Patent Publication Number: US-8992191-B2

Title: Scroll compressor with differential pressure hole

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims priority to Korean Application No. 10-2011-0098596, filed in Korea on Sep. 28, 2011, which is herein expressly incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field 
     A scroll compressor is disclosed herein. 
     2. Background 
     Scroll compressors are known. However, they suffer from various disadvantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
         FIG. 1  is a longitudinal sectional view of an oil supplying structure that supplies oil into a compression chamber using differential pressure in a scroll compressor according to an embodiment; 
         FIG. 2  is a sectional view taken along the line “II-II” of  FIG. 1 ; 
         FIG. 3  is a longitudinal sectional view of internal structure of a scroll compressor in accordance with an embodiment; 
         FIG. 4  is a longitudinal sectional view of a portion of a compression device illustrating a back pressure passage in the scroll compressor of  FIG. 3 ; 
         FIG. 5  is a schematic view illustrating a sealing effect between a fixed scroll and an orbiting scroll by the back pressure passage of  FIG. 4 ; 
       FIGS.  6  and  7 - 8  are a planar view and longitudinal sectional views, respectively, showing an oil collection pump of the scroll compressor of  FIG. 3  according to embodiments; 
         FIG. 9  is a longitudinal sectional view of a portion of a compression device showing a differential pressure passage in the scroll compressor of  FIG. 3 ; 
         FIG. 10  is a planar view of the compression device illustrating positions of the back pressure passage and the differential pressure passage according to embodiments; 
         FIG. 11  is a longitudinal sectional view showing the differential pressure hole of  FIG. 9  in an enlarged state; 
         FIGS. 12 and 13  are sectional views taken along the lines “XII-XII” and “XIII-XIII” of  FIG. 11 , respectively; 
         FIG. 14  is a longitudinal sectional view illustrating a process of supplying oil via the differential pressure passage of  FIG. 9 ; 
         FIG. 15  is a longitudinal sectional view showing another example of the differential pressure hole of  FIG. 9  in an enlarged state; 
         FIG. 16  is a longitudinal sectional view of an oil collection pump in accordance with another embodiment; and 
         FIG. 17  is a longitudinal sectional view of a scroll compressor having an oil collection pump disposed outside of a shell in accordance with another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Description will now be given in detail of a compressor in accordance with embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated. 
     A refrigerant compression type refrigeration cycle may be configured by connecting a compressor, a condenser, an expansion apparatus, and an evaporator via a closed loop refrigerant pipe. A refrigerant compressed in the compressor may circulate sequentially via the condenser, the expansion apparatus, and the evaporator. 
     When the compressor is installed in the refrigerant compression type refrigeration cycle, a predetermined amount of oil is required for lubrication of a drive, sealing of a compression device, and cooling. The predetermined amount of oil is filled in a shell of the compressor. However, some of the oil may be mixed with the refrigerant discharged out of the compressor, and the discharged oil may circulate via the condenser, the expansion apparatus, and the evaporator together with the refrigerant. When an excessive amount of oil circulates along the refrigeration cycle or a large amount of oil remains in the refrigeration cycle without being collected back into the compressor, a lack of oil within the compressor may result. This may result in lowering of reliability of the compressor, and accordingly, lowering of a heat exchange performance of the refrigeration cycle. 
     Scroll compressors are well known. A scroll compressor may include an oil separator installed at a discharge side of the compressor, an oil pump that collects oil separated by the oil separator, and an oil collection pipe that connects the oil separator to the oil pump. In such a scroll compressor, if an inner space of the shell is at a discharge pressure, oil separated by the oil separator may be smoothly collected. However, as the oil pump is installed at a lower end of a crankshaft of the scroll compressor, a pumping force may not be strong during low speed driving of the compressor. This may cause a reliability of the compressor to be lowered or reduced. 
     A scroll compressor using differential pressure has been introduced as a technology for maintaining a predetermined amount of pumped oil during low speed driving of the compressor. In such a scroll compressor, a differential pressure hole, which may communicate with the inner space of the shell as a high pressure part with a suction chamber as a low pressure part, may be formed at or in an orbiting scroll. Accordingly, oil may be quickly supplied into the suction chamber using a pumping force of an oil pump and an attractive force generated due to the pressure difference. This allows the oil to be smoothly pumped during low speed driving, enhancing reliability of the compressor. 
     However, in such a scroll compressor for supplying oil into a compression chamber using differential pressure, smooth supply of the oil into the compressor chamber during low speed driving is allowed, but such oil is supplied into the compressor in a high pressure state, or more than an appropriate amount oil is supplied into the compression chamber, causing a suction loss. 
     Taking this into account, a scroll compressor may employ a decompression device in which a pin member  2  is inserted into a differential pressure hole  1  to function as a type of orifice, as shown in  FIGS. 1-2 . The differential pressure hole  1  may have an inlet  1   a , which may be formed inside a boss portion  3   a  of an orbiting scroll  3 . A pin supporting portion  1   c  that supports the pin member  2  in a lengthwise direction may be formed at an inner circumferential surface of the differential pressure hole  1  in a stepped state. 
     In such a decompression device, the pin member  2  may be placed at a position where it always overlaps an outlet  1   b  of the differential pressure hole  1  due to the pin supporting portion  1   c . The pin member  2  may narrow the outlet  1   b  of the differential pressure hole  1  due to oil introduced between the pin member  2  and the differential pressure hole  1  via the inlet  1   a . Accordingly, pressure and an amount of oil supplied into the suction chamber via the outlet  1   b  of the differential pressure hole  1  may be appropriately adjusted. 
     However, in such a scroll compressor, oil pressure and oil amount may be adjusted as the pin member  2  blocks a part of the outlet  1   b  of the differential pressure hole  1 . Thus, in order for the pin member  2  to always block the part of the outlet  1   b  of the differential pressure hole  1 , the pin supporting portion  1   c , which limits the position of the pin member  2 , has to be stepped with respect to the differential pressure hole  1 , which makes processing of the orbiting scroll complicated. 
     Further, as the inlet  1   a  of the differential pressure hole  1  is formed inside the boss portion  3   a  of the orbiting scroll, oil sucked up from the crankshaft may not be sufficiently supplied to a thrust bearing surface between the orbiting scroll and a frame. This may cause frictional loss and abrasion of the thrust bearing surface. 
       FIG. 3  is a longitudinal sectional view of internal structure of a scroll compressor in accordance with an embodiment, and  FIG. 4  is a longitudinal sectional view of a portion of a compression device for illustrating a back pressure passage in the scroll compressor of  FIG. 3 . 
     As shown in  FIG. 3 , a scroll compressor according to this embodiment may include a shell  10  having a sealed inner space, a drive motor  20  installed in the inner space of the shell  10 , and a compression device  30  having a fixed scroll  31  and a orbiting scroll  32 , which are driven by the drive motor  20  to compress a refrigerant. 
     The shell  10  may have an inner space filled with refrigerant at a discharge pressure. A suction pipe  13  may penetrate through one side of the shell  10  so as to communicate with a suction groove  313  (or suction chamber) of the fixed scroll  31 , and a discharge pipe  14  may be connected to another side of the shell  10  to guide a refrigerant discharged into the inner space of the shell  10  toward a refrigeration cycle system. 
     The drive motor  20  may include a stator  21 , which may be wound with a winding coil in a concentrated winding manner. The drive motor  20  may be implemented as a constant speed motor, in which a rotor  22  rotates at a same rotation speed. Alternatively, the drive motor  20  may be implemented as an inverter motor, in which the rotation speed of the rotor  22  is variable, taking multifunctional refrigerating devices having a compressor into account. Also, the drive motor  20  may be supported by a main frame  11  and a sub frame  12 , which may be fixed to upper and lower sides of the shell  10 . 
     The compression device  30  may include the fixed scroll  31 , which may be coupled to the main frame  11 , the orbiting scroll  32 , which may be engaged with the fixed scroll  31  to define a pair of compression chambers P that continuously move, an Oldham ring  33  installed between the orbiting scroll  32  and the main frame  11  to induce an orbiting motion of the orbiting scroll  32 , and a check valve  34  installed to open and close the discharge hole  314  of the fixed scroll  31  so as to block gas discharged via the discharge hole  314  from back flowing. 
     The fixed scroll  31  may include a fixed wrap  312  formed at a lower surface of a disc portion  311  that defines the compression chambers P, the suction groove  313 , which may be formed at an edge of the disc portion  311 , and the discharge hole  314 , which may be formed at a central portion of the disc portion  311 . The suction pipe  13  may be directly connected to the suction groove  313  of the fixed scroll  31  so as to guide refrigerant from a refrigeration cycle system into the scroll compressor. 
     The orbiting scroll  32  may include an orbiting wrap  322  formed at an upper surface of a disc portion  321  that defines the compression chambers P by being engaged with the fixed wrap  312 , and a boss portion  323  formed at a lower surface of the disc portion  321  and coupled with a crankshaft  23 . The boss portion  323  may be orbitably inserted into a shaft receiving portion  113 , which may extend to a shaft receiving hole  111  of the main frame  11  and may be formed at or in a thrust bearing surface  112  to have a preset depth. 
     A back pressure chamber S 1 , which may be defined as an intermediate pressure space by the orbiting scroll  32 , the fixed scroll  31 , and the main frame  11 , may be formed at an edge of a rear surface of the orbiting scroll  32 . A sealing member  114  may be installed between the main frame  11  and the orbiting scroll  32  to prevent oil sucked up via an oil passage  231  of the crankshaft  23  from being excessively introduced into the back pressure chamber S 1 . The sealing member  114  may be located between the shaft receiving portion  113  of the main frame  11  and the back pressure chamber S 1 . 
     Referring to  FIG. 4 , a back pressure hole  315  may be formed at or in the fixed scroll  31 . The back pressure hole  315  may serve to induce a portion of a refrigerant from an intermediate compression chamber having intermediate pressure, between suction pressure and discharge pressure, toward the back pressure chamber S 1  so as to support an edge of the orbiting scroll  32  in a thrusting direction. The back pressure hole  315  may include a first open end  3151  that communicates with the compression chambers P, and a second open end  3152  that communicates with the first open end  3151  and also the back pressure chamber S 1 . The first open end  3151  of the back pressure hole  315  may be located at a position in which it may independently communicate with both compression chambers P in an alternating manner and may be thinner than a wrap thickness of the orbiting wrap  322 , preventing leakage of refrigerant in both compression chambers P. 
     With this configuration of the scroll compressor, when power is applied to the drive motor  20 , the crankshaft  23  may rotate together with the rotor  22  to transfer a rotational force to the orbiting scroll  32 . Upon receipt of the rotational force, the orbiting scroll  32  may orbit by an eccentric distance from an upper surface of the main frame  11  via the Oldham ring  33 . Accordingly, a pair of compression chambers P which continuously move may be formed between the fixed wrap  312  of the fixed scroll  31  and the orbiting wrap  322  of the orbiting scroll  32 . The compression chambers P may be reduced in volume while moving toward a center due to the continuous orbiting motion of the orbiting scroll  32 , compressing a sucked refrigerant. Referring to  FIG. 5 , a central portion of the orbiting scroll  32  may be supported by oil introduced into the shaft receiving portion  113  while a side portion of the orbiting scroll  32  may be supported by refrigerant introduced from the compression chambers P into the back pressure chamber S 1  via the back pressure hole  315 . Consequently, the refrigerant within the compression chambers P may be smoothly compressed without being leaked. 
     The refrigerant compressed in the compression chambers P may be continuously discharged into an upper space S 2  of the shell  10  via the discharge hole  314  of the fixed scroll  31 , and may then flow into a lower space S 3  of the shell  10 , thereby being discharged into a refrigeration cycle system via the discharge pipe  14 . An oil separating device  40  may be installed at a middle of the discharge pipe  14  to separate oil from the refrigerant, which may be discharged from the shell  10  into the refrigeration cycle system via the discharge pipe  14 , and an oil collecting device  50  that collects the oil separated by the oil separating device  40  into the shell  10  may be installed on the oil separating device  40 . 
     The oil separating device  40 , as shown in  FIG. 3 , may include an oil separator  41  disposed at one side of the shell  10  in series, and an oil separation member (not shown) installed in the oil separator  41  that separates oil from refrigerant discharged from the compression device  30 . The discharge pipe  14  may be connected to a middle of a side wall surface of the oil separator  41  to support the oil separator  41 , or a supporting member  42 , such as a clamp, may be disposed between the shell  10  and the oil separator  41  for support. A refrigerant pipe  15  may be connected to an upper end of the oil separator  41  to allow the separated refrigerant to flow into a condenser of the refrigeration cycle system. An oil collection pipe  51 , which will be explained later, may be connected to a lower end of the oil separator  41  to guide the oil separated by the oil separator  41  to be collected into the shell  10  or the compression device  30  of the compressor. 
     The oil separating device  40  may employ various oil separation methods, such as installing a mesh screen in the oil separator  41 , to separate oil from refrigerant, or connecting the discharge pipe in an inclined state to separate relatively heavy oil from refrigerant while the refrigerant rotates in a cyclone shape. 
     The oil collecting device  50  may include the oil collection pipe  51  connected to the oil separator  41  to guide oil separated by the oil separator  41  toward the shell  10 , and an oil collection pump  52  connected to the oil collection pipe  51  to pump the oil separated by the oil separator  41  toward the shell  10 . The oil collection pipe  51  may have one end connected to a lower end of the oil separator  41  and the other end connected to an inlet of the oil collection pump  52  via the shell  10 . The oil collection pipe  51  may be made of, for example, a metal pipe having a predetermined rigidity to stably support the oil separator  41 . Also, the oil collection pipe  51  may be curved by an angle so that the oil separator  41  is arranged in parallel to the shell  10  so as to attenuate vibration of the compressor. The oil collection pipe  51  may be coupled to a pump cover  523  of the oil collection pump  52 , which will be explained later, using a communication hole (not shown) formed on or in the sub frame  12 . 
     FIGS.  6  and  7 - 8  are a planar view and a longitudinal sectional views, respectively, showing an oil collection pump of  FIG. 3  according to embodiments. As shown in FIGS.  6  and  7 - 8 , the oil collection pump  52  may be implemented by employing various types of pumps. As shown in this exemplary embodiment, the oil collection pump  52  may be implemented as a trochoid gear pump which includes an inner gear  521  and an outer gear  522  engaged with each other to form a variable displacement. 
     The inner gear  521  may be coupled to the crankshaft  23  to be driven by a driving force of the drive motor  20 . The inner gear  521  and the outer gear  522  may be received in the pump cover  523 , which may be fixed to the sub frame  12 . The pump cover  523  may include one inlet  5231  and one outlet  5234 , which may communicate with the variable displacement of the oil collection pump  52 , respectively. The inlet  5231  may communicate with the oil collection pipe  51  while the outlet  5234  may communicate with an oil storage of the lower space S 3  of the shell  10 . 
     An oil hole  5235 , which may communicate with the oil passage  231  of the crankshaft  23 , may be formed at a central portion of the pump cover  523 . An oil supply pipe  524  may be coupled to the oil hole  5235  to guide oil stored in the inner space of the shell  10  toward the oil passage  231  of the crankshaft  23 . Alternatively, as shown in  FIG. 8 , the oil supply pipe  524  may be directly coupled to the oil passage  231  of the crankshaft  23  via the oil hole  5235 . When the oil supply pipe  524  is directly coupled to the crankshaft  23 , a pumping member  525 , such as a propeller, which may generate a pumping force, may be inserted in the oil supply pipe  524 , to improve the oil pumping force when the oil supply pipe  524  rotates in response to rotation of the crankshaft  23 . 
     The oil separator  41  of the scroll compressor having this configuration may separate oil from refrigerant, which is discharged from the inner space of the shell  10  into the refrigeration cycle system, and the separated oil may be collected back into the inner space of the shell  10  by the oil collection pump  52 . In more detail, oil introduced into the compression chambers P may be discharged together with refrigerant to be introduced into the oil separator  41  via the discharge pipe  14 . The oil may be separated from the refrigerant in the oil separator  41 . The separated refrigerant may flow toward a condenser of the refrigeration cycle system via the refrigerant pipe  15 , while the separated oil may be gathered at a bottom of the oil separator  41 . As the crankshaft  23  of the drive motor  20  rotates, the inner gear  521  of the oil collection pump  52  may rotate to generate a pumping force and forming a variable displacement with the outer gear  522 . The pumping force may be used to pump the oil separated by the oil separator  41 . The oil pumped by the oil collection pump  52  may be collected into the lower space S 3  of the shell  10 , which may define the oil storage, via the oil collection pipe  51  and the oil collection pump  52 . 
     The oil collected in the inner space of the shell  10  may be sucked up via the oil supply pipe  524  and the oil passage  231  of the crankshaft  23 , thereby being supplied to a sliding (bearing) portion of the compression device  30 . In accordance with embodiments disclosed herein, the inner space of the shell  10 , which may define a relatively high pressure part, may communicate with the compression chambers P, which may define a relatively low pressure part, such that the oil collected in the inner space of the shell  10  may be sucked from the inner space of the shell  10  back into the compression chambers P by a pressure difference (differential pressure). 
       FIG. 9  is a longitudinal sectional view of a portion of a compression device showing a differential pressure passage in the scroll compressor of  FIG. 3 .  FIG. 10  is a planar view of the compression device illustrating positions of the back pressure passage and the differential pressure passage according to embodiments. As shown in  FIGS. 9 and 10 , a communication hole  316  may be formed at or in the fixed scroll  31 . The communication hole  316  may communicate from a thrust bearing surface (hereinafter, referred to as a first thrust surface)  319  contacting the orbiting scroll  32  to the compression chambers P. A differential pressure hole  324  may be formed at or in the orbiting scroll  32 . The differential pressure hole  324  may guide oil sucked up via the oil passage  231  toward a thrust bearing surface (hereinafter, referred to as a second thrust surface)  329  contacting the fixed scroll  31 . 
     The communication hole  316  may include a first open end  3161  that contacts the first thrust surface  319  and a second open end  3162  that communicates with the first open end  3161  and contacts the compression chambers P. The second open end  3162 , as shown in  FIG. 10 , may be formed at a position closer to the suction groove (or suction chamber)  313  than the second open end  3152  of the back pressure hole  315 , without overlapping the second open end  3152  of the back pressure hole  315 . 
     When the second open end  3162  of the communication hole  316  is formed too close to a discharge side, it may increase pressure within the communication hole  316 . This may interrupt smooth oil introduction or cause compression loss. Hence, as shown in  FIG. 10 , an opening time point of the second open end  3162  as an outlet of the communication hole  316  may be within approximately −60°, based on a crank angle, from a suction-completed time point, namely, a time point when an outer surface of an outer end of the orbiting wrap  322  contacts an inner surface of an outer end of the fixed warp  312 . Also, the second open end  3162  of the communication hole  316  may be formed at a position where it may independently communicate with both compression chambers P in an alternating manner so as to supply oil into the both compression chambers P. In addition, the second open end  3162  of the communication hole  316  may be formed such that an inner diameter thereof is not be greater than a wrap thickness of the orbiting wrap  322  to prevent leakage of refrigerant between the compression chambers P. 
       FIG. 11  is a longitudinal sectional view showing the differential pressure hole of  FIG. 9  in an enlarged state, and  FIGS. 12 and 13  are sectional views taken along the lines “XII-XII” and “XIII-XIII” of  FIG. 11 , respectively. As shown in  FIGS. 11 to 13 , the differential pressure hole  324  may penetrate through a center of the disc portion  321  of the orbiting scroll  32  toward an outer circumferential surface in a radial direction. The differential pressure hole  324  may include a decompression portion  3241 , in which the pin member  325  is slidably inserted in a radial direction to decompress oil pressure. 
     An inner diameter D 1  of the decompression portion  3241  may be slightly greater than an outer diameter D 2  of the pin member  325 , such that pressure of oil introduced into the decompression portion  3241  may be decompressed while the oil flows between the decompression portion  3241  and the pin member  325 . 
     An inlet  3242  of the differential pressure hole  324  may be formed at one end portion of the decompression portion  3241 , such that oil may be introduced into the decompression portion  3241  therethrough. An outlet  3243  of the differential pressure hole  324  may be formed at the other end portion of the decompression portion  3241 , such that the oil passing through the decompression portion  3241  may be discharged to the thrust bearing surface  329  between the orbiting scroll  32  and the fixed scroll  31  so as to flow toward the communication hole  316 . 
     A length L 1  between the inlet  3242  and the outlet  3243  of the differential pressure hole  324  may be longer than a length L 2  of the pin member  235 , such that the pin member  325  may be slidable within the decompression portion  3241 . 
     The inlet  3242  of the differential pressure hole  324  may be formed such that the oil sucked via the oil passage  231  may be introduced into the inlet  3242  of the differential pressure hole  324  after lubrication between the boss portion  323  of the orbiting scroll  32  and the shaft receiving portion  113  of the main frame  11 , deriving a smooth lubrication of the orbiting scroll  32 . Referring to  FIG. 10 , the inlet  3242  of the differential pressure hole  324  may be positioned outside of an outer circumferential surface of the boss portion  323  based on a center of the boss portion  323 , namely, between the shaft receiving portion  113  and the sealing member  114 . 
     A communication groove  3163 , which may have a sectional area greater than that of the differential pressure hole  324  or the communication hole  316 , may be formed at at least one of the outlet  3243  of the differential pressure hole  324  or the first open end  3161  of the communication hole  316  (the communication groove  3163  is formed at the first open end  3161  of the communication hole  316  in the drawings). This may result in an increase in an amount of oil sucked. 
     An expansion portion  3244 , which may have an inner diameter D 3  greater than the inner diameter D 1  of the decompression portion  3241  to expand oil passing through the decompression portion  3241 , may be formed near the outlet  3243  of the differential pressure hole  324 . The decompression portion  3241  may communicate with the expansion portion  3244 . A length L 3  of the expansion portion  3244  may be formed shorter than the length L 2  of the pin member  325 , such that the pin member  325  may extend over the expansion portion  3244  and the decompression portion  3241 . 
     In the scroll compressor having such a configuration, the oil stored in the inner space of the shell  10  may be sucked into the compression chambers P as a low pressure part by the pressure difference. 
       FIG. 14  is a longitudinal sectional view illustrating a process of supplying oil via the differential pressure passage of  FIG. 9 . As shown in  FIG. 14 , oil introduced into the boss portion  323  of the orbiting scroll  32  via the oil passage  231  of the crankshaft  23  may flow toward an outer circumferential surface of the boss portion  323  and then move onto the thrust bearing surface between the orbiting scroll  32  and the main frame  11 . The oil moving to the thrust bearing surface between the main frame  11  and the orbiting scroll  32  may be partially introduced into the decompression portion  3241  via the inlet  3242  of the differential pressure hole  324 . 
     The oil introduced into the decompression portion  3241  may flow to the outlet  3243  of the differential pressure hole  324  via a gap (t) (see  FIG. 12 ), which may be formed between an inner circumferential surface of the decompression portion  3241  and an outer circumferential surface of the pin member  325 , or to the expansion portion  3244  when the expansion portion is formed. Such oil then may flow to the thrust bearing surfaces  319  and  329  between the fixed scroll  31  and the orbiting scroll  32  via the outlet  3243  of the differential pressure hole  324 . Afterwards, the oil may be introduced into the first open end  3161  of the communication hole  316  to be guided into the suction chamber  313  via the second open end  3162  of the communication hole  316 . 
     The expansion portion may alternatively be formed at or on the pin member. For example, as shown in  FIG. 15 , by maintaining the same inner diameter D 1  of the decompression portion  3241 , the pin member  325  may be stepped to have a large diameter part  3251  and a small diameter part  3252 . The small diameter part  3252  may be defined as the expansion portion. When the expansion portion is formed at or on the pin member, the operating effect may be the same or similar to the aforementioned embodiments, so respective description has been omitted. 
     Hereinafter, description will be given of an oil supply apparatus for a scroll compressor according to another embodiment. That is, in the aforementioned embodiment, the oil collection pump has one inlet and one outlet, such that the inlet communicates with the oil collection pipe and the outlet communicates with the inner space of the shell, respectively. However, in this embodiment, the oil collection pump  52 , as shown in  FIG. 16 , may include two inlets  5231  and  5232  and one outlet  5234 . 
     With this structure, the two inlets  5231  and  5232  of the oil collection pump  52  may communicate with the oil collection pipe  51  and the inner space of the shell  10 , respectively, while the one outlet  5234  may communicate directly with the oil passage  231  of the crankshaft  23 . An oil storage  5236  that stores a predetermined amount of oil may further be formed in the outlet  5234 . The oil storage  5236  may communicate with the oil passage  231  of the crankshaft  23 . 
     Even in the scroll compressor having this configuration, pressure of the oil passage  231 , more particularly, pressure of the oil storage  5236  of the pump cover  523  may become higher than the pressure of the compression chambers P. Accordingly, oil collected via the oil collection pipe  51  and oil pumped up from the inner space of the shell  10  may be sucked into the compression chambers P not only by the differential pressure, but also by the pumping force of the oil collection pump  52 . This may allow the oil to be smoothly supplied even during low speed driving and at the beginning of the driving. 
     Hereinafter, description will be given of an oil supply apparatus for a scroll compressor according to another embodiment. 
     That is, the aforementioned embodiments have illustrated that the oil collection pump is installed inside the shell or coupled to the drive motor to use the driving force of the drive motor. However, in this embodiment, as shown in  FIG. 17 , the oil collection pump  52  of the oil collecting device  50  may be installed outside of the shell  10  and driven using a drive source separate from the drive motor  20 . To this end, the oil collection pump  52  may be installed at a middle of the oil collection pipe  51  outside of the shell  10 , and an inverter motor, whose rotation speed increases or decreases cooperative with the rotation speed of the drive motor  20 , may be installed. The outlet of the oil collection pipe  51  may be connected directly to the oil passage  231  of the crankshaft  23 , but in some cases, connected to the inner space of the shell  10 . 
     In the scroll compressor having such a configuration, the basic configuration of pumping oil into the compression chambers and its operating effect may be the same or similar to the aforementioned embodiments. However, in the scroll compressor according to this embodiment, the pump, which pumps oil, may be installed outside of the shell  10 , rather than inside the shell  10 , and the oil collection pipe  51  may communicate with the inner space of the shell  10 . Accordingly, foreign materials contained in the oil may be filtered in the inner space of the shell  10 . This may prevent contamination of the oil supplied to the thrust surfaces or the compression chambers P in advance. Also, installation of the oil collection pump  52  outside of the shell  10  may facilitate maintenance and management of the oil collection pump  52 . 
     The foregoing embodiments have exemplarily illustrated a scroll compressor. However, the present disclosure may be applied equally to a so-called hermetic compressor, such as a rotary compressor, in which a drive motor and a compression device are installed inside the same shell, without being limited to the scroll compressor. 
     Embodiments disclosed herein provide a scroll compressor capable of facilitating processing of an orbiting scroll by simplifying a structure of a differential pressure hole for insertion of a pin member therein. Further, embodiments disclosed herein provide a scroll compressor capable of reducing frictional loss and abrasion by allowing oil to be sufficiently supplied between an orbiting scroll and a frame. 
     Embodiments disclosed herein provide a scroll compressor that may include a shell having an inner space filled with refrigerant discharged to the inner space, the inner space containing a predetermined amount of oil, a drive motor installed in the shell, a crankshaft coupled to a rotor of the drive motor and having an oil passage formed therethrough, a fixed scroll fixed to the shell and having a fixed wrap, and an orbiting scroll having an orbiting wrap engaged with the fixed wrap, the orbiting scroll forming compression chambers together with the fixed scroll while orbiting with respect to the fixed scroll. The orbiting scroll may include a differential pressure hole that communicates a high pressure part formed in the inner space of the shell with an intermediate pressure part formed between the fixed scroll and the orbiting scroll. The differential pressure hole may include a decompression portion having a pin member inserted therein that decompresses oil. An inner diameter D 1  of the decompression portion may be greater than an outer diameter D 2  of the pin member. The decompression portion may include an inlet through which oil may be introduced from the high pressure part into the differential pressure hole, and an outlet through which oil from the differential pressure hole may be discharged into the intermediate pressure part. A length L 1  between the inlet and the outlet may be longer than a length L 2  of the pin member. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. 
     As present features may be embodied in several forms without departing from characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather, should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. 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 embodiment, 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, various 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.