Exhaust gas purification device for internal combustion engine

Abstract

To provide an exhaust emission control device of an internal combustion engine which achieves improvement of purification characteristics without increasing the size of a catalyst.SOLUTION: In an exhaust emission control device of an internal combustion engine, a catalytic converter 40 is attached to an engine including a plurality of cylinders 10a to 10d and a plurality of exhaust passages 20a to 20d communicating with the plurality of the cylinders 10a to 10d. In a confluent part 30 connected to the downstream side of the exhaust passages 20a to 20d, a diffusion part 32 which facilitates jet flow of a main stream of exhaust gas flowing into the confluent part 30 is provided. Further, on an inner wall of the confluent part 30 facing inflow ports 31 of the exhaust gas provided at the exhaust passages 20a to 20d, a diffusion surface 33 which three-dimensionally diffuses the main stream of the exhaust gas linearly flowing from the inflow ports 31 into the confluent part 30 is formed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device for an internal combustion engine in which a catalytic converter is attached in the immediate vicinity of an engine having an exhaust passage communicating with a plurality of cylinders.

Background Art

[0002] In this type of exhaust gas purification device for an internal combustion engine, there are cases where a catalytic converter arranged in the immediate vicinity of the engine has to be arranged with a large offset from the central portion in the cylinder row direction. Even when the catalytic converter arranged in the immediate vicinity of the engine is largely offset in this way, Patent Document 1 discloses a technique for introducing exhaust gas into the catalytic converter in a well-balanced manner.

[0003] Patent Document 1 discloses a technique in which exhaust gas flows flowing through a plurality of first exhaust passages, second exhaust passages, third exhaust passages, and fourth exhaust passages arranged side by side along a cylinder arrangement are each swirled and induced toward a catalytic converter by a swirling structure provided in a collecting portion arranged between the first exhaust passage and the second exhaust passage.

[0004] According to Patent Document 1, even when the catalytic converter is arranged with a large offset, exhaust gas can be introduced into the catalytic converter in a well-balanced manner.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in Patent Document 1, since the flow is biased to the outside of the pipe due to the generation of a swirling flow, there is a concern that the central part of the catalyst cannot be effectively utilized. Further, in Patent Document 1, since the collecting part is arranged between the first exhaust passage and the second exhaust passage, the flow velocity of the exhaust gas flowing through the first exhaust passage and the second exhaust passage is high, and the time the exhaust gas stays in the catalyst becomes short. Therefore, it is necessary to increase the size of the catalyst to ensure the purification ability, but there is a concern that the pressure loss increases in the entire exhaust purification system.

[0007] This invention has been made in view of the above circumstances, and an object thereof is to provide an exhaust purification device for an internal combustion engine capable of improving purification characteristics without increasing the size of the catalyst.

Means for Solving the Problems

[0008] In order to solve the above problems, a first invention is an exhaust purification device for an internal combustion engine in which a catalytic converter is attached to an engine including a plurality of cylinders and one or a plurality of exhaust passages communicating with the plurality of cylinders, wherein a diffusion part for promoting the jet flow of the main stream of the exhaust gas flowing into the confluence part is provided at the confluence part connected to the downstream side of the exhaust passage. One or more at the confluence part connected to the downstream side of the exhaust passage wherein , a protruding portion is formed such that a downstream end portion of the one or more exhaust passages protrudes into the confluence portion, and a diffusion part for promoting the jet flow of the main stream of the exhaust gas flowing into the confluence part is provided a dispersion surface is formed on an inner wall of the confluence portion facing an inlet of exhaust gas provided in the one or more exhaust passages, the dispersion surface colliding with a main stream of exhaust gas flowing linearly into the confluence portion from the inlet and three-dimensionally dispersing the exhaust gas. Further, the one or more exhaust passages are connected to the confluence portion via a bent portion, and an axis along an outer wall of the bent portion and the dispersion surface of the confluence portion are substantially orthogonal to each other and it is characterized by that.

[0009] By configuring in this way, in a confluence portion where exhaust passages from each cylinder merge, the jet flow of the main stream of exhaust gas flowing into the confluence portion peels off the flow of exhaust gas accumulating on the wall side of the exhaust passage from the wall and entrains the surrounding stationary gas, thereby diffusing the flow. At the same time, in a confluence portion where exhaust passages from each cylinder merge, the main stream of exhaust gas flowing into the confluence portion collides with the inner wall of the confluence portion facing the inlet and can disperse the flow three-dimensionally with respect to the collision portion. As a result, the flow velocity of the exhaust gas decreases, and the flow in the catalyst direction can be reduced.

[0021] In addition, in this invention, it is preferable that an exhaust gas sensor is provided at a portion where the main streams of the exhaust gas flowing into the confluence part from the plurality of exhaust passages in the confluence part intersect.

[0022] By configuring in this way, since the exhaust gas collides with the exhaust gas sensor in a state where the flow velocity of the exhaust gas discharged from each cylinder is high, the sensor responsiveness can be ensured.

Effects of the Invention

[0023] According to the present invention, in a merging portion connected to the downstream side of an exhaust passage communicating with each cylinder, the main flow of exhaust gas is diffused and and dispersed to reduce the flow velocity, and the flow velocity passing through the catalyst can be reduced. Therefore, the purification characteristics can be improved without increasing the size of the catalyst.

Brief Description of the Drawings

[0024]

Figure 1

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Embodiments for Carrying Out the Invention

[0025] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. Here, an exhaust gas purification device for an internal combustion engine equipped with an in-line cylinder engine will be described.

[0026] <First Embodiment> As shown in FIGS. 1 and 2, an exhaust gas purification device 1 for an internal combustion engine according to the present invention includes a plurality of, i.e., in-line, first to fourth cylinders 10a, 10b, 10c, 10d (hereinafter referred to as the first to fourth cylinders 10a, 10b, 10c, 10d) provided in a cylinder head 3 of an engine 2. A confluence portion 30 is connected to the downstream side of exhaust passages 20a to 20d formed by first to fourth exhaust pipes communicating with the cylinders, and a catalytic converter 40 is connected to the downstream side below the confluence portion 30.

[0027] The engine 2 communicates with each of the cylinders 10a to 10d provided in the cylinder head 3, and one ends of first to fourth exhaust ports 11a to 11d for guiding exhaust gas generated in each of the cylinders 10a to 10d are open in the horizontal direction. In FIG. 1, the cylinder row is composed of a first cylinder 10a, a second cylinder 10b, a third cylinder 10c, and a fourth cylinder 10d in order from the upper end side to the lower end side. The first to fourth exhaust ports 11a to 11d correspond to each of the first to fourth cylinders 10a to 10d.

[0028] In the first to fourth cylinders 10a to 10d, for example, combustion is repeatedly performed while shifting the timing in the order of the first cylinder 10a, the third cylinder 10c, the fourth cylinder 10d, and the second cylinder 10b. Therefore, exhaust gas is continuously discharged separately from each of the exhaust ports 11a to 11d of the first to fourth exhaust ports 11a to 11d while shifting the timing.

[0029] Each of the first to fourth exhaust passages 20a to 20d has an upstream end connected to a mounting flange 22 fixed to the cylinder head 3, and communicates with the corresponding first to fourth cylinders 10a to 10d via the first to fourth exhaust ports 11a to 11d. The first to fourth exhaust passages 20a to 20d extend rearward away from the engine 2 while being arranged side by side at a constant interval along the cylinder row. The downstream ends of these first to fourth exhaust passages 20a to 20d are connected to a merging portion 30 and communicate with each other. The merging portion 30 is disposed at a position intermediate the first to fourth exhaust ports 11a to 11d with respect to the cylinder head 3.

[0030] Among the first to fourth exhaust passages 20a to 20d, the first exhaust passage 11a and the fourth exhaust passage 11d are symmetrically arranged with respect to an imaginary line (not shown) connecting the middle of the cylinder head 3 and the center of the merging portion 30, and the tip sides of the linear portions extending rearward from the cylinder head 3 are connected to the merging portion 30 in a state inclined toward the merging portion 30 via the bent portions 21. The downstream end of the first exhaust passage 20a and the downstream end of the fourth exhaust passage 11d project into the merging portion 30 to form a diffusion portion 32 described later.

[0031] The second exhaust passage 20b and the third exhaust passage 20c are symmetrically arranged with respect to an imaginary line (not shown) connecting the middle of the cylinder head 3 and the center of the merging portion 30, and are connected to the merging portion 30 while being slightly bent toward the rear of the engine 2.

[0032] The confluence section 30 is provided with an inlet 31 to which each of the first to fourth exhaust passages 20a to 20d is connected. The ends of the first exhaust passage 11a and the fourth exhaust passage 11d connected to the inlet 31 project into the confluence section 30, thereby forming a diffusion section 32 that promotes the jet flow of the main stream of the exhaust gas flowing into the confluence section 30 (see Fig. 1(b)). By forming the diffusion section 32 in this way, the jet flow of the main stream of the exhaust gas flowing into the confluence section 30 from the first exhaust passage 11a and the fourth exhaust passage 11d peels off the flow of the exhaust gas stagnating on the wall sides of the first exhaust passage 11a and the fourth exhaust passage 11d from the wall and entrains the surrounding stationary gas, so that the flow can be diffused. As a result, the flow velocity of the exhaust gas decreases, and the flow in the direction of the catalyst of the catalytic converter 40 can be reduced.

[0033] In the confluence section 30, a dispersion surface 33 is formed on the inner wall of the confluence section 30 facing the inlet 31 that connects the first exhaust passage 11a and the fourth exhaust passage 20d, for three-dimensionally dispersing the main stream of the exhaust gas flowing linearly into the confluence section 30 from the inlet 31. In this case, the dispersion surface 33 is provided so as to be substantially orthogonal to the axes of the first exhaust passage 11a and the fourth exhaust passage 11d. Further, the dispersion surface 33 is provided so as to be substantially orthogonal to the axis along the outer wall of the bent portion 21 of the first exhaust passage 11a and the fourth exhaust passage 20d.

[0034] Also, in the confluence section 30, a dispersion surface 33 is formed on the inner wall of the confluence section 30 facing the inlet 31 that connects the second exhaust passage 20b and the third exhaust passage 20c, for three-dimensionally dispersing the main stream of the exhaust gas flowing linearly into the confluence section 30 from the inlet 31. In this case, the dispersion surface 33 is provided so as to be substantially orthogonal to the axes of the second exhaust passage 20b and the third exhaust passage 20c. In Fig. 1, for the sake of clarity of the dispersion surface 33, it is shown by a straight line.

[0035] Further, as shown in FIG. 2, the dispersion surface 33 is formed by an inclined surface 34 with an obtuse angle on the upper side with respect to the dispersion surface 33 along the vertical direction. By forming the dispersion surface 33 in this way with the inclined surface 34 having an obtuse angle on the upper side, the dispersion direction of the exhaust gas can be induced upward, and further the flow in the catalyst direction can be reduced.

[0036] An air-fuel ratio sensor 50 for measuring the air-fuel ratio (A / F) of the exhaust gas flowing out from each of the cylinders 10a to 10d is provided at a site where the main streams of the exhaust gas flowing into the confluence portion 30 from the first to fourth exhaust passages 20a to 20d in the confluence portion 30 intersect. By providing the air-fuel ratio sensor 50 at the site where the main streams of the exhaust gas flowing into the confluence portion 30 from the first to fourth exhaust passages 20a to 20d intersect, since the air-fuel ratio sensor 50 collides with the exhaust gas at a high flow velocity discharged from each of the cylinders 10a to 10d, the sensor responsiveness can be ensured. Note that the measurement data detected by the air-fuel ratio sensor 50 is transmitted to a control unit (not shown), and the combustion conditions of each of the cylinders 10a to 10d are controlled by the control unit based on the measured values.

[0037] Next, regarding the flow of the exhaust gas discharged from each of the cylinders 10a to 10d in the exhaust purification device 1 of the first embodiment, it will be described with reference to FIGS. 3A to 3D.

[0038] The main stream of the exhaust gas discharged from the first cylinder 10a flows along the outer wall of the bent portion 21 of the first exhaust passage 20a connected to the first exhaust port 11a and into the inlet 31 of the confluence portion 30 as indicated by the arrow in FIG. 3A. The main stream of the exhaust gas flowing into the confluence portion 30 becomes a jet flow by the diffusion portion 32 and flows into the confluence portion 30. Due to this jet flow of the exhaust gas, the flow of the exhaust gas that accumulates on the wall side of the first exhaust passage 20a is peeled off from the wall. Further, as shown in FIG. 3A(b), the stationary gas around the inlet 31 is entrained by the jet flow of the exhaust gas and the exhaust gas is diffused, and the flow velocity of the exhaust gas decreases.

[0039] In addition, the main flow of the exhaust gas that linearly flows into the confluence section 30 collides with the dispersion surface 33 facing the inlet 31, and the flow is dispersed three-dimensionally at the collision section as shown in Figures 3A(a) and 4A. This reduces the flow velocity of the exhaust gas.

[0040] As shown by the arrows in Fig. 3B, the main stream of exhaust gas discharged from the second cylinder 10b flows through the second exhaust passage 20b connected to the second exhaust port 11b and enters the inlet 31 of the junction 30. The main stream of exhaust gas that flows linearly into the junction 30 collides with the dispersion surface 33 facing the inlet 31, and is dispersed three-dimensionally at the collision portion as shown in Figs. 3B and 4A. This reduces the flow velocity of the exhaust gas.

[0041] The main stream of exhaust gas discharged from the third cylinder 10c flows through the third exhaust passage 20c connected to the third exhaust port 11b, as shown by the arrows in Fig. 3C, and enters the inlet 31 of the junction 30. The main stream of exhaust gas that flows linearly into the junction 30 collides with the dispersion surface 33 facing the inlet 31, and is dispersed three-dimensionally at the collision portion, as shown in Figs. 3C and 4A. This reduces the flow velocity of the exhaust gas.

[0042] As shown by the arrows in FIG. 3D, the mainstream of exhaust gas discharged from the fourth cylinder 10d flows along the outer wall of the bent portion 21 of the fourth exhaust passage 20d connected to the fourth exhaust port 11d, and flows into the inlet 31 of the junction 30. The mainstream of exhaust gas flowing into the junction 30 is turned into a jet by the diffusion portion 32 and flows into the junction 30. This jet of exhaust gas separates the exhaust gas flow stagnating on the wall side of the fourth exhaust passage 20a from the wall. In addition, as shown in FIG. 3D(b), the jet of exhaust gas entrains stationary gas around the inlet 31, diffusing the exhaust gas and decreasing the flow velocity of the exhaust gas.

[0043] In addition, the main stream of exhaust gas that linearly flows into the confluence section 30 collides with the dispersion surface 33 facing the inlet 31, and is dispersed three-dimensionally at the collision section as shown in Fig. 3D(a) and Fig. 4A. This reduces the flow velocity of the exhaust gas.

[0044] As described above, the main stream of the exhaust gas discharged from each of the cylinders 10a to 10d flows through the first to fourth exhaust passages 20a to 20d connected to the respective exhaust ports 11a to 11d communicating with the cylinders 10a to 10d, flows into the confluence section 30, and the flow velocity is reduced by diffusion by the jet flow of the diffusion section 32 and dispersion by collision with the dispersion surface 33. Therefore, since the exhaust gas with the reduced flow velocity is sent to the catalytic converter 40 on the downstream side of the confluence section 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

[0045] In addition, as shown in FIG. 4B, by forming the dispersion surface 33 with an inclined surface 34 having an obtuse angle on the upper side with respect to the dispersion surface 33 along the vertical direction, the dispersion direction of the exhaust gas can be induced upward, so that the flow in the catalyst direction can be further reduced.

[0046] <Second Embodiment> As shown in FIGS. 5 and 6, in the exhaust purification device 1A of the second embodiment, the confluence section 30 is arranged at an intermediate position between the third exhaust port 11c communicating with the third cylinder 10c and the fourth exhaust port 11d communicating with the fourth cylinder 10d with respect to the cylinder head 3. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals and will be described.

[0047] In the exhaust purification device 1A of the second embodiment, the first exhaust passage 20a communicating with the first cylinder 10a is connected in a state where the tip side of the linear portion extending rearward of the engine from the cylinder head 3 is inclined toward the confluence section 30 via the bent portion 21. The second exhaust passage 20b communicating with the second cylinder 10b is connected to the downstream side of the bent portion 21 of the first exhaust passage 20a by a linear portion extending rearward of the engine 2 from the cylinder head 3. The third exhaust passage 20c communicating with the third cylinder 10c and the fourth exhaust passage 20d communicating with the fourth cylinder 10d are connected to the confluence section 30 with a slight bend toward the rear of the engine 2.

[0048] In the confluence section 30, an inlet 31 is provided to which each of a first exhaust passage 20a connecting to a second exhaust passage 20b, a third exhaust passage 20c, and a fourth exhaust passage 20d is connected.

[0049] In the confluence section 30, a dispersion surface 33 is formed on the inner wall of the confluence section 30 facing the inlet 31 connecting to the first exhaust passage 11a, for three-dimensionally dispersing the main stream of the exhaust gas flowing linearly into the confluence section 30 from the inlet 31. In this case, the dispersion surface 33 is provided so as to be substantially orthogonal to the axis of the first exhaust passage 11a. Also, the dispersion surface 33 is provided so as to be substantially orthogonal to the axis along the outer wall of the bent portion 21 of the first exhaust passage 11a.

[0050] Also, in the confluence section 30, a dispersion surface 33 is formed on the inner wall of the confluence section 30 facing the inlet 31 connecting the third exhaust passage 20c and the fourth exhaust passage 20d, for three-dimensionally dispersing the main stream of the exhaust gas flowing linearly into the confluence section 30 from the inlet 31. In this case, the dispersion surface 33 is provided so as to be substantially orthogonal to the axes of the third exhaust passage 20c and the fourth exhaust passage 20d. In FIG. 5, for the sake of easy understanding of the dispersion surface 33, it is shown by a straight line.

[0051] At a portion where the main streams of the exhaust gas flowing into the confluence section 30 from the first exhaust passage 20a, the third exhaust passage 20c, and the fourth exhaust passage 20d in the confluence section 30 intersect, an air-fuel ratio sensor 50 for measuring the air-fuel ratio (A / F) of the exhaust gas flowing out from each of the cylinders 10a to 10d is provided. In this way, by providing the air-fuel ratio sensor 50 at the portion where the main streams of the exhaust gas flowing into the confluence section 30 from the first exhaust passage 20a, the third exhaust passage 20c, and the fourth exhaust passage 20d intersect, since the air-fuel ratio sensor 50 collides with the exhaust gas at a high flow rate discharged from each of the cylinders 10a to 10d, sensor responsiveness can be ensured. The measurement data detected by the air-fuel ratio sensor 50 is transmitted to a control unit (not shown), and the combustion conditions of each of the cylinders 10a to 10d are controlled by the control unit based on the measured values.

[0052] Next, in the exhaust gas purification device 1A of the second embodiment, the flow of the exhaust gas discharged from each of the cylinders 10a to 10d will be described with reference to FIGS. 7A to 7D.

[0053] The main stream of the exhaust gas discharged from the first cylinder 10a flows along the outer wall of the bent portion 21 of the first exhaust passage 20a connected to the first exhaust port 11a, as indicated by the arrow in FIG. 7A, and flows into the inlet 31 of the confluence portion 30. The main stream of the exhaust gas that has flowed linearly into the confluence portion 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion as shown in FIG. 7A. As a result, the flow velocity of the exhaust gas decreases.

[0054] The main stream of the exhaust gas discharged from the second cylinder 10b flows through the second exhaust passage 20b connected to the second exhaust port 11b, as indicated by the arrow in FIG. 7B, flows to the downstream side of the bent portion 21 of the first exhaust passage 20a, and then flows along the outer wall of the bent portion 21 and into the inlet 31 of the confluence portion 30. The main stream of the exhaust gas that has flowed linearly into the confluence portion 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion as shown in FIG. 7B. As a result, the flow velocity of the exhaust gas decreases.

[0055] The main stream of the exhaust gas discharged from the third cylinder 10c flows through the third exhaust passage 20c connected to the third exhaust port 11b, as indicated by the arrow in FIG. 7C, and flows into the inlet 31 of the confluence portion 30. The main stream of the exhaust gas that has flowed linearly into the confluence portion 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion as shown in FIG. 7C. As a result, the flow velocity of the exhaust gas decreases.

[0056] The main stream of the exhaust gas discharged from the fourth cylinder 10d flows along the outer wall of the bent portion 21 of the fourth exhaust passage 20d connected to the fourth exhaust port 11d, as indicated by the arrow in FIG. 7D, and flows into the inlet 31 of the confluence portion 30. The main stream of the exhaust gas that has flowed linearly into the confluence portion 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion as shown in FIG. 7D. As a result, the flow velocity of the exhaust gas decreases.

[0057] As described above, the main stream of the exhaust gas discharged from each of the cylinders 10a to 10d flows through the first to fourth exhaust passages 20a to 20d connected to the respective exhaust ports 11a to 11d communicating with the cylinders 10a to 10d, flows into the confluence portion 30, and the flow velocity is reduced by dispersion due to collision with the dispersion surface 33. Therefore, since the exhaust gas with the reduced flow velocity is sent to the catalytic converter 40 on the downstream side of the confluence portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

[0058] In addition, in the third exhaust passage 20c and the fourth exhaust passage 20d communicating with the third cylinder 10c and the fourth cylinder 10d, as shown in FIG. 6, by making the angle between the lower surface 20e of the inlet portion of these third and fourth exhaust passages 20c and 20d and the wall surface end face 30a of the confluence portion 30 substantially a right angle, the dispersion of the exhaust gas can be promoted. Further, as shown in FIG. 6, by forming the dispersion surface 33 with an inclined surface 34 having an obtuse angle on the upper side, the dispersion direction of the exhaust gas can be induced upward, so that the flow in the catalyst direction can be further reduced.

[0059] As described above, the main stream of the exhaust gas discharged from each of the cylinders 10a to 10d flows through the first to fourth exhaust passages 20a to 20d connected to the respective exhaust ports 11a to 11d communicating with the cylinders 10a to 10d, flows into the confluence portion 30, and the flow velocity is reduced by dispersion due to collision with the dispersion surface 33. Therefore, since the exhaust gas with the reduced flow velocity is sent to the catalytic converter 40 on the downstream side of the confluence portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

[0060] <Third Embodiment> As shown in FIGS. 8, 9A, and 9B, the exhaust gas purification device 1B of the third embodiment is a case where a confluence portion 30 is disposed at a position intermediate between a third exhaust port 11c communicating with the third cylinder 10c and a fourth exhaust port 11d communicating with the fourth cylinder 10d with respect to the cylinder head 3, and an exhaust passage 20B communicating with each of the exhaust ports 11a to 11d is integrally formed. In the third embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals and will be described.

[0061] In the exhaust gas purification device 1B of the third embodiment, as shown in FIGS. 9A and 9B, the exhaust passage 20B has openings 23 communicating with each of the exhaust ports 11a to 11d, and the outer wall on the side of the first exhaust port 11a is connected to the confluence portion 30 in a state of expanding and inclining toward the confluence portion 30 via a bent portion 21 at the tip side of a linear portion extending rearward from the cylinder head 3 of the engine 2. Further, in the exhaust passage 20B, the tip side of the outer wall on the side of the fourth exhaust port 11d, which is a linear portion extending rearward from the cylinder head 3, is gently bent and connected to the confluence portion 30.

[0062] In this case, an inclined wall surface 24 that inclines toward the confluence portion 30 from the bent portion 21 in the exhaust passage 20B is formed such that the exhaust gas discharged from the first cylinder 10a, the second cylinder 10b, and the third cylinder 10c collides therewith. By forming it in this way, the main flow of the exhaust gas that collides with the inclined wall surface 24 of the exhaust gas discharged from the first cylinder 10a, the second cylinder 10b, and the third cylinder 10c flows into the confluence portion 30 along the inclined wall surface 24.

[0063] The confluence section 30 is provided with an inlet 31 for connecting the exhaust passage 20B. On the inner wall of the confluence section 30 facing the inlet 31, a dispersion surface 33 is formed to three-dimensionally disperse the main flow of the exhaust gas flowing linearly into the confluence section 30 from the inlet 31. In this case, the dispersion surface 33 is provided so as to be substantially orthogonal to the axis along the inclined wall surface 24. Further, the dispersion surface 33 is formed on the inner wall of the confluence section 30 facing the inlet 31 where the exhaust gas discharged from the fourth cylinder 10d flows in, to three-dimensionally disperse the main flow of the exhaust gas flowing linearly into the confluence section 30 from the inlet 31.

[0064] In the confluence section 30, at a position where the main flow of the exhaust gas flowing into the confluence section 30 along the inclined wall surface 24 intersects with the main flow of the exhaust gas discharged from the fourth cylinder 10d and flowing into the confluence section 30, an air-fuel ratio sensor 50 for measuring the air-fuel ratio (A / F) of the exhaust gas flowing out from each of the cylinders 10a to 10d is provided. In this way, by providing the air-fuel ratio sensor 50 at a position where the main flow of the exhaust gas flowing into the confluence section 30 along the inclined wall surface 24 intersects with the main flow of the exhaust gas discharged from the fourth cylinder 10d and flowing into the confluence section 30, since the exhaust gas discharged from each of the cylinders 10a to 10d collides with the air-fuel ratio sensor 50 at a high flow velocity state, the sensor responsiveness can be ensured. Note that the measurement data detected by the air-fuel ratio sensor 50 is transmitted to a control unit (not shown), and the combustion conditions of each of the cylinders 10a to 10d are controlled by the control unit based on the measured values.

[0065] Next, regarding the flow of the exhaust gas discharged from each of the cylinders 10a to 10d in the exhaust purification device 1B of the third embodiment, it will be described with reference to FIGS. 9A and 9B.

[0066] The main flow of the exhaust gas discharged from the first cylinder 10a collides with the inclined wall surface 24 of the exhaust passage 20B as indicated by the solid arrow in FIG. 9A, and then flows along the inclined wall surface 24 and enters the inlet 31 of the confluence section 30. When the flow along the inclined wall surface 24 enters the confluence section 30, it becomes a jet flow due to the sudden expansion, peels off the flow of the exhaust gas that accumulates on the outer wall side of the exhaust passage 20B from the wall, and entrains and diffuses the surrounding stationary gas. Then, the main flow of the exhaust gas that linearly enters the confluence section 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision part as shown in FIG. 9A. As a result, the flow velocity of the exhaust gas decreases.

[0067] The main flow of the exhaust gas discharged from the second cylinder 10b collides with the inclined wall surface 24 of the exhaust passage 20B as indicated by the dashed arrow in FIG. 9A, and then flows along the inclined wall surface 24 and enters the inlet 31 of the confluence section 30. When the flow along the inclined wall surface 24 enters the confluence section 30, it becomes a jet flow due to the sudden expansion, peels off the flow of the exhaust gas that accumulates on the outer wall side of the exhaust passage 20B from the wall, and entrains and diffuses the surrounding stationary gas. Then, the main flow of the exhaust gas that linearly enters the confluence section 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision part as shown in FIG. 9A. As a result, the flow velocity of the exhaust gas decreases.

[0068] The main flow of the exhaust gas discharged from the third cylinder 10c collides with the inclined wall surface 24 of the exhaust passage 20B as indicated by the dash-dotted arrow in FIG. 9A, and then flows along the inclined wall surface 24 and enters the inlet 31 of the confluence section 30. When the flow along the inclined wall surface 24 enters the confluence section 30, it becomes a jet flow due to the sudden expansion, peels off the flow of the exhaust gas that accumulates on the outer wall side of the exhaust passage 20B from the wall, and entrains and diffuses the surrounding stationary gas. Then, the main flow of the exhaust gas that linearly enters the confluence section 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision part as shown in FIG. 9A. As a result, the flow velocity of the exhaust gas decreases.

[0069] The main stream of the exhaust gas discharged from the fourth cylinder 10d flows into the inlet 31 of the exhaust passage 20B connected to the fourth exhaust port 11d, as indicated by the arrow in Fig. 9B. The main stream of the exhaust gas that linearly flows into the confluence section 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision section, as shown in Fig. 9B. As a result, the flow velocity of the exhaust gas decreases.

[0070] As described above, the main stream of the exhaust gas discharged from the first to third cylinders 10a to 10c collides with the inclined wall surface 24 of the exhaust passage 20B, then flows along the inclined wall surface 24 and into the inlet 31 of the confluence section 30, collides with the dispersion surface 33 facing the inlet 31, and is three-dimensionally dispersed with respect to the collision section. The flow velocity decreases due to the dispersion caused by the collision with the dispersion surface 33. Also, the main stream of the exhaust gas discharged from the fourth cylinder 10d flows into the inlet 31 of the confluence section 30 to form a jet flow, peels off the flow of the exhaust gas that accumulates on the outer wall of the exhaust passage 20B from the wall, and entrains and diffuses the surrounding stationary gas. Further, the main stream of the exhaust gas flowing into the confluence section 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision section. Therefore, since the exhaust gas with the reduced flow velocity is sent to the catalytic converter 40 on the downstream side of the confluence section 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

[0071] <Fourth Embodiment> In the exhaust gas purification device 1C of the fourth embodiment, as shown in Figs. 10 and 11, the exhaust passage 20C communicating with the collective exhaust port 12 that aggregates the exhaust ports 11a to 11d communicating with the respective cylinders 10a to 10d is connected to the confluence section 30. In this case, the discharge port 13 of the collective exhaust port 12 is provided at a position intermediate between the second exhaust port 11b and the third exhaust port 11c. In the fourth embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals and will be described.

[0072] In the exhaust gas purification device 1C of the fourth embodiment, the confluence portion 30 is disposed at an intermediate position between a second exhaust port 11b communicating with the second cylinder 10b and a third exhaust port 11c communicating with the third cylinder 10c with respect to the cylinder head 3 via an exhaust passage 20C communicating with the discharge port 13 of the collective exhaust port 12.

[0073] The confluence portion 30 is provided with an inlet 31 for connecting the exhaust passage 20C, and a diffusion portion 32C for promoting the main stream jet of the exhaust gas flowing into the confluence portion 30 is provided at a connection portion with the exhaust passage 20C. In this case, the diffusion portion 32C is formed by a step at the connection portion between the exhaust passage 20C and the confluence portion 30.

[0074] Further, on the inner wall of the confluence portion 30 facing the inlet 31, a dispersion surface 33 for three-dimensionally dispersing the main stream of the exhaust gas linearly flowing into the confluence portion 30 from the inlet 31 along the wall surface 25 of the exhaust passage 20C is formed.

[0075] In the confluence portion 30, at a site where the main streams of the exhaust gas discharged from the respective cylinders 10a to 10d and flowing into the confluence portion 30 along the wall surface 25 of the exhaust passage 20C intersect, in the same manner as in the first to third embodiments, an air-fuel ratio sensor 50 for measuring the air-fuel ratio (A / F) of the exhaust gas flowing out from the respective cylinders 10a to 10d is provided.

[0076] Next, in the exhaust gas purification device 1C of the fourth embodiment, the flow of the exhaust gas discharged from the respective cylinders 10a to 10d will be described with reference to FIGS. 12 and 13. Since the first cylinder 10a, the fourth cylinder 10d and the second cylinder 10b, the third cylinder 10c have a symmetric shape, here, the first cylinder 10a and the second cylinder 10b will be described.

[0077] The exhaust gas discharged from the first cylinder 10a flows, as indicated by the arrow in FIG. 12, greatly bent and flows into the confluence portion 30 along the wall surface 25 of the exhaust passage 20C from the discharge port 13 of the collective exhaust port 12. The main stream of the exhaust gas flowing into the confluence portion 30 becomes a jet flow by the diffusion portion 32C formed by the step at the connection portion between the exhaust passage 20C and the confluence portion 30, peels off the flow of the exhaust gas stagnating on the wall side of the exhaust passage 20C from the wall, and entrains and diffuses the surrounding stationary gas. Then, the main stream of the exhaust gas flowing linearly into the confluence portion 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion as shown in FIG. 13. Thereby, the flow velocity of the exhaust gas decreases.

[0078] The exhaust gas discharged from the second cylinder 10b flows substantially linearly into the confluence portion 30 along the wall surface 25 of the exhaust passage 20C from the discharge port 13 of the collective exhaust port 12. The main stream of the exhaust gas flowing into the confluence portion 30 becomes a jet flow by the diffusion portion 32C formed by the step at the connection portion between the exhaust passage 20C and the confluence portion 30, peels off the flow of the exhaust gas stagnating on the wall side of the exhaust passage 20C from the wall, and entrains and diffuses the surrounding stationary gas. Then, the main stream of the exhaust gas flowing linearly into the confluence portion 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion as shown in FIG. 13. Thereby, the flow velocity of the exhaust gas decreases.

[0079] As described above, the main streams of the exhaust gases discharged from the first to fourth cylinders 10a to 10d flow along the wall surface 25 of the exhaust passage 20C and flow into the inlet 31 of the confluence portion 30 to become jet flows, peeling off the flow of the exhaust gas stagnating on the outer wall of the exhaust passage 20C from the wall and entraining and diffusing the surrounding stationary gas. Further, the main stream of the exhaust gas flowing into the confluence portion 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion. Therefore, since the exhaust gas with a reduced flow velocity is sent to the catalytic converter 40 on the downstream side of the confluence portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

[0080] In the exhaust gas purification device 1C of the fourth embodiment, as shown in FIG. 11, by forming the dispersion surface 33 with an inclined surface 34 having an obtuse angle on the upper side, the dispersion direction of the exhaust gas can be guided upward, so that the flow in the catalyst direction can be further reduced.

[0081] Also, in the exhaust gas purification device 1C of the fourth embodiment, as shown in FIG. 14, by making the angle between the lower surface 20e of the inlet portion of the exhaust passage 20C and the wall end surface 30a of the confluence portion 30 substantially a right angle, the dispersion of the exhaust gas can be promoted.

[0082] <Fifth Embodiment> The exhaust gas purification device 1D of the fifth embodiment has a collective exhaust passage 20D provided with a wall 25D on the extension line of the central axis of each of the exhaust passages 20a to 20d communicating with each of the cylinders 10a to 10d, as shown in FIGS. 15 to 17, and the collective exhaust passage 20D is connected to the confluence portion 30. In the fifth embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals for explanation.

[0083] The wall 25D provided in the collective exhaust passage 20D is formed in a direction perpendicular to the central axis of each of the exhaust passages 20a to 20d or the extension line of the wall surface.

[0084] In the exhaust gas purification device 1D of the fifth embodiment, the confluence portion 30 is arranged on the side of the fourth cylinder 10d with respect to the cylinder head 3, and the downstream end of the collective exhaust passage 20D extending through the bent portion 21 in the first exhaust passage 20a is connected to the confluence portion 30 through an elbow portion 26 that bends. The downstream ends of the second to fourth exhaust passages 20b to 20d are connected to the collective exhaust passage 20D.

[0085] The confluence portion 30 connected to the downstream side of the collective exhaust passage 20D is provided with a diffusion portion 32D that promotes the main jet flow of the exhaust gas flowing into the confluence portion 30. In this case, the diffusion portion 32D is formed by a step at the connection portion between the collective exhaust passage 20D (specifically, the elbow portion 26) and the confluence portion 30. Note that the diffusion portion may be formed by protruding the elbow portion 26 into the confluence portion 30.

[0086] Further, in the confluence portion 30, on the inner wall of the confluence portion 30 facing the inlet 31 connecting the collective exhaust passage 20D, a dispersion surface 33 is formed to three-dimensionally disperse the main flow of the exhaust gas linearly flowing into the confluence portion 30 from the inlet 31. In this case, the dispersion surface 33 is provided so as to be substantially orthogonal to the axis of the collective exhaust passage 20D. Further, the dispersion surface 33 is provided so as to be substantially orthogonal to the axis along the wall 26a of the elbow portion 26 of the collective exhaust passage 20D. Note that the dispersion surface 33 may be formed as an inclined surface with an obtuse angle on the upper side in the vertical direction with respect to the axis of the collective exhaust passage 20D.

[0087] Next, in the exhaust gas purification device 1D of the fifth embodiment, the flow of the exhaust gas discharged from each of the cylinders 10a to 10d will be described with reference to FIGS. 15, 18, and 19.

[0088] The exhaust gas discharged from each of the cylinders 10a to 10d flows through each of the cylinders 10a to 10d as indicated by the arrows in FIG. 15, collides with the wall 25D of the collective exhaust passage 20D and is dispersed, and then flows through the collective exhaust passage 20D along the wall 25D and into the confluence portion 30. The main flow of the exhaust gas flowing into the confluence portion 30 becomes a jet flow by the diffusion portion 32D formed by the step at the connection portion between the collective exhaust passage 20D and the confluence portion 30, peels off the flow of the exhaust gas stagnating on the wall side of the collective exhaust passage 20D from the wall, and entrains and diffuses the surrounding stationary gas. Then, the main flow of the exhaust gas linearly flowing into the confluence portion 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion as shown in FIGS. 18 and 19. As a result, the flow velocity of the exhaust gas decreases.

[0089] As described above, the exhaust gas discharged from the first to fourth cylinders 10a to 10d flows through each cylinder 10a to 10d and collides with the wall 25D of the collective exhaust passage 20D and is dispersed, thereby suppressing the variation in the distribution of the exhaust gas discharged from each cylinder 10a to 10d. Then, the exhaust gas with the suppressed variation in distribution flows along the wall 25D of the collective exhaust passage 20D and flows into the inlet 31 of the confluence section 30 to become a jet flow, peeling off the flow of the exhaust gas stagnating on the wall 25D of the collective exhaust passage 20D and entraining the surrounding stationary gas to diffuse. Further, the main flow of the exhaust gas flowing into the confluence section 30 collides with the dispersion surface 33 facing the inlet 31 and is three-dimensionally dispersed with respect to the collision portion. Therefore, since the exhaust gas with the reduced flow velocity is sent to the catalytic converter 40 on the downstream side of the confluence section 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

[0090] In addition, in the exhaust gas purification device 1D of the fifth embodiment, by forming the dispersion surface 33 of the confluence section 30 with an inclined surface (not shown) having an obtuse angle on the upper side, the dispersion direction of the exhaust gas can be induced upward, so that the flow in the catalyst direction can be further reduced.

[0091] In the above embodiment, the case where the engine has four cylinders has been described. However, the present invention is not limited to this, and the engine may have a plurality of cylinders other than four cylinders.

Explanation of reference numerals

[0092] 1, 1A, 1B, 1C, 1D Exhaust gas purification device 2 Engine 3 Cylinder head 10a~10d First to fourth cylinders 11a~11d First to fourth exhaust ports 12 Collective exhaust port 13 Exhaust outlet 20a~20d First to fourth exhaust passages 20e Lower end surface 20B, 20C Exhaust passages 20D Collective exhaust passage 21 Bend 22 Mounting flange 23 Opening 24 Inclined wall surface 25 Wall surface 25D Wall 26 Elbow part 26a Wall 30 Confluence part 31 Inlet 32, 32C, 32D Diffusion part 33 Dispersion surface 34 Inclined surface 40 Catalytic converter 50 Air-fuel ratio sensor.

Claims

1. An exhaust gas purification device for an internal combustion engine having a catalyst converter attached to an engine including a plurality of cylinders and one or more exhaust passages communicating with the plurality of cylinders, in a merging portion connected to the downstream side of the one or more exhaust passages, a diffusion portion is provided that promotes the main jet of exhaust gas flowing into the merging portion by forming a protruding portion where the downstream end portion of the one or more exhaust passages protrudes into the merging portion from the inner surface of the merging portion, and on the inner wall of the merging portion facing the inlet of the exhaust gas provided in the one or more exhaust passages, a dispersion surface is formed that collides with the main stream of the exhaust gas flowing linearly into the merging portion from the inlet and disperses it three-dimensionally, further, the one or more exhaust passages are connected to the merging portion via a bent portion, and an axis along the outer wall of the bent portion and the dispersion surface of the merging portion are substantially orthogonal to each other An exhaust gas purification device for an internal combustion engine, characterized by the above.

2. The exhaust gas purification device for an internal combustion engine according to Claim 1, wherein an air-fuel ratio sensor is provided at a portion where the main streams of the exhaust gas flowing into the merging portion from the plurality of exhaust passages in the merging portion intersect. An exhaust gas purification device for an internal combustion engine, characterized by the above.

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