Patent Publication Number: US-7581936-B2

Title: Hermetically sealed compressor having oil supply mechanism based on refrigerant pressure

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a hermetically sealed compressor used for refrigeration and air-conditioning, and particularly to a technique of enhancing COP (Coefficient Of Performance: refrigeration power/input power) of a hermetically sealed compressor. 
   2. Description of the Related Art 
   There is known a hermetically sealed rotary compressor including an electrically-driven element and a rotary compression element driven by the electrically-driven element to compress refrigerant that are accommodated in a hermetically sealed container. This type of hermetically sealed rotary compressor is disclosed in JP-A-6-323276, for example. According to this hermetically sealed rotary compressor, an eccentrically rotating roller is disposed in a cylinder so as to keep predetermined clearance from the inner surface of the cylinder and form a crescent-shaped space (so-called compression chamber) in the cylinder. Furthermore, a vane is provided so as to come into sliding contact with the roller, and the crescent-shaped space is partitioned to a refrigerant-sucking low-pressure chamber side and a refrigerant-compressing high pressure chamber side by the vane in terms of pressure. 
   However, the conventional hermetically sealed rotary compressor has a problem that the sealing performance of the crescent-shaped space is not sufficient, resulting in reduction of the cooling efficiency of the hermetically sealed rotary compressor. 
   SUMMARY OF THE INVENTION 
   The present invention has been implemented in view of the foregoing situation, and has an object to provide a hermetically sealed compressor in which the sealing performance between a roller and a cylinder is enhanced and thus the cooling efficiency can be enhanced. 
   According to an aspect of the present invention, there is provided a hermetically sealed compressor comprising: an electrically-driven element; a rotary compressing element driven by the electrically-driven element to compress refrigerant; the rotary compressing element having at least one cylinder including a compression chamber in which the refrigerant is compressed; a hermetically sealed container in which the electrically-driven element and the rotary compressing element are accommodated and oil is stocked; an oil path for injecting the oil into the compression chamber when the refrigerant is sucked into the compression chamber of the cylinder constituting the rotary compressing element; and an opening/closing valve for opening/closing the oil path in accordance with the refrigerant discharge pressure of the rotary compressing element or the pressure of the compressed refrigerant compressed by the rotary compressing element. 
   In the hermetically sealed compressor, the opening/closing valve is opened/closed in accordance with the differential pressure between the refrigerant suction pressure and the reference discharge pressure of the compression chamber, and set to an open state when the differential pressure is low. 
   In the hermetically sealed compressor according to claim  1 , the opening/closing valve is opened/closed in accordance with the pressure of the compressed refrigerant, and is set to an open state when the pressure of the compressed refrigerant is low. 
   The hermetically sealed compressor further comprises a compressed refrigerant introducing path for applying the pressure of the compressed refrigerant discharged from the discharge pipe of the hermetically sealed container to the opening/closing valve. 
   According to another aspect of the present invention, there is provided a hermetically sealed compressor including an electrically-drive element, a rotary compressing element that is driven by the electrically-driven element and has at least one cylinder including a compression chamber in which the refrigerant is compressed, and a hermetically sealed container in which the electrically-driven element and the rotary compressing element are accommodated, further comprising: an oil supply pipe for supplying oil; an oil path that is connected to the oil supply pipe and injects the oil into the compression chamber when the refrigerant is sucked into the compression chamber; and an electromagnetic valve that is provided to the oil supply pipe and opened/closed in accordance with a driving frequency of the rotary compressing element. 
   In the hermetically sealed compressor, the electromagnetic valve is set to an open state when the rotary compressing element is set to a low load power area. 
   In the hermetically sealed compressor, the oil is stocked in the hermetically sealed container and the oil is supplied to the oil path through the oil supply pipe. 
   The hermetically sealed compressor further comprises a refrigerant circuit having an oil separator, wherein the oil supply pipe is connected to the oil separator, and the oil separated from the refrigerant by the oil separator is led through the oil supply pipe to the oil path. 
   The hermetically sealed compressor further comprises a pressure reducing unit that is provided between the oil separator and the electromagnetic valve and reducing the pressure of the oil supplied from the oil separator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinally-sectional view showing the construction of a hermetically sealed rotary compressor according to a first embodiment of the present invention; 
       FIG. 2  is an enlarged longitudinally-sectional view showing a rotary compressing element; 
       FIG. 3  is a plan view showing a cylinder; 
       FIG. 4  is an enlarged longitudinally-sectional view showing an oil injecting portion and an opening/closing valve; 
       FIG. 5  is a longitudinally-sectional view showing the construction of a hermetically sealed rotary compressor according to a second embodiment of the present invention. 
       FIG. 6  is an enlarge longitudinally-sectional view showing a rotary compressing element; 
       FIG. 7  is a plan view showing a cylinder; 
       FIG. 8  is an enlarged longitudinally-sectional view showing a oil path and an opening/closing valve; 
       FIG. 9  is a diagram showing a refrigerating circuit according to a third embodiment of the present invention; 
       FIG. 10  is a longitudinally-sectional view showing an example of the hermetically sealed rotary compressor according to this embodiment; 
       FIG. 11  is an enlarged longitudinally-sectional view showing the rotary compressing element; 
       FIG. 12  is a plan view showing a cylinder; 
       FIG. 13  is an enlarged longitudinally-sectional view showing an oil path; and 
       FIG. 14  is a diagram showing a refrigerating circuit according to a modification of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments according to the present invention will be described hereunder with reference to the accompanying drawings. 
   First Embodiment 
     FIG. 1  is a longitudinally-sectional view showing a hermetically sealed rotary compressor according to a first embodiment of the present invention, and  FIG. 2  is an enlarged longitudinally-sectional view of a rotary compressing element. The hermetically sealed rotary compressor  100  constructs a refrigerating unit by connecting a condenser for refrigerant and an evaporator for refrigerant through a pipe. As shown in  FIG. 1 , the hermetically sealed rotary compressor  100  has a hermetically sealed container  1 , an electrically-driven element  2  accommodated at the upper side of the hermetically sealed container  1 , and a rotary compressing element  4  accommodated at the lower side of the hermetically sealed container  1 . The rotary compressing element  4  is driven by a crank shaft  3  of the electrically-driven element  2  to compress refrigerant. 
   The hermetically sealed container  1  is equipped with a cylindrical shell portion  10 , and an end cap  11  fixed to the shell portion  10  by arc welding or the like, and the end cap  11  is provided with a terminal  12  serving as a relay terminal when power is supplied to the electrically-driven element  2 , and a discharge pipe  13  for discharging compressed refrigerant to the outside of the compressor  100 . Furthermore, a suction pipe  6  for leading refrigerant from an accumulator  5  to the rotary compressing element  4  is fixed to the neighborhood of the bottom portion of the shell portion  10  by welding, for example. 
   The electrically-driven element  2  comprises a DC motor such as a so-called DC brushless motor or the like, and it is equipped with a rotor  31  and a stator  32  fixed to the shell portion  10 . The crank shaft  3  is fixed to the rotor  31 , and the crank shaft  3  is freely rotatably mounted to a primary bearing  7 A and an secondary bearing  7 B equipped to the rotary compressing element  4  so that the rotating force of the rotor  31  is transmitted to the rotary compressing element  4 . 
   The rotary compressing element  4  has one cylindrical cylinder  41 , and it is pinched between the primary bearing  7 A (support member) and the secondary bearing  7 B and integrally fixed to the primary bearing  7 A and the secondary bearing  7 B by bolts or the like. 
   The primary bearing  7 A is fixed to the inner surface of the hermetically sealed container  1 , and the cylinder  41  is supported in the hermetically sealed container  1  by the primary bearing  7 A. The opening at the upper side of the cylinder  41  is closed by the primary bearing  7 A, and also the opening at the lower side of the cylinder  41  is closed by the secondary bearing  7 B, thereby forming a compression chamber  43  in the cylinder  41 . 
   A roller  45  which is fitted in an eccentric portion integrally formed with the crank shaft  3  and eccentrically rotated is provided in the compression chamber  43 . Furthermore, as shown in  FIG. 3 , a refrigerant suction port  48  and a refrigerant discharge port  40  are formed in the cylinder  41 . A vane groove  47  extending in the radial direction of the cylinder  41  is provided between the suction port  48  and the discharge port  40 , and a vane  46  is freely slidably provided in the vane groove  47 . The vane  46  is pressed against the roller  45  by an urging member such as a spring or the like at all times. When the roller  45  is eccentrically rotated, the vane  46  reciprocates in the vane groove  47  in sliding contact with the outer peripheral surface of the roller  45 , and it serves to partition the inside of the compression chamber  43  into a low-pressure chamber side  43 A and a high-pressure chamber side  43 B in terms of pressure. 
   More specifically, the cylindrical space in the cylinder  41 , that is, the compression chamber  43  for refrigerant is constructed in a crescent-shape because the roller  45  is eccentrically disposed in the cylinder  41 . The contact of the vane  46  with the peripheral surface of the roller  45 A partitions the crescent-shaped compression chamber  43  into the low-pressure chamber side  43 A at the refrigerant suction port  48  side and the high-pressure chamber side  43 B at the refrigerant discharge port  40  side. 
   As shown in  FIG. 1 , the suction pipe  6  is engagedly inserted in the suction port  48  of the cylinder  41 , and the discharge port  40  shown in  FIG. 3  is provided with a discharge valve. When the refrigerant pressure of the high-pressure chamber side  43 B reaches a discharge pressure regulated by the discharge valve, the refrigerant is discharged from the discharge port  40  into the hermetically sealed container  1 . 
   That is, in the hermetically sealed rotary compressor  100 , the electrically-driven element  2  rotates the crank shaft  3 , so that the roller  45  is eccentrically rotated in the compression chamber  43 . Accordingly, the refrigerant supplied from the outside of the compressor through the accumulator  5  is sucked through the suction pipe  6  into the lower pressure chamber side  43 A of the compression chamber  43 . The refrigerant thus sucked is compressed while fed to the high-pressure chamber side  43 B, discharged from the discharge port  40  into the hermetically sealed container  1  and then discharged from the discharge pipe  13  to the outside of the compressor. 
   As shown in  FIG. 1 , oil  8  is stocked at the bottom portion of the hermetically sealed container  1  until the lower surface of the primary bearing  7 A (indicated by a line A-A′ in  FIGS. 1 and 2 . The lower end portion  3 A of the crank shaft  3  is provided with an oil pickup  50  serving as an oil supply device for supplying the oil  8  to the primary bearing  7 A, the secondary bearing  7 B, the rubbing portion between the rotary compressing element  4  and the crank shaft  3  and the sliding portion of the rotary compressing element  4 . 
   Specifically describing, the crank shaft  3  is designed in a cylindrical shape, and a cylindrical oil pickup  50  is pressed in the lower end portion  3 A of the crank shaft  3 . As shown in  FIG. 2 , a paddle  51  constituting a spiral oil flow path is integrally formed in the oil pickup  50 . When the crank shaft  3  is rotated, the oil  8  stocked in the hermetically sealed container  1  is sucked up from the lower end  50 A of the oil pickup  50  by centrifugal force in connection with the rotation of the paddle  51 , passed through an oil supply hole  52  formed at the upper end side of the oil pickup  50  and then supplied as lubricating oil to the primary bearing  7 A, the secondary bearing  7 B and each rubbing portion between the rotary compressing element  4  and the crank shaft  3 . 
   In order to prevent the abrasion between the roller  45  and the cylinder  41  when the roller  45  is eccentrically rotated, the roller  45  is designed so that predetermined clearance is kept between the roller  45  and the inner surface  49  of the cylinder  41  at the contact place therebetween. However, this clearance degrades the sealing performance of the compression chamber  43 , particularly the sealing performance between the low-pressure chamber side  43 A and the high-pressure chamber side  43 B, and the cooling efficiency would be reduced unless any countermeasure is taken. 
   Therefore, the hermetically sealed rotary compressor  100  of this embodiment is equipped with an oil injecting portion  60  for injecting the oil  8  stocked in the hermetically sealed container  1  into the compression chamber  43  when the refrigerant is sucked into the compression chamber  43 . By injecting the oil  8  into the compressing chamber  43 , oil film is formed between the roller  45  and the cylinder  41  to thereby enhance the sealing performance. 
   As shown in  FIG. 2 , the oil injecting portion  60  comprises an oil stocking portion  61  for stocking the oil  8  and an oil path  62  for leading the oil  8  stocked in the oil stocking portion  61  to the compression chamber  43  of each of the cylinder  41 . 
   The oil stocking portion  61  is formed by providing an annular space along the outer peripheral surface of the crank shaft  3  at the rubbing face of the primary bearing  7 A against the crank shaft  3 . Accordingly, when the oil pickup  50  supplies the oil  8  to each rubbing portion between the rotary compressing element  4  and the crank shaft  3 , a part of the oil  8  is stocked in the oil stocking portion  61 . 
   The oil path  62  is designed so as to extend from the oil stocking portion  61  and intercommunicate with the compressing chambers  43  of the respective cylinder  41 . During the suction process of the refrigerant, the oil  8  in the oil stocking portion is led to the compressing chambers  43 . 
   More specifically, the oil path  62  comprises an secondary oil path  63  formed in the primary bearing  7 A as shown in  FIG. 4 , and a primary oil path  64  formed in the cylinder  41  so as to intercommunicate with the secondary oil path  63 . 
   The secondary oil path  63  comprises a first oil path  65  penetrating from the outer peripheral surface of the primary bearing  7 A to the oil stocking portion  61 , and a second oil path  66  penetrating through the primary bearing  7 A in the vertical direction (thickness direction) and intercommunicating with the first oil path  65 . Accordingly, the oil  8  stocked in the oil stocking portion  61  is led to the primary oil path  64  of the cylinder  41  through the first oil path  65  and the second oil path  66 . 
   When the primary bearing  7 A is fixed to the hermetically sealed container  1  by carrying out tack-welding from the outside of the hermetically sealed container  1 , the place P corresponding to the opening end  65 A of the first oil path  65  at the outer peripheral surface side of the primary bearing  7 A is tack-welded from the outside of the hermetically sealed container  1 , whereby the opening end  65 A can be closed in close contact with the inner surface of the hermetically sealed container  1  simultaneously with the fixing of the primary bearing  7 A. Accordingly, the opening end  65 A can be closed without separately using any member for closing the opening end  65 A, so that the cost can be reduced and the fabrication working process can be simplified. When not the primary bearing  7 A, but the cylinder  41  is fixed to the hermetically sealed container  1 , the opening end  65 A of the first oil path  65  may be closed by using plug or the like. 
   The primary oil path  64  is provided on the upper surface of the cylinder  41 , and it is formed as a narrow groove so that one end thereof intercommunicates with the opening end of the second oil path  66  and the other end thereof extends so as to intercommunicate with the compression chamber  43 . Accordingly, the oil  8  led from the secondary oil path  63  is led through the primary oil path  64  into the compression chamber  43 . Furthermore, in connection with the suction of the refrigerant into the low-pressure chamber side  43 A of the compression chamber  43 , one end  64 A of the primary oil path  64  is opened to the inner surface  49  of the cylinder of the low-pressure chamber side  43 A as shown in  FIG. 3  so that the oil  8  stocked in the oil stocking portion  61  is injected in the compression chamber  43 . 
   That is, the refrigerant discharge pressure (for example, 3 MPa) is applied to the oil  8  in the hermetically sealed container  1 . Accordingly, by opening one end  64 A of the primary oil path  64  to the low-pressure chamber side  43   a , the high-pressure oil  8  stocked in the oil stocking portion  61  is passed through the oil path  62  comprising the secondary oil path  63  and the primary oil path  64  by the differential pressure between the pressure of the oil  8  and the inner pressure (for example, 1.1 MPa) of the low-pressure chamber side  43 A of the compression chamber  43  and led into the low-pressure chamber side  43 A of the compression chamber  43  during the refrigerant suction process. 
   As a result, following the suction of the refrigerant into the compression chamber  43 , the oil  8  is injected into the compression chamber  43 . Therefore, sufficient oil film is formed between the cylinder inner surface  49  and the roller  45  by the oil  8  can be enhanced. Particularly, the oil is injected into the compression chamber  43  during the suction process of the refrigerant into the compression chamber  43 , and the low-pressure chamber side  43 A and the high-pressure chamber side  43 B of the compression chamber  43  can be more surely separated from each other. Therefore, in the process that the refrigerant is fed to the high-pressure chamber side  43 B and compressed (compression process), leakage of the compressed refrigerant into the low-pressure chamber side  43 A can be prevented, and the refrigerant compression efficiency is enhanced, so that the cooling efficiency of the hermetically sealed rotary compressor  100  can be enhanced. 
   When one end  64 A of the primary oil path  64  is formed to be opened at an angle in a predetermined angle range from θ 1  to θ 2  (θ 1 : 0°, θ 2 : 170°, more preferably θ 1 : 125°, θ 2 : 165°) with respect to a reference line L connecting the suction port  48  and the center point O of the cylinder  41 A as shown in  FIG. 3 , the compression efficiency of the refrigerant (about 55° in the example of  FIG. 3 ) can be further enhanced. 
   Here, the amount of the oil  8  injected into the compression chamber  43  can be adjusted by adjusting the cross-section area (opening area) D of the primary oil path opened to the inner surface  49  of the cylinder. According to this embodiment, in order to set the amount of the oil  8  injected into the compression chamber  43  to a proper amount, the cross-section area D of the primary oil path  64  is determined so that the ratio R (=D/V) of the cross-section area D of the primary oil path  64  and the displacement volume V of the compression chamber  43  falls within a predetermined range. 
   More specifically, if the ratio R is excessively small, the primary oil path  64  is excessively narrow and the oil  8  is not injected into the compression chamber  43 . On the other hand, if the ratio R is excessively large, the oil  8  is excessively injected into the compression chamber  43  and thus liquid compression occurs. Therefore, according to this embodiment, the ratio R is set to fall in the range from 0.004 to 0.03 (mm.sup.2/cc), and the cross-sectional area D of the primary oil path  64  is determined on the basis of the ratio R, whereby the sealing performance between the inner surface  49  of the cylinder and the roller  45 A is enhanced with preventing the liquid compression due to excessive injection of the oil  8 . 
   The effect of enhancing the sealing performance by the oil injection into the compression chamber  43  is larger when the rotary compressing element  4  is rotated in a low frequency area (for example, 15 Hz to 30 Hz) and thus the differential pressure between the discharge pressure and the suction pressure is smaller than when the rotary compressing element  4  is rotated in a high frequency area and thus rotated at a high speed. That is, by limiting the oil injection into the compression chamber  43  to the time when the differential pressure is small, the cooling efficiency can be more effectively enhanced with suppressing wasting of the oil  8 . Therefore, according to this embodiment, the oil path  62  is provided with an opening/closing valve  80 , and the opening/closing valve  80  is set to an open state only when the rotary compression element  4  is rotated at a low speed and thus the differential pressure between the discharge pressure and the suction pressure is smaller, thereby injecting the oil  8  into the compression chamber  43 . 
   The construction of the opening/closing valve  80  will be described. As shown in  FIG. 4 , a cylindrical through hole  70  which traverses from the first oil path  65  to the primary oil path  64  and extends to the lower surface of the cylinder  41  is provided in the cylinder  41 , and the opening/closing valve  80  is provided in the through hole  70 . The opening/closing valve  80  comprises a substantially cylindrical valve plug which is engagedly inserted in the through hole  70 , and a spring  82  as an urging member for urging the valve plug  81  to the first oil path  65 . The upper portion  81 A of the valve plug  81  invades into the first oil path  65 , and the pressure in the first oil path  65 , that is, the discharge pressure is applied to the upper portion  81 A. At this time, the upper portion  81 A of the valve plug  81  is designed to be smaller in diameter than the through hole  70 , so that the flow of the oil  8  can be secured even when the upper portion  81  A is located in the first oil path  65 . 
   The narrow groove  83  is formed along the peripheral direction on the outer periphery of the valve plug  81 , and when the valve plug  81  is set and kept to be pressed up to the first oil path  65  side by the spring  82 , the primary oil path  64  which is disconnected by the upper portion  81 A of the valve plug  81  in the through hole  70  is connected through the narrow groove  83  of the valve plug  81 , and the oil injection into the compression chamber  43  is carried out. 
   Furthermore, as shown in  FIG. 3 , an intercommunicating rod  71  extending from the suction port  48  to the through hole  70  is formed on the lower surface of the cylinder  41 , and the suction pressure of the refrigerant is led to the bottom portion of the through hole  70  through the intercommunicating rod  71 . That is, the pressure in the first oil path  65  (that is, the discharge pressure of the rotary compressing element  4 ) is applied to the upper portion  81 A of the valve plug  81 , and the refrigerant suction pressure is applied to the inside of the valve plug  81 . 
   Accordingly, during the period when the discharge pressure of the rotary compressing element  4  is low and thus the differential pressure of the discharge pressure from the suction pressure is small, the valve plug  81  is urged up to be located at the first oil path  65  by the urging force of the spring  82 , and the primary oil path  64  is kept to be connected through the narrow groove  83  of the valve plug  81  to the one end portion  64 A opened to the compression chamber  43 , that is, the open state for oil injection is set. Furthermore, when the discharge pressure of the rotary compressing element  4  is increased and the differential pressure from the suction pressure is increased, the valve plug  81  is pressed down against the urging force of the spring  82 , and the state that the narrow groove  83  of the valve plug  81  and the primary oil path  65  is disconnected from each other, that is, the close state is set. Under this close state, the oil path  62  is closed, and the injection of the oil  8  into the compression chamber  43  is stopped. 
   Accordingly, the oil injection into the compression chamber  43  is limited to the case where the rotary compressing element  4  is driven at a low frequency and thus the differential pressure between the discharge pressure and the suction pressure is small, and the cooling efficiency can be effectively enhanced with suppressing consumption of the oil  8  stocked in the heretically sealed container  1 . 
   As described above, according to this embodiment, the oil  8  is injected into the compression chamber  43  when the refrigerant is sucked into the compression chamber  43 . Therefore, sufficient oil film is formed between the cylinder  41  and the roller  45  by the oil  8  injected in the compression chamber  43 , and thus the sealing performance can be enhanced. Accordingly, the refrigerant during the compression process can be prevented from leaking into the low-pressure chamber side  43 A, and thus the compression efficiency is enhanced, so that the cooling efficiency of the hermetically sealed rotary compressor  100  can be enhanced. 
   Furthermore, according to this embodiment, the ratio between the cross-section area D of the primary oil path  64  constituting the oil path  62  and the displacement volume V of the compression chamber  43  is set to be within a predetermined range. Accordingly, the sealing performance between the cylinder inner surface  49  and the roller  45  can be enhanced with preventing the liquid compression due to excessive injection of the oil  8 . 
   Still furthermore, according to this embodiment, the oil path  62  is provided with the opening/closing valve  80  which is set to the open state only when the discharge pressure of the rotary compressing element  4  is low, that is, in an area where the differential pressure between the discharge pressure and suction pressure of the rotary compressing element  4  is small. Therefore, the oil injection into the compression chamber  43  is limited to the time period when where the differential pressure between the discharge pressure and suction pressure of the rotary compressing element  4 , whereby the cooling efficiency can be effectively enhanced with suppressing the consumption of the oil  8  stocked in the hermetically sealed container  1 . 
   The above embodiment relates to the hermetically sealed rotary compressor  1  having one cylinder  41 , however, the present invention my be applied to a hermetically sealed rotary compressor having two or more compressors. 
   Second Embodiment 
     FIG. 5  is a longitudinally-sectional view showing a hermetically sealed rotary compressor according to a second embodiment of the present invention, and  FIG. 6  is an enlarged longitudinally-sectional view showing a rotary compressing element. The hermetically sealed rotary compressor  100 A constitutes a refrigerating unit by connecting a refrigerant condenser and a refrigerant evaporator through a pipe. As in the case of the hermetically sealed rotary compressor  100 , as shown in  FIG. 5 , the hermetically sealed rotary compressor  100 A has a hermetically sealed container  1 , an electrically-driven element  2  is accommodated at the upper side of the hermetically sealed container  1 , and a rotary compressing element  4  that is driven by a crank shaft  3  of the electrically-driven element  2  to compress the refrigerant is accommodated at the lower side of the hermetically sealed container  1 . 
   As shown in  FIGS. 5 and 6 , the hermetically rotary compressor  100 A of this embodiment has the same basic construction as the fist embodiment. Therefore, the same elements as the first embodiment are represented by the same reference numerals and the description thereof is omitted. 
   The hermetically sealed rotary compressor  100 A of this embodiment is designed so that the oil  8  is injected into the compression chamber  43  when the refrigerant is sucked into the compression chamber  43  in order to enhance the refrigerant compression efficiency as in the case of the first embodiment. The construction of the hermetically sealed rotary compressor  100 A will be specifically described. 
   As shown in  FIG. 8 , step portions  270 A,  270 B are formed within the contact faces with the primary bearing  7 A and the secondary bearing  7 B on the upper and lower surfaces of the cylinder  41  to enhance the close contact. 
   A groove  261  extending in the radial direction is formed on the step portion  270 B at the lower side, that is, on the lower surface of the cylinder  41  making the contact with the secondary bearing  7 B by cutting work, and when the step portion  270 B and the secondary bearing  7 B are brought into close contact with each other, an oil path  260  is formed so that one end  260 A is opened to the inner surface  49  of the cylinder  41  by the groove  261  and the other end  260 B thereof is opened to the oil  8  stocked in the hermetically sealed container  1 . When the oil  8  is stocked in the hermetically sealed container  1  to the extent that the primary bearing  7 B is immersed in the oil  8 , the groove  261  may be formed on the step portion  270 A at the upper side, that is, on the upper surface of the cylinder  41  coming into contact with the primary bearing  7 A, thereby forming the oil path  260 . 
   One end  260 A of the oil path  260  is opened to the cylinder inner surface  49  of the low-pressure chamber side  43  A so that the oil  8  can be injected into the compression chamber  43  in connection with the suction of the refrigerant into the compression chamber  43 . Particularly, as shown in  FIG. 7 , the one end  260 A of the oil path  260  is opened at an angle in a predetermined angle range from θ 1  to θ 2  (θ 1 : 0°, θ 2 : 170°, more preferably θ 1 : 125°, θ 2 : 165°) with respect to a reference line L connecting the suction port  48  and the center point O of the cylinder  41  (about 55° in the example of  FIG. 7 ) can be further enhanced. 
   That is, since the refrigerant discharge pressure (for example, 3 MPa) is applied to the oil  8  in the hermetically sealed container  1 , by opening the one end  260 A of the oil path  260  to the cylinder inner surface of the low-pressure chamber side  43 A, the high-pressure oil  8  is passed through the oil path  260  and injected into the low-pressure chamber  43 A of the compression chamber  43  of the cylinder  43  by the differential pressure from the inner pressure (for example, 1.1 MPa) of the low-pressure chamber  43  of the compression chamber  43 . 
   Accordingly, sufficient oil film is formed between the cylinder inner surface  49  and the roller  45  by the oil  8  injected into the compression chamber  43 , and the sealing performance is enhanced by the oil film. Particularly, the oil  8  is injected into the compression chamber  43  during the suction process of the refrigerant into the compression chamber  43 , and the low-pressure chamber side  43 A and the high-pressure chamber side  43 B of the compression chamber  43  are more surely separated from each other. Therefore, in the process of compressing the refrigerant to the high-pressure chamber side  43 B (compression process), the leakage of the compressed refrigerant to the low-pressure chamber side  43 A can be prevented, and the refrigerant compression efficiency is enhanced, so that the cooling efficiency of the hermetically sealed rotary compressor  100 A can be enhanced. 
   Here, in this embodiment, by adjusting the cross-section area D of the oil path  260  opened to the cylinder inner surface  49  (that is, the cross-section area of the groove  261 ), the amount of the oil injected into the compression chamber  43  is adjusted, and at this time the cross-section area D of the oil path  260  is determined so that the ratio R (=D/V) between the cross-section area D of the oil path  260  and the displacement volume V of the compression chamber  43  falls within a predetermined range. Specifically, when the ratio R is excessively small, the oil path  260  is excessively narrow, and thus no oil  8  is injected into the compression chamber  43 . On the other hand, when the ratio R is excessively large, the oil  8  is excessively injected into the compression chamber  43 , and thus liquid compression occurs. Therefore, it is preferable that the ratio R is set to fall within the range from 0.004 to 0.03 (mm 2 /cc), whereby the sealing performance between the cylinder inner surface  49  and the roller  45  can be enhanced with preventing liquid compression due to excessive injection of the oil  8 . 
   The sealing effect based on the oil injection into the compression chamber  43  is larger when the rotary compressing element  4  is driven in a low frequency area (for example, 15 Hz to 30 Hz) and thus the differential pressure between the discharge pressure and the suction pressure is small than when the rotary compressing element  4  is driven in a high frequency area and thus rotated at a high speed. That is, by limiting the oil injection into the compression chamber  43  to the case where the differential pressure is small, the cooling efficiency can be effectively enhanced with suppressing the wasting of the oil  8  stocked in the hermetically sealed container  1 . Therefore, according to this embodiment, an opening/closing valve  280  is provided to the oil path  260 , and only when the pressure of the refrigerant compressed by the rotary compressing element  4  is relatively small, that is, the discharge pressure of the rotary compressing element  4  is small, the opening/closing valve  280  is set to the open state, so that the oil  8  is injected into the compression chamber  43 . 
   The construction of the opening/closing valve  280  will be described in detail. The cylinder  41  is provided with a cylindrical through hole  271  which penetrates through the cylinder  41  in the vertical direction (thickness direction) and traverses the oil path  260 , and the opening/closing valve  280  described above is provided in the through hole  271 . The opening/closing valve  280  comprises a substantially cylindrical valve plug  281  engagedly inserted in the through hole  271 , and a spring  282  as an urging member that is provided in the valve plug  281  and urges the valve plug  281  to the primary bearing. Under the state (open state) that valve plug  281  is pushed up to the primary bearing  7 A side by the urging force of the spring  282 , a gap occurs between the bottom portion  281 A of the valve plug  281  and the upper surface of the secondary bearing  7 B, and the oil path  260  disconnected by the through hole  271  is connected, so that the oil is injected into the compression chamber  43 . 
   Furthermore, the primary bearing  7 A is provided with a recess portion  272  in conformity with the through hole  271 . When the valve plug  281  is pushed up by the spring  282 , the upper portion  281 B of the valve plug  281  abuts against the upper surface of the recess portion  272 . One end of a compressed refrigerant introducing path  290  provided in the primary bearing  7 A is connected to the recess portion  272 , and the other end of the compressed refrigerant introducing path  290  is connected to an introducing pipe  291  which is fixed to the hermetically sealed container  1  so as to penetrate through the hermetically sealed container  1 . As shown in  FIG. 5 , a part of the compressed refrigerant discharged from the discharge pipe  13  of the hermetically sealed container  1  is led into the introducing pipe  291  through a connection pipe. Therefore, the pressure of the compressed refrigerant is applied to the upper portion  281  of the valve plug  281  through the compressed refrigerant introducing path  290 . Furthermore, when the spring constant (urging force) of the spring  282  is determined so that the valve plug  281  is pushed down when the differential pressure between the pressure of the compressed refrigerant and the suction pressure is equal to a predetermined value or more. 
   Accordingly, during the time period when the differential pressure of the compressed refrigerant is small, the valve plug  282  is pushed up to the primary bearing  7 A side by the urging force of the spring  282 , and the oil path  260  is set to a communicating state (connected state), that is, it is set to an open state. When the pressure of the compressed refrigerant is enhanced and the differential pressure of the pressure of the compressed refrigerant from the suction pressure thereof is increased, the valve plug  281  is pushed down against the urging force of the spring  282  by the pressure of the compressed refrigerant, and the oil path  260  is closed by the bottom portion  281 A of the valve plug  281 , so that the injection of the oil  8  into the compression chamber  43  is stopped. 
   Accordingly, the oil injection into the compression chamber  43  is limited to the time period when the rotary compressing element  4  is driven at a low frequency and thus the compressed refrigerant pressure is small, that is, the differential pressure between the discharge pressure and the suction pressure of the rotary compressing element  4  is small, so that the cooling efficiency can be effectively enhanced with suppressing wasting of the oil  8  stocked in the hermetically sealed container  1 . 
   As described above, according to this embodiment, the oil  8  is injected into the compression chamber  43  during the suction process of the refrigerant into the compression chamber  3  as in the case of the first embodiment. Therefore, the sufficient oil film is formed between the cylinder  41  and the roller  45  by the oil  8  injected into the compression chamber  43  and thus the sealing performance can be enhanced. Accordingly, the leakage of the refrigerant into the low-pressure chamber side  43 A during the compression process in the compression chamber  43  can be prevented, and thus the compression efficiency can be enhanced, so that the cooling efficiency of the hermetically sealed rotary compressor  100 A can be enhanced. 
   Furthermore, according to this embodiment, the ratio between the cross-section area D of the oil path  260  for injecting the oil  8  into the compression chamber  43  and the displacement volume V of the compression chamber  43  is set to be within a predetermined range, whereby the sealing performance between the cylinder inner surface  49  and the roller  45  can be enhanced with preventing the liquid compression due to excessive injection of the oil  8 . 
   Furthermore, according to this embodiment, the oil path  262  is provided with the opening/closing valve  280  that is set to the open state only when the pressure of the compressed refrigerant is small, that is, during only the time period when the rotary compressing element  4  is driven in an area where the differential pressure between the discharge pressure and suction pressure of the rotary compressing element  4  is small. Therefore, the oil injection into the compression chamber  43  is limited to the time period when the differential pressure between the discharge pressure and the suction pressure of the rotary compressing element  4  is small, and thus the cooling efficiency can be effectively enhanced with suppressing wasting of the oil  8  stocked in the hermetically sealed container  1 . 
   In this embodiment, the hermetically sealed rotary compressor  100 A having one cylinder  41  is used. However, the present invention is not limited to this type of hermetically sealed rotary compressor  100 A, and it may be applied to a hermetically sealed rotary compressor having two or more cylinders. 
   Third Embodiment 
     FIG. 9  is a diagram showing the construction of a refrigerating circuit  1200  according to an embodiment. As shown in  FIG. 9 , the refrigerating circuit  1200  (refrigerating cycle) comprises a hermetically sealed rotary compressor  100 B, a condenser  1110 , an expansion valve  1120  and an evaporator  1130  that are connected to one another in this order through a refrigerant pipe  1140 . In this refrigerating circuit  1200 , high-temperature and high-pressure gas refrigerant compressed in the hermetically sealed rotary compressor  100 B radiates heat in the condenser  1110  and is condensed and liquefied. The refrigerant thus liquefied is reduced in pressure by the expansion valve  1120 , and absorbs heat from the outside heat in the evaporator  1130  to thereby cool the surrounding of the evaporator  1130 . Thereafter, the liquefied refrigerant is stocked in an accumulator (not shown), and the gas refrigerant is returned to the hermetically sealed rotary compressor  100 B. 
     FIG. 10  is a longitudinally sectional view showing an example of the hermetically sealed rotary compressor  100 B according to this embodiment, and  FIG. 11  is an enlarged longitudinally-sectional view showing a rotary compressing element. The hermetically sealed rotary compressor  100 B constitutes a refrigerating unit by connecting a condenser and an evaporator for refrigerant to each other through a pipe. As shown in  FIG. 10 , as in the case of the first and second embodiments, the hermetically sealed rotary compressor  100 B has hermetically sealed container  1 . An electrically-driven element  2  is accommodated at the upper portion of the hermetically sealed container  1 , and a rotary compressing element  4  that is driven by the crank shaft  3  of the electrically-driven element  2  to compress the refrigerant is accommodated at the lower portion of the hermetically sealed container  1 . The basic construction of the hermetically sealed rotary compressor  100 B of this embodiment is the same as the first and second embodiments. Therefore, the same elements as the first and second embodiments are represented by the same reference numerals, and the description thereof is omitted. 
   In order to enhance the compression efficiency of the refrigerant, the hermetically sealed rotary compressor  100 B of this embodiment is equipped with an oil path  360  for injecting the oil  8  into the compression chamber  43  when the refrigerant is sucked into the compression chamber  43 . The construction of the hermetically sealed rotary compressor  100 B will be described in detail. 
   As shown in  FIG. 13 , the oil path  360  comprises a secondary oil path  361  formed in the primary bearing  7 A, and a primary oil path  362  formed in the cylinder  41 . 
   The secondary oil path  361  comprises a lateral hole extending from the outer peripheral surface of the primary bearing  7 A to the crank shaft  3  side, and a recess portion  364  connected to one end portion  363 A of the lateral hole  363  which is located at the crank shaft  3  side. 
   Furthermore, an introducing pipe  371  fixed to the hermetically sealed container  1  is connected to the other end portion  363 B of the lateral hole  363  which is located at the primary bearing  7 A side. As shown in  FIG. 10 , one end of an oil supply pipe  372  is connected to the introducing pipe  371 . The other end of the oil supply pipe  372  is connected to a lead-out pipe  373  fixed to the bottom portion of the hermetically sealed container  1 . Accordingly, the oil  8  stocked in the hermetically sealed container  1  is supplied through the oil supply pipe  372  to the secondary oil path  361 . 
   Furthermore, as shown in  FIG. 13 , the primary oil path  362  is designed as a narrow groove extending so that one end thereof intercommunicates with the opening end of the recess portion  634  formed in the primary bearing  7 A and the other end thereof intercommunicates with the compression chamber  343 , and the oil  8  introduced to the secondary oil path  361  is passed through the primary oil path  362  and led into the compression chamber  43 . In order to enable the oil  8  to be injected into the compression chamber  43  in connection with the suction of the refrigerant into the low-pressure chamber side  43 A of the compression chamber  43 , one end  362 A of the primary oil path  362  is opened to the cylinder inner surface  49  of the low-pressure chamber side  43 A as shown in  FIG. 12 . 
   That is, the refrigerant discharge pressure (for example, 3 MPa) is applied to the oil  8  in the hermetically sealed container  1 . Therefore, by opening one end  362 A of the primary oil path  362  to the cylinder inner surface  49  of the low-pressure chamber side  43 A, the high-pressure oil  8  is supplied through the oil supply pipe  372  to the oil path  360  by the differential pressure between the pressure of the high-pressure oil  8  and the inner pressure (for example, 1.1 MPa) of the low-pressure chamber side  43 A of the compression chamber  43 , and injected from the oil path  360  into the low-pressure chamber side  43 A of the compression chamber  43  of the cylinder  41 . 
   As a result, the oil  8  is injected into the compression chamber  43  in connection with the suction of the refrigerant into the compression chamber, and thus sufficient oil film is formed between the cylinder inner surface  49  and the roller  45  by the oil  8  and the sealing performance is enhanced. 
   Accordingly, the low-pressure chamber side  43 A and the high-pressure chamber side  43 B are more surely separated from each other in the compression chamber  43  of the cylinder  41 . Therefore, in the process (compression process) that the refrigerant sucked in the low-pressure chamber side  43 A is fed to the high-pressure chamber side  43 B and compressed, the leakage of the compressed refrigerant into the low-pressure chamber side  43 A is prevented, and the refrigerant compression coefficient is enhanced, so that the cooling efficiency of the hermetically sealed rotary compressor  100 B is enhanced. 
   As shown in  FIG. 12 , by forming the oil path  360  so that one end  360 A thereof is opened at an angle in a predetermined angle range from θ 1  to θ 2  (θ 1 : 0°, θ 2 : 170°, more preferably θ 1 : 125°, θ 2 : 165°) with reference to a reference line L connecting the suction port  48  and the center point O of the cylinder  41 , whereby the refrigerant compression efficiency can be further enhanced (in this example, about 125°). 
   Furthermore, according to this embodiment as in the case of the first embodiment, the cross-section area (opening area) D of the primary oil path  362  is set so that the ration R (=D/V) between the cross-section area D and the displacement volume V of the compression chamber  43  falls within a predetermined range, for example, within the range from 0.004 to 0.03 (mm 2 /cc). Accordingly, the sealing performance between the cylinder inner surface  49  and the roller  45  is enhanced with preventing liquid compression due to excessive injection of the oil  8 . 
   The effect of the sealing performance based on the oil injection into the compression chamber  43  is larger when the rotary compressing element  4  is driven in a low frequency area (for example, 15 Hz to 30 Hz) and thus the differential pressure between the discharge pressure and the suction pressure is small than when the rotary compressing element  4  is driven in a high frequency area and thus rotated at a high speed. That is, the oil injection into the compression chamber  43  is limited to the time period when the differential pressure is small, so that the cooling efficiency can be effectively enhanced with suppressing the wasting of the oil  8  stocked in the hermetically sealed container  1 . 
   Therefore, in this embodiment, the electromagnetic valve  380  is inserted in the oil supply pipe  372  as shown in  FIGS. 9 and 10 , and a controller  1150  for controlling the driving of the hermetically sealed rotary compressor  100 B controls the opening/closing operation of the electromagnetic valve  380  on the basis of the driving frequency of the rotary compressing element  4 B. The controller  1150  sets the electromagnetic valve  380  to the open state only when the electrically-driven element  2  is driven in a low frequency area (for example, 15 Hz to 30 Hz) , that is, only when the differential pressure between the discharge pressure and the suction pressure is small. 
   Accordingly, the oil injection into the compression chamber  43  is limited to only the case where the hermetically sealed rotary compressor  100 B is driven at a low frequency, that is, the differential pressure between the discharge pressure and the suction pressure of the rotary compressing element  4 B is small, and thus the cooling efficiency can be effectively enhanced with suppressing the wasting of the oil  8  stocked in the hermetically sealed container  1 . 
   As described above, according to this embodiment, as in the case of the first and second embodiments, the oil  8  is injected into the compression chamber  43  during the suction process of the refrigerant into the compression chamber  43 , so that the sufficient oil film is formed between the cylinder  41  and the roller  45  by the oil  8  injected in the compression chamber and the sealing performance is enhanced. Accordingly, the leakage of the refrigerant into the low-pressure chamber side  43 A during the compression process in the compression chamber  43  can be prevented, and thus the compression efficiency is enhanced, so that the cooling efficiency of the hermetically sealed rotary compressor  100 B can be enhanced. 
   Furthermore, according to this embodiment, the ratio between the cross-section area D of the oil path  360  for injecting the oil  8  into the compression chamber  43  and the displacement volume V of the compression chamber  43  is set to be within a predetermined range. Therefore, the sealing performance between the cylinder inner surface  49  and the roller  45  can be enhanced with preventing the liquid compression due to excessively injection of the oil  8 . 
   Furthermore, according to this embodiment, the oil supply pipe  372  is provided with the opening/closing valve  380  that is set to the open state only when the rotary compressing element  4 B is driven in a low frequency area, that is, only when the rotary compressing element  4 B is driven in an area where the differential pressure between the discharge pressure and the suction pressure of the rotary compressing element  4 B is small. Therefore, the oil injection into the compression chamber  43  is limited to the time period when the rotary compressing element  4 B is driven at a low frequency and the differential pressure is low. Therefore, the cooling efficiency can be effectively enhanced with suppressing the wasting of the oil  8  stocked in the hermetically sealed container  1 . 
   Furthermore, according to this embodiment, the high-pressure oil  8  stocked in the hermetically sealed container  1  is injected into the compression chamber  43 . However, the present invention is not limited to this embodiment, and oil of high pressure or middle pressure may be lead from the outside of the hermetically sealed rotary compressor and injected into the compression chamber  43 . Specifically, as shown in  FIG. 14 , in a refrigerating circuit  1200 ′, an oil separator  1160  for separating and withdrawing the oil from the refrigerant and returning the oil to the hermetically sealed rotary compressor  100 B′ is inserted between the discharge side of the hermetically sealed rotary compressor  100 B′ and the condenser  1110 ′, the oil separator  1160  and the oil path  360  are connected to each other through an oil supply pipe  372 ′ and a part of the oil withdrawn by the oil separator  1160  is supplied to the oil path  360 . In this case, as in the case of the above-described embodiment, an electromagnetic valve  380 ′ is provided to the oil supply pipe  372 ′, and the electromagnetic valve  380 ′ is set to the open state only when the rotary compressing element  4 B of the hermetically sealed rotary compressor  100 B′ is driven in a low frequency area, and the oil is supplied to the oil path  360 . There is a case where the oil supply pipe  372 ′ is closed by the electromagnetic valve  380 ′, and thus it is preferable that an oil return pipe is provided between the oil separator  1160  and the hermetically sealed rotary compressor  100 B′ separately from the oil supply pipe  372 ′ in order to stably return the oil withdrawn by the oil separator  1160  to the hermetically sealed rotary compressor  100 B′. Furthermore, the oil led from the oil separator  1160  is kept to be under high pressure, and thus it is preferable that a pressure-reducing unit such as a capillary tube  1170  (may be expansion valve) or the like is provided between the oil separator  1160  and the electromagnetic valve  380 ′ to reduce and adjust the pressure of the oil and supply the pressure-adjusted oil to the oil path  360 . 
   Furthermore, according to this embodiment, the hermetically sealed rotary compressor  100 B is equipped with one cylinder  41 . However, the present invention is not limited to this embodiment, and the present invention may be applied to a hermetically sealed rotary compressor having two or more cylinders.