Patent Publication Number: US-9897088-B2

Title: Scroll compressor with back pressure chamber having leakage channel

Description:
This application is the national phase of International Application No. PCT/CN2013/086182, titled “SCROLL COMPRESSOR” and filed on Oct. 30, 2013, which claims priority from Chinese Patent Application No. 201310020858.X titled “SCROLL COMPRESSOR” and filed with the Chinese State Intellectual Property Office on Jan. 21, 2013, and Chinese Patent Application No. 201320037041.9 titled “SCROLL COMPRESSOR” and filed with the Chinese State Intellectual Property Office on Jan. 21, 2013. The entire disclosures of the Chinese Patent Applications are incorporated herein by reference. 
     FIELD 
     The present application relates to a scroll compressor. 
     BACKGROUND 
     The contents in this section only provide background information relating to the present disclosures which does not necessarily constitute the prior art. 
     A scroll compressor generally includes a compression mechanism constituted by a non-orbiting scroll component and an orbiting scroll component. Typically, an end plate of the non-orbiting scroll component is formed thereon with a concave portion and a seal assembly is provided in the concave portion. The concave portion is in fluid communication with one of a series of compression chambers formed between the non-orbiting scroll component and the orbiting scroll component. The seal assembly is fitted in the concave portion to form a back pressure chamber which provides back pressure to the non-orbiting scroll component. In the cases that the scroll compressor works in different working conditions, sealing requirements for the seal assembly are also different. Therefore, there remains room for further improvement in the seal assembly. 
     SUMMARY 
     A scroll compressor is provided according to one aspect of the embodiments of the present application. The scroll compressor includes an orbiting scroll component, a non-orbiting scroll component, a seal assembly and a leakage channel. The orbiting scroll component includes an orbiting scroll end plate, and a spiral orbiting scroll vane formed at one side of the orbiting scroll end plate. The non-orbiting scroll component includes a non-orbiting scroll end plate, a spiral non-orbiting scroll vane formed at one side of the non-orbiting scroll end plate, and a concave portion formed at the other side of the non-orbiting scroll end plate. The concave portion is in fluid communication with one of a series of compression chambers formed between the orbiting scroll vane and the non-orbiting scroll vane via a medium pressure channel. The seal assembly is fitted with the concave portion to jointly form a back pressure chamber, and is configured to separate the back pressure chamber from a high-pressure side and a low-pressure side in the scroll compressor. The leakage channel is configured to allow fluid in the back pressure chamber to leak. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features and advantages of one or more embodiments of the present application can be understood more readily from the following description made with reference to drawings in which: 
         FIG. 1A  is a longitudinal sectional view of a conventional scroll compressor; 
         FIG. 1B  is an exploded view of a single-layer seal assembly shown in  FIG. 1A ; 
         FIG. 2A  is a sectional view of a double-layer seal assembly; 
         FIG. 2B  is an exploded view of the double-layer seal assembly shown in  FIG. 2A ; 
         FIG. 3A  is a sectional view of a seal assembly according to a first embodiment of the present application; 
         FIG. 3B  is an exploded view of the seal assembly shown in  FIG. 3A ; 
         FIG. 4A  is a sectional view of a seal assembly according to a second embodiment of the present application; 
         FIG. 4B  is an exploded view of the seal assembly shown in  FIG. 4A ; 
         FIG. 5A  is a sectional view of a seal assembly according to a third embodiment of the present application; 
         FIG. 5B  is an exploded view of the seal assembly shown in  FIG. 5A ; 
         FIG. 6A  is a sectional view of a seal assembly according to a fourth embodiment of the present application; 
         FIG. 6B  is an exploded view of the seal assembly shown in  FIG. 6A ; 
         FIG. 7A  is a sectional view of a fifth embodiment of the present application; 
         FIG. 7B  is an exploded view of the assembly shown in  FIG. 7A ; 
         FIG. 8A  is a sectional view of a seal assembly according to a sixth embodiment of the present application; and 
         FIG. 8B  is a partially enlarged view of part B in  FIG. 8A . 
     
    
    
     DETAILED DESCRIPTION 
     The following description of various embodiments of the application is only illustrative rather than a limitation to the present application and use or usage thereof. Throughout the figures, the like reference signs are used to indicate the like elements and thus the description of the like elements will not be repeated. 
     First, the general configuration and operation principle of the scroll compressor are described with reference to  FIG. 1A . As shown in  FIG. 1A , the scroll compressor  100  (sometimes referred to as compressor hereinafter) generally includes a housing  110 . The housing  110  may include a substantially cylindrical body  111 , a top cover  112  arranged at one end of the body  111 , a bottom cover  114  provided at the other end of the body  111 , and a separator  116  arranged between the top cover  112  and the body  111  to separate an inner space of the compressor into a high-pressure side and a low-pressure side. The space between the separator  116  and the top cover  112  constitutes the high-pressure side, and the space among the separator  116 , the body  111  and the bottom cover  114  constitutes the low-pressure side. An intake connector  118  configured to suck fluid is provided at the low-pressure side, and an outlet connector  119  configured to discharge the compressed fluid is provided at the high-pressure side. A motor  120  constituted by a stator  122  and a rotor  124  is arranged in the housing  110 . A drive shaft  130  is arranged in the rotor  124  to drive a compression mechanism constituted by the non-orbiting scroll component  150  and the orbiting scroll component  160 . The orbiting scroll component  160  includes an end plate  164 , a hub  162  formed at one side of the end plate, and a spiral vane  166  formed at the other side of the end plate. The non-orbiting scroll component  150  includes an end plate  154 , a spiral vane  156  formed at one side of the end plate, and a concave portion  158  formed at the other side of the end plate. A discharge port  152  is formed at a substantially center position of the end plate. The space around the discharge port  152  also constitutes a high-pressure side. A series of compression chambers C 1 , C 2  and C 3  with the volume gradually decreased from the radially outer side to the radially inner side are formed between the spiral vane  156  of the non-orbiting scroll  150  and the spiral vane  166  of the orbiting scroll  160 . The radially outermost compression chamber C 1  is at an intake pressure, and the radially innermost compression chamber C 3  is at a discharge pressure. The compression chamber C 2  in the middle is at a pressure between the intake pressure and the discharge pressure, and thus is also referred to as a medium pressure chamber. 
     The orbiting scroll component  160  is supported at one side by an upper portion (i.e. a support portion) of a main bearing housing  140 , and one end of the drive shaft  130  is supported by a main bearing  144  arranged in the main bearing housing  140 . One end of the drive shaft  130  is provided with an eccentric crank pin  132 , and an unloading liner  142  is provided between the eccentric crank pin  132  and the hub  162  of the orbiting scroll component  160 . Driven by a motor  120 , the orbiting scroll component  160  orbits relative to the non-orbiting scroll component  150  (i.e., the central axis of the orbiting scroll component  160  rotates about the central axis of the non-orbiting scroll component  150 , but the orbiting scroll component  160  itself may not rotate about its own central axis) to achieve compression of the fluid. The orbiting is achieved by an Oldham ring  190  arranged between the non-orbiting scroll component  150  and the orbiting scroll component  160 . The fluid compressed by the non-orbiting scroll component  150  and the orbiting scroll component  160  is discharged to the high-pressure side via the discharge port  152 . In order to prevent the fluid at the high-pressure side from back flowing to the low-pressure side via the discharge port  152  in a particular case, a one-way valve or a discharge valve  170  may be provided at the discharge port  152 . 
     In order to achieve compression of the fluid, an effective sealing is required between the non-orbiting scroll component  150  and the orbiting scroll component  160 . 
     On the one hand, axial sealing is required between a top end of the spiral vane  156  of the non-orbiting scroll component  150  and the end plate  164  of the orbiting scroll component  160  and between a top end of the spiral vane  166  of the orbiting scroll component  160  and the end plate  154  of the non-orbiting scroll component  150 . Typically, a seal assembly S is provided in the concave portion  158  of the non-orbiting scroll component  150 . That is, the seal assembly S is arranged between the separator  116  and the non-orbiting scroll component  150 . The concave portion  158  is in fluid communication with one of the series of compression chambers C 1 , C 2 , C 3  via a through hole  155  (also referred to as a medium pressure channel) formed in the non-orbiting scroll end plate  154 . Preferably, the concave portion  158  is in fluid communication with the compression chamber C 2  in the middle via the through hole  155 . Thus, the seal assembly S is fitted with the concave portion  158  to jointly form a back pressure chamber BC which provides back pressure to the orbiting scroll component  150 . The axial displacement of the seal assembly S is limited by the separator  116 . Since the orbiting scroll component  160  is supported at one side by the support portion of the main bearing housing  140 , the non-orbiting scroll component  150  and the orbiting scroll component  160  may be effectively pressed together by the pressure in the back pressure chamber BC. In the case that the pressures in various compression chambers exceed a set value, the resultant force generated by the pressures in these compression chambers will exceed a pressing downward force provided in the back pressure chamber BC, thus allowing the non-orbiting scroll component  150  to move upwards. At this time, the fluid in the compression chambers will leak to the low-pressure side via a gap between the top end of the spiral vane  156  of the non-orbiting scroll component  150  and the end plate  164  of the orbiting scroll component  160  and a gap between the top end of the spiral vane  166  of the orbiting scroll component  160  and the end plate  154  of the non-orbiting scroll component  150  to achieve unloading, thereby providing an axial compliance to the scroll compressor. 
     On the other hand, radial sealing is further required between a side surface of the spiral vane  156  of the non-orbiting scroll component  150  and a side surface of the spiral vane  166  of the orbiting scroll component  160 . The radial sealing between the both is typically achieved by means of a centrifugal force of the orbiting scroll component  160  during operation, and a driving force provided by the drive shaft  130 . Specifically, in operation, driven by the motor  120 , the orbiting scroll component  160  will orbit relative to the non-orbiting scroll component  150 , so that the orbiting scroll component  160  will generate a centrifugal force. Further, the eccentric crank pin  132  of the drive shaft  130  will also produce, during rotation, a driving force component to facilitate the radial sealing between the non-orbiting scroll component and orbiting scroll component. The spiral vane  166  of the orbiting scroll component  160  will abut against the spiral vane  156  of the non-orbiting scroll component  150  by means of the above centrifugal force and driving force component, thus achieving the radial sealing between the spiral vane  166  of the orbiting scroll component  160  and the spiral vane  156  of the non-orbiting scroll component  150 . When an incompressible matter (such as solid impurities, lubricant and liquid refrigerant) enters into the compression chamber and is stuck between the spiral vane  156  and the spiral vane  166 , the spiral vane  156  and the spiral vane  166  can apart from each other temporarily in the radial direction so as to allow the foreign matters to pass therethrough, thus preventing the spiral vane  156  or the spiral vane  166  from being damaged. The capability of moving apart radially provides a radial compliance to the scroll compressor, and improves the reliability of the compressor. 
     The lubrication of the components of the compressor will be described hereinafter. In the example of a vertical scroll compressor shown in  FIG. 1 , lubricant is stored at the bottom of the compressor housing. Accordingly, a channel is formed in the drive shaft  130  and extends substantially in an axial direction of the drive shaft  130 , including a central hole  136  formed at a lower end of the drive shaft  130  and an eccentric hole  134  extending upwards to an end face of the eccentric crank pin  132  from the central hole  136 . An end portion of the central hole  136  is submerged in the lubricant in the bottom of the compressor housing or is supplied with lubricant in other manners. In one example, a lubricant supply device may be provided in the central hole  136  or near the central hole  136 , for example, an oil pump or an oil fork  138  as shown in  FIG. 1 . In the operation of the compressor, one end of the central hole  136  is supplied with lubricant by the lubricant supply device, and the lubricant entered into the central hole  136  is pumped or thrown into the eccentric hole  134  by the centrifugal force during rotation of the drive shaft  130 , and flows upwards along the eccentric hole  134  till it reaches the end face of the eccentric crank pin  132 . The lubricant discharged from the end face of the eccentric crank pin  132  flows downwards through a gap between the unloading liner  142  and the eccentric crank pin  132  and a gap between the unloading liner  142  and the hub  162  into the concave portion  146  of the main bearing housing  140 . A part of lubricant gathered in the concave portion  146  flows downwards through the main bearing  144 , and a part of lubricant is agitated by the hub  162  to move upwards to reach a lower side of the end plate  164  of the orbiting scroll component  160  and spread over thrust surfaces of the orbiting scroll component  160  and the main bearing housing  140  as the orbiting scroll component  160  orbits. In order to improve the lubrication and cooling effect of the rotor  124  of the motor, a radial hole  139  may be provided in the drive shaft  130  to directly supply the lubricant from the eccentric hole  134  to the rotor  124 . In addition, a radial hole  137  may further be provided in the drive shaft  130 , to directly supply the lubricant to a lower bearing which supports a lower end of the drive shaft  130 . In the operation of the compressor, the lubricant supplied to the various movable components in the compressor is thrown or splashes to form liquid drops or mist. These lubricant drops or mist will be mixed with the working fluid (or refrigerant) sucked from the intake connector  118 . Subsequently, the working fluid mixed with the lubricant drops is sucked into the compression chambers between the non-orbiting scroll component  150  and the orbiting scroll component  160  to realize the lubricating, sealing and cooling of the interior of these scroll components. This kind of lubrication between the orbiting scroll component and the non-orbiting scroll component is commonly referred to as mist lubrication. 
     The configuration and function of the seal assembly S is further described in detail hereinafter. As shown in  FIG. 1B , the seal assembly S may include an upper plate S 1 , a lower plate S 2 , and a first seal member S 3  and a third seal member S 5  which are arranged between the upper plate S 1  and the lower plate S 2 . The shape of the seal assembly S substantially corresponds to the shape of the concave portion BC, such that the first seal member S 3  may abut against a radial inner side wall of the concave portion  158  to achieve sealing, and the third seal member S 5  may abut against a radial outer side wall of the concave portion  158  to achieve sealing. In addition, an upper end S 11  of the upper plate S 1  may abut against the separator  116  or abut against a lining ring  117  arranged on the separator  116  to achieve sealing. More specifically, the first seal member S 3  is configured to prevent the fluid from flowing from the high-pressure side to the back pressure chamber BC, however, allow the fluid to flow from the back pressure chamber BC to the high-pressure side. For example, the first seal member S 3  may include a substantially annular body S 32 , and a seal lip S 34  extending away from the non-orbiting scroll end plate from the body S 32  and abutting against the radial inner side wall of the concave portion  158 . The body S 32  is sandwiched between the upper plate S 1  and the lower plate S 2 . Similarly, the third seal member S 5  is configured to prevent the fluid from flowing from the back pressure chamber BC to the low-pressure side. For example, the third seal member S 5  may include a substantially annular body S 52  and a seal lip S 54  extending towards the non-orbiting scroll end plate from the body S 52  and abutting against the radial outer side wall of the concave portion  158 . The body S 52  is sandwiched between the upper plate S 1  and the lower plate S 2 . 
     The seal assembly S achieves sealing in a compressor in the following manners: 1) the upper end S 11  of the upper plate S 1  abuts against the lining ring  117  in the separator  116  to achieve the separation of the high-pressure side from the low-pressure side; 2) the first seal member S 3  abuts against the radial inner side wall of the concave portion  158  to achieve the separation of the high-pressure side from the back pressure chamber BC; 3) the third seal member S 5  abuts against the radial outer side wall of the concave portion  158  to achieve the separation of the back pressure chamber BC from the low-pressure side. 
     If the above seal assembly S (also referred to as a single-layer seal assembly) is applied, in the case that the compressor is started with liquid, the scroll components compress the liquid, and the pressure in the back pressure chamber BC is much higher than the discharge pressure (the pressure in the high-pressure side), the first seal member S 3  allows the fluid in the back pressure chamber to leak to the high-pressure side, thus can just relief this part of surged pressure, which improves the reliability of the compressor. However, in the case that the compressor is in a working condition of a low pressure ratio, if the pressure in the back pressure chamber BC is higher than that on the high-pressure side, the first seal member S 3  allows the pressure in the back pressure chamber to leak to the high-pressure side, thus may cause the improper engagement between the orbiting scroll component and the non-orbiting scroll component, and thus the noise, and reduced refrigerating capacity and the like. 
       FIGS. 2A and 2B  illustrate a double-layer seal assembly. More specifically, in addition to the components shown in  FIG. 1B , the seal assembly S shown in  FIGS. 2A and 2B  further includes a second seal member S 4  and an intermediate plate S 6  arranged between the first seal member S 3  and the second seal member S 4 . The second seal member S 4  is configured to prevent the fluid from flowing from the back pressure chamber BC to the high-pressure side, however, allow the fluid to flow from the high-pressure side to the back pressure chamber BC. For example, the second seal member S 4  may include a substantially annular body S 42  and a seal lip S 44  extending from the body S 42  towards the non-orbiting scroll end plate and abutting against the radial inner side wall of the concave portion  158 . The body S 42  is sandwiched between the intermediate plate S 6  and the lower plate S 2 . The structure and function of other members of the double-layer seal assembly are similar to those of the single-layer seal assembly shown in  FIG. 1B . 
     If the double-layer seal assembly S shown in  FIGS. 2A and 2B  is applied, in the case that the compressor is in a working condition of a low pressure ratio, even if the pressure in the back pressure chamber BC is higher than that in the high-pressure side, the second seal member S 4  does not allow the pressure in the back pressure chamber to leak to the high-pressure side, result in the good engagement between the orbiting scroll component and the non-orbiting scroll component. However, in the case that the compressor is started with liquid, since the second seal member S 4  does not allow the fluid in the back pressure chamber to leak to the high-pressure side, the pressure in the back pressure chamber BC is far higher than the pressure desired, resulting in increasing of an axial force between the orbiting scroll component and the non-orbiting scroll component, which influences the reliability and service life of the compressor. It is to be noted that, the constructions of the above single-layer seal assembly and double-layer seal assembly are described more detail in China Invention Patent CN1028379C, the entire disclosure of which is incorporated herein by reference. 
     Thus, the above sealing construction has still room for improvement to achieve stable and reliable operation of the compressor in various operation conditions. 
     The inventor proposes to provide a leakage channel allowing the fluid in the back pressure chamber to leak outwards to address the above issues. Theoretically, the leakage channel may be configured to allow the fluid in the back pressure chamber to leak to the high-pressure side or the low-pressure side. However, considering the overall working efficiency of the compressor, preferably, the leakage channel is configured to allow the fluid in the back pressure chamber to leak to the high-pressure side. Various embodiment of the construction of the leakage channel will be described with reference to  FIGS. 3A to 8  below. 
     A seal assembly PS 1  according to a first embodiment of the present application is described in detail hereinafter with reference to  FIGS. 3A and 3B . The basic construction of the seal assembly PS 1  shown in  FIGS. 3A and 3B  are substantially the same as that shown in  FIGS. 2A and 2B . Specifically, the seal assembly PS 1  according to the first embodiment of the present application may include an upper plate S 1 , a lower plate S 2  and an intermediate plate S 6 . A first seal member S 3  and a third seal member S 5  are arranged between the upper plate S 1  and the intermediate plate S 6 . A second seal member S 4  is arranged between the intermediate plate S 6  and the lower plate S 2 . The first seal member S 3  and the second seal member S 4  may abut against a radial inner side wall of the concave portion  158  to achieve sealing, and the third seal member S 5  may abut against a radial outer side wall of the concave portion  158  to achieve sealing. An upper end S 11  of the upper plate S 1  may abut against the separator  116  or a lining ring  117  arranged on the separator  116  to achieve sealing. More specifically, the first seal member S 3  may be configured to prevent the fluid from flowing from the high-pressure side to the back pressure chamber BC, however, allow the fluid to flow from the back pressure chamber BC to the high-pressure side. For example, the first seal member S 3  may include a substantially annular body S 32 , and a seal lip S 34  extending away from the non-orbiting scroll end plate from the body S 32  and abutting against the radial inner side wall of the concave portion  158 . The second seal member S 4  may be configured to prevent the fluid from flowing from the back pressure chamber BC to the high-pressure side, however, allow the fluid to flow from the high-pressure side to the back pressure chamber BC. For example, the second seal member S 4  may include a substantially annular body S 42  and a seal lip S 44  extending towards the non-orbiting scroll end plate from the body S 42  and abutting against the radial inner side wall of the concave portion  158 . The third seal member S 5  may be configured to prevent the fluid from flowing from the back pressure chamber BC to the low-pressure side. For example, the third seal member S 5  may include a substantially annular body S 52 , and a seal lip S 54  extending towards the non-orbiting scroll end plate from the body S 52  and abutting against the radial outer side wall of the concave portion  158 . 
     Similarly, the seal assembly PS 1  achieves sealing in a compressor in the following manners: 1) the upper end S 11  of the upper plate S 1  abuts against the lining ring  117  on the separator  116  to achieve the separation of the high-pressure side from the low-pressure side; 2) the first seal member S 3  and the second seal member S 4  abut against the radial inner side wall of the concave portion  158  to achieve the separation of the high-pressure side from the back pressure chamber BC; 3) the third seal member S 5  abuts against the radial outer side wall of the concave portion  158  to achieve the separation of the back pressure chamber BC from the low-pressure side. 
     In the first embodiment of the present application, a leakage channel L is formed in the seal assembly PS 1 . More specifically, the leakage channel L is formed in the second seal member S 4 , in particular formed in the seal lip S 44  of the second seal member S 4 . For example, the leakage channel L may be a through hole S 46  formed in the seal lip S 44  of the second seal member S 4 . 
     The minimum cross-sectional area of the leakage channel L can be set as ½ to 3 times of the minimum cross-sectional area of the medium pressure channel  155  (in this case the cross-sectional area of the through hole S 46 ). Preferably, the minimum cross-sectional area of the leakage channel L can be set to be smaller than the minimum cross-sectional area of the medium pressure channel  155 . In particular, the minimum cross-sectional area of the leakage channel L can be set as 0.8 times to 1.2 times of the minimum cross-sectional area of the medium pressure channel  155 . It is noted that, in this embodiment and the following other embodiments, if the leakage channel L has varied cross-sections, the minimum cross-sectional area of the leakage channel L will be a parameter to control fluid leakage amount of the leakage channel L. Similarly, the minimum cross-sectional area of the medium pressure channel  155  is a parameter to control the amount of fluid supplied through the medium pressure channel  155 . 
     If the seal assembly PS 1  according to a first embodiment of the present application is used, in the case that the compressor is started with liquid, since the leakage channel L in the second seal member S 4  allows the fluid in the back pressure chamber to leak to the high-pressure side, thus may just relief this part of surged pressure, and improves reliability of the compressor. At the same time, in the case that the compressor is in a working condition of a low presser ratio, though the leakage channel L in the second seal member S 4  will cause leakage of the fluid in the back pressure chamber BC, since the leakage amount via the leakage channel L is smaller than the supply amount via the medium pressure channel  155 , the second seal member S 4  cooperating with the first seal member S 3  can still maintain sufficient back pressure in the back pressure chamber, result in the good engagement between the orbiting scroll component and the non-orbiting scroll component and the reduced noise caused by the engagement. In other working conditions, the seal assembly PS 1  may work as the single-layer seal assembly shown in  FIGS. 1A and 1B . In other words, according to the present application, the compressor may operate stably and reliably in various working conditions. 
     The first embodiment of the present application may be implemented only by drilling a small hole in the seal lip S 44  of the second seal member S 4  of the existing double-layer seal assembly. Thus, the constructions of other portions of the compressor are not required to be varied or modified, which greatly saves the overall manufacture cost of the compressor. 
     A seal assembly PS 2  according to a second embodiment of the present application is described in detail hereinafter with reference to  FIGS. 4A and 4B . The seal assembly PS 2  according to the second embodiment is different from the seal assembly PS 1  according to the first embodiment in that, the leakage channel L is a cutout S 47  formed on an edge of the seal lip S 44  of the second seal member S 4 . The seal assembly according to the second embodiment may achieve the similar effect as that of the first embodiment. 
     A seal assembly PS 3  according to a third embodiment of the present application is described in detail hereinafter with reference to  FIGS. 5A and 5B . The seal assembly PS 3  according to the third embodiment is different from the seal assembly PS 1  according to the first embodiment in that, the through hole S 46  may be formed in the body S 42  of the second seal member S 4  or in the seal lip S 44 , and a cutout S 62  is formed at a position in the intermediate plate S 6  corresponding to the through hole S 46 . The seal assembly according to the third embodiment may achieve the similar effect as that of the first embodiment. In addition, the third embodiment may further facilitate the machining of the through hole S 46 . 
     A seal assembly PS 4  according to a fourth embodiment of the present application is described in detail hereinafter with reference to  FIGS. 6A and 6B . The seal assembly PS 4  according to the fourth embodiment is different from the seal assembly PS 1  according to the first embodiment in that, the second seal member S 4  is configured to prevent the fluid from flowing from the back pressure chamber BC to the high-pressure side, and prevent the fluid from flowing from the high-pressure side to the back pressure chamber BC, for example, the second seal member S 4  may be an O-shaped ring arranged or supported in the lower plate S 2 ; and a channel S 22  is formed in the lower plate S 2  such as to allow the fluid in the back pressure chamber to enter into a space between the first seal member S 3  and the second seal member S 4 . For example, the channel S 22  may be an L-shaped hole which is opened at one end in a bottom surface of the lower plate S 2  and is opened at the other end in a side surface of the lower plate S 2 . The seal assembly according to the fourth embodiment may achieve the similar effect as that of the first embodiment. 
     A seal assembly PS 5  according to a fifth embodiment of the present application is described in detail hereinafter with reference to  FIGS. 7A and 7B . The seal assembly PS 5  according to the fifth embodiment may be implemented by a double-layer seal assembly shown in  FIGS. 2A and 2B . However, in the fifth embodiment, the leakage channel L may be formed in a radial inner side wall  1581  of the concave portion  158 . More specifically, the leakage channel L may be configured as a groove  1582  formed in the radial inner side wall  1581  of the concave portion  158  at a position corresponding to the second seal member S 4 . Preferably, the groove  1582  does not extend to the position of the first seal member S 3 . The fifth embodiment may achieve the similar effect as that of the first embodiment. In addition, in the fifth embodiment, the seal assembly is not required to be machined, or only the non-orbiting scroll component  150  is required to be slightly machined, which can also save the overall manufacture cost of the compressor. 
     A seal assembly PS 6  according to a sixth embodiment of the present application is described in detail hereinafter with reference to  FIGS. 8A and 8B . The seal assembly PS 6  according to the sixth embodiment may include: a first seal member S 3  arranged about the discharge port  152  of the non-orbiting scroll component  150  to prevent the fluid from flowing from the high-pressure side to the back pressure chamber BC, however, allow the fluid to flow from the back pressure chamber BC to the high-pressure side; and a second seal member S 4  arranged in the concave portion  158  to prevent the fluid from flowing from the back pressure chamber BC to the high-pressure side, however, allow the fluid to flow from the high-pressure side to the back pressure chamber BC. The seal assembly PS 6  may further include a third seal member S 5  arranged in the concave portion  158  to prevent the fluid from flowing from the back pressure chamber BC to the low-pressure side. More specifically, these seal members S 3 , S 4  and S 5  may have a substantially annular shape, and have a substantially L-shaped cross section, and two arms of the L-shaped cross section respectively abut against a wall surface of the non-orbiting scroll component  150  and the separator  116  to achieve the sealing. The first seal member S 3  may be supported by a spring S 11  arranged about the discharge port  152 . The second seal member S 4  and the third seal member S 5  may be supported by a spring S 12  arranged in the concave portion  158 . It is to be noted that, the construction of the seal assembly shown in the sixth embodiment is described in detail in China Invention Patent CN 202228358, the entire disclosure of which is incorporated herein by reference. 
     In the sixth embodiment, the leakage channel L is configured to be a through hole or slot S 46  formed in the second seal member S 4 . The sixth embodiment may achieve the similar effect as that of the first embodiment. 
     While various embodiments and modifications of the present application have been described in detail above, it should be understood by those skilled in the art that the present application is not limited to the specific embodiments and modifications described hereinbefore, but may include other various possible combinations and groups. 
     For example, a scroll compressor is provided according to one aspect of the present application. The scroll compressor includes an orbiting scroll component, a non-orbiting scroll component, a seal assembly, and a leakage channel. The orbiting scroll component includes an orbiting scroll end plate and a spiral orbiting scroll vane formed at one side of the orbiting scroll end plate. The non-orbiting scroll component includes a non-orbiting scroll end plate, a spiral non-orbiting scroll vane formed at one side of the non-orbiting scroll end plate, and a concave portion formed at the other side of the non-orbiting scroll end plate. The concave portion is in fluid communication with one of a series of compression chambers formed between the orbiting scroll vane and the non-orbiting scroll vane via a medium pressure channel. The seal assembly is fitted with the concave portion to jointly form a back pressure chamber, and is configured to separate the back pressure chamber from a high-pressure side and a low-pressure side in the scroll compressor. The leakage channel is configured to allow fluid in the back pressure chamber to leak. 
     According to a second aspect of the present application, the leakage channel may be configured to allow the fluid in the back pressure chamber to leak to the high-pressure side. 
     According to a third aspect of the present application, the leakage channel may be formed in the seal assembly. 
     According to a fourth aspect of the present application, the seal assembly may be arranged in the concave portion, and the seal assembly may include: a first seal member configured to prevent the fluid at the high-pressure side from flowing to the back pressure chamber, however, allow the fluid to flow from the back pressure chamber to the high-pressure side; and a second seal member configured to prevent the fluid in the back pressure chamber from flowing to the high-pressure side, however, allow the fluid to flow from the high-pressure side to the back pressure chamber. 
     According to a fifth aspect of the present application, the leakage channel may be formed in the second seal member. 
     According to a sixth aspect of the present application, the second seal member may include a substantially annular body and a seal lip extending from the body towards the non-orbiting scroll end plate and abutting against a radial inner side wall of the concave portion, and the leakage channel is formed in the seal lip of the second seal member. 
     According to a seventh aspect of the present application, the leakage channel may be a through hole formed in the seal lip of the second seal member. 
     According to an eighth aspect of the present application, the leakage channel may be a cutout formed on an edge of the seal lip of the second seal member. 
     According to a ninth aspect of the present application, the leakage channel may be a through hole formed in the body or the seal lip of the second seal member. 
     According to a tenth aspect of the present application, the seal assembly may further include an intermediate plate arranged between the first seal member and the second seal member, and a cutout is formed in the intermediate plate at a position corresponding to the through hole. 
     According to an eleventh aspect of the present application, the seal assembly may be arranged in the concave portion, and the seal assembly may include: a first seal member configured to prevent the fluid at the high-pressure side from flowing to the back pressure chamber, however, allow the fluid to flow from the back pressure chamber to the high-pressure side; and a second seal member configured to prevent the fluid in the back pressure chamber from flowing to the high-pressure side, and prevent the fluid at the high-pressure side from flowing to the back pressure chamber. 
     According to a twelfth aspect of the present application, the second seal member may be an O-shaped ring. 
     According to a thirteenth aspect of the present application, the seal assembly may include a lower plate configured to support the second seal member, and a channel may be formed in the lower plate to allow the fluid in the back pressure chamber to enter into a space between the first seal member and the second seal member. 
     According to a fourteenth aspect of the present application, the leakage channel may be formed in a radial inner side wall of the concave portion. 
     According to a fifteenth aspect of the present application, the seal assembly may be arranged in the concave portion, the seal assembly may include: a first seal member configured to prevent the fluid at the high-pressure side from flowing to the back pressure chamber, however, allow the fluid to flow from the back pressure chamber to the high-pressure side; and a second seal member configured to prevent the fluid in the back pressure chamber from flowing to the high-pressure side, however, allow the fluid to flow from the high-pressure side to the back pressure chamber, and the leakage channel is configured as a groove formed in the radial inner side wall of the concave portion at a position corresponding to the second seal member. 
     According to a sixteenth aspect of the present application, the groove does not extend to reach the first seal member. 
     According to a seventeenth aspect of the present application, the seal assembly may include: a first seal member arranged about the discharge port of the non-orbiting scroll component to prevent the fluid at the high-pressure side from flowing to the back pressure chamber, however, allow the fluid to flow from the back pressure chamber to the high-pressure side; and a second seal member arranged in the concave portion to prevent the fluid in the back pressure chamber from flowing to the high-pressure side, however, allow the fluid to flow from the high-pressure side to the back pressure chamber. 
     According to an eighteenth aspect of the present application, the leakage channel may be configured to be a through hole or slot formed in the second seal member. 
     According to an eighteenth aspect of the present application, the seal assembly may further include a third seal member arranged in the concave portion to prevent the fluid in the back pressure chamber from flowing to the low-pressure side. 
     According to a nineteenth aspect of the present application, the seal assembly may further include a third seal member configured to prevent the fluid in the back pressure chamber from flowing to the low-pressure side. 
     According to a twentieth aspect of the present application, the third seal member may include a substantially annular body and a seal lip extending towards the non-orbiting scroll end plate from the body and abutting against a radial outer side wall of the concave portion. 
     According to a twenty-second aspect of the present application, the scroll compressor may further include a separator configured to separate an inner space of the scroll compressor into a high-pressure side and a low-pressure side, wherein the seal assembly is arranged between the separator and the non-orbiting scroll component. 
     According to a twenty-third aspect of the present application, the minimum cross-sectional area of the leakage channel may be ½ to 3 times as big as the minimum cross-sectional area of the medium pressure channel. 
     According to a twenty-fourth aspect of the present application, the minimum cross-sectional area of the leakage channel may be set to be smaller than the minimum cross-sectional area of the medium pressure channel. 
     According to a twenty-fifth aspect of the present application, the minimum cross-sectional area of the leakage channel is set to be 0.8 times to 1.2 times as big as the minimum cross-sectional area of the medium pressure channel. 
     While various embodiments of the present application have been described in detail herein, it should be understood that the present application is not limited to the specific embodiments described in detail and illustrated herein, and those skilled in the art can also make other variants and modifications without departing from the principle and scope of the application, and these variants and modifications should also be deemed to fall into the protective scope of the application. Furthermore, all the elements described herein can be replaced by other technically equivalent elements.