Abstract:
Scroll compressor including wraps of involute curves on opposite surfaces of an orbiting scroll and a fixed scroll engaged to each other, to form a compression chamber as the orbiting scroll orbits with respect to the fixed scroll, wherein each of the wraps on opposite surfaces of the orbiting scroll and the fixed scroll is formed from two or more than involute curves each having a base circle and a point of starting different from each other, thereby permitting to secure a larger compression space for a same sized scroll compressor while a reliability of the scroll compressor is not made poor, to reduce a centrifugal force and noise occurred at the orbiting scroll, and improving a stability of the orbiting scroll.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to scroll compressors, and more particularly, to a wrap structure of each scroll in the scroll compressor for compressing refrigerant as an orbiting scroll orbits a fixed scroll.  
           [0003]    2. Background of the Related Art  
           [0004]    In general, the scroll compressors are mostly used in room air conditioners or car air conditioners as the scroll compressors have low noise, and small sized and light weighted, in which one pair of opposite scrolls form a compression chamber, in which the refrigerant is compressed. FIG. 1 illustrates a section of a related art scroll compressor, referring to which the related art scroll compressor will be explained.  
           [0005]    Referring to FIG. 1, there is an enclosed shell of a body  1  having an inlet tube  11  and an outlet tube  15  connected thereto for drawing and discharging the refrigerant, respectively. There is a fixed scroll  8  in an upper part of the body  1  having an outlet  12  at a central part  12  thereof and a wrap  8   a  of an involute curve projected downward from a bottom thereof. Also, there is an orbiting scroll  7  under the fixed scroll  8  orbitably coupled with the fixed scroll  8  in correspondence thereto having a wrap  7   a  of an involute curve projected upward. Side surfaces of the wraps  8   a  and  7   a  on the fixed, and orbiting scrolls  8  and  7  are made to be brought into contact as well as fore ends of the wraps  8   a  and  7   a  and scroll dish plates (disks the wraps are formed thereon), to form a compression chamber (a space which encloses refrigerant therein and is involved in gradual reduction for implementing compression).  
           [0006]    The orbiting scroll  7  has a crank shaft  6  fixed to a bottom thereof for orbiting the orbiting scroll  7  as the crank shaft  6  transmits a rotating force from a motor part  5 , provided in a lower part of the body  1 , to the orbiting scroll  7  via an Oldham ring  9  that prevents rotation of the orbiting scroll  7 , to reduce a volume of the compression chamber gradually to compress the refrigerant trapped between the two scrolls  7  and  8  and discharge through the outlet tube  15 .  
           [0007]    FIGS.  2 A˜ 2 D illustrate the steps of a process for compressing refrigerant in a related art scroll compressor, referring to which the operation of the related art scroll compressor will be explained in detail.  
           [0008]    Upon application of power to the motor part  5 , the crank shaft  6  rotates to rotate the orbiting scroll  7  fixed on a top thereof. In this instance, the orbiting scroll  7  is made to orbit spaced from a center of the crank shaft  6  by a preset orbiting radius in a state rotation is prevented by the Oldham ring  9 . As shown in FIG. 2B, low temperature and low pressure refrigerant  20  drawn into the body  1  through the inlet tube  11  after being heat exchanged at an evaporator during the foregoing process is the compression chamber through refrigerant inlets  21  and  22  formed by the wraps  8   a  and  7   a  on the fixed scroll  8  and the orbiting scroll  7 , respectively.  
           [0009]    Then, as shown in FIGS. 2C and 2D, as the orbiting scroll  7  keeps to orbit, the refrigerant is involved in gradual decrease of a volume thereof and flows toward a central portion of the compression chamber, i.e., to a location where the outlet  12  of the fixed scroll  8  is formed. It can be known that, as explained, the refrigerant is compressed to high temperature and pressure as the refrigerant is involved in gradual decrease of volume during the refrigerant flows toward the central portion of the compression chamber.  
           [0010]    At the end, as shown in FIG. 2D, the refrigerant compressed thus is discharged through the outlet  12  passed through the fixed scroll  8 , and, therefrom, to a condenser through the outlet tube  15 , when new refrigerant to be compressed is drawn through the refrigerant inlets  21  and  22  of the compression chamber formed as the scrolls  7  and  8  are engaged.  
           [0011]    The foregoing related art scroll compressor is required to compress the refrigerant gradually as the refrigerant goes toward the central portion of the compression chamber, for which it is very important that the wraps  7   a  and  8   a  of the orbiting scroll  7  and the fixed scroll  8  are required to be designed to come into a close contact at an appropriate positions.  
           [0012]    FIGS.  3 A˜ 3 C illustrate the steps of a process for forming an orbiting scroll wrap of a related art scroll compressor, referring to which structures of the orbiting scroll wrap  7   a  and a fixed scroll wrap  8   a  of the related art scroll compressor will be explained.  
           [0013]    Referring to FIG. 3A, a base circle  30  with a radius ‘a’ is drawn on a center on an X-, and Y-axes. Then, an involute curve is drawn, taking one point on a circumference of the base circle  30  at a starting angle ‘α’ from the X-axis as a starting point, i.e., an inner involute curve is drawn. One point on the inner involute curve  31  for the base circle  30  may be expressed with a parameter ‘θ’ as follows.  
             X   i   =a ×{cos(θ i −α)+θ i ×sin(θ i −α)}, and  
             Y   i   =a ×{sin(θ i −α)−θ i ×cos(θ i −α)} 
           [0014]    Then, as shown in FIG. 3B, in order to form a thickness of the wrap  7   a  of the orbiting scroll  7 , another involute curve started from a point at ‘−α’ angle to the X-axis on the circumference of the base circle  30 , i.e., an outer involute curve  32 , is drawn. One point on the outer involute curve  32  for the base circle  30  may be expressed with a parameter ‘θ’ as follows.  
             X   o   =a ×{cos(θ o +α)+θ o ×sin(θ o +α)}, and  
             Y   i   =a ×{sin(θ o +α)−θ o ×cos(θ o +α)} 
           [0015]    A distance of the inner involute curve  31  and the outer involute curve form a thickness ‘t’ for forming the wrap. Thus, as shown in FIG. 3C, upon completion of formation of involute curves, the orbiting scroll  7   a  can be formed by using the involute curves.  
           [0016]    FIGS.  4 A˜ 4 C illustrate the steps of a process for forming a fixed scroll wrap of a related art scroll compressor, the fixed scroll wrap  8   a  is formed in a form having a 180° phase difference from the orbiting scroll wrap  7   a . That is, a base circle  40  with a radius ‘a’ is drawn in a method identical to the base circle  30  drawn for the orbiting scroll wrap  7   a , inner, and outer involute curves  41  and  42  are drawn starting from points on the circumference of the base circle  40 , and the fixed scroll wrap  8   a  is formed based on the involute curves  41  and  42  of the scroll compressor, of which detailed explanation will be omitted.  
           [0017]    For making appropriate points of the wraps  7   a  and  8   a  of the orbiting scroll  7  and the fixed scroll  8  are brought into contact, orbiting radiuses of the involute curves are required to have a relation of (P−2t)/2, where P=2πa, i.e., a pitch of the wraps  7   a  and  8   a  on the scrolls, and ‘t’=2aα, i.e., the thickness of the wrap. Accordingly, the compression chamber is formed as the orbiting scroll  7  is made to orbit along an orbiting radius by the motor  5 , and the refrigerant drawn into the compression chamber is compressed.  
           [0018]    However, the foregoing scroll wrap structures have the following problems in light of the present trend in which the scroll compressor is made the smaller while capacity and efficiency are enhanced.  
           [0019]    That is, in order to increase a capacity of the related art scroll compressor, there is no way, but to increase a height of the wrap on the scroll, or to increase an overall size of the scroll compressor, which, not only is against the recent trend of making the scroll compressor the smaller, but also makes a reliability of the scroll compressor poor, if the heights of the wraps on the scrolls are increased, that makes points of action of a pressure occurred as the refrigerant is compressed is higher as much as the increased height of the wrap.  
           [0020]    The increased centrifugal force in proportion to an increased mass of the orbiting scroll  7  causes noise heavier when the orbiting scroll  7  and the fixed scroll  8  are in contact, and a light weighted orbiting scroll is essential for extending application of the scroll compressor to a high compression range.  
         SUMMARY OF THE INVENTION  
         [0021]    Accordingly, the present invention is directed to a scroll compressor that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.  
           [0022]    An object of the present invention is to provide a scroll compressor, which can secure a greater compression space for the same size of scroll compressor while a reliability of the scroll compressor is not made poor.  
           [0023]    Another object of the present invention is to provide a scroll compressor, which can reduce a centrifugal force and noise occurred at the orbiting scroll, and enhance stability of the orbiting scroll.  
           [0024]    Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0025]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the scroll compressor includes wraps of involute curves on opposite surfaces of an orbiting scroll and a fixed scroll engaged to each other, to form a compression chamber as the orbiting scroll orbits with respect to the fixed scroll, wherein each of the wraps on opposite surfaces of the orbiting scroll and the fixed scroll is formed from two or more than involute curves each having a base circle and a point of starting different from each other.  
           [0026]    The wraps on opposite surfaces of the orbiting scroll and the fixed scroll includes a first involute curve and a second involute curve of base circles and starting points different from each other employed alternately. The second involute curve preferably has the base circle radius and an angle to an X-axis of the starting point smaller than the first involute curve.  
           [0027]    The first involute curve and the second involute curve are used alternately at 180° intervals of the involute angles of respective involute curves. The first and second involute curves preferably alternate at 90° of involute angle from an outer end of the orbiting scroll wrap or the fixed scroll wrap.  
           [0028]    The orbiting scroll wrap employs the second involute curve from 450° of involute angle and over, and the fixed scroll wrap employs the second involute curve from 630° of involute angle and over.  
           [0029]    In another aspect of the present invention, there is provided a scroll compressor including wraps of involute curves on opposite surfaces of an orbiting scroll and a fixed scroll engaged to each other, to form a compression chamber as the orbiting scroll orbits with respect to the fixed scroll, wherein the wraps of the orbiting scroll and the fixed scroll have thickness different from each other.  
           [0030]    The wrap of the orbiting scroll has a thickness relatively thinner than the wrap of the fixed scroll.  
           [0031]    The wraps of involute curves on the orbiting scroll and the fixed scroll have the same base circle radiuses ‘a’, and different angles of starting points of the wraps of α1 and α2 to an X-axis, respectively. The angles of starting points α1 and α2 have a relation of 0.5α1≦α2&lt;α1.  
           [0032]    The wrap of the fixed scroll has a thickness formed relatively thinner than a thickness of the wrap of the orbiting scroll.  
           [0033]    The wraps of involute curves on the orbiting scroll and the fixed scroll have the same base circle radiuses and angles of starting points of β1 and β2 different from each other. The angles of starting points β1 and β2 of wraps of the orbiting scroll and the fixed scroll respectively have a relation of 0.5β1≦β2&lt;1.  
           [0034]    Thus, the scroll compressor of the present invention permits to secure a larger compression space for a same sized scroll compressor while a reliability of the scroll compressor is not made poor, to reduce a centrifugal force and noise occurred at the orbiting scroll, and improves a stability of the orbiting scroll.  
           [0035]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention:  
         [0037]    In the drawings:  
         [0038]    [0038]FIG. 1 illustrates a section of a related art scroll compressor;  
         [0039]    FIGS.  2 A˜ 2 D illustrate the steps of a process for compressing refrigerant in a related art scroll compressor;  
         [0040]    FIGS.  3 A˜ 3 C illustrate the steps of a process for forming an orbiting scroll wrap of a related art scroll compressor;  
         [0041]    FIGS.  4 A˜ 4 C illustrate the steps of a process for forming a fixed scroll wrap of a related art scroll compressor;  
         [0042]    [0042]FIGS. 5A and 5B illustrate the steps of a process for forming a first and a second involute curves employed in an orbiting scroll wrap of a scroll compressor in accordance with a first preferred embodiment of the present invention;  
         [0043]    [0043]FIGS. 6A and 6B illustrate the steps of a process for forming a first and a second involute curves employed in a fixed scroll wrap of a scroll compressor in accordance with a first preferred embodiment of the present invention;  
         [0044]    [0044]FIG. 7 illustrates a coupled state of an orbiting scroll wrap and a fixed scroll wrap formed in accordance with a first preferred embodiment of the present invention;  
         [0045]    [0045]FIGS. 8A and 8B compare radiuses of the first embodiment scroll wraps of the present invention and the related art scroll wraps;  
         [0046]    [0046]FIGS. 9A and 9B illustrate the steps of process for forming an orbiting scroll wrap and a fixed scroll wrap in accordance with a second preferred embodiment of the present invention;  
         [0047]    [0047]FIG. 10 illustrates a coupled state of an orbiting scroll wrap and a fixed scroll wrap formed in accordance with a second preferred embodiment of the present invention;  
         [0048]    [0048]FIGS. 11A and 11B illustrate the steps of process for forming an orbiting scroll wrap and a fixed scroll wrap in accordance with a third preferred embodiment of the present invention;  
         [0049]    [0049]FIG. 12 illustrates a coupled state of an orbiting scroll wrap and a fixed scroll wrap formed in accordance with a third preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0050]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.  
         [0051]    First Embodiment  
         [0052]    [0052]FIGS. 5A and 5B illustrate the steps of a process for forming a first and a second involute curves employed in an orbiting scroll wrap of a scroll compressor in accordance with a first preferred embodiment of the present invention, referring to which the steps of process for forming the first and second involute curves  101  and  102  will be explained.  
         [0053]    In order to form an orbiting scroll wrap  100  (see FIG. 7), two involute curves, i.e., a first involute curve  101  and a second involute curve  102  are required.  
         [0054]    As shown in FIG. 5A, for forming the first involute curve  101 , an imaginary base circle  50  is formed with a radius ‘a’ centered on an X-axis, and a Y-axis. Then, an inner involute curve  101   a  is drawn starting from a point on a circumference of the base circle  50  at an angle ‘α’ from the X-axis. As shown in FIG. 5A, for forming a thickness ‘t1’ of the orbiting scroll wrap  100  of the first involute curve  101 , an outer involute curve  101   b  is formed starting from one point on a circumference of the base circle  50  at an angle ‘−α’ to the X-axis. Thus, a first involute curve  101  with a thickness ‘t1’ is formed by using the inner involute curve  101   a  and the outer involute curve  101   b.    
         [0055]    As shown in FIG. 5B, for forming the second involute curve  102 , an imaginary base circle  60  is formed with a radius ‘b’ centered on an X-axis, and a Y-axis. Then, an inner involute curve  102   a  is drawn starting from a point on a circumference of the base circle  60  at an angle ‘β’ from the X-axis. As shown in FIG. 5B, for forming a thickness ‘t2’ of the orbiting scroll wrap  100  of the first involute curve  101 , an outer involute curve  102   b  is formed starting from one point on a circumference of the base circle  60  at an angle −‘β’ to the X-axis. Thus, a second involute curve  102  with a thickness ‘t2’ is formed by using the inner involute curve  101   a  and the outer involute curve  101   b.    
         [0056]    [0056]FIGS. 6A and 6B illustrate the steps of a process for forming a first and a second involute curves employed in a fixed scroll wrap of a scroll compressor in accordance with a first preferred embodiment of the present invention, referring to which the process for forming the first and second involute curves  201  and  202  will be explained.  
         [0057]    In order to form the fixed scroll wrap  200  (see FIG. 7), it is required to draw two involute curves, a first involute curve  201  and a second involute curve  202 , having a 180° phase difference from the orbiting scroll wrap  100 .  
         [0058]    As shown in FIG. 6A, for forming the first involute curve  201 , an imaginary base circle  70  is formed with a radius ‘a’, and an inner involute curve  201   a  and an outer involute curve  201   b  are formed starting from points on a circumference of the base circle  70  at angles ‘a’ and ‘−α’ from an X-axis, respectively. Then, a first involute curve  201  having a thickness ‘t1’ is formed by using the inner involute curve  201   a  and the outer involute curve  201   b.    
         [0059]    Then, as shown in FIG. 6B, an imaginary base circle  80  is formed with a radius ‘b’, and an inner involute curve  202   a  and an outer involute curve  202   b  are formed starting from points on a circumference of the base circle  80  at angles ‘β’ and ‘−β’ from an X-axis, respectively. Then, a second involute curve  202  having a thickness ‘t2’ is formed by using the inner involute curve  202   a  and the outer involute curve  202   b.    
         [0060]    [0060]FIG. 7 illustrates a coupled state of an orbiting scroll wrap and a fixed scroll wrap formed in accordance with a first preferred embodiment of the present invention, referring to which structures of the orbiting scroll wrap  100  and the fixed scroll wrap  200  in accordance with a first preferred embodiment of the present invention will be explained.  
         [0061]    As shown, because the orbiting scroll wrap  100  and the fixed scroll wrap  200  are formed to have the same orbit radiuses, surfaces of the wraps are brought into contact, to form a plurality of compression chambers. However, as explained, since the orbiting scroll wrap  100  and the fixed scroll wrap  200  are formed by employing two involute curves having different angles ‘α’ and ‘β’ of starting points and radiuses of base circle diameters ‘a’ and ‘b’ alternately, the wraps  100  and  200  have forms with different thickness ‘t1’ and ‘t2’ alternated at fixed intervals, which will be explained in detail.  
         [0062]    With regard to the structure of the fixed scroll wrap  200 , a part of the wrap  200  from a starting point AO at a central part of the wrap  200  to a point A1 at 450° of involute angle is formed according to a first involute curve  201  (see FIG. 6A), and a part of the wrap  200  from the point A1 to a point A2 at 180° of involute angle is formed according to a second involute curve  202  (see FIG. 6B).  
         [0063]    Then, a part of the wrap  200  from the point A2 to a point A3 at 180° of involute angle is formed according to the first involute curve  201  again, a part of the wrap  200  from the point A3 to a point A4 at 180° of involute angle is formed according to the second involute curve  202 , and a part of the wrap  200  from the point A4 to a point A5 at 90° of involute angle is formed according to the first involute curve  201 , again.  
         [0064]    Of the parts of the fixed scroll wrap  200 , parts formed according to the first involute curve  201  have the thickness of ‘t1’ (the same with a wrap thickness ‘t’ in the related art fixed scroll wrap  8   a ), and parts formed according to the second involute curve  202  have a thickness ‘t2’ relatively thinner than the ‘t1’. Accordingly, the parts A1-A2, and A3-A4 have a wrap thickness thinner by t1-t2 than the thickness of the parts A0-A1, A2-A3, and A4-A5. That is, if it is assumed that the thickness ‘t’ (see FIGS. 4B and 4C) of the related art fixed scroll wrap  8   a  is the same with the thickness ‘t1’ of the fixed scroll wrap  200 , the scroll compressor of the present invention is made to have a volume of the compression chamber increased by an amount of thickness reduction from ‘t1’ to ‘t2’ of the fixed scroll wrap  200 . In this instance, since the part A0-A1 of the wrap  200  has a relatively high pressure occurred therein, it is preferable that the part A0-A1 of the wrap  200  is formed to have a thickness the same with the related art ‘t1’ for preventing the central part of the wrap  200  suffering from damage.  
         [0065]    Opposite to this, since parts from A1-A5 of the wrap  200  have absolute pressures and pressure differences between chambers comparatively lower than the central part of the wrap  200 , a strength of the wrap matters not so much, permitting to form the wrap to form thinner than the thickness of the related art wrap  8   a.    
         [0066]    Since the fixed scroll wrap  200  has different involute curves employed at each of the parts A1-A5, the wrap  200  has different thickness and radius of curvatures. Accordingly, steps  211 ,  212 , and  213  are formed at the points A2-A4 for connecting parts of the wrap  200  having different thickness and radius of curvatures. The steps  211 ,  212 , and  213  are arcs so that different surfaces of the orbiting scroll wrap  100  and the fixed scroll wrap  200  can maintain close contact states.  
         [0067]    A structure of the orbiting scroll wrap  100  will be explained.  
         [0068]    A part of the wrap  100  from a starting point B0 at a central part of the wrap  100  to a point B1 at 630° of involute angle is formed according to a first involute curve  101  (see FIG. 5A), and a part of the wrap  100  from the point B1 to a point B2 at 180° of involute angle is formed according to a second involute curve  102  (see FIG. 5B). A part of the wrap  100  from the point B2 to a point B3 at 90° of involute angle is formed according to the first involute curve  102  again, and a part of the wrap  100  from the point B3 to a point B4 at 00° of involute angle is formed according to a second involute curve  102 .  
         [0069]    Of the parts of the orbiting scroll wrap  100 , parts formed according to the first involute curve  101  have the thickness of ‘t1’ (the same with a wrap thickness ‘t’ in the related art orbiting scroll wrap  7   a ), and parts formed according to the second involute curve  102  have a thickness ‘t2’ relatively thinner than the ‘t1’. That is, the parts B1-B2, and B3-B4 have a wrap thickness t2 relatively thinner than the thickness of the parts B0-B1, and B2-B3. Accordingly, the wrap thickness in parts of B1-B2, and B3-B4 is made thinner by t1-t2 in comparison to the parts B0-B1 and B2-B3.  
         [0070]    The scroll compressor of the present invention is made to have a volume of the compression chamber increased by an amount of thickness reduction from ‘t1’ to ‘t2’ of the orbiting scroll wrap  100 . Moreover, mass of the orbiting scroll can be reduced as much as the reduction of volume of the orbiting scroll wrap  100 .  
         [0071]    In this instance, since the part B0-B1 of the wrap  100  has a relatively high pressure occurred therein, it is preferable that the central part of the wrap  100  is formed to have a thickness the same with the related art ‘t1’. Opposite to this, since parts from B1-B4 of the wrap  100  may be formed thinner than the thickness of the central part of the wrap  100 .  
         [0072]    Alike the fixed scroll wrap  200 , since the orbiting scroll wrap  100  also has different involute curves employed at each of the parts B1-B4, the wrap  100  has different thickness and radius of curvatures. Accordingly, steps  111 ,  112 , and  113  are formed at the points B2-B4 for connecting parts of the wrap having different thickness and radius of curvatures. Positions of the steps  111 ,  112 , and  113  of the orbiting scroll wrap  100  and the steps  211 ,  212 , and  213  of the fixed scroll wrap  200  are at 90° of an involute angle from an outer end of the orbiting scroll wrap  100  or the fixed scroll wrap  200 . By doing so, an outer diameter of the orbiting scroll or the fixed scroll can be reduced.  
         [0073]    [0073]FIGS. 8A and 8B compare radiuses of the first embodiment scroll wraps of the present invention and the related art scroll wraps.  
         [0074]    Referring to FIGS. 8A and 8B, when it is assumed that a distance from an outer surface of an outer end of the orbiting scroll wrap  100  formed according to the second involute curve  102  to a center ‘c’ of the compression chamber is L1 (see FIG. 8A), and a distance from an outer surface of an outer end of the related art orbiting scroll wrap  7   a  to a center ‘c” of the compression chamber is l1 (see FIG. 8B), L1 is shorter than l1, because the involute curve of the orbiting scroll wrap  100  has a relatively smaller angle of the starting point and base circle radius than the involute curve of the related art orbiting scroll wrap  8   a  at parts of B3-B4, to form a thinner wrap thickness and smaller wrap radius than the related art orbiting scroll wrap  8   a.    
         [0075]    Alike the L1, distances L4, L3, and L2 (see FIG. 8A) from the center ‘c’ to an outer surface of each of the parts A1-A2, B1-B2, and A3-A4 located in succession toward an outer end of each of the wraps  100  and  200  are shorter than l4, l3, and l2 (see FIG. 8B) in the orbiting scroll wrap  7   a  and the fixed scroll wrap  8   a  corresponding to the L4, L3, and L2 respectively.  
         [0076]    As explained, since the lengths L1, L2, L3 and L4 of the wraps  100  and  200  are relatively shorter than l1, l2, l3, and l4, shifting locations of the parts of the wraps  100  and  200  inward, an outside diameter of the scrolls can be made smaller. Accordingly, a center of gravity of the orbiting scroll is shifted inward compared to the related art orbiting scroll, that improves stability of the orbiting scroll.  
         [0077]    The scroll compressor having the first embodiment scroll wraps of the present invention applied thereto has the following advantages.  
         [0078]    The formation of the scroll wrap from involute curves of different base circles and starting points in the first embodiment of the present invention varies radius of curvatures and thickness from part to part. That is, since parts of the wrap are shifted inward in a radial direction, together with a center of gravity of the scroll, a stability of the scroll is enhanced.  
         [0079]    The formation of parts of the scroll wrap from different involute curves, i.e., the first and second involute curves in the first embodiment of the present invention provides wrap thickness different from each other, with a wrap thickness from the second involute curve thinner than the warp thickness from the first involute curve, that increases a volume of the compression chamber as much as a reduction of the wrap thickness, to increase a compression space for the same size of scroll compressors. On the other hand, a central region of the scroll warp where a high pressure is occurred has the wrap thickness the same with the related art wrap, for not deteriorating a reliability of the scroll compressor.  
         [0080]    Second Embodiment  
         [0081]    [0081]FIGS. 9A and 9B illustrate the steps of process for forming an orbiting scroll wrap and a fixed scroll wrap in accordance with a second preferred embodiment of the present invention, and FIG. 10 illustrates a coupled state of an orbiting scroll wrap and a fixed scroll wrap formed in accordance with a second preferred embodiment of the present invention, referring to which structures of an orbiting scroll wrap  400  and a fixed scroll wrap  300  of the second embodiment of the present invention will be explained in detail.  
         [0082]    Referring to FIG. 9A, for forming an orbiting scroll wrap  400 , an imaginary base circle  410  with a radius ‘a’ is formed on a center on an X-axis and Y-axis. Then, an inner involute curve  411  is formed starting from a point on a circumference of the base circle  410  at an angle α1 from the X-axis. As shown in FIG. 9A, to form a thickness of the orbiting scroll wrap  400 , an outer involute curve  412  is formed starting from a point on a circumference of the base circle  410  at an angle −α1 from the X-axis. The inner involute curve  411  and the outer involute curve  412  form an orbiting scroll wrap  400  having a thickness t3.  
         [0083]    On the other hand, for forming the fixed scroll wrap  300 , as shown in FIG. 9B, a base circle  310  is formed in a method the same with a case of the orbiting scroll wrap  400 . Then, an inner involute curve  311  and an outer involute curve  312  are formed starting from points on a circumference of the base circle  310  at angles ‘α’ and ‘−α’ from the X-axis, respectively. The inner involute curve  311  and the outer involute curve  312  form a fixed scroll wrap  300  having a thickness ‘t4’. Both the orbiting scroll wrap  400  and the fixed scroll wrap  300  are formed from identical base circle, but with different starting points on a circumference of the base circle. The involute curves  411  and  412  of the orbiting scroll wrap  400  start at a point on the circumference of the base circle at an angle α1 to the X-axis, which is smaller than α2 to the X-axis both the involute curves  311  and  312  of the fixed scroll wrap  300  start therefrom.  
         [0084]    That is, as shown in FIG. 10, by taking α1 to be one half of α2, the orbiting scroll wrap  400  having a thickness one half of the related art orbiting scroll wrap  7   a  can be obtained, with an increased volume of the compression chamber formed by the orbiting scroll wrap  400  and the fixed scroll wrap  300  as much as an amount of reduction of the thickness of the orbiting scroll wrap  400  (a part “V” hatched in FIG. 10), and a decreased mass of the orbiting wrap  400  as much as the decreased volume of the orbiting wrap  400 .  
         [0085]    As explained, the smaller the α1 of the orbiting scroll wrap, the larger the volume of the compression chamber, and the orbiting scroll wrap  400  is permitted to be engaged with the fixed scroll wrap  300  in a changed orbiting radius to make compression of the refrigerant.  
         [0086]    On the other hand, it is preferable that the α1 is restricted to be 0.5α2≦α1&lt;α2 because excessive reduction of the wrap thickness causes strength and pressure problems of the orbiting wrap  400  and the fixed scroll wrap  300 .  
         [0087]    The scroll compressor having the second embodiment scroll wrap of the present invention applied thereto has the following advantages.  
         [0088]    The formation of the thickness of the orbiting scroll wrap relatively thinner than the related art orbiting scroll wrap increases the volume of the compression chamber formed by the orbiting scroll wrap and the fixed scroll wrap as much as the reduction of thickness of the orbiting scroll wrap thickness, permitting to secure a more compression space even though neither a frame size of the scroll compressor, nor a height of the wrap, is increased. Moreover, as weight of the scroll becomes the lighter as much as the thickness of the wrap is made the thinner, the orbiting scroll wrap can be made the lighter that allows improving a stability of the orbiting scroll.  
         [0089]    Third Embodiment  
         [0090]    [0090]FIGS. 11A and 11B illustrate the steps of process for forming an orbiting scroll wrap and a fixed scroll wrap in accordance with a third preferred embodiment of the present invention, and FIG. 12 illustrates a coupled state of an orbiting scroll wrap and a fixed scroll wrap formed in accordance with a third preferred embodiment of the present invention, referring to which structures of an orbiting scroll wrap  600  and a fixed scroll wrap  500  of a scroll compressor in accordance with the third preferred embodiment of the present invention will be explained.  
         [0091]    Alike the description in association with FIGS. 9A  9 B, for forming an orbiting scroll wrap  600 , an inner involute curve  611  is formed starting from a point on a circumference of a base circle  610  with a radius ‘a’, i.e., at an angle β1 from an X-axis. To form a thickness of the orbiting scroll wrap  600 , an outer involute curve  612  is formed starting from a point on a circumference of the base circle  610  at an angle −β1 from the X-axis. The inner involute curve  611  and the outer involute curve  612  form an orbiting scroll wrap  600  having a thickness t5.  
         [0092]    On the other hand, for forming the fixed scroll wrap  500 , a base circle  510  with a radius ‘a’ is formed in a method the same with a case of the orbiting scroll wrap  600 . Then, an inner involute curve  511  and an outer involute curve  512  are formed starting from points on a circumference of the base circle  510  at angles ‘β’ and ‘−β’ from the X-axis, respectively. Thus, the inner involute curve  511  and the outer involute curve  512  form a fixed scroll wrap  500  having a thickness ‘t6’, of which detailed description will be omitted as the third embodiment scroll wraps can be understandable from the prior embodiments. Both the orbiting scroll wrap  600  and the fixed scroll wrap  500  are formed from identical base circle with a radius ‘a’, but with different starting points on a circumference of the base circle. The involute curves  511  and  512  of the fixed scroll wrap  500  start at a point on the circumference of the base circle at an angle β2 to the X-axis, which is smaller than β1 to the X-axis both the involute curves  611  and  612  of the orbiting scroll wrap  600  start therefrom.  
         [0093]    That is, as shown in FIG. 12, by taking β2 to be one half of β, the fixed scroll wrap  500  having a thickness reduced as much as “V” compared to the related art fixed scroll wrap  8   a  can be obtained.  
         [0094]    It is preferable that the β2 is taken to be within a range of 0.5β1≦β2&lt;β1, for increasing the compression space, of which detailed explanation will be omitted, as it is understandable from the foregoing explanation.  
         [0095]    The scroll compressor having the third embodiment scroll wraps of the present invention applied thereto has advantages the same with the second embodiment of the present invention.  
         [0096]    It will be apparent to those skilled in the art that various modifications and variations can be made in the scroll compressor of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.