Exhaust gas control apparatus for internal combustion engine

Abstract

In an exhaust gas control apparatus for an internal combustion engine in which a catalytic converter is attached to an engine having a plurality of cylinders and a plurality of exhaust passages communicating with the plurality of cylinders, a diffusion portion that promotes a jet flow of a main flow of the exhaust gas flowing into the merging portion is provided at a merging portion connected to a downstream side of the exhaust passage. Further, on the inner wall of the merging portion facing the inlet of the exhaust gas provided in the exhaust passage, a dispersion face for three-dimensionally dispersing the main flow of the exhaust gas flowing linearly into the merging portion from the inlet is formed.

Claims

1. An exhaust gas control apparatus comprising: a catalytic converter; a merging portion that connects the catalytic converter to an internal combustion engine; and a diffusion protrusion provided in the merging portion, wherein the internal combustion engine includes a plurality of cylinders and a plurality of exhaust passages respectively communicating with the cylinders, the merging portion has a cylindrical shape and is connected to a downstream side of each of the exhaust passages, the catalytic converter is connected to a downstream side of the merging portion, and the diffusion protrusion is configured to promote a jet flow of a main flow of exhaust gas flowing into the merging portion.

2. The exhaust gas control apparatus according to claim 1, wherein the diffusion protrusion is a downstream end portion of each of the exhaust passages that protrudes into the merging portion.

3. The exhaust gas control apparatus according to claim 1, further comprising an air-fuel ratio sensor merging portion at a section where main flows of the exhaust gas from the exhaust passages converge.

4. An exhaust gas control apparatus comprising: a catalytic converter; and a merging portion that connects the catalytic converter and an internal combustion engine and that is provided with a dispersion surface on an inner wall of the merging portion, wherein the internal combustion engine including a plurality of cylinders and a plurality of exhaust passages respectively communicating with the cylinders, the merging portion has a cylindrical shape and is connected to a downstream side portion of each of the exhaust passages, the catalytic converter is connected to a downstream side of the merging portion, and the dispersion surface faces an outflow opening of exhaust gas in the downstream side portion and that three-dimensionally disperses a main flow of exhaust gas linearly flowed into the merging portion from the outflow opening.

5. The exhaust gas control apparatus according to claim 4, wherein at least one of the exhaust passages is connected to the merging portion via a bent portion, and the dispersion surface provided in the merging portion so as to be orthogonal to an axis along an outer wall of the bent portion.

6. The exhaust gas control apparatus according to claim 5, further comprising a diffusion protrusion provided in the merging portion, the diffusion protrusion being configured to promote a jet flow of the main flow of the exhaust gas flowing into the merging portion.

7. The exhaust gas control apparatus according to claim 6, wherein the diffusion protrusion is a downstream end portion of each of the exhaust passages that protrudes into the merging portion.

8. The exhaust gas control apparatus according to claim 4, wherein: one of the exhaust passages is a manifold exhaust passage connected with the other exhaust passages, the manifold exhaust passage having a wall on an extension line of the center axis of each of the other exhaust passages; and the manifold exhaust passage is connected to the merging portion.

9. The exhaust gas control apparatus according to claim 8, wherein a diffusion protrusion is provided in the merging portion connected to a downstream side portion of the manifold exhaust passage, the diffusion protrusion being configured to promote a jet flow of the main flow of the exhaust gas flowing into the merging portion.

10. The exhaust gas control apparatus according to claim 4, wherein an air-fuel ratio sensor is provided in the merging portion at a section where main flows of the exhaust gas from the exhaust passages converge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

(2) FIG. 1A is a schematic plan view showing a first embodiment of an exhaust gas control apparatus according to the present disclosure;

(3) FIG. 1B is an enlarged sectional view of a portion I of a schematic plan view showing a first embodiment of an exhaust gas control apparatus according to the present disclosure;

(4) FIG. 2 is a schematic side view of the exhaust gas control apparatus of the first embodiment;

(5) FIG. 3A is a schematic plan view illustrating a flow of exhaust gases of a first cylinder in an exhaust gas control apparatus according to a first embodiment;

(6) FIG. 3B is an enlarged cross-sectional view of a II portion of a schematic plan view showing a flow of exhaust gases of a first cylinder in an exhaust gas control apparatus according to a first embodiment;

(7) FIG. 3C is a schematic plan view illustrating a flow of exhaust gases of a second cylinder in an exhaust gas control apparatus according to a first embodiment;

(8) FIG. 3D is a schematic plan view illustrating a flow of exhaust gases of a third cylinder in the exhaust gas control apparatus according to the first embodiment;

(9) FIG. 3E is a schematic plan view illustrating a flow of exhaust gases of a fourth cylinder in an exhaust gas control apparatus according to a first embodiment;

(10) FIG. 3F is an enlarged cross-sectional view of a III portion of a schematic plan view showing a flow of exhaust gases of a fourth cylinder in an exhaust gas control apparatus according to a first embodiment;

(11) FIG. 4A is a schematic side view illustrating a flow of exhaust gases in an exhaust gas control apparatus according to a first embodiment;

(12) FIG. 4B is a schematic side view illustrating a flow of exhaust gases obtained by deforming a dispersion face in an exhaust gas control apparatus according to a first embodiment;

(13) FIG. 5 is a schematic plan view showing a second embodiment of the exhaust gas control apparatus according to the present disclosure;

(14) FIG. 6 is a schematic side view of an exhaust gas control apparatus according to a second embodiment;

(15) FIG. 7A is a schematic plan view illustrating a flow of exhaust gases of a first cylinder in an exhaust gas control apparatus according to a second embodiment;

(16) FIG. 7B is a schematic plan view illustrating a flow of exhaust gases of a second cylinder in an exhaust gas control apparatus according to a second embodiment;

(17) FIG. 7C is a schematic plan view illustrating a flow of exhaust gases of a third cylinder in an exhaust gas control apparatus according to a second embodiment;

(18) FIG. 7D is a schematic plan view illustrating a flow of exhaust gases of a fourth cylinder in an exhaust gas control apparatus according to a second embodiment;

(19) FIG. 8 is a schematic plan view showing a third embodiment of the exhaust gas control apparatus according to the present disclosure;

(20) FIG. 9A is a schematic plan view illustrating a flow of exhaust gases of the first to third cylinders in the exhaust gas control apparatus of the third embodiment;

(21) FIG. 9B is a schematic plan view illustrating a flow of exhaust gases of a fourth cylinder in an exhaust gas control apparatus according to the third embodiment;

(22) FIG. 10 is a schematic plan view showing a fourth embodiment of the exhaust gas control apparatus according to the present disclosure;

(23) FIG. 11 is a schematic side view of an exhaust gas control apparatus according to a fourth embodiment;

(24) FIG. 12 is a schematic plan view showing a flow of exhaust gas in the exhaust gas control apparatus according to the fourth embodiment;

(25) FIG. 13 is a schematic side view showing a flow of exhaust gas in the exhaust gas control apparatus of the fourth embodiment;

(26) FIG. 14 is a schematic side view showing a modification of the exhaust gas control apparatus according to the fourth embodiment;

(27) FIG. 15 is a schematic perspective view showing a fifth embodiment of the exhaust gas control apparatus according to the present disclosure;

(28) FIG. 16 is a schematic side view of an exhaust gas control apparatus according to a fifth embodiment;

(29) FIG. 17 is a schematic front view of an exhaust gas control apparatus according to a fifth embodiment;

(30) FIG. 18 is a schematic side view showing the flow of exhaust gases in the exhaust gas control apparatus of the fifth embodiment; and

(31) FIG. 19 is a schematic front view illustrating a flow of exhaust gas in the exhaust gas control apparatus of the fifth embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

(32) Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

(33) Here, an exhaust gas control apparatus of an internal combustion engine including an engine of a series cylinder will be described.

First Embodiment

(34) Exhaust gas control apparatus 1 of an internal combustion engine according to the present disclosure, as shown in FIGS. 1A, 1B, and 2, a merging portion 30 is connected to a downstream side of the exhaust passages 20a to 20d formed of first to fourth exhaust pipes communicating with a plurality of, i.e., first to fourth cylinder 10a, 10b, 10c, 10d in series (hereinafter referred to as first to fourth cylinder 10a, 10b, 10c, 10d) provided in cylinder head 3 of engine 2, and a catalytic converter 40 is connected to a downstream side below merging portion 30.

(35) The engine 2 communicates with the respective cylinders 10a to 10d provided in the cylinder head 3, and one end of 11d is horizontally opened from the first to fourth exhaust ports 11a for discharging the exhaust gases generated in the respective cylinders 10a to 10d. Note that, in FIGS. 1A and 1B, the cylinder row is constituted by the first cylinder 10a, second cylinder 10b, third cylinder 10c and the fourth cylinder 10d in order from the upper end side toward the lower end side. The first to fourth exhaust ports 11a to 11d correspond to each of 10d from the first to fourth cylinder 10a.

(36) From the first to fourth cylinders 10a to 10d, for example, the first cylinder 10a, the third cylinder 10c, the fourth cylinder 10d, and the second cylinder 10b are repeatedly burned while being shifted in the order of the timings. Therefore, from the first to fourth exhaust ports 11a to 11d, the exhaust gases are continuously discharged from each of to the exhaust ports 11a to 11d while being shifted in timing.

(37) Each of the first to fourth exhaust passages 20a to 20d is connected at its upstream end to a mounting flange 22 fixed to the cylinder head 3 and communicates with the corresponding first to fourth cylinder 10a to 10d via a the first to fourth exhaust port 11a to 11d. The first to fourth exhaust passages 20a to 20d extend rearward away from the engine 2 at regular intervals laterally along the cylinder row. The downstream-side end portions of 20d from the first to fourth exhaust passages 20a are connected to the merging portion 30 and are in communication with each other. The merging portion 30 is disposed at a position intermediate from the first to fourth exhaust ports 11a to 11d with respect to the cylinder head 3.

(38) Of the first to fourth exhaust passages 20a to 20d, the first exhaust port 11a and the fourth exhaust port 11d are arranged symmetrically with respect to an imaginary line (not shown) connecting the middle of the cylinder head 3 and the central portion of the merging portion 30, and the leading end sides of the straight portions extending rearward from the cylinder head 3 are connected to the merging portion 30 through the bent portion 21. The downstream end portion of the first exhaust passage 20a and the downstream end portion of the fourth exhaust port 11d protrude into the merging portion 30 to form a diffusion portion 32 to be described later.

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

(40) The merging portion 30 is provided with an inflow port 31 to which each of the first to fourth exhaust passages 20a to 20d is connected, and the end portion of the first exhaust port 11a and the end portion of the fourth exhaust port 11d connected to the inflow port 31 are protruded into the merging portion 30, thereby forming a diffusion portion 32 that promotes the jet flow of the main flow of the exhaust gas flowing into the merging portion 30 (see FIG. 1B). By forming the diffusion portion 32 in this manner, the flow of the exhaust gas stagnating toward the wall of the first exhaust port 11a and the fourth exhaust port 11d is separated from the wall by the jet of the main flow of the exhaust gas flowing into the merging portion 30 from the first exhaust port 11a and the fourth exhaust port 11d, and the surrounding stationary gas is entrained, whereby the flow can be diffused. As a result, the flow rate of the exhaust gas decreases, and the flow of the catalytic converter 40 in the catalytic direction can be reduced.

(41) In the merging portion 30, on the inner wall of the merging portion 30 opposed to the inflow port 31 connecting the first exhaust port 11a and the fourth exhaust passage 20d, a dispersion face 33 is formed which three-dimensionally disperses the main flow of the exhaust gases linearly flowing from the inflow port 31 into the merging portion 30. Here, the dispersion face 33 is provided so as to be substantially perpendicular to the first exhaust port 11a and the shaft of the fourth exhaust port 11d. Further, the dispersion face 33 is provided so as to be substantially perpendicular to the first exhaust port 11a and the shaft along the outer wall of the bent portion 21 of the fourth exhaust passage 20d.

(42) Further, in the merging portion 30, on the inner wall of the merging portion 30 opposed to the inflow port 31 connecting the second exhaust passage 20b and the third exhaust passage 20c, a dispersion face 33 is formed which three-dimensionally disperses the main flow of the exhaust gases flowing linearly from the inflow port 31 into the merging portion 30. Here, the dispersion face 33 is provided so as to be substantially perpendicular to the second exhaust passage 20b and the shaft of the third exhaust passage 20c. Note that, in FIGS. 1A and 1B, the dispersion face 33 is indicated by a straight line for clarity.

(43) Further, as shown in FIG. 2, the dispersion face 33 is formed by an inclined surface 34 whose upper side is obtuse with respect to the dispersion face 33 along the vertical direction. By forming the dispersion face 33 with the inclined surface 34 having an obtuse upper side as described above, the dispersion direction of the exhaust gas can be guided upward, and the flow in the catalyst direction can be further reduced.

(44) An air-fuel ratio sensor 50 for measuring an air-fuel ratio (A/F) of the exhaust gas flowing out of the respective cylinders 10a to 10d is provided at a portion where the main flow of the exhaust gas flowing into the merging portion 30 from the first to fourth exhaust passages 20a to 20d is alternating with each other in the merging portion 30. As described above, by providing the air-fuel ratio sensor 50 at a portion where the main flow of the exhaust gas flowing from the first to fourth exhaust passages 20a to 20d into the merging portion 30 is alternating with each other, the flow rate of the exhaust gas discharged from the respective cylinders 10a to 10d is fast and collides with the air-fuel ratio sensor 50, so that the sensor responsiveness can be secured. The measurement data detected by the air-fuel ratio sensor 50 is transmitted to a control unit (not shown), and the combustion condition of the cylinders 10a to 10d is controlled based on the measurement value by the control unit.

(45) Next, in the exhaust gas control apparatus 1 of the first embodiment, the flow of the exhaust gas discharged from the respective cylinders 10a to 10d will be described referring to FIGS. 3A to 3F.

(46) The main flow 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 flows into the inflow port 31 of the merging portion 30, as indicated by arrows in FIGS. 3A and 3B. The main flow of the exhaust gas flowing into the merging portion 30 becomes a jet flow by the diffusion portion 32 and flows into the merging portion 30. Due to the jet of the exhaust gas, the flow of the exhaust gas stagnating toward the wall of the first exhaust passage 20a is separated from the wall. Further, as shown in FIG. 3B, the stationary gas around the inflow port 31 is entrained by the jet of the exhaust gas, and the exhaust gas is diffused, so that the flow rate of the exhaust gas decreases.

(47) Further, the main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and the flow is three-dimensionally dispersed with respect to the colliding portion as shown in FIGS. 3A and 4A. This reduces the flow rate of the exhaust gas.

(48) The main flow of the exhaust gas discharged from the second cylinder 10b flows through the second exhaust passage 20b connected to the second exhaust port 11b and flows into the inflow port 31 of the merging portion 30, as indicated by an arrow in FIG. 3C. The main flow of the exhaust gas linearly flowing into the merging portion 30 collides with the dispersion face 33 facing the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIGS. 3C and 4A. This reduces the flow rate of the exhaust gas.

(49) The main flow of the exhaust gas discharged from the third cylinder 10c flows through the third exhaust passage 20c connected to the third exhaust port 11c and flows into the inflow port 31 of the merging portion 30, as indicated by an arrow in FIG. 3D. The main flow of the exhaust gas linearly flowing into the merging portion 30 collides with the dispersion face 33 facing the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIGS. 3D and 4A. This reduces the flow rate of the exhaust gas.

(50) The main flow 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 and flows into the inflow port 31 of the merging portion 30, as indicated by arrows in FIGS. 3E and 3F. The main flow of the exhaust gas flowing into the merging portion 30 becomes a jet flow by the diffusion portion 32 and flows into the merging portion 30. Due to the jet of the exhaust gas, the flow of the exhaust gas stagnating toward the wall of the fourth exhaust passage 20d is separated from the wall. Further, as shown in FIG. 3F, the stationary gas around the inflow port 31 is entrained by the jet of the exhaust gas, and the exhaust gas is diffused, so that the flow rate of the exhaust gas decreases.

(51) Further, the main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIGS. 3E and 4A. This reduces the flow rate of the exhaust gas.

(52) As described above, the main flow of the exhaust gases discharged from the respective cylinders 10a to 10d flows through the first to fourth exhaust passage 20a to 20d connected to the respective exhaust ports 11a to 11d communicating from the respective cylinders 10a to 10d and flows into the merging portion 30, and the flow velocity decreases due to the diffusion caused by the jet flow of the diffusion portion 32 and the dispersion caused by the collision with the dispersion face 33. Therefore, since the exhaust gas whose flow rate is reduced is sent to the catalytic converter 40 on the downstream side of the merging portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

(53) Incidentally, as shown in FIG. 4B, the dispersion face 33, by forming the upper side of the inclined surface 34 is obtuse with respect to the dispersion face 33 along the vertical direction, it is possible to guide the dispersion direction of the exhaust gas upward, it is possible to further reduce the flow in the catalytic direction.

Second Embodiment

(54) The exhaust gas control apparatus 1A of the second embodiment is, as shown in FIGS. 5 and 6, when the merging portion 30 is disposed at a position intermediate 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 of the first embodiment are denoted by the same reference numerals and will be described.

(55) In the exhaust gas control apparatus 1A of the second embodiment, the first exhaust passage 20a communicating with the first cylinder 10a is connected such that the distal end of the straight portion extending from the cylinder head 3 to the rear of the engine is inclined toward the merging portion 30 via the bent portion 21. In the second exhaust passage 20b communicating with the second cylinder 10b, a straight portion extending rearward of the engine 2 from the cylinder head 3 is connected downstream of the bent portion 21 of the first exhaust passage 20a. The third exhaust passage 20c communicating with the third cylinder 10c and the fourth exhaust passage 20d communicating with the fourth cylinder 10d are bent slightly toward the rear of the engine 2 and connected to the merging portion 30.

(56) The merging portion 30 is provided with an inflow port 31 to which the first exhaust passage 20a connecting the second exhaust passage 20b, the third exhaust passage 20c, and the fourth exhaust passage 20d are connected.

(57) In the merging portion 30, a dispersion face 33 is formed on an inner wall of the merging portion 30 opposed to the inflow port 31 connecting the first exhaust port 11a so as to three-dimensionally disperse the main flow of the exhaust gases linearly flowing from the inflow port 31 into the merging portion 30. Here, the dispersion face 33 is provided so as to be substantially perpendicular to the axis of the first exhaust port 11a. Further, the dispersion face 33 is provided so as to be substantially perpendicular to an axis along the outer wall of the bent portion 21 of the first exhaust port 11a.

(58) Further, in the merging portion 30, on the inner wall of the merging portion 30 opposed to the inflow port 31 connecting the third exhaust passage 20c and the fourth exhaust passage 20d, a dispersion face 33 is formed which three-dimensionally disperses the main flow of the exhaust gases flowing linearly from the inflow port 31 into the merging portion 30. Here, the dispersion face 33 is provided so as to be substantially perpendicular to the third exhaust passage 20c and the shaft of the fourth exhaust passage 20d. In FIG. 5, the dispersion face 33 is indicated by a straight line for ease of understanding.

(59) An air-fuel ratio sensor 50 for measuring an air-fuel ratio (A/F) of the exhaust gas flowing out of the respective cylinders 10a to 10d is provided at a portion where the main flow of the exhaust gas flowing into the merging portion 30 from the first exhaust passage 20a, the third exhaust passage 20c, and the fourth exhaust passage 20d in the merging portion 30 intersects with each other. As described above, by providing the air-fuel ratio sensor 50 at a portion where the main flow of the exhaust gas flowing into the merging portion 30 from the first exhaust passage 20a, the third exhaust passage 20c, and the fourth exhaust passage 20d intersects with each other, the flow velocity of the exhaust gas discharged from the respective cylinders 10a to 10d collides with the air-fuel ratio sensor 50 at a high speed, so that the 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 condition of the cylinder 10a to 10d is controlled based on the measurement value by the control unit.

(60) Next, in the exhaust gas control apparatus 1A of the second embodiment, the flow of the exhaust gas discharged from the respective cylinders 10a to 10d will be described referring to FIGS. 7A to 7D.

(61) As indicated by arrows in FIG. 7A, the main flow 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 flows into the inflow port 31 of the merging portion 30. The main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIG. 7A. This reduces the flow rate of the exhaust gas.

(62) As indicated by arrows in FIG. 7B, the main flow of the exhaust gas discharged from the second cylinder 10b flows through the second exhaust passage 20b connected to the second exhaust port 11b, flows downstream of the bent portion 21 of the first exhaust passage 20a, flows along the outer wall of the bent portion 21, and flows into the inflow port 31 of the merging portion 30. The main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIG. 7B. This reduces the flow rate of the exhaust gas.

(63) The main flow of the exhaust gas discharged from the third cylinder 10c flows through the third exhaust passage 20c connected to the third exhaust port 11c and flows into the inflow port 31 of the merging portion 30, as indicated by an arrow in FIG. 7C. The main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIG. 7C. This reduces the flow rate of the exhaust gas.

(64) As indicated by arrows in FIG. 7D, the main flow 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 and flows into the inflow port 31 of the merging portion 30. The main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIG. 7D. This reduces the flow rate of the exhaust gas.

(65) As described above, the main flow of the exhaust gases discharged from the respective 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 respective cylinders 10a to 10d, and flows into the merging portion 30, and the flow velocity decreases due to the dispersion caused by the collision with the dispersion face 33. Therefore, since the exhaust gas whose flow rate is reduced is sent to the catalytic converter 40 on the downstream side of the merging portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

(66) 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 part of the third and fourth exhaust passages 20c, 20d and the wall surface end surface 30a of the merging portion 30 substantially at right angles, it is possible to promote the dispersal of the exhaust gases. Further, as shown in FIG. 6, the dispersion face 33 is formed by the inclined surface 34 having an obtuse upper side, it is possible to guide the dispersion direction of the exhaust gas upward, it is possible to further reduce the flow in the catalyst direction.

(67) As described above, the main flow of the exhaust gases discharged from the respective 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 respective cylinders 10a to 10d, and flows into the merging portion 30, and the flow velocity decreases due to the dispersion caused by the collision with the dispersion face 33. Therefore, since the exhaust gas whose flow rate is reduced is sent to the catalytic converter 40 on the downstream side of the merging portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

Third Embodiment

(68) An exhaust gas control apparatus 1B of the third embodiment is, as shown in FIGS. 8, 9A, and 9B, when the merging portion 30 is arranged at an intermediate position of a third exhaust port 11c communicating with the third cylinder 10c with respect to the cylinder head 3 and the fourth exhaust port 11d communicating with the fourth cylinder 10d, and the exhaust passage 20B communicating with the respective exhaust ports 11a to 11d is formed integrally. In the third embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals and will be described.

(69) In the exhaust gas control apparatus 1B of the third embodiment, the exhaust passage 20B, as shown in FIGS. 9A and 9B, has an opening 23 communicating with 11d from the respective exhaust ports 11a, the outer wall of the first exhaust port 11a is connected to the merging portion 30 with the leading end side of the straight portion extending rearward of the engine 2 from the cylinder head 3 with an enlarged inclination toward the merging portion 30 via the bent portion 21. Further, in the exhaust passage 20B, an outer wall on the fourth exhaust port 11d side is gently bent at a distal end side of a straight portion extending rearward of the engine 2 from the cylinder head 3, and is connected to the merging portion 30.

(70) At this time, the exhaust gases discharged from the first cylinder 10a, second cylinder 10b and the third cylinder 10c collide with the inclined wall surface 24 inclined from the bent portion 21 toward the merging portion 30 in the exhaust passage 20B. By forming in this way, the main flow of the exhaust gas discharged from the first cylinder 10a, second cylinder 10b and the third cylinder 10c collides with the inclined wall surface 24 flows into the merging portion 30 along the inclined wall surface 24.

(71) The merging portion 30 is provided with an inflow port 31 that connects the exhaust passage 20B, and a dispersion face 33 that three-dimensionally disperses the main flow of the exhaust gas linearly flowing from the inflow port 31 into the merging portion 30 is formed on the inner wall of the merging portion 30 that faces the inflow port 31. In this case, the dispersion face 33 is provided so as to be substantially orthogonal to the axis along the inclined wall surface 24. Further, the dispersion face 33 is formed with a dispersion face 33 that three-dimensionally disperses the main flow of the exhaust gas flowing linearly from the inflow port 31 into the merging portion 30 on the inner wall of the merging portion 30 that faces the inflow port 31 into which the exhaust gas discharged from the fourth cylinder 10d flows.

(72) In the merging portion 30, an air-fuel ratio sensor 50 that measures an air-fuel ratio (A/F) of the exhaust gas flowing out of the respective cylinders 10a to 10d is provided at a portion where the main flow of the exhaust gas flowing into the merging portion 30 along the inclined wall surface 24 and the main flow of the exhaust gas discharged from the fourth cylinder 10d and flowing into the merging portion 30 intersect with each other. As described above, by providing the air-fuel ratio sensor 50 at a portion where the main flow of the exhaust gas flowing into the merging portion 30 along the inclined wall surface 24 and the main flow of the exhaust gas discharged from the fourth cylinder 10d and flowing into the merging portion 30 intersect with each other, the flow rate of the exhaust gas discharged from the respective cylinders 10a to 10d collides with the air-fuel ratio sensor 50 at a high speed, so that the sensor responsiveness can be secured. The measurement data detected by the air-fuel ratio sensor 50 is transmitted to a control unit (not shown), and the combustion condition of the cylinder 10a to 10d is controlled based on the measurement value by the control unit.

(73) Next, in the exhaust gas control apparatus 1B of the third embodiment, the flow of the exhaust gas discharged from the respective cylinders 10a to 10d will be described referring to FIGS. 9A and 9B.

(74) 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 a solid arrow in FIG. 9A, and then flows along the inclined wall surface 24 and flows into the inflow port 31 of the merging portion 30. When the flow along the inclined wall surface 24 flows into the merging portion 30, the flow becomes a jet for rapid expansion, and the flow of the exhaust gas stagnating toward the outer wall of the exhaust passage 20B is separated from the wall, and the surrounding stationary gas is entrained and diffused. Then, the main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIG. 9A. This reduces the flow rate of the exhaust gas.

(75) 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 a broken line arrow in FIG. 9A, and then flows along the inclined wall surface 24 and flows into the inflow port 31 of the merging portion 30. When the flow along the inclined wall surface 24 flows into the merging portion 30, the flow becomes a jet for rapid expansion, and the flow of the exhaust gas stagnating toward the outer wall of the exhaust passage 20B is separated from the wall, and the surrounding stationary gas is entrained and diffused. Then, the main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIG. 9A. This reduces the flow rate of the exhaust gas.

(76) 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 a dashed-dotted arrow in 9A of the drawing, and then flows along the inclined wall surface 24 and flows into the inflow port 31 of the merging portion 30. When the flow along the inclined wall surface 24 flows into the merging portion 30, the flow becomes a jet for rapid expansion, and the flow of the exhaust gas stagnating toward the outer wall of the exhaust passage 20B is separated from the wall, and the surrounding stationary gas is entrained and diffused. Then, the main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIG. 9A. This reduces the flow rate of the exhaust gas.

(77) The main flow of the exhaust gas discharged from the fourth cylinder 10d flows into the inflow port 31 of the exhaust passage 20B connected to the fourth exhaust port 11d as indicated by an arrow in FIG. 9B. The main flow of the exhaust gas that has flowed linearly into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIG. 9B. This reduces the flow rate of the exhaust gas.

(78) As described above, the main flow 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 flows into the inflow port 31 of the merging portion 30, collides with the dispersion face 33 opposed to the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion. The dispersion caused by the collision with the dispersion face 33 lowers the flow velocity. Further, the main flow of the exhaust gas discharged from the fourth cylinder 10d flows into the inflow port 31 of the merging portion 30 to become a jet, and the flow of the exhaust gas stagnating on the outer wall of the exhaust passage 20B is separated from the wall, and the surrounding stationary gas is entrained and diffused. Further, the main flow of the exhaust gas that has flowed into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion. Therefore, since the exhaust gas whose flow rate is reduced is sent to the catalytic converter 40 on the downstream side of the merging portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

Fourth Embodiment

(79) As shown in FIGS. 10 and 11, the exhaust gas control apparatus 1C of the fourth embodiment is when the exhaust passage 20C communicating with the collective exhaust port 12 in which 11d are collected from the exhaust port 11a communicating with 10d from the respective cylinders 10a is connected to the merging portion 30. Here, 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 of the first embodiment are denoted by the same reference numerals and will be described.

(80) In the exhaust gas control apparatus 1C of the fourth embodiment, the merging portion 30 is disposed at an intermediate position between the second exhaust port 11b communicating with the second cylinder 10b and the third exhaust port 11c communicating with the third cylinder 10c with respect to the cylinder head 3 via the exhaust passage 20C communicating with the discharge port 13 of the collective exhaust port 12.

(81) The merging portion 30 is provided with an inflow port 31 that connects the exhaust passage 20C, and the connecting portion with the exhaust passage 20C is provided with a diffusion portion 32C that promotes the jet flow of the main flow of the exhaust gas flowing into the merging portion 30. Here, the diffusion portion 32C is formed by a step between the exhaust passage 20C and the connecting portion of the merging portion 30.

(82) Further, the merging portion 30, the inner wall of the merging portion 30 facing the inflow port 31, the main flow of the exhaust gas flowing linearly into the merging portion 30 from the inflow port 31 along the wall surface 25 of the exhaust passage 20C is three-dimensionally dispersed dispersion face 33 is formed.

(83) In the merging portion 30, an air-fuel ratio sensor 50 for measuring an air-fuel ratio (A/F) of the exhaust gas flowing out of the respective cylinders 10a to 10d is provided at a portion where the main flow of the exhaust gas discharged from the respective cylinders 10a to 10d and flowing into the merging portion 30 along the wall surface 25 of the exhaust passage 20C intersects with each other as in the first to third embodiments.

(84) Next, in the exhaust gas control apparatus 1C of the fourth embodiment, the flow of the exhaust gas discharged from the respective cylinders 10a to 10d will be described referring to FIGS. 12 and 13. Since the first cylinder 10a, fourth cylinder 10d and the second cylinder 10b, third cylinder 10c are symmetrical, the first cylinder 10a and the second cylinder 10b will be described here.

(85) As indicated by arrows in FIG. 12, the exhaust gas discharged from the first cylinder 10a is largely bent and flows into the merging 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 flow of the exhaust gas flowing into the merging portion 30 becomes a jet by the diffusion portion 32C formed by the step between the exhaust passage 20C and the connecting portion of the merging portion 30, and separates the flow of the exhaust gas stagnating toward the wall of the exhaust passage 20C from the wall, and diffuses by entraining the surrounding stationary gas. Then, the main flow of the exhaust gas linearly flowing into the merging portion 30 collides with the dispersion face 33 opposed to the inflow port 31, and is three-dimensionally dispersed with respect to the collision portion as shown in FIG. 13. This reduces the flow rate of the exhaust gas.

(86) The exhaust gas discharged from the second cylinder 10b flows into the merging portion 30 substantially linearly along the wall surface 25 of the exhaust passage 20C through the discharge port 13 of the collective exhaust port 12. The main flow of the exhaust gas flowing into the merging portion 30 becomes a jet by the diffusion portion 32C formed by the step between the exhaust passage 20C and the connecting portion of the merging portion 30, and separates the flow of the exhaust gas stagnating toward the wall of the exhaust passage 20C from the wall, and diffuses by entraining the surrounding stationary gas. Then, the main flow of the exhaust gas linearly flowing into the merging portion 30 collides with the dispersion face 33 opposed to the inflow port 31, and is three-dimensionally dispersed with respect to the collision portion as shown in FIG. 13. This reduces the flow rate of the exhaust gas.

(87) As described above, the main flow of the exhaust gas discharged from the first to fourth cylinders 10a to 10d flows along the wall surface 25 of the exhaust passage 20C and flows into the inflow port 31 of the merging portion 30 to become a jet flow, and the flow of the exhaust gas stagnating on the outer wall of the exhaust passage 20C is separated from the wall, and the surrounding stationary gas is entrained and diffused. Further, the main flow of the exhaust gas that has flowed into the merging portion 30 collides with the dispersion face 33 that faces the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion. Therefore, since the exhaust gas whose flow rate is reduced is sent to the catalytic converter 40 on the downstream side of the merging portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

(88) In the exhaust gas control apparatus 1C of the fourth embodiment, as shown in FIG. 11, the dispersion face 33 is formed by the inclined surface 34 whose upper side is obtuse, so that the dispersion direction of the exhaust gas can be guided upward, so that the flow in the catalytic direction can be further reduced.

(89) Further, in the exhaust gas control apparatus 1C of the fourth embodiment, as shown in FIG. 14, by making the angle between the lower surface 20e of the inlet part of the exhaust passage 20C and the wall surface end surface 30a of the merging portion 30 substantially at right angles, it is possible to promote the dispersal of the exhaust gas.

Fifth Embodiment

(90) The exhaust gas control apparatus 1D of the fifth embodiment has, as shown in FIGS. 15 to 17, a manifold exhaust passage 20D in which a wall 25D is provided on an extension line of each central axis of 20d from each exhaust passage 20a communicating with 10d from each cylinder 10a, and the manifold exhaust passage 20D is connected to the merging portion 30. In the fifth embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals and will be described.

(91) The wall 25D provided in the manifold exhaust passage 20D is formed perpendicularly to the central axis of each of the respective exhaust passages 20a to 20d or the extension line of the wall surface.

(92) In the exhaust gas control apparatus 1D of the fifth embodiment, the merging portion 30 is disposed on the fourth cylinder 10d side with respect to the cylinder head 3, and is connected to the merging portion 30 via an elbow portion 26 in which a downstream-side end of the manifold exhaust passage 20D extending through the bent portion 21 in the first exhaust passage 20a is bent. The downstream-side ends of the second to fourth exhaust passages 20b to 20d are connected to the manifold exhaust passage 20D.

(93) The merging portion 30 connected to the downstream-side of the manifold exhaust passage 20D is provided with a diffusion portion 32D that promotes the jet flow of the main flow of the exhaust gases flowing into the merging portion 30. Here, the diffusion portion 32D is formed by a step in a connecting portion between the manifold exhaust passage 20D (specifically, the elbow portion 26) and the merging portion 30. The diffusion portion may be formed by projecting the elbow portion 26 into the merging portion 30.

(94) Further, the merging portion 30, the inner wall of the merging portion 30 facing the inflow port 31 connecting the manifold exhaust passage 20D, the main flow of the exhaust gas flowing linearly into the merging portion 30 from the inflow port 31 is three-dimensionally dispersion face 33 is formed. Here, the dispersion face 33 is provided so as to be substantially perpendicular to the axis of the manifold exhaust passage 20D. Further, the dispersion face 33 is provided so as to be substantially perpendicular to the axial 26a of the elbow portion 26 of the manifold exhaust passage 20D. The dispersion face 33 may be formed by an inclined surface having an obtuse upper side perpendicular to the axis of the manifold exhaust passage 20D.

(95) Next, in the exhaust gas control apparatus 1D of the fifth embodiment, the flow of the exhaust gas discharged from the respective cylinders 10a to 10d will be described referring to FIGS. 15, 18, and 19.

(96) Exhaust gases discharged from the respective cylinders 10a to 10d flow through the respective cylinders 10a to 10d as indicated by arrows in FIG. 15, collide with and are dispersed in the wall 25D of the manifold exhaust passage 20D, flow through the manifold exhaust passage 20D along the wall 25D, and flow into the merging portion 30. The main flow of the exhaust gas flowing into the merging portion 30 becomes a jet by the diffusion portion 32D formed by the step of the connecting portion of the merging portion 30 and the manifold exhaust passage 20D, and separates the flow of the exhaust gas stagnating toward the wall of the manifold exhaust passage 20D from the wall, and diffuses by entraining the surrounding stationary gas. Then, the main flow of the exhaust gas linearly flowing into the merging portion 30 collides with the dispersion face 33 facing the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion as shown in FIGS. 18 and 19. This reduces the flow rate of the exhaust gas.

(97) As described above, the exhaust gas discharged from the first to fourth cylinders 10a to 10d flows through the respective cylinders 10a to 10d and collides with 20D wall-wall 25D of the manifold exhaust passage to be dispersed, thereby suppressing variations in the distribution of the exhaust gas discharged from the respective cylinders 10a to 10d. Then, the exhaust gas whose distribution variation is suppressed flows along the wall 25D of the manifold exhaust passage 20D, flows into the inflow port 31 of the merging portion 30, becomes a jet, and separates the flow of the exhaust gas stagnant on the wall 25D of the manifold exhaust passage 20D from the wall 25D, and diffuses by entraining the surrounding stationary gas. Further, the main flow of the exhaust gas flowing into the merging portion 30 collides with the dispersion face 33 opposed to the inflow port 31, and is three-dimensionally dispersed with respect to the colliding portion. Therefore, since the exhaust gas whose flow rate is reduced is sent to the catalytic converter 40 on the downstream side of the merging portion 30, the flow in the catalyst direction can be reduced, and the purification characteristics of the catalyst can be improved.

(98) In the exhaust gas control apparatus 1D of the fifth embodiment, the dispersion face 33 of the merging portion 30 is formed by an inclined surface (not shown) whose upper side is obtuse, so that the dispersion direction of the exhaust gas can be guided upward, so that the flow in the catalytic direction can be further reduced.

(99) In the above embodiment, the engine has been described in the case of four cylinders, but the present disclosure is not limited thereto, and the engine may be a plurality of cylinders other than four cylinders.