Patent Publication Number: US-6336336-B1

Title: Rotary piston compressor and refrigerating equipment

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a rotary piston compressor and refrigerating equipment; and, more particularly, the invention is directed to a rotary piston compressor in which a rotor and a vane are unitarily formed, and to refrigerating equipment using the rotary piston compressor, such as an air conditioner, a refrigerator, and a refrigerating device. 
     A conventional rotary piston compressor is provided with a cylinder which forms a cylinder chamber and a bushing housing chamber communicating with this cylinder chamber, a piston disposed in the cylinder chamber, and a rotary bushing disposed in the bushing housing chamber. The piston unitarily has a roller which rotates in the cylinder chamber, and a vane which, together with the roller, divides the interior of the cylinder chamber into a suction chamber and a compression chamber. 
     The vane is extended into the bushing housing chamber, so that the rotary bushing is divided into a rotary bushing on the compression chamber side and another rotary bushing on the suction chamber side on both sides of the vane. 
     In the rotary piston compressor, the rotary bushing rotates in the bushing housing chamber with the rotation of the roller to absorb rotation and axial motion of the vane, thereby increasing the volume of the suction chamber and decreasing the volume of the compression chamber. In this manner the refrigerant is drawn into the suction chamber and compressed in the compression chamber, being discharged out of the cylinder. 
     A prior art rotary piston compressor has been disclosed in, for instance, JP-A No. H7-158574. 
     The prior art rotary piston compressor, however, has a drawback in that, when drawn into the cylinder chamber immediately after starting, a liquid refrigerant or a wet refrigerant is subject to volume expansion the instant when the refrigerant is drawn into the cylinder chamber, or to volume contraction when the refrigerant is still in an almost liquid state. Since, in this case, the rotary piston roller and vane are unitarily formed, the refrigerant is likely to be excessively compressed. 
     Therefore, it has been proposed to form a dead space communicating with the compression chamber, whereby transient overcompression occurring at the time of starting will be alleviated. However, during routine operation, the presence of the dead space allows a high-pressure gas to remain within the cylinder chamber after the end of the discharge stroke, causing re-expansion of the refrigerant in the following stroke and accordingly resulting in a pressure loss at the time of suction and a lowering of the refrigerating capacity. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of this invention to provide a reliable, high-performance rotary piston compressor and refrigerating equipment which are of a simple configuration and are capable of preventing overcompression without deterioration of performance during routine operation, and which are also capable of preventing re-expansion of the refrigerant after the completion of the discharge process. 
     For attaining the above-described object, according to a first feature of this invention, a rotary piston compressor is provided with a cylinder which forms a cylinder chamber and a bushing housing chamber communicating with this cylinder chamber, a piston disposed in the cylinder chamber, and a rotary bushing disposed in the bushing housing chamber. The piston is unitarily formed with a roller which rotates in the cylinder chamber, and a vane which, together with the roller, divides the interior of the cylinder chamber into a suction chamber and a compression chamber. The vane is extended into the bushing housing chamber, so that the rotary bushing is separated into a rotary bushing on the compression chamber side and another rotary bushing on the suction chamber side on both sides of the vane. The rotary bushing on the compression chamber side is disposed so as to move away from the cylinder chamber when the compression chamber pressure has been not less than a specific pressure, and also to move toward the cylinder chamber when the compression chamber pressure has decreased to not more than a specific pressure. With the movement of the rotary bushing on the compression chamber side, a communicating passage for communication between the compression chamber and the space on the discharge side outside of the cylinder is opened and closed. 
     According to a second feature of this invention, the rotary bushing on the compression chamber side has a portion facing the compression chamber and a portion facing the high discharge pressure side, and is so arranged as to move away from the cylinder chamber when the resultant of the load applied to the portion facing the compression chamber and the load applied to the portion facing the high discharge pressure side is not less than the specific value, and to move toward the cylinder chamber when the resultant has decreased to not more than the specific value. The communicating passage for communication between the compression chamber and the space on the discharge side outside of the cylinder therefore is opened and closed with the movement of the rotary bushing on the compression chamber side. 
     According to a third feature of this invention, the rotary piston compressor is provided with a cylinder including a cylinder chamber, a bushing housing chamber connected to the cylinder chamber, and a oil-supply pump chamber connected to the bushing housing chamber. The oil-supply pump chamber communicates with the high discharge pressure side; the vane is extended from the bushing housing chamber to the oil-supply pump chamber, which therefore is provided with the pumping function by the motion of the vane; the rotary bushing on the compression chamber side has a portion facing the compression chamber and a portion facing the oil-supply pump chamber, and moves away from the cylinder chamber when the resultant of the load applied to the portion facing the compression chamber and the load applied to the portion facing the oil-supply pump chamber is not less than a specific value, and moves toward the cylinder chamber when the resultant has decreased to not more than the specific value. 
     According to a fourth feature of this invention, the compression chamber side of the bushing housing bore which forms the cylinder chamber is comprised of a circular portion on the cylinder chamber side, an intermediate straight portion, and a circular portion on the opposite side of the cylinder chamber as viewed from the vicinity of the cylinder chamber. 
     According to a fifth feature of this invention, the bushing housing bore defining the cylinder chamber asymmetrically forms the suction chamber side and the compression chamber side. The rotary bushing on the suction chamber side is so formed as to have approximately the same external semicircular shape as the semicircular portion on the suction chamber side of the bushing housing bore. 
     A sixth feature of this invention resides in the fact that the intermediate straight portion spreads outward. 
     A seventh feature of this invention resides in the fact that the rotary bushing on the compression chamber side moves away from the cylinder chamber when the compression chamber pressure has been not less than the specific pressure in the discharge stroke of the compressor, and moves toward the cylinder chamber when the compression chamber pressure has lowered to not more than the specific pressure after the completion of the discharge process of the compressor. 
     An eighth feature of this invention resides in the fact that a refrigerating cycle is formed by connecting a rotary piston compressor, a condenser, a pressure reducing device, an evaporator, and a receiver tank by means of a piping. The rotary piston compressor is provided with a cylinder which forms a cylinder chamber and a bushing housing chamber communicating with this cylinder chamber, a piston disposed in the cylinder chamber, and a rotary bushing disposed in the bushing housing chamber. The piston unitarily has a roller which rotates in the cylinder chamber, and a vane which, together with the roller, divides the interior of the cylinder chamber into a suction chamber and a compression chamber. The suction chamber is connected to a piping from the receiver tank. The vane is extended into the bushing housing chamber. The rotary bushing is so arranged as to be separated into a rotary bushing on the compression chamber side and another rotary bushing on the suction chamber side on both sides of the vane. Furthermore, the rotary bushing has a portion facing the compression chamber and a portion facing the high discharge pressure side, and is so arranged as to move away from the cylinder chamber when the resultant of the load applied to the portion facing the compression chamber and the load applied to the portion facing the high discharge pressure side has been not less than a specific value, and to move toward the cylinder chamber when the resultant has decreased to not more than the specific value. The communicating passage for providing communication between the compression chamber and the space on the discharge side outside of the cylinder therefore is opened and closed with the movement of the rotary bushing on the compression chamber side. 
     According to a ninth feature of this invention, a refrigerating cycle is formed by connecting a rotary piston compressor, a condenser, a pressure reducing device, an evaporator, and a receiver tank by means of a piping. The rotary piston compressor is provided with a cylinder which forms a cylinder chamber and a bushing housing chamber communicating with this cylinder chamber, a piston disposed in the cylinder chamber, and a rotary bushing disposed in the bushing housing chamber. The compression chamber side of the bushing housing bore defining the cylinder chamber is comprised of a circular portion on the cylinder chamber side, an intermediate straight portion, and a circular portion on the opposite side of the cylinder chamber as viewed from the vicinity of the cylinder chamber; the intermediate straight portion being designed to spread outward. 
     Other objects, features and advantages of this invention will be apparent from the following detailed description taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view of a first embodiment of a rotary piston compressor according to this invention; 
     FIG. 2 is a sectional view taken on line A—A of a rotary piston compressor cylinder of FIG. 1; 
     FIG. 3 is a sectional view taken on line A—A of a compression mechanism section of the rotary piston compressor of FIG. 1 during routine operation; 
     FIG. 4 is a sectional view taken on line A—A of the compression mechanism section of the rotary piston compressor of FIG. 1 during overcompression operation; 
     FIG. 5 is an operating flow diagram of the sequence of operation of the rotary piston compressor of FIG. 1; 
     FIG. 6 is a refrigerating cycle diagram of the refrigerating equipment using the rotary piston compressor of FIG. 1; 
     FIG. 7 is a diagram of a second embodiment of the compression mechanism of the rotary piston compressor according to this invention; and 
     FIG. 8 is an operation flow diagram of the sequence of operation of the rotary piston compressor of FIG.  7 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Each embodiment of this invention will hereinafter be described with reference to the accompanying drawings. 
     In FIG. 1, a closed vessel  1  is comprised of a long, cylindrical body section  1   a  and cover sections  1   b  and  1   c  on respective ends thereof. In the closed vessel  1  an electric motor section  2 , a compression mechanism section  3 , and a crankshaft  4  are housed. 
     The electric motor section  2  has a stator  2   a  and a rotor  2   b,  the stator  2   a  being firmly attached on one side in the closed vessel  1 , and the rotor  2   b  being rotatably installed within the stator  2   a.    
     The compression mechanism section  3  has two cylinders  5 , end plates  61  and  62  on both sides, an intermediate end plate  63 , two pistons  7 , and two rotary bushings  8 . The piston  7  includes a roller  7   a  and a vane  7   b,  which are formed as one unit, as seen in FIG.  3 . The compression mechanism section  3  is secured on the other side inside of the closed vessel  1  through the end plate  61 . 
     The two cylinders  5  have a cylindrical inner peripheral surface  5   a,  as seen in FIG.  2 . Between the two cylinders the end plate  63  is interposed. The end plates  61  and  62  are disposed on both sides of the two cylinders, thereby forming two spaces as a cylinder chamber  11  surrounded by these end plates  61  and  62 . The cylinder  5  is formed adjacent to a cutout suction groove  10  and a cutout discharge groove  12  connected to the cylinder chamber  11 . The cutout discharge groove  12  is connected to a discharge port  13  formed in the end plates  61  and  62 . 
     The cylinder  5  is provided with a bushing housing bore  5   b  ( 5   b   1 ,  5   b   2 ,  5   b   3 ) which forms a bushing housing chamber  21  communicating with the cylinder chamber  11 , and, furthermore, with a pump bore  5   c  which forms an oil-supply pump chamber  22  communicating with the bushing housing chamber  21 . 
     Both sides of the bushing housing bore  5   b,  as is clear from FIG. 2, are asymmetrical. The compression chamber side of the bushing housing bore  5   b  is formed of a circular portion  5   b   1  on the cylinder chamber side, a intermediate straight portion  5   b   2 , and a circular portion  5   b   3  on the opposite side of the cylinder chamber, as viewed from the vicinity of the cylinder chamber  11 . The other suction chamber side is formed to be semicircular. The intermediate straight portion  5   b   3  is formed to a specific size L. 
     The bushing housing chamber  21  communicates with a high-pressure space in the closed vessel outside of the cylinder  5  through a communicating passage  23 . The communicating passage  23  is so formed as to open to one part of the circular portion  5   b   1  on the cylinder chamber side of the bushing housing bore  5   b.  The communicating passage, in the present embodiment, is formed in the cylinder  5 , but may be formed in the opposite end plates  61 ,  62  and  63 . 
     The crankshaft  4  is fixedly attached on one side to the rotor  2   b  of the electric motor section  2  and on the other side to the compression mechanism section  3 , being rotatably supported on bearings mounted on the end plates  61  and  62 . The crankshaft  4  is provided with two off-center portions  4   a  formed and positioned within two rollers  7   a  of the piston  7 . The crankshaft  4  has an oil feed hole  4   b  formed through the central portion thereof The rotor  2   b  rotates as electrical power is supplied to the stator  2   a  of the electric motor  2 , thereby turning the crankshaft  4  and, accordingly, eccentrically turning the two off-center portions  4   a  of the crankshaft  4  within the two rollers  7   a.    
     Thus, the rotor  7   a  rotates within the cylinder  5  as shown in FIG.  5 . 
     The vane  7   b  unitarily formed on the roller  7   a  is supported on the rotary bushing  8  in such a manner that, with the revolution of the roller  7   a  as shown in FIG. 5, it can move back and forth within the cylinder chamber  11  while rotating at the angle of rotation a in relation to the centerline. The vane  7   b  is disposed between the cutout suction groove  10  and the cutout discharge groove  12  so that the cylinder chamber  11  is divided into the suction chamber  11   a  and the compression chamber  11   b.  Furthermore, the vane  7   b  thus disposed is extended from the bushing housing chamber  21  to the oil-supply pump chamber  22 . 
     As shown in FIGS. 3 and 4, the rotary bushing  8  is separated into a rotary bushing  8   a  on the suction chamber side and a rotary bushing  8   b  on the compression chamber side, which are mounted on both sides of the vane  7   b  in the bushing housing bore  5   b.  These rotary bushings are formed in a semicircular form comprising a semicircular portion and a straight portion. The outside diameter of the semicircular portion of the rotary bushing  8  is a very little smaller than the inside diameter of the circular portion  5   b   1  and the semicircular portion  5   b   4  on the cylinder chamber side of the bushing housing bore  5   b  and, to be more specific, is set to a size which allows the formation of a very narrow clearance for the formation of an oil film between the rotary bushing  8  and the bushing housing bore  5   b.  The rotary bushing  8   b  on the compression chamber side is so arranged as to be movable by the size of the intermediate straight portion  5   b   2 . The rotary bushing  8  is mounted in such a manner as to partly face the suction chamber  11   a  and the compression chamber  11   b.    
     With the revolution of the roller  7   a  as previously stated, the roller  7   a,  the vane  7   b  and the rotary bushing  8 , in the routine operation, change their positions from the state (a) to the state (d) in FIG.  5 . Each of these states will be explained. When the crank angle is 0° (360°), the state (a) indicates the beginning of suction and the completion of discharge; that is, at the rotation angle α of 0°, the vane  7   b  is fully withdrawn from the cylinder chamber  11  and fully projects into the oil-supply pump chamber  22 . When the roller  7   a  rotates from this state, the volume of the suction chamber  11   a  increases, while the volume of the compression chamber  11   b  decreases. In the state (b) at the crank angle of 90°, the rotation angle α is at a maximum, at which the amount of projection of the vane  7   b  into the cylinder chamber  11  increases and the amount of projection of the vane  7   b  into the oil-supply pump chamber  22  decreases. When the roller  7   b  rotates further from this state until the crank angle becomes 180° into the state (c), the rotation angle α decreases to 0, at which the vane  7   b  fully projects into the cylinder chamber  11  and is fully withdrawn from the oil-supply pump chamber. As the roller  7   a  rotates further from this state to the state (d) at the crank angle of 270°, the rotation angle α reaches a maximum on the opposite side, at which the amount of projection of the vane  7   b  into the cylinder chamber  11  decreases, while the amount of projection into the oil-supply pump chamber  22  increases. The roller  7   a  further rotates from this position, back to the initial state (a), thereafter repeating the above-described operation. 
     The position of the rotary bushing  8   b  on the compression chamber side is determined by the resultant of load applied to a portion facing the compression chamber  11   b  and the oil-supply pump chamber  22 . In a routine operation, the resultant is applied toward the cylinder chamber at all crank angles until the rotary bushing  8   b  is pressed into contact with the circular portion  5   b   1  on the cylinder chamber side, whereby the communicating passage  23  is closed with the rotary bushing  8 . The oil-supply pump chamber  21  is located at the lower part within the closed vessel  1 , and is extended to the refrigerating machine oil held at the lower part within the closed vessel  1  through a fluid diode. In this oil-supply pump chamber  21 , the vane  7   b  rotates in and out as shown in FIG. 5, thereby allowing the refrigerating machine oil to flow from the closed vessel  1  into the oil-supply pump chamber  21  through the fluid diode, and further to be supplied to each sliding part of the compression mechanism section to lubricate the sliding part. 
     A suction pipe  9  and a discharge pipe  15  are installed through the closed vessel  1 , being connected on one side to an external refrigerating cycle. The suction pipe  9  is connected on the other side to a cutout suction groove  10 . The discharge pipe  15  is connected on the other side to a high-pressure space in the closed vessel. The refrigerant gas that has been drawn from the suction pipe  9  flows out of the suction portion of the end plates  61  and  62 , being drawn into the cylinder chamber  11  through the cutout suction groove  10  of the cylinder  5 . The refrigerant thus drawn in is compressed with a change in the volume of the compression chamber  11 , as is clear from FIG. 5, then flows through the cutout discharge groove  12  of the cylinder  5  to push up the discharge valve  14  from the discharge port  13  of the end plates  61  and  62 , being discharged into the first discharge silencer  71 . The high-pressure refrigerant thus discharged passes through the second silencer  72 , being discharged into the space in the closed vessel  1 . The refrigerant gas in the closed vessel  1  is discharged from the discharge pipe  15  out to the external refrigerating cycle. 
     The refrigerating cycle is comprised of a rotary piston compressor  30 , a condenser  31 , a pressure reducing device  32  including a capillary tube, an evaporator  33 , and a receiver tank  34 , which are connected by a piping  35 , as shown in FIG.  6 . In the present embodiment, the refrigerating equipment using this refrigerating cycle is a refrigerator. 
     When the refrigerating cycle is operated, the refrigerant in the refrigerating cycle is compressed to a high-pressure gas in the rotary piston compressor  30 , from which the high-pressure gas goes into the condenser  31 . In the condenser  31  the high-pressure gas is cooled and returned to its liquid state, flowing into the pressure reducing device  32 , where the pressure of the liquid refrigerant is reduced to a low pressure. The low-pressure refrigerant reaches the evaporator  33 , where the refrigerant is vaporized to draw heat from the surrounding atmosphere, then it goes into the receiver tank  34 . The refrigerant, after separation of liquid in the receiver tank  34 , returns to the rotary piston compressor  30 , thus completing a specific cooling operation. 
     Then, after the refrigerating cycle operation is stopped, the refrigerant in the evaporator  33  returns to a liquid and is held therein because the evaporator  33  is at a low temperature. Therefore, when the refrigerating cycle operation is restarted, a transient phenomenon takes place such that the liquid refrigerant or the wet refrigerant is drawn into the rotary piston compressor  30  during the starting operation of the rotary piston compressor  30  immediately after restarting. 
     Operation of the rotary piston compressor  30  during the starting operation will now be explained. 
     When the rotary piston compressor  30  is started, the rotor  7   a  rotates to draw in the liquid refrigerant or the wet refrigerant, which is subsequently compressed. In the compression process, a low-pressure refrigerant thus drawn in is compressed, thereby increasing the refrigerant pressure in the compression chamber  11   b.  When the pressure of the thus compressed refrigerant has reached the pressure in the space in the closed vessel  1 , the discharge valve  14  is opened to connect the compression chamber  11   b  to the space in the closed vessel  1  on the outside of the cylinder  5 . Furthermore, in the compression process, the resultant load being applied to the portion facing the oil-supply pump chamber  22  and the compression chamber  11   b  of the rotary bushing  8   b  on the compression chamber side has been set so as to be applied toward the cylinder chamber, so that the rotary bushing  8   b  on the compression chamber side will be pressed into contact with the circular portion  5   b   1  on the cylinder chamber side. 
     The communicating passage  23 , therefore, is closed by the rotary bushing  8   b  on the compression chamber side. When the resultant of the load applied to the portion facing the compression chamber  11   b  of the rotary bushing  8   b  on the compression chamber side and the load applied to the portion facing the oil-supply pump chamber  22  is not less than a specific value, the rotary bushing  8   b  on the compression chamber side moves toward the opposite side of the cylinder chamber. Also, when the resultant of the load has decreased not more than a specific value, the rotary bushing  8   b  on the compression chamber side moves toward the cylinder chamber. It is therefore possible to reliably prevent over-compression by using the pressure of the oil-supply pump chamber  22 . 
     Furthermore, the rotor  7   a  rotates to perform the discharge process. In this case, when the pressure of the compression chamber  11   b  has increased over a specific value, the resultant of load applied to the portion facing the oil-supply pump chamber  22  and the compression chamber  11   b  of the rotary bushing  8   b  on the compression chamber side is so set as to be exerted toward the opposite side of the cylinder chamber. The rotary bushing  8   b  on the compression chamber side is moved into contact with the circular portion  5   b   3  on the opposite side of the cylinder chamber, so that the communicating passage  23  is opened by the rotary bushing  8   b  on the compression chamber side. Therefore, the compression chamber  11   b  communicates with the space in the closed vessel  1  through the communicating passage  23 ; and, the refrigerant in the compression chamber  11  is discharged into the space in the closed vessel  1  through the communicating passage  23 , thereby preventing over-compression which is likely to be caused by the compression of the liquid refrigerant or the wet refrigerant, thereby improving the reliability of the rotary piston compressor. 
     When the compressor operation returns to the compression stroke after the discharge process, the pressure in the compression chamber  11   b  lowers as low as the suction pressure; therefore, the resultant of load being applied to the portion facing the oil-supply pump chamber  22  and the compression chamber  11   b  of the rotary bushing  8   b  on the compression chamber side is applied toward the cylinder chamber. Thus, the bushing  8   b  on the compression chamber side is pressed into contact with the circular portion  5   b   1  on the cylinder chamber side, to thereby close the communicating passage  23 . Therefore, when the operation returns from the discharge stroke to the compression stroke, it is possible to prevent the refrigerant in the space in the closed vessel  1  from returning to the compression chamber  11  through the communicating passage  23  and accordingly to prevent the lowering of the refrigerating capacity. 
     In the rotary piston compressor  30  described above, the bushing housing bore  5   b  which defines the cylinder chamber  11  is comprised, on the compression chamber side, of the circular portion  5   b   1  on the cylinder chamber side, the intermediate straight portion  5   b   2 , and the circular portion  5   b   3  on the opposite side of the cylinder chamber, as viewed from the vicinity of the cylinder chamber  11 . Therefore, it is possible to smoothly move the rotary bushing  5   b   3  of a simple shape on the opposite side of the cylinder chamber through the intermediate straight portion  5   b   2 . 
     In the refrigerating equipment using the above-described rotary piston compressor  30  for the refrigeration cycle, the receiver tank  34  can be downsized. 
     Next, a second embodiment of this invention will be explained with reference to FIGS. 7 and 8. FIG. 7 is an explanatory view of the compression mechanism section of the rotary piston compressor of the second embodiment according to this invention; and FIG. 8 is an explanatory view of operation of the rotary piston compressor of FIG.  7 . In the description of the second embodiment, the configuration of members common to those of the first embodiment will not be described in order to prevent redundancy. 
     The second embodiment differs from the first embodiment in the respect that, as is clear from FIG. 7, the intermediate straight portion  5   b   2  on the compression chamber side of the bushing housing bore  5   b  is formed to spread outward so as to be approximately parallel with the vane  7   b  at the maximum rotation angle α. In other respects, there is no difference between the second embodiment and the first embodiment. 
     According to the configuration described above in the second embodiment, the rotary piston compressor of the second embodiment has the same advantage as that of the first embodiment, and can be so set as to move the rotary bushing  8   b  on the compression chamber side even at the crank angle of 180° or less. 
     It should be noticed that, in the above-described embodiment, the rotary bushing  8   b  on the compression chamber side is so configured as to face the oil-supply pump chamber  22 , but the invention is not limited thereto. 
     According to this invention, the rotary bushing of a simple configuration can prevent over-compression of a refrigerant without deteriorating compressor performance during routine operation, and also can prevent re-expansion of the refrigerant after completion of the discharge process. It is therefore possible to provide a high-reliability, high-performance rotary piston compressor and refrigerating equipment. 
     Furthermore, according to this invention, it is possible to obtain refrigerating equipment incorporating a high-reliability, high-performance rotary piston compressor and a small-sized receiver tank.