Exhaust gas purification device for internal combustion engine

Abstract

An exhaust gas purification device (1) for measuring air / fuel ratio accurately and for enhancing a purification performance without increasing a size of a catalyst. The exhaust gas purification device (1) comprises: header pipes through which exhaust gas flows; a catalytic converter (3) arranged downstream of the header pipes; a diffusion chamber (4) arranged between the header pipe and the catalytic converter (3); and a receiving surface (4a) with which the exhaust gas flowing into the diffusion chamber (4) collides. An orifice (5) is formed in a downstream end plate of the diffusion chamber (4), and an air / fuel ratio sensor (7) is arranged downstream of the orifice (5).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present invention claims the benefit of Japanese Patent Application No. 2024-087800 filed on May 30, 2024 with the Japanese Patent Office, the invention of which is incorporated herein by reference in its entirety.BACKGROUND Field of the Invention

[0002] Embodiments of the present invention relate to the art of an exhaust gas purifying device for an internal combustion engine, and especially to an exhaust gas purifying device in which a catalytic converter in arranged in the vicinity of an engine having an exhaust pipe connected to a plurality of cylinders.Discussion of the Related Art

[0003] In the internal combustion engines, a catalytic converter may have to be offset significantly from a center in an array direction of cylinders. JP-A-2014-211111 discloses an exhaust pipe structure adapted to introduce exhaust gas into a catalytic converter in a well-balanced manner.

[0004] In the exhaust pipe structure described in JP-A-2014-211111, exhaust passages are connected individually to cylinders, and exhaust gas flowing through the exhaust passage is guided to the catalytic converter through a swirl structure of a collection part formed between the first exhaust passage and the second exhaust passage.

[0005] In the exhaust pipe structure described in JP-A-2014-211111, although the catalyst converter is significantly offset from the center of the row of the cylinders, the exhaust gas may be introduced to the catalytic converter in a well-balanced manner. However, since a swirl flow of the exhaust gas tends to flow outer side in the passage, the exhaust gas may not be not allowed to flow efficiently through a center portion of the catalyst. In addition, since the collection part at which the flows of the exhaust gas converge is formed between the first exhaust passage and the second exhaust passage, flow rates of the flows of the exhaust gas flowing through the first exhaust passage and the second exhaust passage are increased. That is, a time period in which the exhaust gas flows within the catalyst is shortened. Therefore, in order to ensure a purifying performance of the catalyst, it is necessary to enlarge the catalyst. However, if the catalyst is enlarged, a loss of pressure in the exhaust gas purifying device may be increased.

[0006] JP-A-2024-79990 discloses an exhaust gas control apparatus for enhancing a purifying performance of a catalyst without enlarging the catalyst. The exhaust gas control apparatus taught by JP-A-2024-79990 is applied to an internal combustion engine having a plurality of cylinders, a plurality of exhaust passages communicating with the plurality of cylinders, and a catalytic converter. In the engine to which the exhaust gas control apparatus taught by JP-A-2024-79990 is applied, a diffusion portion that promotes a jet flow of the exhaust gas flowing into a merging portion is provided at the merging portion connected to a downstream side of the exhaust passage. The diffusion portion includes a dispersion face that is substantially perpendicular to a flowing direction of the exhaust gas so that the main flow of the exhaust gas that has flowed linearly into the merging portion collides with the dispersion face to be dispersed. According to the teachings of JP-A-2024-79990, therefore, the flow rate of the exhaust gas passing through the catalyst can be reduced, whereby the purification characteristics can be improved without increasing the size of the catalyst. In addition, in the exhaust gas control apparatus taught by JP-A-2024-79990, an air / fuel ratio sensor is provided at a portion where the main flow of the exhaust gas flowing into the merging portion from the exhaust passages is alternating with each other. According to the teachings of JP-A-2024-79990, therefore, the flow rate of the exhaust gas discharged from the respective cylinders is fast and collides with the air / fuel ratio sensor so that the sensor responsiveness can be secured.

[0007] However, if the air / fuel ratio sensor is arranged at the diffusion portion where the flows of exhaust gas converge, an air / fuel ratio may not be measured accurately. Fig. 1 shows an example of an exhaust gas purification device to which the teachings of JP-A-2024-79990 is applied. The purification device 100 shown in Fig. 1 comprises: an exhaust manifold 104 including paired header pipes 101, 102, and 103 individually connected to cylinders of an engine (not shown); a collector 104a at which the paired header pipes 101, 102, and 103 converge; a collector pipe 104b joined to a downstream side of the collector 104a; a diffusion chamber 105 in which a jet flow of the exhaust gas is created and which is joined to the collector pipe 104b; a catalytic converter 106 joined to a downstream side of the diffusion chamber 105; and an air / fuel ratio sensor 107 arranged in the vicinity of an inlet 105a of the diffusion chamber 105 from which the exhaust gas flows into the diffusion chamber 105. In the purification device 100, the exhaust gas emitted from an engine flow into the collector pipe 104b from different directions. Therefore, flowing directions of the exhaust gas passing through the air / fuel ratio sensor 107 vary as indicated by the arrows a, b, and c. That is, the flows of the exhaust gas come into contact with the air / fuel ratio sensor 107 unevenly. In addition, since the air / fuel ratio sensor 107 is arranged in the diffusion chamber 105, an air-fuel ratio may be measured before the flows of the exhaust gas are mixed completely. Therefore, the air / fuel ratio measured by the air / fuel ratio sensor 107 may be varied, and the engine may not be controlled properly based on the air / fuel ratio measured by the air / fuel ratio sensor 107.SUMMARY

[0008] Aspects of embodiments of the present invention have been conceived noting the foregoing technical problems, and it is therefore an object of the present invention to provide an exhaust gas purification device for an internal combustion engine configured to enhance a purification performance and to measure an exhaust air / fuel ratio accurately.

[0009] In order to achieve the above-explained objective, according to the exemplary embodiment of the present invention, there is provided an exhaust gas purification device for an internal combustion engine, comprising: at least one or more header pipe through which an exhaust gas emitted from cylinders of the engine flows; a catalytic converter arranged downstream of the header pipe; a diffusion chamber arranged between the header pipe and the catalytic converter; a receiving surface formed in the diffusion chamber with which a mainstream of the exhaust gas flowing into the diffusion chamber via the header pipe collides; an orifice formed in a downstream end plate of the diffusion chamber, a cross-sectional area thereof is smaller than a cross-sectional area of an internal space of the diffusion chamber; and an air / fuel ratio sensor arranged downstream of the orifice to measure an air / fuel ratio of an air / fuel mixture supplied to the engine.

[0010] In a non-limiting embodiment, the orifice may be formed in the downstream end plate of the diffusion chamber at a portion where an inner edge of the orifice is distant from the receiving surface of the diffusion chamber.

[0011] In a non-limiting embodiment, the orifice may be formed on the downstream end plate of the diffusion chamber at a portion where a predetermined clearance is maintained between an inner edge of the orifice and the receiving surface of the diffusion chamber in a flowing direction of the mainstream of the exhaust gas flowing toward the receiving surface.

[0012] In a non-limiting embodiment, the exhaust gas purification device may further comprise a retention surface formed on at least a portion of the downstream end plate between the receiving surface of the diffusion chamber and the inner edge of the orifice so as to prevent the exhaust gas colliding with the receiving surface from flowing into the catalytic converter.

[0013] In the exhaust gas purification device according to the exemplary embodiment of the present invention, flows of the exhaust gas emitted from cylinders of the engine flow into the diffusion chamber to be diffused and agitated. According to the exemplary embodiment of the present invention, therefore, a flow rate of the exhausted gas passing through the catalytic converter may be reduced. For this reason, a purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst. In addition, in the exhaust gas purification device according to the exemplary embodiment of the present invention, the orifice is formed in the downstream end plate of the diffusion chamber. Further, the catalytic converter is connected to the orifice, and the air / fuel ratio sensor is arranged downstream of the orifice. According to the exemplary embodiment of the present invention, therefore, the air / fuel ratio of the air / fuel mixture may be measured from the exhaust gas after the flows of the exhaust gas emitted from the header pipes are mixed in the diffusion chamber. For this reason, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.

[0014] In addition, the orifice is formed in the downstream end plate of the diffusion chamber at the portion where the inner edge of the orifice is distant from the receiving surface of the diffusion chamber. In other words, the orifice is formed on the downstream end plate of the diffusion chamber at the portion where the predetermined clearance is maintained between the inner edge of the orifice and the receiving surface of the diffusion chamber in the flowing direction of the mainstream of the exhaust gas flowing toward the receiving surface. That is, at least a portion of the downstream end plate between the receiving surface of the diffusion chamber and the inner edge of the orifice serves as the retention surface. Therefore, the exhaust gas colliding with the receiving surface of the diffusion chamber is not allowed to further flow down directly into the catalytic converter. For this reason, the exhaust gas may be retained in the diffusion chamber to be mixed effectively.

[0015] Thus, according to the exemplary embodiment of the present invention, the purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst. In addition, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Features, aspects, and advantages of exemplary embodiments of the present invention will become better understood with reference to the following description and accompanying drawings, which should not limit the invention in any way. Fig. 1 is a perspective view showing a conventional exhaust gas purification device in which an air / fuel ratio sensor is arranged in a diffusion chamber; Fig. 2 is a perspective view showing the exhaust gas purification device according to the exemplary embodiment of the present invention in which the air / fuel ratio sensor is arranged between the diffusion chamber and the catalytic converter: Fig. 3 is a side view showing arrangements of an exhaust manifold, the orifice, the air / fuel ratio sensor, the catalytic converter, and the diffusion chamber in the exhaust gas purification device; Fig. 4 is a cross-sectional view showing a cross-section of the exhaust gas purification device according to one example of the present invention viewed from the direction indicated by the arrow C shown in Fig. 3; Fig. 5 is a cross-sectional view showing a cross-section of the exhaust gas purification device according to another example of the present invention viewed from the direction indicated by the arrow C shown in Fig. 3; and Fig. 6 is a cross-sectional view showing a cross-section of the exhaust gas purification device according to still another example of the present invention viewed from the direction indicated by the arrow C shown in Fig. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0017] Embodiments of the present invention will now be explained with reference to the accompanying drawings. Note that the embodiments shown below are merely examples of the present invention, and do not limit the present invention.

[0018] The exhaust gas purification device according to the exemplary embodiment of the present invention may be applied to e.g., a gasoline engine having a plurality of cylinders, a plurality of header pipes extending from the cylinders, and a catalytic converter arranged downstream of the header pipes. As illustrated in Figs. 2 and 3, the exhaust gas purification device 1 comprises an exhaust manifold 2, a catalytic converter 3, a diffusion chamber 4, an orifice 5, a retention surface 6, and an air / fuel ratio sensor 7.

[0019] The exhaust manifold 2 comprises a plurality of header pipes, a collector, and a collector pipe 2a. Although not illustrated in Figs. 2 and 3, structures of the header pipes are similar to those of the header pipes 101, 102, and 103 shown in Fig. 1. Each of the header pipes are individually joined to cylinders of an engine (not shown) so that exhaust gas emitted from the cylinders of the engine flows through the header pipes toward the collector. A structure of the collector is similar to that of the collector 104a shown in Fig. 1, and the header pipes of the exhaust manifold 2 converge into one pipe to form the collector. Also, structure of the collector pipe 2a is similar to that of the collector pipe 104b shown in Fig. 1, and the exhaust manifold 2 is connected to the diffusion chamber 4 through the collector pipe 2a.

[0020] A structure of the catalytic converter 3 is similar to that of the catalytic converter 106, and a conventional catalytic converter may be adopted as the catalytic converter 3. According to the exemplary embodiment of the present invention, the catalytic converter 3 is connected to the exhaust manifold 2 through the diffusion chamber 4 and the orifice 5.

[0021] The diffusion chamber 4 is arranged between the header pipes of the exhaust manifold 2 and the catalytic converter 3. Specifically, the diffusion chamber 4 is connected to a downstream end of the collector through the collector pipe 2a, and the catalytic converter 3 is connected to the orifice 5 formed in a downstream end plate as an orifice plate of the diffusion chamber 4. It is to be noted that the definitions of "upstream" and "downstream" in the descriptions are upstream and downstream in a flowing direction of the exhaust gas. For example, in the example shown in Fig. 3, the arrow A indicates the downstream in the flowing direction of the exhaust gas flowing into the diffusion chamber 4, and the arrow B indicates the downstream in the flowing direction of the exhaust gas flowing out of the diffusion chamber 4. As illustrated in Fig. 3, an inner circumferential surface of the diffusion chamber 4 serves as a receiving surface 4a.

[0022] A mainstream of the exhaust gas flowing into the diffusion chamber 4 via the header pipes of the exhaust manifold 2 collides with the receiving surface 4a. In the diffusion chamber 4, specifically, a portion of an inner circumferential wall opposed to the downstream end (i.e., an outlet) of the collector pipe 2a serves as the receiving surface 4a. Specifically, the receiving surface 4a is erected substantially in a vertical fashion, and the receiving surface 4a includes a receiving portion D shown in Fig. 4. Therefore, the mainstream of the exhaust gas flowing into the diffusion chamber 4 collides with the receiving portion D of the receiving surface 4a at a substantially right angle. Then, as indicated by the curved arrows in Figs. 2 and 3, the mainstream of the exhaust gas is diffused and agitated in the diffusion chamber 4.

[0023] As described, the orifice 5 is formed on the downstream end plate of the diffusion chamber 4. In other words, the orifice 5 is formed between an internal space of the diffusion chamber 4 and the catalytic converter 3. The exhaust gas colliding with the receiving surface 4a further flows downwardly into the catalytic converter 3 through the orifice 5. As illustrated in Figs. 3 and 4, a cross-sectional area of the orifice 5 is smaller than an inner area of the diffusion chamber 4 in which the exhaust gas is diffused and agitated. Specifically, as shown in Fig. 4, a cross-sectional area CS1 as a diameter of the orifice 5 through which the exhaust gas flows from the diffusion chamber 4 toward the catalytic converter 3 is smaller than a cross-sectional area CS2 as a diameter of the inner space of the diffusion chamber 4 in which the exhaust gas is diffused and agitated.

[0024] In addition, the orifice 5 is formed in the downstream end plate of the diffusion chamber 4 at a portion where an inner edge (i.e., an opening edge) 5a of the orifice 5 is distant from the receiving surface 4a of the diffusion chamber 4. For example, as illustrated in Fig. 4, the orifice 5 may be formed on the downstream end plate of the diffusion chamber 4 at a portion where a predetermined clearance d is maintained between the inner edge 5a of the orifice 5 and the receiving surface 4a of the diffusion chamber 4 in the flowing direction of the mainstream of the exhaust gas flowing from the collector pipe 2a toward the receiving surface 4a. In other words, the orifice 5 is eccentrically formed on the downstream end plate of the diffusion chamber 4 at a portion where the predetermined clearance d is maintained between the inner edge 5a of the orifice 5 and the receiving surface 4a of the diffusion chamber 4 in the horizontal direction of Fig. 4. Here, Fig. 4 and after-mentioned Figs. 5 and 6 show the cross-sections of the diffusion chamber 4 and the orifice 5 viewed from the direction indicated by the arrow C shown in Fig. 3. However, those cross-sections are not hatched in Figs. 4 to 6 for the sake of illustration.

[0025] An inner surface of the downstream end plate (i.e., a bottom plate) of the diffusion chamber 4 serves as the retention surface 6. As illustrated in Fig. 4, the retention surface 6 includes a portion between the receiving portion D of the receiving surface 4a of the diffusion chamber 4 and the inner edge 5a of the orifice 5. Therefore, the exhaust gas colliding with the receiving portion D of the receiving surface 4a is not allowed to further flow down directly into the catalytic converter 3. That is, since the orifice 5 is formed at the portion where the predetermined clearance d is maintained from the receiving portion D of the receiving surface 4a of the diffusion chamber 4, the retention surface 6 is ensured between the receiving portion D of the receiving surface 4a of the diffusion chamber 4 and the inner edge 5a of the orifice 5. Therefore, after the exhaust gas collides with the receiving portion D of the receiving surface 4a, a part of the exhaust gas flowing downwardly toward the catalytic converter 3 is blocked by the portion of the retention surface 6 between the receiving portion D of the receiving surface 4a and the inner edge 5a of the orifice 5, and most part of the exhaust gas is retained in the diffusion chamber 4. For this reason, the exhaust gas may be diffused and agitated efficiently in the diffusion chamber 4.

[0026] The air / fuel ratio sensor 7 is located downstream of the orifice 5 to measure an air / fuel ratio of an air / fuel mixture supplied to the engine from the exhaust gas. As described, in the conventional exhaust gas purification devices, flows of the exhaust gas emitted from the header pipes come into contact with the air / fuel ratio sensor through the collector at different angles. Therefore, a measured value of an air / fuel ratio may vary depending on a contact angle of the flow of the exhaust gas with the air / fuel ratio sensor. Whereas, in the exhaust gas purification device 1 according to the exemplary embodiment of the present invention, the air / fuel ratio sensor 7 is arranged downstream of the orifice 5. Theretofore, the air / fuel ratio may be measured from the exhaust gas after the flows of the exhaust gas emitted from the header pipes of the exhaust manifold 2 are mixed in the diffusion chamber 4. For this reason, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.

[0027] Turning to Fig. 5, there is shown another example of the exhaust gas purification device 1 according to the present invention. In the example shown in Fig. 5, the orifice 5 is formed in the downstream end plate of the diffusion chamber 4 at a portion where the clearance d between the receiving portion D of the receiving surface 4a of the diffusion chamber 4 and the inner edge 5a of the orifice 5 is increased to the maximum. That is, the portion of the retention surface 6 between the receiving portion D of the receiving surface 4a of the diffusion chamber 4 and the inner edge 5a of the orifice 5 is widened to the maximum. According to another example shown in Fig. 5, therefore, the exhaust gas flowing downwardly toward the catalytic converter 3 may be blocked more effectively by the above-mentioned portion of the retention surface 6 thus expanded. For this reason, the exhaust gas may be retained in the diffusion chamber 4 more effectively to be diffused and agitated.

[0028] Turning to Fig. 6, there is shown still another example of the exhaust gas purification device 1 according to the present invention. In the example shown in Fig. 6, the orifice 5 is formed into an oval shape. As described, the exhaust gas purification device 1 according to the present invention comprises the diffusion chamber 4 including the receiving surface 4a, and the orifice 5 including the inner edge 5a. In addition, in the exhaust gas purification device 1, the cross-sectional area CS1 of the orifice 5 is smaller than the cross-sectional area CS2 of the inner space of the diffusion chamber 4, and the retention surface 6 is ensured between the receiving portion D of the receiving surface 4a and the inner edge 5a of the orifice 5. Therefore, a shape and a location of the orifice 5 as well as dimensions of the diffusion chamber 4 may be altered as long as the cross-sectional area CS1 of the orifice 5 is smaller than the cross-sectional area CS2 of the inner space of the diffusion chamber 4 to ensure the retention surface 6 between the receiving portion D of the receiving surface 4a and the inner edge 5a of the orifice 5.

[0029] Thus, in the exhaust gas purification device 1 according to the exemplary embodiment of the present invention, the header pipes of the exhaust manifold 2 are connected to the cylinders of the engine, and the diffusion chamber 4 is arranged downstream of the exhaust manifold 2. According to the exemplary embodiment of the present invention, therefore, the flows of the exhaust gas emitted from the cylinders of the engine flow into the diffusion chamber 4 to be diffused and agitated. Consequently, a flow rate of the exhausted gas passing through the catalytic converter 3 is reduced. For this reason, the purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst.

[0030] In addition, in the exhaust gas purification device 1 according to the exemplary embodiment of the present invention, the orifice 5 is formed in the downstream end plate of the diffusion chamber 4. Further, the catalytic converter 3 is connected to the orifice 5, and the air / fuel ratio sensor 7 is arranged downstream of the orifice 5. According to the exemplary embodiment of the present invention, therefore, the air / fuel ratio of the air / fuel mixture may be measured from the exhaust gas after the flows of the exhaust gas emitted from the header pipes of the exhaust manifold 2 are mixed in the diffusion chamber 4. For this reason, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.

[0031] Thus, according to the exemplary embodiment of the present invention, the purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst. In addition, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.

Examples

Embodiment Construction

[0017]Embodiments of the present invention will now be explained with reference to the accompanying drawings. Note that the embodiments shown below are merely examples of the present invention, and do not limit the present invention.

[0018]The exhaust gas purification device according to the exemplary embodiment of the present invention may be applied to e.g., a gasoline engine having a plurality of cylinders, a plurality of header pipes extending from the cylinders, and a catalytic converter arranged downstream of the header pipes. As illustrated in Figs. 2 and 3, the exhaust gas purification device 1 comprises an exhaust manifold 2, a catalytic converter 3, a diffusion chamber 4, an orifice 5, a retention surface 6, and an air / fuel ratio sensor 7.

[0019]The exhaust manifold 2 comprises a plurality of header pipes, a collector, and a collector pipe 2a. Although not illustrated in Figs. 2 and 3, structures of the header pipes are similar to those of the header pipes 101, 102, and 103 ...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present invention claims the benefit of Japanese Patent Application No. 2024-087800 filed on May 30, 2024 with the Japanese Patent Office, the invention of which is incorporated herein by reference in its entirety.BACKGROUND Field of the Invention

[0002] Embodiments of the present invention relate to the art of an exhaust gas purifying device for an internal combustion engine, and especially to an exhaust gas purifying device in which a catalytic converter in arranged in the vicinity of an engine having an exhaust pipe connected to a plurality of cylinders.Discussion of the Related Art

[0003] In the internal combustion engines, a catalytic converter may have to be offset significantly from a center in an array direction of cylinders. JP-A-2014-211111 discloses an exhaust pipe structure adapted to introduce exhaust gas into a catalytic converter in a well-balanced manner.

[0004] In the exhaust pipe structure described in JP-A-2014-211111, exhaust passages are connected individually to cylinders, and exhaust gas flowing through the exhaust passage is guided to the catalytic converter through a swirl structure of a collection part formed between the first exhaust passage and the second exhaust passage.

[0005] In the exhaust pipe structure described in JP-A-2014-211111, although the catalyst converter is significantly offset from the center of the row of the cylinders, the exhaust gas may be introduced to the catalytic converter in a well-balanced manner. However, since a swirl flow of the exhaust gas tends to flow outer side in the passage, the exhaust gas may not be not allowed to flow efficiently through a center portion of the catalyst. In addition, since the collection part at which the flows of the exhaust gas converge is formed between the first exhaust passage and the second exhaust passage, flow rates of the flows of the exhaust gas flowing through the first exhaust passage and the second exhaust passage are increased. That is, a time period in which the exhaust gas flows within the catalyst is shortened. Therefore, in order to ensure a purifying performance of the catalyst, it is necessary to enlarge the catalyst. However, if the catalyst is enlarged, a loss of pressure in the exhaust gas purifying device may be increased.

[0006] JP-A-2024-79990 discloses an exhaust gas control apparatus for enhancing a purifying performance of a catalyst without enlarging the catalyst. The exhaust gas control apparatus taught by JP-A-2024-79990 is applied to an internal combustion engine having a plurality of cylinders, a plurality of exhaust passages communicating with the plurality of cylinders, and a catalytic converter. In the engine to which the exhaust gas control apparatus taught by JP-A-2024-79990 is applied, a diffusion portion that promotes a jet flow of the exhaust gas flowing into a merging portion is provided at the merging portion connected to a downstream side of the exhaust passage. The diffusion portion includes a dispersion face that is substantially perpendicular to a flowing direction of the exhaust gas so that the main flow of the exhaust gas that has flowed linearly into the merging portion collides with the dispersion face to be dispersed. According to the teachings of JP-A-2024-79990, therefore, the flow rate of the exhaust gas passing through the catalyst can be reduced, whereby the purification characteristics can be improved without increasing the size of the catalyst. In addition, in the exhaust gas control apparatus taught by JP-A-2024-79990, an air / fuel ratio sensor is provided at a portion where the main flow of the exhaust gas flowing into the merging portion from the exhaust passages is alternating with each other. According to the teachings of JP-A-2024-79990, therefore, the flow rate of the exhaust gas discharged from the respective cylinders is fast and collides with the air / fuel ratio sensor so that the sensor responsiveness can be secured.

[0007] However, if the air / fuel ratio sensor is arranged at the diffusion portion where the flows of exhaust gas converge, an air / fuel ratio may not be measured accurately. Fig. 1 shows an example of an exhaust gas purification device to which the teachings of JP-A-2024-79990 is applied. The purification device 100 shown in Fig. 1 comprises: an exhaust manifold 104 including paired header pipes 101, 102, and 103 individually connected to cylinders of an engine (not shown); a collector 104a at which the paired header pipes 101, 102, and 103 converge; a collector pipe 104b joined to a downstream side of the collector 104a; a diffusion chamber 105 in which a jet flow of the exhaust gas is created and which is joined to the collector pipe 104b; a catalytic converter 106 joined to a downstream side of the diffusion chamber 105; and an air / fuel ratio sensor 107 arranged in the vicinity of an inlet 105a of the diffusion chamber 105 from which the exhaust gas flows into the diffusion chamber 105. In the purification device 100, the exhaust gas emitted from an engine flow into the collector pipe 104b from different directions. Therefore, flowing directions of the exhaust gas passing through the air / fuel ratio sensor 107 vary as indicated by the arrows a, b, and c. That is, the flows of the exhaust gas come into contact with the air / fuel ratio sensor 107 unevenly. In addition, since the air / fuel ratio sensor 107 is arranged in the diffusion chamber 105, an air-fuel ratio may be measured before the flows of the exhaust gas are mixed completely. Therefore, the air / fuel ratio measured by the air / fuel ratio sensor 107 may be varied, and the engine may not be controlled properly based on the air / fuel ratio measured by the air / fuel ratio sensor 107.SUMMARY

[0008] Aspects of embodiments of the present invention have been conceived noting the foregoing technical problems, and it is therefore an object of the present invention to provide an exhaust gas purification device for an internal combustion engine configured to enhance a purification performance and to measure an exhaust air / fuel ratio accurately.

[0009] In order to achieve the above-explained objective, according to the exemplary embodiment of the present invention, there is provided an exhaust gas purification device for an internal combustion engine, comprising: at least one or more header pipe through which an exhaust gas emitted from cylinders of the engine flows; a catalytic converter arranged downstream of the header pipe; a diffusion chamber arranged between the header pipe and the catalytic converter; a receiving surface formed in the diffusion chamber with which a mainstream of the exhaust gas flowing into the diffusion chamber via the header pipe collides; an orifice formed in a downstream end plate of the diffusion chamber, a cross-sectional area thereof is smaller than a cross-sectional area of an internal space of the diffusion chamber; and an air / fuel ratio sensor arranged downstream of the orifice to measure an air / fuel ratio of an air / fuel mixture supplied to the engine.

[0010] In a non-limiting embodiment, the orifice may be formed in the downstream end plate of the diffusion chamber at a portion where an inner edge of the orifice is distant from the receiving surface of the diffusion chamber.

[0011] In a non-limiting embodiment, the orifice may be formed on the downstream end plate of the diffusion chamber at a portion where a predetermined clearance is maintained between an inner edge of the orifice and the receiving surface of the diffusion chamber in a flowing direction of the mainstream of the exhaust gas flowing toward the receiving surface.

[0012] In a non-limiting embodiment, the exhaust gas purification device may further comprise a retention surface formed on at least a portion of the downstream end plate between the receiving surface of the diffusion chamber and the inner edge of the orifice so as to prevent the exhaust gas colliding with the receiving surface from flowing into the catalytic converter.

[0013] In the exhaust gas purification device according to the exemplary embodiment of the present invention, flows of the exhaust gas emitted from cylinders of the engine flow into the diffusion chamber to be diffused and agitated. According to the exemplary embodiment of the present invention, therefore, a flow rate of the exhausted gas passing through the catalytic converter may be reduced. For this reason, a purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst. In addition, in the exhaust gas purification device according to the exemplary embodiment of the present invention, the orifice is formed in the downstream end plate of the diffusion chamber. Further, the catalytic converter is connected to the orifice, and the air / fuel ratio sensor is arranged downstream of the orifice. According to the exemplary embodiment of the present invention, therefore, the air / fuel ratio of the air / fuel mixture may be measured from the exhaust gas after the flows of the exhaust gas emitted from the header pipes are mixed in the diffusion chamber. For this reason, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.

[0014] In addition, the orifice is formed in the downstream end plate of the diffusion chamber at the portion where the inner edge of the orifice is distant from the receiving surface of the diffusion chamber. In other words, the orifice is formed on the downstream end plate of the diffusion chamber at the portion where the predetermined clearance is maintained between the inner edge of the orifice and the receiving surface of the diffusion chamber in the flowing direction of the mainstream of the exhaust gas flowing toward the receiving surface. That is, at least a portion of the downstream end plate between the receiving surface of the diffusion chamber and the inner edge of the orifice serves as the retention surface. Therefore, the exhaust gas colliding with the receiving surface of the diffusion chamber is not allowed to further flow down directly into the catalytic converter. For this reason, the exhaust gas may be retained in the diffusion chamber to be mixed effectively.

[0015] Thus, according to the exemplary embodiment of the present invention, the purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst. In addition, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Features, aspects, and advantages of exemplary embodiments of the present invention will become better understood with reference to the following description and accompanying drawings, which should not limit the invention in any way. Fig. 1 is a perspective view showing a conventional exhaust gas purification device in which an air / fuel ratio sensor is arranged in a diffusion chamber; Fig. 2 is a perspective view showing the exhaust gas purification device according to the exemplary embodiment of the present invention in which the air / fuel ratio sensor is arranged between the diffusion chamber and the catalytic converter: Fig. 3 is a side view showing arrangements of an exhaust manifold, the orifice, the air / fuel ratio sensor, the catalytic converter, and the diffusion chamber in the exhaust gas purification device; Fig. 4 is a cross-sectional view showing a cross-section of the exhaust gas purification device according to one example of the present invention viewed from the direction indicated by the arrow C shown in Fig. 3; Fig. 5 is a cross-sectional view showing a cross-section of the exhaust gas purification device according to another example of the present invention viewed from the direction indicated by the arrow C shown in Fig. 3; and Fig. 6 is a cross-sectional view showing a cross-section of the exhaust gas purification device according to still another example of the present invention viewed from the direction indicated by the arrow C shown in Fig. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0017] Embodiments of the present invention will now be explained with reference to the accompanying drawings. Note that the embodiments shown below are merely examples of the present invention, and do not limit the present invention.

[0018] The exhaust gas purification device according to the exemplary embodiment of the present invention may be applied to e.g., a gasoline engine having a plurality of cylinders, a plurality of header pipes extending from the cylinders, and a catalytic converter arranged downstream of the header pipes. As illustrated in Figs. 2 and 3, the exhaust gas purification device 1 comprises an exhaust manifold 2, a catalytic converter 3, a diffusion chamber 4, an orifice 5, a retention surface 6, and an air / fuel ratio sensor 7.

[0019] The exhaust manifold 2 comprises a plurality of header pipes, a collector, and a collector pipe 2a. Although not illustrated in Figs. 2 and 3, structures of the header pipes are similar to those of the header pipes 101, 102, and 103 shown in Fig. 1. Each of the header pipes are individually joined to cylinders of an engine (not shown) so that exhaust gas emitted from the cylinders of the engine flows through the header pipes toward the collector. A structure of the collector is similar to that of the collector 104a shown in Fig. 1, and the header pipes of the exhaust manifold 2 converge into one pipe to form the collector. Also, structure of the collector pipe 2a is similar to that of the collector pipe 104b shown in Fig. 1, and the exhaust manifold 2 is connected to the diffusion chamber 4 through the collector pipe 2a.

[0020] A structure of the catalytic converter 3 is similar to that of the catalytic converter 106, and a conventional catalytic converter may be adopted as the catalytic converter 3. According to the exemplary embodiment of the present invention, the catalytic converter 3 is connected to the exhaust manifold 2 through the diffusion chamber 4 and the orifice 5.

[0021] The diffusion chamber 4 is arranged between the header pipes of the exhaust manifold 2 and the catalytic converter 3. Specifically, the diffusion chamber 4 is connected to a downstream end of the collector through the collector pipe 2a, and the catalytic converter 3 is connected to the orifice 5 formed in a downstream end plate as an orifice plate of the diffusion chamber 4. It is to be noted that the definitions of "upstream" and "downstream" in the descriptions are upstream and downstream in a flowing direction of the exhaust gas. For example, in the example shown in Fig. 3, the arrow A indicates the downstream in the flowing direction of the exhaust gas flowing into the diffusion chamber 4, and the arrow B indicates the downstream in the flowing direction of the exhaust gas flowing out of the diffusion chamber 4. As illustrated in Fig. 3, an inner circumferential surface of the diffusion chamber 4 serves as a receiving surface 4a.

[0022] A mainstream of the exhaust gas flowing into the diffusion chamber 4 via the header pipes of the exhaust manifold 2 collides with the receiving surface 4a. In the diffusion chamber 4, specifically, a portion of an inner circumferential wall opposed to the downstream end (i.e., an outlet) of the collector pipe 2a serves as the receiving surface 4a. Specifically, the receiving surface 4a is erected substantially in a vertical fashion, and the receiving surface 4a includes a receiving portion D shown in Fig. 4. Therefore, the mainstream of the exhaust gas flowing into the diffusion chamber 4 collides with the receiving portion D of the receiving surface 4a at a substantially right angle. Then, as indicated by the curved arrows in Figs. 2 and 3, the mainstream of the exhaust gas is diffused and agitated in the diffusion chamber 4.

[0023] As described, the orifice 5 is formed on the downstream end plate of the diffusion chamber 4. In other words, the orifice 5 is formed between an internal space of the diffusion chamber 4 and the catalytic converter 3. The exhaust gas colliding with the receiving surface 4a further flows downwardly into the catalytic converter 3 through the orifice 5. As illustrated in Figs. 3 and 4, a cross-sectional area of the orifice 5 is smaller than an inner area of the diffusion chamber 4 in which the exhaust gas is diffused and agitated. Specifically, as shown in Fig. 4, a cross-sectional area CS1 as a diameter of the orifice 5 through which the exhaust gas flows from the diffusion chamber 4 toward the catalytic converter 3 is smaller than a cross-sectional area CS2 as a diameter of the inner space of the diffusion chamber 4 in which the exhaust gas is diffused and agitated.

[0024] In addition, the orifice 5 is formed in the downstream end plate of the diffusion chamber 4 at a portion where an inner edge (i.e., an opening edge) 5a of the orifice 5 is distant from the receiving surface 4a of the diffusion chamber 4. For example, as illustrated in Fig. 4, the orifice 5 may be formed on the downstream end plate of the diffusion chamber 4 at a portion where a predetermined clearance d is maintained between the inner edge 5a of the orifice 5 and the receiving surface 4a of the diffusion chamber 4 in the flowing direction of the mainstream of the exhaust gas flowing from the collector pipe 2a toward the receiving surface 4a. In other words, the orifice 5 is eccentrically formed on the downstream end plate of the diffusion chamber 4 at a portion where the predetermined clearance d is maintained between the inner edge 5a of the orifice 5 and the receiving surface 4a of the diffusion chamber 4 in the horizontal direction of Fig. 4. Here, Fig. 4 and after-mentioned Figs. 5 and 6 show the cross-sections of the diffusion chamber 4 and the orifice 5 viewed from the direction indicated by the arrow C shown in Fig. 3. However, those cross-sections are not hatched in Figs. 4 to 6 for the sake of illustration.

[0025] An inner surface of the downstream end plate (i.e., a bottom plate) of the diffusion chamber 4 serves as the retention surface 6. As illustrated in Fig. 4, the retention surface 6 includes a portion between the receiving portion D of the receiving surface 4a of the diffusion chamber 4 and the inner edge 5a of the orifice 5. Therefore, the exhaust gas colliding with the receiving portion D of the receiving surface 4a is not allowed to further flow down directly into the catalytic converter 3. That is, since the orifice 5 is formed at the portion where the predetermined clearance d is maintained from the receiving portion D of the receiving surface 4a of the diffusion chamber 4, the retention surface 6 is ensured between the receiving portion D of the receiving surface 4a of the diffusion chamber 4 and the inner edge 5a of the orifice 5. Therefore, after the exhaust gas collides with the receiving portion D of the receiving surface 4a, a part of the exhaust gas flowing downwardly toward the catalytic converter 3 is blocked by the portion of the retention surface 6 between the receiving portion D of the receiving surface 4a and the inner edge 5a of the orifice 5, and most part of the exhaust gas is retained in the diffusion chamber 4. For this reason, the exhaust gas may be diffused and agitated efficiently in the diffusion chamber 4.

[0026] The air / fuel ratio sensor 7 is located downstream of the orifice 5 to measure an air / fuel ratio of an air / fuel mixture supplied to the engine from the exhaust gas. As described, in the conventional exhaust gas purification devices, flows of the exhaust gas emitted from the header pipes come into contact with the air / fuel ratio sensor through the collector at different angles. Therefore, a measured value of an air / fuel ratio may vary depending on a contact angle of the flow of the exhaust gas with the air / fuel ratio sensor. Whereas, in the exhaust gas purification device 1 according to the exemplary embodiment of the present invention, the air / fuel ratio sensor 7 is arranged downstream of the orifice 5. Theretofore, the air / fuel ratio may be measured from the exhaust gas after the flows of the exhaust gas emitted from the header pipes of the exhaust manifold 2 are mixed in the diffusion chamber 4. For this reason, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.

[0027] Turning to Fig. 5, there is shown another example of the exhaust gas purification device 1 according to the present invention. In the example shown in Fig. 5, the orifice 5 is formed in the downstream end plate of the diffusion chamber 4 at a portion where the clearance d between the receiving portion D of the receiving surface 4a of the diffusion chamber 4 and the inner edge 5a of the orifice 5 is increased to the maximum. That is, the portion of the retention surface 6 between the receiving portion D of the receiving surface 4a of the diffusion chamber 4 and the inner edge 5a of the orifice 5 is widened to the maximum. According to another example shown in Fig. 5, therefore, the exhaust gas flowing downwardly toward the catalytic converter 3 may be blocked more effectively by the above-mentioned portion of the retention surface 6 thus expanded. For this reason, the exhaust gas may be retained in the diffusion chamber 4 more effectively to be diffused and agitated.

[0028] Turning to Fig. 6, there is shown still another example of the exhaust gas purification device 1 according to the present invention. In the example shown in Fig. 6, the orifice 5 is formed into an oval shape. As described, the exhaust gas purification device 1 according to the present invention comprises the diffusion chamber 4 including the receiving surface 4a, and the orifice 5 including the inner edge 5a. In addition, in the exhaust gas purification device 1, the cross-sectional area CS1 of the orifice 5 is smaller than the cross-sectional area CS2 of the inner space of the diffusion chamber 4, and the retention surface 6 is ensured between the receiving portion D of the receiving surface 4a and the inner edge 5a of the orifice 5. Therefore, a shape and a location of the orifice 5 as well as dimensions of the diffusion chamber 4 may be altered as long as the cross-sectional area CS1 of the orifice 5 is smaller than the cross-sectional area CS2 of the inner space of the diffusion chamber 4 to ensure the retention surface 6 between the receiving portion D of the receiving surface 4a and the inner edge 5a of the orifice 5.

[0029] Thus, in the exhaust gas purification device 1 according to the exemplary embodiment of the present invention, the header pipes of the exhaust manifold 2 are connected to the cylinders of the engine, and the diffusion chamber 4 is arranged downstream of the exhaust manifold 2. According to the exemplary embodiment of the present invention, therefore, the flows of the exhaust gas emitted from the cylinders of the engine flow into the diffusion chamber 4 to be diffused and agitated. Consequently, a flow rate of the exhausted gas passing through the catalytic converter 3 is reduced. For this reason, the purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst.

[0030] In addition, in the exhaust gas purification device 1 according to the exemplary embodiment of the present invention, the orifice 5 is formed in the downstream end plate of the diffusion chamber 4. Further, the catalytic converter 3 is connected to the orifice 5, and the air / fuel ratio sensor 7 is arranged downstream of the orifice 5. According to the exemplary embodiment of the present invention, therefore, the air / fuel ratio of the air / fuel mixture may be measured from the exhaust gas after the flows of the exhaust gas emitted from the header pipes of the exhaust manifold 2 are mixed in the diffusion chamber 4. For this reason, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.

[0031] Thus, according to the exemplary embodiment of the present invention, the purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst. In addition, the air / fuel ratio of the air / fuel mixture may be measured accurately without variations.

Examples

Embodiment Construction

[0017]Embodiments of the present invention will now be explained with reference to the accompanying drawings. Note that the embodiments shown below are merely examples of the present invention, and do not limit the present invention.

[0018]The exhaust gas purification device according to the exemplary embodiment of the present invention may be applied to e.g., a gasoline engine having a plurality of cylinders, a plurality of header pipes extending from the cylinders, and a catalytic converter arranged downstream of the header pipes. As illustrated in Figs. 2 and 3, the exhaust gas purification device 1 comprises an exhaust manifold 2, a catalytic converter 3, a diffusion chamber 4, an orifice 5, a retention surface 6, and an air / fuel ratio sensor 7.

[0019]The exhaust manifold 2 comprises a plurality of header pipes, a collector, and a collector pipe 2a. Although not illustrated in Figs. 2 and 3, structures of the header pipes are similar to those of the header pipes 101, 102, and 103 ...

Claims

1. An exhaust gas purification device (1) for an internal combustion engine, comprising: at least one or more header pipe through which an exhaust gas emitted from cylinders of the engine flows; a catalytic converter (3) arranged downstream of the header pipe; a diffusion chamber (4) arranged between the header pipe and the catalytic converter (3); a receiving surface (4a) formed in the diffusion chamber (4) with which a mainstream of the exhaust gas flowing into the diffusion chamber (4) via the header pipe collides; characterized by: an orifice (5) formed in a downstream end plate of the diffusion chamber (4), a cross-sectional area thereof is smaller than a cross-sectional area of an internal space of the diffusion chamber (4); and an air / fuel ratio sensor (7) arranged downstream of the orifice to measure an air / fuel ratio of an air / fuel mixture supplied to the engine.

2. The exhaust gas purification device (1) as claimed in claim 1, wherein the orifice (5) is formed in the downstream end plate of the diffusion chamber (4) at a portion where an inner edge of the orifice (5) is distant from the receiving surface (4a) of the diffusion chamber (4).

3. The exhaust gas purification device (1) as claimed in claim 1 or 2, wherein the orifice (5) is formed on the downstream end plate of the diffusion chamber (4) at a portion where a predetermined clearance (d) is maintained between an inner edge of the orifice (5) and the receiving surface (4a) of the diffusion chamber (4) in a flowing direction of the mainstream of the exhaust gas flowing toward the receiving surface (4a).

4. The exhaust gas purification device (1) as claimed in claim 3, further comprising: a retention surface (6) formed on at least a portion of the downstream end plate between the receiving surface (4a) of the diffusion chamber (4) and the inner edge of the orifice (5) so as to prevent the exhaust gas colliding with the receiving surface (4a) from flowing into the catalytic converter.

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