Abstract:
A bypass apparatus for a scroll compressor includes multiple bypass holes located at a plurality of locations along a path traced by the compression chambers of the compressor. A dimple portion having a large cross sectional area may be formed at an outlet of the bypass holes to increase the surface area of the compressed gas pushing against the bypass valves. Angled openings of the dimple portions, or angled openings of the bypass holes would also act to further increase the area of the compressed gas pushing on the bypass valves. The increased surface area of the gas pressing on the bypass, by virtue of its greater overall force, enhances an opening speed of the bypass valve. Accordingly, the over-compression of the refrigerant gas is prevented.

Description:
[0001]    The present application claims priority to Korean Application No. 10-2006-0023703, filed on Mar. 14, 2006, which is herein expressly incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention relates to a scroll compressor, and more particularly, to a bypass apparatus for a scroll compressor. 
         [0004]    2. Background 
         [0005]    Generally, a scroll compressor is widely used in air conditioning systems because it offers high efficiency and low noise. In the scroll compressor, two scrolls perform a relative orbiting motion, and a plurality of paired compression chambers are formed between the two scrolls. As the scrolls orbit with respect to each other, the compression chambers move towards a center of the scroll. During this movement, volume of the compression chambers decreases to thereby compress and discharge a refrigerant gas. 
         [0006]      FIG. 1  is a sectional view showing an example of a scroll compressor according to the conventional art.  FIG. 2  is a sectional view showing an operation state of a bypass valve of the compressor shown in  FIG. 1 . And  FIG. 3  is a plan view showing a discharge active area of a bypass valve of  FIG. 2 . 
         [0007]    The conventional scroll compressor includes a casing  1  having a gas suction pipe SP and a gas discharge pipe DP. A main frame  2  and a sub frame (not shown) are fixed to upper and lower sides of an inner circumferential surface of the casing  1 . A driving motor  3  is mounted between the main frame  2  and the sub frame. A drive shaft  4  is forcibly inserted into to the center of a rotor  3   b  of the driving motor  3  and also extends through the main frame  2 , to transfer a rotation force of the driving motor  3 . An orbiting scroll  5  is mounted on the main frame  2  and performs an orbiting motion because it is eccentrically mounted on the drive shaft  4 . An Oldham&#39;s ring  7  is disposed between the orbiting scroll  5  and the main frame  2  to prevent the orbiting scroll  5  from rotating on its axis. 
         [0008]    A fixed scroll  6  is fixed to an upper surface of the main frame  2  and forms an involute fixed wrap  6   a  so that a plurality of compression chambers P may be formed between the fixed and orbiting scrolls. A high/low pressure separator  8  divides the inside of the casing  1  into a suction space S 1  and a discharge space S 2 . The separator  8  is engaged with a rear surface of the fixed scroll  6 . A backflow valve  9  is disposed at the center of the rear surface of a plate portion of the fixed scroll  6  and prevents the backflow of a refrigerant gas, which is discharged from the discharge space S 2 . A bypass valve  10  is formed in the rear surface of the plate portion of the fixed scroll  6 . Refrigerant in the compression chambers can, in certain instances, pass from the compression chambers directly to the discharge space S 2 , thereby bypassing the normal flow path which passes through the outlet  6   c  and the backflow valve  9 . 
         [0009]    The involute-orbiting wrap  5   a  is formed at the front surface of the plate portion of the orbiting scroll  5 . The involute wrap  5   a  of the orbiting scroll  5 , together with the fixed wrap  6   a,  forms a pair of compression chambers. A boss unit  5   b  formed at the center of the lower surface of the plate portion of the orbiting scroll  5  is eccentrically coupled to the drive shaft  4  and receives the driving force from the driving motor  3  through the drive shaft  4 . 
         [0010]    The involute-fixed wrap  6   a  that helps to form the pair of compression chambers P is formed at the lower surface of the plate portion of the fixed scroll  6  and is engaged with the orbiting wrap  5   a  of the orbiting scroll  5 . An inlet  6   b  communicating with the gas suction pipe SP is formed at a side surface of the plate portion of the fixed scroll  6 . An outlet  6   c  communicating with the center of a final compression chamber P and discharging the refrigerant gas to the discharge space S 2  of the casing  1 , is formed at the center of the front surface of the plate portion of the fixed scroll  6 . A bypass hole  6 d is penetratingly formed at the rear surface of the plate portion of the fixed scroll  6 . 
         [0011]    The bypass valve  10  includes a reed-type valve plate  12  which opens/closes an upper end of the bypass hole  6 d in the fixed scroll  6 . The valve plate  12  is fixed to an outer side surface of the fixed scroll  6 . A retainer  11  disposed at a rear portion of the valve plate  12  is also fixed to the fixed scroll  6 , and the retainer  11  controls the amount or degree to which the valve plate  12  is allowed to open. 
         [0012]    Reference numeral  3   a  denotes a stator of the motor, and  4   a  denotes an oil channel passing through the drive shaft. 
         [0013]    When power is applied to the driving motor  3 , the drive shaft  4  is rotated with the rotor  3   b  of the driving motor  3 . The rotation of the drive shaft causes the orbiting scroll  5  to orbit, as controlled by the Oldham&#39;s ring  7 . A plurality of paired compression chambers P are consecutively formed between the orbiting wrap  5   a  of the orbiting scroll  5  and the fixed wrap  6   a  of the fixed scroll  6 . The compression chambers P move toward the center of the scroll by the consecutive orbiting motion of the orbiting scroll  5 , and the compression chambers decreases in volume as they move toward the center. Accordingly, a refrigerant gas is sucked, compressed, and discharged to the discharge space S 2 . When the refrigerant gas is compressed, the bypass valve  10  automatically opens/closes depending on a pressure differential between the compression chamber P and the discharge space S 2 . 
         [0014]    If the refrigerant within the compression chambers is compressed to a pressure greater than the pressure in the discharge space S 2 , the higher pressure in the compression chamber will cause the bypass valve  10  to open. Then, some of the gas from, within the compression chamber will flow from the compression chamber into the discharge space S 2  via the bypass hole  6 d. This can prevent damage to the compressor which might occur if the pressure in the compression chambers gets too high. In addition, it limits the amount of resistance the scroll compressor will exert against the driving force of the motor, which can improve overall efficiency. 
         [0015]    However, the conventional scroll compressor has the following problems. Because the diameter of the bypass hole is relatively small, the area of the gas within the bypass hole  6   d  that is pressing against the bypass valve  10  is relatively small. This means that the amount of force being exerted to open the bypass valve is relatively small, which means that the valve will open relatively slowly when an overpressure condition occurs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
           [0017]      FIG. 1  is a sectional view showing a scroll compressor in accordance with the conventional art; 
           [0018]      FIG. 2  is a sectional view showing the operation state of a bypass valve of the compressor shown in  FIG. 1 ; 
           [0019]      FIG. 3  is a plan view showing the discharge active area of refrigerant gas for the bypass valve shown in  FIG. 2 ; 
           [0020]      FIG. 4  is a sectional view showing a scroll compressor according to a first embodiment; 
           [0021]      FIG. 5  is a plan view showing the fixed scroll of the compressor shown in  FIG. 4 ; 
           [0022]      FIGS. 6A and 6B  are plan views showing the orientations of bypass holes provided in the fixed scroll shown in  FIG. 4 ; 
           [0023]      FIG. 7  is a plan view showing the bypass apparatus of the compressor as shown in  FIG. 4 ; 
           [0024]      FIG. 8  is a sectional view showing the operation state of the bypass apparatus of the compressor shown in  FIG. 4 ; 
           [0025]      FIG. 9  is a sectional view showing a modified example of the dimple portion of the bypass apparatus; and 
           [0026]      FIG. 10  is a sectional view showing another modified example of the bypass hole. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Reference will now be made in detail to preferred embodiments, examples of which are illustrated in the accompanying drawings.  FIG. 4  is a sectional view showing the scroll compressor in accordance with one embodiment of the present invention. 
         [0028]    Referring to  FIG. 4 , the scroll compressor according to the present invention includes a main frame  102  which is fixedly installed at an upper side of an inner circumferential surface of a casing  101 . A gas suction pipe SP and a gas discharge pipe DP are attached to the casing  101 . A fixed scroll  106  is fixedly installed on an upper surface of the main frame  102 . An orbiting scroll  105  is mounted on the main frame  102  via an Oldham&#39;s Ring  107 . A bypass valve  110  is formed at a rear surface of a plate portion of the fixed scroll  106 . 
         [0029]    An involute-orbiting wrap  105   a  is formed at the front surface of the plate portion of the orbiting scroll  105  and the involute orbiting wrap  105   a,  together with a fixed wrap  106   a  of the fixed scroll  106  forms a pair of compression chambers P. A boss unit  105   b  is formed at the center of the lower surface of the plate portion of the orbiting scroll  105  and is eccentrically coupled to the drive shaft  104 . 
         [0030]    An inlet  106   b  that communicates with the gas suction pipe SP is formed at a side surface of the plate portion of the fixed scroll  106 . An outlet  106   c  communicates with the center of a final compression chamber P and discharges the refrigerant gas to the discharge space S 2  of the casing  101 . The outlet  106   c  is formed at the center of the front surface of the plate portion of the fixed scroll  106 . 
         [0031]    One bypass hole may be formed in the fixed scroll for each of the compression champers P. Alternatively, bypass holes may be formed in the fixed scroll  106  at several locations along the path of each of the compression chambers P. The bypass holes are penetratingly formed at the rear surface of the plate of the fixed scroll  106  at locations that lie along the path of travel of the compression chambers P. 
         [0032]    As shown in  FIGS. 8-10 , each bypass valve  110  includes a reed-type valve plate  112  which opens/closes an upper end of a dimple portion  115  of the fixed scroll  106 . The valve plates  112  are fixed to the outer side surface of the fixed scroll  106 . Retainers  111 , which are disposed at the rear portion of the valve plate  112  and which are fixed to the fixed scroll  106 , control the amount or degree to which the valve plate  112  can open. 
         [0033]    Because of the way the involute wraps of the fixed and orbiting plates are formed the pair of compression chambers trace out a path as the orbiting plate moves. Referring to  FIG. 5 , at least one bypass hole  106   d  is formed along a travel path of each compression chamber P with a certain gap from a suction completing time point to a discharge starting time point. 
         [0034]    As shown in  FIGS. 4 and 5 , the bypass holes may be formed in pairs that are immediately adjacent one another. In this instance, a single bypass valve may cover both of the bypass holes in a pair. When a plurality of bypass holes  106   d  are formed for each bypass valve, the bypass holes  106   d,  as shown in  FIG. 6A , may be formed in a direction that corresponds to the direction the compression chambers travel so that the refrigerant to be compressed may be discharged in the forward direction along the compression chamber travel path. Alternatively, the bypass holes  106   d,  as shown in  FIG. 6B , may be formed in a direction which is perpendicular to the compression chamber travel path so as to prevent the orbiting wrap  105   a  from blocking one of the bypass holes as the orbiting wrap  105   a  moves. 
         [0035]    An upper sectional surface connected to the bypass holes  106   d  may be formed to be larger or smaller than a lower sectional surface of the bypass holes  106   d.  This can be done by controlling the configuration of the sidewalls, or by adding dimples, as will be explained. In some instances, this can lead to beneficial results. 
         [0036]    For instance, during a compression cycle, the refrigerant gas may be compressed to the point that it becomes a liquid, which is incompressible. If this occurs, further compression would no longer be possible. To solve this problem, the bypass holes  106   a  are formed in the fixed scroll. The bypass holes allow the incompressible liquid to escape the compression chambers P to the discharge area  52 . 
         [0037]    In order to enhance the reliability of the compressor by discharging the liquid refrigerant at an early stage of the compression, the upper sectional surface of the bypass hole  106   d  is preferably formed to be larger than the lower sectional surface thereof. When the upper sectional surface area of the refrigerant in the bypass holes is larger than the sectional surface area of the bypass holes themselves, a greater force is exerted on the valve plate. In other words, the total force exerted on the valve plate is the pressure per unit area multiplied by the total area. If the area is greater, the force is greater. And when the force is grater, the valve plate  112  will open faster. 
         [0038]    On the other hand, when the compressor is operating with a low load, in order to enhance the compressor efficiency by preventing the over-compression of the refrigerant gas and to reduce the amount of power consumption, the lower sectional surface thereof is preferably formed to be larger than the upper sectional surface. 
         [0039]      FIG. 7  is a plan view showing the bypass apparatus of the compressor shown in  FIG. 4 .  FIG. 8  is a cross sectional view showing the operation state of the bypass apparatus, and  FIG. 9  is a cross sectional view showing a modified example of a dimple portion of the bypass apparatus. Referring to  FIGS. 7 through 9 , the bypass holes  106   d  pass in the thickness direction of the plate portion of the fixed scroll  106 . Dimple portions  115  are formed at an exit end of the bypass holes  106   d  so as to increase the discharge active area of the refrigerant gas. The dimple portion  115  results in pressurized gas from the bypass holes  106   d  pushing against the entire shaded area of the valve plate  112  shown in  FIG. 7 . 
         [0040]    A cross-sectional shape of the bypass holes can be formed as a circle, an oval, or as a polygon. Similarly, the cross-sectional shape of the dimple portions  115  may form a circular section, an oval section, or a polygon section, all of which are larger than the cross section of the bypass holes  106   d.    
         [0041]    In some embodiments, one bypass hole  106   d  may communicate with one dimple portion  115 . In alternate embodiments, where paired bypass holes  106   d  are formed, a pair of bypass holes  106   d  may communicate with one dimple portion  115 . 
         [0042]    When a dimple is formed at the end of a single bypass hole, the greater surface area of the dimple increases the speed at which the bypass valve  110  opens. Further, when a plurality of paired bypass holes  106   d  are formed and a single dimple portion  115  is formed at the exit ends of the paired bypass holes  106   d,  the paired bypass holes would be simultaneously opened/closed by one bypass valve  110 , thus by reducing the number of components. 
         [0043]    The sidewalls of the dimple portion  116  may be inclined or curved so that the total cross sectional area opening onto the valve plate  112  can be increased. This would further increase the force applied to open the bypass valve, and thereby increase the opening speed.  FIG. 9  shows an embodiment where the exterior wall of the dimple is angled outward as it goes up, thereby increasing the surface area of the compressed gas pushing against the bypass valve  110 . 
         [0044]      FIG. 10  shows another embodiment where an extended portion  117  of the upper fixed scroll meets the underside of the valve plate  112 . In this embodiment, no dimple is formed. However, in this embodiment, the sidewalls of the bypass holes themselves are angled. Forming the openings to the bypass holes  106   d  with inclined sides would also serve to increase the amount of surface area of pressurized refrigerant pushing against the bypass valve. 
         [0045]    When power is applied to the driving motor  103  and the drive shaft  104  is rotated, the orbiting scroll  105 , which is eccentrically coupled to the drive shaft  104 , performs an orbiting motion. At this time, compression chambers P are formed between the orbiting scroll  105  and the fixed scroll  106 . As the compression chambers P move toward the center due to the orbiting motion, the volume of the compression chambers is decreased, thereby compressing a refrigerant gas and discharging the compressed gas to the discharge space S 2  of the casing  101 . 
         [0046]    When the pressure of the refrigerant gas is in the compressor chambers becomes excessively high, the refrigerant gas is discharged through the bypass holes  106 d. The dimple units  115 ,  116  or the angled extended portion  117  formed at the exit end of the bypass holes will increase the surface area of compressed gas pushing against the bypass valves. This in turn, increases the force applied to the valve plate  112  of the bypass valve  110  to enhance the opening speed of the bypass valve. Therefore, when the pressure of the compression chambers P is excessively high, the bypass valve is quickly opened, thereby rapidly discharging the refrigerant of the compression chambers P. Accordingly, compression loss of the motor may be reduced and performance of the compressor and reliability are enhanced. 
         [0047]    Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
         [0048]    Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.