slide coatings with lubrication deficiency properties, in particular, on the piston skirt.  
         [0058]     When such slide coatings with lubrication deficiency properties are provided for the guidance of the pistons, the refrigerant compressor according to the invention may, again, be designed advantageously in that with it the pistons are guided on the compressor housing without any cylinder liners, i.e., essentially directly in cylinder bores of the compressor housing.  
         [0059]     The slide coatings with lubrication deficiency properties have not, themselves, been specified in greater detail in conjunction with the preceding explanations concerning the individual embodiments.  
         [0060]     Slide coatings with lubrication deficiency properties are to be understood such that with them the lubrication with a lubricant can be interrupted for a defined period of time without damage occurring in the area of the respective slide bearings. In the extreme case, the slide coatings with lubrication deficiency properties are designed in such a manner that they are capable of running dry, i.e., are suitable for mounting without lubricant over a longer period of time.  
         [0061]     One particularly advantageous embodiment of such slide coatings with lubrication deficiency properties provides for these to comprise PTFE, i.e., polytetrafluoroethylene.  
         [0062]     In addition, these slide coatings with lubrication deficiency properties may be improved in that additives improving the stability of the PTFE, such as, for example, CaF, can be incorporated into it.  
         [0063]     An additional, advantageous solution provides for the slide coatings with lubrication deficiency properties to comprise a porous layer consisting of sintered bronze which likewise has good lubrication deficiency properties.  
         [0064]     A particularly favorable solution provides for PTFE to be incorporated into the porous layer consisting of sintered bronze.  
         [0065]     With respect to the drive for the piston drive shaft, no further details have been given in conjunction with the preceding embodiments. It is, for example, particularly favorable for the design of the mounting for the piston drive shaft when this can be driven free from transverse forces on the drive side, i.e., forces directed transversely to the drive shaft axis since, as a result, the design of the mounting for the piston drive shaft need not take such transverse forces into consideration.  
         [0066]     In this respect, it is particularly favorable when the piston drive shaft can be driven via a coupling, wherein the coupling is preferably designed as an electromagnetic coupling.  
         [0067]     With respect to the drive for the coupling, it is provided for this to be drivable via a drive element.  
         [0068]     In order to avoid the introduction of transverse forces into the piston drive shaft via such a coupling, it is preferably provided for the drive element of the coupling to be mounted, for its part, on the compressor housing via roller bearings. As a result, all the transverse forces acting on the drive element act on the compressor housing via the roller bearing but to a substantially reduced extent, if at all, on the piston drive shaft.  
         [0069]     The drive element may be any type of drive element for a coupling. For example, this may be a drive wheel for the coupling as well as, for example, a drive pinion.  
         [0070]     An alternative form of a drive element, in particular, for use in motor vehicles, provides for the drive element to be a belt pulley, with which transverse forces occur to a considerable degree on account of the belt tension.  
         [0071]     Additional features and advantages of the invention are the subject matter of the following description as well as the drawings illustrating one embodiment. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0072]      FIG. 1  shows a longitudinal section through one embodiment of a refrigerant compressor according to the invention;  
         [0073]      FIG. 2  shows a section along line  2 - 2  in  FIG. 1 ;  
         [0074]      FIG. 3  shows a section along line  3 - 3  in  FIG. 1 ;  
         [0075]      FIG. 4  shows a section through a slide coating used in bearing points of the refrigerant compressor according to the invention;  
         [0076]      FIG. 5  shows a section along line  5 - 5  in  FIG. 1 ;  
         [0077]      FIG. 6  shows a perspective illustration of a housing cover illustrated in  FIG. 5 ;  
         [0078]      FIG. 7  shows a section along line  7 - 7  in  FIG. 5 ;  
         [0079]      FIG. 8  shows an enlarged, sectional illustration in the area around a piston drive shaft along line  8 - 8  in  FIG. 3 ;  
         [0080]      FIG. 9  shows a section along line  9 - 9  in  FIG. 2  and  
         [0081]      FIG. 10  shows a section along line  10 - 10  in  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0082]     One embodiment of a refrigerant compressor for motor vehicles according to the invention, illustrated in  FIG. 1 , comprises a compressor housing which is designated as a whole as  10  and comprises a housing member  12  which is closed on one side with a first housing cover  14  and on a side located opposite by a second housing cover  16 .  
         [0083]     The compressor housing  10  can be divided altogether into a cylinder section  20  which comprises, for example, two cylinder banks  22  and  24  ( FIG. 2 ) and a drive shaft section  26 , which is located beneath the cylinder section  20  in a vertical direction in the installed position and in which a piston drive shaft designated as a whole as  30  is mounted for rotation about a drive shaft axis  32 .  
         [0084]     In this respect, the piston drive shaft  30  is mounted in the area of a first bearing point  34  which is arranged in the housing member  12  on a side facing the housing cover  14  and a second bearing point  36  which is arranged on the second housing cover  16 .  
         [0085]     The bearing point  34  is formed by a first annular member  40 , which is preferably integrally formed in one piece on the housing member  12  and into which a first slide bearing bushing  42  with a slide coating  44  with lubrication deficiency properties is inserted, wherein the piston drive shaft  30  is slidingly mounted in the slide bearing bushing  42  with an outer surface designed as a first slide surface  45 . The first slide surface  45  is provided in a first bearing section  46  of the piston drive shaft  30 .  
         [0086]     The second bearing point  36  is formed by a second annular member  50  which is integrally formed in one piece on the second housing cover  16 . A second slide bearing bushing  52  with a slide coating with lubrication deficiency properties is seated in the second annular member  50 , the piston drive shaft  30  being mounted in this second slide bearing bushing with an outer surface of a second bearing section  56  of the piston drive shaft  30 , this outer surface being designed as a second slide surface  55 .  
         [0087]     The piston drive shaft  30  is, for its part, provided, for example, with a first eccentric member  60  and a second eccentric member  62 , wherein a first connecting rod  64  and a second connecting rod  66  are mounted on the first eccentric member  60  while a third connecting rod  68  and a fourth connecting rod  70  are mounted on the second member so as to be rotatable.  
         [0088]     As illustrated in  FIG. 2 , the third connecting rod  68  drives, for example, a piston  80  of the cylinder bank  24  while the fourth connecting rod  70  drives a piston  80  of the cylinder bank  22 .  
         [0089]     In the same way, the first connecting rod  64  drives a piston of the cylinder bank  24  and the second connecting rod  66  a piston of the cylinder bank  22 .  
         [0090]     Each of the connecting rods  64 ,  66 ,  68 ,  70  is mounted with its large connecting rod eye  82  on the respective eccentric member  60 ,  62  in the form of a slide bearing while a small connecting rod eye  84  of the respective connecting rod is mounted on the respective piston  80  via a piston pin  86  so as to be rotatable.  
         [0091]     In this respect, the mounting of the small connecting rod eye  84  on the piston pin  86  is also designed as a slide bearing.  
         [0092]     The large connecting rod eye  82  and the small connecting rod eye  84  are each preferably provided with a slide coating  88  with lubrication deficiency properties.  
         [0093]     Each of the pistons  80  is, for its part, as illustrated in  FIG. 2 , guided for displacement in a cylinder working surface  100  of a cylinder bore  98 , namely preferably at least via one piston ring  102  which is arranged in the piston skirt  104  close to a piston crown  106 . Furthermore, the respective piston  80  is preferably guided, in addition, by an outer surface  108  of the piston skirt  104  which is arranged on a side of the piston ring  102  located opposite the piston crown  106 .  
         [0094]     The piston ring  102  is preferably designed such that its outer side  110  sliding on the cylinder working surface  100  is formed by a material comprising PTFE, wherein the cylinder working surface  100  is, for example, designed as a machined and, in particular, hardened aluminum outer surface of the housing member  12  produced from a cast aluminum.  
         [0095]     In addition, the outer surface  108  of the piston skirt  104  is also provided, for example, with a slide coating  112  comprising PTFE.  
         [0096]     As a result of the design of the piston ring  102  as described with an outer side  110  comprising PTFE and the slide coating  112  with a material comprising PTFE, the piston  80  is also guided altogether in the cylinder bore  98  in a manner with lubrication deficiency properties.  
         [0097]     The cylinder bore  98  is, for its part, closed by a valve plate  116 , on which the valves, which are not illustrated in the drawings, are seated and are, for their part, covered by a cylinder head cover  118 .  
         [0098]     The drive for the piston drive shaft  30  results via a drive section  120  of the piston drive shaft  30  which extends on a side of the first bearing point  34  located opposite the second bearing point  36  and beyond it and which, for its part, passes through a slide ring seal  122  which is arranged in a shoulder  126  of the first housing cover  14  forming a slide ring seal chamber  124 .  
         [0099]     A coupling disk  130  of an electromagnetic coupling designated as a whole as  132  is arranged on an end section  128  of the piston drive shaft  30  projecting out of the compressor housing  10  beyond the slide ring seal  122 , wherein the coupling disk  130  is held on a coupling collar  138  seated on the end section  128  via a flexible ring  136 .  
         [0100]     Furthermore, the electromagnetic coupling  132  comprises a drivable belt disk  140  which is mounted, for its part, via roller bearings  142  on the shoulder  126  of the first housing cover  14  so as to be rotatable.  
         [0101]     The belt disk  140  comprises, in addition, an annular section  144 , on which the coupling disk  130  can be abutted in a friction-locking manner, namely by means of an electromagnet  146  which is arranged on a side of the annular section  144  of the belt disk  140  located opposite the coupling disk  130  and is held stationarily on the shoulder  126 .  
         [0102]     As a result of current being supplied to the electromagnet  146 , the coupling disk  130  is drawn against the annular section  144  of the belt disk  140  and abutted on it in a friction-locking manner and, as a result, is taken along by the driven belt disk  140 , wherein all the forces acting on the belt disk  140  on one side by means of the belt drive and directed transversely to the drive shaft axis  32  are absorbed by the roller bearing  142  for the belt disk  140 .  
         [0103]     The drive section  120  of the piston drive shaft  30  is driven by the coupling disk  130  via the flexible ring  136  and the coupling collar  138  free from external transverse forces caused, in particular, by the belt drive and so no such transverse forces need be absorbed, in particular, in the area of the first bearing point  34 .  
         [0104]     The only transverse forces to be absorbed by the piston drive shaft  30  and, therefore, the bearing points  34  and  36  result from the drive of the pistons  80  via the connecting rods  64 ,  66 ,  68 ,  70 .  
         [0105]     As illustrated in  FIG. 4  on an enlarged scale, the slide coatings  44 ,  54  are built up such that they have a carrier member  150  consisting of steel, on which a porous layer  152  consisting of sintered bronze is arranged, wherein a material  156 , comprising PTFE (polytetrafluoroethylene) and additional materials, is introduced, for example, rolled into pores or spaces  154  of the layer  152  consisting of sintered bronze so as to fill them and so the porous layer  152  consisting of sintered bronze is present on a slide surface  158  of such slide coatings  44 ,  54  together with the material  156  comprising PTFE and together they result in lubrication deficiency or at least temporarily dry running properties on the slide surface  158  so that the respective slide surfaces  45 ,  55  abutting thereon can also be guided and supported by the slide surface  158  or on the slide surface  158  without lubricant for an appreciable period of time essentially free from wear and tear.  
         [0106]     Such a construction of a slide surface  158  with lubrication deficiency properties or dry running properties is preferably provided not only in conjunction with the slide bearing coatings  44  and  54  but also in the area of the large connecting rod eye  82  and the small connecting rod eye  84  of the respective connecting rods  64 ,  66 ,  68 ,  70  as a slide coating  88  as well as preferably in the case of the slide coating  112  on the piston skirt  104  and in the case of the construction of the piston ring  102 , as well.  
         [0107]     Despite the slide coatings  44 ,  54 ,  88 ,  112  with deficient lubricant properties and the piston rings  102  in the compressor according to the invention, this also operates with lubricant which is supplied to the individual slide bearings in the compressor housing  10  at least in part by means of a lubricant conveying device  160 .  
         [0108]     The lubricant conveying device  160  comprises a lubricant pitching disk  162  which is rotatable with the piston drive shaft  30  coaxially to the drive shaft axis  32 . For this purpose, the lubricant pitching disk  162  is held on an imbalance compensation member  164  of the piston drive shaft  30  and is seated close to the second housing cover  16 , wherein the lubricant pitching disk  162  engages around the annular member  50  of the second bearing point  36  integrally formed on the second housing cover  16  on its outer side ( FIG. 1 ).  
         [0109]     The lubricant pitching disk  162  thereby dips into a lubricant sump  166  which is formed in the interior of the compressor housing  10  and pitches the lubricant out of the lubricant sump  166  against an inner side  168  of the second housing cover  16 , wherein the inner side  168  has ribs  170  ( FIGS. 5, 6 ,  7 ) which extend radially to the drive shaft and between which collecting surfaces  172  are arranged which are located so as to be set back in relation to the ribs  170  and form together with the ribs  170  collecting pockets  174  which are recessed into the second housing cover  16 , wherein the collecting pockets  174  are located merely between the ribs  170  which extend in a vertical direction above the piston drive shaft  30  in the installed position of the refrigerant compressor. The lubricant pitched into the collecting pockets  174  by the lubricant pitching disk  162  sticks at least partially to the collecting surfaces  172  and runs down the collecting surfaces  172  and, where applicable, guided by the ribs  170  in the direction of the piston drive shaft  30  as a result of gravity.  
         [0110]     The collecting surfaces  172  extend as far as into a receiving chamber  176  for the lubricant which, as is apparent from  FIGS. 1 and 7 , is arranged in the second housing cover  16  facing an end side  178  of the piston drive shaft and being open towards it.  
         [0111]     Proceeding from the end side  178  of the piston drive shaft  30 , a central lubricant channel  180  extending coaxially to the drive shaft axis  32  extends into it, namely preferably from the end side  178  as far as into the drive section  120 , wherein lubricant supply channels extending radially to the drive shaft axis  32  branch off the lubricant channel  180 .  
         [0112]     These are, for example, lubricant supply channels  182  and  184  which are provided in the first bearing section  46  and the second bearing section  56  and which have openings  186 ,  188  located in the slide surfaces  45  and  55 , respectively, via which lubrication of the sliding mounting of the slide surfaces  45  and  55 , respectively, on the slide coatings  44 ,  54  of the slide bearing bushings  42  and  52 , respectively, is brought about.  
         [0113]     In addition, lubricant supply channels  190 ,  192 ,  194  and  196  preferably branch off the central lubricant channel  180 , as well, and these supply channels contribute to the lubrication of the large connecting rod eyes  82  of the individual connecting rods  64 ,  66 ,  68 ,  70 , which are slidingly mounted on slide surfaces  200 ,  202 ,  204 ,  206  with their slide coatings  88 , with respective openings  210 ,  212 ,  214 ,  216  which are located in the slide surfaces  200 ,  202 ,  204 ,  206  for the connecting rods  64 ,  66 ,  68 ,  70  ( FIG. 1 ).  
         [0114]     Lubrication in the area of the slide coatings  88  of the small connecting rod eyes  84  and the slide coatings  112  as well as the piston rings  102  of the pistons  80  is brought about by a lubricant mist generated by the lubricant pitching disk  162  in the compressor housing  10 .  
         [0115]     Finally, a lubricant supply channel  220 , which serves to supply the slide ring seal  122  with lubricant, also branches off the central lubricant channel  180 .  
         [0116]     As illustrated, in addition, in  FIG. 1 , the slide ring seal chamber  124  in the shoulder  126  is designed such that the lubricant exiting from the slide ring seal  122  is collected and accumulates in it, wherein the entire slide ring seal  122  is preferably arranged so as to dip into the lubricant accumulating in the slide ring seal chamber  124  and it is possible for the lubricant to leave the slide ring seal chamber  124  only via an overflow channel  222  arranged above the first annular member  40 .  
         [0117]     The lubricant passing through the slide ring seal  122  is, as illustrated in  FIG. 8 , collected in a space  125  between the slide ring seal  122  and an outer shaft seal  123  and supplied to a cavity  219  via a channel  218 .  
         [0118]     All the lubricant which accumulates within a cylinder chamber  224  enclosed by the cylinder section  20  of the compressor housing  10  and within a drive shaft chamber  226  enclosed by the drive shaft section  26 , wherein the cylinder chamber  224  and the drive shaft chamber  226  merge into one another, is collected as a result of gravity in a pan  228  which is formed by the drive shaft section  26  and which, as illustrated in  FIG. 1 , extends in the direction of the drive shaft axis  32  from the side of the first bearing point  34  in the direction towards the second housing cover  16  and forms a collection chamber  230 , in which the lubricant collects to form the lubricant sump  166 , directly adjoining the second housing cover  16 . In this respect, the pan  228  is preferably inclined with its wall surfaces  232  and the base surface  234  in the direction of the collection chamber  230  in order to guide all the lubricant entering the pan  228  to the collection chamber  230  as a result of gravity.  
         [0119]     The lubricant flowing out of the slide ring seal chamber  124  out of the overflow channel  222  also runs around the first annular member  40  into the pan  228  and is supplied to the collection chamber  230 . In addition, the lubricant collecting in the cavity  219  is also supplied to the drive shaft chamber  226  via a channel  236 .  
         [0120]     The collection chamber  230  is preferably designed such that the lubricant collecting in it to form the lubricant sump  166  can still be taken up by the lubricant pitching disk  162  and pitched into the collecting pockets  174  even with an inclination of the drive shaft axis in relation to the ideal installation position through up to plus/minus 35°, preferably up to plus/minus 15° in a vertical direction or also rotation of the compressor housing about the drive shaft axis  22  through up to plus/minus 90°, preferably up to plus/minus 45° in relation to the optimum installation position.  
         [0121]     Since lubricant is transported along with the refrigerant according to the invention, this entrained lubricant will also be supplied again, at least in part, via refrigerant drawn in.  
         [0122]     Lubricant is also supplied, for example, by way of refrigerant entering the compressor housing via a suction gas channel  240  and this lubricant will already be precipitated in the central suction gas channel  250  and then enters the branch channels  242 ,  244  leading to the cylinder banks  22 ,  24 .  
         [0123]     These branch channels  242 ,  244  have, for their part, as illustrated, in particular, in  FIGS. 2 and 7 , collecting areas  246 ,  248 , proceeding form which lubricant can enter the cylinder chamber  224  via discharge channels  250 ,  252  and from there can be guided to the pan  228  so that the lubricant again supplied to the refrigerant compressor by the refrigerant can also be collected in the collection chamber  230 .  
         [0124]     Finally, the refrigerant compressed in the refrigerant compressor flows via branch channels  256 ,  258  into a central pressure gas channel  260 , proceeding from which it exits from the compressor housing  10  via a pressure gas connection  162  ( FIGS. 3, 9 ).  
         [0125]     In order to insulate the central pressure gas channel  260  heated up by hot pressure gas in relation to the cylinder bores  98  and the suction gas channel  240 , hollow housing pockets  270  are integrally formed in the housing member  12  and these are connected to the cylinder chamber  224  only by a pressure compensation channel  272  so that the gaseous medium, which is essentially not swirled about in this channel but is, in particular, static, brings about a thermal insulation ( FIGS. 9, 10 ).