Patent Publication Number: US-9410547-B2

Title: Compressor with oil separator and refrigeration device including the same

Description:
TECHNICAL FIELD 
     The present invention relates to a compressor and to a refrigeration device; more particularly, the present invention relates to a compressor provided with a mechanism for returning, to the compressor, lubricating oil included in refrigerant discharged from the compressor, as well as to a refrigeration device provided with the compressor. 
     BACKGROUND ART 
     In general, in a compressor constituting a refrigerant circuit for performing a refrigeration cycle, lubricating oil (refrigerator oil) is used in order to enhance the lubricating performance of a sliding part of a compression mechanism in the interior of the compressor. For this reason, the lubricating oil is included in refrigerant discharged from the compressor. However, when the refrigerant containing the lubricating oil flows into a refrigerant circuit on the exterior of the compressor, a problem emerges in that there is a deficit of lubricating oil in the interior of the compressor and poor lubrication of the sliding part, and in that the lubricating oil sticks to a heat transfer tube in the interior of a condenser and a heat transfer action is inhibited, and others. In view whereof, there has been proposed in the past a configuration for separating out the lubricating oil from the refrigerant compressed in the compressor and for returning the lubricating oil to the compressor, in order to prevent the refrigerant containing the lubricating oil from circulating through the refrigerant circuit. 
     For example, Patent Literature 1 (Japanese Unexamined Publication No. 5-223074) recites a scroll-type compressor which is connected to an oil separator for separating out lubricating oil from refrigerant discharged from the compressor. A discharge tube installed on an upper surface of a casing of this scroll compressor is in direct communication with the oil separator, which is installed on the exterior of the compressor. Refrigerant discharged from the discharge tube is sent to the interior of the oil separator and passes through oil separating means in which a fine metal wire is formed in a roll, the lubricating oil being thus separated. The lubricating oil separated out from the refrigerant is stored in an oil reservoir chamber in the interior of the oil separator. This oil reservoir chamber communicates with a space at an upper part of the oil reservoir chamber in the interior of the compressor, via an oil return flow path, which has resistance. As such, the lubricating oil stored in the oil reservoir chamber in the interior of the oil separator is returned to the oil reservoir chamber in the interior of the compressor, via the oil return flow path. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     However, in a conventional scroll compressor, lubricating oil which has been compressed and brought to a high temperature will be returned to a space in the interior of the compressor filled with as-yet uncompressed, low-temperature refrigerant. For this reason, in the conventional scroll compressor, the as-yet uncompressed, low-temperature refrigerant is heated by the high-temperature lubricating oil, and a problem emerges in that compressing the refrigerant, which has been expanded by the heating, leads to a considerable decline in volumetric efficiency. 
     An objective of the present invention is to provide a compressor whereby any decline in volumetric efficiency can be suppressed in a process for returning, to the interior of the compressor, high-temperature lubricating oil having been separated out by an oil separator. 
     Solution to Problem 
     A compressor according to a first aspect of the present invention is provided with a casing, a compression mechanism, an oil separator, and an oil return passage. The casing stores lubricating oil in a bottom part. The compression mechanism is accommodated in the interior of the casing. The oil separator is installed on the exterior of the casing. The oil separator separates out lubricating oil from high-pressure refrigerant discharged from the compression mechanism. The lubricating oil separated out by the oil separator flows through the oil return passage. The oil return passage communicates with a high-pressure space formed in the interior of the casing. The high-pressure refrigerant flows into the high-pressure space. 
     In the compressor according to the first aspect, the lubricating oil is separated out by the oil separator from the refrigerant compressed by the compression mechanism, and the separated-out lubricating oil is returned directly to the high-pressure space in the interior of the casing by way of the oil return passage. This high-pressure space is a space where refrigerant compressed by the compression mechanism is discharged. As such, in the compressor according to the first aspect, unlike the conventional compressor, the lubricating oil separated out by the oil separator will not be returned to a low-pressure space filled with as-yet uncompressed refrigerant, and therefore the as-yet uncompressed refrigerant will not be heated and expanded by the high-temperature lubricating oil. This makes it possible for any decline in volumetric efficiency to be suppressed in the compressor according to the first aspect. 
     Further, in the compressor according to the first aspect, there is little difference in pressure between the high-pressure space and the oil return passage, through which the lubricating oil separated out by the oil separator flows. As such, there is no longer a need for a capillary tubing or other pressure adjustment mechanism, which has been necessary in a conventional compression mechanism in order to return only a suitable amount of lubricating oil to the low-pressure space filled with as-yet uncompressed refrigerant. This makes it possible to achieve a cost reduction based on a reduced number of components in the compressor according to the first aspect. 
     A compressor according to a second aspect of the present invention is the compressor according to the first aspect, further provided with an ejector mechanism formed in the high-pressure space. The ejector mechanism has a refrigerant-accelerating flow path and an oil suction flow path. The high-pressure refrigerant flows in the refrigerant-accelerating flow path via a narrowed part, whereby a flow rate of the high-pressure refrigerant is increased. The oil suction flow path communicates with the oil return passage, the lubricating oil being sucked from the oil return passage into the oil suction flow path. The oil suction flow path merges with the refrigerant-accelerating flow path. 
     In the compressor according to the second aspect, the flow rate of the refrigerant passing through the narrowed part of the refrigerant-accelerating flow path of the ejector mechanism is increased, and a negative pressure is generated due to an ejector effect in the oil suction flow path merging with the refrigerant-accelerating flow path, wherefore the lubricating oil is sucked in to the oil suction flow path from the oil return passage, and the sucked-in lubricating oil is supplied to the refrigerant-accelerating flow path. This makes it possible to increase the amount of lubricating oil returned to the interior of the compressor in the compressor according to the second aspect. 
     A compressor according to a third aspect of the present invention is the compressor according to the second aspect, wherein the oil suction flow path merges with the refrigerant-accelerating flow path in a substantially parallel manner. 
     In the compressor according to the third aspect, because the oil suction flow path merges with the refrigerant-accelerating flow path in a substantially parallel manner, the flow of lubricating oil in the oil suction flow path more readily merges into the refrigerant-accelerating flow path. For this reason, the lubricating oil sucked in to the oil suction flow path from the oil return passage is supplied more efficiently to the refrigerant-accelerating flow path. This makes it possible to further increase the amount of the lubricating oil returned to the interior of the compressor in the compressor according to the third aspect. 
     A compressor according to a fourth aspect of the present invention is the compressor according to the second aspect or the third aspect, wherein the refrigerant-accelerating flow path is formed from a first flow-path-forming member and a second flow-path-forming member. The first flow-path-forming member, together with the casing, forms a flow path for the high-pressure refrigerant. The second flow-path-forming member, together with the first flow-path-forming member, forms the narrowed part. Further, the oil suction flow path is formed from the casing and the second flow-path-forming member. 
     In the compressor according to the fourth aspect, the second flow-path-forming member is installed in the interior of a space (hereinbelow called a first space) surrounded by the first flow-path-forming member and the casing, thus forming the refrigerant-accelerating flow path and the oil suction flow path having the narrowed part. The first flow-path-forming member functions as a so-called gas guide member, and the refrigerant compressed by the compression mechanism is able to pass through the first space. The second flow-path-forming member functions as a so-called constricted-flow plate, and is installed such that a part of a flow path for the refrigerant in the first space is gradually narrowed. More specifically, the second flow-path-forming member, together with the first flow-path-forming member, forms a part of the refrigerant-accelerating flow path having the narrowed part. Further, a space (hereinbelow called a second space) is formed between the second flow-path-forming member and the casing. This second space communicates with the first space at a point where the refrigerant has passed through the narrowed part, and is also the oil suction flow path communicating with the oil return passage. This makes it possible to use the first flow-path-forming member and the second flow-path-forming member to efficiently construct the ejector mechanism in the compressor according to the fourth aspect; and, therefore, to achieve a cost reduction based on a reduced number of components. 
     A compressor according to a fifth aspect of the present invention is the compressor according to the second aspect or the third aspect, further provided with a main frame for supporting the compression mechanism. The main frame has a through-hole. The through-hole communicates with the high-pressure space, and is a space through which the high-pressure refrigerant discharged from the compression mechanism flows. The refrigerant-accelerating flow path includes the through-hole having the narrowed part as well as a space formed from the casing and the main frame. The oil suction flow path includes a space formed from the casing and the main frame. 
     In the compressor according to the fifth aspect, the narrowed part is formed in the through-hole of the main frame. It is possible to mechanically process the main frame and thereby to provide a narrowed part having a high degree of shape accuracy. This makes it possible to curb any variance in the suction force imparted by the ejector mechanism in the compressor according to the fifth aspect. 
     A compressor according to a sixth aspect of the present invention is provided with a casing, a compression mechanism, a main frame, and an ejector mechanism. The casing stores lubricating oil in a bottom part. The compression mechanism is accommodated in the interior of the casing. The compression mechanism compresses refrigerant and discharges high-pressure refrigerant. The main frame supports the compression mechanism. The ejector mechanism is accommodated in the interior of the casing. The casing has, in the interior thereof, a high-pressure space and an oil separation space. The high-pressure space is a space into which the high-pressure refrigerant discharged from the compression mechanism flows. The oil separation space is a different space than the high-pressure space, and is a space where lubricating oil is separated out from the high-pressure refrigerant. The main frame has a through-hole and an oil release hole. The through-hole communicates with the high-pressure space, and is a space through which the high-pressure refrigerant discharged from the compression mechanism flows. The oil release hole communicates with the high-pressure space, and is a space where the lubricating oil separated out in the oil separation space flows. The ejector mechanism has a refrigerant-accelerating flow path, where the high-pressure refrigerant flows via a narrowed part whereby the flow rate of the high-pressure refrigerant is increased, and an oil suction flow path, which merges with the refrigerant-accelerating flow path. The refrigerant-accelerating flow path includes a through-hole having a narrowed part as well as a space formed from the casing and the main frame. The oil suction flow path includes an oil release hole. 
     In the compressor according to the sixth aspect, the lubricating oil separated out in the oil separation space inside the casing will not be stored in the bottom part of the oil separation space, but rather will be rapidly released into the high-pressure space by the ejector mechanism. This makes it possible to curb any decline in the efficiency at which the lubricating oil is separated out in the compressor according to the sixth aspect. 
     A refrigeration device according to a seventh aspect of the present invention is provided with the compressor according to any of the first through sixth aspects, a condenser, an expansion mechanism, and an evaporator. 
     In the compressor according to the seventh aspect, a refrigeration device can be provided with the compressor according to any of the first through sixth aspects. This makes it possible to suppress any decline in the coefficient of performance and the refrigeration capacity of the compressor in the refrigeration device according to the seventh aspect. 
     Advantageous Effects of Invention 
     The compressor according to the first aspect makes it possible to suppress any decline in volumetric efficiency; and possible to achieve a reduction in cost. 
     The compressor according to the second aspect makes it possible to increase the amount of the lubricating oil returned to the interior of the compressor. 
     The compressor according to the third aspect makes it possible to further increase the amount of the lubricating oil returned to the interior of the compressor. 
     The compressor according to the fourth aspect makes it possible to achieve a reduction in cost. 
     The compressor according to the fifth aspect makes it possible to curb any variance in the suction force imparted by the ejector mechanism. 
     The compressor according to the sixth aspect makes it possible to curb any decline in the efficiency at which the lubricating oil is separated out. 
     The refrigeration device according to the seventh aspect makes it possible to suppress any decline in the coefficient of performance and the refrigeration capacity of the compressor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal cross-sectional view of a scroll compressor according to a first embodiment of the present invention; 
         FIG. 2  is a schematic view of a refrigerant circuit to which the scroll compressor according to the first embodiment of the present invention is provided; 
         FIG. 3  is a detailed longitudinal cross-sectional view of the vicinity of an ejector mechanism of the scroll compressor according to the first embodiment of the present invention; 
         FIG. 4  is a perspective view of a gas guide constituting the ejector mechanism according to the first embodiment of the present invention; 
         FIG. 5  is a perspective view of a constricted-flow plate for constituting the ejector mechanism according to the first embodiment of the present invention; 
         FIG. 6  is a perspective view of the gas guide in combination with the constricted-flow plate according to the first embodiment of the present invention; 
         FIG. 7  is a longitudinal cross-sectional view of a scroll compressor according to a second embodiment of the present invention; 
         FIG. 8  is a detailed longitudinal cross-sectional view of the vicinity of an ejector mechanism of the scroll compressor according to the second embodiment of the present invention; 
         FIG. 9  is an external view of a main frame according to the second embodiment of the present invention; 
         FIG. 10  is a cross-sectional view of the main frame according to the second embodiment of the present invention; 
         FIG. 11  is a longitudinal cross-sectional view of a scroll compressor according to a third embodiment of the present invention; 
         FIG. 12  is a detailed longitudinal cross-sectional view of the vicinity of an ejector mechanism of the scroll compressor according to the third embodiment of the present invention; and 
         FIG. 13  is a top view of a fixed scroll component of the scroll compressor according to the third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A description of the compressor according to the first embodiment of the present invention shall now be provided, with reference to  FIGS. 1 to 6 . The compressor in the present embodiment is a scroll compressor having two scrolling components in meshed engagement with each other, at least one of which engages in an orbital motion but not in a revolving motion, whereby refrigerant is compressed. 
     &lt;Configuration&gt; 
       FIG. 1  illustrates a longitudinal cross-sectional view of a scroll compressor  1  according to the present embodiment.  FIG. 2  illustrates a schematic view of a refrigerant circuit to which the scroll compressor  1  according to the present embodiment as well as an oil separator  2 , a condenser  3 , an expansion mechanism  4 , and an evaporator  5  are provided. The refrigerant circuit moves and operates to perform a refrigeration cycle for circulating refrigerant. 
     The scroll compressor  1  according to the present embodiment, as illustrated in  FIG. 2 , is connected via a discharge tube  20  and an oil return passage  96  to the oil separator  2 , which is disposed on the exterior of the scroll compressor  1 . A more detailed description of the constituent components of the scroll compressor  1  as well as a more detailed description of the oil separator  2  shall be provided below. 
     (1) Casing 
     A casing  10  has a substantially cylindrical trunk casing part  11 , a bowl-shaped upper wall part  12  hermetically welded to an upper end part of the trunk casing part  11 , and a bowl-shaped bottom wall part  13  hermetically welded to a lower end part of the trunk casing part  11 . The casing  10  is molded from a rigid member which is less prone to experience deformation or damage in a case where the pressure and temperature change on the interior and/or exterior of the casing  10 . The casing  10  is installed such that an axial direction of the substantially cylindrical shape of the trunk casing part  11  runs along the vertical direction. The inside of the casing  10  accommodates: a compression mechanism  15  for compressing refrigerant; a drive motor  16  disposed below the compression mechanism  15 ; a drive shaft  17  disposed so as to extend in the up-down direction throughout the inside of the casing  10 ; and the like. An intake tube  19  (described below), the discharge tube  20 , and the oil return passage  96  are hermetically joined to the casing  10 . 
     (2) Compression Mechanism 
     The compression mechanism  15  comprises a fixed scroll component  24  and an orbiting scroll component  26 . 
     The fixed scroll component  24  has a first end plate  24   a , and a spiral-shaped involute-shaped) first lap  24   b  formed in an upright manner on the first end plate  24   a . A main suction hole (not shown) and an auxiliary suction hole (not shown) adjacent to the main suction hole are formed on the fixed scroll component  24 . The main suction hole creates communication between the intake tube  19  (described below) and a compression chamber  40  (described below), and the auxiliary suction hole creates communication between a low-pressure space S 2  (described below) and the compression chamber  40  (described below). A discharge hole  41  is formed on a center part of the first end plate  24   a , and an expanded recess  42  communicating with the discharge hole  41  is formed on an upper surface of the first end plate  24   a . The expanded recess  42  comprises a recess expanding in the horizontal direction and disposed in a concave manner on the upper surface of the first end plate  24   a . A lid body  44  is securely fastened by a bolt  44   a  to the upper surface of the fixed scroll component  24  so as to close off the expanded recess  42 . By covering the expanded recess  42 , the lid body  44  forms a muffler space  45  composed of an expansion chamber for muting the operating sound of the compression mechanism  15 . The fixed scroll component  24  and the lid body  44  are tightly joined interposed by a packing (not shown) and thereby tightly sealed. A first intercommunicating passage  46  communicating with the muffler space  45  and opening on a lower surface of the fixed scroll component  24  is formed on the fixed scroll component  24 . 
     The orbiting scroll component  26  comprises a second end plate  26   a  and a spiral-shaped (involute-shaped) second lap  26   b  formed in an upright manner on the second end plate  26   a . A second bearing part  26   c  is formed on a lower surface center part of the second end plate  26   a . An oil supply hole  63  is formed on the second end plate  26   a . The oil supply hole  63  communicates between an upper surface outer peripheral part of the second end plate  26   a  and a space on the inside of the second bearing part  26   c . The first lap  24   b  and the second lap  26   b  mesh together, whereby the fixed scroll component  24  and the orbiting scroll component  26  form the compression chamber  40  enclosed by the first end plate  24   a , the first lap  24   b , the second end plate  26   a , and the second lap  26   b.    
     (3) Main Frame 
     The main frame  23  is installed below the compression mechanism  15  and is hermetically joined to an inner wall of the casing  10  at an outer peripheral surface thereof. For this reason, the interior of the casing  10  is subdivided into a high-pressure space S 1  below the main frame  23 , and the low-pressure space S 2  above the main frame  23 . The main frame  23  has a main frame recess  31  disposed in a concave manner on an upper surface of the main frame  23 , and a first bearing part  32  extending downward from a lower surface of the main frame  23 . A first bearing hole  33  penetrating in the up-down direction is formed in the first bearing part  32 . The fixed scroll component  24  is bolted or otherwise securely situated on the main frame  23 , and the orbiting scroll component  26  is clamped together with the fixed scroll component  24  interposed by an Oldham coupling  39  (described below). A second intercommunicating passage  48  penetrating in the up-down direction is formed on an outer peripheral part of the main frame  23 . The second intercommunicating passage  48  communicates with the first intercommunicating passage  46  on the upper surface of the main frame  23 , and communicates with the high-pressure space S 1  via a discharge port  49  on the lower surface of the main frame  23 . 
     (4) Oldham Coupling 
     The Oldham coupling  39  is a ring-shaped member for preventing the orbiting scroll component  26  from engaging in revolving motion, and is fitted into an oblong-shaped Oldham groove  26   d  formed on the main frame  23 . 
     (5) Drive Motor 
     The drive motor  16  is a brushless DC motor installed below the main frame  23 . The drive motor  16  comprises a stator  51  fixed to the inner wall of the casing  10 , and a rotor  52  provided with a slight clearance and accommodated so as to be able to rotate on the inside of the stator  51 . 
     A copper wire is wound around teeth of the stator  51  and a coil end  53  is formed thereabove and therebelow. An outer peripheral surface of the stator  51  is provided with a core-cut part formed over a lower end surface from an upper end surface of the stator  51  so as to be notched at a plurality of points, placed at predetermined intervals in the circumferential direction. The core-cut part forms a motor cooling passage  55  extending in the up-down direction between the trunk casing part  11  and the stator  51 . 
     The rotor  52  is coupled to the orbiting scroll component  26  via a drive shaft  17  (described below) in a center of rotation thereof. 
     (6) Secondary Frame 
     A secondary frame  60  is disposed below the drive motor  16 . The secondary frame  60  is fixed to the trunk casing part  11  and has a third bearing part  60   a.    
     (7) Oil Separation Plate 
     An oil separation plate  73  is a plate-shaped member installed below the drive motor  16  within the casing  10 , and fixed to an upper surface side of the secondary frame  60 . The oil separation plate  73  separates the lubricating oil included in the descending compressed refrigerant. The lubricating oil separated out falls to an oil reservoir P at a bottom part of the casing  10 . 
     (8) Drive Shaft 
     The drive shaft  17  is coupled to the compression mechanism  15  and to the drive motor  16 , and is disposed so as to extend in the up-down direction throughout the inside of the casing  10 . A lower end part of the drive shaft  17  is positioned at the oil reservoir P. An oil supply path  61  penetrating in an axial direction is formed in the interior of the drive shaft  17 . The oil supply path  61  communicates with an oil chamber  83  formed of an upper end surface of the drive shaft  17  and a lower surface of the second end plate  26   a . The oil chamber  83  communicates with a sliding part of the fixed scroll component  24  and the orbiting scroll component  26  (hereinafter simply called the “sliding part of the compression mechanism  15 ”), via the oil supply hole  63  of the second end plate  26   a , and ultimately leads to the low-pressure space S 2 . As such, when the drive shaft  17  engages in an axial rotational motion, a centrifugal pump action and a high-low pressure difference cause the lubricating oil being stored in the oil reservoir P to flow upward through the oil supply path  61  and to be supplied to the oil chamber  83 . Thereafter, the lubricating oil passes by way of the oil supply hole  63  and lubricates the sliding part of the compression mechanism  15 . 
     The drive shaft  17  has on the interior thereof a first horizontal oil supply hole  61   a , a second horizontal oil supply hole  61   b , and a third horizontal oil supply hole  61   c , for supplying lubricating oil to the first bearing part  32 , the third bearing part  60   a , and the second bearing part  26   c , respectively. The lubricating oil ascending through the oil supply path  61  is supplied to the first horizontal oil supply hole  61   a , the second horizontal oil supply hole  61   b , and the third horizontal oil supply hole  61   c , and lubricates a sliding bearing part of the drive shaft  17 . 
     (9) Ejector Mechanism 
     An ejector mechanism  91  is positioned below the discharge port  49  opening on the lower surface of the main frame  23 . The ejector mechanism  91  comprises a gas guide  92  and a constricted-flow plate  93 .  FIG. 3  provides a more detailed illustration of the ejector mechanism  91  set forth in  FIG. 1 ,  FIGS. 4 and 5  illustrate perspective views of the gas guide  92  and the constricted-flow plate  93 , respectively, constituting the ejector mechanism  91 .  FIG. 6  illustrates a perspective view of the gas guide  92  in combination with the constricted-flow plate  93 . 
     The gas guide  92 , as is illustrated in  FIG. 4 , comprises a first flow path-forming part  92   a , two first side wall parts  92   b , and two outer wall parts  92   c , Each of the two first side wall parts  92   b  is provided extending from both end parts of the first flow path-forming part  92   a , and each of the two outer wall parts  92   c  is provided extending from both end parts of each of the first side wall parts  92   b . The outer wall parts  92   c  have a surface which matches the shape of the inner wall of the casing  10 , and the gas guide  92  can be tightly joined in a complete manner to the inner wall surface of the casing  10  at the outer wall parts  92   c . For this reason, in a case where the gas guide  92  has been tightly joined to the inner wall surface of the casing  10 , then the first flow path-forming part  92   a  and the first side wall parts  92   b , together with the inner wall of the casing  10 , form a space which opens at an upper end and a lower end. The upper end of the gas guide  92 , as is illustrated in  FIG. 3 , is in contact with the lower surface of the main frame  23 , and therefore the space formed between the gas guide  92  and the casing  10  serves as a flow path for refrigerant, the flow path communicating from the second intercommunicating passage  48  via the discharge port  49 . The shape of the gas guide  92  as illustrated in  FIG. 3  represents the shape of the longitudinal cross-section of the first flow path-forming part  92   a.    
     The constricted-flow plate  93 , as is illustrated in  FIG. 5 , comprises a second flow path-forming part  93   a  and two second side wall parts  93   b . The two second side wall parts  93   b  are provided each extending from both end parts of the second flow path-forming part  93   a , Each of the second side wall parts  93   b  can be tightly joined to each of the first side wall parts  92   b  of the gas guide  92 , whereby the constricted-flow plate  93  can be combined with the gas guide  92 , as illustrated in  FIG. 6 . The shape of the constricted-flow plate  93  illustrated in  FIG. 3  represents the shape of the longitudinal cross-section of the second flow path-forming part  93   a . Specifically, the second flow path-forming part  93   a  is positioned between the casing  10  and the first flow path-forming part  92   a  of the gas guide  92 . 
     As is illustrated in  FIG. 3 , the gap between the first flow path-forming part  92   a  of the gas guide  92  and the second flow path-forming part  93   a  of the constricted-flow plate  93  gradually narrows as the gap advances downward from above. Herein, a narrowed part  94  is formed where the gap between the first flow path-forming part  92   a  and the second flow path-forming part  93   a  reaches a minimum. The refrigerant having flowed in from the second flow path-forming part  48  increases in flow rate upon passing through the narrowed part  94 , and therefore a space formed by the gas guide  92 , the constricted-flow plate  93 , and the casing  10  forms a refrigerant-accelerating flow path  95   a.    
     The space between the constricted-flow plate  93  and the casing  10  forms a part of an oil suction flow path  95   b  communicating with the oil return passage  96 . The oil suction flow path  95   b  merges with the refrigerant-accelerating flow path  95   a  at an intercommunicating space  48   b . An upper end part of the constricted-flow plate  93  is in contact with the casing  10 , and therefore the refrigerant flowing through the refrigerant-accelerating flow path  95   a  merges with the oil suction flow path  95   b  at a point where the refrigerant has passed through the narrowed part  94 . 
     (10) Oil Separator 
     The oil separator  2  has a function for separating the lubricating oil from the refrigerant and returning the separated lubricating oil to the high-pressure space S 1  within the casing  10  via the oil return passage  96 , so as to prevent the compressed refrigerant discharged from the discharge tube  20  of the scroll compressor  1  from flowing into the exterior refrigerant circuit in a state where the compressed refrigerant includes lubricating oil. 
     The oil separator  2 , as is illustrated in  2 , has a tank  2   a  internally provided with a mechanism for separating out the lubricating oil from the refrigerant; an inlet tube  2   b  for introducing the refrigerant containing the lubricating oil, into the interior of the tank  2   a  from the discharge tube  20  of the scroll compressor  1 ; an outlet tube  2   c  for supplying, from the tank  2   a  to the exterior refrigerant circuit, the refrigerant from which the lubricating oil has been separated out; and the oil return passage  96 , serving as a flow path for returning, to the high-pressure space S 1  within the casing  10 , the lubricating oil having been separated out from the refrigerant. The oil return passage  96  is joined to a bottom part of the tank  2   a.    
     (11) Intake Tube 
     The intake tube  19  is a member for guiding the refrigerant to the compression mechanism  15 , and is hermetically fitted into the upper wall part  12  of the casing  10 . 
     (12) Discharge Tube 
     The discharge tube  20  is a member for discharging the refrigerant from the casing  10 , and is hermetically fitted to a position in the high-pressure space S 1  in the trunk casing part  11  of the casing  10 . 
     (13) Oil Return Passage 
     The oil return passage  96  is a tube for returning, to the high-pressure space S 1  in the trunk casing part  11  of the casing  10 , the lubricating oil separated out by the oil separator  2  from the refrigerant compressed by the compression mechanism  15 . As is illustrated in  FIG. 3 , the oil return passage  96  is joined to the casing  10  at a position above the lower end of the constricted-flow plate  93 . 
     &lt;Operation&gt; 
     A description of the motion and operation of the scroll compressor  1  of the present embodiment shall now be provided. The description shall first relate to the flow of the refrigerant; thereafter, the process by which the lubricating oil is returned to the high-pressure space S 1  of the scroll compressor  1  from the oil separator  2  by way of the oil return passage  96  shall be described. 
     The description shall first relate to the flow of the refrigerant. Firstly, when the drive motor  16  is started up, the drive shaft  17  begins to engage in an axial rotational motion in association with the rotation of the rotor  52 . The axial rotational force of the drive shaft  17  is transmitted to the orbiting scroll component  26  via the second bearing part  26   c . The orbiting scroll component  26  is prohibited from engaging in revolving motion by the Oldham coupling  39 , and therefore engages in orbital motion, but not revolving motion, about a center of axial rotation of the drive shaft  17 . The refrigerant is supplied to the compression chamber  40  of the compression mechanism  15  from the intake tube  19  by way of the main suction hole, or from the low-pressure space S 2  by way of the auxiliary suction hole. The orbiting motion of the orbiting scroll component  26  causes the compression chamber  40  to move from the outer peripheral part of the fixed scroll component  24  toward the center part, while also causing the volume to gradually be reduced. As a result thereof, the refrigerant inside the compression chamber  40  is compressed and discharged from the discharge hole  41  to the muffler space  45 . The compressed refrigerant flows from the discharge port  49  into the high-pressure space S 1  by way of the first intercommunicating passage  46  and the second intercommunicating passage  48 , and passes through the ejector mechanism  91  to ultimately be discharged from the discharge tube  20 . The high-pressure refrigerant discharged from the scroll compressor  1  is supplied to the exterior refrigerant circuit after the lubricating oil has been separated out therefrom in the oil separator  2 , and is introduced into the intake tube  19  of the scroll compressor  1  by way of the condenser  3 , the expansion mechanism  4 , and the evaporator  5 . 
     During this compression operation of the refrigeration cycle, the lubricating oil stored in the oil reservoir P ascends through the oil supply path  61  of the drive shaft  17 , due to the centrifugal pump action and the high-low pressure difference, and is supplied to the sliding part of the compression mechanism  15  by way of the oil chamber  83  and the oil supply hole  63 . Because the sliding part is in contact with the compression chamber  40 , the lubricating oil supplied to the sliding part of the compression mechanism  15  is supplied to the compression chamber  40 . As a result thereof, the lubricating oil supplied to the compression chamber  40  is compressed together with the refrigerant. The lubricating oil, having lubricated the sliding part in the first bearing part  32  and the second bearing part  26 , leaks out to the high-pressure space S 1  from the lower end of the first bearing part  32 , and is supplied to the high-pressure space S 1  via an oil passage (not shown) which is formed in the main frame  23  and communicates with the main frame recess  31  and the high-pressure space S 1 . As such, the high-pressure refrigerant discharged from the scroll compressor  1  contains lubricating oil. 
     The high-pressure refrigerant containing the lubricating oil discharged from the scroll compressor  1  is taken into the interior of the tank  2   a  from the inlet tube  2   b  of the oil separator  2 , and the lubricating oil is separated out. Centrifugation is an example of a scheme for separating out the lubricating oil from the refrigerant. With centrifugation, an orbiting plate is disposed in the interior of the tank  2   a , and the refrigerant is made to perform an orbiting motion; the centrifugal force causes droplets of the lubricating oil included in the refrigerant to be separated out. The lubricating oil separated out from the refrigerant is stored in the bottom part of the tank  2   a , and the refrigerant from which the lubricating oil has been separated out is supplied from the outlet tube  2   c  to the exterior refrigerant circuit. The lubricating oil stored in the bottom part of the tank  2   a  is returned to the high-pressure space S 1  in the interior of the scroll compressor  1 , via the oil return passage  96 . A description of the process therefor shall now be provided. 
     The refrigerant compressed by the compression mechanism  15  passes through the ejector mechanism  91  and is ultimately discharged from the discharge tube  20 . The refrigerant, when passing through the ejector mechanism  91 , flows through the refrigerant-accelerating flow path  95   a . At such a time, because the flow path of the refrigerant is tightened in the narrowed part  94 , the flow rate of the refrigerant is increased. Because the refrigerant in the refrigerant-accelerating flow path  95   a  merges with the oil suction flow path  95   b  at a point where the refrigerant has passed through the narrowed part  94 , a negative pressure is generated in the oil suction flow path  95   b  due to an ejector effect. The lubricating oil inside the oil return passage  96 , which communicates with the oil suction flow path  95   b , is thereby sucked into the oil suction flow path  95   b . The lubricating oil sucked into the oil suction flow path  95   b  merges into the flow of refrigerant in the refrigerant-accelerating flow path  95   a , falls through the high-pressure space S 1 , and is supplied to the oil reservoir P in the bottom part of the casing  10 . 
     &lt;Features&gt; 
     In the scroll compressor  1  according to the present embodiment, the ejector effect generated when the refrigerant compressed by the compression mechanism  15  passes through the ejector mechanism  91  disposed in the high-pressure space S 1  inside the casing  10  causes the lubricating oil separated out by the oil separator  2  to be sucked into the high-pressure space S 1  from the oil return passage  96 . This makes it possible to prevent the as-yet uncompressed refrigerant from being heated and expanded by the high-temperature lubricating oil, because, in the scroll compressor  1  according to the present embodiment, the high-temperature lubricating oil separated out by the oil separator is not returned to a space filled with the as-yet uncompressed refrigerant (for example, a suction tube for the refrigerant of the compressor). As such, the scroll compressor  1  according to the present embodiment makes it possible to suppress any decline in volumetric efficiency of the compressor. 
     Further, in the scroll compressor  1  according to the present embodiment, there is no longer a need for a capillary tubing or other pressure adjustment mechanism, which has been necessary in a conventional compressor in order to return only a suitable amount of lubricating oil to the low-pressure space filled with as-yet uncompressed refrigerant. As such, the scroll compressor  1  according to the present embodiment makes it possible to achieve a reduction in costs by reducing the number of components in the compressor. 
     Also, in the scroll compressor  1  according to the present embodiment, the ejector mechanism  91 , which has no moving parts, is used in order to realize a mechanism whereby lubricating oil is sucked into the high-pressure space S 1  from the oil return passage  96 . As such, the scroll compressor  1  according to the present embodiment has an oil return mechanism which is simple to set up and maintain. 
     Modification Examples 
     In the present embodiment, the scroll compressor  1  provided with the compression mechanism  15 , constituted of the fixed scroll component  24  and the orbiting scroll component  26 , is used as the compressor, but a compressor provided with a different compression mechanism may also be used. For example, a rotary-type compressor and/or a screw-type compressor may be used. 
     Further, in the present embodiment, the oil separator  2  is disposed on the exterior of the casing  10  of the scroll compressor  1 , but an oil separation mechanism equivalent to the oil separator  2  may also be disposed on the interior of the casing  10 . This makes it possible to render the refrigerant circuit more compact. 
     Second Embodiment 
     A description of a compressor according to a second embodiment of the present invention shall now be provided, with reference to  FIGS. 7 to 10 . A scroll compressor  101  according to the present embodiment has identical configurations, operations, and features in common with the scroll compressor  1  according to the first embodiment. Hereinbelow, the description shall focus on the points of disparity between the scroll compressor  101  according to the present embodiment and the scroll compressor  1  according to the first embodiment. 
     &lt;Configuration&gt; 
       FIG. 7  illustrates a longitudinal cross-sectional view of the scroll compressor  101  according to the present embodiment.  FIG. 8  illustrates an enlarged cross-sectional view of the vicinity of an ejector mechanism  191  used in the present embodiment.  FIGS. 9 and 10  illustrate an external view and a cross-sectional view, respectively of a main frame  123  used in the present embodiment. In  FIGS. 7 to 10 , constituent elements identical to those of the scroll compressor  1  according to the first embodiment have been assigned reference numerals identical to those in  FIG. 1 . 
     (1) Main Frame 
     In the present embodiment, as is illustrated in  FIG. 7 , the main frame  123  has a second intercommunicating passage  148 . Similarly with respect to the second intercommunicating passage  48  in the first embodiment, the second intercommunicating passage  148  communicates with the first intercommunicating passage  46  on an upper surface of the main frame  123 , and communicates with the high-pressure space S 1  via the discharge port  49  on a lower surface of the main frame  123 . As is illustrated in  FIG. 8 , the second intercommunicating passage  148  comprises a frame through-hole  148   a  penetrating through the main frame  123  in the vertical direction, and an intercommunicating space  148   b  positioned below the frame through-hole  148   a  and formed between an outer peripheral surface of the main frame  123  and the inner wall surface of the trunk casing part  11 . As is illustrated in  FIGS. 9 and 10 , the frame through-hole  148   a  has a plurality of interlinking through-holes  148   a   1 ,  148   a   2 , . . . formed along a circumferential direction of the main frame  123 . As is illustrated in  FIGS. 8 and 10 , a lower end part of each of the through-holes  148   a   1 ,  148   a   2 , . . . has a truncated cone shape oriented vertically downward. More specifically, the horizontal surface area of the lower end parts of each of the through-holes  148   a   1 ,  148   a   2 , . . . gradually becomes smaller proceeding downward from above in the vertical direction. 
     In the present embodiment, the main frame  123  has a tapered part  129 . As is illustrated in  FIG. 8 to 10 , the tapered part  129  is a surface which is formed in the intercommunicating space  148   b  and is tilted inward in the radial direction from the outside in the radial direction of the trunk casing part  11  as the surface proceeds downward from above in the vertical direction. 
     (2) Ejector Mechanism 
     A description of the constituent elements of the ejector mechanism  191  in the present embodiment shall now be provided. As is illustrated in  FIG. 8 , the tapered part  129  forms a part of an oil suction flow path  195   b  with the inner wall surface of the trunk casing part ill. The oil suction flow path  195   b  merges with a refrigerant-accelerating flow path  195   a  in the intercommunicating space  148   b . An oil return passage  196  communicates with the oil suction flow path  195   b . An upper end of the oil return passage  196  is positioned on an upper end of the tapered part  129 . The frame through-hole  148   a  and the intercommunicating space  148   b  constitute the refrigerant-accelerating flow path  195   a . A lower end of the frame through-hole  148   a  is a narrowed part  194  where a flow path cross-sectional area of the refrigerant-accelerating flow path  195   a  reaches a minimum. 
     &lt;Action&gt; 
     A description of a process in the present embodiment by which the lubricating oil separated out by the oil separator  2  is returned to the high-pressure space S 1  by the ejector mechanism  191  via the oil return passage  196  shall now be provided. The refrigerant compressed by the compression mechanism  15 , when flowing through the refrigerant-accelerating flow path  195   a , passes through the narrowed part  194 . At such a time, the flow path of the refrigerant is tightened, whereby the flow rate of the refrigerant is increased. A negative pressure is generated, due to the ejector effect, in the oil suction flow path  195   b  merging with the refrigerant-accelerating flow path  195   a . The lubricating oil within the oil return passage  196  is thereby sucked into the oil suction flow path  195   b . The lubricating oil sucked into the oil suction flow path  195   b  flows into the refrigerant-accelerating flow path  195   a , thereafter falls through the high-pressure space S 1 , and is supplied to the oil reservoir P of the bottom part of the casing  10 . 
     &lt;Features&gt; 
     In the scroll compressor  101  according to the present embodiment, the main frame  123  has the frame through-hole  148   a  and the narrowed part  194 . The high-pressure refrigerant compressed by the compression mechanism  15  flows into the frame through-hole  148   a . The frame through-hole  148   a  communicates with the high-pressure space S 1 . The refrigerant-accelerating flow path  195   a  comprises the frame through-hole  148   a  and the intercommunicating space  148   b  firmed from the trunk casing part  11  and the main frame  123 . The oil suction flow path  195   b  is formed from the tapered part  129  of the main frame  123  and the trunk casing part  11 . 
     In the present embodiment, it is possible to mechanically process the main frame  123  to form the frame through-hole  148   a  having the narrowed part  194 . This makes it possible to increase the shape accuracy of the narrowed part  194 . As such, in the present embodiment, it possible to curb any variance in the suction force imparted by the ejector mechanism  191 . 
     Further, in the scroll compressor  1  according to the first embodiment, a concern is presented in that the refrigerant yet to pass through the narrowed part  94  may leak out from a gap between the gas guide  92  and the main frame  23 . However, in the scroll compressor  101  according to the present embodiment, the refrigerant compressed by the compression mechanism  15 , when flowing through the refrigerant-accelerating flow path  195   a , will reliably pass through the narrowed part  194 ; therefore, no concern is presented that the refrigerant having not yet passed through the narrowed part  194  will leak out. 
     Also, in the scroll compressor  101  according to the present embodiment, there is no need to install the constricted-flow plate  93  used in the scroll compressor  1  according to the first embodiment. 
     (Modifications) 
     In the scroll compressor  101  according to the present embodiment, each of the through-holes  148   a   1 ,  148   a   2 , . . . constituting the frame through-hole  148   a  has, at the lower end part, a truncated cone shape oriented downward in the vertical direction, but it is possible for at least one through-hole from among the through-holes  148   a   1 ,  148   a   2 , . . . to have, at the lower end part, a truncated cone shape oriented downward in the vertical direction. In the present modification example as well, the frame through-hole  148   a  has the narrowed part  194 . 
     Third Embodiment 
     A description of a compressor according to a third embodiment of the present invention shall now be provided, with reference to  FIGS. 11 to 13 . A scroll compressor  201  according to the present embodiment has identical configurations, operations, and features in common with the scroll compressor  101  according to the second embodiment. Hereinbelow, the description shall focus on the points of disparity between the scroll compressor  201  according to the present embodiment and the scroll compressor  101  according to the second embodiment. 
     &lt;Configuration&gt; 
       FIG. 11  illustrates a longitudinal cross-sectional view of the scroll compressor  201  according to the present embodiment.  FIG. 12  illustrates an enlarged cross-sectional view of the vicinity of an ejector mechanism  291  used in the present embodiment.  FIG. 13  illustrates a top view of a fixed scroll component  224  used in the present embodiment. In  FIGS. 11 to 13 , constituent elements identical to those of the scroll compressor  101  according to the second embodiment have been assigned reference numerals identical to those in  FIG. 7 . 
     (1) Casing 
     In the present embodiment, a casing  210  has a trunk casing part  211  onto which an intake tube  219  is hermetically fitted, as well as an upper wall part  212  onto which a discharge tube  220  is hermetically fitted at an upper surface thereof. Refrigerant is guided to the interior of the casing  210  via the intake tube  219 , compressed by the compression mechanism  215 , and discharged to the exterior of the casing  210  via the discharge tube  220 . 
     (2) Compression Mechanism 
     In the present embodiment, a fixed scroll component  224  of a compression mechanism  215 , as is illustrated in  FIG. 11 , has at an outer peripheral part an upper refrigerant passage  297   a  penetrating through in the vertical direction; and, as is illustrated in  FIG. 12 , has at the outer peripheral part an upper oil release hole  296   a  penetrating through in the vertical direction. The upper refrigerant passage  297   a  and the upper oil release hole  296   a  communicate with an oil separation space S 3 . The oil separation space S 3  is a space on the interior of the casing  21  which is above the compression mechanism  215 . The oil separation space S 3  is a space to which refrigerant gas compressed by the compression mechanism  215  is discharged. 
     The fixed scroll component  224 , as is illustrated in  FIG. 11 , has an interior discharge tube  230 . One of the end parts of the interior discharge tube  230  is connected to an opening part on an upper side of the upper refrigerant passage  297   a , and the other end part is positioned in the oil separation space S 3 . The interior discharge tube  230 , as is illustrated in  FIGS. 11 and 13 , is an L-shaped tube which is elongated upward in the vertical direction from the opening part of the upper refrigerant passage  297   a , caused to curve above the oil separation space S 3 , and elongated in the horizontal direction along a direction tangent to the outer periphery of the casing  210 . 
     (3) Main Frame 
     In the present embodiment, a main frame  223 , as is illustrated in  FIG. 12 , has a second intercommunicating passage  248 . Similarly with respect to the second embodiment, the second intercommunicating passage  248  communicates with the first intercommunicating passage  46  of the compression mechanism  215  on an upper surface of the main frame  223 , and communicates with the high-pressure space S 1  via the discharge port  49  on a lower surface of the main frame  223 . The second intercommunicating passage  248  comprises a frame through-hole  248   a  penetrating through the main frame  223  in the vertical direction, and an intercommunicating space  248   b  between an outer peripheral surface of the main frame  223  and an inner wall surface of the trunk casing part  211 , the intercommunicating space  248   b  being positioned below the frame through-hole  248   a . The frame through-hole  248   a  has at a lower end part a narrowed part  294  where the cross-sectional area reaches a minimum. 
     The main frame  223 , as is illustrated in  FIG. 11 , has, at an outer peripheral part, a lower refrigerant passage  297   b  penetrating through in the vertical direction, and, as is illustrated in  FIG. 12 , has a lower oil release hole  296   b  penetrating through in the vertical direction. The lower refrigerant passage  297   b  communicates with an upper refrigerant passage  297   a , and the lower oil release hole  296   b  communicates with an upper oil release hole  296   a . The lower refrigerant passage  297   b  and the lower oil release hole  296   b  communicate with the high-pressure space S 1  which is below the main frame  223 . The lower oil release hole  296   b  is positioned in the vicinity of the frame through-hole  248   a.    
     (4) Ejector Mechanism 
     In the present embodiment, the ejector mechanism  291 , as is illustrated in  FIG. 12 , comprises a refrigerant-accelerating flow path  295   a , an oil suction flow path  295   b , and the narrowed part  294 . In the present embodiment, the refrigerant-accelerating flow path  295   a  comprises the frame through-hole  248   a  and an intercommunicating space  248   b . The frame through-hole  248   a  has the narrowed part  294 . A space on the interior of the upper oil release hole  296   a  and the lower oil release hole  296   b  forms a part of the oil suction flow path  295   b . The oil suction flow path  295   b  merges with the refrigerant-accelerating flow path  295   a  in the intercommunicating space  248   b.    
     &lt;Operation&gt; 
     In the present embodiment, as is illustrated in  FIG. 11 , compressed refrigerant discharged from the compression mechanism  215  into the high-pressure space S 1  passes through the lower refrigerant passage  297   b  of the main frame  223  and the upper refrigerant passage  297   a  of the fixed scroll component  224  prior to being discharged to the exterior of the casing  210 , and flows into the interior discharge tube  230 . Thereafter, the compressed refrigerant is discharged from the interior discharge tube  230  into the oil separation space S 3 . In a case where the scroll compressor  201  is viewed from above, the compressed refrigerant, as is illustrated in  FIG. 13 , is discharged at the outer peripheral part of the fixed scroll component  224 , along a direction tangent to the outer periphery of the casing  210 . The compressed refrigerant discharged spinningly flows in the oil separation space S 3  while running along the inner wall surface of the upper wall part  212  of the casing  210 . At such a time, the lubricating oil included in the compressed refrigerant is separated out by the centrifugal force created by the spinning flow, and is flung toward the inner wall surface of the upper wall part  212 . The lubricating oil, flung out and having stuck to the inner wall surface of the upper wall part  212 , falls through the inside of the oil separation space S 3 , and is released into the high-pressure space S 1  from the upper oil release hole  296   a  of the fixed scroll component  224 . The compressed refrigerant from which the lubricating oil has been separated out is discharged to the exterior of the casing  210  via the discharge tube  220 . 
     A description of a process in the present embodiment by which the lubricating oil separated out in the oil separation space S 3  is returned to the high-pressure space S 1  by the ejector mechanism  291  shall now be provided. The refrigerant compressed by the compression mechanism  215 , when flowing through the refrigerant-accelerating flow path  295   a , passes through the narrowed part  294 . At such a time, the flow path of the refrigerant is tightened, whereby the flow rate of the refrigerant is increased. A negative pressure is generated, due to the ejector effect, in the oil suction flow path  295   b  merging with the refrigerant-accelerating flow path  295   a . A suction action from the oil separation space S 3  to the oil suction flow path  295   b , i.e., to the lower oil release hole  296   b  is thereby generated. As such, the lubricating oil separated out from the compressed refrigerant in the oil separation space S 3  is sucked into the lower oil release hole  296   b  by way of the upper oil release hole  296   a , and ultimately arrives at the intercommunicating space  248   b . Thereafter, the lubricating oil falls through the high-pressure space S 1  and is supplied to the oil reservoir P in the bottom part of the casing  210 . 
     &lt;Features&gt; 
     In the present embodiment, the lubricating oil separated out in the oil separation space S 3  is not stored in the bottom part of the oil separation space S 3  but rather is rapidly released into the high-pressure space S 1  by the ejector mechanism  291 . As such, the scroll compressor  201  according to the present embodiment makes it possible to curb any decline in the efficiency at which the lubricating oil is separated out. 
     Also, in the present embodiment, the lubricating oil is separated out from the compressed refrigerant in the oil separation space S 3  inside the casing  210 , and accordingly there is no need to install on the exterior of the casing  210  the oil separator  2  used in the second embodiment. As such, the scroll compressor  201  according to the present embodiment makes it possible to reduce costs. 
     INDUSTRIAL APPLICABILITY 
     The compressor according to the present invention returns high-temperature lubricating oil separated out by the oil separator to the high-pressure space in the interior of the compressor, making it possible to suppress any decline in volumetric efficiency. As such, employing the compressor according to the present invention in a refrigeration cycle makes it possible to operate an air conditioner or other refrigeration device in an efficient manner. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  101 ,  201  Compressor (Scroll compressor) 
           2  Oil separator 
           3  Condenser 
           4  Expansion mechanism 
           5  Evaporator 
           10 ,  210  Casing 
           15 ,  215  Compression mechanism 
           91 ,  191 ,  291  Ejector mechanism 
           92  First flow-path-forming member (gas guide) 
           93  Second flow-path-forming member (Constricted-flow plate) 
           94 ,  194 ,  294  Narrowed part 
           95   a ,  195   a ,  295   a  Refrigerant-accelerating flow path 
           95   b ,  195   b ,  295   b  Oil suction flow path 
           96 ,  196  Oil return passage 
           123 ,  223  Main frame 
           148   a ,  248   a  Through-hole (frame through-hole) 
           296   b  Oil release hole (lower oil release hole) 
         S 1  High-pressure space 
         S 3  Oil separation space 
       
    
     CITATION LIST 
     Patent Literature 
     PATENT LITERATURE 1: Japanese Unexamined Publication No. 5-223074