Abstract:
Compressors are defined by two relatively moving members, which have a relative orbital movement between the two. Piezoelectric elements are associated with each of the two moving members to cause the moving members to result in the orbital movement.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a compressor, wherein piezoelectric elements are actuated to control orbiting movement of the members in the compressor. 
         [0002]    Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor, a first scroll member has a base and a generally spiral wrap extending from its base. A second scroll member has a base and a generally spiral wrap extending from its base. The two wraps interfit to define compression chambers. In standard scroll compressors, an electric motor drives a shaft to in turn cause one of the two scroll members to orbit relative to the other. As the two scroll members orbit, the compression chambers between the wraps decrease in size, and an entrapped refrigerant is compressed. 
         [0003]    Another type of compressor that is utilized in refrigerant compression applications is a rotary compressor. In a rotary compressor, a housing surrounds a rotor, and a vane contacts the rotor, and moves inwardly and outwardly of the housing. The rotor and the housing are caused to orbit relative to each other, and an entrapped refrigerant is compressed during this orbiting movement. 
         [0004]    There has been some effort proposed to provide alternative drives for at least scroll compressors. Thus, in one prior patent, a piezoelectric drive is proposed, which moves a scroll member through a complex back and forth movement to achieve the compression. While piezoelectric drive elements would be beneficial in reducing the size of the compressor, and also reducing the number of drive components, the proposed drive is complex, and impractical. 
       SUMMARY OF THE INVENTION 
       [0005]    In the disclosed embodiment of this invention, compressor members are provided with opposed piezoelectric elements. A control selectively actuates the piezoelectric elements to expand and contract. 
         [0006]    In a scroll compressor embodiment, the expansion and contraction, the scroll members are caused to move in a linear fashion. In a disclosed embodiment, there are opposed piezoelectric elements associated with each of an orbiting and a non-orbiting scroll. The two members are caused to move in controlled cycles, such that the overall relative movement is an orbiting movement to entrap and compress a refrigerant. 
         [0007]    This embodiment provides a very simple method of driving the scroll members, and further provides a very powerful technique for achieving a orbiting cycle which is exactly as desired. By properly controlling the movement of the two scroll members, any orbiting movement can be achieved. The orbit can be elliptical, square, etc. Further, by simply changing the frequency of the cycles, a designer is able to easily increase or decrease capacity of the scroll compressor. 
         [0008]    In disclosed embodiments, each of the two scroll members are driven along a sinusoidal wave cycle. 
         [0009]    In a second disclosed embodiment, the piezoelectric elements drive a rotor and a housing for a rotary compressor. Again, by controlling the movement of the two elements, any orbiting movement can be achieved. 
         [0010]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a view of a scroll compressor incorporating the inventive drive. 
           [0012]      FIG. 2  is a cross-sectional view along line  2 - 2  of  FIG. 1 . 
           [0013]      FIG. 3  shows drive cycles for the inventive scroll compressor. 
           [0014]      FIG. 4  shows a second embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    A scroll compressor  20  is illustrated in  FIG. 1 . As known, a first scroll  22  includes a base and a generally spiral wrap  24  extending from that base. A second scroll  26  has a base and a spiral wrap  28  extending from its base. The two wraps interfit to define compression chambers, as known. A refrigerant to be compressed enters through a suction tube  30 , and flows into the compression chambers between the wraps  24  and  28 . The refrigerant is compressed as the two wraps orbit relative to each other, and deliver outwardly through a discharge port  32 . 
         [0016]    As shown in  FIG. 1 , piezoelectric elements  34  are associated with the base of the first scroll  22 , and piezoelectric elements  36  are associated with the second scroll member  26 . 
         [0017]    As shown in  FIG. 2 , the piezoelectric elements  36  are mounted at opposed sides of the base of the second scroll member  26 . The piezoelectric elements  34  are mounted in a similar fashion on scroll member  22 . Some guiding structure may be included to ensure the movement of the second scroll member  26  is generally linear, and along an X axis, and that the movement of the first scroll member  22  is also linear, and along a Y axis as shown in  FIG. 2 . The discharge port  40  receives the compressed refrigerant, and delivers it downstream to the discharge port  32 . 
         [0018]    As shown in  FIG. 3 , the second scroll member  26  may be driven along a sinusoidal cycle and in the X direction. Similarly, the first scroll member  22  can be driven along the Y axis in a sinusoidal cycle. As shown, the two cycles can be offset by 90°. The resultant overall relative movement can be as shown in the bottom chart of  FIG. 3 , and thus the resultant movement can be an orbital movement. 
         [0019]    A designer of a control  100  for the scroll compressor  20  would recognize that the inventive drive arrangement provides a powerful tool for achieving many beneficial characteristics. As can example, by simply changing the cycle frequency of the actuation of the piezoelectric elements, varying capacity can be easily achieved. In the past, varying capacity has typically required very complex structure. The present invention provides varying capacity with the simple piezoelectric drive elements. 
         [0020]    In addition, an exactly tailored relative orbital movement can be easily achieved by properly controlling the timing and magnitude of the movement of the scroll member  22  and  26 . 
         [0021]      FIG. 4  shows another embodiment  130 , which is a rotary compressor. In this rotary compressor, a housing  140  surrounds a rotor  142 . The rotor  142  includes a driveshaft (not shown), which is driven by piezoelectric elements  134 . A second set of piezoelectric elements  136  drive the housing  140 . In a fashion similar to that mentioned above with regard to the scroll compressor embodiment, the orbital movement of the elements  140  and  142  can be controlled to achieve any desired cycle. As known, a vane  144  contacts the outer periphery of the rotor  142 , to define compression chambers that decrease in volume as the rotor  142  orbits. As shown in this figure, the rotor  142  can actually be caused to move generally linearly upwardly and downwardly in this figure while the housing moves left to right in this figure. The combination of the two movements can achieve an orbital movement. 
         [0022]    A worker of ordinary skill in the art would recognize the various modifications and movements which can be achieved with the present invention. 
         [0023]    While a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.