Abstract:
A scroll compressor, which allows refrigerant in a compressor chamber to be partially discharged so that frictions generated in frictional surfaces between an orbiting scroll and an Oldham ring and between the Oldham ring and a main frame may be decreased. Also, an upper chamber may be formed on an upper surface thereof and a lower chamber may be formed on a lower surface thereof. An oil supply structure may be provided in a main frame such that lubrication is smoothly performed. Additionally, at least one key may be provided protruding from the lower surface of the Oldham ring. Further, the main frame may include at least one key groove configured to receive the at least one key of the Oldham ring. Additionally, the oil supply groove may be provided separately from and in communication with the at least one key groove.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a scroll compressor, and more particularly, to a scroll compressor in which high pressure generated by an orbiting movement of an orbiting scroll during a compressing operation is adjusted such that oil is smoothly distributed over parts of the compressor, thereby preventing breakage and abrasion of the parts. 
   2. Description of the Related Art 
   Generally, a scroll compressor is operated for compressing by means of relative movement of a fixed scroll and an orbiting scroll, and widely used in the fields of room air conditioners and automobile air conditioners owing to its advantageous characteristics such as high efficiency, low noise, small size and light weight. 
   The scroll compressor is classified into a low pressure scroll compressor and a high pressure scroll compressor according to the filling gas, namely whether an inhaling gas is filled in the casing or a discharging gas is filled therein, and the following description is based on the low pressure scroll compressor. 
   A scroll compressor generally includes a main frame, an Oldham ring seated on the upper surface of the main frame for linear movement, an orbiting scroll seated on the upper portion of the Oldham ring for orbiting movement, and a fixed scroll positioned at an upper portion of the orbiting scroll and fixed to the main frame. In addition, the fixed scroll has a fixed scroll wrap spirally twisted, and the orbiting scroll has an orbiting scroll wrap spirally twisted and formed on the upper surface thereof. In more detail, the fixed scroll wrap and the orbiting scroll wrap form a compressor chamber, and the fluid received in the compressor chamber is compressed by means of movement of the orbiting scroll. 
     FIG. 1  is a sectional view showing the compressing operation accomplished in a general scroll compressor of the related art. 
   Referring to  FIG. 1 , the conventional scroll compressor includes a fixed scroll wrap  81  formed on the fixed scroll, an orbiting scroll wrap  71  formed on the upper surface of the orbiting scroll and inserted into the fixed scroll wrap  81  to form a compressor chamber P, and a discharge port  9  formed at the center of the orbiting scroll wrap  71  and the fixed scroll wrap  81  so that a compressed fluid may be discharged through it. 
   To describe the compressing operation by the above configuration, the fluid collected in the compressor chamber P of a relatively larger volume formed in the outer portion of the scroll wraps  71  and  81  is moved toward the center by means of the orbiting movement of the orbiting scroll wrap  71 . As the fluid moves toward the center, its volume is gradually decreased, thereby increasing the pressure. In addition, the pressure of the fluid is maximum at the center of the scroll wraps  71  and  81 , and the fluid gathered at the center is discharged through the discharge port. 
   The compressor which is operated as above for compressing is already disclosed in U.S. Pat. No. 6,287,099, filed by the same applicant of this application. 
   The conventional scroll compressor may have a tip seal on the uppermost surface of the orbiting scroll wrap in order to prevent the fluid from being partially leaked outward when the pressure of the fluid is excessively increased. 
   However, in case of the conventional low pressure scroll compressor to which the above configuration is applied, the tip seal may be melted by high temperature in the compressor chamber P, and the refrigerant gas may be leaked out of the compressor chamber P. 
   In addition, if a pressure in the compressor chamber P is excessively increased, the excessive pressure is applied to the Oldham ring seated between the orbiting scroll and the main frame. That is to say, if an excessive pressure is applied to the Oldham ring, the excessive pressure causes excessive frictions between the lower end of the orbiting scroll and the upper end of the Oldham ring and between the lower end of the Oldham ring and the upper end of the main frame, thereby increasing the pressure loss caused by friction. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a scroll compressor that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
   An object of the invention is to provide a scroll compressor having an improved Oldham ring that can discharge a middle pressure coolant from a compressor chamber, and decreasing a frictional force applied to the Oldham ring by using the discharged middle pressure gas. 
   Another object of the present invention is to provide a scroll compressor that can prevent a high pressure gas in the compressor chamber from leaking out by rising an Oldham ring and an orbiting scroll with the use of the discharged middle pressure gas so that the orbiting scroll is closely adhered to a fixed scroll. 
   A further another object of the present invention is to provide a scroll compressor in which an excessive frictional force is not generated between a lower surface of the Oldham ring and a thrust surface of the main frame by means of the pressure in the compressor chamber. 
   A yet further another object of the present invention is to provide a scroll compressor that is provided with an oil channel to uniformly disperse a lubricating oil between a thrust surface and a lower surface of an Oldham ring, thereby reducing a frictional force between the thrust surface and the lower surface of the Oldham ring. 
   Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
   To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a scroll compressor, which includes: an orbiting scroll having a compressor chamber in an upper portion thereof and a bypass passage formed through upper and lower ends of a body thereof; a fixed scroll for allowing the orbiting scroll to orbit therein for compressing a refrigerant; an Oldham ring on which the orbiting scroll is seated, the Oldham ring having an upper chamber (i.e., second gas chamber) formed on an upper surface thereof with predetermined width and depth and a lower chamber (i.e., first gas chamber) formed on a lower surface thereof with predetermined width and depth; and a main frame on which the Oldham ring is seated, the main frame being provided with an oil supplying groove. 
   In another aspect of the present invention, there is provided a scroll compressor, which includes: a driving part including a driving motor and a driving shaft rotated by the driving motor; a scroll compressing part including an orbiting scroll and a fixed scroll for compressing a refrigerant inhaled while an orbiting wrap orbits inside a fixed wrap by a rotation of the driving shaft, and an Oldham ring designed such that the orbiting scroll can orbit inside the fixed scroll; and a main frame including a thrust surface contacted with a lower surface of the Oldham ring, and a caved portion formed on the thrust surface, for storing oil. 
   In still another aspect of the invention, there is also provided a scroll compressor, which includes: a driving shaft having an oil channel formed therein; a main frame for supporting the driving shaft, the main frame having key grooves oppositely formed on an upper surface thereof with predetermined depth and width; a fixed scroll fixedly combined to the main frame; an orbiting scroll seated on an upper portion of the main frame, the orbiting scroll having at least one bypass passage in one side thereof so that a compressed coolant is partially discharged through the bypass passage; and an Oldham ring seated between the orbiting scroll and the main frame, the Oldham ring having a back pressure chamber for storing a part of the discharged compressed coolant and a protrusion protruded in a predetermined height at upper and/or lower surfaces of a body thereof. 
   It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
       FIG. 1  is a sectional view showing a general scroll compressor according to the related art; 
       FIG. 2  is an enlarged sectional view showing main components of a scroll compressor according to the present invention; 
       FIG. 3  is a side sectional view showing an Oldham ring of the scroll compressor according to the present invention; 
       FIG. 4  is a perspective view showing a main frame of the scroll compressor according to the present invention; 
       FIG. 5  shows pressure distribution applied to an orbiting scroll and the Oldham ring in the scroll compressor according to the present invention; and 
       FIG. 6  is a sectional view showing refrigerant gas flows in a compressor chamber and forces exerted by the refrigerant gas in the scroll compressor according to the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. However, the spirit of the invention is not limited to the embodiments, but other embodiments may be easily proposed within the scope of the invention or other retrograde inventions by adding, changing or deleting other components. 
     FIG. 2  is an enlarged sectional view showing main components of a scroll compressor according to the present invention. 
   Referring to  FIG. 2 , the scroll compressor  100  of the present invention includes a main frame  300  for supporting an upper end of a driving shaft, an Oldham ring  200  seated on the upper portion of the main frame to linearly reciprocate, an orbiting scroll  400  seated on the upper portion of the Oldham ring to compress a coolant with orbiting, and a fixed scroll  500  fixed to the main frame  300  and forming a compressor chamber P therein together with the orbiting scroll. 
   In more detail, the main frame  300  includes a driving shaft hole  340  at its center so that the driving shaft passes through it, a thrust surface (described later) contacted with the lower surface of the Oldham ring  200 , and a lower key groove (described later) depressed toward the center as much as a predetermined length from the outer side of the thrust surface with predetermined depth and width. 
   In addition, the Oldham ring  200  includes at least two upper keys  210  protruded on the upper surface thereof as much as a predetermined height and combined with the lower end of the orbiting scroll  400 . Moreover, a lower key (described later) is also formed therein so as to be seated on the lower key groove formed in the main frame  300 . 
   In addition, an upper chamber  220  with a predetermined depth is formed at a position spaced apart from the center in a diameter direction as much as a predetermined distance. In more detail, the upper chamber  220  forms a circular strap with predetermined depth and width. In addition, a lower chamber  230  with predetermined height and width is formed upward from a lower bottom of the Oldham ring  200 . Here, a high pressure coolant gas stored in the compressor chamber P is received in spaces of the upper and lower chambers  220  and  230 . In addition, a communication groove  240  is formed vertically so as to connect the upper and lower chambers  220  and  230 . Thus, the coolant gas gathered in the upper chamber  220  is moved to the lower chamber  230  along the communication groove  240 . 
   Meanwhile, the orbiting scroll  400  seated on the upper end of the Oldham ring  200  includes a body  450  having a disc shape, and an orbiting scroll wrap  410  spirally curved on the upper end of the body with a predetermined height. In addition, at one side of the lower end of the orbiting scroll  400 , there are formed an upper key groove  420  on which the upper key protruded on the upper end of the Oldham ring  200  is inserted and seated, and an orbiting axis  440  having a circular rod shape which is extended in a vertical direction from the bottom surface of the body  450  as much as a predetermined length and has a hollow therein. 
   In addition, a bypass passage  430  is formed to pass through upper and lower portions of the body  450  with being inclined at a predetermined angle. In more detail, the bypass passage  430  is formed to communicate with the upper chamber  220  formed in the upper portion of the Oldham ring  200 . Thus, the high pressure coolant gas existing in the compressor chamber P is moved down along the bypass passage  430  to the upper chamber  220 . 
   Meanwhile, the fixed scroll  500  seated on the upper end of the orbiting scroll  400  is hollow and includes a fixed scroll wrap  510  spirally curved and having a predetermined length from the inner upper surface thereof. In more detail, the fixed scroll wrap  510  is seated between the orbiting scroll wraps  410  so as to form a compressor chamber P as the orbiting scroll  400  is orbiting. In addition, the volume of the compressor chamber P is decreased toward the center of the orbiting scroll  400 , so the coolant in the compressor chamber P is compressed at high pressure. Moreover, a discharge port  520  is formed at the center of the fixed scroll  500  so that the coolant compressed at high pressure is discharged to a discharge chamber (not shown). 
   Now, the compressing operation occurring at the scroll compressor  100  is described. 
   First, a coolant is introduced into the scroll compressor, and the introduced coolant is input to the compressor chamber P. In more detail, the coolant is received in the compressor chamber of a relatively large volume, formed at the edge of the scroll wraps  410  and  510 . In addition, as the orbiting scroll  400  orbits, the volume of the compressor chamber is decreased and moves to the center along the spiral of the scroll wraps  410  and  510 . And then, the coolant compressed at high pressure with moving to the center is transferred to the discharge chamber through the discharge port  520 . 
   Meanwhile, the edge of the fixed scroll  500  is combined to the main frame  300  by means of at least one combination member. In addition, the orbiting scroll  400  is linearly reciprocated on the upper surface of the Oldham ring  200 . Moreover, the Oldham ring  200  is linearly reciprocated on the upper surface of the main frame  300 . 
   Here, the direction that the orbiting scroll  400  is linearly reciprocated is crossed at a predetermined angle with the direction that the Oldham ring  200  is linearly reciprocated. Resultantly, the orbiting scroll  400  is orbited on the basis of the main frame  300 . 
     FIG. 3  is a side sectional view showing the Oldham ring of the scroll compressor according to the present invention. 
   Referring to  FIG. 3 , the Oldham ring  200  of the scroll compressor according to the present invention has an upper key  210  protruded on the upper surface thereof as much as a predetermined height. 
   In more detail, there are two upper keys  210  at positions faced with each other, and the upper keys  210  are inserted into the upper key grooves  420  formed in the lower surface of the orbiting scroll  400  as mentioned above. In addition, an orbiting axis hole  270  having a predetermined diameter is formed at the center of the Oldham ring  200 , and the orbiting axis  440  passes through the orbiting axis hole  270 . 
   In addition, the upper chamber  220  with predetermined width and depth is formed at a position spaced apart as much as a predetermined distance from the orbiting axis hole  270 . In more detail, the upper chamber  220  forms a circular strap along the circumferential shape of the Oldham ring  200 . In addition, an upper sealing member  250  is mounted to the inner circumferential edge of the upper chamber  220 . The upper sealing member  250  plays a role of preventing a middle pressure coolant introduced into the upper chamber  220  from being leaked through the upper end of the Oldham ring  200 . 
   Here, due to the pressure of the middle-pressure coolant collected in the upper chamber  220 , the orbiting scroll  400  is raised slightly from the upper surface of the Oldham ring  200 . It reduces the friction generated between the orbiting scroll  400  and the Oldham ring  200 . Furthermore, if the orbiting scroll  400  is raised, the upper surface of the orbiting scroll wrap  410  is closely adhered to the upper portion of the fixed scroll  500 . Thus, the oil cannot be leaked through the upper end of the orbiting scroll wrap  410 . 
   In addition to that, in the present invention, there is no need to attach a separate sealing member to the upper end of the orbiting scroll wrap  410  like the related art, so the conventional problem that the sealing member is melt by high pressure and high temperature in the compressor chamber P is eliminated. 
   In addition, the lower chamber  230  with predetermined width and depth is also provided to the lower surface of the Oldham ring  200 . A lower sealing member  260  is mounted to the inner circumferential edge of the lower chamber  230  in a strap shape. Thus, the middle pressure coolant received in the lower chamber  230  is not leaked out between the Oldham ring  200  and the mainframe  300 . 
   In more detail, the sealing members  250  and  260  attached to the upper and lower chambers  220  and  230  are made of resin material which endures high temperature, and their sections form a “           ” shape.
   In addition, the communication hole  240  for connection of the upper and lower chambers  220  and  230  is formed so that the coolant in the upper chamber  220  may move to the lower chamber  230 . Moreover, due to the pressure possessed by the middle pressure coolant collected in the lower chamber  230 , the Oldham ring  200  is raised slightly from the main frame  300 . Thus, the friction generated between the Oldham ring  200  and the main frame  300  is reduced. 
   Meanwhile, the width of the lower chamber  230  is greater than the width of the upper chamber  220 . It is because the pressure applied to the lower chamber  230  is greater than the pressure applied to the Oldham ring  200 . This is described later in more detail. 
     FIG. 4  is a perspective view showing the main frame of the scroll compressor according to the spirit of the present invention. 
   Referring to  FIG. 4 , the main frame  300  of the scroll compressor according to the present invention includes the driving shaft hole  340  at its center for a driving shaft (not shown) to pass through, and the thrust surface  320  surface-contacted with the lower surface of the Oldham ring. 
   In addition, the main frame  300  includes an oil supplying groove  330  (e.g., provided as a caved portion) formed on the thrust surface  320  with a predetermined width and depth, and a lower key groove  310  formed facing the lower end of the Oldham ring  200  and into which the lower key  211  is inserted. The lower key groove  310  communicates with the oil supplying groove  330 . 
   In more detail, the oil supplying groove  330  is curved along a circumference of the thrust surface  320 , with a predetermined distance from a center of the thrust surface  320 . The lower key groove  310  and the oil supplying groove  330  are connected with each other such that the lubricating oil accommodated in the oil supplying groove  330  can flow into the lower key groove  310 . Therefore, the oil can lubricate inner surface of the lower key groove  310 . 
   Now, the process of supplying oil to the main frame  300  is described. 
   First, the lubricating oil is moved upward along an oil channel formed in the driving shaft, and then accumulated from the end of the driving shaft into a space interposed by the thrust surface  320 . And then, the oil accumulated in the space flows along the thrust surface  320 . Then, by means of the reciprocating movement of the Oldham ring  200  surface-contacted with the thrust surface  320 , the oil is dispersed uniformly on the whole thrust surface  320 . The oil dispersed along the thrust surface  320  is collected in the oil supplying groove  330  and the collected oil flows into the lower key groove  310 . Thus, the lubricating oil reduces a frictional heat generated between the Oldham ring and the thrust surface  320 . Further, since a residual oil on the thrust surface  320  is accommodated in the oil supplying groove  330 , the oil is not drifted. 
     FIG. 5  shows pressure distribution applied to the orbiting scroll and the Oldham ring in the scroll compressor according to the spirit of the present invention. 
   Referring to  FIG. 5 , a total coolant gas force F a  is offset by a middle pressure coolant gas back pressure F ocm2  to make the equilibrium of force. In more detail, the coolant gas force F a  means a force applied to the whole orbiting scroll  400  in the compressor chamber P. In addition, the middle pressure coolant gas back pressure F ocm2  means a back pressure of the coolant gas discharged from the upper chamber  220  to the lower chamber  230  through the communication hole  240  formed in the Oldham ring  200 . At this time, the Oldham ring  200  and the orbiting scroll  400  are raised up to a predetermined height until the whole coolant gas force F a  is in equilibrium with the coolant gas back pressure F ocm2 . In addition, if the coolant gas force F a  applied to the whole orbiting scroll  400  is in equilibrium with the back pressure F ocm2  of the coolant gas discharged to the lower chamber  230 , the upward movement of the Oldham ring  200  and the orbiting scroll  400  is stopped. 
   In addition, an adhering force between the orbiting scroll  400  and the fixed scroll  500  is changed according to the difference between the back pressure F ocm2  generated in the lower chamber  230  and the whole coolant gas force F a  applied to the whole orbiting scroll  400 . As a result, a thrust repulsive force F th1  is exerted on the surface where the orbiting scroll  400  and the fixed scroll  500  are contacted. 
   Meanwhile, the thrust repulsive force F th1  may adjust an amount of the coolant gas discharged to the lower chamber  230  through the bypass passage  430  formed through the body  450  of the orbiting scroll  400 , thereby being capable of controlling the back pressure F ocm2  applied to the lower chamber  230 . That is to say, by controlling the back pressure F ocm2  applied to the lower chamber  230 , a magnitude of the thrust repulsive force F th1 +F th2  applied to the orbiting scroll  400  may be controlled. 
   Here, the force applied to the orbiting scroll  400 , the force applied to the Oldham ring  200 , and the thrust repulsive force applied to both ends of the orbiting scroll  400  may be expressed by a mathematical equation as follows. 
   1. Force applied to the Orbiting Scroll
 
 F   th2   +F   ocm1   −F   a   −F   th1 =0
 
 F   th1   =F   th2   +F   ocm1   −F   a 
 
   2. Force applied to the Oldham Ring
 
 F   ocm2   −F   th2   −F   ocm1 =0
 
 F   th2   =F   ocm2   −F   ocm1 
 
   3. Thrust Repulsive Force
 
∴ F   th1   =F   ocm2   −F   a 
 
 F   th2   =F   ocm2   −F   ocm1 
 
     FIG. 6  is a sectional view showing coolant gas flows in the compressor chamber and forces exerted by the coolant gas in the scroll compressor according to the present invention. 
   Referring to  FIG. 6 , the scroll compressor of the present invention is formed to decrease the loss caused by the frictional force between the orbiting scroll  400  and the Oldham ring  200  and between the Oldham ring  200  and the main frame  300  by discharging a part of the high pressure coolant gas received in the compressor chamber P through the bypass passage  430 . 
   In more detail, if the middle pressure coolant discharged through the bypass passage  430  is collected in the upper chamber  220 , the pressure in the upper chamber  220  is increased. In addition, by means of the pressure, the coolant presses the upper sealing member  250  seated on the inner circumferential edge of the upper chamber  220 . 
   Meanwhile, since the upper sealing member  250  is made of material enduring high temperature with flexibility, the upper sealing member  250  leaves space by the pressure. As shown in the figure, the upper end of the upper sealing member  250  is upwardly inclined at a predetermined angle by the pressure of the upper chamber  220 , thereby leaving space. As a result, the orbiting scroll  400  seated on the upper end of the Oldham ring  200  is slightly raised by means of the pushing force of the upper sealing member  250 . As the upper end of the upper sealing member  250  leaves space, the upper sealing member  250  keeps contacting with the lower surface of the orbiting scroll  400 . Thus, the upper sealing member  250  prevents the coolant gas in the upper chamber  220  from being leaked through a gap. 
   To the contrary, the lower chamber  230  is open at its lower end. Thus, the lower end of the lower sealing member  260  mounted to the inner circumferential edge leaves space with being inclined downward, and its effect is identical to the upper sealing member  250 . That is to say, since the lower sealing member  260  pushes the thrust surface  320  of the main frame  300 , the pushing force makes the Oldham ring  200  be slightly raised from the thrust surface  320 . It reduces the frictional force generated between the Oldham ring  200  and the thrust surface  320 . In addition, the oil flowing along the thrust surface  320  may also be smoothly moved. 
   Meanwhile, as mentioned above, the lower chamber  230  has a width wider than the upper-chamber  220 . It is because the pressure supported by the lower chamber  230  should be greater than the pressure supported by the upper chamber  220 . 
   In addition, the lower end of the bypass passage  430  should be always communicated with the upper chamber  220  while the orbiting scroll  400  is orbiting. Thus, the orbiting diameter of the bypass passage  430  is preferably ranged between the inner and outer diameters of the upper chamber  220 . 
   Moreover, the upper end of the bypass passage  430  is communicated with the compressor chamber P through the upper surface of the orbiting scroll  400 . Here, the inner pressure of the compressor chamber P is gradually increased from an outside of the orbiting scroll  400  to the center. Thus, as the upper end of the bypass passage  430  is formed at a position nearer to the center of the orbiting scroll  400 , the back pressure of the discharged coolant gas is increased. 
   The scroll compressor according to the present invention forms a plurality of back pressure pockets and a plurality of feeding holes in the Oldham ring, thereby smoothly supplying oil between the thrust surface of the upper frame and the lower surface of the orbiting scroll though an overload is applied to the compressor. Thus, the scroll compressor of the present invention gives an effect of reducing or eliminating abrasion of parts, frictional heat, noise and vibration, which are caused by the friction. 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.