Abstract:
A variable capacity exhaust gas turbocharger having a small thermal capacity and enabling the structure to be simplified. A exhaust gas inlet hardware ( 13 ) having an exhaust gas inlet body ( 11 ) in which an inner side flow passage (U 1 ) communicating with an inner scroll passage (T 1 ) and an outer side flow passage (U 2 ) communicating with an outer scroll flow passage (T 2 ) are formed and a flap valve ( 12 ) for opening and closing the outer side flow passage (U 2 ) are formed at the exhaust gas inlet part of a turbine housing body ( 14 ) in which the inner scroll passage (T 1 ) and the outer scroll flow passage (T 2 ) are formed. A valve recess ( 11   a ) for disposing the flap valve ( 12 ) along the outer side flow passage (U 2 ) and a seat ( 11   b ) for the flap valve for closing the outer side flow passage (U 2 ) are formed in the exhaust gas inlet body ( 11 ). The flap valve ( 12 ) is rotatable about a rotating center positioned in the storage space of the valve recess ( 11   a ) between the position of the flap valve in contact with the seat ( 11   b ) and the position of the flap valve stored in the valve recess ( 11   a ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a variable capacity exhaust gas turbocharger provided with an inner scroll gas passage and an outer scroll gas passage. 
     2. Background of the Invention 
     An exhaust gas turbocharger of a relatively small size is used for an internal combustion engine of vehicle use; the exhaust gas turbocharger is provided with a scroll passage is conventionally used; thereby, the exhaust gas emitted by the engine is charged into the scroll passage that is formed in a turbine housing in which a plurality of nozzle vanes is arranged on the inner periphery side of the scroll passage; after passing through the nozzle vanes, the exhaust gas works on the turbine rotor that is provided inside of the circumference formed by the nozzle vanes. Such a turbocharger of a variable capacity type (a variable nozzle area type) as well as of a radial gas-flow type finds widespread acceptance (see the patent references  1  and  3 , for instance). 
       FIG. 8  depicts a general example of conventional exhaust gas turbochargers of a variable capacity type (having an inner scroll passage and an outer scroll passage); thereby,  FIG. 8  shows a bird&#39; eye view regarding the variable capacity exhaust gas turbocharger of a conventional type, the turbocharger being depicted by use of an exploded view. As shown in  FIG. 8 , the turbocharger is provided with: a turbine housing  1 ; a bearing housing unit  5  coupled to the turbine housing  1 ; and, a compressor housing  2  coupled to the bearing housing unit  5 . Further, in the space that involves the bearing housing unit  5  and the turbine housing  1 , a turbine wheel  3  and a turbine stator  4  are housed; incidentally, a compressor wheel is provided in the turbocharger (in the compressor housing) in response to the turbine wheel, although the compressor wheel is not shown. An opening is formed on an upper side of the turbine housing  1 ; a valve cover  7  is fastened to the turbine housing so as to cover the opening with a gasket  6  between the valve cover  7  and the turbine housing; just below the valve cover, a flow rate control valve  8  is arranged inside the turbine housing  1 . The turbine housing  1  is provided with a plate type inlet flange  1 a that is formed so as to fix the turbine housing  1  to an exhaust gas outlet side of the engine. 
     When the turbocharger which exploded view is depicted in  FIG. 8  is assembled and the turbocharger-mounted engine is operated under a low speed operation condition, the exhaust gas enters an gas inlet opening inside of the plate type inlet flange  1   a  (enters the exhaust gas inlet opening of the turbocharger) and the exhaust gas streams along an inner scroll passage T 1  that forms a spiral shape passage, as shown in  FIG. 9(   a ); thereby, the streamlines of the exhaust gas flow along the inner scroll passage are directed toward the inner side of the spiral scroll. Further, the turbine housing comprises an outer scroll passage T 2  beside the inner scroll passage T 1 ; the inner scroll passage T 1  and the outer scroll passage T 2  are demarcated by a plurality of blades  4   a  of a turbine stator; since the stream lines of the exhaust gas flow along the inner scroll passage are directed toward the inner side of the spiral scroll, the exhaust gas flow in the inner scroll passage T 1  does not enter the outer scroll passage T 2 . 
     On the other hand, when the engine is operated under a high-speed operation condition, a flow rate control valve  8  is pivotally rotated so as to move toward a valve cover  7  as shown in  FIG. 9(   b ); thus, the exhaust gas that enters the turbocharger (the gas inlet opening inside of the plate type inlet flange  1   a ) streams along the inner scroll passage T 1  as well as the outer scroll passage T 2 . In such a manner as shown in  FIG. 9(   a ), the exhaust gas that enters the inner scroll passage T 1  streams along the inner scroll passage T 1 , the streamlines being directed toward the inner side of the spiral scroll. On the other hand, the exhaust gas that enters the outer scroll passage T 2  streams along the spiral of the outer scroll passage T 2 ; and, the exhaust gas streams into the inner scroll passage through the slit area (or the throat area) between a blade  4   a  of the turbine stator and an adjacent blade; thus, the exhaust gas flow in the outer scroll passage joins the exhaust gas flow in the inner scroll passage. Thus, a merging gas flow is formed and streams toward the turbine wheel; then, after passing by the turbine wheel, the exhaust gas is discharged outside of the turbine housing  1 . 
     Incidentally, when the engine is operated under the low speed operation condition as depicted in  FIG. 9(   a ), the exhaust gas streams only in the inner scroll passage T 1 ; thus, the exhaust gas flow speed under the low speed operation condition is faster than that under the high speed operation condition. On the other hand, when the engine is operated under the high speed operation condition as depicted in  FIG. 9(   b ), the exhaust gas streams in and along the inner scroll passage T 1  as well as the outer scroll passage T 2 ; thus, the back pressure regarding the exhaust gas flow is reduced and the fuel consumption is improved. 
     However, in the variable capacity exhaust gas turbocharger of conventional technologies, there exist the components such as the turbine stator  4 , the flow rate control valve  8  and the valve cover; accordingly, the heat capacity (or heat accumulation) regarding the components that form the turbine housing assembly becomes large; thus, the components forming the turbine housing assembly absorb large heat quantity during an engine start transition condition, namely, during a time interval from the time point of the engine start in a cold condition to the time point of the temperature distribution stabilization in a hot operating condition. Hence, it requires longer time for the temperature of the catalyst in the exhaust gas purifying device provided on a downstream side of the exhaust gas outlet of the turbine housing to reach the activation temperature regarding the catalyst. In this way, it is required that the heat capacity of the components that form the turbine housing assembly be reduced. In order to enhance the purifying efficiency, it is preferable to reduce the heat capacity of the turbine housing assembly as small as possible. 
     Further, the configuration in which the valve cover  7  is included is not preferable in view of costs, time and labor in packaging, and possible gas leakage and so on. 
     REFERENCES 
     Patent References 
     Patent Reference 1: JP2008-128056 
     Patent Reference 2: JP2008-215083 
     Patent Reference 3: U.S. Pat. No. 2,860,827 
     SUMMARY OF THE INVENTION 
     Subjects to be Solved 
     In view of the subjects that appears in the conventional technologies, the present invention aims at providing a variable capacity exhaust gas turbocharger, by which the heat capacity, namely, the heat absorption accumulated on the turbine side of the turbocharger is restrained, and the configuration of the turbocharger is simplified. 
     Means to Solve the Subjects 
     In order to provide solutions for the subjects, the present invention discloses a variable capacity exhaust gas turbocharger, comprising:
         a turbine housing in which exhaust gas emitted from an internal combustion engine is guided;   a turbine wheel provided in the turbine housing, the turbine wheel being rotated by the exhaust gas;   an inner scroll passage and an outer scroll passage formed in the turbine housing for dividing a flow of the exhaust gas for rotating the turbine wheel into an inner flow and an outer flow;   a flow rate control valve provided in the turbine housing for controlling a flow rate of the exhaust gas that enters the inner scroll passage and a flow rate of the exhaust gas that enters the outer scroll passage; and   a compressor housing connected to the turbine housing via a bearing housing unit;   wherein the flow rate control valve is a flap valve, and   the variable capacity exhaust gas turbocharger further comprises:   an exhaust gas inlet hardware provided in an exhaust gas inlet part of a turbine housing body inside of which the inner scroll passage and the outer scroll passage are formed, the exhaust gas inlet hardware including:
           an exhaust gas inlet body comprising an inner side flow passage that communicates with the inner scroll passage,   an outer side flow passage that communicates with the outer scroll passage; and   the flap valve that opens and closes the outer side flow passage;   
           wherein   the exhaust gas inlet body comprises:
           a valve recess for the flap valve to be placed therein along the outer side flow passage; and   a seat on which the flap valve sit to shut off the outer side flow passage;   
           further wherein the flap valve has a rotation center placed in a housing space of the valve recess; and   the flap valve rotationally moves around the rotation center between a position where the flap valve is in contact with the seat and a position where the flap valve is housed in the valve recess.       

     According to the present invention as disclosed above, the rotation center of the flap valve is placed in the housing space of the valve recess; around the rotation center, the flap valve rotationally moves between a position where the flap valve keeps contact with the seat and a position where the flap valve is housed in the space of the valve recess; thus, the conventionally used valve cover can be dispensed with; accordingly, there can be no apprehension of gas leakage through the sealing surface of the valve cover; moreover, the configuration of the turbine assembly can be simplified and made compact, and the heat capacity of the components that form the turbine assembly can be reduced. Consequently, the time span during which the catalyst of the exhaust gas purifying device is activated can be shortened. Further, the flap valve is folded into the space of the valve recess, together with the arm member that is connected to the flap valve; thus, the flap valve does not hinder the exhaust gas flow. Accordingly, the pressure drop loss regarding the exhaust gas flow can be restrained, and the turbine efficiency can be enhanced. 
     Still further, since the components such as the valve cover, the gasket and the fitting bolts thereof can be dispensed with, the manufacturing cost can be reduced. 
     A preferable embodiment according to the present invention described above is the variable capacity exhaust gas turbocharger, wherein the exhaust gas inlet hardware is formed as a separated body from the turbine housing body, and fitted to an exhaust gas inlet side of the turbine housing body. 
     According to the embodiment of the present invention as disclosed above, since the exhaust gas inlet hardware is provided as a separated body different from the turbine housing body, the flap valve and an arm member connected to the flap valve can be easily assembled to the exhaust gas inlet hardware. 
     Another preferable embodiment according to the present invention as disclosed above is the variable capacity exhaust gas turbocharger, wherein the exhaust gas inlet hardware comprises a flange part, and a second seat for the flap valve to sit thereon, the second seat being formed on an inner-wall positioned at an inner periphery side of the flange part. 
     According to the embodiment of the present invention as described above, the second seat is formed at the inner periphery side of the flange part on the exhaust gas passage inner-wall of the exhaust gas inlet hardware; the second seat can supply satisfactory strength durability against the seating impacts of the flap valve, even though the flap valve repeats opening/closing movements for long operation hours. In addition, the exhaust gas flow passing through the outer scroll passage can be further accurately shut. 
     Further, the present invention discloses a variable capacity exhaust gas turbocharger, comprising:
         a turbine housing in which exhaust gas emitted from an internal combustion engine is guided;   a turbine wheel provided in the turbine housing, the turbine wheel being rotated by the exhaust gas;   an inner scroll passage and an outer scroll passage formed in the turbine housing for dividing a flow of the exhaust gas for rotating the turbine wheel into an inner flow and an outer flow;   a flow rate control valve provided in the turbine housing for controlling a flow rate of the exhaust gas that enters the inner scroll passage and a flow rate of the exhaust gas that enters the outer scroll passage; and   a compressor housing connected to the turbine housing via a bearing housing unit;   wherein the flow rate control valve is a flap valve, and   the variable capacity exhaust gas turbocharger further comprises:   an exhaust gas inlet hardware provided at an exhaust gas inlet part of a turbine housing body inside of which the inner scroll passage and the outer scroll passage are formed, the exhaust gas inlet hardware comprising:
           an exhaust gas inlet duct into which the exhaust gas streams; and   the flap valve provided to the exhaust gas inlet duct;   
           wherein the gas inlet side of the turbine housing body is provided with a partition wall for separating between the inner scroll passage and the outer scroll passage,   a seat on which the flap valve sits is formed on an end part of the partition wall at the side of the exhaust gas inlet part, and   the flap valve rotationally moves between a position where the flap valve is in contact with the seat and a position where the flap valve is placed along the gas flow direction,   further wherein when the flap valve is placed along the gas flow direction, the flap valve moves into a space outside of an area that is formed by the extension of the exhaust gas inlet duct so that the flap valve does not hinder the exhaust gas flow.       

     According to the present invention as disclosed above, since the flap valve rotationally moves between a position where the flap valve sits on the seat of the partition wall and a position where the flap valve is placed along the gas flow direction, the conventionally used valve cover can be dispensed with; accordingly, there can be no apprehension of gas leakage through the sealing surface of the valve cover; moreover, the configuration of the turbine assembly can be simplified and made compact, and the heat capacity of the components that form the turbine assembly can be reduced. Consequently, the time span during which the catalyst of the exhaust gas purifying device is activated can be shortened. Further, when the engine is operated under a high speed operation condition and the exhaust gas made stream through the outer scroll passage, the flap valve is placed along the gas flow direction; thus, the flap valve does not hinder the exhaust gas flow. More in detail, when the flap valve is placed along the gas flow direction, the flap valve moves into a space outside of an area that is formed by the extension of the exhaust gas inlet duct so that the flap valve does not hinder the exhaust gas flow. Accordingly, the pressure drop loss regarding the exhaust gas flow can be restrained, and the turbine efficiency can be enhanced. Still further, since the components such as the valve cover, the gasket and the fitting bolts thereof can be dispensed with, the manufacturing cost can be reduced. 
     A preferable embodiment according to the present invention as disclosed above is the variable capacity exhaust gas turbocharger, wherein the exhaust gas inlet duct is inserted in an exhaust gas inlet part of the turbine housing body, thereby forming a double tube structure. 
     According to the embodiment of the present invention as described above, the exhaust gas inlet duct is inserted in an outer duct as a gas inlet part of the turbine housing, so that the double tube structure is formed. Hereby, the exhaust gas can stream just inside the exhaust gas inlet duct as the inner side duct of the double tube structure; thus, an air space can be formed between the outer duct and the exhaust gas inlet duct as an inner duct. Thanks to the air space, excellent heat insulation can be achieved, namely, heat dissipation transmitted to the turbine housing can be reduced; the temperature of the exhaust gas can be kept high; and, the time span during which the catalyst of the exhaust gas purifying-device becomes activated can be shortened. 
     Another preferable embodiment according to the present invention as disclosed above is the variable capacity exhaust gas turbocharger, wherein the exhaust gas inlet duct is made of metal sheets. 
     According to the embodiment of the present invention as described above, the exhaust gas inlet duct is formed, being made of thin metal sheets; and, an outer duct as a gas inlet part of the turbine housing surrounds the exhaust gas inlet duct. Thus, the exhaust gas inlet duct and the gas inlet part of the turbine housing form a double tube structure; accordingly, the heat to be transmitted to the turbine housing can be reduced, and the temperature of the exhaust gas can be kept high. As a result, the time span during which the catalyst of the exhaust gas purifying-device becomes activated can be shortened. 
     Further, the present invention discloses a variable capacity exhaust gas turbocharger, comprising:
         a turbine housing in which exhaust gas emitted from an internal combustion engine is guided;   a turbine wheel provided in the turbine housing, the turbine wheel being rotated by the exhaust gas;   an inner scroll passage and an outer scroll passage formed in the turbine housing for dividing   a flow of the exhaust gas for rotating the turbine wheel into an inner flow and an outer flow;   a flow rate control valve provided in the turbine housing for controlling a flow rate of the exhaust gas that enters the inner scroll passage and a flow rate of the exhaust gas that enters the outer scroll passage; and   a compressor housing connected to the turbine housing via a bearing housing unit;   wherein the flow rate control valve is a butterfly valve,   the butterfly valve is provided at the exhaust gas inlet part of the turbine housing body inside of which the inner scroll passage and the outer scroll passage are formed,
           the exhaust gas inlet part of the turbine housing body is provided with a partition wall for separating between the inner scroll passage and the outer scroll passage,   
           a seat on which the butterfly valve sits is formed on an end part of the partition wall at the side of the exhaust gas inlet part, and   the butterfly valve rotationally moves between a position where the butterfly valve sits on the seat and a position where the flap valve is placed along the gas flow direction.       

     According to the present invention as disclosed above, the butterfly valve rotationally moves between a position where the butterfly valve sits on the seat on the partition wall, and a position where the butterfly valve is placed along the gas flow direction; thus, the conventionally used valve cover can be dispensed with; accordingly, there can be no apprehension of gas leakage through the sealing surface of the valve cover; moreover, the configuration of the turbine assembly can be simplified and made compact, and the heat capacity of the components that form the turbine assembly can be reduced. Consequently, the time span during which the catalyst of the exhaust gas purifying device becomes activated can be shortened. 
     Further, since the butterfly valve can be placed along the gas flow direction so that the butterfly valve does not hinder the exhaust gas flow, the pressure drop loss regarding the exhaust gas flow can be restrained, and the turbine efficiency can be enhanced. Still further, since the components such as the valve cover, the gasket and the fitting bolts thereof can be dispensed with, the manufacturing cost can be reduced. 
     A preferable embodiment according to the present invention is the variable capacity exhaust gas turbocharger, comprising 
     a flange part formed at the exhaust gas inlet part of the turbine housing body; and 
     a second seat for the butterfly valve to sit thereon is formed at an inner periphery side of the flange part on an exhaust gas passage inner-wall of the exhaust gas inlet part of the turbine housing body. 
     According to the embodiment of the present invention as described above, a second seat is formed at the inner periphery side of the flange part on the exhaust gas passage inner-wall of the exhaust gas inlet part of the turbine housing body, so that the butterfly valve sits on the second seat. Therefore, the second seat can supply satisfactory strength durability against the seating impacts of the butterfly valve, even though the butterfly valve repeats opening/closing movements for long operation hours. In addition, the exhaust gas flow passing through the outer scroll passage can be further accurately shut. 
     Another preferable embodiment according to the present invention as disclosed above is the variable capacity exhaust gas turbocharger, wherein 
     the butterfly valve is configured to be installed from the exhaust gas inlet part of the turbine housing body. 
     According to the embodiment of the present invention as described above, the butterfly valve can be easily assembled in the turbine housing; thus, TACT time (e.g. inspection time) or manufacturing cost can be reduced. 
     Another preferable embodiment according to the present invention as disclosed above is the variable capacity exhaust gas turbocharger, wherein 
     the butterfly valve slopes so that the exhaust gas smoothly streams into the inner scroll passage when the butterfly valve sits on the seat on the partition wall. 
     According to the embodiment of the present invention as described above, when the butterfly valve sits on the seat on the partition wall, the butterfly valve slopes so that the exhaust gas smoothly streams into the inner scroll passage; thus, the pressure drop loss regarding the exhaust gas flow can be restrained. 
     Another preferable embodiment according to the present invention is the variable capacity exhaust gas turbocharger, wherein the flap valve or the butterfly valve has surface contact with the seat on the partition wall, when the flap valve or the butterfly valve sits on the seat. 
     According to the embodiment of the present invention as described above, the sealing effect during the valve closing duration is enhanced; thus, the exhaust gas streaming through the outer scroll passage is prevented from leaking into the inner scroll passage. Accordingly, the deterioration of the turbine performance is restrained while the flap valve or the butterfly valve sits on the seat 
     Further, the exhaust gas can be prevented from streaming through the outer scroll passage; thus, heat dissipation loss can be restrained. Consequently, the heat capacity (heat accumulation capacity) of the turbine assembly can be reduced; moreover, the time span during which the catalyst of the exhaust gas purifying-device becomes activated can be shortened. 
     Another preferable embodiment according to the present invention is the variable capacity exhaust gas turbocharger, wherein the surface of the seat is grinded. 
     According to the embodiment of the present invention as described above, the surface of the seat on which the flap valve or the butterfly valve sits is grinded; thus, the sealing performance during the valve closing duration regarding each valve can be enhanced. 
     Another preferable embodiment according to the present invention is the variable capacity exhaust gas turbocharger, wherein the turbine housing body is made of metal sheets. 
     According to the embodiment of the present invention as described above, the turbine housing body is formed with metal sheets; the heat capacity of the turbine assembly can be reduced. Consequently, the time span during which the catalyst of the exhaust gas purifying device becomes activated can be shortened. 
     Effects of the Invention 
     The present invention can provide a variable capacity exhaust gas turbocharger; thereby, the heat capacity, namely, the heat absorption accumulated on the turbine side of the turbocharger can be restrained; and, the configuration of the turbocharger can be simplified. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described in greater detail with reference to the preferred embodiments of the invention and the accompanying drawings, wherein: 
         FIG. 1  shows a variable capacity exhaust gas turbocharger according to a first embodiment of the present invention; 
         FIG. 2  shows the inner configuration regarding the turbine housing of the turbocharger depicted in  FIG. 1 ; 
         FIG. 3  shows the movement mechanism (open/close mechanism) regarding the flap valve of the turbine housing depicted in  FIG. 2 ; 
         FIG. 4  shows the inner configuration of a variable capacity exhaust gas turbocharger according to a second embodiment of the present invention; 
         FIG. 5  shows the movement mechanism (open/close mechanism) regarding the flap valve of the turbine housing depicted in  FIG. 4 ; 
         FIG. 6  shows A-A arrow view in  FIG. 4 ; 
         FIG. 7  shows the inner configuration of a variable capacity exhaust gas turbocharger according to a third embodiment of the present invention; 
         FIG. 8  explains a variable capacity exhaust gas turbocharger of a conventional type; 
         FIG. 9(A)  shows the inner configuration regarding the turbine housing of the conventional turbocharger, and explains the exhaust gas flow in the turbine housing when the engine is operated under a low speed operation condition; 
         FIG. 9(B)  shows the inner configuration regarding the turbine housing of the conventional turbocharger, and explains the exhaust gas flow in the turbine housing when the engine is operated under a high speed operation condition. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereafter, the present invention will be described in detail with reference to the embodiments shown in the figures. However, the dimensions, materials, shape, the relative placement and so on of a component described in these embodiments shall not be construed as limiting the scope of the invention thereto, unless especially specific mention is made. 
       FIG. 8  depicts a general example regarding conventional exhaust gas turbochargers of a variable capacity type; thereby,  FIG. 8  shows a bird&#39; eye view regarding the variable capacity exhaust gas turbocharger of a conventional type, the turbocharger being depicted by use of an exploded view. 
     As shown in  FIG. 8 , the turbocharger is provided with: a turbine housing  1 ; a bearing housing unit  5  coupled to the turbine housing  1 ; and, a compressor housing  2  coupled to the bearing housing unit  5 . Further, in the space that involves the bearing housing unit  5  and the turbine housing  1 , a turbine wheel  3  and a turbine stator  4  are housed; incidentally, a compressor wheel is provided in the compressor housing of the turbocharger in response to the turbine wheel, although the compressor wheel is not shown. An opening is formed on an upper side of the turbine housing  1 ; a valve cover  7  is fastened to the turbine housing so as to cover the opening with a gasket  6  between the valve cover  7  and the turbine housing; just below the valve cover, a flow rate control valve  8  is arranged inside the turbine housing  1 . The turbine housing  1  is provided with a plate type inlet flange  1  a that is formed so as to fix the turbine housing  1  to an exhaust gas outlet side of the engine. 
     (First Embodiment) 
       FIG. 1  shows a variable capacity exhaust gas turbocharger according to a first embodiment of the present invention. 
     The variable capacity exhaust gas turbocharger according to the first embodiment comprises: a turbine housing  1  in which the exhaust gas emitted from the internal combustion engine is guided; a turbine wheel  3  provided in the turbine housing  1 , the turbine wheel being rotated by the exhaust gas. 
     Further, the turbocharger further comprises: a bearing housing unit  5  that is coupled to the turbine housing  1 ; a compressor housing  2  that is coupled to the bearing housing unit  5 , the bearing housing unit  5  being arranged so as to be fitted in the inner side of the compressor housing  2 . 
     Further, in the space that involves the bearing housing unit  5  and the turbine housing  1 , a turbine wheel  3  and a turbine stator  4  are housed; incidentally, a compressor wheel is provided in the turbocharger in response to the turbine wheel, although the compressor wheel is not shown. In addition, in this embodiment, the turbine housing  1  is made of metal sheets; thus, the heat capacity (heat accumulation capacity) can be restrained. 
       FIG. 2  shows the inner configuration regarding the turbine housing of the turbocharger, so as to focus on the remarkable feature of the present invention. As shown in  FIG. 2 , inside of the turbocharger turbine housing  1 , an inner scroll passage T 1  and an outer scroll passage T 2  are formed; namely, the exhaust gas flow space inside the turbine housing is demarcated into the inner scroll passage T 1  and the outer scroll passage T 2 ; thereby, the exhaust gas that rotationally drives the turbine wheel after passing through the scroll passages (through the inner scroll passage or through both the inner and outer scroll passages). Further, in the turbine housing, a flap valve  12  is provided so that the flap valve  12  controls the ratio between the gas flow rate of the exhaust gas that enters the inner scroll passage T 1  and the gas flow rate of the exhaust gas that enters the inner scroll passage T 1 . In addition, the turbine housing  1  is provided with an exhaust gas inlet hardware  13  at the gas inlet side of a turbine housing body  14 ; thereby, the exhaust gas inlet hardware  13  includes: an exhaust gas inlet body  11  comprising an inner side flow passage U 1  that communicates with the inner scroll passage T 1 , and an outer side flow passage U 2  that communicates with the outer scroll passage T 2 ; and, the flap valve  12  that opens and closes the outer side flow passage U 2 . 
     In this embodiment, the turbine housing comprises the turbine housing body  14 , and the exhaust gas inlet hardware  13  that is formed as a separated body different from the turbine housing body  14 ; and, the exhaust gas inlet hardware  13  can be fixed to the turbine housing body  14 , for example, by means of welding, after the flap valve  12  and an arm member  15  connected to the flap valve  12  are easily assembled to the exhaust gas inlet hardware  13 . 
     Further, the exhaust gas inlet body  11  comprises: a valve recess (space)  11   a  that makes the flap valve take shelter so that the outer side flow passage U 2  forms a smooth flow passage when the flap valve is opened; a seat  11   b  on which the flap valve sit when the flap valve is closed so as to shut the outer side flow passage U 2 . 
     Further, on the exhaust gas inlet side of the turbine housing body  14 , a gas inlet side plate  11   c  that forms a plate type inlet flange is provided so as to fix the turbine housing  1  to an exhaust gas outlet side of the engine; on the exhaust gas passage wall at the inner periphery side of the gas inlet side plate  11   c , a second seat  11   c   1  is formed so that the flap valve  12  sits on the second seat. Therefore, the second seat can supply satisfactory strength durability against the seating impacts of the flap valve  12 , even though the flap valve repeats opening/closing movements for long operation hours. In addition, the exhaust gas flow passing through the outer scroll passage T 2  can be further accurately shut. 
     As shown in  FIG. 2 , the rotation center of the flap valve  12  is placed in the housing space of the valve recess  11   a ; around the rotation center, the flap valve  12  rotationally moves between a position (the solid line for the valve  12  in  FIG. 2 ) where the flap valve  12  keeps contact with the seat  11   b  and a position (the dotted line for the valve  12  in  FIG. 2 ) where the flap valve  12  is housed in the space of the valve recess  11   a . As shown in  FIG. 3 , the flap valve  12  of, for example, a disk shape rotationally moves by the driving movements via an arm member  15  and a lever member  16 . 
     Further, as shown in  FIG. 2 , since the flap valve  12  has surface contact with the seat  11   b  when the flap valve sits on the seat, the sealing effect during the valve closing duration is enhanced; thereby, the exhaust gas is prevented from streaming through the outer scroll passage T 2 . Accordingly, the deterioration of the turbine performance is restrained while the flap valve sits on the seat. 
     In addition, since the seat  11   b  is grinded (e.g. polished), the performance of the sealing between the valve  12  and the seat  11   b  can be enhanced. 
     Further, when the engine is operated under a low speed operation condition, the exhaust gas enters the gas inlet side plate  11   c  and streams along the inner scroll passage T 1  that forms a spiral shape passage; thereby, the streamlines of the exhaust gas flow along the inner scroll passage are directed toward the inner side of the spiral scroll. The inner scroll passage T 1  and the outer scroll passage T 2  are demarcated by a partition wall  14   a ; on the downstream side from the trailing edge of the partition wall  14   a , a plurality of blades  4   a  of the turbine stator  4  that is shown in  FIG. 1  (not shown in  FIG. 2 ) are arranged; the upstream side of each blade forms a comparatively mild slope (e.g. angle of attack), while the downstream side of the blade forms a comparatively steep slope. Further, each blade is arranged so as to have a predetermined inclined angle against the hoop direction, the hoop crossing each blade; since the stream lines of the exhaust gas flow along the inner scroll passage are directed toward the inner side of the spiral scroll, the exhaust gas flow in the inner scroll passage T 1  does not enter the outer scroll passage T 2 . 
     On the other hand, when the engine is operated under a high-speed operation condition, the flap valve  12  rotationally moves toward the space of the valve recess  11   a  as shown in  FIG. 2 ; thus, the exhaust gas that enters the gas inlet side plate  11   c  streams along the inner scroll passage T 1  as well as the outer scroll passage T 2 . The exhaust gas that enters the inner scroll passage T 1  streams along the inner scroll passage T 1 , the streamlines being directed toward the inner side of the spiral scroll. On the other hand, the exhaust gas that enters the outer scroll passage T 2  streams along the spiral of the outer scroll passage T 2 ; and, the exhaust gas streams into the inner scroll passage through the throat area (or slit area) between a blade  4   a  of the turbine stator and an adjacent blade; thus, the exhaust gas flow in the outer scroll passage joins the exhaust gas flow in the inner scroll passage. After the merging gas flow streams through the turbine wheel, the exhaust gas is discharged outside of the turbine housing  1 . 
     According to this first embodiment, the rotation center of the flap valve  12  is placed in the housing space of the valve recess  11   a ; around the rotation center, the flap valve  12  rotationally moves between a position where the flap valve  12  keeps contact with the seat  11   b  and a position where the flap valve  12  is housed in the space of the valve recess  11   a ; thus, the conventionally used valve cover can be dispensed with; accordingly, there can be no apprehension of gas leakage through the sealing surface of the valve cover; moreover, the configuration of the turbine housing assembly can be simplified and made compact, and the heat capacity of the components that form the turbine housing assembly can be reduced. Consequently, the time span during which the catalyst of the exhaust gas purifying device is activated is shortened. Further, the flap valve  12  is folded into the space of the valve recess  11   a , together with the arm member  15  that is connected to the flap valve  12 ; thus, the flap valve does not hinder the exhaust gas flow. Accordingly, the pressure drop loss regarding the exhaust gas flow can be restrained, and the turbine efficiency can be enhanced. Still further, since the components such as the valve cover, the gasket and the fitting bolts thereof can be dispensed with, the manufacturing cost can be reduced. 
     (Second Embodiment) 
       FIG. 4  shows the inner configuration of a variable capacity exhaust gas turbocharger according to a second embodiment of the present invention; incidentally, the same component in this second embodiment as in the first embodiment is quoted with a common alphanumeric, and the explanation repetition will be omitted. 
     As shown in  FIG. 4 , an exhaust gas inlet hardware  13  is provided at the inlet of a turbine housing body  14  in which an inner scroll passage T 1  and an outer scroll passage T 2  are demarcated by a partition wall  14   a ; thereby, the exhaust gas inlet hardware  13  comprises: an exhaust gas inlet duct  17  through which the exhaust gas streams; and a flap valve  12  that is provided in the exhaust gas inlet duct  17 . The exhaust gas inlet duct  17  is formed, being made of metal sheets; and, a duct part as the gas inlet part of the turbine housing surrounds the exhaust gas inlet duct  17 . Thus, the exhaust gas inlet duct  17  and the gas inlet part of the turbine housing form a double tube structure; accordingly, the heat to be transmitted to the turbine housing is reduced, and the temperature of the exhaust gas is kept high. As a result, the time span during which the catalyst of the exhaust gas purifying-device becomes activated can be shortened. 
     Further, at an end part of the gas inlet side regarding the partition wall  14   a , a seat  14   a   1  is formed so that the flap valve  12  sits on the seat  14   a   1 , the flap valve having surface contact with the seat  14   a   1 . Thanks to the surface contact, the performance of the sealing between the flap valve  12  and the seat  14   a   1  can be enhanced. 
     According to this embodiment, the flap valve  12  rotationally moves between a position where the flap valve  12  sits on the seat  14   a   1  of the partition wall  14   a  and a position where the flap valve  12  is placed along the gas flow direction. 
     As illustratively shown in  FIG. 5 , the flap valve  12  opens and closes by the movements of the arm member and the lever member  16 . In this embodiment, a rectangular platy member forms the flap valve  12 . 
     Further, as shown in  FIG. 6 , in this embodiment, the exhaust gas inlet duct  17  is inserted in a duct part (an outer duct  14   b ) as a gas inlet part of the turbine housing, so that the double tube structure is formed. Hereby, the exhaust gas can stream just inside the exhaust gas inlet duct  17  as the inner side duct of the double tube structure; thus, an airspace S can be formed between the outer duct  14   b  and the exhaust gas inlet duct  17  as an inner duct. Thanks to the airspace S, excellent heat insulation can be achieved, namely, heat dissipation transmitted to the turbine housing can be reduced; the temperature of the exhaust gas can be kept high; and, the time span during which the catalyst of the exhaust gas purifying-device becomes activated can be shortened. 
     In this second embodiment, since the flap valve  12  rotationally moves between a position where the flap valve  12  sits on the seat  14   a   1  of the partition wall  14   a  and a position where the flap valve  12  is placed along the gas flow direction, the conventionally used valve cover can be dispensed with; accordingly, there can be no apprehension of gas leakage through the sealing surface of the valve cover; moreover, the configuration of the turbine housing assembly can be simplified and made compact, and the heat capacity of the components that form the turbine housing assembly can be reduced. Consequently, the time span during which the catalyst of the exhaust gas purifying device is activated is shortened. Further, when the engine is operated under a high speed operation condition and the exhaust gas is made stream through the outer scroll passage T 2 , the flap valve  12  is placed along the gas flow direction; thus, the flap valve does not hinder the exhaust gas flow. More in detail, when the flap valve  12  is placed along the gas flow direction, the flap valve  12  moves into a space outside of an area that is formed by the extension of the exhaust gas inlet duct  17  so that the flap valve does not hinder the exhaust gas flow. Accordingly, the pressure drop loss regarding the exhaust gas flow can be restrained, and the turbine efficiency can be enhanced. Still further, since the components such as the valve cover, the gasket and the fitting bolts thereof can be dispensed with, the manufacturing cost can be reduced. 
     (Third Embodiment) 
       FIG. 7  shows the inner configuration of a variable capacity exhaust gas turbocharger according to a third embodiment of the present invention; incidentally, the same component in this third embodiment as in the first embodiment is quoted with a common alphanumeric, and the explanation repetition will be omitted. 
     As shown in  FIG. 7 , a butterfly valve  12 A is provided at the exhaust gas inlet part of the turbine housing body  14  inside which an inner scroll passage T 1  and an outer scroll passage T 2  are formed; a partition wall  14   a  is provided in the exhaust gas inlet part of the turbine housing body  14  so that the inner scroll passage T 1  and the outer scroll passage T 2  are demarcated. At an end part of the gas inlet side regarding the partition wall  14   a , a seat  14   a   1  is formed so that the butterfly valve  12 A sits on the seat  14   a   1 . Further, a flange  14   c  is formed at the exhaust gas inlet part of the turbine housing body  14 ; on the exhaust gas passage wall at the inner periphery side of the flange  14   c , a second seat  14   c   1  is formed so that the butterfly valve  12 A sits on the second seat  14   c   1 . Therefore, the second seat  14   c   1  can supply satisfactory strength durability against the seating impacts of the butterfly valve  12 A, even though the butterfly valve  12 A repeats opening/closing movements for long operation hours. In addition, the exhaust gas flow passing through the outer scroll passage T 2  can be further accurately shut. 
     The butterfly valve  12 A rotationally moves between a position where the butterfly valve  12 A sits on the seats  14   a   1  and  14   c   1 , and a position where the butterfly valve  12 A is placed along the gas flow direction. 
     Further, the butterfly valve  12 A is designed so that the butterfly valve  12 A can be installed from the gas inlet side of the turbine housing  1 ; hence, the butterfly valve can be easily assembled in the turbine housing; thus, TACT time (e.g. inspection time) or manufacturing cost can be reduced. 
     When the butterfly valve  12 A sits on the seat  14   a   1 , the butterfly valve  12 A slopes so that the exhaust gas smoothly streams into the inner scroll passage T 1 ; thus, the pressure drop loss regarding the exhaust gas flow can be restrained. 
     Further, since the butterfly valve  12 A has surface contact with the seats  14   a   1  and  14   c   1 , the sealing effect during the valve closing duration is enhanced; thereby, the exhaust gas is prevented from streaming through the outer scroll passage T 2 . 
     In this third embodiment, the butterfly valve  12 A rotationally moves between a position where the butterfly valve  12 A sits on the seats  14   a   1  and  14   c   1 , and a position where the butterfly valve  12 A is placed along the gas flow direction; thus, the conventionally used valve cover can be dispensed with; accordingly, there can be no apprehension of gas leakage through the sealing surface of the valve cover; moreover, the configuration of the turbine housing assembly can be simplified and made compact, and the heat capacity of the components that form the turbine housing assembly can be reduced. Consequently, the time span during which the catalyst of the exhaust gas purifying device becomes activated is shortened. 
     Further, since the butterfly valve  12 A can be placed along the gas flow direction so that the butterfly valve  12 A does not hinder the exhaust gas flow, the pressure drop loss regarding the exhaust gas flow can be restrained, and the turbine efficiency can be enhanced. Still further, since the components such as the valve cover, the gasket and the fitting bolts thereof can be dispensed with, the manufacturing cost can be reduced. 
     Incidentally, the present invention shall not be construed as limiting the scope thereof to the embodiments as is described thus far; it is needless to say that there can be various kinds of modified embodiments within the bounds of the features of the present invention. 
     Industrial Applicability 
     According to the present invention, a variable capacity exhaust gas turbocharger can be provided; thereby, the heat capacity, namely, the heat absorption accumulated on the turbine side of the turbocharger can be restrained; and, the configuration of the turbocharger can be simplified. The configuration according to the features of the present invention can be applied to the products in the technical field of turbochargers.