Abstract:
This compressor comprises first and second volutes describing an orbital relative movement and each comprising a plate from which a spiral extends, the two spirals being engaged one inside the other and defining pairs of compression chambers of variable volume. The compressor has a housing formed in that surface of the plate of the first volute which is turned towards the spirals, which housing opens into one of the compression chambers, refrigerant delivery means leading into the housing, and a nonreturn device being mounted in the housing, the nonreturn device preventing communication between the delivery means and the compression chamber into which housing opens in a first or closed position, and allowing communication between the delivery means and said compression chamber in a second or open position.

Description:
BACKGROUND 
     The present invention relates to a scroll-type refrigerator compressor. 
     In a known way, a scroll type refrigerator compressor comprises first and second volutes describing an orbital relative movement, each volute including a plate from which a spiral extends, the two spirals being engaged one inside the other and delimiting pairs of compression chambers of variable volume, the compression chambers having a volume which gradually decreases from the outside, where admission of refrigerant gas is accomplished inwards. 
     Thus, during the orbital relative movement of the first and second volutes, the refrigerant gas is compressed because of the reduction in the volume of the compression chambers and conveyed to the centre of the first and second volutes. The compressed refrigerant gas in the central portion flows out towards a recovery chamber via a discharge orifice made in one of the first and second volutes. 
     In order to improve the performances of such a compressor according to the seasons, and more particularly according to the demand for cold it is known how to make compressors with variable capacity and with variable compression level. 
     Document U.S. Pat. No. 7,100,386 describes a scroll-type refrigerator compressor with variable capacity comprising an orifice for letting through a refrigerant gas, made in the plate of one of the volutes and opening into one of the compression chambers. 
     This compressor further comprises a bypass circuit communicating with the passage orifice and a bypass valve arranged for diverting a portion of the refrigerant gas contained in the compression chambers towards the low pressure side of the compressor. With these arrangements it is possible to reduce the capacity or cylinder volume of the compressor. 
     This compressor also comprises a circuit for injecting refrigerant gas, communicating with the passage orifice and an injection valve arranged for injecting refrigerant gas into the compression chambers towards the low pressure side of the compressor. With these arrangements it is possible to increase the capacity of the compressor. 
     Thus, by suitably controlling the opening and closing of the injection and bypass valves, it is possible to adapt the capacity of the compressor according to the demand for cold. 
     According to a first embodiment described in document U.S. Pat. No. 7,100,386, the injection and bypass valves are both arranged outside the compressor. According to a second embodiment described in U.S. Pat. No. 7,100,386, the injection valve is arranged outside the compressor and the bypass valve is arranged in the suction stage. 
     Consequently, the distances between the passage orifice and the injection and bypass valves are significant, which generates a significant dead space. 
     Thus, when one of the valves or when both valves are in the closed position, a significant amount of refrigerant gas may flow through the passage orifice of the compression chambers towards the dead spaces of the injection and/or bypass circuits. 
     Now, since the pressure in each compression chamber varies from a minimum value to a maximum value during the orbital relative movement of the first and second volutes, the result of this is the occurrence of pressure pulsations in the injection and/or bypass circuits. These pressure pulsations cause overpressures and depressions in the compression chambers which may be detrimental to the performances of the compressor. 
     In order to overcome these drawbacks, positioning an anti-return device in proximity to the orifice for letting through refrigerant gas, made in the plate of the fixed volute, is known from document U.S. Pat. No. 4,475,360. 
     For this purpose, the surface of the plate of the fixed volute turned towards the side opposite to the spirals comprises a housing in which an anti-return device is mounted. The anti-return device is mobile between an open position allowing refrigerant gas to be injected into the compression chamber into which the passage orifice opens out, and a closed position preventing backflow of refrigerant gas from said compression chamber towards the refrigerant gas injection means. 
     With these arrangements it is possible to avoid the generation of significant dead space and therefore the occurrence of pressure fluctuations which may reduce the performances of the compressor. 
     However, installing an anti-return device on the upper surface of the fixed volute of a compressor may prove to be difficult, or even impossible notably when the access to the upper portion of the fixed volute is hindered by the existence of a bell covering the fixed volute or by the presence of seal elements at the discharge orifice. 
     SUMMARY 
     The present invention aims at finding a remedy to these drawbacks. 
     The technical problem at the basis of the invention therefore consists of providing a scroll-type refrigerator compressor which is of a simple and economical structure, while allowing simple and easy mounting of an anti-return device on one of the volutes of the compressor. 
     For this purpose, the invention relates to a scroll-type refrigerator compressor, comprising first and second volutes describing an orbital relative movement, each volute including a plate from which a spiral extends, both spirals being engaged inside each other and delimiting at least two compression chambers of variable volume, 
     characterized in that the compressor includes:
         at least one housing formed in the surface of the plate of one of the first and second volutes turned towards the spirals, the housing opening out into one of the compression chambers,   means for discharging and/or injecting refrigerant fluid, opening out into the housing,   an anti-return device mounted in the housing, the anti-return device being arranged so as to prevent communication between means for discharging and/or injecting refrigerant fluid and the compression chamber into which the housing opens out in a first closed position, and being arranged so as to allow communication between the means for discharging and/or injecting refrigerant fluid and the compression chamber into which the housing opens out in a second open position.       

     The machining of a housing arranged for receiving an anti-return device in the surface of the plate of one of the volutes turned towards the spirals may easily be achieved, and is by no means hindered by the presence of a bell covering the fixed volute or of seal elements at the discharge orifice. 
     Thus, the compressor according to the invention allows simple and easy mounting of an anti-return device on one of the volutes of the compressor. 
     According to an embodiment of the invention, the anti-return device comprises a member forming a valve seat and an anti-return valve movable between a closed position of the anti-return device in which the anti-return valve bears against the member forming a valve seat and an open position of the anti-return device in which the anti-return valve is moved away from the member forming a valve seat. With these arrangements it is possible to select the constitutive material of the valve seat, which may be very advantageous in the case of a specific application. 
     Preferably, the anti-return valve is an elastically deformable strip firmly secured to the member forming a valve seat. 
     According to another embodiment of the invention, the housing delimits a valve seat, and the anti-return device comprises an anti-return valve movable between a closed position of the anti-return device in which the anti-return valve bears against the valve seat and an open position of the anti-return device in which the anti-return valve is moved away from the valve seat. 
     Preferably, the compressor includes a partial obturation device mounted in the housing and arranged so as to partly obdurate the latter. The obturation device delimiting at least in part an orifice for letting through refrigerant fluid opening out into one of the compression chambers, the passage orifice being arranged so as to have said compression chamber communicate with the means for discharging and/or injecting refrigerant fluid when the anti-return device is in its open position. With these arrangements it is possible to easily obtain passage orifices having difficult or even impossible shapes to be made by machining the plate of the volutes. These arrangements also ensure great selection freedom as to the shape, the size and the positioning of the passage orifice. 
     Advantageously, the obturation device is mounted in the housing so that its surface turned towards the spirals are substantially aligned with the surface of the plate in which the housing is made. 
     Advantageously, the passage orifice is proportioned so that the spiral of the upper of the first and second volutes prevents communication between both compression chambers through the passage orifice during the orbital relative movement of both volutes. With these arrangements, it is possible to avoid leaks of fluid between two compression chambers and therefore a reduction in the performances of the compressor. 
     Preferentially, the passage orifice has a section of elongated shape and a width substantially less than or equal to the thickness of the spiral of the upper one of the first and second volutes. With these arrangements it is possible to increase the diverted amount of refrigerant fluid towards the means for discharging and/or injecting refrigerant fluid, and therefore to increase the yield of the compressor. 
     Advantageously, the passage orifice is partly delimited by the obturation device and partly by the wall of the housing. Alternatively, the passage orifice is entirely delimited by the obturation device. 
     According to an alternative embodiment, the passage orifice has a circular shape and the opening of the latter which opens out into the compression chamber is achieved by removing material from the surface of the insert turned towards the spirals and from the circumference of the passage orifice so that said opening has larger dimensions than those of the passage orifice. 
     Preferably, the member forming a valve seat is made with the obturation device out of the same material. 
     Advantageously, the compressor comprises means for controlling the anti-return device arranged so as to displace the latter between its closed and open positions. 
     Preferentially, the control means are arranged so as to connect the means for discharging refrigerant fluid, alternately with a high pressure fluid supply circuit and a low pressure fluid supply circuit, the anti-return device being displaced in its closed position when the means for discharging refrigerant fluid are connected with the high pressure fluid supply circuit, and in its open position when the means for discharging refrigerant fluid are connected with the low pressure fluid supply circuit. 
     According to another embodiment of the invention, the control means are arranged so as to connect the refrigerant fluid injection means with a refrigerant fluid injection circuit, the anti-return device being displaced into its open position when the refrigerant fluid injection means are connected with the refrigerant fluid injection circuit. 
     Advantageously, the means for discharging refrigerant fluid include a discharge conduit, one of the ends of which opens out into the housing and the other end of which opens out into a refrigerant gas suction space delimited by the compressor. 
     According to another embodiment of the invention, the means for discharging refrigerant fluid include a discharge conduit, one of the ends of which opens out into the housing and the other end of which opens out into a discharge opening made in the plate of one of the first and second volutes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In any way, the invention will be better understood with the following description, with reference to the appended schematic drawing illustrating as non-limiting examples, several embodiments of this scroll-type refrigerator compressor. 
         FIG. 1  is a longitudinal sectional view of a first compressor. 
         FIG. 2  is a longitudinal sectional view at an enlarged scale, of the fixed volute of the compressor of  FIG. 1 . 
         FIGS. 3 and 4  are partial longitudinal sectional views at an enlarged scale, of a detail of the fixed volute of the compressor of  FIG. 1 . 
         FIG. 5  is a view showing the passage orifice made in the plate of the fixed volute. 
         FIG. 6  is a longitudinal sectional view of a second compressor. 
         FIG. 7  is a longitudinal sectional view, at an enlarged scale, of the fixed volute of the compressor of  FIG. 6 . 
         FIGS. 8 and 9  are partial longitudinal sectional views at an enlarged scale, of a detail of the fixed volute of the compressor of  FIG. 6 . 
         FIG. 10  is a longitudinal sectional view, at an enlarged scale, of the fixed volute of a third compressor. 
         FIGS. 11 and 12  are partial longitudinal sectional views, at an enlarged scale, of a detail of the fixed volute of the compressor of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the following description, the same elements are designated by the same references in the different embodiments. 
       FIG. 1  describes a scroll-type refrigerator compressor with variable speed, occupying a vertical position. However, the compressor according to the invention may occupy a tilted position or a horizontal position, without its structure being significantly modified. 
     The compressor illustrated in  FIG. 1  comprises a sealed enclosure delimited by a ferrule  2 , the upper and lower ends of which are respectively closed by a lid  3 , and a base  4 . Assembling this enclosure may notably be achieved by means of welding beads. 
     The ferrule  2  comprises a refrigerant gas inlet (not shown in  FIG. 1 ) opening out into a suction space for achieving inflow of refrigerant gas to the compressor. 
     The intermediate portion of the compressor is occupied by a body  5  used for mounting a stage  7  for compressing the refrigerant gas. This compressor stage  7  comprises a fixed volute  8  including a plate  9  from which extends a fixed spiral  10  turned downwards, and a mobile volute  11  including a plate  12  bearing against the body  5  and from which extends a spiral  13  turned upwards. Both spirals  10  and  13  of both volutes interpenetrate each other in order to form compression chambers  14  with a variable volume. 
     Admission of the gas into the compression stage is accomplished from the outside, the compression chambers  14  having a variable space which decreases from the outside to the inside, during the movement of the mobile volute  11  relatively to the fixed volute  8 , the compressed gas escaping at the centre of the volute through a discharge opening  15  made in the fixed volute  8  towards a high pressure chamber  16  from which it is discharged through a fitting (not shown in the figure). 
     The compressor comprises a separation plate  40  covering the fixed volute  8  and sealably mounted on the latter. The separation plate  40  delimits two spaces, a low pressure suction space located below the latter, and a high pressure discharge space positioned above the latter. 
     The compressor comprises an electric motor positioned in the suction space, the electric motor comprises a stator  17  at the centre of which is positioned a rotor  18 . 
     The rotor  18  is firmly secured to a drive shaft  20 , the upper end of which is offset in the fashion of a crankshaft. This upper portion is engaged into a sleeve-shaped portion  21  which the mobile volute  11  includes. Upon its being driven into rotation by the motor, the drive shaft  20  drives the mobile volute  11  following an orbital movement. 
     The lower end of the drive shaft  20  drives an oil pump  22  supplying with oil contained in a case  23  delimited by the base  4 , an oil supply conduit  24  made in the central portion of the drive shaft, the supply conduit  24  being offset and extends over a portion of the length of the drive shaft  20 . 
     As shown more particularly in  FIGS. 2 to 4 , the compressor also comprises a substantially cylindrical housing  25  made in the lower surface of the plate  9  of the fixed volute  8 , i.e. the surface of the plate  9  turned towards the spirals  10 ,  13 . The housing  25  opens out into one of the compression chambers  14 . The housing  25  has a maximum diameter substantially corresponding to the radial distance between two adjacent portions of the spiral  10  of the fixed volute  8 . 
     The compressor further comprises an anti-return device  26  mounted in the housing  25 . The anti-return device  26  comprises a member  27  forming a valve seat inserted into the housing  25  and delimiting a passage opening  28  on the one hand, and an anti-return valve  29  on the other hand, movable between a closed position (shown in  FIG. 3 ) in which the anti-return valve  29  bears against the member forming a valve seat  27  and obturates the passage opening  28 , an open position (shown in  FIG. 4 ) in which the anti-return valve  29  is moved away from the member forming a valve seat  27  and clears the passage opening  28 . The anti-return valve  29  has a substantially circular shape. 
     The compressor further comprises an obturation device  30  mounted in the housing  25  and arranged in order to obturate the latter. The obturation device  30  is also arranged so as to maintain the member forming a valve seat  27  in position, and more particularly for flattening the member forming a valve seat  27  against a bottom wall of the housing  25 . Advantageously, the obturation device  30  comprises a substantially cylindrical obturation member  31  fixed in the housing  25 . Preferably, the obturation member  31  is fixed in the housing  25  by adhesive bonding, screwing or force-fitting. The obturation member  31  is attached in the housing  25  so that its surface turned towards the spirals  10 ,  13  is flush with the lower surface of the plate  9  of the fixed volute  8 . 
     The obturation member  31  partly delimits an orifice for letting through refrigerant gas  32  opening out into one of the compression chambers  14  and communicating with the passage opening  28  delimited by the member forming a valve seat  27 . 
     Advantageously, the passage orifice  32  is proportioned so that the spiral  13  of the mobile volute  11  prevents connection of both compression chambers  14  through the passage orifice  32  during the orbital movement of the mobile volute  11 . 
     As shown more particularly in  FIG. 5 , the passage orifice  32  has a section with an elongated shape and a width substantially less than or equal to the thickness of the spiral  13  of the mobile volute  11 . Preferentially, the passage orifice  32  is delimited partly by the obturation member  31  and partly by the wall of the housing  25 . Consequently, the passage orifice  32  substantially opens out along the wall of the spiral  10  of the fixed volute  8 . 
     According to an alternative embodiment, the passage orifice  32  may be entirely delimited by the obturation member  31 . 
     The compressor comprises a refrigerant gas discharge conduit  33  comprising a first end  34  opening out into the housing  25  downstream from the anti-return valve  29  relatively to the member forming a valve seat  27 , and a second end  35  opening out into the suction space delimited by the ferrule  2 . 
     As shown in  FIG. 4 , during the orbital movement of the mobile volute  11  and when the anti-return valve  29  is in its open position, part of the compressed refrigerant gas in the compression chamber  14  into which opens out the passage orifice  32 , is discharged into the suction space while successively flowing through the passage orifice  32 , the passage opening  28  delimited by the member forming a valve seat  27 , and the discharge conduit  33 . 
     With these arrangements, it is possible to reduce the amount of compressed refrigerant gas during the compressor operating cycle, and therefore to reduce the capacity of the latter. 
     Of course, such a reduction in the capacity of the compressor is not continually desired. 
     Thus, the compressor comprises means  37  for controlling the anti-return device arranged for displacing the anti-return valve  29  between its closed and open positions depending on whether it is desired to use the maximum capacity of the compressor or not. 
     The control means are arranged so as to alternately connect the discharge conduit  33  to a high pressure fluid supply circuit  38  and to a low pressure fluid supply circuit  39 . 
     When it is desired to use the maximum capacity of the compressor, the control means connect the discharge conduit  33  to the high pressure fluid supply circuit  38 . Thus, the anti-return valve  29  is subject, on its face opposite to the member forming a valve seat  27 , to the pressure of a high pressure fluid so that the anti-return valve  29  is held flattened onto the member forming a valve seat  27  and it isolates the compression chamber  14  into which opens out the passage orifice  32 , from the suction space. 
     When it is desired to reduce the useful capacity of the compressor, the control means connect the discharge conduit  33  to the low pressure fluid supply circuit  39 . Thus, the anti-return valve  29  is subject, on its face opposite to the member forming a valve seat  27 , to the pressure of a low pressure fluid so that the anti-return valve  29  is lifted and connects the compression chamber  14  into which opens out the passage orifice  32 , with the suction volume. In order to promote the displacement of the anti-return valve  29  towards its open or closed position, a spring acting in an opening or closing direction of the valve may be associated with the latter. 
     According to an alternative embodiment, the control means may be arranged in order to alternately connect the discharge conduit  33  to a high pressure fluid supply circuit  38  and to the suction space delimited by the ferrule of the compressor. 
       FIGS. 6 to 9  illustrate a second embodiment of the invention. 
     According to this embodiment, the compressor comprises two substantially cylindrical housings  25  made in the lower surface of the plate  9  of the fixed volute  8 . The compressor further comprises an anti-return device  26  and an obturation device  30  mounted in each housing  25 . 
     According to this embodiment, the member forming a valve seat  27  of each anti-return device  26  is made together with the obturation member  31  of the corresponding obturation device  30 , in the same material. 
     Further, according to this embodiment, the anti-return valve  29  of each anti-return device  26  consists of a strip firmly secured to the corresponding member forming a valve seat  27  and elastically deformable between a closed position (shown in  FIG. 8 ) in which the valve  29  bears against the corresponding member forming a valve seat  27  and obturates the passage opening  28  delimited by the latter and an open position (shown in  FIG. 9 ) in which the valve bears against a retaining plate  45  firmly secured to the corresponding member forming a valve seat  27  and clears the passage opening  28  delimited by the latter. Advantageously, the abutment plate  45  of each anti-return device  26  is attached by screwing onto the corresponding member forming a valve seat  27 . 
     Thus, each anti-return device  26  and each corresponding obturation device  30  form a cartridge unit, which facilitates the mounting of the anti-return and obturation devices in the respective housings. 
     According to this embodiment, the compressor comprises two refrigerant gas discharge conduits, each discharge conduit  33  including a first end opening out into one of the housings  25  and a second end opening out into the discharge opening  15  made in the fixed volute  8 . 
     Advantageously, the compressor does not include any means for controlling the anti-return valve  29  of each anti-return device  26 . 
     In this case, each anti-return valve  29  is arranged so as to deform only towards its open position when the compression in the compression chamber  14  into which opens the corresponding passage orifice  32 , is greater than the pressure in the discharge orifice  15 . 
     Thus, when the anti-return valve  29  of each anti-return device  26  is subject, on its face turned towards the member forming a valve seat, to a pressure of less than the pressure in the discharge orifice  15 , the valve  29  is maintained flattened on the member forming a valve seat (as this is shown in  FIG. 8 ) and isolates the compression chamber  14  into which opens out the corresponding passage orifice  32  of the discharge orifice  15  made in the fixed volute  8 . The result of this is that the compression level of the compressor is maintained at its maximum value. 
     When the anti-return valve  29  of each anti-return valve  26  is subject, on its face turned towards the member forming a valve seat, to a greater pressure than the pressure in the discharge orifice  15 , the valve  29  elastically deforms towards its open position (as this is shown in  FIG. 9 ) and connects the compression chamber  14  into which opens out the corresponding passage orifice  32 , with the discharge orifice  15  made in the fixed volute  8 . Thus the result of this is backflow towards the discharge orifice  15  of a portion of the compressed refrigerant gas in the compression chambers  14  into which the passage orifices  32  open out, before this portion of the refrigerant gas reaches the center of the spirals  10 ,  13 . 
     With these arrangements, it is possible to reduce the compression level of each compression chamber and therefore of the compressor, and consequently improve the yield of the compressor. 
     With this arrangement, it is also possible to avoid obtaining too high pressures in the compression volume. 
     According to an alternative embodiment, each discharge conduit  33  may include a first end opening out into one of the housings  25  and a second end opening out into the high pressure chamber  16 . 
     According to an alternative embodiment, the compressor may only include a single cartridge or two identical cartridges. 
       FIGS. 10 to 12  illustrate a third embodiment of the invention which differs from the first embodiment essentially in that the valve seat is delimited by the housing  25 , and in that the compressor comprises a refrigerant gas injection conduit  41  comprising a first end  42  opening out into the housing  25  downstream from the anti-return valve  29  relatively to the obturation member  31 , and a second end  43  connected to a circuit for injecting refrigerant gas (not shown in the figure). 
     According to this embodiment, the control means  137  of the anti-return device are arranged in order to connect the injection conduit  41  with the circuit for injecting refrigerant gas on the one hand, and for isolating the injection conduit  41  from the circuit for injecting refrigerant gas, on the other hand. 
     When it is desired to use the useful capacity of the compressor, the control means  137  isolate the injection conduit  41  with respect to the refrigerant gas injection circuit. Thus, the anti-return valve  29  is subject, on its face turned towards the obturation member  31 , to the pressure of the compressed refrigerant gas in the compression chamber  14  into which the passage orifice  32  opens out so that the anti-return valve  29  is maintained flattened on its valve seat and isolates said compression chamber  14  from the injection conduit  41 . In order to promote this flattening of the anti-return valve against its seat, a spring acting in a direction for closing the valve may be inserted between the latter and the obturation member  31 . 
     When it is desired to increase the useful capacity of the compressor, the control means  137  connect the injection conduit  41  to the refrigerant gas injection circuit. Thus, the anti-return valve  29  is subject, on its face opposite to the obturation member  31 , to the pressure of a high pressure fluid so that the anti-return valve  29  will be flattened against the obturation member  31  and connects the compression chamber  14  into which the passage orifice  32  opens out, with the injection conduit  41 , which allows injection of refrigerant gas into said compression chamber  14 . 
     With these arrangements it is possible to increase the amount of compressed refrigerant gas in the compression chambers during the operating cycle of the compressor, and therefore increase the capacity of the latter. 
     As this is obvious, the invention is not limited to the sole embodiment of this scroll-type refrigerator compressor, described above as examples, on the contrary it encompasses all the alternative embodiments thereof.