Abstract:
A scroll fluid machine comprises a stationary scroll that has a spiral stationary wrap, and an orbiting scroll that has a spiral orbiting wrap to form a compression chamber between the stationary and orbiting wraps. In the stationary and orbiting wraps, an outer low-pressure pressurizing portion is separated from an inner high-pressure pressurizing portion. A plurality of outlets and inlets are formed in the low-pressure and high-pressure pressurizing portions respectively. At least one of the outlets or at lease one of inlets is selectively closed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a scroll-type fluid machine suitable in use for an air compressor, a vacuum pump and an expansion machine.  
           [0002]    A known scroll-type fluid machine is disclosed in Japanese Patent No. 2,971,652.  
           [0003]    The fluid machine comprises an orbiting scroll that is connected to a drive shaft rotated by an AC electric motor to be able to revolve and has a spiral orbiting wrap on one side surface, a stationary scroll that faces the orbiting scroll and has a stationary wrap to form a compression chamber between the stationary and orbiting wraps, and tip seals that seals the compression chamber at the ends of the stationary wraps of the stationary scroll to be in sliding contact with the surface of the orbiting scroll.  
           [0004]    For example, if the scroll compressor set by frequency of 50 Hz for East Japan is used in West Japan, the tip seal is made to be shorter not to seal the winding finish of the stationary wrap. Therefore, even if the number of rotation of the AC electric motor becomes higher by the frequency of 60 Hz for West Japan, it prevents the scroll-type fluid machine not to be subject to overload operation. That is, the length of the tip seal can be changed depending on the frequency of AC voltage applied to the AC electric motor.  
           [0005]    However, in the known scroll-type fluid machine as above, it is necessary to change the length of the tip seal depending on the condition of use, and thus, various types of tip seals having different lengths have to be provided. Thus, it is impossible to use the same type of tip seals, thereby increasing cost. To replace the tip seal, it is necessary to remove other parts to involve troublesome replacement.  
         SUMMARY OF THE INVENTION  
         [0006]    In view of the disadvantages as above, it is an object of the present invention to provide a scroll-type fluid machine that need not replacement of parts even if condition in use is different, to prevent overload. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The features and advantages of the present invention will become more apparent from the following description with respect to embodiments as shown in appended drawings wherein:  
         [0008]    [0008]FIG. 1 is a vertical side sectional view of one embodiment of a scroll compressor according to the present invention;  
         [0009]    [0009]FIG. 2 is a vertical sectional view taken along the line  11 - 11  in FIG. 1;  
         [0010]    [0010]FIG. 3 is a perspective view of a stationary scroll in FIG. 1, seen from the front or stationary wrap;  
         [0011]    [0011]FIG. 4 is a vertical sectional view taken along the line IV-IV in FIG. 2;  
         [0012]    [0012]FIG. 5 is a vertical sectional view taken along the line IV-IV in FIG. 2 before mounting a closure member;  
         [0013]    [0013]FIG. 6 is a view showing operation of a compression chamber that is formed when the second low-pressure-side outlet is closed;  
         [0014]    [0014]FIG. 7 is a view showing operation of the compression chamber that is formed when the first low-pressure-side outlet is closed;  
         [0015]    [0015]FIG. 8 is a view showing operation of a compression chamber that is formed when the other high-pressure-side inlet is closed in another embodiment; and  
         [0016]    [0016]FIG. 9 is a view showing operation of a compression chamber that is formed when the high-pressure-side inlet is closed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    A stationary scroll  1  has a stationary end plate  5  that has a spiral stationary wrap  6  on the front surface (right side in FIG. 1) and a plurality of equally-spaced cooling fins  7  on the rear surface. The stationary end plate  5  is integrally formed with a housing  4  that has an inlet  2  at the outer portion and an outlet  3  at the center. The outlet  3  is connected to an external air tank via a conduit. (not shown) A tip seal  6  is provided at the end of the stationary wrap  6  and is in sliding contact with the front surface of an orbiting end plate  10 .  
         [0018]    An orbiting scroll  8  faces the front surface of the stationary scroll  1  and has a circular orbiting end plate  10 . The orbiting end plate  10  has a spiral orbiting wrap  11  on the front surface which faces the stationary scroll  1 , and a plurality of equal-height cooling fins  12  that are equally spaced. A tip seal  11   a  is provided on the end of the orbiting wrap  11  and is in sliding contact with the front surface of the stationary end plate  5 .  
         [0019]    A bearing plate  13  is fixed on the rear surface of the orbiting scroll  8  or opposite surface to the orbiting wrap  11 . On the middle of the bearing plate  13 , a tubular boss  17  is projected to support an eccentric shaft  15  of a drive shaft  14  via a bearing  16 . On the outer portion of the bearing plate  13 , there are three crank-pin-type rotation prevention mechanisms  18  so that the orbiting scroll may revolve with respect to the housing  9 .  
         [0020]    Between the stationary scroll  1  and the orbiting scroll  8 , the center of the orbiting scroll  8  is eccentric to the center of the stationary scroll  1  and the drive shaft  14  by a distance corresponding to the eccentricity of the eccentric shaft  15  so that the orbiting wrap  11  of the orbiting scroll  8  may be engaged with the stationary wrap  6  of the stationary scroll  1  as shown in FIG. 2.  
         [0021]    A pressing plate  19  is engaged on the rear surface of the stationary scroll i and fastened by fastening screws  20 , and the rear surface of the orbiting scroll  8  is engaged on the front surface of the bearing plate  13  and fastened by fastening screws  21  to construct a scroll compressor.  
         [0022]    The drive shaft  14  is connected to a motor (not shown) outside the housing via a pulley and a V-shaped belt or directly connected to a motor (not shown) in the housing  9  so as to rotate in a predetermined direction by the motor.  
         [0023]    In the scroll compressor, there are a low-pressure pressurizing portion “A” in which winding of the stationary wrap  6  is finished outside the stationary scroll  1  and the orbiting scroll  8 ; and a high-pressure pressurizing portion “B” in which winding of the stationary wrap  6  begins inside the scrolls  1  and  8 . The low-pressure pressurizing portion “A” and the high-pressure pressurizing portion “B” are divided by an insulating wall  22  of the stationary wrap  6  to block a fluid path of a pressurized gas.  
         [0024]    The stationary end plate  5  includes first and second low-pressure-side outlets  23 ,  24  which communicate with the low-pressure pressurizing portion “A” of the stationary wrap  6  and penetrate axially; and a high-pressure inlet  25  which communicates with the high-pressure pressurizing portion “B” of the stationary wrap  6  and penetrates axially.  
         [0025]    The first low-pressure-side outlet  23  is formed by the insulating wall  22  at the innermost winding of the low-pressure pressurizing portion “A”, and the second low-pressure-side out let  24  is formed at outer portion than the first low-pressure outlet  23 .  
         [0026]    The low-pressure-side outlets  23 ,  24  are selectively closed by closure members  25  depending on the condition of use as shown in FIGS. 4 and 5. For example, when it is used at frequency of 50 Hz, the first low-pressure-side outlet  23  opens and the second low-pressure-side outlet  24  is closed by a closure member  26 . When it is used at frequency of 60 Hz, the second low-pressure-side outlet  24  opens and the first low-pressure-side outlet  23  is closed by a closure member  26 .  
         [0027]    One of the low-pressure-side outlets  23 ,  24 , which opens, Is connected to an entrance of an intermediate cooler  28  for cooling a pressurized gas, and the high-pressure-side inlet  25  is connected to an exit of the intermediate cooler  28  via a conduit  29 .  
         [0028]    As shown in FIG. 5, the closure member  26  has an external thread  26   a  which is engaged in an internal thread  24   a  of the low-pressure-side outlet  23 ,  24  to close the outlets  23 ,  23  completely. The closure member  26  can be engaged in low-pressure-side outlets  23 ,  24  without removing the stationary plate  5  from the outside of the scroll compressor. The external thread  26   a  of the closure member  26  has the same shape as a mounting portion of the conduit  27  connected to each of the low-pressure outlets  23 ,  24 .  
         [0029]    [0029]FIG. 6 shows that the second low-pressure outlet  24  is closed, and FIG. 7 b  shows that the first low-pressure-side outlet  23  is closed, relating to FIG. 2.  
         [0030]    When frequency of an alternating voltage applied to a motor is 50 Hz, the conduit  27  connected to the intermediate cooler  28  is connected to the first low-pressure-side outlet  23 , and the second low-pressure-side outlet  24  is closed by the closure member  26 . Thus, by revolving the orbiting scroll  8  by the motor, air taken in through the inlet  2  of the stationary scroll  1  is compressed gradually by a compression chamber formed between the stationary wrap  6  and the orbiting wrap  11  of the low pressure pressurizing portion “A”, and moved in an anti-clockwise direction or towards the center in FIG. 6.  
         [0031]    Air taken in through the inlet  2  is compressed to an amount corresponding to a volume of the compression chamber “C” formed between sealing points “a” and “a” at which the stationary wrap  6  contacts the orbiting wrap  11 , and discharged through the first low-pressure-side outlet  23  at the innermost winding of the low-pressure pressurizing portion “A”. After compression heat generated by compression is cooled by the intermediate cooler  28 , the air is sent from the high-pressure-side inlet  25  to the high-pressure pressurizing portion “B”, further compressed in the high-pressure pressurizing portion “B”, and finally discharged through the outlet  3  to an air tank.  
         [0032]    When the frequency is 60 Hz, the conduit  27  is connected to the second low-pressure outlet  24  and the first low-pressure outlet is closed by the closure member  26 . Thus, air taken in through the inlet  2  is compressed only to an amount corresponding to a volume of a compression chamber “D” that provides more volume than that of the compression chamber “C” as shown in FIG. 7 to reduce compression ratio compared with the operation of 50 Hz, thereby preventing overload even if the number of rotation of an AC electric motor becomes higher. That is to say, when the first low-pressure-side outlet  23  is closed, a sealing point “b” at which the stationary wrap  6  contacts the orbiting wrap  11  is outer than the sealing points “a”, “a”, the volume of the compression chamber “D” formed between the sealing points “b”, “b” becomes larger than the volume of the compression chamber “C” to reduce a compression ratio.  
         [0033]    [0033]FIGS. 8 and 9 show the second embodiment of the present invention. In the embodiment, a single low-pressure-side outlet  23  is formed in a low-pressure pressurizing portion “A”, and there are formed a high-pressure-side inlet  25  by an insulating wall  22  and another high-pressure-side inlet  25   a  inner than the inlet  25 .  
         [0034]    When frequency is 50 Hz, a conduit  29  is connected to the high-pressure-side inlet  25 , and the other high-pressure-side inlet  25   a  is closed by a closure member  26 . When frequency is 60 Hz, the conduit  29  is connected to the high-pressure-side inlet  25   a , the high-pressure-side inlet  25  is closed by the closure member  26 .  
         [0035]    Therefore, when the frequency is 50 Hz, compressed air discharged through the low-pressure-side outlet  23  is sent to a high-pressure pressurizing portion “B” through the high-pressure-side inlet  25 . As shown in FIG. 8, the air is gradually compressed by a compression chamber “E” formed between sealing points “c” and “c” at which the stationary scroll  6  contacts the orbiting scroll  1  in the high-pressure pressurizing portion “B”, moved in an anti-clockwise direction or towards the center and discharged through the outlet  3 .  
         [0036]    When the frequency is 60 Hz, compressed air discharged from the low-pressure-side outlet  23  is sent into the high-pressure pressurizing portion “B” through the high-pressure-side inlet  25   a . As shown in FIG. 9, the air is gradually compressed by a compression chamber “F” formed between sealing points “d” and “d” at which the stationary wrap  6  contacts the orbiting wrap  11  in the high-pressure pressurizing portion “B”, moved in an anti-clockwise direction or towards the center and discharged through the outlet  3 . In this case, the compression chamber “F” is inner than the compression chamber “E”, the volume of the compression chamber “F” becomes smaller than the volume of the compression chamber “E”, and the amount of the air taken into the high-pressure pressurizing portion “B” becomes smaller, thereby reducing compression ratio and preventing overload even if the number of rotation of an AC electric motor becomes higher.  
         [0037]    In the foregoing embodiments, the present invention is applied to a single-winding multi-stage scroll compressor in which the low-pressure pressurizing portion “A” is separated from the high-pressure pressurizing portion “B”, but may be applied to a single-winding single-stage scroll compressor in which a low-pressure pressurizing portion “A” and a high-pressure pressurizing portion “B” are continuously formed.  
         [0038]    In this case, without low-pressure-side outlet or high-pressure-side inlet, another outlet is formed outer than the outlet  2 . In case of 50 Hz, the outlet  2  is connected to an air tank and the other outlet is closed by a closure member  26 . In case of 60 Hz, the other outlet is connected to an air tank, and the outlet  2  is closed by a closure member  26 .  
         [0039]    The present invention is applied not only to a scroll compressor, but also to any other scroll-type fluid machines. The invention can be also applied to an oil-filling scroll-type fluid machine as well as the oil-free scroll-type fluid machine as above.  
         [0040]    According to the present invention, compression ratio is changeable depending on the condition of use. Overloading can be prevented without replacement of parts.  
         [0041]    The foregoing merely relates to embodiments of the invention. Various modifications and changes may be made by a person skilled in the art without departing from the scope of claims wherein: