Patent Publication Number: US-2023151813-A1

Title: Compressor and method for manufacturing compressor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of International Patent Application No. PCT/JP2021/026024 filed on Jul. 9, 2021, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No. 2020-133286 filed on Aug. 5, 2020. The entire disclosures of all of the above applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a compressor, which is configured to compress suctioned fluid and discharge the compressed fluid, and a method for manufacturing the compressor. 
     BACKGROUND 
     A previously proposed compressor includes: a compression mechanism; an electric motor unit; a drive shaft which transmits a drive force outputted from the electric motor unit to the compression mechanism; and a housing, which receives the compression mechanism. A portion of the drive shaft, which is located on one side in an axial direction, is rotatably supported by a main bearing, which is formed at a main bearing member of the compression mechanism. Another portion of the drive shaft, which is located on another side in the axial direction, is rotatably supported by a sub-bearing, which is formed at an inside of a body portion of a sub-bearing member, while the body portion is shaped in a tubular form. The housing includes a housing main body which is shaped in a bottomed tubular form and has an opening on the one side in the axial direction. The sub-bearing member is formed integrally with a bottom surface of a bottom portion of the housing main body. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     According to one aspect of the present disclosure, there is provided a compressor including: a compression mechanism that is configured to compress fluid; an electric motor unit that is configured to output a drive force which drives the compression mechanism; a drive shaft that is configured to transmit the drive force, which is outputted from the electric motor unit, to the compression mechanism; and a housing that receives the compression mechanism, the electric motor unit and the drive shaft. The housing includes a first housing, which is shaped in a bottomed tubular form and has an opening on one side in an axial direction of the drive shaft, and a second housing, which covers the opening of the first housing. A portion of the drive shaft, which is located on the one side in the axial direction, is rotatably supported by a main bearing. Another portion of the drive shaft, which is located on another side in the axial direction, is rotatably supported by a sub-bearing, which is formed integrally in one-piece with or is fixed to an inside of a body portion of a sub-bearing member, while the body portion is shaped in a tubular form. The sub-bearing member is formed separately from the first housing and is fixed to a bottom surface of a bottom portion of the first housing. 
     According to another aspect of the present disclosure, there is provided a method for manufacturing the compressor, including: coaxially aligning a central axis of the sub-bearing and a central axis of an inner circumferential surface of an insertion section of the tubular portion, wherein the insertion section is a section of the tubular portion to which the compression mechanism is inserted; and fixing the sub-bearing member to an inner surface of the bottom portion of the first housing in a state where the central axis of the sub-bearing and the central axis of the inner circumferential surface of the insertion section are coaxially aligned. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG.  1    is a schematic cross-sectional view of a compressor according to a first embodiment. 
         FIG.  2    is a schematic view showing a bottom surface of a first housing and a sub-bearing member. 
         FIG.  3    is an explanatory diagram for explaining a flow of an assembling operation of constituent components of the compressor. 
         FIG.  4    is a schematic cross-sectional view of a compressor of a first comparative example of the first embodiment. 
         FIG.  5    is a schematic cross-sectional view of a compressor of a second comparative example of the first embodiment. 
         FIG.  6    is a schematic view showing a bottom surface of a first housing and a sub-bearing member of a compressor of a modification of the first embodiment. 
         FIG.  7    is a schematic cross-sectional view of a compressor according to a second embodiment. 
         FIG.  8    is a schematic cross-sectional view of a compressor according to a third embodiment. 
         FIG.  9    is a schematic cross-sectional view showing a state where an aligning jig is inserted into an inside of a first housing of the compressor. 
         FIG.  10    is a view taken in a direction of an arrow X in  FIG.  9   . 
     
    
    
     DETAILED DESCRIPTION 
     A previously proposed compressor includes: a compression mechanism; an electric motor unit; a drive shaft which transmits a drive force outputted from the electric motor unit to the compression mechanism; and a housing, which receives the compression mechanism. A portion of the drive shaft, which is located on one side in an axial direction, is rotatably supported by a main bearing, which is formed at a main bearing member of the compression mechanism. Another portion of the drive shaft, which is located on another side in the axial direction, is rotatably supported by a sub-bearing, which is formed at an inside of a body portion of a sub-bearing member, while the body portion is shaped in a tubular form. The housing includes a housing main body which is shaped in a bottomed tubular form and has an opening on the one side in the axial direction. The sub-bearing member is formed integrally with a bottom surface of a bottom portion of the housing main body. An alignment gap for enabling coaxial alignment of a central axis of the main bearing and a central axis of the sub-bearing is formed between the compression mechanism and an inner circumferential surface of a tubular portion of the housing main body. 
     During an assembling operation of the above compressor, the central axis of the main bearing is detected while displacing the compression mechanism relative to the inner circumferential surface of the tubular portion of the housing main body, and the central axis of the main bearing is coaxially aligned with the central axis of the sub-bearing. Then, the compression mechanism is fixed to the housing main body while maintaining the aligned state of the central axis of the main bearing and the central axis of the sub-bearing. 
     However, the above operation requires repetitions of the accurate detection of the amount of displacement of the central axis of the main bearing while displacing the compression mechanism. Therefore, the above operation requires high equipment cost and long cycle time and is therefore not suitable for mass-produced products, such as on-vehicle compressors. 
     In view of the above point, the inventors of the present application have proposed to reduce a size of the gap between the compression mechanism and the housing main body and increase the precision of the coaxiality between a central axis of an insertion section of the housing main body, to which the compression mechanism is inserted, and the central axis of the sub-bearing to coaxially align these axes. According to the study of the inventors of the present application, in order to implement the above structure, it is necessary to precisely process each of the insertion section of the housing main body and the inner circumferential surface of the sub-bearing. 
     However, in the case where the sub-bearing member, which includes the sub-bearing, is formed integrally with the bottom portion of the housing main body, it is difficult to accurately process the inner circumferential surface of the sub-bearing, and dedicated equipment for processing the inner circumferential surface of the sub-bearing needs to be introduced. For example, in a case where the sub-bearing is a sliding bearing, grinding of the inner circumferential surface of the bearing is carried out using a grindstone that has a length which allows the grindstone to reach from the opening of the housing main body to the bottom portion. In such a case, since the degree of difficulty of polishing is significantly increased by the tendency of whirling of the grindstone during polishing, the introduction of the dedicated equipment is inevitable. 
     According to one aspect of the present disclosure, there is provided a compressor including: 
     a compression mechanism that is configured to compress fluid;
 
an electric motor unit that is configured to output a drive force which drives the compression mechanism;
 
a drive shaft that is configured to transmit the drive force, which is outputted from the electric motor unit, to the compression mechanism; and
 
a housing that receives the compression mechanism, the electric motor unit and the drive shaft, wherein:
 
the housing includes a first housing, which is shaped in a bottomed tubular form and has an opening on one side in an axial direction of the drive shaft, and a second housing, which covers the opening of the first housing;
 
a portion of the drive shaft, which is located on the one side in the axial direction, is rotatably supported by a main bearing, which is formed integrally in one-piece with or is fixed to a main bearing member of the compression mechanism;
 
another portion of the drive shaft, which is located on another side in the axial direction, is rotatably supported by a sub-bearing, which is formed integrally in one-piece with or is fixed to an inside of a body portion of a sub-bearing member, wherein the body portion is shaped in a tubular form;
 
the compression mechanism, which includes the main bearing member, is placed at an inside of a tubular portion of the first housing; and
 
the sub-bearing member is formed separately from the first housing and is fixed to a bottom surface of a bottom portion of the first housing.
 
     When the sub-bearing member, which includes the sub-bearing, is formed separately from the first housing, the inner circumferential surface of the sub-bearing can be processed in a state where the sub-bearing member is removed from the housing. Therefore, the inner circumferential surface of the sub-bearing can be processed with high precision without introducing dedicated equipment. 
     Therefore, in the compressor, which includes the first housing shaped in the bottomed tubular form, the precision of the sub-bearing, which supports the drive shaft at the bottom portion of the first housing, can be ensured without introducing the dedicated equipment. As a result, it is possible to achieve both the productivity and the high quality while limiting capital investment. 
     According to another aspect of the present disclosure, there is provided a method for manufacturing a compressor that includes: 
     a compression mechanism that is configured to compress fluid;
 
an electric motor unit that is configured to output a drive force which drives the compression mechanism;
 
a drive shaft that is configured to transmit the drive force, which is outputted from the electric motor unit, to the compression mechanism; and
 
a housing that receives the compression mechanism, the electric motor unit and the drive shaft, wherein:
 
the housing includes a first housing, which is shaped in a bottomed tubular form and has an opening on one side in an axial direction of the drive shaft, and a second housing, which covers the opening of the first housing;
 
a portion of the drive shaft, which is located on the one side in the axial direction, is rotatably supported by a main bearing, which is formed integrally in one-piece with or is fixed to a main bearing member of the compression mechanism;
 
another portion of the drive shaft, which is located on another side in the axial direction, is rotatably supported by a sub-bearing, which is formed integrally in one-piece with or is fixed to an inside of a body portion of a sub-bearing member, wherein the body portion is shaped in a tubular form;
 
the compression mechanism, which includes the main bearing member, is placed at an inside of a tubular portion of the first housing; and
 
the sub-bearing member is formed separately from the first housing and is fixed to a bottom surface of a bottom portion of the first housing, the method including:
 
coaxially aligning a central axis of the sub-bearing and a central axis of an inner circumferential surface of an insertion section of the tubular portion, wherein the insertion section is a section of the tubular portion to which the compression mechanism is inserted; and
 
fixing the sub-bearing member to an inner surface of the bottom portion of the first housing in a state where the central axis of the sub-bearing and the central axis of the inner circumferential surface of the insertion section are coaxially aligned.
 
     According to this method, since the inner circumferential surface of the sub-bearing of the sub-bearing member can be processed before the time of assembling the sub-bearing member to the first housing, the inner circumferential surface of the sub-bearing can be processed with high precision without introducing the dedicated equipment. 
     Therefore, in the compressor, which includes the first housing shaped in the bottomed tubular form, the precision of the sub-bearing, which supports the drive shaft at the bottom portion of the first housing, can be ensured without introducing the dedicated equipment. 
     Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same reference signs may be assigned to portions that are the same as or equivalent to those described in the preceding embodiment(s), and the description thereof may be omitted. Further, when only a portion of any one of the components is described in the embodiment, the description of the component described in the preceding embodiment can be applied to the rest of the component. The following embodiments may be partially combined with each other as long as the combination does not cause any trouble, even if not explicitly stated. 
     First Embodiment 
     The present embodiment will be described with reference to  FIGS.  1  to  5   . In the present embodiment, there will be described an example in which a compressor  10  of the present disclosure is applied as an on-vehicle compressor of a refrigeration cycle device for a vehicle air conditioning device. 
     The refrigeration cycle device forms a vapor compression refrigeration cycle. The refrigeration cycle device includes: the compressor  10  that compresses and discharges refrigerant which is fluid; a radiator that radiates heat from the refrigerant discharged from the compressor  10 ; a decompression device that decompresses the refrigerant discharged from the radiator; and an evaporator that evaporates the refrigerant decompressed by the decompression device. A main component of the refrigerant used in the refrigeration cycle device is carbon dioxide. The carbon dioxide shifts to a supercritical state at a lower temperature than fluorocarbon refrigerant. The refrigerant is mixed with lubricant oil, which lubricates respective sliding portions at the inside of the compressor  10 . A portion of the lubricant oil is circulated in the cycle along with the refrigerant. Here, it should be noted that the refrigerant may be fluorocarbon refrigerant. 
     The compressor  10  will be described with reference to  FIG.  1   .  FIG.  1    is an axial cross-sectional view showing a cross-section taken along a central axis CL of a drive shaft  14  of the compressor  10 . A double-sided arrow, which indicate up and down in  FIG.  1   , indicates an up-to-down direction DRv in a state where the compressor  10  is installed on the vehicle. An arrow DRa in  FIG.  1    indicates an axial direction DRa of the drive shaft  14 . 
     As shown in  FIG.  1   , the compressor  10  includes a housing  12 , the drive shaft  14 , an electric motor unit  20 , an inverter  25  and a compression mechanism  30 . The drive shaft  14 , the electric motor unit  20  and the compression mechanism  30  are received at the inside of the housing  12 . The compressor  10  is an electric compressor. The electric motor unit  20  serves as a drive source to rotate the drive shaft  14 . The compression mechanism  30  is driven in response to rotation of the drive shaft  14 . The compressor  10  has a horizontal structure in which the central axis CL of the drive shaft  14  extends in an approximately horizontal direction, and the compression mechanism  30  and the electric motor unit  20  are arranged side by side in the approximately horizontal direction. The approximately horizontal direction is a direction that intersects the gravitational direction. 
     The housing  12  forms an outer shell of the compressor  10 . The housing  12  includes a first housing  121  and a second housing  122 . The first housing  121  and the second housing  122  are made of aluminum or an aluminum alloy. 
     The first housing  121  is shaped in a bottomed tubular form and has an opening on one side in the axial direction DRa of the drive shaft  14 . In other words, the first housing  121  is shaped in a cup form that has a U-shaped cross-section. Specifically, the first housing  121  has: a tubular portion  121   b,  which is shaped in a cylindrical tubular form; and a bottom portion  121   c.  The tubular portion  121   b  has an opening  121   a  on the one side in the axial direction DRa. The bottom portion  121   c  is joined to an end part of the tubular portion  121   b  which is located on the other side in the axial direction DRa. In the first housing  121 , the tubular portion  121   b  and the bottom portion  121   c  are integrally formed in one-piece as a seamless integral article. A part of an outer surface of the bottom portion  121   c  is planar to enable close contact of the inverter  25  to the part of the outer surface of the bottom portion  121   c.    
     The first housing  121  is shaped in a stepped form where a stepped portion  80  is formed at the tubular portion  121   b.  Specifically, the first housing  121  has a first inner circumferential surface  82 , a second inner circumferential surface  83  and a step surface  81 . The first inner circumferential surface  82 , the step surface  81  and the second inner circumferential surface  83  are arranged in order of decreasing distance from the bottom portion  121   c.  In other words, the first inner circumferential surface  82 , the step surface  81  and the second inner circumferential surface  83  are arranged in order of increasing distance from the opening  121   a . The first inner circumferential surface  82  and the second inner circumferential surface  83  are respectively formed in a cylindrical shape such that the first inner circumferential surface  82  and the second inner circumferential surface  83  are concentric on the central axis CL of the drive shaft  14 . The first inner circumferential surface  82  is a section of the first housing  121 , at which the electric motor unit  20  is placed. The first inner circumferential surface  82  is cylindrical. The second inner circumferential surface  83  is located on the one side of the first inner circumferential surface  82  in the axial direction DRa. The second inner circumferential surface  83  is cylindrical. The second inner circumferential surface  83  is an inner circumferential surface of an insertion section of the first housing  121 , to which the compression mechanism  30  is inserted. An outer diameter of the compression mechanism  30  is larger than an outer diameter of the electric motor unit  20 . Therefore, a diameter of the second inner circumferential surface  83  is larger than a diameter of the first inner circumferential surface  82 . The step surface  81  connects between the first inner circumferential surface  82  and the second inner circumferential surface  83 . The step surface  81  extends in a direction perpendicular to the axial direction DRa. The step surface  81  directly contacts a bearing fixing portion  362  of a main bearing member  36  described later. Here, it should be noted that the step surface  81  may contact the bearing fixing portion  362  through an intervening component. The insertion section of the tubular portion  121   b,  to which the compression mechanism  30  is inserted, is a section of the tubular portion  121   b  that is located on the one side (i.e., the opening  121   a  side) of the step surface  81  in the axial direction DRa. 
     In the first housing  121 , the compression mechanism  30 , which includes the main bearing member  36 , is placed at the inner circumferential surface of the tubular portion  121   b , and the sub-bearing member  16 , which includes a body portion  161  shaped in a tubular form, is fixed to the bottom portion  121   c.  In the first housing  121  of the present embodiment, the tubular portion  121   b  serves as a tubular portion of the first housing  121 , and the bottom portion  121   c  serves as a bottom portion of the first housing  121 . 
     The second housing  122  is located on the one side of the first housing  121  in the axial direction DRa and covers the opening of the first housing  121 . The second housing  122  is securely fixed to the first housing  121  by lid bolts (not shown). A seal member (not shown) is interposed between an end part of the first housing  121 , which is located on the one side in the axial direction DRa, and the second housing  122 . Thus, the housing  12  is sealed. 
     The electric motor unit  20  is a three-phase AC motor that is driven by an electric power supplied from the inverter  25 . The electric motor unit  20  is formed as an inner rotor motor, in which a rotor  22  is placed on an inner side of a stator  21 . 
     The stator  21  includes a stator core  211 , which is made of a magnetic material, and coils  212 , which are wound around the stator core  211 . When the electric power is supplied from the inverter  25 , the stator  21  generates a rotating magnetic field for rotating the rotor  22 . The stator  21  is fixed to the first inner circumferential surface  82  of the tubular portion  121   b  by thermal shrink fit. 
     The rotor  22  is shaped in a cylindrical tubular form, and the drive shaft  14  is fixed to an inner periphery of the rotor  22  by, for example, press-fitting. Permanent magnets (not shown) are arranged at an inside of the rotor  22 . Balance weights  221 ,  222  are installed to two opposite side surfaces, respectively, of the rotor  22  to offset the imbalance of eccentric rotation of, for example, an orbiting scroll  34 . 
     The inverter  25  is a device that supplies the electric power to the stator  21 . The inverter  25  is installed to an outside of the housing  12 . Specifically, the inverter  25  is installed to the outer surface of the bottom portion  121   c  of the first housing  121 . 
     In the electric motor unit  20  configured in the above-described manner, when the rotating magnetic field is generated around the stator  21  in response to the supply of the electric power from the inverter  25  to the stator  21 , the rotor  22  and the drive shaft  14  are integrally rotated. 
     Here, electrical wirings (not shown) of the inverter  25  and electric wirings (not shown) of the electric motor unit  20  are electrically connected with each other through airtight terminals (not shown) installed at the bottom portion  121   c  of the first housing  121 . Therefore, the housing  12  has a sealed structure. 
     The first housing  121  of the housing  12  has a suction port  125 , through which low pressure refrigerant passed through the evaporator is suctioned. Specifically, at the first housing  121 , the suction port  125  is located on the other side of the electric motor unit  20  in the axial direction DRa. A suction pipe (not shown), which is connected to the evaporator, is connected to the suction port  125 . 
     The low-pressure refrigerant, which has passed through the evaporator, is suctioned from the suction port  125  into the inside of the housing  12  where the electric motor unit  20  is placed. The low-pressure refrigerant, which is suctioned into the inside of the housing  12 , is suctioned into the inside of the compression mechanism  30  through a suction port (not shown) of the compression mechanism  30 . For this reason, the inside of the housing  12 , in which the electric motor unit  20  is placed, has a low temperature atmosphere. In this way, the electric motor unit  20  and the inverter  25  can be cooled. Particularly, the inverter  25  is installed to the planar section of the bottom portion  121   c,  so that even when the inverter  25  generates heat during its operation, the generated heat can be efficiently conducted to the bottom portion  121   c  to cool the inverter  25 . Therefore, the efficiency and the reliability of the electric motor unit  20  and the inverter  25  can be improved. 
     The second housing  122  of the housing  12  has a discharge port  126 , through which high pressure refrigerant compressed by the compression mechanism  30  is discharged from the second housing  122 . At the housing  12 , the discharge port  126  is located on the one side of the compression mechanism  30  in the axial direction DRa. 
     Furthermore, a high-pressure muffler chamber  51 , an oil separation chamber  52  and a high-pressure oil storage chamber  53  are formed at the inside of the second housing  122 . The high-pressure muffler chamber  51  is communicated with a discharge hole  323 . The high-pressure muffler chamber  51  is a space for reducing a discharge pressure pulsation of the refrigerant, which is discharged from the discharge hole  323 . The oil separation chamber  52  is communicated with the high-pressure muffler chamber  51 . The oil separation chamber  52  is a space for separating the lubricant oil from the high-pressure refrigerant supplied from the high-pressure muffler chamber  51 . An oil separator  54 , which separates the lubricant oil from the high-pressure refrigerant supplied from the oil separation chamber  52 , is received in the oil separation chamber  52 . The oil separator  54  is shaped in a pipe form. The oil separator  54  is fixed to the discharge port  126  by, for example, press-fitting. The high-pressure oil storage chamber  53  is a space for accumulating the lubricant oil separated by the oil separator  54 . 
     The drive shaft  14  has a one-side portion  141  which is located on the one side of the rotor  22  in the axial direction DRa. The compression mechanism  30  is located on the one side of the electric motor unit  20  in the axial direction DRa of the drive shaft  14 . The one-side portion  141  is engaged with the compression mechanism  30 . The drive shaft  14  transmits the drive force, which is generated by the electric motor unit  20 , to the compression mechanism  30 . The one-side portion  141  is rotatably supported by a main bearing  361   a  (described later) of the main bearing member  36  of the compression mechanism  30 . 
     An end portion of the one-side portion  141 , which is located on the one side in the axial direction DRa, has an eccentric shaft portion  142  that is eccentric from a rotational center of the drive shaft  14 . The eccentric shaft portion  142  forms a crank mechanism for orbiting the orbiting scroll  34  described later. The eccentric shaft portion  142  is rotatably engaged with an eccentric bearing  342   a  (described later) of the orbiting scroll  34 . The eccentric shaft portion  142  is formed integrally in one-piece with a main body of the drive shaft  14 . Furthermore, the one-side portion  141  has a flange portion  143  which extends in the up-to-down direction DRv. A balance weight  143   a,  which limits eccentric rotation of the drive shaft  14 , is provided at the flange portion  143 . 
     The drive shaft  14  has an other-side portion  144  which is located on the other side of the rotor  22  in the axial direction DRa. The other-side portion  144  is rotatably supported by the sub-bearing  16   a  of the sub-bearing member  16 . Details of the sub-bearing member  16  will be described later. 
     An oil supply passage  145 , which supplies the lubricant oil to the bearings  16   a ,  342   a,    361   a,  is formed at an inside of the drive shaft  14 . The oil supply passage  145  is communicated with the high-pressure oil storage chamber  53  through an oil flow passage (not shown) which is formed at the stationary scroll  32  and the orbiting scroll  34 . With this configuration, the lubricant oil, which is stored in the high-pressure oil storage chamber  53 , is supplied to the bearings  16   a,    342   a,    361   a  from the oil supply passage  145 . Each of the bearings  16   a,    342   a,    361   a  is internally and forcefully lubricated. 
     The compression mechanism  30  includes the stationary scroll  32 , the orbiting scroll  34  and the main bearing member  36 . The stationary scroll  32  is fixed to the second inner circumferential surface  83  of the tubular portion  121   b  through the main bearing member  36 . The orbiting scroll  34  is meshed with the stationary scroll  32  and compresses the refrigerant when the orbiting scroll  34  is driven to make orbiting motion by the drive force of the drive shaft  14 . The orbiting scroll  34  and the stationary scroll  32  are arranged next to each other in the axial direction DRa. The orbiting scroll  34  is located on the other side of the stationary scroll  32  in the axial direction DRa. The stationary scroll  32  and the orbiting scroll  34  are made of a steel material or aluminum alloy. 
     An Oldham ring (not shown) is coupled to the orbiting scroll  34 . The Oldham ring forms an anti-rotation mechanism that limits rotation about the eccentric shaft portion  142 . The orbiting scroll  34  makes the orbital motion around the central axis (serving as an orbital center) CL of the drive shaft  14  without rotating around the eccentric shaft portion  142  when the drive shaft  14  is rotated. In other words, the orbiting scroll  34  makes the orbiting motion around the central axis CL of the drive shaft  14  when the drive shaft  14  is rotated. 
     The orbiting scroll  34  has an orbiting base plate  341  that is shaped in a circular disk form. The orbiting base plate  341  has a bearing forming portion  342  which is shaped in a cylindrical tubular form and is formed at a center part of the orbiting base plate  341 . The bearing forming portion  342  forms the eccentric bearing  342   a,  which is located at an inside of the bearing forming portion  342  and rotatably supports the eccentric shaft portion  142 . The eccentric bearing  342   a  is formed separately from the orbiting base plate  341  and is formed as a sliding bearing. 
     The stationary scroll  32  has a stationary base plate  321  that is shaped in a circular disk form. The stationary scroll  32  has a stationary wrap  322  that is shaped in a spiral form and projects from the stationary base plate  321  toward the orbiting scroll  34 . The orbiting scroll  34  has an orbiting wrap  343  that is shaped in a spiral form and projects from the orbiting base plate  341  toward the stationary scroll  32 . 
     The stationary wrap  322  and the orbiting wrap  343  are meshed with each other at a plurality of locations to form a plurality of operating chambers  31  respectively shaped in a crescent form. In  FIG.  1   , only one of the operating chambers  31  is indicated with the reference sign for convenience of illustration. 
     Each of the operating chambers  31  is moved from the outer peripheral side toward the center side while decreasing a volume of the operating chamber  31  in response to the orbiting of the orbiting scroll  34 . Although not illustrated, the refrigerant, which is suctioned into the inside of the housing  12  from the suction port  125 , is supplied to the operating chamber  31  through a refrigerant supply passage formed at, for example, the main bearing member  36 . The refrigerant in the respective operating chambers  31  is compressed when the volume of the operating chamber  31  is reduced. 
     The discharge hole  323 , through which the refrigerant compressed in the operating chamber  31  is discharged, is formed at a center part of the stationary base plate  321 . A lead valve (not shown) which forms a check valve for limiting a backflow of the refrigerant to the operating chamber  31 , and a stopper  324 , which limits a maximum opening degree of the lead valve, are installed at an end surface  321   a  of the stationary base plate  321 , which is located on the one side in the axial direction DRa. The lead valve and the stopper  324  are securely fixed to the stationary base plate  321  by a fixture bolt  325 . 
     The main bearing member  36  is a bearing member that includes the main bearing  361   a.  The main bearing member  36  forms a space between the main bearing member  36  and the stationary scroll  32 . The eccentric shaft portion  142 , the flange portion  143 , the balance weight  143   a  and the orbiting scroll  34  are received in this space. 
     Specifically, the main bearing member  36  includes a bearing forming portion  361 , a bearing fixing portion  362  and a connecting portion  363 . The bearing forming portion  361 , the bearing fixing portion  362  and the connecting portion  363  are seamlessly and continuously formed in one-piece. The bearing forming portion  361  is shaped in a tubular form. The bearing forming portion  361  forms the main bearing  361   a  at the inside of the bearing forming portion  361 . 
     The bearing fixing portion  362  is a portion of the main bearing member  36  which is fixed to the stationary scroll  32 . The bearing fixing portion  362  is located on a radially outer side of the orbiting scroll  34  in a radial direction of the drive shaft  14 . The bearing fixing portion  362  has an outermost peripheral surface of the main bearing member  36  which has a largest outer diameter at the main bearing member  36 . An end surface  362   a  of the bearing fixing portion  362 , which is located on the one side in the axial direction DRa, contacts the stationary scroll  32 . 
     The connecting portion  363  connects between the bearing forming portion  361  and the bearing fixing portion  362 . The bearing fixing portion  362  is located on the outer side of the bearing forming portion  361  in the radial direction of the drive shaft  14 . The connecting portion  363  extends from the bearing forming portion  361  toward the outside in the radial direction of the drive shaft  14 . 
     The main bearing member  36  is shaped in a cylindrical tubular form that has an inner diameter and an outer diameter which are increased stepwise from the other side toward the one side in the axial direction DRa. A minimum inner diameter portion of the main bearing member  36 , which has the smallest inner diameter at the main bearing member  36 , forms the bearing forming portion  361 . A maximum inner diameter portion of the main bearing member  36 , which has the largest outer diameter at the main bearing member  36 , forms the bearing fixing portion  362 . The bearing forming portion  361 , the bearing fixing portion  362  and the connecting portion  363  are made of a steel material or aluminum alloy. 
     The main bearing  361   a  is a sliding bearing. An inner circumferential surface of the main bearing  361   a  is processed in such a manner that a high degree of coaxiality of the inner circumferential surface of the main bearing  361   a  relative to an outer peripheral surface of the bearing fixing portion  362  is achieved. The main bearing  361   a  is fixed integrally to the main bearing member  36 . Specifically, the main bearing  361   a  includes: a steel member shaped in a cylindrical tubular form; and a resin layer or the like which is coated to an inner circumferential surface of the steel member. Here, it should be noted that the main bearing  361   a  may be made of the same material as that of the bearing forming portion  361  and may be formed integrally in one-piece with the main bearing member  36 . 
     Two thrust plates  364 ,  344 , which are respectively shaped in a circular ring form, are interposed between the main bearing member  36  and the orbiting scroll  34 . Among the thrust plates  364 ,  344 , the thrust plate  364 , which is located on the main bearing member  36  side, is fixed to the main bearing member  36 . Furthermore, the thrust plate  344 , which is located on the orbiting scroll  34  side, is fixed to the orbiting scroll  34  such that the thrust plate  344  and the orbiting scroll  34  integrally rotate. Therefore, the thrust plates  364 ,  344  make relative orbiting motion and thereby slide relative to each other. 
     The compressor  10  includes a plurality of fastening bolts  70  for fastening the constituent components of the compression mechanism  30 . The fastening bolts  70  securely fasten the main bearing member  36  and the stationary scroll  32  together to form the compression mechanism  30 . 
     The fastening bolts  70  include a plurality of primary bolts  71  and a plurality of secondary bolts  72 . The primary bolts  71  fasten only two components, i.e., the stationary scroll  32  and the main bearing member  36  together. The bearing fixing portion  362  has a plurality of female-threaded parts  365  which correspond to male-threaded parts  71   a,  respectively, of the primary bolts  71 . 
     In a state where the bearing fixing portion  362  of the main bearing member  36  is clamped between the stepped portion  80  and the stationary scroll  32 , the secondary bolts  72  fasten the above-described three components together. The stepped portion  80  has a plurality of female-threaded parts  84  which correspond to male-threaded parts  72   a,  respectively, of the secondary bolts  72 . 
     The compression mechanism  30  is inserted into the first housing  121  through the opening  121   a  and is fixed to the first housing  121  in a state where the compression mechanism  30  abuts against the step surface  81  at the inside of the first housing  121 . 
     The compressor  10  includes a main bearing aligning structure that coaxially aligns a central axis of the main bearing  361   a  and a central axis of the second inner circumferential surface  83  of the tubular portion  121   b  to which the compression mechanism  30  is inserted. The main bearing aligning structure includes a socket and spigot fitting structure (or simply referred to as a spigot fitting structure)  91  and a pin fitting structure  92 . 
     The socket and spigot fitting structure  91  is a fitting structure, at which an outer peripheral surface (an outer periphery)  30   a  of the compression mechanism  30  is fitted to the second inner circumferential surface  83  of the tubular portion  121   b  to position the main bearing member  36  in place. The socket and spigot fitting structure  91  of this type can be formed with high precision by machining using general-purpose equipment, such as a lathe. 
     Specifically, the socket and spigot fitting structure  91  is the structure, at which the outer peripheral surface of the bearing fixing portion  362  of the main bearing member  36 , which forms a very small clearance relative to the second inner circumferential surface  83 , is installed to the second inner circumferential surface  83  of the first housing  121 . The outer peripheral surface of the bearing fixing portion  362  is processed to be coaxial with the inner circumferential surface of the main bearing  361   a,  so that the main bearing member  36  can be highly accurately positioned at the inside of the first housing  121  by the socket and spigot fitting structure  91  described above. 
     The pin fitting structure  92  is a fitting structure, at which a common positioning pin  92   c  is fitted into each of a housing hole  92   a  formed at the first housing  121  and a main bearing side hole  92   b  formed at the main bearing member  36  to position the main bearing member  36  in place. 
     The positioning pin  92   c  is a cylindrical member. Each of the housing hole  92   a  and the main bearing side hole  92   b  is a blind hole that has a size which enables insertion of the positioning pin  92   c  therein. The housing hole  92   a  and the main bearing side hole  92   b  are respectively formed at a part of the first housing  121  and a part of the main bearing member  36  which are opposed to each other. Specifically, the housing hole  92   a  is formed at the step surface  81  of the first housing  121 . The main bearing side hole  92   b  is formed at an end surface  362   b  of the bearing fixing portion  362  which contacts the step surface  81  of the first housing  121 . 
     Here, it should be noted that there is a scroll compressor  10  that has a cantilever structure, at which a load of the drive shaft  14  is supported by the main bearing  361   a.  This type of cantilever structure tends to tilt the drive shaft  14  relatively to the bearing. 
     In contrast, in the compressor  10  of the present embodiment, the portion of the drive shaft  14 , which is located on the other side in the axial direction DRa, is rotatably supported by the sub-bearing  16   a  of the sub-bearing member  16 , so that the compressor  10  of the present embodiment has excellent reliability. Hereinafter, the sub-bearing member  16  will be described with reference to  FIGS.  1  and  2   . 
     The sub-bearing member  16  is formed separately from the first housing  121  and is fixed to a bottom surface of the bottom portion  121   c  of the first housing  121 . Specifically, the sub-bearing member  16  is fixed to the bottom surface of the bottom portion  121   c  by a plurality of fastening bolts  18 . 
     The sub-bearing member  16  includes: the body portion  161 , which is shaped in the tubular form; a flange portion  162  which is connected to an end part of the body portion  161 ; and a projection  93   a.  The body portion  161 , the flange portion  162  and the projection  93   a  are made of a steel material or aluminum alloy. The body portion  161 , the flange portion  162  and the projection  93   a  are formed integrally in one-piece as an integrated article. 
     The body portion  161  forms the sub-bearing  16   a  at the inside of the body portion  161 . The sub-bearing  16   a  is a sliding bearing. An inner circumferential surface of the sub-bearing  16   a  is processed in such a manner that a high degree of coaxiality of the inner circumferential surface of the sub-bearing  16   a  relative to an outer peripheral surface of the projection  93   a  is achieved. The sub-bearing  16   a  is fixed integrally to the sub-bearing member  16 . Specifically, the sub-bearing  16   a  includes: a steel member shaped in a cylindrical tubular form; and a resin layer or the like which is coated to an inner circumferential surface of the steel member. Here, it should be noted that the sub-bearing  16   a  may be made of the same material as that of the body portion  161  and may be formed integrally in one-piece with the sub-bearing member  16 . 
     The sub-bearing  16   a  can more effectively provide a tilt support when a distance of the sub-bearing  16   a  from the main bearing  361   a  is increased. In view of this point, at the time of placing the sub-bearing  16   a  away from the main bearing  361   a,  the electric motor unit  20  is interposed between the main bearing  361   a  and the sub-bearing  16   a.  In this way, the space at the inside of the housing  12  can be effectively utilized. 
     The flange portion  162  is a portion that is fixed to the bottom portion  121   c  of the first housing  121 . The flange portion  162  is shaped in a circular ring form. The flange portion  162  outwardly extends in the radial direction of the drive shaft  14 . The flange portion  162  has a plurality of insertion holes  162   a,  into which the fastening bolts  18  are respectively inserted. The number of the insertion holes  162   a  is three, and these insertion holes  162   a  are arranged at equal intervals in the circumferential direction of the flange portion  162 . The number of the fastening bolts  18  is three, and the sub-bearing member  16  of the present embodiment is fixed to the bottom portion  121   c  by these three fastening bolts  18 . The number of the fastening bolts  18  is not limited to three and can be any number that is equal to or larger than one. 
     Here, the compressor  10  includes a sub-bearing aligning structure that coaxially aligns a central axis of the sub-bearing  16   a  and the central axis of the second inner circumferential surface  83  of the tubular portion  121   b.  The sub-bearing aligning structure includes a socket and spigot fitting structure  93 . 
     The socket and spigot fitting structure  93  is a fitting structure, at which a projection formed at one of the first housing  121  and the sub-bearing member  16  is fitted into a recess formed at another one of the first housing  121  and the sub-bearing member  16  to position the sub-bearing member  16  in place. Specifically, the socket and spigot fitting structure  93  is a fitting structure, at which the projection  93   a,  which is formed at the sub-bearing member  16 , is fitted into a recessed hole  93   b,  which is formed at the first housing  121 , to position the sub-bearing member  16  in place. The socket and spigot fitting structure  93  of this type can be formed with high precision by machining using the general-purpose equipment, such as the lathe. In the socket and spigot fitting structure  93  of the present embodiment, the projection  93   a  serves as the projection, and the recessed hole  93   b  serves as the recess. 
     Here, the recessed hole  93   b  is a cylindrical blind hole. The recessed hole  93   b  is formed at a central part of the bottom portion  121   c  such that the central axis of the recessed hole  93   b  is coaxial with the central axis of the second inner circumferential surface  83  of the first housing  121 . The projection  93   a  is shaped in a cylindrical tubular form. The projection  93   a  has an outer peripheral surface that enables fitting of the projection  93   a  to the inside of the recessed hole  93   b.  The outer peripheral surface of the projection  93   a  is processed such that the outer peripheral surface of the projection  93   a  is coaxial with the inner circumferential surface of the sub-bearing  16   a.  Furthermore, an axial length of the projection  93   a  is set to be smaller than an axial length of the recessed hole  93   b  to limit contact of a distal end of the projection  93   a  to a bottom surface of the recessed hole  93   b  at the time of fitting the projection  93   a  into the recessed hole  93   b.    
     The sub-bearing aligning structure of the present embodiment is the socket and spigot fitting structure, at which the outer peripheral surface of the projection  93   a,  which forms a very small clearance relative to the recessed hole  93   b,  is installed to the recessed hole  93   b . The outer peripheral surface of the projection  93   a  is processed to be coaxial with the inner circumferential surface of the sub-bearing  16   a,  so that the sub-bearing member  16  can be highly accurately positioned at the inside of the first housing  121  by the socket and spigot fitting structure  93  described above. 
     The sub-bearing member  16  is configured to be fixed to the bottom portion  121   c  of the first housing  121  in the state where the stator  21  is fixed to the first inner circumferential surface  82  of the tubular portion  121   b.  Specifically, the sub-bearing member  16  is configured such that an outer diameter of the flange portion  162  is smaller than an inner diameter of the stator  21 . 
     Next, a flow of an assembling operation of the constituent components of the compressor  10  will be described with reference to  FIG.  3   . As shown in  FIG.  3   , the assembling operation of the compressor  10  includes: a preparing step; a fixing step of the stator  21 ; an aligning step of the sub-bearing  16   a,  a fixing step of the sub-bearing member  16  and an assembling step of the compression mechanism  30  and the others. 
     In the assembling operation, first of all, at the preparing step at step S 10 , the constituent components of the compressor  10  are prepared. At this preparing step, there is prepared the first housing  121 , which has the first inner circumferential surface  82  and the second inner circumferential surface  83  that are processed in such a manner that a high degree of coaxiality of the first inner circumferential surface  82  and the second inner circumferential surface  83  is achieved. 
     Next, at the fixing step of the stator  21  at step S 20 , the stator  21  of the electric motor unit  20  is fixed to the first inner circumferential surface  82  of the tubular portion  121   b . In the present embodiment, the stator  21  is fixed to the first inner circumferential surface  82  of the first housing  121  by the thermal shrink fit. 
     Next, the aligning step of the sub-bearing  16   a  at step S 30  is a step of coaxially aligning the central axis of the sub-bearing  16   a  and the central axis of the second inner circumferential surface  83  of the tubular portion  121   b.  In this aligning step, the projection  93   a  of the sub-bearing member  16  is fitted into the recessed hole  93   b  of the bottom portion  121   c  of the first housing  121 . At the sub-bearing member  16 , an outer circumferential surface of the projection  93   a  and the inner circumferential surface of the sub-bearing  16   a  are processed in such a manner that a high degree of coaxiality of the outer peripheral surface of the projection  93   a  and the inner circumferential surface of the sub-bearing  16   a  is achieved. Furthermore, the second inner circumferential surface  83  of the tubular portion  121   b  and the recessed hole  93   b  are processed in such a manner that a high degree of coaxiality of the second inner circumferential surface  83  of the tubular portion  121   b  and the recessed hole  93   b  is achieved. Furthermore, a very small clearance is formed between the outer peripheral surface of the projection  93   a  and the inner circumferential surface of the recessed hole  93   b.  Therefore, when the projection  93   a  is fitted into the recessed hole  93   b,  a misalignment of the central axis of the inner circumferential surface of the sub-bearing  16   a  relative to the central axis of the second inner circumferential surface  83  of the tubular portion  121   b  is limited. 
     Next, the fixing step of the sub-bearing  16   a  at step S 40  is a step of fixing the sub-bearing member  16  to the inner surface of the bottom portion  121   c  of the first housing  121  in a state where the central axis of the sub-bearing  16   a  and the central axis of the second inner circumferential surface  83  of the tubular portion  121   b  are coaxially aligned. In this fixing step, the sub-bearing member  16  is fixed to the bottom portion  121   c  of the first housing  121  by the fastening bolts  18 . 
     Next, at the assembling step of the compression mechanism  30  and the others at step S 50 , the main bearing member  36  and the stationary scroll  32  are temporarily assembled by the primary bolts  71  in a state where the drive shaft  14 , the main bearing member  36 , the orbiting scroll  34  and the stationary scroll  32  are assembled together. In this state, by coaxially aligning the main bearing member  36  and the stationary scroll  32 , a deviation between the central axis of the orbiting scroll  34  and the central axis of the stationary scroll  32  is adjusted. 
     Thereafter, the compression mechanism  30  is assembled to the first housing  121 . During the assembling of the compression mechanism  30  to the first housing  121 , the compression mechanism  30  is inserted into the inside of the first housing  121  from the one side in the axial direction DRa. Then, the end surface  362   b  of the main bearing member  36  of the compression mechanism  30  is placed in contact with the step surface  81  of the first housing  121 . In this state, the secondary bolts  72  are inserted from the one side toward the other side in the axial direction DRa. 
     Next, the compression mechanism  30  is securely fastened to the housing  12  by the secondary bolts  72 . Then, after the assembling of the compression mechanism  30  to the first housing  121 , the second housing  122  is fixed to the first housing  121 . Furthermore, the inverter  25  is fixed to the outer surface of the bottom portion  121   c  of the first housing  121  before or after the fixing of the second housing  122  to the first housing  121 . The rotor  22  of the electric motor unit  20  is fixed to the drive shaft  14  in advance by, for example, thermal shrink fit before the assembling of the compression mechanism  30  to the first housing  121 . 
     The compressor  10  described above is applied to the refrigeration cycle device where the refrigerant, which includes the carbon dioxide as its main component, circulates. In this type of refrigeration cycle device, a difference between the high pressure and the low pressure is larger than that of a case where the fluorocarbon refrigerant is used. For this reason, a high load acts on, for example, the main bearing  361   a  and the sub-bearing  16   a  of the compressor  10 , so that a required level of durability for the compressor  10  is high. 
     Therefore, in the compressor  10  of the present embodiment, the sliding bearing, which has the excellent durability, is used as the eccentric bearing  342   a,  the main bearing  361   a  and the sub-bearing  16   a.  As a result, even in the case where the difference between high pressure and low pressure in the cycle is large, and the high load acts on the bearings, the reliability against wear and degradation is improved, and the service life can be extended in comparison to a rolling bearing. 
     Furthermore, in a case where the sliding bearing is used as the main bearing  361   a  and the sub-bearing  16   a,  it is necessary to coaxially align the central axis of the main bearing  361   a  and the central axis of the sub-bearing  16   a  as much as possible from the viewpoint of improving the seizure resistance by limiting a rise of a localized contact pressure, and also the viewpoint of ensuring the wear resistance by good oil film formation. 
       FIG.  4    is an axial cross-sectional view of a compressor CE 1  of a first comparative example of the present embodiment. The compressor CE 1  differs from the compressor  10  of the present embodiment in that the sub-bearing member  16  is integrally formed in one-piece with the bottom portion  121   c,  and that an alignment gap δp for enabling coaxial alignment of the central axes is formed between the outer peripheral surface  30   a  of the compression mechanism  30  and the second inner circumferential surface  83  of the tubular portion  121   b . For convenience, in  FIG.  4   , among the components of the compressor CE 1  of the first comparative example, those corresponding to the components of the compressor  10  of the present embodiment are given the same reference signs as the components of the compressor  10  of the present embodiment. 
     In the compressor CE 1  of the comparative example shown in  FIG.  4   , the sub-bearing member  16  is integrally formed in one-piece with the bottom portion  121   c,  and thereby the position of the sub-bearing  16   a  cannot be adjusted relative to the first housing  121 . Therefore, it is necessitated that assembling equipment is used to detect the central axis of the main bearing  361   a  while displacing the compression mechanism  30  relative to the first housing  121 , and then coaxially align the central axis of the main bearing  361   a  with the central axis of the sub-bearing  16   a,  and thereafter tighten the secondary bolts  72  while maintaining the aligned state of the central axis of the main bearing  361   a  and the central axis of the sub-bearing  16   a.    
     However, the above operation requires repetitions of the accurate detection of the amount of displacement of the central axis of the main bearing  361   a  while displacing the compression mechanism  30 . Therefore, the above operation requires high equipment cost and long cycle time and is not suitable for mass-produced products, such as on-vehicle compressors. 
     In view of the above point, as in a compressor CE 2  of a second comparative example shown in  FIG.  5   , it is conceivable that the alignment gap δp of the compressor CE 1  of the first comparative example is made extremely small, and it is also conceivable that the dimensional and shape tolerances, which have an influence on the variations in the relative coaxiality of the main bearing  361   a  and the sub-bearing  16   a,  are made highly accurate. In the compressor CE 2  of the second comparative example, by simply assembling the constituent components, variations in the coaxiality of the bearings  361   a,    16   a  can be contained within the acceptable range in terms of the quality. 
     In order to generate an oil film effectively in the sliding bearing, it is necessary to make the inner circumferential surface of the sliding bearing smooth and highly accurate. For this reason, in general, polishing of the inner circumferential surface of the sliding bearing is performed. 
     However, if the sub-bearing member  16  is formed integrally in one-piece with the bottom portion  121   c  as in the compressor CE 2  of the second comparative example, it is necessary to increase a length of a shaft of a grindstone in order to polish the sub-bearing  16   a.    
     When the length of the shaft of the grindstone is increased, deflection of the shaft or whirl of the grindstone causes an increase in a difficulty of polishing, and it becomes difficult to obtain the required precision of, for example, the coaxiality, the surface roughness and/or the cylindricity. In order to ensure the required precision, it is necessary to install specialized equipment that enables high-precision machining, and the investment becomes expensive. 
     In view of the above point, in the compressor  10  of the present embodiment, the sub-bearing member  16  is formed separately from the first housing  121  and is fixed to the bottom surface of the bottom portion  121   c  of the first housing  121 . According to this configuration, since the inner circumferential surface of the sub-bearing  16   a  can be processed in the state where the sub-bearing member  16  is removed from the housing  12 , the inner circumferential surface of the sub-bearing  16   a  can be processed with high precision without introducing dedicated equipment. That is, since the polishing of the sub-bearing  16   a  can be performed in the unassembled state of the sub-bearing member  16 , it is not necessary to increase the length of the shaft of the grindstone, and the high polishing precision of the sub-bearing  16   a  can be ensured even with the relatively inexpensive general purpose equipment. 
     Therefore, in the compressor  10 , which includes the first housing  121  shaped in the bottomed tubular form, the precision of the sub-bearing  16   a,  which supports the drive shaft  14  at the bottom portion  121   c  of the first housing  121 , can be ensured without introducing the dedicated equipment. As a result, it is possible to achieve both the productivity and the high quality while limiting the capital investment. 
     This type of compressor  10  is effective for applications with the high durability requirements, such as the refrigeration cycle device where the refrigerant, which includes the carbon dioxide as its main component, is used, and the difference between high pressure and the low pressure in the cycle is large. In addition, the compressor  10  of the present embodiment can be effectively applied as a compressor, such as the on-vehicle compressor that has high needs for compactness, lightweight and low-cost. Furthermore, the compressor  10  of the present embodiment can be effectively applied as a compressor, such as a scroll compressor, which has the following structure. That is, the cantilever structure is used to support the load of the drive shaft  14 , and the relative tilt between the drive shaft  14  and the bearing tends to occur, and the localized contact pressure increase of the bearing is likely to occur. 
     Specifically, the sub-bearing member  16  is fixed to the bottom surface of the bottom portion  121   c  by the fastening bolts  18 . According to this fastening method, the high fastening force can be obtained with the relatively small number of the assembling steps. 
     Particularly, the compressor  10  includes the sub-bearing aligning structure that coaxially aligns the central axis of the sub-bearing  16   a  and the central axis of the second inner circumferential surface  83  of the tubular portion  121   b.  With this structure, a misalignment between the central axis of the sub-bearing  16   a  and the central axis of the second inner circumferential surface  83  of the first housing  121  can be limited. 
     In addition, the compressor  10  includes the main bearing aligning structure that coaxially aligns the central axis of the main bearing  361   a  and the central axis of the second inner circumferential surface  83  of the tubular portion  121   b . With this structure, a misalignment between the central axis of the main bearing  361   a  and the central axis of the second inner circumferential surface  83  of the first housing  121  can be limited. 
     Since the compressor  10  has both the main bearing aligning structure and the sub-bearing aligning structure, a misalignment of the central axis of the inner circumferential surface of the main bearing  361   a  and the central axis of the inner circumferential surface of the sub-bearing  16   a  caused by accumulation of the tolerances at the time of the assembling operation can be highly accurately limited. As a result, the seizure resistance can be improved by limiting the localized contact pressure increase of the respective bearings  361   a,    16   a.  In addition, each bearing  361   a,    16   a  can have a good state of the oil film formation, and thereby the wear resistance can be improved. Thus, the reliability of each bearing  361   a,    16   a  can be improved. 
     Specifically, the sub-bearing aligning structure includes the socket and spigot fitting structure  93 , at which the projection  93   a,  which is formed at the sub-bearing member  16 , is fitted into the recessed hole  93   b,  which is formed at the first housing  121 , to position the sub-bearing member  16  in place. The recessed hole  93   b  and the projection  93   a  of the socket and spigot fitting structure  93  can be formed with high precision by machining using the general-purpose equipment, such as the lathe. Therefore, the positioning precision of the sub-bearing member  16  can be ensured without introducing the dedicated equipment. 
     The main bearing aligning structure includes the socket and spigot fitting structure  91 , at which the outer periphery of the compression mechanism  30  is fitted to the second inner circumferential surface  83  of the first housing  121  to position the main bearing member  36  in place. The socket and spigot fitting structure  91  of this type can be formed with high precision by machining using the general-purpose equipment, such as the lathe. Therefore, the positioning precision of the main bearing member  36  can be ensured without introducing the dedicated equipment. 
     The main bearing aligning structure includes the pin fitting structure  92 , at which the common positioning pin  92   c  is fitted into each of the housing hole  92   a  formed at the first housing  121  and the main bearing side hole  92   b  formed at the main bearing member  36  to position the main bearing member  36  in place. 
     With this structure, the misalignment of the central axis of the main bearing  361   a  relative to the central axis of the second inner circumferential surface  83  of the first housing  121  can be limited, and the main bearing member  36  can be positioned in place in the rotational direction by the positioning pin  92   c.  Therefore, the assemblability of the main bearing member  36  to the first housing  121  can be ensured. In addition, even when the drive force of the electric motor unit  20  is applied to the compression mechanism  30 , which includes the main bearing member  36 , the positioning pin  92   c  functions as a rotation stopper to limit dragged rotation of the main bearing member  36  caused by the drive force of the electric motor unit  20 . 
     Here, in a case where the tubular portion  121   b  and the bottom portion  121   c  of the first housing  121  are formed separately unlike the present embodiment, it is necessary to provide a required wall thickness to each of the tubular portion  121   b  and the bottom portion  121   c  to form bolt seats for fastening the tubular portion  121   b  and the bottom portion  121   c  together by bolts. 
     In contrast, in the compressor  10  of the present embodiment, the first housing  121  is the seamless integral article where the tubular portion  121   b  and the bottom portion  121   c  are integrally formed in one-piece. According to this structure, it is not necessary to provide the additional thickness to each of the tubular portion  121   b  and the bottom portion  121   c  to form the bolt seat, and thereby the required rigidity of each of the tubular portion  121   b  and the bottom portion  121   c  can be obtained with the relatively thin wall thickness of each of the tubular portion  121   b  and the bottom portion  121   c.  This structure reduces the number of the components and ensures the pressure resistance while reducing the weight of the housing  12 . 
     Modifications of First Embodiment 
     In the first embodiment described above, the constituent components and the various structures of the compressor  10  are explained specifically. However, the compressor  10  of the present disclosure is not limited to the above-described compressor  10 , and the above-described compressor  10  may be modified, for example, as follows. It should be noted that the following modifications are not limited to the first embodiment and are equally applicable to the other embodiments. 
     In the first embodiment, there is described the compressor  10  that includes the socket and spigot fitting structure  91  and the pin fitting structure  92  as the main bearing aligning structure. However, the compressor  10  of the present disclosure is not limited to this. The compressor  10  may include, for example, only one of the socket and spigot fitting structure  91  and the pin fitting structure  92 . Furthermore, in the compressor  10 , an alignment gap δp for enabling coaxial alignment of the central axes may be formed between the outer peripheral surface  30   a  of the compression mechanism  30  and the second inner circumferential surface  83  of the first housing  121  in place of the main bearing aligning structure. 
     In the first embodiment described above, as the socket and spigot fitting structure  93 , there is exemplified the structure, at which the projection formed at the sub-bearing member  16  is fitted into the recess formed at the bottom portion  121   c  of the first housing  121 . However, the socket and spigot fitting structure  93  is not limited to this structure. The socket and spigot fitting structure  93  may be, for example, a fitting structure, at which a projection formed at the bottom portion  121   c  of the first housing  121  is fitted into a recess formed at the sub-bearing member  16 . Furthermore, the socket and spigot fitting structure  93  may be a fitting structure, at which a projection, which has a shape other than the circular shape, and a recess, which has a shape corresponding to the shape of the projection, are fitted together while a clearance between the projection and the recess is substantially eliminated. 
     In the first embodiment described above, there is described the example, in which the sub-bearing member  16  includes the flange portion  162  shaped in the circular form. However, the shape of the flange portion  162  is not limited to this shape, and the flange portion  162  may have a shape that is other than the circular form. For example, the flange portion  162  may have an approximately triangular form, as shown in  FIG.  6   . According to this structure, a covered area, which is covered by the flange portion  162  at the bottom surface of the bottom portion  121   c  of the first housing  121 , can be reduced. As a result, interference between the flange portion  162  and the airtight terminals  121   d  can be easily avoided, and thereby a degree of freedom in the layout of the airtight terminals  121   d  can be improved. 
     In the compressor  10  described in the above first embodiment, the compression mechanism  30  is fixed to the first housing  121  by the secondary bolts  72 . If the compression mechanism  30  can be fixed to the first housing  121  by other means, such as clamping of the compression mechanism  30  between the first housing  121  and the second housing  122 , the secondary bolts  72  may be eliminated. Even if the compression mechanism  30  is not fixed, the secondary bolts  72  are not necessarily required. That is, if the compression mechanism  30  is pressed against the step surface  81  between the inner circumferential surfaces  82 ,  83  of the first housing  121  by a pressure difference generated during the operation of the compressor  10  and is substantially fixed in place during the operation by a frictional force generated by the pressure difference, the secondary bolts  72  are not required. In this case, even when the rotational force is applied from the electric motor unit  20  to the compression mechanism  30 , the rotational force is received by the positioning pin  92   c  of the pin fitting structure  92 , and thereby it is possible to limit the positional deviation, such as dragged rotation, of the compression mechanism  30 . 
     Second Embodiment 
     Next, a second embodiment will be described with reference to  FIG.  7   . In the present embodiment, points, which are different from the first embodiment, will be mainly described. 
     In the compressor  10  of the present embodiment, the pin fitting structure  92  described in the first embodiment is eliminated. Furthermore, in place of the socket and spigot fitting structure  93  described in the first embodiment, the sub-bearing aligning structure is formed by a pin fitting structure  94 . The pin fitting structure  94  is a fitting structure, at which a common positioning pin  94   c  is fitted into each of a bottom wall hole  94   a  formed at the bottom portion  121   c  of the first housing  121  and a sub-bearing side hole  94   b  formed at the sub-bearing member  16  to position the sub-bearing member  16  in place. 
     The positioning pin  94   c  is a cylindrical member. The bottom wall hole  94   a  is a blind hole that has a size which enables insertion of the positioning pin  94   c  therein. The sub-bearing side hole  94   b  is a blind hole or a through-hole that has a size which enables insertion of the positioning pin  94   c  therein. The bottom wall hole  94   a  and the sub-bearing side hole  94   b  are respectively formed at a part of the bottom portion  121   c  and a part of the sub-bearing member  16  which are opposed to each other. Specifically, a plurality of bottom wall holes  94   a  are formed at the portion of the bottom surface of the bottom portion  121   c  which is opposed to the flange portion  162 . A plurality of sub-bearing side holes  94   b  are formed at a portion of the flange portion  162  which contacts the bottom surface of the bottom portion  121   c.  A corresponding one of a plurality of positioning pins  94   c  is inserted in a corresponding one of the bottom wall holes  94   a  and a corresponding one of the sub-bearing side holes  94   b  to position the sub-bearing member  16  in place. The fitting between the bottom wall hole  94   a  and the positioning pin  94   c  and the fitting between the sub-bearing side hole  94   b  and the positioning pin  94   c  may be such that only one or both of these two fittings may be press-fitting. In this case, the positioning pin  94   c  is fixed by the press-fitting, and there is no possibility of unintentional removal of the positioning pin  94   c.  Therefore, the sub-bearing side hole  94   b  may be a through-hole. 
     The rest of the structure and the operation are the same as those of the first embodiment. In the compressor  10  of the present embodiment, the sub-bearing aligning structure includes the pin fitting structure  94 . With this structure, the misalignment of the central axis of the sub-bearing  16   a  relative to the central axis of the second inner circumferential surface  83  of the first housing  121  can be limited, and the sub-bearing member  16  can be positioned in place in the rotational direction by the positioning pin  94   c.  As a result, the alignment between the insertion hole  162   a  of the sub-bearing member  16  for the fastening bolt  18  and a threaded hole formed at the bottom portion  121   c  becomes easy, so that the assemblability of the sub-bearing member  16  to the first housing  121  can be sufficiently ensured. 
     Modifications of Second Embodiment 
     In the second embodiment described above, there is described the example, in which the sub-bearing aligning structure is formed by the pin fitting structure  94 . However, the sub-bearing aligning structure is not limited to this structure. For example, the sub-bearing aligning structure may include both of the socket and spigot fitting structure  93  and the pin fitting structure  94 . 
     Third Embodiment 
     Next, a third embodiment will be described with reference to  FIGS.  8  to  10   . In the present embodiment, points, which are different from the second embodiment, will be mainly described. 
     As shown in  FIG.  8   , the compressor  10  of the present embodiment does not have the sub-bearing aligning structure. Specifically, the first housing  121  and the sub-bearing member  16  do not have the structures which correspond to the socket and spigot fitting structure  93  described in the first embodiment and the pin fitting structure  94  described in the second embodiment. 
     In place of these structures, in the compressor  10 , in a state where the central axis of the sub-bearing  16   a  and the central axis of the second inner circumferential surface  83  of the tubular portion  121   b  are coaxially aligned by an aligning jig  95  shown in  FIGS.  9  and  10   , the sub-bearing member  16  is fixed to the bottom surface of the bottom portion  121   c  of the first housing  121 . 
     The aligning jig  95  is a dummy shaft that mimics the drive shaft  14 . The aligning jig  95  can be fitted to both of the inner circumferential surface of the sub-bearing  16   a  and the second inner circumferential surface  83  of the first housing  121 . 
     The aligning jig  95  has: a large diameter portion  95   a  which has an outer diameter that can be fitted to the second inner circumferential surface  83  of the tubular portion  121   b;  and a small diameter portion  95   b  which has an outer diameter that can be fitted to the inner circumferential surface of the sub-bearing  16   a.  The aligning jig  95  is processed such that a central axis of the large diameter portion  95   a  and a central axis of the small diameter portion  95   b  coincide with each other at extremely high precision. The outer diameter of the small diameter portion  95   b  is smaller than the outer diameter of the large diameter portion  95   a.    
     The large diameter portion  95   a  has an approximately cylindrical shape and is processed to such a size that the outer diameter of the large diameter portion  95   a  forms an extremely small clearance relative to the inner diameter of the second inner circumferential surface  83  of the tubular portion  12  lb. As shown in  FIG.  10   , the large diameter portion  95   a  has a plurality of through-holes  95   c  which extend through the large diameter portion  95   a  in the axial direction DRa. Each of these through-holes  95   c  is formed to enable insertion of a bolt fastening jig, which is configured to fasten a corresponding one of the fastening bolts  18 , into the through-hole  95   c.  Each of the through-holes  95   c  is formed at a corresponding location of the large diameter portion  95   a  which is opposed to a corresponding one of the insertion holes  162   a  of the flange portion  162 . 
     The small diameter portion  95   b  has an approximately cylindrical shape and is processed such that the outer diameter of the small diameter portion  95   b  forms an extremely small clearance relative to the inner diameter of the sub-bearing  16   a.  The small diameter portion  95   b  has a tapered portion  95   d  for a guiding purpose at a distal end part of the small diameter portion  95   b,  which is opposite to a connecting portion that connects between the large diameter portion  95   a  and the small diameter portion  95   b.  The tapered portion  95   d  eases insertion of the small diameter portion  95   b  into the inside of the sub-bearing  16   a.    
     Next, an assembling operation of the constituent components of the compressor  10  of the present embodiment will be described. Among the assembling operation of the compressor  10 , those common to the first embodiment will be simplified or omitted from the explanation. 
     In the assembling operation of the compressor  10  of the present embodiment, first of all, at the preparing step, the constituent components of the compressor  10  are prepared. Next, at the fixing step of the stator  21  at step S 20 , the stator  21  of the electric motor unit  20  is fixed to the first inner circumferential surface  82  of the tubular portion  121   b  by the thermal shrink fit. 
     Next, at the aligning step of the sub-bearing  16   a  at step S 30 , first of all, the sub-bearing member  16  is temporarily fixed to the bottom surface of the bottom portion  121   c  by the fastening bolts  18 . In this state, the fastening bolts  18  are not tightened with a prescribed torque, and a position of the sub-bearing member  16  can be shifted. 
     Thereafter, at the aligning step, the aligning jig  95  is fitted into the inside of the first housing  121 . Specifically, at the aligning step, the large diameter portion  95   a  of the aligning jig  95  is fitted to the second inner circumferential surface  83  of the tubular portion  121   b,  and the small diameter portion  95   b  of the aligning jig  95  is fitted to the inner circumferential surface of the sub-bearing  16   a.  At this time, there is established a state where the misalignment between the central axis of the second inner circumferential surface  83  of the tubular portion  121   b  and the central axis of the inner circumferential surface of the sub-bearing  16   a  is limited. 
     Next, at the fixing step of the sub-bearing  16   a  at step S 40 , the fastening bolts  18  are fastened with the prescribed torque to fix the sub-bearing member  16  to the bottom surface of the bottom portion  121   c.  At this step, for each of the fastening bolts  18 , the bolt fastening jig is inserted through the through-hole  95   c  formed through the large diameter portion  95   a,  and the fastening bolt  18  is fastened with the prescribed torque by the bolt fastening jig. 
     Next, at the assembling step of the compression mechanism  30  and the other components at step S 50 , the aligning jig  95  is removed from the inside of the first housing  121 . Thereafter, the assembling of the drive shaft  14  to the sub-bearing  16   a  and the assembling of the compression mechanism  30  to the first housing  121  are performed. 
     According to the assembling operation described above, even in the case where the compressor  10  does not have the sub-bearing aligning structure, the positioning precision of the sub-bearing member  16  can be ensured by the aligning jig  95 . According to this, the relative misalignment between the central axis of the main bearing  361   a  and the central axis of the sub-bearing  16   a  can be limited with high precision while limiting the product cost. 
     Here, at the fixing step of the stator  21 , the first housing  121  is heated to the high temperature to place the first housing  121  in a state of being thermally expanded. Then, the stator  21  is inserted into the heated first housing  121 . Thereafter, the first housing  121  is shrunk to the initial state at the time of cooling the first housing  121  to a normal temperature, so that the stator  21  is fixed to the first housing  121 . 
     In general, in order to limit the loosening of the stator  21  relative to the first housing  121  under the temperature distribution environment in each operating condition of the compressor  10 , it is necessary to increase the tightening margin at the time of executing the thermal shrink fit. However, if the tightening margin is large, the strain of the first housing  121  becomes large. In addition, for example, in the case where the material of the first housing  121  is aluminum alloy or the like, the first housing  121  is likely to be strained due to stress relaxation or the like caused by the high temperature of the first housing  121  at the time of executing the thermal shrink fit. These strains of the first housing  121  will likely cause the misalignment of the central axis of the sub-bearing  16   a.    
     In contrast, in the compressor  10  of the present embodiment, the coaxial alignment of the central axis of the sub-bearing  16   a  by the aligning jig  95  is performed after the fixing step of the stator  21 . Therefore, the sub-bearing member  16  can be fixed to the bottom surface of the bottom portion  121   c  in the state where the misalignment of the central axis caused by the strains of the first housing  121  is canceled by the aligning jig  95 . Specifically, according to the assembling operation of the present embodiment, it is possible to limit the misalignment of the axes with higher precision. 
     Modifications of Third Embodiment 
     In the above embodiment, the specific shape and structure of the aligning jig  95  are described. However, the aligning jig  95  of the present disclosure is not limited to this. The aligning jig  95  may be different from that of the third embodiment as long as it is possible to coaxially align the central axis of the inner circumferential surface of the sub-bearing  16   a  and the central axis of the second inner circumferential surface  83  of the tubular portion  121   b.  In addition, the aligning jig  95  may be formed as a part of another machine rather than as a single unit. 
     Other Embodiments 
     Although the representative embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. For example, according to the present disclosure, the above-described embodiments may be modified as follows. 
     In the above-described embodiments, the sub-bearing member  16  is fixed to the bottom surface of the bottom portion  121   c  by the fastening bolts  18 . However, the sub-bearing member  16  may be fixed to the bottom surface of the bottom portion  121   c  by any other means that is other than the fastening bolts  18 . 
     In the above-described embodiments, there is described the example where the compressor  10  includes the main bearing aligning structure and the sub-bearing aligning structure. However, the main bearing aligning structure and the sub-bearing aligning structure are not essential components, and at least one of the main bearing aligning structure and the sub-bearing aligning structure may be eliminated. 
     In the above-described embodiments, there is described the example where each of the main bearing  361   a  and the sub-bearing  16   a  is formed as the sliding bearing. However, at least one of the main bearing  361   a  and the sub-bearing  16   a  may be formed as another type of bearing that is other than the sliding bearing. 
     In the above-described embodiments, there is described the example where the compressor  10  includes the scroll compression mechanism  30 . However, the compressor  10  of the present disclosure is not limited to this. For example, a rotary compression mechanism  30  or a vane compression mechanism  30  may be employed. 
     In the above-described embodiments, there is described the example where the compressor  10  is applied to the refrigeration cycle device of the vehicle air conditioning device. However, the compressor  10  is not limited to this, and the compressor  10  may be widely applicable to temperature control devices used in houses, factories and the like. Moreover, the compressor  10  is not limited to a horizontal structure, in which the electric motor unit  20  and the compression mechanism  30  are arranged in the horizontal direction. For example, the structure of the compressor  10  may be a vertical structure, in which the electric motor unit  20  and the compression mechanism  30  are arranged in the up-to-down direction DRv. 
     Needless to say, in the above-described embodiments, the elements of each embodiment are not necessarily essential except when it is clearly indicated that they are essential and when they are clearly considered to be essential in principle. 
     In each of the above embodiments, when a numerical value such as the number, numerical value, amount, range or the like of the constituent elements of the embodiment is mentioned, the present disclosure should not be limited to such a numerical value unless it is clearly stated that it is essential and/or it is required in principle. 
     In each of the above embodiments, when the shape, positional relationship or the like of the constituent elements of the embodiment is mentioned, the present disclosure should not be limited such a shape or positional relationship unless it is clearly stated that it is essential and/or it is required in principle. 
     CONCLUSION 
     According to a first aspect presented in part or all of the above-described embodiments, a compressor includes a compression mechanism, an electric motor unit, a drive shaft and a housing. The housing includes a first housing, which is shaped in a bottomed tubular form and has an opening on one side in an axial direction of the drive shaft, and a second housing, which covers the opening of the first housing. A portion of the drive shaft, which is located on the one side in the axial direction, is rotatably supported by a main bearing, which is formed integrally in one-piece with or is fixed to a main bearing member of the compression mechanism. Another portion of the drive shaft, which is located on another side in the axial direction, is rotatably supported by a sub-bearing, which is formed integrally in one-piece with or is fixed to an inside of a body portion of a sub-bearing member. The compression mechanism, which includes the main bearing member, is placed at an inside of a tubular portion of the first housing. The sub-bearing member is formed separately from the first housing and is fixed to a bottom surface of a bottom portion of the first housing. According to this configuration, since the inner circumferential surface of the sub-bearing can be processed in a state where the sub-bearing member is removed from the housing, the inner circumferential surface of the sub-bearing can be processed with high precision without introducing the dedicated equipment. That is, since polishing of the sub-bearing can be performed in the unassembled state of the sub-bearing member, it is not necessary to increase the length of the shaft of the grindstone, and the high polishing precision of the sub-bearing can be ensured even with the relatively inexpensive general purpose equipment. 
     According to a second aspect, the sub-bearing member is fixed to the bottom surface of the bottom portion by a fastening bolt. According to this fastening method, the high fastening force can be obtained with the relatively small number of the assembling steps. 
     According to a third aspect, the compressor includes a sub-bearing aligning structure that is configured to coaxially align a central axis of the sub-bearing and a central axis of an inner circumferential surface of an insertion section of the tubular portion, wherein the insertion section is a section of the tubular portion to which the compression mechanism is inserted. According to this configuration, the misalignment between the central axis of the sub-bearing and the central axis of the inner circumferential surface of the tubular portion is limited. Therefore, a cumulative variation in the relative misalignment amount of the central axis of the respective bearings can be limited. As a result, it is possible to limit a localized contact pressure increase at each bearing and to ensure good oil film formation at each bearing. Therefore, the reliability of each bearing can be ensured. 
     According to a fourth aspect, the sub-bearing aligning structure includes a fitting structure, at which a projection formed at one of the first housing and the sub-bearing member is fitted into a recess formed at another one of the first housing and the sub-bearing member to position the sub-bearing member in place. 
     The projection and the recess of the fitting structure can be formed with high precision by machining using the general-purpose equipment, such as the lathe. Therefore, the positioning precision of the sub-bearing member can be ensured without introducing the dedicated equipment. Thus, the cumulative variation in the relative misalignment amount of the central axis of the respective bearings can be limited. 
     According to a fifth aspect, the sub-bearing aligning structure includes a pin fitting structure, at which a common positioning pin is fitted into each of a bottom wall hole formed at the bottom portion and a sub-bearing side hole formed at the sub-bearing member to position the sub-bearing member in place. 
     With this structure, the misalignment of the central axis of the sub-bearing relative to the central axis of the inner circumferential surface of the tubular portion can be limited, and the sub-bearing member can be positioned in place in the rotational direction by the positioning pin. Thus, assemblability of the sub-bearing member to the first housing can be sufficiently ensured. 
     According to a sixth aspect, the sub-bearing member is fixed to the bottom surface of the bottom portion in a state where a central axis of the sub-bearing and a central axis of an insertion section of the tubular portion, to which the compression mechanism is inserted, are coaxially aligned by an aligning jig that is configured to fit to an inner circumferential surface of the sub-bearing and an inner circumferential surface of the insertion section. 
     With this configuration, the positioning precision of the sub-bearing member can be ensured without adding the sub-bearing aligning structure to the compressor. Therefore, the cumulative variation in the relative misalignment amount of the central axis of the respective bearings can be limited. 
     According to a seventh aspect, the compressor includes a main bearing aligning structure that coaxially aligns a central axis of the main bearing and a central axis of an inner circumferential surface of an insertion section of the tubular portion, wherein the insertion section is a section of the tubular portion to which the compression mechanism is inserted. According to this configuration, the cumulative variation in the relative misalignment amount of the central axis of the respective bearings can be limited. As a result, it is possible to limit a localized contact pressure increase at each bearing and to ensure good oil film formation at each bearing. Therefore, the reliability of each bearing can be ensured. 
     According to an eighth aspect, the main bearing aligning structure includes a fitting structure, at which an outer periphery of the compression mechanism is fitted to the inner circumferential surface of the insertion section to position the main bearing member in place. The fitting structure of this type can be formed with high precision by machining using the general-purpose equipment such as the lathe. Therefore, the positioning precision of the main bearing member can be ensured without introducing the dedicated equipment. Thus, the cumulative variation in the relative misalignment amount of the central axis of the respective bearings can be limited. 
     According to a ninth aspect, the main bearing aligning structure includes a pin fitting structure, at which a common positioning pin is fitted into each of a housing hole formed at the first housing and a main bearing side hole formed at the main bearing member to position the main bearing member in place. 
     With this structure, the misalignment of the central axis of the main bearing relative to the central axis of the inner circumferential surface of the tubular portion can be limited, and the main bearing member can be positioned in place in the rotational direction by the positioning pin. Thus, assemblability of the sub-bearing member to the first housing can be sufficiently ensured. In addition, even when the drive force of the electric motor unit is applied to the compression mechanism, which includes the main bearing member, the positioning pin functions as the rotation stopper to limit dragged rotation of the main bearing member caused by the drive force of the electric motor unit. 
     According to a tenth aspect, at least one of the main bearing and the sub-bearing is a sliding bearing. With this configuration, the bearing of the drive shaft can be made more reliable against wear deterioration and have a longer service life while ensuring seizure resistance of the bearing of the drive shaft. 
     According to an eleventh aspect, the compression mechanism includes: a stationary scroll, which is fixed to the first housing; and an orbiting scroll, which is meshed with the stationary scroll and compresses the fluid when the orbiting scroll makes orbital motion in response to rotation of the drive shaft. According to the scroll compression mechanism with small torque fluctuation, the load on each bearing is limited. Thus, it is possible to ensure seizure resistance and wear resistance of each bearing. 
     According to a twelfth aspect, a method for manufacturing the compressor includes fixing the sub-bearing member to an inner surface of the bottom portion of the first housing in a state where the central axis of the sub-bearing and the central axis of the inner circumferential surface of the insertion section are coaxially aligned. 
     According to a thirteenth aspect, in the method for manufacturing the compressor, coaxially aligning of the central axis of the sub-bearing and the central axis of the inner circumferential surface of the insertion section is implemented by fitting an aligning jig to each of an inner circumferential surface of the sub-bearing and the inner circumferential surface of the insertion section. With this configuration, the positioning precision of the sub-bearing member can be ensured without adding the sub-bearing aligning structure to the compressor. Therefore, relative misalignment between the central axis of the main bearing and the central axis of the sub-bearing can be highly accurately limited.