Abstract:
A two-stage supercharging exhaust turbocharger includes: a high-pressure-stage supercharger having a high-pressure turbine driven by exhaust gas discharged from an exhaust manifold of an engine; a low-pressure-stage supercharger having a low-pressure turbine driven by the exhaust gas used to drive the high-pressure-stage supercharger, the high-pressure-stage supercharger and the low-pressure-stage supercharger being arranged in series in an exhaust gas passageway; and an exhaust gas control valve configured to selectively change flow rates of the exhaust gas passageways of the high-pressure-stage supercharger and the low-pressure-stage supercharger, wherein an exhaust manifold incorporating casing is configured by integrally forming the exhaust manifold, a high-pressure turbine housing of the high-pressure-stage supercharger, and a valve casing accommodating the exhaust gas control valve.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a two-stage supercharging exhaust turbocharger including a high-pressure-stage supercharger driven by exhaust gas discharged from an exhaust manifold of an engine; a low-pressure-stage supercharger driven by the exhaust gas used to drive the high-pressure-stage supercharger, the high-pressure-stage supercharger and the low-pressure-stage supercharger being arranged in series in an exhaust gas passageway; and an exhaust gas control valve configured to selectively change flow rates of the exhaust gas passageways of the high-pressure-stage supercharger and the low-pressure-stage supercharger. 
     2. Description of the Related Art 
     In recent years, a vehicle diesel engine adopts a two-stage supercharging exhaust turbocharger which includes a high-pressure-stage supercharger having a high-pressure turbine driven by exhaust gas discharged from an engine and a low-pressure-stage supercharger having a low-pressure turbine driven by the exhaust gas used to drive the high-pressure-stage supercharger, wherein the high-pressure-stage supercharger and the low-pressure-stage supercharger are arranged in series in an exhaust gas passageway, and wherein air subjected to a first-stage pressurizing operation of the low-pressure compressor of the low-pressure-stage supercharger is subjected to a second-stage pressurizing operation of the high-pressure compressor of the high-pressure-stage supercharger and is supplied to an engine. 
     In the engine provided with the multi-stage supercharging exhaust turbocharger, a two-stage supercharging operation using both the high-pressure-stage supercharger and the low-pressure-stage supercharger is carried out in a low-speed running region, which is advantageous in a transient characteristic and an increase of low-speed torque of the engine. Additionally, a one-stage supercharging operation using the low-pressure-stage supercharger is carried out in a high-speed running region of the engine by allowing the exhaust gas to bypass the high-pressure-stage supercharger. In this manner, it is possible to further improve efficiency of the compressor and thus to realize a reliable running state having an excellent degree of freedom in matching. 
       FIG. 6  is an explanatory view showing an operation of the two-stage supercharging exhaust turbocharger. 
     In  FIG. 6 , Reference Numeral  1  denotes a high-pressure-stage supercharger, where the high-pressure-stage supercharger  1  includes a high-pressure turbine  1   a  and a high-pressure compressor  1   b  coaxially driven by the high-pressure turbine  1   a . Reference Numeral  2  denotes a low-pressure-stage supercharger, where the low-pressure-stage supercharger  2  includes a low-pressure turbine  2   a  and a low-pressure compressor  2   b  coaxially driven by the low-pressure turbine  2   a.    
     The exhaust gas discharged from a cylinder  100  of the engine is collected in an exhaust manifold  103  and is supplied to the high-pressure turbine  1   a  of the high-pressure-stage supercharger  1  via an exhaust pipe  4 . A part of the exhaust gas is supplied to the low-pressure turbine  2   a  of the low-pressure-stage supercharger  2  via an exhaust gas control valve  5 , an exhaust pipe  6 , and an exhaust pipe  10 . 
     Here, the exhaust gas control valve  5  shown in a Y part of  FIG. 6  is provided between the high-pressure-stage supercharger  1  and the low-pressure-stage supercharger  2 , and is used to control a relationship between an amount of the exhaust gas of the high-pressure-stage supercharger  1  and an amount of the exhaust gas bypassing the high-pressure-stage supercharger  1  and supplied to the low-pressure turbine  2   a  of the low-pressure-stage supercharger  2  by controlling an opening degree thereof. That is, the exhaust gas passing through the high-pressure turbine  1   a  of the high-pressure-stage supercharger  1  and an exhaust pipe  8  and the exhaust gas of which a flow rate is controlled by the exhaust gas control valve  5  are mixed at an exhaust pipe  9  and the mixed gas is supplied to the low-pressure turbine  2   a  of the low-pressure-stage supercharger  2  via an exhaust pipe  10 . 
     In the low-pressure-stage supercharger  2 , the low-pressure compressor  2   b  is coaxially driven by the low-pressure turbine  2   a  so as to pressurize air supplied from an air cooler  2   c , and the pressurized air is supplied to the high-pressure compressor  1   b  of the high-pressure-stage supercharger  1  via an air supply pipe  21  and an air supply suction pipe  18 . 
     In the high-pressure-stage supercharger  1 , the high-pressure compressor  1   b  is coaxially driven by the high-pressure turbine  1   a  so as to supply the pressurized air to a cylinder  100  of an engine via an air supply pipe  20 , an intercooler  2   d , an air supply pipe  22 , and an exhaust manifold  101 . 
     Here, a compressor bypass valve unit  05  is provided in a bypass pipe  17  of the high-pressure compressor  1   b  so as to control an amount of air bypassing the high-pressure compressor  1   b.    
     Additionally, a waste gate valve  12  is provided in a bypass pipe  11  of the low-pressure turbine  2   a  so as to control an amount of exhaust gas bypassing the low-pressure turbine  2   a.    
       FIG. 4  is an explanatory view showing a structure of a main part of the two-stage supercharging exhaust turbocharger. 
     In  FIG. 4 , Reference Numeral  1  denotes a high-pressure-stage supercharger, where the high-pressure-stage supercharger  1  includes a high-pressure turbine  1   a  and a high-pressure compressor  1   b  coaxially driven by the high-pressure turbine  1   a . Reference Numeral  2  denotes a low-pressure-stage supercharger, where the low-pressure-stage supercharger  2  includes a low-pressure turbine  2   a  and a low-pressure compressor  2   b  coaxially driven by the low-pressure turbine  2   a.    
     An outlet of the high-pressure turbine  1   a  (not shown in  FIG. 4 ) is connected to a low-pressure connection casing  12  at a connection surface  11   a  by the use of bolts so as to be connected to a low-pressure gas inlet passageway  2   s  of the low-pressure-stage supercharger  2  via the low-pressure connection casing  12 . 
     The compressed air discharged from the low-pressure compressor  2   b  of the low-pressure-stage supercharger  2  is sucked into the high-pressure compressor  1   b  of the high-pressure-stage supercharger  1  via an air supply connection pipe  21  and a high-pressure compressor cover  9 . Here, as described above, a compressor bypass valve unit  05  is provided in a bypass pipe  17  of the high-pressure compressor  1   b  so as to control an amount of air bypassing the high-pressure compressor  1   b  and discharged from an air discharge pipe  18 . 
       FIG. 5A  is a view showing a structure of a low-pressure connection portion and an exhaust manifold portion of the two-stage supercharging exhaust turbocharger shown in  FIG. 4 , and  FIG. 5B  is a sectional view taken along the line Z-Z shown in  FIG. 5A . 
     In  FIG. 5 , Reference Numeral  200  denotes an exhaust manifold portion, where the exhaust manifold  103  is integrally formed with a housing  10  of the high-pressure turbine  1   a  of the high-pressure-stage supercharger  1  by casting. 
     Reference Numeral  103   a  denotes an exhaust gas inlet flange of each cylinder (not shown) of the engine. As shown in  FIG. 5 , a right angle is formed between a flange surface of the exhaust gas inlet flange  103   a  and a flange surface  1   z  of the high-pressure housing  10 , and the flange surface is coupled to an exhaust gas outlet flange (not shown) of each cylinder by the use of a plurality of bolts. 
     As shown in  FIG. 5B , Reference Numeral  201  denotes a low-pressure connection portion. The low-pressure connection casing  12  is provided with the exhaust gas control valve  5  and is integrally formed with an EGR pipe  15 . 
     The exhaust gas control valve  5  provided between the high-pressure-stage supercharger  1  and the low-pressure-stage supercharger  2  controls an opening degree thereof so as to control a relationship between an amount of the exhaust gas of the high-pressure-stage supercharger  1  and an amount of the exhaust gas bypassing the high-pressure-stage supercharger  1  and supplied to the low-pressure turbine  2   a  of the low-pressure-stage supercharger  2 . 
     That is, in  FIG. 5B , the exhaust gas control valve  5  includes a valve member  54  and a valve seat  55  on which the valve member  54  is seated, where one end of the valve member  54  is supported to a rotary shaft  52  so as to be rotatable about a shaft center  52   a  of the rotary shaft  52  in a direction indicated by the arrow W in terms of a support arm  56 . 
     The lower surface  54   a  of the valve member  54  is formed into a plane. When the valve member  54  is swung about the shaft center  52   a  of the rotary shaft  52 , a lower surface  54   a  of the valve member  54  comes into contact with a seat surface  55   a  of the valve seat  55  to thereby close the valve member  54 . 
     Upon opening the valve member  54 , the rotary shaft  52  is rotated in a direction indicated by the arrow W of  FIG. 5  by the use of an exhaust gas control valve driving unit (not shown) to thereby open the valve member  54  in terms of the support arm  56 . 
     Then, the exhaust manifold portion  200  with the above-described configuration and the low-pressure connection portion  201  equipped with the exhaust gas control valve  5  are connected to each other at the connection surface  11   a  by the use of a plurality of bolts. 
     Additionally, Patent Document 1 (Japanese Utility Model Application Laid-Open No. H06-48119) discloses a two-stage exhaust turbocharger in which a high-pressure-stage supercharger and a low-pressure-stage supercharger are connected to each other in terms of a low-pressure connection pipe, an exhaust gas control valve is provided in an inlet of the low-pressure-stage supercharger, and then a part of exhaust gas in the inlet of the low-pressure-stage supercharger is returned to an exhaust manifold. 
     In order to install an engine equipped with the two-stage supercharging exhaust turbocharger in a narrow engine room of a vehicle engine, an installation space in the engine room increases inevitably since the two-stage supercharging exhaust turbocharger is larger than a single-stage supercharging exhaust turbocharger. 
     For this reason, it is required to efficiently install the engine equipped with the two-stage supercharging exhaust turbocharger in the narrow engine room by realizing a compact in size of the structure of the two-stage supercharging exhaust turbocharger to decrease the installation space thereof as small as possible. 
     In the exhaust manifold portion  200  according to the convention art shown in  FIG. 5 , the exhaust manifold  103  is integrally formed with the housing  10  of the high-pressure turbine  1   a  of the high-pressure-stage supercharger  1  by casting. In the low-pressure connection portion  201 , the low-pressure connection casing  12  is provided with the exhaust gas control valve  5  and is integrally formed with the EGR pipe  15 . The exhaust manifold portion  200  and the low-pressure connection portion  201  are connected to each other at the connection surface  11   a  by the use of the plurality of bolts. 
     For this reason, since it is necessary to provide two components, that is, the exhaust manifold portion  200  and the low-pressure connection portion  201 , the number of components increases and the number of assembling processes using a bolt increases. Also, it is necessary to carry out many processes upon separating the exhaust manifold portion  200  and the low-pressure connection portion  201  in the narrow engine room. 
     Additionally, as described above, since it is necessary to provide two components, that is, the exhaust manifold portion  200  and the low-pressure connection portion  201 , the weight of the assembling components increases. 
     SUMMARY OF THE INVENTION 
     The present invention is contrived in consideration of the above-described problems, and an object of the invention is to provide a light and compact two-stage supercharging exhaust turbocharger capable of reducing the weight and the number of components, of reducing the number of assembling processes using a bolt, and of reducing the number of separating processes in a narrow engine room in such a manner that an exhaust manifold portion, in which an exhaust manifold and a high-pressure turbine housing of a high-pressure-stage supercharger are integrally formed with each other by casting, is integrally formed with a low-pressure-stage connection portion mounted with an exhaust gas control valve. 
     In order to achieve the above-described object, according to an aspect of the invention, there is provided a two-stage supercharging exhaust turbocharger including: a high-pressure-stage supercharger having a high-pressure turbine driven by exhaust gas discharged from an exhaust manifold of an engine; a low-pressure-stage supercharger having a low-pressure turbine driven by the exhaust gas used to drive the high-pressure-stage supercharger, the high-pressure-stage supercharger and the low-pressure-stage supercharger being arranged in series in an exhaust gas passageway; and an exhaust gas control valve configured to selectively change flow rates of the exhaust gas passageways of the high-pressure-stage supercharger and the low-pressure-stage supercharger, wherein an exhaust manifold incorporating casing is configured by integrally forming the exhaust manifold, a high-pressure turbine housing of the high-pressure-stage supercharger having a rotary center disposed in parallel to a center of the exhaust manifold, and a valve casing accommodating the exhaust gas control valve and disposed perpendicular to the exhaust manifold and the high-pressure turbine housing. 
     The two-stage supercharging exhaust turbocharger may have the following configuration. 
     (1) The valve casing may include an exhaust gas passageway opened or closed by the exhaust gas control valve and disposed on the side of the exhaust manifold and an exhaust gas passageway disposed on the side of a low-pressure turbine inlet of the low-pressure-stage supercharger. 
     (2) The exhaust manifold incorporating casing may be formed into a single body by casting. 
     (3) A low-pressure inlet casing of the low-pressure-stage supercharger may be directly connected to a lower portion of the exhaust manifold incorporating casing. 
     The conventional art has a configuration in which the exhaust manifold portion and the low-pressure connection portion are formed into separate members and are connected to each other at a connection surface. However, according to the embodiment, since the two-stage supercharging exhaust turbocharger has a configuration in which the exhaust manifold incorporating casing is configured by integrally forming the exhaust manifold, the high-pressure turbine housing of the high-pressure-stage supercharger disposed in parallel to the center of the exhaust manifold, and the valve casing accommodating the exhaust gas control valve and disposed in a direction perpendicular to the exhaust manifold and the high-pressure turbine housing, it is possible to form the exhaust manifold incorporating casing having a single body structure by casting. 
     Accordingly, since the exhaust manifold incorporating casing is configured by forming the functional components into a single body by casting, it is possible to reduce the number of components from two to one, and to reduce the weight. 
     Additionally, it is possible to omit the assembling process in which two components are connected to each other by the use of bolts, and it is not necessary to carry out many processes upon separating the low-pressure connection portion and the exhaust manifold portion from each other in a narrow engine room. Accordingly, it is possible to obtain the two-stage supercharging exhaust turbocharger which is light and compact by reducing the number of components. 
     Furthermore, it is possible to directly connect the low-pressure inlet casing of the common low-pressure-stage supercharger to the lower portion of the exhaust manifold incorporating casing in an easy manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view showing a two-stage supercharging exhaust turbocharger according to an embodiment of the invention. 
         FIG. 2  is a sectional view taken along the line A-A shown in  FIG. 1 . 
         FIG. 3  is a side view showing an exhaust manifold incorporating casing according to the embodiment. 
         FIG. 4  is an explanatory view showing a structure of a main part of the two-stage supercharging exhaust turbocharger. 
         FIG. 5A  is a view showing a structure of a low-pressure connection portion and an exhaust manifold portion of the two-stage supercharging exhaust turbocharger shown in  FIG. 4 , and  FIG. 5B  is a sectional view taken along the line Z-Z shown in  FIG. 5A . 
         FIG. 6  is an explanatory view showing an operation of the two-stage supercharging exhaust turbocharger. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the accompanying drawings. Here, although the dimension, the material, the shape, the relative arrangement, and the like of the component are described in the embodiment, the scope of the invention is not limited thereto so long as a particular description is not made, but those are only examples for a description. 
       FIG. 1  is a side view showing a two-stage supercharging exhaust turbocharger according to an embodiment of the invention.  FIG. 2  is a sectional view taken along the line A-A shown in  FIG. 1 .  FIG. 3  is a side view showing an exhaust manifold incorporating casing according to the embodiment. 
     In  FIG. 1 , Reference Numeral  1  denotes a high-pressure-stage supercharger, where the high-pressure-stage supercharger  1  includes a high-pressure turbine  1   a  and a high-pressure compressor  1   b  coaxially driven by the high-pressure turbine  1   a . Reference Numeral  2  denotes a low-pressure-stage supercharger, where the low-pressure-stage supercharger  2  includes a low-pressure turbine  2   a  and a low-pressure compressor  2   b  coaxially driven by the low-pressure turbine  2   a.    
     In  FIG. 2 , Reference Numeral  205  denotes an exhaust manifold incorporating casing, where the exhaust manifold incorporating casing  205  is connected to a low-pressure inlet casing  10  and the low-pressure inlet casing  10  is connected to the low-pressure turbine  2   a  of the low-pressure-stage supercharger  2 . 
     Then, compressed air discharged from the low-pressure compressor  2   b  of the low-pressure-stage supercharger  2  is sucked into the high-pressure compressor  1   b  of the high-pressure-stage supercharger  1  via an air supply connection pipe  21  and a high-pressure compressor cover  9 . 
     Here, as described above, a compressor bypass valve unit  05  is provided in a bypass pipe  17  of the high-pressure compressor  1   b  so as to control an amount of air bypassing the high-pressure compressor  1   b  and discharged from an air discharge pipe  8 . 
     Next, an attachment portion between an exhaust gas control valve and the exhaust manifold incorporating casing  205  is described in detail in  FIG. 2 . In  FIG. 2 , the exhaust manifold incorporating casing  205  includes a valve casing  53 . 
     One-side exhaust gas discharged from a cylinder of an engine is collected into an exhaust manifold  103  (see  FIG. 3 ) and is supplied to the high-pressure-stage supercharger  1 . Also, the other-side exhaust gas is supplied to the low-pressure-stage supercharger  2  via an exhaust gas control valve  5  and the low-pressure inlet casing  10 . 
     The low-pressure inlet casing  10  is fixed to an attachment surface  42  of the valve casing  53  by the use of a bolt. Additionally, Reference Numeral  40  denotes a cover of a valve chamber  43  formed in the valve casing  53 , the cover being fixed by the use of a plurality of bolts  41 . 
     In the same manner as the conventional art, the exhaust gas control valve  5  is provided with a valve seat  55  fixed to the valve casing  53 . The exhaust gas control valve  5  includes a valve member  54  and the valve seat  55  on which the valve member  54  is seated, where one end of the valve member  54  is supported to a rotary shaft  52  so as to be rotatable about a shaft center  52   a  of the rotary shaft  52  in a direction indicated by the arrow W in terms of a support arm  56 . 
     An outer-peripheral lower surface  54   a  of the valve member  54  is formed into a plane. When the valve member  54  is swung about the shaft center  52   a  of the rotary shaft  52 , the outer-peripheral lower surface  54   a  of the valve member  54  comes into contact with a seat surface  55   a  of the valve seat  55  to thereby close the valve member  54 . 
     Upon opening the valve member  54 , the rotary shaft  52  is rotated in a direction indicated by the arrow W of  FIG. 5  by the use of an exhaust gas control valve driving unit (not shown) to thereby open the valve member  54  via the support arm  56 . 
     The exhaust gas control valve  5  has the above-described configuration, and is used to control a relationship between an amount of the exhaust gas of the high-pressure-stage supercharger  1  and an amount of the exhaust gas supplied to the low-pressure turbine  2   a  of the low-pressure-stage supercharger  2  after bypassing the high-pressure-stage supercharger  1  by controlling an opening degree thereof. 
       FIG. 3  is a side view showing the exhaust manifold incorporating casing  205  according to the embodiment of the invention. 
     In  FIG. 3 , Reference Numeral  205  denotes the exhaust manifold incorporating casing. A plurality of exhaust gas inlet flanges  103   a  is provided and the exhaust manifold  103  is disposed so as to dispose a center  103   z  in an axial direction of the engine. A high-pressure turbine housing  1   as  of the high-pressure-stage supercharger  1  is disposed so as to make a rotary center  1   y  be in parallel to the center  103   z . The valve casing  53  which accommodates the exhaust gas control valve  5  and of which the lower portion is directly connected to the low-pressure inlet casing  10  is disposed so that the center  205   z  of the exhaust gas control valve  5  is perpendicular to the exhaust manifold and the high-pressure turbine housing. 
     Then, the exhaust manifold incorporating casing  205  is formed into a single body by casting. 
     As shown in  FIG. 3 , a right angle is formed between a flange surface of each the exhaust gas inlet flange  103   a  of the cylinder of the engine and a flange surface  1   z  of the high-pressure housing  1   as , and the exhaust gas inlet flange  103   a  is coupled to an exhaust gas outlet flange (not shown) of each cylinder by the use of a plurality of bolts. The valve casing  53  is integrally formed with an EGR pipe  15 . 
     As shown in  FIG. 2 , the valve casing  53  includes an exhaust gas passageway  103   s  disposed on the side of the exhaust manifold  103  and opened or closed by the exhaust gas control valve  5  and an exhaust gas passageway  10   s  formed in the low-pressure inlet casing  10  of the low-pressure-stage supercharger  2 . The low-pressure inlet casing  10  of the low-pressure-stage supercharger  2  is directly connected to the lower portion of the exhaust manifold incorporating casing  205 , that is, the attachment surface  42  provided in the valve casing  53 . 
     The conventional art has a configuration in which the exhaust manifold portion and the low-pressure connection portion are formed into separate members and are connected to each other at a connection surface. However, according to the embodiment, since the exhaust manifold incorporating casing  205  is configured by integrally forming the exhaust manifold  103 , the high-pressure turbine housing  1   as  of the high-pressure-stage supercharger  1  disposed in parallel to the center  103   z  of the exhaust manifold  103 , and the valve casing  53  accommodating the exhaust gas control valve  5  and disposed in a direction perpendicular to the exhaust manifold  103  and the high-pressure turbine housing  1   as , it is possible to form the exhaust manifold incorporating casing  205  having a single body structure by casting. 
     According to the exhaust manifold incorporating casing  205  according to the embodiment, it is possible to reduce the number of components from two to one, and to reduce the weight by integrally forming the casing. 
     Further, it is possible to omit the assembling process in which two components are connected to each other by the use of bolts, and it is not necessary to carry out many processes upon separating the low-pressure connection portion and the exhaust manifold portion from each other in a narrow engine room. Accordingly, it is possible to obtain the two-stage supercharging exhaust turbocharger which is light and compact by reducing the number of components. 
     Furthermore, it is possible to directly connect the low-pressure inlet casing  10  of the common low-pressure-stage supercharger  2  to the lower portion of the exhaust manifold incorporating casing  205  in an easy manner. 
     Industrial Applicability 
     According to the invention, since the exhaust manifold portion, in which the exhaust manifold and the high-pressure turbine housing of the high-pressure-stage supercharger are integrally formed with each other by casting, is integrally formed with the low-pressure connection portion mounted with the exhaust gas control valve, it is possible to provide the light and compact two-stage supercharging exhaust turbocharger capable of reducing the weight and the number of components, of reducing the number of assembling processes using a bolt, and of reducing the number of separating processes in the narrow engine room.