Patent Publication Number: US-6336800-B1

Title: Rotary compressor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to rotary compressors and, more particularly, to a rotary compressor of the low operational noise type, having a bypass passage on the internal surface of its cylinder at a position around a fluid exhaust stroke initiating point to effectively reduce excessive pressure pulsation generated at the initial stage of an exhaust stroke, thus effectively reducing impact exciting force caused by the pressure pulsation within the compression chamber of the cylinder and effectively reducing pulsation noise having a wide frequency band. 
     2. Description of the Prior Art 
     As well known to those skilled in the art, compressors are machines used for compressing fluid, such as liquid or gas, to a desired pressure and have been preferably and widely used for a variety of applications. Such compressors are recognized as very important elements in a variety of refrigeration systems, such as air conditioners or refrigerators, since the compressors are used for compressing refrigerant of refrigeration cycles and determine the operational capacities and operational efficiencies of such refrigeration systems. Conventional compressors have been classified into two types: rotary compressors and scroll compressors. Of the two types, the scroll compressors are designed to compress refrigerant by a rotating action of a rotatable scroll, operated in conjunction with a drive unit, relative to a fixed scroll. On the other hand, the rotary compressors compress refrigerant by a roller, which is operated in conjunction with a drive unit and is eccentrically rotated within the bore of a cylinder. 
     FIGS. 1 and 2 show the construction of a conventional rotary compressor. As shown in the drawings, the conventional rotary compressor comprises a casing  10  provided with both a refrigerant inlet port  10   a  for introducing refrigerant into the casing  10  and a refrigerant outlet port  10   b  for discharging compressed refrigerant from the casing  10 . A stator  11  is fixed within the casing  10 , while a rotor  12  is positioned to be electromagnetically rotatable relative to the stator  11  when it is electrically activated. A rotating shaft  13  having an eccentric portion ( 13 ′) is integrated with the central axis of the rotor  12  and is rotatable along with the rotor  12 . A roller  17  is fixed to the eccentric portion ( 13 ′) of the rotating shaft  13  and set within the bore  16   a  of a cylinder  16 . The cylinder  16  has a suction port  21  and an exhaust port  22  and compresses working fluid, sucked into the bore  16   a  through the suction port  21 , in accordance with an eccentric rotating action of the roller  17  within the bore  16   a  and discharges the compressed fluid from the bore  16   a  through the exhaust port  22 . 
     A vane  18  is provided within the bore  16   a  of the cylinder  16  at a position around the exhaust port  22  and is normally biased by a spring  19  so as to elastically come into contact with the external surface of the roller  17 . The above vane  18  partitions the chamber, formed between the cylinder  16  and the roller  17 , into a variable suction chamber  16   b  and a variable compression chamber  16   c . An exhaust control valve (not shown) is provided within the exhaust port  22  of the cylinder  16  and is used for controlling the port  22  so as to allow the port  22  to exhaust the compressed fluid from the cylinder  16  when the roller  17  completely rotates within the cylinder  16  at a predetermined angle. A main bearing  14  is installed at an upper position within the cylinder  16 , while a sub-bearing  15  is installed at a lower position within the cylinder  16 . 
     The above conventional rotary compressor is operated as follows: That is, when the compressor is electrically activated, the rotor  12  is electromagnetically rotated along with the rotating shaft  13  relative to the stator  11 . Therefore, the roller  17  is eccentrically rotated within the cylinder bore  16   a  while coming into tangential contact with the internal surface of the cylinder  16 . When the roller  17  is eccentrically rotated within the cylinder bore  16   a , refrigerant is introduced into the bore  16   a  through the suction port  21 . The refrigerant is thus gradually compressed as the compression chamber  16   c , formed by the roller  17 , the internal surface of the cylinder  16  and the vane  18 , is gradually reduced in its volume due to the eccentric rotating action of the roller  17  within the cylinder bore  16   a . When the pressure of the refrigerant reaches a predetermined reference level as it is compressed, the exhaust control valve is opened, thus allowing the compressed refrigerant to be exhausted from the cylinder  16  through the exhaust port  22 . The exhausted compressed air is, thereafter, discharged from the compressor through the refrigerant outlet port  10   b  formed on the casing  10  of the compressor. 
     In the drawings, the reference numeral  20  denotes an accumulator. 
     FIG. 3 is a sectional view corresponding to FIG. 2, showing a resonator installed within the cylinder of the conventional rotary compressor. As shown in the drawing, a resonator  40 , designed to reduce operational noise of a predetermined frequency band, is formed in the cylinder  16  to communicate with the exhaust port  22 . Due to the resonator  40 , the compressor reduces pulsation noise, caused by refrigerant gas within the cylinder  16  during a refrigerant compression stroke of the cylinder  16 . The resonator  40  also prevents an undesirable quick discharging of the pressure pulsation from the cylinder  16  during a refrigerant exhaust stroke of the cylinder  16 , thus reducing operational noise and vibration during the refrigerant exhaust stroke. The resonator  40  is determined in its resonating frequency band in accordance with both the shape of a resonating cavity determined by the acoustic resonance and the shape of a pressure leading passage. 
     Since both the shape of the resonating cavity and the shape of the pressure leading passage are fixed, the resonating frequency band of the resonator  40  for the cylinder  16  is fixed. However, since the compression chamber  16   c  is gradually reduced in its volume in a refrigerant compression stroke, the internal pressure of the compression chamber  16   c  continuously varies, with the pressure pulsation being exhausted from the cylinder  16  through the exhaust port  22 . Therefore, the compressor inevitably generates operational noises having a variety of frequency bands, and so the resonator  40 , having a fixed resonating frequency band, does not desirably reduce the pressure pulsation in the compressor. 
     In addition, lubrication oil may be undesirably introduced from the cylinder bore  16   a  into the resonating cavity of the resonator  40  at the initial stage of the operation of the compressor. In such a case, it is almost impossible to effectively remove the lubrication oil from the resonator  40  during the operation of the compressor since the pressure leading passage of the resonator  40  is positioned above the resonating cavity. The amount of lubrication oil, remaining in the resonating cavity, varies during the operation of the compressor, and changes the noise reduction characteristics of the resonator  40 . Therefore, the resonator  40  does not maintain its designed noise reductirefrigeranton characteristics and fails to accomplish its desired noise reducing operational effect. 
     In addition, since the resonator  40  is formed on the middle portion of the exhaust line while communicating with the exhaust port  22 , the quantity of refrigerant, which is undesirably remained in the compression chamber  16   c  at the final stage of a compressed refrigerant exhaust stroke and is free from exhausting compressed refrigerant from the cylinder  16 , is undesirably increased. Therefore, the highly compressed refrigerant gas, remaining in the dead cavity, is undesirably fed back to the suction chamber  16   b  of the cylinder bore  16   a  after the exhaust stroke, thus causing a re-expansion of completely compressed refrigerant and deteriorating the compression efficiency of the compressor. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a rotary compressor of the low operational noise type, which has a bypass passage on the internal surface of its cylinder at a position around a fluid exhaust stroke initiating point to effectively reduce excessive pressure pulsation generated at the initial stage of each exhaust stroke, thus effectively reducing impact exciting force caused by the pressure pulsation within the compression chamber of the cylinder and effectively reducing pulsation noise having a wide frequency band. 
     In order to accomplish the above object, the present invention provides a rotary compressor comprising a casing, a rotating shaft set within the casing, a roller eccentrically fixed to the rotating shaft and eccentrically, rotatably set within a cylinder so as to form a variable suction chamber and a variable compression chamber within the cylinder, further comprising a bypass passage formed on the internal surface of the cylinder at a position around the refrigerant exhaust stroke initiating point, thus allowing the compression and exhaust chambers to communicate with each other through the bypass passage at the initial stage of each exhaust stroke. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a sectional view, showing the construction of a conventional rotary compressor; 
     FIG. 2 is a sectional view, showing the cylinder and the eccentric roller of the conventional rotary compressor; 
     FIG. 3 is a sectional view corresponding to FIG. 2, showing a resonator installed within the cylinder of the conventional rotary compressor; 
     FIG. 4 is a sectional view, showing the cylinder and the eccentric roller of a rotary compressor in accordance with the preferred embodiment of the present invention; 
     FIG. 5 is a sectional view of the rotary compressor of this invention, showing a flow of refrigerant within the cylinder provided with a bypass passage; 
     FIG. 6 is a graph, showing pressure as a function of rotating angle of the eccentric roller within the cylinder of the rotary compressor according to this invention in comparison with a conventional rotary compressor; and 
     FIG. 7 is a waveform diagram, showing operational noise as a function of frequency of the rotary compressor according to the present invention in comparison with a conventional rotary compressor. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION. 
     FIG. 4 is a sectional view, showing the cylinder and the eccentric roller of a rotary compressor in accordance with the preferred embodiment of the present invention. FIG. 5 is a sectional view of the rotary compressor of this invention, showing a flow of refrigerant within the cylinder provided with a bypass passage. 
     As shown in the drawings, the general shape of the rotary compressor according to the preferred embodiment of this invention remains the same as that of the conventional rotary compressor of FIG. 1, but a bypass passage  60  is formed on the internal surface of the cylinder  16  at a position around a refrigerant exhaust stroke initiating point spaced apart from the vane  18  at a counterclockwise angle θ. 
     That is, the rotary compressor according to the preferred embodiment of this invention comprises a casing  10  provided with the cylinder  16  therein. The cylinder  16  defines a bore  16   a  therein, with both a refrigerant suction port  21  and a refrigerant exhaust port  22  being formed on the cylinder  16 . An eccentric roller  17 , eccentrically fixed to the rotating shaft  13  of a rotor  12 , is set within the cylinder bore  16   a . This roller  17  is eccentrically rotated within the bore  16   a  and compresses refrigerant. A vane  18  is provided within the cylinder bore  16   a  while being normally biased by a spring  1 p to elastically come into contact with the external surface of the roller  17 . This vane  18  thus partitions the chamber, formed between the cylinder  16  and the roller  17 , into a low pressure variable suction chamber  16   b  and a high pressure variable compression chamber  16   c . The bypass passage  60  is formed by a groove, which is formed on the internal surface of the cylinder  16  at a position around the refrigerant exhaust stroke initiating point spaced apart from the spring-biased vane  18  at a counterclockwise angle θ. In the present invention, it is preferable to design the groove of the bypass passage  60  to have a depth of not larger than 20% of the height of the cylinder  16 . At the refrigerant exhaust stroke initiating point, the roller  17  completely compresses the refrigerant within the compression chamber  16   c  and initially exhausts the compressed refrigerant from the cylinder  16  through the exhaust port  22  that is opened by an exhaust control valve (not shown). 
     In the present invention, the bypass passage  60  may be provided in the upper portion of the cylinder  16  around the main bearing  14  or in the lower portion of the cylinder  16  around the sub-bearing  15 . Alternatively, two bypass passages  60  may be formed in the upper and lower portions of the cylinder  16 . 
     In addition, the bypass passage  60  may be preferably formed on the internal surface of the cylinder  16  at a position within an area having a range of θ ± 10°. 
     In the rotary compressor of this invention, the refrigerant suction and exhaust strokes are alternately and periodically performed under the control of the exhaust control valve, which periodically opens and closes the exhaust port  22  of the compression chamber  16   c . That is, the exhaust control valve opens the exhaust port  22  at a time the internal pressure of the compression chamber  16   c  becomes higher than the exhaust pressure, thus quickly discharging pressure pulsation from the compression chamber  16   c  into the interior of the compressor casing  10 . In such a case, the compressor typically generates impact vibration and pulsation noise. However, the compressor of this invention has the bypass passage  60  on the internal surface of the cylinder  16  at a position around the refrigerant exhaust stroke initiating point spaced apart from the spring-biased vane  18  at the angle θ. Therefore, at the exhaust stroke initiating point, the remaining highly compressed refrigerant gas is fed back from the compression chamber  16   c  into the suction chamber  16   b  through the bypass passage  60 , thus reducing the pressure pulsation. That is, at a time the roller  17  passes by the exhaust stroke initiating point of the angle θ with the exhaust control valve being opened, the high pressure compression chamber  16   c  communicates with the low pressure suction chamber  16   b  through the bypass passage  60 . Therefore, the pressure pulsation of the highly compressed refrigerant gas is discharged from the compression chamber  16   c  into the low pressure suction chamber  16   b , thus preventing a rapid pressure variation at a time the exhaust control valve is opened. Therefore, it is possible to prevent an undesired excessive compression of refrigerant gas at the initial stage of each exhaust stroke. This finally reduces both impact vibration and pulsation noise caused by such an excessive pressure variation. 
     In such a case, the refrigerant compression efficiency of the compressor may be undesirably reduced since the highly compressed refrigerant gas is fed from the compression chamber  16   c  back into the suction chamber  16   b  through the bypass passage  60 . However, such a communication of the compression chamber  16   c  with the suction chamber  16   b  through the bypass passage  60  only continues for a very short time of the initial stage of each exhaust stroke. Therefore, the deterioration in compression efficiency of the compressor caused by the communication of the chambers  16   b  and  16   c  may be negligible particularly in comparison with that of the conventional compressor caused by undesirable excessive compression of refrigerant due to the resonator  40 . In addition, different from the conventional compressor having the resonator  40 , the compressor of this invention is free from any dead cavity, which is undesirably remained in the compression chamber  16   c  at the final stage of a compressed refrigerant exhaust stroke and is free from exhausting compressed refrigerant from the cylinder  16 . Therefore, the compressor of this invention is free from any deterioration in its refrigerant compression efficiency caused by a re-expansion of completely compressed refrigerant. 
     FIG. 6 is a graph, showing pressure as a function of rotating angle of the eccentric roller within the cylinder of the rotary compressor according to this invention in comparison with a conventional rotary compressor. FIG. 7 is a drawing showing operational noise as a function of frequency of the rotary compressor according to the present invention in comparison with a conventional rotary compressor. As shown in FIG. 6, the pressure of the rotary compressor of this invention at a position around the exhaust stroke initiating point of the angle θ is lower than that of the conventional rotary compressor, and so the compressor of this invention is free from excessive compression of refrigerant and is effectively reduced in its operational noise at the initial stage of each exhaust stroke. In addition, the graph of FIG. 7 shows that the compressor of this invention is remarkably reduced in its operational noise over a variety of frequency bands in comparison with the conventional rotary compressor. 
     As described above, the rotary compressor according to the invention has a bypass passage on the internal surface of the cylinder at a position around a refrigerant exhaust stroke initiating point spaced apart from the spring-biased vane at a counterclockwise angle θ, with the bypass passage allowing the compression and exhaust chambers to communicate with each other at the initial stage of each exhaust stroke. Due to such a bypass passage, pressure pulsation of highly compressed refrigerant gas is effectively discharged from the compression chamber into the suction chamber at the initial stage of each exhaust stroke, thus remarkably reducing a rapid pressure variation at a time the exhaust port of the cylinder is opened different from a conventional rotary compressor having a resonator at its cylinder. The bypass passage also prevents an undesired excessive compression of refrigerant at the initial stage of each exhaust stroke, thus finally reducing both impact vibration and pulsation noise caused by such an excessive pressure variation. 
     The rotary compressor of this invention is effectively reduced in its operational noise over a variety of frequency bands from a low frequency band to a high frequency band. Therefore, the operational noise of the compressor according to this invention is preferably reduced by 3 dB or more. 
     In the rotary compressor of this invention, the compression efficiency is almost free from excessive compression of refrigerant, thus being less likely to be reduced in its compression efficiency due to such excessive compression of refrigerant. Another advantage of the rotary compressor of this invention resides in that it is free from any dead cavity, which is undesirably remained in the compression chamber of its cylinder at the final stage of each exhaust stroke and is free from exhausting compressed refrigerant from the cylinder. The compressor of this invention is thus free from any deterioration in its refrigerant compression efficiency caused by a re-expansion of completely compressed refrigerant. 
     Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.