Exhaust Gas Purification Device for Internal Combustion Engine

The present disclosure claims the benefit of Japanese Patent Application No. 2024-087800 filed on May 30, 2024 with the Japanese Patent Office, the disclosure of which is incorporated herein by reference in its entirety.

Embodiments of the present disclosure 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.

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.

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.

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.

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.

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.shows an example of an exhaust gas purification device to which the teachings of JP-A-2024-79990 is applied. The purification deviceshown incomprises: an exhaust manifoldincluding paired header pipes,, andindividually connected to cylinders of an engine (not shown); a collectorat which the paired header pipes,, andconverge; a collector pipejoined to a downstream side of the collector; a diffusion chamberin which a jet flow of the exhaust gas is created and which is joined to the collector pipe; a catalytic converterjoined to a downstream side of the diffusion chamber; and an air/fuel ratio sensorarranged in the vicinity of an inletof the diffusion chamberfrom which the exhaust gas flows into the diffusion chamber. In the purification device, the exhaust gas emitted from an engine flow into the collector pipefrom different directions. Therefore, flowing directions of the exhaust gas passing through the air/fuel ratio sensorvary 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 sensorunevenly. In addition, since the air/fuel ratio sensoris arranged in the diffusion chamber, 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 sensormay be varied, and the engine may not be controlled properly based on the air/fuel ratio measured by the air/fuel ratio sensor.

Aspects of embodiments of the present disclosure have been conceived noting the foregoing technical problems, and it is therefore an object of the present disclosure 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.

In order to achieve the above-explained objective, according to the exemplary embodiment of the present disclosure, 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.

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.

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.

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.

In the exhaust gas purification device according to the exemplary embodiment of the present disclosure, 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 disclosure, 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 disclosure, 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 disclosure, 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.

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.

Thus, according to the exemplary embodiment of the present disclosure, 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.

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

The exhaust gas purification device according to the exemplary embodiment of the present disclosure 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, the exhaust gas purification devicecomprises an exhaust manifold, a catalytic converter, a diffusion chamber, an orifice, a retention surface, and an air/fuel ratio sensor.

The exhaust manifoldcomprises a plurality of header pipes, a collector, and a collector pipe. Although not illustrated in, structures of the header pipes are similar to those of the header pipes,, andshown in. 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 collectorshown in, and the header pipes of the exhaust manifoldconverge into one pipe to form the collector. Also, structure of the collector pipeis similar to that of the collector pipeshown in, and the exhaust manifoldis connected to the diffusion chamberthrough the collector pipe

A structure of the catalytic converteris similar to that of the catalytic converter, and a conventional catalytic converter may be adopted as the catalytic converter. According to the exemplary embodiment of the present disclosure, the catalytic converteris connected to the exhaust manifoldthrough the diffusion chamberand the orifice.

The diffusion chamberis arranged between the header pipes of the exhaust manifoldand the catalytic converter. Specifically, the diffusion chamberis connected to a downstream end of the collector through the collector pipe, and the catalytic converteris connected to the orificeformed in a downstream end plate as an orifice plate of the diffusion chamber. 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, the arrow A indicates the downstream in the flowing direction of the exhaust gas flowing into the diffusion chamber, and the arrow B indicates the downstream in the flowing direction of the exhaust gas flowing out of the diffusion chamber. As illustrated in, an inner circumferential surface of the diffusion chamberserves as a receiving surface

A mainstream of the exhaust gas flowing into the diffusion chambervia the header pipes of the exhaust manifoldcollides with the receiving surface. In the diffusion chamber, specifically, a portion of an inner circumferential wall opposed to the downstream end (i.e., an outlet) of the collector pipeserves as the receiving surface. Specifically, the receiving surfaceis erected substantially in a vertical fashion, and the receiving surfaceincludes a receiving portion D shown in. Therefore, the mainstream of the exhaust gas flowing into the diffusion chambercollides with the receiving portion D of the receiving surfaceat a substantially right angle. Then, as indicated by the curved arrows in, the mainstream of the exhaust gas is diffused and agitated in the diffusion chamber.

As described, the orificeis formed on the downstream end plate of the diffusion chamber. In other words, the orificeis formed between an internal space of the diffusion chamberand the catalytic converter. The exhaust gas colliding with the receiving surfacefurther flows downwardly into the catalytic converterthrough the orifice. As illustrated in, a cross-sectional area of the orificeis smaller than an inner area of the diffusion chamberin which the exhaust gas is diffused and agitated. Specifically, as shown in, a cross-sectional area CS1 as a diameter of the orificethrough which the exhaust gas flows from the diffusion chambertoward the catalytic converteris smaller than a cross-sectional area CS2 as a diameter of the inner space of the diffusion chamberin which the exhaust gas is diffused and agitated.

In addition, the orificeis formed in the downstream end plate of the diffusion chamberat a portion where an inner edge (i.e., an opening edge)of the orificeis distant from the receiving surfaceof the diffusion chamber. For example, as illustrated in, the orificemay be formed on the downstream end plate of the diffusion chamberat a portion where a predetermined clearance d is maintained between the inner edgeof the orificeand the receiving surfaceof the diffusion chamberin the flowing direction of the mainstream of the exhaust gas flowing from the collector pipetoward the receiving surface. In other words, the orificeis eccentrically formed on the downstream end plate of the diffusion chamberat a portion where the predetermined clearance d is maintained between the inner edgeof the orificeand the receiving surfaceof the diffusion chamberin the horizontal direction of. Here,and after-mentionedshow the cross-sections of the diffusion chamberand the orificeviewed from the direction indicated by the arrow C shown in. However, those cross-sections are not hatched infor the sake of illustration.

An inner surface of the downstream end plate (i.e., a bottom plate) of the diffusion chamberserves as the retention surface. As illustrated in, the retention surfaceincludes a portion between the receiving portion D of the receiving surfaceof the diffusion chamberand the inner edgeof the orifice. Therefore, the exhaust gas colliding with the receiving portion D of the receiving surfaceis not allowed to further flow down directly into the catalytic converter. That is, since the orificeis formed at the portion where the predetermined clearance d is maintained from the receiving portion D of the receiving surfaceof the diffusion chamber, the retention surfaceis ensured between the receiving portion D of the receiving surfaceof the diffusion chamberand the inner edgeof the orifice. Therefore, after the exhaust gas collides with the receiving portion D of the receiving surface, a part of the exhaust gas flowing downwardly toward the catalytic converteris blocked by the portion of the retention surfacebetween the receiving portion D of the receiving surfaceand the inner edgeof the orifice, and most part of the exhaust gas is retained in the diffusion chamber. For this reason, the exhaust gas may be diffused and agitated efficiently in the diffusion chamber.

The air/fuel ratio sensoris located downstream of the orificeto 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 deviceaccording to the exemplary embodiment of the present disclosure, the air/fuel ratio sensoris arranged downstream of the orifice. 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 manifoldare mixed in the diffusion chamber. For this reason, the air/fuel ratio of the air/fuel mixture may be measured accurately without variations.

Turning to, there is shown another example of the exhaust gas purification deviceaccording to the present disclosure. In the example shown in, the orificeis formed in the downstream end plate of the diffusion chamberat a portion where the clearance d between the receiving portion D of the receiving surfaceof the diffusion chamberand the inner edgeof the orificeis increased to the maximum. That is, the portion of the retention surfacebetween the receiving portion D of the receiving surfaceof the diffusion chamberand the inner edgeof the orificeis widened to the maximum. According to another example shown in, therefore, the exhaust gas flowing downwardly toward the catalytic convertermay be blocked more effectively by the above-mentioned portion of the retention surfacethus expanded. For this reason, the exhaust gas may be retained in the diffusion chambermore effectively to be diffused and agitated.

Turning to, there is shown still another example of the exhaust gas purification deviceaccording to the present disclosure. In the example shown in, the orificeis formed into an oval shape. As described, the exhaust gas purification deviceaccording to the present disclosure comprises the diffusion chamberincluding the receiving surface, and the orificeincluding the inner edge. In addition, in the exhaust gas purification device, the cross-sectional area CS1 of the orificeis smaller than the cross-sectional area CS2 of the inner space of the diffusion chamber, and the retention surfaceis ensured between the receiving portion D of the receiving surfaceand the inner edgeof the orifice. Therefore, a shape and a location of the orificeas well as dimensions of the diffusion chambermay be altered as long as the cross-sectional area CS1 of the orificeis smaller than the cross-sectional area CS2 of the inner space of the diffusion chamberto ensure the retention surfacebetween the receiving portion D of the receiving surfaceand the inner edgeof the orifice.

Thus, in the exhaust gas purification deviceaccording to the exemplary embodiment of the present disclosure, the header pipes of the exhaust manifoldare connected to the cylinders of the engine, and the diffusion chamberis arranged downstream of the exhaust manifold. According to the exemplary embodiment of the present disclosure, therefore, the flows of the exhaust gas emitted from the cylinders of the engine flow into the diffusion chamberto be diffused and agitated. Consequently, a flow rate of the exhausted gas passing through the catalytic converteris reduced. For this reason, the purification performance of the catalytic converter may be enhanced without increasing a size of the catalyst.

In addition, in the exhaust gas purification deviceaccording to the exemplary embodiment of the present disclosure, the orificeis formed in the downstream end plate of the diffusion chamber. Further, the catalytic converteris connected to the orifice, and the air/fuel ratio sensoris arranged downstream of the orifice. According to the exemplary embodiment of the present disclosure, 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 manifoldare mixed in the diffusion chamber. For this reason, the air/fuel ratio of the air/fuel mixture may be measured accurately without variations.

Thus, according to the exemplary embodiment of the present disclosure, 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.