Patent Publication Number: US-7722341-B2

Title: Scroll compressor having variable height scroll

Description:
This claims priority to Korean Application No. 10-2006-0021469, filed in Korea on Mar. 7, 2006, the entirety of which is incorporated herein by reference. 
   BACKGROUND 
   1. Field 
   This relates to a compressor, and more particularly, to a scroll compressor. 
   2. Background 
   Compressors convert mechanical energy into compressive energy. Compressors may be classified into a variety of different types, including, for example, reciprocating, scroll, centrifugal and vane types. Scroll compressors may be further classified into low pressure and high pressure types, based on whether a suction gas or a discharge gas is filled in a casing thereof. In a scroll compressor, two scrolls perform a relative orbiting motion, and a pair of substantially symmetrical compression chambers are formed between the two scrolls. As the compression chambers consecutively move towards a center of the scroll, a volume of the compression chamber is decreased, thus compressing a refrigerant held therein. The pair of compression chambers may include a high pressure side compression chamber and a low pressure side compression chamber. In some instances, refrigerant inside the high pressure side compression chamber may leak into the low pressure side compression chamber, thus degrading performance of the compressor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
       FIG. 1  is a sectional view of an exemplary high pressure type scroll compressor; 
       FIG. 2  is a sectional view of an orbiting scroll of the exemplary compressor shown in  FIG. 1 ; 
       FIG. 3  is a sectional view of an exemplary high pressure type scroll compressor in accordance with embodiments as broadly described herein; 
       FIG. 4  is a sectional view of an orbiting scroll of the exemplary compressor shown in  FIG. 3 ; 
       FIG. 5  is a graph of a height of the orbiting scroll shown in  FIG. 4 ; 
       FIGS. 6-8  are cross sectional views of the orbiting scroll shown in  FIG. 4  relative to a fixed scroll during operation of the exemplary compressor shown in  FIG. 3  in accordance with embodiments as broadly described herein; 
       FIGS. 9 and 10  are sectional views of another exemplary scroll compressor in accordance with another embodiment as broadly described herein; and 
       FIGS. 11-13  illustrate exemplary installations of a compressor as embodied and broadly described herein. 
   

   DETAILED DESCRIPTION 
   The exemplary high pressure type scroll compressor shown in  FIG. 1  may include a casing  10  that forms a hermetic inner space, and a main frame  20  and a sub frame  30  fixed to upper and lower sides of the casing  10 , respectively. A driving motor  40  may be provided between the main frame  20  and the sub frame  30  to generate a rotation force. A fixed scroll  50  may be fixed to an upper surface of the main frame  20  so as to communicate with a gas suction pipe SP. An orbiting scroll  60  having an involute wrap  62  may perform an orbiting motion through its inter-engagement with a wrap  52  of the fixed scroll  50  so that a plurality of paired compression chambers P are formed. An Oldham&#39;s ring  70  may be disposed between the orbiting scroll  60  and the main frame  20 , and orbits the orbiting scroll  60 . A shaft hole  22 , a boss portion receiving groove  22 , and a back pressure groove  23  may also be formed in the main frame  20 . An inlet  53  and an outlet  54  may be formed in the fixed scroll  50 , and a boss portion  63  may be formed in the orbiting scroll. 
   When power is supplied to a winding coil  80  of the driving motor  40 , a driving shaft  43  is rotated together with a rotor  42 , and the orbiting scroll  60  performs an orbiting motion at an upper surface of the main frame  20 . The engagement of the wraps  52  and  62  forms a pair of compression chambers P that progressively move towards the center of the scroll as the orbiting scroll  60  orbits, with a volume decreasing as they approach the center, thereby compressing a refrigerant in the compression space P. 
   A lower surface of a plate  61  of the orbiting scroll  60  is disposed on an upper surface of the main frame  20 , thus forming a lower side thrust bearing surface (TS). An outer circumferential surface of an upper surface of the plate  61  comes in contact with a lower surface of a plate  51  of the fixed scroll  50 , thus forming an upper side thrust bearing surface (TS). The lower surface of the plate  51  of the fixed scroll  50  contacts the end of the wrap  62  of the orbiting scroll  60 , and the end of the wrap  52  of the fixed scroll  50  contacts the upper surface of the plate  61  of the orbiting scroll  60 , thereby preventing a refrigerant inside the high pressure side compression chamber from leaking into the lower pressure side compression chamber. 
   As shown in  FIG. 2 , the plate  61  of the orbiting scroll  60  has the same height H along sections A, B and C. When manufacturing tolerances of the fixed scroll  50  and the orbiting scroll  60  are imprecise, or the wrap ends are abraded due to extended usage, a gap is generated between each wrap end of the fixed scroll  50  and the orbiting scroll  60  and the corresponding plates  51 ,  61  which they contact. Accordingly, refrigerant may leak from the high pressure side compression chamber to the low pressure side compression chamber, thereby degrading performance of the compressor. 
     FIG. 3  is a sectional view of an exemplary high pressure type scroll compressor, and  FIGS. 4 and 5  are respectively a sectional view and a graph showing a height of the orbiting scroll at various locations or positions thereof. 
   The exemplary high pressure type scroll compressor shown in  FIG. 3  may include a casing  110  that forms a hermetic inner space, and a main frame  120  and a sub frame (shown in  FIG. 1 ) fixed to upper and lower sides of the inner space of the casing  110 . A fixed scroll  150  may be coupled to an upper surface of the main frame  120  so as to communicate with a gas suction pipe SP. An orbiting scroll  160  having an involute wrap  162  may perform an orbiting motion by being engaged with a wrap  152  of the fixed scroll  150  so that a plurality of paired compression chambers P may be formed. An Oldham&#39;s ring  170  may be disposed between the orbiting scroll  160  and the main frame  120  so as to prevent the orbiting scroll  160  from rotating. A driving motor  140  including a stator  141  and a rotor  142  may be provided in the casing  110  to generate a rotational force. 
   The main frame  120  may include a shaft hole  121  at a center thereof for supporting a driving shaft  143 . A boss portion receiving groove  122  which allows for orbiting motion of a boss portion  163  of the orbiting scroll  160  may be formed at an upper end of the shaft hole  121 . A back pressure groove  123  may be formed as a recess with a predetermined depth at an edge of an upper surface of the main frame  120 . The back pressure groove  123  may define an inner volume together with a rear surface of the orbiting scroll  160 , and may have a ring shape so that refrigerant gas of a middle pressure may be contained within this inner volume. 
   The involute wrap  152  of the fixed scroll may have the same height and width as that of the involute wrap  162  of the orbiting scroll  160  so that a pair of compression chambers P may be formed between a lower surface of the plate  151 , an upper surface of the plate  161 , and the wraps  152 ,  162 . An inlet  153  to receive the gas suction pipe SP may be disposed at one side of the plate  151 , and an outlet  154  may be disposed at the center of the plate  151  so as to discharge compressed refrigerant from a final compression chamber into the casing  110 . A lower surface of the plate  151  of the fixed scroll  150  may be disposed on the same plane as the end of the wrap  152  so that an outer surface thereof may form a thrust bearing surface (TS) together with an upper surface of the plate  161  of the orbiting scroll  160 . 
   As set forth above, the involute wrap  162  is provided at an upper surface of the plate  161 , the wrap  162  having the same height and width as that of the wrap  152  and performing an orbiting motion through its engagement with the wrap  152  of the fixed scroll  150 . This allows an inner volume of the compression chamber P to be progressively decreased towards a center of the scroll. 
   As shown in  FIG. 4 , the upper surface of the plate  161  of the orbiting scroll  160  has different heights based on a radial position on the plate  161 . As shown in  FIGS. 4 and 5 , among the respective portions of the upper surface of the plate  161  of the orbiting scroll  160 , the outermost compression chamber A may have a largest overall volume and a highest height (H A ). Likewise, the final compression chamber B positioned at a middle portion of the compression chamber P of the orbiting scroll  160  may have a smallest overall volume and a height (H B ) lower than the height H A . In certain embodiments, a difference between the height (H A ) of the outermost compression chamber A and the height (H B ) of the final compression chamber B may be approximately in a range of approximately 5/10000˜ 10/10000 of the wrap height, based on thermal expansion characteristics due to temperature differences in the wrap during operation. 
   A portion C of the plate  161  of the orbiting scroll  160  outside the compression chamber P may have a height (H C ) between the height (H A ) of the outermost compression chamber A and the height (H B ) of the final compression chamber B. Accordingly, excessive leakage of a refrigerant through the thrust bearing surface (FS) formed between the fixed scroll  150  and the orbiting scroll  160 , and between the wrap  152  and the wrap  162 , may be prevented. In certain embodiments, the difference between the height (H A ) of the outermost compression chamber A and the height (H C ) of the portion C of the plate  161  outside the compression chamber may be in a range of approximately 0.003˜0.03 mm, and, in alternative embodiments, may be less than or equal to or less than approximately 0.02 mm. 
   It is noted that the term “height” as used herein may describe an overall distance from an uppermost surface of one of the scrolls to its lowermost surface at a particular radial position, when shown in cross section. Likewise, this term may also be used to describe a thickness of one of the plates, measured from an uppermost surface to a corresponding lowermost surface at a particular position when shown in cross section. Similarly, this term may also be used to describe a length of one of the wraps, measured from a distal end to an opposite end adjacent its corresponding plate when shown in cross section. 
   Operation of the high pressure type scroll compressor in accordance with embodiments as broadly described herein will now be explained. 
   When power is supplied to a coil  80  of the driving motor  140 , the driving shaft  143  rotates, causing the orbiting scroll  160  to orbit a predetermined eccentric distance. While the orbiting scroll  160  progressively moves within the fixed scroll  150 , a plurality of paired compression chambers P having decreased volumes towards the center of the scrolls are formed. A refrigerant is sucked into the scrolls, compressed in the chambers, and discharged through the outlet  154  into the casing  110 . This process is continuously repeated. 
   In order for the compressor to generate a desired cooling capacity, manufacturing tolerances of the fixed scroll  150  and the orbiting scroll  160  should be precise so that the wrap  152  of the fixed scroll  150  and the wrap  162  of the orbiting scroll  160  make necessary contact with the respective surfaces of the plates  151  and  161 . However, such precise control of manufacturing tolerances increases fabrication cost. Further, over time, the wrap  152  of the fixed scroll  150  and the wrap  162  of the orbiting scroll  160  may be abraded due to continuous operation of the compressor, thus generating a gap through which refrigerant may leak from the high pressure side compression chamber to the low pressure side compression chamber. 
   To address this problem, as shown in  FIGS. 3-5 , the bottom surface of the plate  161  of the outermost compression chamber A of the orbiting scroll  160  that forms a suction side first contacts the wrap  152  of the fixed scroll  150  at the time of an initial driving of the compressor, thereby preventing a refrigerant from leaking. Then, the refrigerant is compressed in the compression chamber. Accordingly, even if the manufacturing of the fixed scroll  150  and the orbiting scroll  160  is imprecise or the compressor is used for a long time, refrigerant leakage in a shaft direction is prevented. 
   As shown in  FIG. 6 , at the time of the initial driving of the compressor, only the bottom surface of the outermost compression chamber A (formed by the plate  161  of the orbiting scroll  160 ) makes close contact with the end of the outermost wrap  152   a  of the fixed scroll  150 , thereby sealing the outermost compression chamber A. As shown in  FIG. 7 , as the outermost wrap  152   a  of the fixed scroll  150  contacts the bottom surface of the outermost compression chamber A during operation, the end of the outermost wrap  152  may be abraded. 
   To address this problem, a discharge pressure may be applied to the center of a lower surface of the plate  161  by oil sucked through the driving shaft  143 , and a mid-level pressure may be applied to an outer portion of a lower surface of the plate  161  that forms a portion of the back pressure groove  123 . In contrast, the center of an upper surface of the plate  161  may be supplied with a discharge pressure at the final compression chamber B, and an outer upper surface of the plate  161  may be supplied with a suction pressure by a refrigerant sucked through the inlet  153 . 
   More specifically, because the plate  151  is fixed, and the plate  161  is not fixed, the plate  161  may be shifted in a shaft direction by this pressure difference. At the time of initial driving of the compressor, the pressures at upper and lower sides of the plate  161  are similar to each other. During operation, the pressure of the lower side of the plate  161  is higher than that of the upper side because the lower side of the plate  161  is divided into a high pressure portion  122  and a middle pressure portion  123  which are sealed from one another. These pressure differentials cause the upper surface of the plate  161  positioned outside the wrap  162  of the orbiting scroll  160  to contact the lower surface of the plate  151  positioned outside the suction chamber of the fixed scroll  150 , thereby forming a thrust bearing surface (TS) therebetween and preventing abrasion of the outermost wrap  152   a  and subsequent leakage of refrigerant. 
   As shown in  FIG. 8 , the final compression chamber B experiences an increased pressure and temperature during operation. As a result, the final wrap  152   b  and the wrap  162  may be thermally expanded, causing the final wrap  152   b  to contact the lower surface of the final chamber B (formed by the upper surface of the plate  161  of the wrap  162 /scroll  160 ). In certain embodiments, a portion of the plate  161  within the chamber A may be worn away, causing the plate  161  to shift upward due to the difference in pressure and the thrust surfaces TS to come into contact with each other. Thus, even if each end of the wraps  162  and  152   b  contact the corresponding plate  151  and  161  during operation, as shown in  FIG. 7 , each end of the wraps  162  and  152   b  is thermally expanded by compression heat during operation, as shown in  FIG. 8 . Accordingly, refrigerant leakage from the final compression chamber B to the outer compression chamber, which has a lower pressure than the final compression chamber B, may be prevented. 
   A scroll compressor in accordance with a second embodiment will now be explained. In the scroll compressor of the first embodiment, the thickness of the orbiting scroll  160 , and in particular, a thickness of the plate  161  and/or a length(s) of the wrap  162 , may vary. However, in the scroll compressor shown in  FIG. 9 , the thickness of the orbiting scroll  160 , and in particular, the length(s) of the wrap  162 , is substantially uniform, regardless of a radial position along the plate  161 . In contrast, the thickness of the fixed scroll  150 , and in particular the thickness of the plate  151  and/or a length(s) of the wrap  152 , varies based on a radial position along the plate  151 . 
   A scroll compressor in accordance with a third embodiment is shown in  FIG. 10 . In the third embodiment, both the wrap  152  of the fixed scroll  150  and the wrap  162  of the orbiting scroll  160  have different lengths, each based on a radial position along the respective scroll position. Although not shown in detail, it is possible to construct the wrap  152  of the fixed scroll  150  or the wrap  162  of the orbiting scroll  160  with different heights based on such a position. 
   In the second embodiment shown in  FIG. 9 , the wrap  152  of the fixed scroll  150  extends to a length of the plate  151  outside the wrap  152  of the scroll  150  that forms a thrust bearing surface (TS). However, portions of the fixed scroll  150  may have different heights, and in particular, the length(s) of the wrap  152  may differ, based on a radial position along the plate  151 . For example, as shown in  FIG. 9 , the height of the plate  151  of the fixed scroll  150  may be highest at the middle compression chamber A, and may be the same at right and left compression chambers B and C. In certain embodiments, height difference (t 2 ) of the plate  151  between the middle compression chamber A and the right and left compression chambers B and C may be equal to or larger than a gap (t 1 ) between the plate  161  of the orbiting scroll  160  and the plate  151  outside the wrap  152  of the fixed scroll  150 . Other combinations of heights for the compression chambers A, B and C may also be appropriate. 
   In the third embodiment shown in  FIG. 10 , the plate  151  of the fixed scroll  150  and the plate  161  of the orbiting scroll  160  have substantially the same height. However, the wrap  152  of the fixed scroll  150  has different heights based on a radial position. For example, the height of the wrap  152  of the fixed scroll  150  may be highest at the middle compression chamber A the inner compression chamber B, and lower at the compression chamber C. A gap (t 2 ) between the compression side of the plate  151  of the fixed scroll  150  and the end of the wrap  162  of the orbiting scroll  160  may be greater than or equal to a gap (t 1 ) between the plate  161  of the orbiting scroll  160  and the plate  151  outside the compression chamber of the fixed scroll  150  that forms a thrust bearing surface (TS). In certain embodiments, only the wrap  162  of the orbiting scroll  160  may have different heights, or both the wrap  152  of the fixed scroll  150  and the wrap  162  of the orbiting scroll  160  may have different heights. The height difference between the wraps may be as set forth with respect to the first embodiment. Other differences in height may also be appropriate. 
   Referring to  FIGS. 9 and 10 , ‘t 1 ’ denotes a gap between the fixed scroll  150  and the orbiting scroll  160  at the time of a second contact with each other, and ‘t 2 ’ denotes a gap therebetween at the time of a third contact with each other. Details thereof are based on the sequence shown in  FIGS. 6 to 8 . An effect of the scroll compressor according to the second and third embodiments is similar to that set forth with respect to the first embodiment, and thus further detailed explanation is omitted. 
   As the wrap of each of the scrolls or the plates may have different heights, a gap between the end of the wrap and the opposite plate can be prevented even if control of tolerances during manufacturing of the fixed scroll  150  and the orbiting scroll  160  is imprecise or the compressor is operated for an extended period of time. Accordingly, performance of the compressor may be enhanced. 
   Furthermore, even when an edge of the plate of the orbiting scroll is bent due to different pressures applied thereto, excessive contact and/or friction between the thrust bearing surface of the orbiting scroll and the thrust bearing surface of the fixed scroll may be avoided. This may prevent a frictional loss due to an increase in frictional area. Since the thrust bearing surface serves as a lever, refrigerant leakage due to separation between the end of the wrap and the opposite plate may be prevented. 
   The scroll configuration for a scroll compressor as embodied and broadly described herein has numerous applications in which compression of fluids is required. Such applications may include, for example, air conditioning and refrigeration applications. One such exemplary application is shown in  FIG. 11 , in which a compressor  1110  as embodied and broadly described herein is installed in a refrigerator/freezer  1100 . Installation and functionality of a compressor in this type of refrigerator is discussed in detail in U.S. Pat. Nos. 7,082,776, 6,995,064, 7,114,345, 7,055,338 and 6,772,601, the entirety of which are incorporated herein by reference. 
   Another such exemplary application is shown in  FIG. 12 , in which a compressor  1210  as embodied and broadly described herein is installed in an outdoor unit of an air conditioner  1200 . Installation and functionality of a compressor in this type of air conditioner is discussed in detail in U.S. Pat. Nos. 7,121,106, 6,868,681, 5,775,120, 6,374,492, 6,962,058, 6,951,628 and 5,947,373, the entirety of which are incorporated herein by reference. 
   Another such exemplary application is shown in  FIG. 13 , in which a compressor  1310  as embodied and broadly described herein is installed in a single, integrated air conditioning unit  1300 . Installation and functionality of a compressor in this type of air conditioner is discussed in detail in U.S. Pat. Nos. 7,032,404, 6,412,298, 7,036,331, 6,588,288, 6,182,460 and 5,775,123, the entirety of which are incorporated herein by reference. 
   An object is to provide a scroll compressor capable of preventing a refrigerant from being leaked between each wrap end of a fixed scroll and an orbiting scroll and a plate even if the fixed scroll and the orbiting scroll have a low processing precision or each wrap end thereof is abraded. 
   To achieve these and other advantages and in accordance with the purpose of embodiments broadly described herein, there is provided a scroll compressor, including a frame fixedly-coupled to inside of a casing, a fixed scroll fixedly-coupled to the frame, and having a wrap at a lower surface of a plate, and an orbiting scroll having a wrap at an upper surface of the plate, and performing an orbiting motion by being engaged with the wrap of the fixed scroll so that a compression chamber may have a decreased volume, wherein the plate or the wrap of at least one of the fixed scroll and the orbiting scroll has different heights according to each position. 
   To achieve these and other advantages and in accordance with the purpose of embodiments broadly described herein, there is provided a scroll compressor, including a frame fixedly-coupled to inside of a casing, a fixed scroll fixedly-coupled to the frame, and having a wrap at a lower surface of a plate, and an orbiting scroll having a wrap at an upper surface of the plate, and performing an orbiting motion by being engaged with the wrap of the fixed scroll so that a compression chamber may have a decreased volume, wherein a wrap of at least one of the fixed scroll or the orbiting scroll has different heights according to each position. 
   Any reference in this specification to “one embodiment,” “an exemplary,” “example embodiment,” “certain embodiment,” “alternative embodiment,” and the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment as broadly described herein. 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 embodiments, 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. 
   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, numerous 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.