Abstract:
A scroll compressor contains a suction chamber and a compression chamber formed between the orbiting scroll and stationary scroll; and the rear surface of the orbiting scroll includes a back pressure chamber to apply a pressing force for pressing the stationary scroll to the orbiting scroll by the pressure higher than the pressure in the suction chamber. The stationary scroll contains the communication paths  200, 201  to connect the suction chamber or the compression chamber and the back pressure chamber; and a back pressure control means for opening and closing the communication paths by way of the pressure differential along the communication paths. The inlet communication path  200  that extends from the back pressure control means to the back pressure chamber includes at least two or more path cross-sectional areas. The cross-sectional area of an inlet communication path  301  on the back pressure chamber side of this inlet communication path is formed larger than the cross-sectional area of an inlet communication path  302  on the back pressure control means side. Moreover, the opening surface area of the back pressure chamber side of the communication path  301  is configured so as to be constantly equal to or smaller than the cross-sectional area of the communication path  302  so that a section of the back pressure chamber side opening  300  of the communication path  301  is constantly blocked by the base plate of the orbiting scroll, and in this way a highly efficient and highly reliable scroll compressor is achieved.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a scroll compressor utilized in refrigerant compressors for air conditioning and freezers, or compressors for compressing gas such as air. 
       BACKGROUND ART 
       [0002]    A screw compressor of the related art is described for example in Japanese Unexamined Patent Application Publication No. 2005-163655 (Patent Literature 1). This technology of the related art includes: “a non-orbiting scroll member, an orbiting scroll member forming a suction chamber or a compression chamber by orbital motion engaging with the non-orbiting scroll member, a back pressure chamber to apply a pressing force against the non-orbiting scroll member to the scroll member, a back pressure chamber fluid inflow means to flow a fluid into the back pressure chamber to maintain the back pressure serving as the compression chamber pressure, and a back pressure chamber fluid outflow means to flow the inflow fluid into the suction chamber or back pressure chamber. The back pressure fluid outflow means includes in a series arrangement: a back pressure control valve to control the upstream and downstream pressure differential, and a throttle flow path, and an intermittent flow path intermittently connecting by way of the orbital motion of the orbiting scroll member along the back pressure chamber fluid outflow path connecting the back pressure chamber and suction chamber or compression chamber. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent literature 1: Japanese Unexamined Patent Application Publication No. 2005-163655 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    In the scroll compressor, a gas and oil compression effect acts on the orbital edge plate side surface of the back pressure chamber, along with the orbital motion of the orbiting scroll member. In the method disclosed in the patent literature 1, an orbital outer circumferential groove was formed to avoid gas and oil compression. This method alleviated pressure fluctuations on the orbital edge plate side surface of the back pressure chamber, however the pressure fluctuations were not completely eliminated and caused fluctuations in pressure in the back pressure valve inflow hole. Pressure on the orbital edge plate side surface reaches a maximum when the orbital edge plate is closest to the outer circumference; and the pressure reaches a minimum when the orbital edge plate is farthest away from the outer circumference. Orbital edge plate side surface pressure fluctuations acting directly on the back pressure valve plate, promote abnormal vibrations in the back pressure valve and increase the fluid volume flowing into the back pressure valve; so that the back pressure drops below the specified pressure, and therefore a correct orbital scroll pushup force cannot be achieved, causing problems such as drop in efficiency. In the method disclosed in patent literature 1, the orbital edge plate serves as an intermittent structure to block the back pressure valve inflow hole when the pressure on the orbital edge plate side surface is highest so that the pressure fluctuation width at the back pressure valve inflow hole dropped to a small level relative to the pressure fluctuation width at the orbital edge plate side surface. However, the back pressure valve inflow hole is fully open when the pressure on the orbital edge plate side surface is lowest, and the pressure on the orbital edge plate side surface acts directly on the back pressure valve plate causing the concern that problems from the above described drop in back pressure may occur under conditions where pressure fluctuations become large during high speed rotation. 
         [0005]    In scroll compressors containing a back pressure control means that opens and closes by way of a pressure differential an object of the present invention is to provide a highly efficient and highly reliable compressor capable of maintaining the back pressure at a proper stable level even under operating conditions where pressure fluctuations of the orbital edge plate side surface become large. 
       Solution to Problem 
       [0006]    In order to achieve the above described objects, the scroll compressor of the present invention includes a crankshaft to mutually engage a stationary scroll having a whirlpool shape on the base plate and an orbiting scroll, and drive the orbiting scroll; a suction chamber and a compression chamber formed between the orbiting scroll and stationary scroll by the orbital motion of the orbiting scroll accompanying the rotation of the crankshaft; a back pressure chamber included in the back surface of the orbital scroll to apply a pressing force on the stationary scroll to the orbiting scroll by a pressure that is higher than the pressure in the suction chamber; a communication path in the stationary scroll for connecting the suction chamber or the compression chamber and the back pressure chamber; and a back pressure control means for opening and closing the communication path by way of the pressure differential along the communication path; and in which an inlet communication path that extends from the back pressure control means of the communication path to the back pressure chamber includes at least two or more path cross-sectional areas, and the cross-sectional area of the inlet communication path on the back pressure chamber side is formed larger than the cross-sectional area of an inlet communication path located on the back pressure control means side, and configured so that the opening surface area of the back pressure chamber side of the inlet communication path on the back pressure chamber side is always equal to or smaller than the cross-sectional area of the inlet communication path on the back pressure control means side, by the base plate of the orbiting scroll always blocking part of the back pressure chamber side opening of the inlet communication path on the back pressure chamber side. 
         [0007]    Even in cases where using a structure to intermittently connect to a communication path by opening and closing the back pressure chamber side opening of the communication path by way of the base plate of the orbiting scroll, a structure can be configured where the opening surface area of the back pressure chamber side of the communication path is equal to or smaller than a cross-sectional area of the communication path of the back pressure control means side, even during the maximum opening. 
         [0008]    Moreover, a groove extending to the outer circumferential side may be formed in a section of the back pressure chamber side opening of the inlet communication path on the back pressure chamber side, in which the groove is blocked by the base plate of the orbiting scroll so that the edge of the groove is opened to the back pressure chamber side; and the opening surface area of the groove is always equal to or smaller than the cross-sectional area of the inlet communication path on the back pressure control means side. 
         [0009]    A groove or a hole connecting the back pressure chamber side opening of the back pressure chamber side inlet communication path with the back pressure chamber can be formed over the base plate of the orbiting scroll, so that the opening surface area of the groove or hole is equal to or smaller than the cross-sectional area of the inlet communication path on the back pressure control means side. 
       Advantageous Effects of Invention 
       [0010]    The scroll compressor of the present invention including a back pressure control means that opens and closes by differential pressure, is configured so that cross-sectional area of the communication path on the back pressure chamber side of the communication path connecting the suction chamber or the compression chamber and the back pressure chamber is larger than the cross-sectional area of the communication path of the back pressure control means, and also the opening surface area on the back pressure chamber side is always equal to or smaller than the cross-sectional area of the communication path on the back pressure control means side so that a pressure fluctuation transmittance suppression effect is obtained according to the enlargement or shrinkage of the path. Pressure fluctuations acting on the back pressure control means can therefore be suppressed even under operating conditions where pressure fluctuations on the orbital edge plate side surface have become large, and abnormal vibrations in the back pressure control means can be prevented so that the back pressure can be maintained at an appropriately stable level and a highly efficient and highly reliable scroll compressor can be achieved. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a vertical cross-sectional view showing the scroll compressor of the first embodiment of the present invention; 
           [0012]      FIG. 2  is an enlarged view of essential sections in the vicinity of the back pressure control means shown in  FIG. 1 ; 
           [0013]      FIG. 3  is a bottom view of the stationary scroll shown in  FIG. 1 ; 
           [0014]      FIG. 4  is a bottom view showing another example of the stationary scroll shown in  FIG. 1 ; 
           [0015]      FIG. 5  is an enlarged view of essential sections in the vicinity of the back pressure control means shown in  FIG. 1 : (a) is a drawing showing the state when the base plate of orbiting scroll is closest to the outer circumference; and (b) is a drawing showing the state when the base plate of orbiting scroll is farthest from the outer circumference; 
           [0016]      FIG. 6  is a drawing equivalent to  FIG. 5 , as an enlarged view of essential sections showing the scroll compressor of the second embodiment of the present invention; 
           [0017]      FIG. 7  is a drawing equivalent to  FIG. 5 , showing an enlarged view of essential sections of the scroll compressor of the third embodiment of the present invention; 
           [0018]      FIG. 8  is a bottom view of the stationary scroll in the third embodiment shown in  FIG. 7 ; 
           [0019]      FIG. 9  is a drawing equivalent to  FIG. 5 , showing an enlarged view of essential sections of the scroll compressor of the fourth embodiment of the present invention; 
           [0020]      FIG. 10  is a drawing equivalent to  FIG. 5 , showing an enlarged view of essential sections of the scroll compressor of the fifth embodiment of the present invention; 
           [0021]      FIG. 11  is a flat view of the orbiting scroll of the fifth embodiment shown in  FIG. 10 ; 
           [0022]      FIG. 12  is a drawing equivalent to  FIG. 5 , showing an enlarged view of essential sections of the scroll compressor of the sixth embodiment of the present invention; 
           [0023]      FIG. 13  is a drawing equivalent to  FIG. 5 , showing an enlarged view of essential sections of the scroll compressor of the seventh embodiment of the present invention; 
           [0024]      FIG. 14  is a flat view of the orbiting scroll of the seventh embodiment shown in  FIG. 13 ; and 
           [0025]      FIG. 15  is a drawing equivalent to  FIG. 5 , showing an enlarged view of essential sections of the scroll compressor of the eight embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]    The embodiments of the present invention are described next in detail while referring to the accompanying drawings. Sections in the drawings having identical reference numeral indicate identical or equivalent sections. 
       First Embodiment 
       [0027]    The scroll compressor of the first embodiment is shown in  FIG. 1 . The overall structure of the scroll compressor is first of all described. A scroll compressor  1  includes a drive section  3  and a compressor containing a stationary scroll  20  orbiting scroll  19  within a sealed container  21 . The drive section  3  is comprised of an electric motor  10  containing a stator  8  and a rotor  9 , a crankshaft  11 , a frame  12 , an auxiliary frame  13 , and an auxiliary shaft bearing housing  16  as basic structural elements. Here, the electric motor  10  is driven by electrical input from an inverter (not shown in the drawing) byway of the electrical terminal  17  to apply a rotating effect to the crankshaft  11 . The crankshaft  11  includes a main shaft  11   a  and an auxiliary shaft  11   b  and an eccentric pin  11   c . The shaft bearing  14  mounted in the frame  12 , and the shaft bearing  15  mounted in the auxiliary shaft bearing housing  16  form shaft bearings supporting the main shaft  11   a  and auxiliary shaft  11   b  of the crankshaft  11  for free rotation. The fluid  18  for lubricating the shaft bearings  14 ,  15  is accumulated within the sealed container  21 . The frame  12  and the auxiliary frame  13  joined to the auxiliary shaft housing  16  are clamped to the sealed container  21 . The rotational effect of the crankshaft  11  exerts a compressive action that reduces the volume of the compression chamber  2  mechanically formed by the mutual engagement of the stationary scroll  20  and orbiting scroll  19 . The operating fluid is suctioned from the suction pipe  6  into the compression chamber  2  is dispensed by way of the compression stroke from the dispensing port  4  to the dispensing space  5  within the sealed container  21 , and is further dispensed from the dispensing pipe  7  to outside the sealed container  21 . 
         [0028]    In order to maintain the sealing of the compression chamber  2 , the intermediate pressure (hereafter called back pressure) between the dispensing pressure and suction pressure acts on the back space (hereafter called back pressure chamber  102 ) of the orbiting scroll  19  to press the orbiting scroll  19  against the stationary scroll  20 . By utilizing the back pressure control means  106  installed in the stationary scroll  20  to generate and maintain a correct back pressure, energy loss caused by coolant leakage during compression operation can be reduced and satisfactory reliability for the push-sliding action of the orbiting scroll  19  can be ensured. 
         [0029]    The structure of the back pressure control means  106  is described while referring to  FIG. 2  through  FIG. 4 .  FIG. 2  is a drawing showing in detail the back pressure control means  106  shown in  FIG. 1 . The back pressure control means  106  is comprised of a seal member  107 , a spring  108 , a valve body  109 , and a sheet  110 , and is mounted between an inlet communication path  200  and an outlet communication path  201 . The inlet side of the inlet communication path  200  is an opening to the sliding surface with a base plate  100  of the orbiting scroll of the stationary scroll  20 , and fulfills the task of connecting the back pressure chamber  102  to the back pressure control means  106 . The inlet communication path  200  is configured from an inlet communication path  301  on the back pressure chamber  102  side, and an inlet communication path  302  on the back pressure control means  106  side; and the cross-sectional area S 1  of the path  301  is formed larger than the cross-sectional area S 2  of the path  302 . 
         [0030]    The outlet side of the outlet communication path  201  is an opening to a suction groove  202  of the stationary scroll, and fulfills the task of connecting the back pressure control means  106  with the suction groove  202 . 
         [0031]      FIG. 3  is a bottom view of the stationary scroll  20  shown in  FIG. 1  and  FIG. 2 . The suction groove  202  is connected to a suction space  203  as shown in  FIG. 3 . The outlet communication path  201  may be formed as an opening to an intermediate pressure groove  204  connecting to the compression chamber  2  as shown in  FIG. 4 . In the following description, a structure opening to the suction groove  202  ( FIG. 3 ) is utilized as an example. 
         [0032]    In the state shown in  FIG. 2  with the compressor stopped, the valve body  109  is pressed against the sheet  110  by the spring weight of the spring  108 . In a state where the compressor is operating, the pressure in the suction groove  202  connecting to the suction space  203  drops, and by way of the outlet communication path  201  the upper section pressure P 3  of the valve body  109  drops to a pressure lower than the pressure P 2  inside the path  302  which is the bottom section of the valve body  109 . When the weight acting on the valve body  109  becomes larger than the spring weight of the spring  108  due to the pressure differential between the pressure P 2  and pressure P 3 , the valve body  109  opens, to allow gas and oil to flow from the back pressure chamber  102  into the suction groove  202 , exerting back pressure control to maintain the pressure Pb inside the back pressure chamber  102  at a specified pressure. 
         [0033]      FIG. 5  is a drawing showing the positional relationship between the inlet communication path  200  and the base plate  100  of the orbiting scroll of the first embodiment. A base plate  100  of the orbiting scroll has an orbital motion so the outer circumferential end of the base plate moves below the inlet communication path  200 . An opening  300  is formed in a state where the base plate  100  of the orbiting scroll blocks a section of the inlet of the inlet communication path  301  on the back pressure chamber side. The surface area S 0  of the opening  300  is configured to always be an identical to or smaller than the cross-sectional area S 2  of the inlet communication path  302  on the back pressure control means  106  side and always connects the path  301  with outer circumferential space  101 . 
         [0034]    The outer circumferential space  101  of the base plate of the orbiting scroll is connected to the back pressure chamber  102  of the base plate  100  of the orbiting scroll by way of the path  303 . However fluctuations in the pressure differential applied by the gas compression effect that accompanies movement of the base plate  100  of the orbiting scroll relative to the back pressure Pb occur in the outer circumferential pressure P 0 . The pressure as shown in (a) in the figure reaches a maximum at the position where the base plate  100  of the orbiting scroll is closest to the outer circumference; and the pressure as shown in (b) in the figure reaches a minimum at the position where the base plate  100  of the orbiting scroll approaches the inner side (position farthest from outer circumference). When the fluctuation in outer circumferential pressure P 0  is directly conveyed to the path  302  which is the bottom section of the valve body  109 , the valve body  109  causes an abnormal vibration due to effects from the pressure fluctuation, so that the flow rate of gas and oil passing through the back pressure control means  106  increases, leading to a drop in the back pressure Pb. In the present embodiment, the path  301  forms an enlarged space between the constricted opening  300  and the constricted path  302  as described above, so that transmitta0 is suppressed, providing the effect of minimizing fluctuations in the pressure P 2 , and preventing problems from a drop in the back pressure Pb. 
         [0035]    The pressing force from the orbiting scroll  19  on the stationary scroll  20  can in this way be correctly maintained and the supply of oil to the compression chamber can also be maintained at a correct level, so that coolant leakage losses during the compression operation can be prevented and the energy efficiency improved. Providing a correct back pressure also improves the reliability of the sliding action of the orbiting scroll  19 . A scroll compressor capable of high energy efficiency and high reliability can therefore be provided. 
       Second Embodiment 
       [0036]    The second embodiment of the scroll compressor of the present invention is described while referring to  FIG. 6 .  FIG. 6  is a drawing equivalent to  FIG. 5 . 
         [0037]    This embodiment is configured so that the surface area S 0  of the opening  300  is equivalent or smaller than the cross-sectional area S 2  of the inlet communication path  302  on the back pressure control means side, the same as in the first embodiment. The second embodiment differs from the first embodiment in the point that there is a time in which the inlet communication path  301  on the back pressure chamber side is temporarily fully closed by the base plate  100  of the orbiting scroll; and in the point that the path  301  intermittently connects to the outer circumferential space  101 . By configuring the present embodiment so that the path  301  does not connect to the outer circumferential space  101  when the outer circumferential pressure P 0  is high, a pressure P 2  can be maintained with greater stability within the path  302  and problems from a drop in the back pressure Pb can be prevented. 
       Third Embodiment 
       [0038]    The third embodiment of the scroll compressor of the present invention is described while referring to  FIG. 7  and  FIG. 8 .  FIG. 7  is a drawing equivalent to  FIG. 5 .  FIG. 8  is a bottom view of the stationary scroll of the third embodiment and is a drawing for describing the shape of the groove  104  formed in the stationary scroll. 
         [0039]    In the present embodiment, a groove  104  extending from the inlet communication path  301  on the back pressure chamber side towards the outer circumference is formed over the base plate surface of the stationary scroll. A base plate  100  of the stationary scroll is positioned below this groove  104 , and the outer circumferential edge of the groove  104  is configured to be on the outer side from the outer circumferential edge of the base plate  100  of the orbiting scroll. A structure was in this way configured that always connects the inlet communication path  301  on the back pressure chamber side with the outer circumferential space  101 . The cross-sectional area S 0  of the groove  104  is made identical to or smaller than the cross-sectional area S 2  of the inlet communication path  302  on the back pressure control means side. The path  301  forms an enlarged space between the constricted groove  104  and the constricted path  302  so that the transmittance of fluctuations in the outer circumferential pressure P 0  within the path  302  is suppressed, and an effect that reduces fluctuations in pressure P 2  is obtained, and the problem of a drop in back pressure Pb is prevented. 
         [0040]    Configuring a structure for the present invention according to the indicated dimensions is difficult in the above described first or second embodiments due to the size of the orbital radius. The third embodiment however can be easily configured by adjusting the length of the groove  104  and is not susceptible to effects from the orbital radius. 
       Fourth Embodiment 
       [0041]    The fourth embodiment of the scroll compressor of the present invention is described while referring to  FIG. 9 .  FIG. 9  is a drawing equivalent to  FIG. 5 . 
         [0042]    The point where the fourth embodiment differs from the third embodiment is that the outer circumferential edge of the groove  104  is configured to temporarily function as the inner side from the outer circumferential edge of the base plate  100  of the orbiting scroll. Utilizing this type of configuration allows a structure that is capable of intermittently connecting the inlet communication path  301  on the back pressure chamber side and the outer circumferential space  101 . Utilizing this embodiment, allows configuring a structure where the path  301  and outer circumferential space  101  are not connected when the outer circumferential pressure P 0  is high, and maintains the pressure P 2  with greater stability within the inlet communication path  302  on the back pressure control means side. 
         [0043]    Configuring a structure for the present invention according to the indicated dimensions is difficult in the above described first or second embodiments due to the size of the orbital radius. The fourth embodiment however can be easily configured by adjusting the length of the groove  104  and is not susceptible to effects from the orbital radius. 
       Fifth Embodiment 
       [0044]    The fifth embodiment of the scroll compressor of the present invention is described while referring to  FIG. 10  and  FIG. 11 .  FIG. 10  is a drawing equivalent to  FIG. 5 .  FIG. 11  is a flat view of the orbiting scroll of the fifth embodiment and is a drawing for describing the shape of the groove  103  formed in the orbiting scroll. 
         [0045]    In the present embodiment, a groove  103  extending to the outer circumferential edge is formed over the base plate surface of the orbiting scroll, and configured so that an inlet communication path  301  on the back pressure chamber side of the stationary scroll is positioned permanently on that applicable groove  103 , and so that the path  301  and outer circumferential space  101  are constantly connected to each other. The cross-sectional area S 0  of the groove  103  is configured to be identical to or smaller than the cross-sectional area S 2  of the inlet communication path  302  on the back pressure control means side. The path  301  forms an enlarged space between the constricted groove  103  and the constricted path  302  so that the transmittance of fluctuations in the outer circumferential pressure P 0  within the path  302  is suppressed, and an effect that reduces fluctuations in pressure P 2  is obtained, and the problem of a drop in back pressure Pb is prevented. 
         [0046]    Configuring a structure for the present invention according to the indicated dimensions is difficult in the above described first or second embodiments due to the size of the orbital radius. The fifth embodiment however can be easily configured by adjusting the length of the groove  103  and is not susceptible to effects from the orbital radius. 
       Sixth Embodiment 
       [0047]    The sixth embodiment of the scroll compressor of the present invention is described referring to  FIG. 12 .  FIG. 12  is a drawing equivalent to  FIG. 5 . 
         [0048]    The point where the sixth embodiment differs from the above described fifth embodiment is that an inlet communication path  301  on the back pressure chamber side of the stationary scroll is temporarily positioned on the groove  103 , in a structure where the path  301  and the outer circumferential space  101  are intermittently connected. Utilizing this embodiment, allows configuring a structure where the path  301  and outer circumferential space  101  are not connected when the outer circumferential pressure P 0  is high, and maintains the pressure P 2  with greater stability within the inlet communication path  302  on the back pressure control means side. 
         [0049]    Configuring a structure for the present invention according to the indicated dimensions is difficult in the above described first or second embodiment due to the size of the orbital radius. The sixth embodiment however can be easily configured by adjusting the length of the groove  103  and is not susceptible to effects from the orbital radius. 
       Seventh Embodiment 
       [0050]    The seventh embodiment of the scroll compressor of the present invention is described next while referring to  FIG. 13  and  FIG. 14 .  FIG. 13  is a drawing equivalent to  FIG. 5 .  FIG. 14  is a flat view of the orbiting scroll of the seventh embodiment, and is a drawing for describing the hole  105  formed in the orbiting scroll. 
         [0051]    In the present embodiment, a hole  105  is formed in the base plate surface of the orbiting scroll; and configured so that an inlet communication path  301  on the back pressure chamber side of the stationary scroll is positioned permanently on the hole  105 , and so that the path  301  and outer circumferential space  101  are constantly connected to each other. The cross-sectional area S 0  of the hole  105  is configured to be identical to or smaller than the cross-sectional area S 2  of the inlet communication path  302  on the back pressure control means side. The path  301  forms an enlarged space between the constricted hole  105  and the constricted path  302  so that the transmittance of fluctuations in the outer circumferential pressure P 0  within the path  302  is suppressed, and an effect that reduces fluctuations in pressure P 2  is obtained, and the problem of a drop in back pressure Pb is prevented. 
       Eighth Embodiment 
       [0052]    The eighth embodiment of the scroll compressor of the present invention is described next while referring to  FIG. 15 .  FIG. 15  is a drawing equivalent to  FIG. 5 . 
         [0053]    The point where the present embodiment differs from the above seventh embodiment is that an inlet communication path  301  on the back pressure chamber side of the stationary scroll is positioned temporarily on the hole  105 , and so that the path  301  and outer circumferential space  101  are intermittently connected to each other. By utilizing a structure where the path  301  and outer circumferential space  101  are not connected when the outer circumferential pressure P 0  is high, the pressure P 2  within the inlet communication path  302  on the back pressure control means side can be maintained with greater stability. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1 : scroll compressor,  2 : compression chamber,  3 : drive section,  4 : dispensing port,  5 : dispensing space, 
           6 : suction pipe,  7 : dispensing pipe,  8 : stator,  9 : rotor,  10 : electric motor, 
           11 : crankshaft,  12 : frame,  13 : auxiliary frame, 
           14 ,  15 : shaft bearing,  16 : auxiliary shaft bearing housing, 
           17 : electrical terminal,  18 : fluid,  19 : orbiting scroll,  20 : stationary scroll, 
           21 : sealed container, 
           100 : base plate of the orbiting scroll,  101 : outer circumferential space of the base plate of the orbiting scroll, 
           102 : back pressure chamber, 
           103 ,  104 : groove,  105 : hole,  106 : back pressure control means 
           107 : seal member,  108 : spring,  109 : valve body,  110 : sheet 
           200 : inlet communication path,  201 : outlet communication path, 
           202 : suction groove,  203 : suction space,  204 : intermediate pressure groove, 
           300 : opening, 
           301 : inlet communication path on the back pressure chamber side,  302 : inlet communication path on the back pressure control means side, 
           303 : communication path between the back pressure chamber and the outer circumferential space of base plate of orbiting scroll, 
         S 0 : cross-sectional area of opening, S 1 : cross-sectional area of the inlet communication path on the back pressure chamber side 
         S 2 : cross-sectional area of the inlet communication path on the back pressure control means side, 
         P 0 : pressure in the cross-sectional area of the opening, P 1 : pressure in the inlet communication path on the back pressure chamber side, 
         P 2 : pressure in the inlet communication path on the back pressure control means side, 
         P 3 : pressure in the outlet communication path, Pb: pressure inside the back pressure chamber