Abstract:
In order to improve a refrigerant compressor comprising a drive motor and a compressor unit which compresses a refrigerant entering through a suction inlet and allows it to exit through a pressure outlet in such a way that it works as reliably as possible, it is proposed that the refrigerant compressor comprise a compressor monitoring system which is integrated into a compressor control system and which determines a compressor condition by means of a first condition value that corresponds to a first saturation temperature in the suction inlet and a second condition value that corresponds to a second saturation temperature in the pressure outlet, and which compares the compressor condition with permissible compressor conditions lying in a given deployment field of a deployment diagram and initiates a process of switching-off the refrigerant compressor if the compressor condition departs from the deployment field.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application is a continuation of international application No. PCT/EP2013/055645 filed on Mar. 19, 2013. 
         [0002]    This patent application claims the benefit of international application No. PCT/EP2013/055645 of Mar. 19, 2013 and German application number 10 2012 102 405.7 of Mar. 21, 2012, 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 comprising a drive motor and a compressor unit which compresses a refrigerant entering through a suction inlet and allows it to exit through a pressure outlet. 
         [0004]    Refrigerant compressors of this type are usually compressors known from the state of the art. 
         [0005]    In refrigerant compressors of this type however, it is necessary to protect them from damage so that refrigerant compressors of this type should only be operated under permissible compressor conditions which are defined by a deployment field given in a deployment diagram. 
         [0006]    For this reason, refrigerant compressors of this type are partly operated by an external monitoring system which is described for example, in the user manual issued by the company CAREL Industries HQs, Via del Industria, 35020 Brugine-Padova (Italy), Manual Version: 1.6 dated Aug. 24, 2009 with the title “Standard Chiller Modular HP 1/4 Generic/Bitzer screw compressor and CAREL valve, Application program for pC0 1 , pC0 2 , pC0 3 ”. 
         [0007]    However, a combination of a refrigerant compressor and an external monitoring system of this type brings with it a multiplicity of problems since the deployment field in the external monitoring system does not necessarily agree with the permissible compressor conditions of the refrigerant compressor. 
         [0008]    Consequently, the working reliability of a refrigerant compressor of this type cannot be ensured. 
         [0009]    Consequently, the object of the invention is to improve a refrigerant compressor of the type described hereinabove in such a way that it works as reliably as possible. 
       SUMMARY OF THE INVENTION 
       [0010]    In accordance with the invention, this object is achieved in the case of a refrigerant compressor of the type described hereinabove in that the refrigerant compressor comprises a compressor monitoring system which is integrated into a compressor control system and determines a compressor condition by means of a first condition value that corresponds to a first saturation temperature in the suction inlet, and determines a second condition value that corresponds to a second saturation temperature in the pressure outlet, and which compares the compressor condition with permissible compressor conditions lying in a given deployment field of a deployment diagram and then causes the refrigerant compressor to switch off if the compressor condition leaves the deployment field. 
         [0011]    The advantage of the solution in accordance with the invention is to be seen in that, due to the integration of the monitoring system into the compressor control system in the form of the compressor monitoring system, it is ensured that the permissible compressor conditions within the given deployment field always correspond to the compressor conditions as provided by the manufacturer since in this case, due to the integration of the compressor monitoring system into the compressor control system by the manufacturer, the deployment field can be preset with the permissible compressor conditions so that all the sources of error which can occur in the case of a combination of an external control system with a refrigerant compressor are avoided. 
         [0012]    It is particularly expedient hereby, if the deployment field of the permissible compressor conditions is stored in a memory of the compressor monitoring system such as to be unchangeable by the user. 
         [0013]    A further advantageous solution envisages that the deployment field incorporating the permissible compressor conditions be preset in the compressor monitoring system for the specific compressor. 
         [0014]    This means that in this case, the manufacturer of the refrigerant compressor has the possibility of defining the deployment field specifically for the type of refrigerant compressor or for each individual refrigerant compressor and thus has the possibility of exhausting the possible compressor conditions on the one hand, but he also has the possibility of securely excluding critical compressor conditions and of doing it specifically for each type of refrigerant compressor or each individual refrigerant compressor on the other. 
         [0015]    In particular, provision is made in one embodiment for the compressor control system to comprise a motor control system for the speed-regulatable drive motor, and for the compressor monitoring system for switching-off the refrigerant compressor to cooperate directly with the motor control system thereof so that sources of error attributable thereto which arise in the case of external control systems can also be avoided. 
         [0016]    Up to this point, no details have been given in regard to the functioning of the compressor monitoring system. 
         [0017]    The previously described solution of the compressor monitoring system has the disadvantage that this compressor monitoring system only becomes active and initiates the process of switching-off the refrigerant compressor either directly or with a time delay if over-stepping of the deployment field is already occurring. 
         [0018]    In the course of the actual working time, this leads to a significant frequency of switching-off actions of the refrigerant compressor. 
         [0019]    In order to reduce the frequency at which the refrigerant compressor is switched-off, provision is preferably made for the compressor monitoring system to determine the relative position of the determined compressor condition with reference to a deployment boundary enclosing the deployment field and makes the information about the relative position of the compressor condition available at a control interface for a higher-level control system of a coolant circulation system. 
         [0020]    A higher-level control system can therefore intervene and try to hold the compressor condition in the deployment field before the deployment boundary is reached. 
         [0021]    Up to this point, no details have been given in regard to the process of detecting the compressor condition within the deployment field. 
         [0022]    Thus, one advantageous solution envisages that the compressor monitoring system determine the relative position of the determined compressor condition in the deployment field with reference to the deployment boundary by means of status zones which are defined in the deployment field and by virtue of the compressor monitoring system checking as to whether the compressor condition lies in one of these status zones or not. 
         [0023]    Due to the sub-division of the deployment field into different status zones, the possibility is then provided in a simple manner of characterizing the particular compressor condition and thus of determining the extent of the danger of the compressor condition leaving the deployment field or whether the compressor condition will remain in a harmless area of the deployment field. 
         [0024]    One status zone is, for example, defined as a normal operational zone within which there is no danger of the compressor conditions departing from the deployment field within a short period of time. 
         [0025]    For example thereby, one solution envisages that a status zone in the form of at least one warning zone adjoining the deployment boundary be defined in the deployment field, and that the compressor monitoring system check as to whether the compressor condition lies within the at least one warning zone, whereupon the compressor monitoring system then sends a message to the interface if the compressor condition lies in the at least one warning zone 
         [0026]    A particularly advantageous solution envisages that status zones in the form of a plurality of warning zones adjoining the deployment boundary be defined in the deployment field, and that the compressor monitoring system check as to whether the compressor condition lies in one of the warning zones, whereupon the compressor monitoring system then sends a message in the form of a warning signal characterizing the respective warning zone to the interface if the compressor condition lies in one of the warning zones. 
         [0027]    The advantage of this solution is to be seen in the fact that as a result of the sub-division into different warning zones, it is possible for a warning signal specific to a particular warning zone to be sent, this thereby indicating to the higher-level control system the warning zone within which the compressor condition momentarily lies so that the higher-level control system can react in a manner specific to that warning zone in order to prevent the compressor condition from leaving the deployment field. 
         [0028]    In the previously described solutions, the warning zones could be located such as to be spaced from the deployment boundary. 
         [0029]    It is particularly advantageous however, if the warning zones are defined as being directly adjacent to the deployment boundary in the deployment field so that the respective warning zones extend up to the respective deployment boundary. 
         [0030]    In principle moreover, there is also a possibility of only providing a warning zone in those areas of the deployment field that adjoin one or more deployment boundary sections that are frequently exceeded. 
         [0031]    A particularly expedient solution however envisages that at least one, and in particular a plurality of warning zones succeeding one another along the deployment boundary be arranged within the deployment boundary extending around the deployment field so that the compressor condition will fall into a warning zone before reaching each deployment boundary section whereupon the compressor monitoring system sends a message. 
         [0032]    Hereby, the most diverse types of warning zone are conceivable as the warning zones. 
         [0033]    For example, at least one or more of the warning zones defined in the following is provided as a warning zone: 
         [0000]    a warning zone for a low first saturation temperature,
 
a warning zone for a high second saturation temperature,
 
a warning zone for a high first saturation temperature,
 
a warning zone for a low second saturation temperature,
 
a warning zone for a low first saturation temperature and a high second saturation temperature,
 
a warning zone for a high first saturation temperature and a low second saturation temperature,
 
a warning zone for a low first saturation temperature and a low second saturation temperature,
 
a warning zone for a high first saturation temperature and a high second saturation temperature.
 
         [0034]    As an alternative to detecting the position of the compressor condition in the deployment field, a further advantageous solution envisages that the compressor monitoring system determine the relative position of the determined compressor condition in the deployment field in the form of a spacing from the deployment boundary and sends it to the interface as a message. 
         [0035]    Such a determination of the spacing of the compressor condition from the deployment boundary can be effected in the most varied of manners. 
         [0036]    The all-embracing solution would be that, proceeding from the compressor condition, the deployment boundary in every direction of the deployment diagram be determined and the nearest spacing be sent. 
         [0037]    A simplified solution however envisages that a determination of the spacing from at least one of the following deployment boundary sections be effected for determining the spacing of the compressor condition from the deployment boundary: 
         [0000]    a deployment boundary section which corresponds to a first low saturation temperature,
 
a deployment boundary section which corresponds to a high second saturation temperature,
 
a deployment boundary section which corresponds to a high first saturation temperature,
 
a deployment boundary section which corresponds to a low second saturation temperature,
 
a deployment boundary section which corresponds to a low first saturation temperature and corresponds to a high second saturation temperature,
 
a deployment boundary section which corresponds to a high first saturation temperature and corresponds to a low second saturation temperature,
 
a deployment boundary section which corresponds to a high first saturation temperature and corresponds to a high second saturation temperature,
 
a deployment boundary section which corresponds to a low first saturation temperature and corresponds to a low second saturation temperature.
 
         [0038]    Moreover, a further advantageous embodiment of the compressor monitoring system envisages that it determine the temporal change in the spacing of the compressor condition from the deployment boundary. 
         [0039]    The determination of the temporal change in the spacing from the deployment boundary has the advantage that there is then the possibility of recognizing the temporal behaviour of the compressor condition and in particular, recognizing the temporal behaviour of a change in the compressor condition so that the higher-level control system has the possibility of reacting in a timely manner in order to hold the compressor condition in the deployment field. 
         [0040]    A further advantageous solution envisages that the compressor monitoring system determine a temperature of the lubricant in order to ensure that the lubricant does not become too hot and thereby strip away the lubricant film in the bearings for example. 
         [0041]    In particular, provision is made for the compressor monitoring system to initiate a process of switching-off the refrigerant compressor if a lubricant limit temperature is exceeded. 
         [0042]    For example, it would be conceivable to initiate the process of switching-off the refrigerant compressor immediately or following a delay. 
         [0043]    However, in order to avoid having switching-off processes of this type insofar as possible, provision is preferably made for the compressor monitoring system to determine the relative spacing of the lubricant temperature from the lubricant limit temperature and in particular to send a message in the event that the lubricant limit temperature is approached. 
         [0044]    For example, the spacing from the lubricant limit temperature can be determined in that, in the event of the lubricant temperature reaching a temperature range lying below the lubricant limit temperature, a lubricant temperature warning is sent by the compressor monitoring system to the interface for the higher-level control system. 
         [0045]    Another possibility envisages that the compressor monitoring system determine the spacing of the lubricant temperature from the lubricant limit temperature and send it as a message to the interface. 
         [0046]    A further advantageous embodiment of the solution in accordance with the invention envisages that the compressor monitoring system monitor a motor temperature and initiate a process of switching-off the refrigerant compressor in the event that a motor limit temperature is exceeded. 
         [0047]    For the purposes of reducing the frequency at which a switching-off process occurs, provision is preferably made for the compressor monitoring system to send a motor temperature warning to the interface if the motor temperature reaches a temperature range lying below the motor limit temperature so that, if necessary, the higher-level control system is still able to initiate measures for lowering the motor temperature. 
         [0048]    Another advantageous solution envisages that the compressor monitoring system detect a lubricant level and in the event of it falling below a lubricant lower limit, the compressor control system then initiates a process of switching-off the refrigerant compressor. 
         [0049]    This, for example, is possible in that a minimum lubricant level detecting sensor is provided and in that the compressor control system initiates the process of switching-off the refrigerant compressor if this sensor detects that the lubricant level lies below a lubricant lower limit. 
         [0050]    A further object of the invention is to provide a compressor monitoring system which enables improved operation of the refrigerant compressor. 
         [0051]    This object is achieved by a compressor monitoring system in accordance with claim  21 . 
         [0052]    The advantage of this solution is that the frequency at which the refrigerant compressor switches off can be reduced thereby. 
         [0053]    Further advantageous developments form the subject matter of claims  22  to  39 . 
         [0054]    Furthermore, the further object is also achieved by a method for monitoring a compressor in accordance with claim  40 . 
         [0055]    Further advantageous developments of the method form the subject matter of claims  41  to  56 . 
         [0056]    Further features and advantages of the invention form the subject matter of the following description as well as the graphic illustration of some exemplary embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0057]      FIG. 1  shows a perspective view of a refrigerant compressor in accordance with the invention; 
           [0058]      FIG. 2  a view in the direction of the arrow A in  FIG. 1 ; 
           [0059]      FIG. 3  a section along the line  3 - 3  in  FIG. 2 ; 
           [0060]      FIG. 4  a section along the line  4 - 4  in  FIG. 2 ; 
           [0061]      FIG. 5  a schematic illustration of a coolant circulation system incorporates a refrigerant compressor; 
           [0062]      FIG. 6  an illustration of a deployment field of compressor conditions in a deployment diagram in a first embodiment; 
           [0063]      FIG. 7  an illustration similar to  FIG. 6  of an exemplary implementation of a second embodiment; 
           [0064]      FIG. 8  an illustration similar to  FIG. 6  of a further exemplary implementation of the second embodiment; 
           [0065]      FIG. 9  a schematic illustration of a system for monitoring lubricant temperature and 
           [0066]      FIG. 10  a schematic illustration of a system for monitoring motor temperature. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0067]    An exemplary embodiment of a refrigerant compressor  10  in accordance with the invention which is illustrated in  FIGS. 1 to 3  comprises a common housing  11  which includes a compressor housing  12 , a motor housing  14  arranged on a side of the compressor housing  12  and a pressure housing  16  arranged on a side of the compressor housing  12  opposite the motor housing  14 . Hereby, the compressor housing  12 , the motor housing  14  and the pressure housing  16  may be separate parts of the common housing  11  and are put together in order to form the latter or the compressor housing  12  and the motor housing  14  and/or the compressor housing  12  and the pressure housing  16  could be formed as connected parts. 
         [0068]    Furthermore, the motor housing  14  carries a control system housing  18  in the region of a partial periphery. 
         [0069]    As is illustrated in  FIG. 3 , the motor housing  14  surrounds a motor compartment  20  and is closed at the end thereof remote from the compressor housing  12  by an end face cover  22  which forms an end-face wall of the motor housing  14  and which, for its part, is provided with a suction gas connector  24  through which the refrigerant that is to be sucked to the refrigerant compressor is suppliable. 
         [0070]    As is illustrated in  FIG. 1 , the suction gas connector  24  is preferably provided with a shut-off valve  26  which is connected to a suction gas line leading to the refrigerant compressor but is not illustrated in the drawings. 
         [0071]    The pressure housing  16  is connected to the compressor housing  12  in releasable manner, namely, by means of a pressure housing flange  34  which is connectable to a mounting flange  36  of the compressor housing  12 , whereby, commencing from the pressure housing flange  34 , the pressure housing  16  extends in the form of a cylindrical capsule  38  that is closed at the end thereof by an end wall  48 . 
         [0072]    Furthermore, the pressure housing  16  carries a pressure outlet  42  on which a compressed-gas-side shut-off valve  44  is mountable. 
         [0073]    Furthermore, the capsule  38  is preferably closed in accessible manner in the region of the end wall  48  thereof opposite the compressor housing  12  by an access cover  46  ( FIG. 1 ). 
         [0074]    As is illustrated in  FIG. 3 , an electric motor bearing the general reference  50  is seated in the motor housing  14 , a stator  52  is arranged fixedly in the motor housing  14  and there is also a rotor  56  which is mounted rotatably about a motor axis  54  relative to the stator  52 , wherein the rotor  56  is seated on a drive shaft  58 . 
         [0075]    The drive shaft  58  passes through the rotor  56  in the direction of the motor axis  54  on the one hand and extends into the compressor housing  12  of a screw-type compressor bearing the general reference  60  on the other. 
         [0076]    In the region thereof extending within the compressor housing  12 , the drive shaft  58  carries a compressor rotor  62  which is arranged in the compressor housing  12  in a compressor rotor boring  64  and is rotatable therein about a rotational axis  63  coinciding with the motor axis  54 . 
         [0077]    Moreover, the drive shaft  58  extends on the side thereof opposite the electric motor  50  beyond the compressor rotor  62  and forms an end section  66  which is rotatably mounted in a bearing housing  16  arranged within the pressure housing  68 , wherein a set of bearings  72  is provided in the bearing housing  68  on the pressure-side for this purpose. 
         [0078]    Furthermore, the drive shaft  58  is mounted between the compressor rotor  62  and the rotor  56  in a suction-side set of bearings  74  adjoining the suction-side of the compressor rotor  62 . 
         [0079]    For example, the suction-side set of bearings  74  is held on a suction-side wall  76  of the compressor housing  12 , whilst the pressure-side set of bearings  72  is held on a pressure-side wall  78 , wherein the bearing housing  68  is carried by the pressure-side wall  78  for this purpose. 
         [0080]    For the purposes of accurately guiding the rotor  56  coaxially relative to the motor axis  54 , the drive shaft  58  comprises another end section  82  which extends beyond the rotor  56  and which, for its part, is mounted in a guide bearing  84  that is seated in a bearing seating  86  arranged coaxially relative to the motor axis  54  and fixed to the motor housing  14 , namely, close to the cover  22 . 
         [0081]    The bearing seating  86  could thus be supported directly on the motor housing  14  independently of the cover  22 . 
         [0082]    Preferably, as illustrated in  FIG. 2 , the bearing seating  86  is held on the cover  22 , wherein the bearing seating  86  is held spaced from a cover base  92  by means of a plurality of bars. 
         [0083]    Preferably, a suction gas filter  98  through which the suction gas must flow is arranged in an interior space  100  surrounding the bearing seating  86 . 
         [0084]    As illustrated in  FIG. 3  by dashed lines, the suction gas flows from the shut-off valve  26  in a direction parallel to the motor axis  54  through the suction gas connector  24  and a suction opening  94  into an in-flow space  90  forming a suction inlet which is arranged between the suction opening  94  and the bearing seating  86 . 
         [0085]    From the in-flow space  90 , a component of the suction gas running at an angle to the motor axis  54  then flows through the in-flow openings  96  into the interior space  100  thereby forming a plurality of flow paths, whereby suction-side head windings  102  of the stator  52  are subjected to a gas flow for example. 
         [0086]    Preferably, the suction opening  94  is arranged in the cover  22  in such a manner that the motor axis  54  passes therethrough, and in particular, the suction opening  94  is arranged coaxially with respect to the motor axis  54  so that flow states that are approximately rotationally symmetrical with respect to the motor axis  54  develop in the region of the interior space  100  and the bearing seating  86 . 
         [0087]    After flowing through the recesses  106  and the gap  108 , the suction gas collects in the region of the head windings  112  of the stator  52  facing the compressor housing  12  in an interior space  116  of the motor housing  14  on the compressor housing side and is thus able to also cool these head windings  112  before the sucked-in gas or refrigerant passes through break-throughs  114  provided in the suction-side wall  76  of the compressor housing  12  as illustrated in  FIG. 10 , and thereby enters a suction space  118  of the compressor housing  12 . 
         [0088]    As illustrated in  FIG. 3  and  FIG. 4 , apart from the first compressor rotor  62 , provision is made for yet another, a second compressor rotor  122  which is arranged in a compressor rotor boring  120  and co-operates with the first one, wherein the second compressor rotor  122  is also mounted in a pressure-side set of bearings  126  about a rotational axis  123  that is parallel to the motor axis  54  and the rotational axis  63  by means of a bearing shaft  124  which extends beyond the compressor rotor  122  and is mounted in a suction-side set of bearings  128 . 
         [0089]    In operation, the two compressor rotors  62  and  122  now co-operate in such a manner that refrigerant or gas is sucked in from the suction space  118 , compressed by the inter-engaging compressor rotors  62  and  122  and then, as a compressed gas or refrigerant, it exits into the compressor housing  12  in the region of a pressure-side outlet window  132  that is defined by the pressure-side free-standing peripheral regions and the end-face regions of the compressor rotors  62 ,  122  and passes on from the compressor housing  12  through a housing window  133  into the pressure housing  16 . 
         [0090]    Furthermore, for the purposes of adjusting the volume ratios, another slider gate valve  134  is provided, the construction and functioning of which are described in the German patent application 10 2011 051 730.8 for example. 
         [0091]    In order to dampen the pressure pulsations of the compressed gas or refrigerant emerging through the outlet window  132 , there is provided in the pressure housing  16  directly adjoining the housing window  133 , a first sound absorber unit  140  which comprises a receiving chamber  138  that directly adjoins the housing window  132 , an inlet opening  142  that is arranged on a side of the receiving chamber  138  opposite the housing window  132  and an outlet opening  144  through which a flow is able to take place, in particular, in a direction of flow  146  directed transversely to the pressure-side wall  78  and away therefrom, especially parallel to the motor axis  54 . 
         [0092]    Following the first sound absorber unit  140 , there is for example, yet another, a second sound absorber unit  160  which comprises a transverse flow chamber  162  which directly adjoins the outlet opening  144  and through which the compressed gas or refrigerant emerging from the first sound absorber unit  140  can flow in a direction of flow  164  running transversely relative to the direction of flow  146  in the direction of an outlet  166  of the second sound absorber unit  160  from which the compressed gas or refrigerant is then fed in a channel  168 , formed for example by a pipe  172 , up to the end wall  48  of the capsule  38  where it emerges radially through openings  174  in the pipe  172  and enters the pressure space  176  of the pressure housing  16  enclosing the pipe  172 . 
         [0093]    Surrounding the channel  168  and in particular the pipe  172 , there is arranged in the pressure space  176  of the pressure housing  16  a lubricant separating unit  180  which, for example, comprises two sets of porous gas-permeable structures  182  and  184 , made of metal for example, which cater for the separation of lubricant spray from the pressurised gas or refrigerant. 
         [0094]    After flowing through the lubricant separating unit  180 , it is then possible for the pressurised gas or refrigerant to emerge from the pressure housing  16  through the pressure outlet  42 . 
         [0095]    The lubricant collecting in the lubricant separating unit  180  forms a lubricant bath  190  located, in the direction of the force of gravity, in the lower region of the pressure housing  16  and the compressor housing  12 , and from there lubricant is taken, filtered by a filter  192  and then used for lubricating purposes ( FIG. 3 ). 
         [0096]    In the control system housing  18 —as illustrated in FIG.  5 —, there is provided a compressor control system which bears the general designation  200  and comprises a motor control system  202  incorporating a converter  204  and a converter control system  206 , and there is also provided a compressor monitoring system  210  which detects a compressor condition. 
         [0097]    To this end, the compressor monitoring system  210  is coupled to a pressure sensor  212  ( FIGS. 3 and 5 ) which is arranged in the in-flow space  90  forming the suction inlet of the refrigerant compressor and detects a pressure in the suction inlet that is also referred to as the compressor input pressure which corresponds to a first saturation temperature S1 that may also be referred to as the evaporation temperature. 
         [0098]    Furthermore, there is provided in the pressure housing  16  a pressure sensor  214  which is located close to the pressure outlet  42  for example and measures a pressure in the pressure outlet  42  which corresponds to a second saturation temperature S2 that may also be referred to as the liquefaction temperature. 
         [0099]    In addition, the compressor monitoring system  210  also has another temperature sensor  216  associated therewith, this likewise being arranged in the pressure housing  16  and is used for measuring the lubricant temperature ST of the lubricant bath  190 . 
         [0100]    Moreover, the compressor monitoring system  210  has yet another temperature sensor  220  associated therewith, this being used to measure a motor temperature MT of the electric motor  50 , at its head windings  102 ,  112  for example. 
         [0101]    Finally, the compressor monitoring system  210  also has a lubricant level sensor  218  associated therewith, this being capable of detecting the quantity of lubricant in the lubricant bath  190  ( FIGS. 3 and 5 ), wherein this process is effected either by detecting a mirror surface  194  of the lubricant bath  190  or, in the simplest case, is effected in that the lubricant level sensor  218  merely detects whether the lubricant bath  190  exceeds a minimum lubricant level ( FIG. 5 ). 
         [0102]    From the values of the pressure sensors  212  and  214 , the compressor monitoring system  210  now determines a compressor condition VZ which is defined by the first saturation temperature ( 51 ) in the suction inlet  90  and the second saturation temperature S2 in the pressure outlet  42 , which condition must lie within a deployment field EF that is enclosed by a deployment boundary EG in a deployment diagram which is illustrated in  FIG. 6  in order to enable damage-free operation of the refrigerant compressor  10 , wherein the first saturation temperature S1 at the suction inlet  90  is plotted along the x axis and the second saturation temperature S2 at the pressure outlet  42  is plotted along the y axis ( FIG. 6 ). 
         [0103]    Deployment diagrams for refrigerant compressors of this type are described for example in the book “Lexikon der Kältetechnik” by Dieter Schmidt (Hrsg) published by C F. Mueller to which reference is made in regard thereto. 
         [0104]    All of the compressor conditions VZ which lie in the deployment field EF within the deployment boundary EG thus represent permitted compressor conditions VZ that are harmless for operation of the refrigerant compressor, and under these conditions, operation of the refrigerant compressor  10  may be effected by the operator. 
         [0105]    Hereby, the deployment boundary EG represents a closed bounding border of the deployment field EF so that the deployment field EF is unambiguously defined in the deployment diagram, 
         [0106]    When the current refrigerant compressor  10  is running, the compressor monitoring system  210  now determines continuously or possibly at given time intervals the compressor condition VZ and compares the determined compressor condition VZ with the compressor conditions VZ permitted by the deployment field EF. 
         [0107]    If the compressor monitoring system  210  establishes that the compressor condition VZ of the refrigerant compressor has wandered out of the deployment field EF and lies outside the deployment boundary EG such as the compressor condition VZ1 for example, then the compressor monitoring system  210  initiates a process of switching-off the refrigerant compressor  110 , in particular, by switching-off the electric motor  50 . In the simplest case, this switching-off process may be an immediate switch-off process or it could be a delayed switching-off process at the expiry of a delay period Δt. 
         [0108]    In the case of a delayed switching-off process, the compressor monitoring system  210  determines the time point t1 at which the deployment boundary EG was overstepped and delivers over an interface  242  a boundary message GM to a higher-level control system  230  for a refrigerant circulation system  232  in which the refrigerant compressor in accordance with the invention  10  is being operated and which, following on from the refrigerant compressor  10  in the refrigerant circulation system  232 , comprises a liquefier  234  an expansion valve  236  and an evaporator  238  which are controllable by the higher-level control system  230 . 
         [0109]    If the higher-level control system  230  is in the position of intervening rapidly in the refrigerant circulation system  232 , then the possibility exists for the compressor condition VZ1 to change back again to a compressor condition VZ2 which again lies within the deployment field EF, whereupon a process of switching-off the refrigerant compressor  10  does not take place if the transition to the compressor condition VZ2 has taken place at a time point t2 whose separation in time from the time point t1 is smaller than the delay period Δt. 
         [0110]    However, if the compressor condition VZ1 remains outside the deployment field EF or if, after a certain time, it changes to a compressor condition VZ3 which lies still further outside the deployment field EF, then the process of switching-off the refrigerant compressor  10  takes place at the expiry of the delay period Δt, whereby, for this purpose, the compression monitoring system  210  conveys a switch-off signal AS to the motor control system  202 . 
         [0111]    The deployment boundary EG in the deployment diagram of  FIG. 6  may itself be enclosed by an absolute deployment boundary AEG which runs outside the deployment field EF and outside the deployment boundary EG at a spacing from the deployment boundary EG. In this case, the compressor monitoring system  210  works in such a way that if the compressor condition VZ4 lies outside the absolute deployment boundary AEG then an immediate process of switching-off the refrigerant compressor  10  takes place without further delay by means of the issuance of the switch-off signal AS from the compressor monitoring system  210 . 
         [0112]    This means for example, that even if at first only the compressor condition VZ1 lies outside the deployment boundary EG but the compressor condition VZ4 is reached before the expiry of the delay period Δt, then an immediate process of switching-off the refrigerant compressor  10  by the issuance of the switch-off signal AS takes place before expiry of the delay period Δt. 
         [0113]    In the solution in accordance with the invention, the deployment field EF, the deployment boundary EG and the absolute deployment boundary AEG are set by the factory on a compressor-specific basis such as to be unchangeable by the user and fixedly stored in a memory  240  associated with the compressor monitoring system  210  so that a user of the refrigerant compressor  10  in accordance with the invention cannot affect the position of the deployment boundary EG and the absolute deployment boundary AEG, but, during use of the refrigerant compressor  10  in accordance with the invention, works in the deployment field EF laid down by the manufacturer and it can thereby be ensured that the refrigerant compressor  10  will not suffer damage when in operation. 
         [0114]    Thus the first embodiment of the compressor monitoring system  210  described in connection with  FIG. 6  only reacts when the deployment boundary EG or the absolute deployment boundary AEG is exceeded so that even upon the issuance of the border message GM, the higher-level control system  230  cannot repeatedly control the refrigerant circulation system  232  in such a way that the process of switching-off the refrigerant compressor  10  will be prevented. 
         [0115]    For this reason, provision is advantageously made in a second improved embodiment of the compressor monitoring system  210  for the compressor monitoring system  210  to detect the relative position of the compressor condition VZ in the deployment field EF relative to the deployment boundary EG. 
         [0116]    Thereby, this process for detecting the compressor condition VZ within the deployment field EF relative to the deployment boundary EG can be effected in the most varied of manners. 
         [0117]    In a first exemplary embodiment that is illustrated in  FIG. 7 , a plurality of status zones are defined within the deployment field EF, the status zones Z1 to Z9 for example. Here, the status zone Z1 represents a zone in which no reaction of the compressor monitoring system  210  is necessary because all the compressor conditions V2 are located within the status zone Z1 well away from the deployment boundary EG so that the higher-level control system  230  does not have to consider the compressor condition VZ during operation of the refrigerant circulation system  232 . 
         [0118]    Thus, if the compressor monitoring system  210  determines that the compressor condition VZ lies within the status zone Z1, then no measures are necessary on the part of the compressor monitoring system  210 . The status zone Z1 is therefore referred to as the normal operating zone. 
         [0119]    In contrast thereto, the status zones Z2, Z3, Z4, Z5, Z6, Z7, Z8 and Z9 are located within the deployment field EF directly adjacent the deployment boundary EG and represent warning zones, i.e. if the compressor condition VZ lies within one of these warning zones Z2, Z3, Z4, Z5, Z6, Z7, Z8 and Z9, then the compressor monitoring system  210  will always send a message M via the interface  242  to the higher-level control system  230 . 
         [0120]    However, as a uniform message M for all the warning zones Z2 to Z9 would not indicate to the higher-level control system  230  the particular side of the deployment boundary EG that the compressor condition VZ is approaching, the warning zones Z2 to Z9 define mutually separate warning zones in one exemplary embodiment so that differing warning signals W2 to W9 will be delivered as a message M in dependence on the warning zone Z2 to Z9 into which the compressor condition VZ has entered. 
         [0121]    For example, if the compressor condition VZ occurs in the warning zone Z2, then a warning signal W2 is sent which conveys the information to the higher-level control system  230  that the first saturation temperature S1 at the suction inlet  90  is low so that in the event of further lowering of the first saturation temperature S1 the danger exists that the compressor condition VZ will over-step the deployment boundary EG in the direction of too low a first saturation temperature. 
         [0122]    Consequently, the higher-level control system  230  is then in a position to initiate the necessary measures for increasing the first saturation temperature S1. 
         [0123]    Measures of this type which the higher-level control system  230  can initiate in the refrigerant circulation system are, for example, an increase of the compressor power or an increase in the mass flow. 
         [0124]    By contrast, if the compressor condition VZ occurs in the warning zone Z3 then the warning signal W3 is sent which conveys to the higher-level control system  220  that the first saturation temperature S1 at the suction inlet  90  is low and the second saturation temperature S2 at the pressure outlet  42  is high. 
         [0125]    In this case too, the higher-level control system  230  can initiate the necessary measures, for example, reducing the compressor power, lowering the temperature of the liquefier  234  or possibly defrosting the evaporator  238 . 
         [0126]    Should the compressor condition VZ enter the warning zone Z4, then the warning signal W4 is sent which conveys to the higher-level control system  220  that although the first saturation temperature S1 at the suction inlet  90  is correct, the second saturation temperature S2 at the pressure outlet  42  is high. 
         [0127]    In this case, the higher-level control system  230  has the possibility of either reducing the compressor power or lowering the temperature of the liquefier  234 . 
         [0128]    Should the compressor condition VZ enter the warning zone Z5, then the warning signal W5 is sent. By virtue of this warning signal W5, the higher-level control system  230  is informed that the first saturation temperature S1 at the suction inlet  90  is high, although the second saturation temperature at the pressure outlet  42  lies within the tolerable range. 
         [0129]    Upon entry of the compressor condition VZ into the warning zone Z6, the warning signal W6 is emitted which conveys to the higher-level control system  230  that the first saturation temperature S1 in the suction inlet  90  is high and the second saturation temperature S2 at the pressure outlet  42  is low. 
         [0130]    For the case where the compressor condition VZ enters the warning zone Z7, the higher-level control system  230  is informed that the first saturation temperature S1 in the suction inlet  90  lies in a tolerable range, but that the second saturation temperature S2 in the pressure outlet  42  is low. 
         [0131]    The warning zones Z2 and Z7 could border each other. 
         [0132]    In order to obtain even better information about the compressor condition VZ in the border area between the warning zone Z2 and the warning zone Z7, there is provided the warning zone Z8, whereby if the compressor condition VZ occurs therein, the warning signal W8 is sent which conveys to the higher-level control system  230  that the first saturation temperature S1 and the second saturation temperature S2 are low. 
         [0133]    Finally, an additional warning zone Z9 may also be provided between the warning zone Z4 and the warning zone Z5 so that should the compressor condition VZ occur therein, the warning signal W9 is sent which advises of a high first saturation temperature S1 and a high saturation temperature S2. 
         [0134]    As an alternative or in addition to the functioning of the compressor monitoring system in accordance with the invention described thus far, provision is made in a second exemplary embodiment that is illustrated in  FIG. 8  for the compressor monitoring system  210  to determine the spacing TA from the deployment boundary EG in the case of every compressor condition VZ lying in the deployment field EF within the deployment boundary EG. 
         [0135]    This is effected for example in that the compressor condition VZ of individual deployment boundary sections EG1U, EG2O, EG1O or else EG1U2O or EG1O2U of the deployment boundary EG have a spacing TA which defines the relative position of the compressor condition VZ with respect to the deployment boundary EG. 
         [0136]    These relative spacings TA of the respective compressor condition VZ are indicated, in the case of the direction parallel to the axis S1 of the deployment diagram for example, as spacing TA1U, i.e. the temperature difference to the lower deployment boundary EG1U, and as spacing TA10, i.e. the temperature difference to the upper deployment boundary EG1O. 
         [0137]    Furthermore, the compressor monitoring system  210  determines the relative spacing of the respective compressor condition VZ from the lower deployment boundary EG2U as spacing TA2U and the relative spacing from the upper deployment boundary EG2O as spacing TA2O in the case of the direction parallel to the axis S2 of the deployment diagram. 
         [0138]    This means that the compressor monitoring system  210  generates four spacing values TA1U, TA10, TA2U and TA2O for example and conveys them constantly or at time intervals in the form of a message M to the higher-level control system  230  so that, on the basis these spacing values TA1U, TA10, TA2U, TA2O, the higher-level control system  230  is itself in a position to determine whether the compressor condition VZ is approaching the deployment boundary EG or is sufficiently far enough away therefrom. When processing these spacing values independently, the higher-level control system  230  is in a position, in accord with the inertial parameters of the refrigerant circulation system  232  in which the refrigerant compressor in accordance with the invention  10  is incorporated, to take timely measures for preventing the compressor condition VZ from over-stepping the deployment boundary EG before the compressor condition VZ actually reaches the deployment boundary EG. 
         [0139]    As an alternative or in addition thereto however, there is also the possibility in this exemplary embodiment of detecting the relative spacing of the compressor condition VZ from the deployment boundary EG even more precisely, for example, by additionally detecting yet another spacing from a deployment boundary section EG1U2O which runs between the deployment boundary section EG1U and EG2O, or else additionally detecting yet another spacing from a deployment boundary section EG1O2U which runs between the deployment boundary section EG1O and the deployment boundary section EG2U, or detecting a spacing from a deployment boundary section EG1U2U or from a deployment boundary section EG2O1O. 
         [0140]    Moreover, it is also possible for the compressor monitoring system  210  itself to determine not just the spacings TA but also the temporal change of the spacings TA in order to thereby detect alterations in the compressor condition VZ with respect to time and, in this context, to likewise convey yet more information regarding the temporal changes in the compressor condition VZ to the higher-level control system  230  so that the latter is in a still better position to prevent the compressor condition VZ reaching the deployment boundary EG by timely control of the refrigerant circulation system  232  incorporating the refrigerant compressor  10 , the liquefier  234 , the expansion valve  236  and the evaporator  238 . 
         [0141]    Furthermore, the compressor monitoring system  210  also monitors the temperature ST of the lubricant bath  190  with the aid of the temperature sensor  216 . 
         [0142]    For this purpose as is illustrated in  FIG. 9 , a lubricant limit temperature SGT is stored in the memory  200 , the compressor monitoring system  210  comparing the lubricant temperature ST therewith. 
         [0143]    Thereby, if the lubricant temperature ST exceeds the lubricant limit temperature SGT, then the process of switching-off the refrigerant compressor  10  is triggered immediately, namely, in that the compressor monitoring system  210  sends the switch-off signal AS. 
         [0144]    In order not to open up the possibility of the higher-level control system  230  initiating timely measures for the reduction of the lubricant temperature ST prior to the lubricant limit temperature SGT being exceeded by the lubricant temperature ST, there is provided a temperature range TBS below the lubricant limit temperature SGT with which the compressor monitoring system  210  likewise compares the lubricant temperature ST. 
         [0145]    If the compressor monitoring system  210  determines that the lubricant temperature ST has reached the temperature range TBS, then the compressor monitoring system  210  generates a message MS which conveys this information to the higher-level control system  230  via the interface  242  so that the higher-level control system  230  can react accordingly. 
         [0146]    Moreover, the compressor control system  210  also monitors the motor temperature MT of the electric motor  50 . 
         [0147]    This motor temperature MT is compared with a motor limit temperature MGT which is stored in the memory  240 , and the compressor monitoring system  210  then triggers the process of switching-off the refrigerant compressor  10  by emitting the switch-off signal AS if the motor temperature MT exceeds the motor limit temperature MGT. 
         [0148]    In order to open up the possibility for the higher-level control system  230  to react if necessary to a rise of the motor temperature MT into a range close to the motor limit temperature MGT, there is provided a temperature range TBM below the motor limit temperature MGT which is likewise fixedly defined and stored in the memory  240 . 
         [0149]    In like manner, the compressor monitoring system  210  compares the motor temperature MT with the temperature range TBM and then triggers the sending of a message MM if the motor temperature reaches the temperature range TBM or lies within it, said message conveying the information to the higher-level control system  230  that the motor temperature MT now lies close to the motor limit temperature MGT so that the higher-level control system  230  still has the possibility of reacting if necessary in order to lower the motor temperature MT. 
         [0150]    Moreover, the compressor monitoring system  210  also monitors the quantity of the lubricant by means of the lubricant level sensor  218 . 
         [0151]    For example, the lubricant level sensor  218  can work in such a way that it detects whether the lubricant bath exceeds the minimum lubricant level and, for the case where this is not so, it triggers the message MMS and conveys it to the higher-level control system  230 . 
         [0152]    After transmission of the message MMS, the process of switching-off the refrigerant compressor  10  by the switch-off signal AS can also be triggered off if necessary. 
         [0153]    There is also the possibility of switching-off the refrigerant compressor  10  by means of the switch-off signal AS as soon as the lubricant bath  190  falls below the minimum lubricant level. 
         [0154]    If the lubricant level sensor  218  is working in such a way that it continuously detects the lubricant level in the lubricant bath  190 , then the message MMS can likewise be sent in good time to the higher-level control system  230  before the minimum lubricant level is reached as the lubricant level approaches the minimum lubricant level so that an indication can be given to the operator of the refrigerant circulation system  232  that maintenance is necessary. 
         [0155]    During a start-up phase of the refrigerant compressor  10  in all the exemplary embodiments and the embodiments, provision may be made for the compressor monitoring system  210  not to initiate the process of switching-off the drive motor  50  and not sending information to the higher-level control system  230  in order to enable the refrigerant compressor  10  to reach a compressor condition VZ in the deployment field EF in current-free manner. 
         [0156]    Once the compressor condition VZ has reached the deployment field EF, the compressor monitoring system can then implement the previously described functions.