JP6524700B2 - Internal combustion engine exhaust system - Google Patents

Description

  The present invention relates to an exhaust system of an internal combustion engine. In particular, it is suitably used in an exhaust system of an internal combustion engine having a catalyst for purifying exhaust gas.

  A vehicle provided with an internal combustion engine includes an exhaust system for discharging exhaust gas from the internal combustion engine to the outside. The exhaust system has a catalytic converter (hereinafter referred to as a catalyst) for purifying exhaust gas. Here, it is necessary to reach the activation temperature in order for the catalyst to exert its purification function. In recent years, exhaust gas regulations become stricter, and it is required to improve the purification performance of the catalyst by setting the catalyst to the activation temperature early from the start of the internal combustion engine.

  In Patent Document 1, a first pipe for introducing exhaust gas from an exhaust port of an engine to an upstream catalyst, a second pipe for connecting the upstream catalyst and the downstream catalyst, and a downstream catalyst An exhaust system is disclosed having an exhaust pipe consisting of an extending third pipe. In the exhaust system of Patent Document 1, exhaust gas is purified by the two catalysts immediately after the start of the engine. Further, in the exhaust system of Patent Document 1, the engine output can be improved by attaching a resonator for attenuating the reflected wave and the negative pressure wave to the second pipe.

JP, 2008-151093, A

  However, in the exhaust system of Patent Document 1, although the exhaust gas is purified by the two catalysts immediately after the start of the engine, no measures against the heat radiation from the exhaust pipe itself are taken. Therefore, in the configuration of the exhaust system of Patent Document 1, there is a problem that the heat is dissipated from the exhaust pipe, and the effect of early reaching the catalyst to the activation temperature is not sufficient.

  The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to improve the purification performance of a catalyst by causing the catalyst to reach the activation temperature early.

The exhaust system for an internal combustion engine according to the present invention comprises an exhaust pipe extending toward the rear of the vehicle body via a curved portion after extending toward the front of the vehicle body from an exhaust port provided in the internal combustion engine, and the exhaust pipe An exhaust system for an internal combustion engine, comprising: a catalyst that purifies the exhaust gas to be induced, wherein the entire curved portion located at the front of the exhaust pipe is covered along a part of the exhaust pipe. possess an outer wall portion, the curved portion, in the space inside the outer wall portion, so that space is provided in front of the vehicle body, are arranged unevenly inside the vehicle body in the vehicle width direction, after the outer wall of the exhaust pipe The exposed portion exposed from the end is characterized in that it is disposed on the inner side of the vehicle body than the outer surface of the outer wall in the vehicle width direction .

  According to the present invention, since the heat retaining property of the exhaust pipe can be improved, the exhaust gas can be prevented from being cooled in the exhaust pipe, and can reach the catalyst at high temperature. Therefore, the catalyst can reach the activation temperature early, and the purification performance of the catalyst can be improved.

Fig. 2 is a right side view of the motorcycle. It is a right side view showing a part of an engine and an exhaust system. It is a front view showing a part of an engine and an exhaust system. It is a top view which shows an engine and a part of exhaust system. It is a top view which shows the structure of a part of exhaust apparatus. It is a right side which shows the structure of a part of exhaust apparatus. It is sectional drawing of the II line shown in FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an exhaust system for an internal combustion engine according to the present invention will be described below based on the drawings. Here, the case where the exhaust system of an internal combustion engine is applied to a motorcycle will be described.
FIG. 1 is a right side view of the motorcycle 100. FIG. First, the overall configuration of the motorcycle 100 will be described with reference to FIG. In each of the drawings including FIG. 1 in the following description, the front of the vehicle body is indicated by an arrow Fr and the rear of the vehicle body is indicated by an arrow Rr, and the right side of the vehicle body is indicated by an arrow R and the left side of the vehicle body is indicated by an arrow L. It shows each.

  The motorcycle 100 of FIG. 1 is typically for so-called off-road use. A steering head pipe 101 is disposed at an upper portion in front of the vehicle body. A steering shaft (not shown) is rotatably inserted into the steering head pipe 101. A steering wheel 102 is coupled to an upper end of the steering shaft, and a front fork 103 is attached to the steering shaft. A front wheel 104 which is a steering wheel is rotatably supported at the lower end of the front fork 103.

  Further, from the steering head pipe 101, a pair of left and right main frames 105 extends obliquely downward toward the rear of the vehicle body, and a down tube 106 extends substantially vertically downward. The down tube 106 branches left and right as a lower frame 107 in the vicinity of the lower portion. The pair of lower frames 107 extend downward and are then bent at a substantially right angle toward the rear of the vehicle body. The rear ends of the pair of lower frames 107 are connected to the rear ends of the main frame 105 via the pair of left and right body frames 108.

  In a space surrounded by the main frame 105, the down tube 106, the lower frame 107, and the body frame 108, an engine 10 is mounted as an internal combustion engine. A fuel tank 109 is disposed above the engine 10. The fuel supply port of the fuel tank 109 is plugged by a cap 110. A seat 111 is disposed behind the fuel tank 109.

  A front end portion of a rear swing arm 112 is supported by a pivot shaft 113 so as to be vertically swingable at a pair of left and right body frames 108 provided at a lower portion substantially in the longitudinal center of the vehicle body. A rear wheel 114, which is a driving wheel, is rotatably supported at the rear end of the rear swing arm 112. The rear swing arm 112 is suspended from the vehicle body via a link mechanism 115 and a shock absorber 116 connected thereto.

  A fuel pump unit (not shown) is disposed in the fuel tank 109. The fuel pump unit supplies the engine 10 with fuel. On the other hand, an air cleaner box 117 is disposed above the shock absorber 116. The air cleaner box 117 and the engine 10 are connected via an intake pipe (not shown). The intake pipe is connected to an intake port 16 provided in a cylinder head 14 of the engine 10 described later, and a throttle body (not shown) is disposed in the middle of the intake pipe. The throttle body has a fuel injector, and a predetermined amount of fuel is supplied to the fuel injector from the fuel pump unit at a predetermined timing.

  An exhaust device 20 is connected to an exhaust port 17 provided in a cylinder head 14 of the engine 10 described later. The exhaust system 20 exhausts the exhaust gas burned by the engine 10 to the outside. The exhaust system 20 includes an exhaust pipe 21, a muffler 34, a catalyst 35, and a surrounding pipe 30 as an outer wall portion. The exhaust pipe 21 guides the exhaust gas from the exhaust port 17 of the engine 10 to the muffler 34. The muffler 34 has a plurality of expansion chambers (not shown) formed therein, which can reduce exhaust noise. The catalyst 35 is disposed in the muffler 34 to purify the exhaust gas. The configurations of the exhaust pipe 21 and the surrounding pipe 30 will be described later.

Next, the configuration of the engine 10 will be described. The engine 10 of this embodiment uses a water-cooled four-stroke single-cylinder engine. 2 to 4 are a right side view, a front view, and a plan view showing a part of the engine 10 and the exhaust system 20.
The engine 10 includes a crankcase 11 rotatably supporting a crankshaft 12 and accommodated, a cylinder block 13 accommodating a piston (not shown) so as to be capable of moving up and down, a cylinder head 14 accommodating a valve gear, and a cylinder head A cylinder head cover 15 that covers 14 is connected vertically along the upper and lower sides. The cylinder axis Cy of the cylinder block 13 is slightly forwardly inclined (the inclination angle is approximately 15 °) with respect to the vertical direction. The cylinder axis Cy of the cylinder block 13 is orthogonal to the crankshaft Cr of the crankshaft 12.

  The cylinder head 14 is provided with an intake port 16 on the rear surface and an exhaust port 17 on the front surface. The intake port 16 opens rearward and slightly upward of the vehicle body. The exhaust port 17 is open toward the front of the vehicle body and slightly downward and to the right. An exhaust pipe 21 is connected to the exhaust port 17.

Next, the configuration of the exhaust system 20 will be described.
FIG. 5 is a plan view showing the configuration of a part of the exhaust system 20. As shown in FIG. FIG. 5 shows a state in which the surrounding pipe 30 is cut in the horizontal direction. FIG. 6 is a right side view showing the configuration of part of the exhaust system 20. As shown in FIG. In FIG. 6, the surrounding pipe 30 is shown by a two-dot chain line. FIG. 7 is a cross-sectional view taken along a line II shown in FIG.
In the present embodiment, the exhaust pipe 21 and the surrounding pipe 30 are used to configure the catalyst 35 to reach the activation temperature early. Hereinafter, the configurations of the exhaust pipe 21 and the surrounding pipe 30 will be specifically described.

  First, the exhaust pipe 21 will be described. The exhaust pipe 21 extends from the exhaust port 17 toward the front of the vehicle body and then curves and extends toward the rear of the vehicle body. Here, the exhaust pipe 21 is integrally formed, but for ease of explanation, as shown in FIGS. 5 and 6, the exhaust pipe 21 is divided into a front portion 22, a middle portion 23, and a rear portion 24. explain.

The front portion 22 ranges from a vertical plane F1 passing through the front end of the exhaust pipe 21 parallel to the left-right direction of the vehicle to a vertical plane F2 parallel to the left-right direction of the vehicle passing the rear end of the connecting portion 26 connected to the exhaust port 17 Shall be said.
The intermediate portion 23 refers to a range from the vertical plane F2 to a vertical plane F3 parallel to the left-right direction of the vehicle body passing a portion where the exhaust pipe 21 starts straight extension straight toward the rear of the vehicle body.
The rear portion 24 refers to a range from the vertical plane F3 to the rear end of the exhaust pipe 21 connected to the muffler 34.

The front portion 22 constitutes a generally curved bend 25. A connection 26 for connecting to the exhaust port 17 using a bolt is provided at the end of the bending portion 25. As shown in FIG. 5, in a plan view, the curved portion 25 curves so as to turn to the right of the engine 10 while maintaining a substantially constant curvature radius. Further, as shown in FIG. 6, the curved portion 25 extends toward the intermediate portion 23 so as to be gradually biased downward as viewed in a side view. The length of the curved portion 25 can be shortened by the amount that the exhaust port 17 opens slightly to the right.
The bypass pipe 27 is joined to the curved portion 25 by welding. The bypass pipe 27 is coupled to a position on the vehicle body outer side of the curved portion 25, and its axis (the alternate long and short dash line La shown in FIG. 7) is substantially radial from the center of the radius of curvature of the curved portion 25; It is directed upward. The bypass pipe 27 brings the space 28 in the exhaust pipe 21 into communication with the space 32 in the surrounding pipe 30, which will be described later.

The intermediate portion 23 is formed toward the rear of the vehicle body via the side of the cylinder block 13 and the cylinder head 14 of the engine 10 while being slightly bent in the vehicle left-right direction and the vehicle vertical direction. Specifically, as shown in FIG. 5, in a plan view, the intermediate portion 23 gradually extends toward the rear portion 24 while gradually shifting to the inner side of the vehicle body, that is, to the left side of the vehicle body. Further, as shown in FIG. 6, when viewed from the side, the intermediate portion 23 gradually extends upward and then gradually extends downward and extends toward the rear portion 24. The height of the middle portion 23 located at the highest position substantially coincides with the height at which the bending portion 25 is located at the highest position.
The rear portion 24 is formed toward the muffler 34 after extending linearly to the rear of the vehicle body by a certain length.

Next, the surrounding pipe 30 will be described. The surrounding pipe 30 covers at least the outer periphery of the front portion 22 of the exhaust pipe 21 in a state along a part of the exhaust pipe 21. Specifically, the surrounding pipe 30 continuously and integrally covers from the front portion 22 of the exhaust pipe 21 to the uppermost portion of the intermediate portion 23. Thus, a portion of the exhaust pipe 21 covered by the surrounding pipe 30 is disposed in the surrounding pipe 30. On the other hand, a part of the exhaust pipe 21 not covered by the surrounding pipe 30 is exposed to the outside. Here, a portion of the exhaust pipe 21 exposed to the outside is referred to as an exposed portion 29. As shown in FIG. 4, the exposed portion 29 is disposed on the vehicle body inner side in the vehicle body width direction with respect to the surface (two-dot chain line Lt shown in FIG. 4) on the vehicle body outer side of the surrounding pipe 30.
In addition, the surrounding pipe 30 is divided up and down, and it is comprised by welding by the boundary part 31 so that the exhaust pipe 21 may be pinched from the upper and lower sides. In addition, the surrounding pipe 30 is joined by welding one end and the other end to the exhaust pipe 21. Therefore, the space 32 in the surrounding pipe 30 is closed by the exhaust pipe 21. The exhaust pipe 21 and the surrounding pipe 30 are preferably made of the same material (for example, stainless steel plate) so that they can be easily welded.

Since the surrounding pipe 30 is formed along the front part 22 and the middle part 23 of the exhaust pipe 21, it wraps around the right side of the engine 10 like the exhaust pipe 21, and the sides of the cylinder block 13 and the cylinder head 14 It is formed to go through.
Here, the surrounding pipe 30 is curved so as to expand to the outside of the vehicle body more largely than the exhaust pipe 21. Specifically, as shown in FIG. 7, the distance L1 between the surface of the exhaust pipe 21 on the outer side of the vehicle body and the surface of the surrounding pipe 30 is the surface of the exhaust pipe 21 on the inner side of the vehicle body and the surface of the surrounding pipe 30 And the distance L2 between In other words, the exhaust pipe 21 is disposed inward of the vehicle body in the space 32 in the surrounding pipe 30.

  In addition, although the height of the upper surface of the surrounding pipe 30 does not substantially change from one end to the other end, the height of the lower surface slightly bulges downward in accordance with the downward bias of the exhaust pipe 21 There is. In other words, the exhaust pipe 21 is biased downward in the space 32 in the surrounding pipe 30.

  Here, the space 32 in the surrounding pipe 30 is communicated with the space 28 in the exhaust pipe 21 by the bypass pipe 27 described above. Therefore, in order for the exhaust gas guided to the exhaust pipe 21 to enter the surrounding pipe 30, the surrounding pipe 30 can function as a resonator. Here, the bypass pipe 27 can adjust the effect of the resonator by changing the pipe diameter and the pipe length (length Lp shown in FIG. 7). Here, since the axis La of the bypass pipe 27 is directed toward the outside of the vehicle body in which the distance to the surrounding pipe 30 is long, the pipe length Lp of the bypass pipe 27 can be easily adjusted. . Therefore, since it is not necessary to change the shape of the surrounding pipe 30 according to the characteristic of the engine 10 or the vehicle body, it is possible to achieve commonality of parts and reduction of the development process.

In the exhaust system 20 configured as described above, the exhaust gas burned by the engine 10 is purified by the catalyst 35 from the exhaust port 17 through the exhaust pipe 21 and the exhaust noise is reduced by the muffler 34 to the outside Exhausted.
At this time, since the surrounding pipe 30 covers the outer periphery of the exhaust pipe 21, the air in the space 32 of the surrounding pipe 30 can improve the heat retention of the exhaust pipe 21. Therefore, the exhaust gas exhausted from the engine 10 is suppressed from being cooled in the exhaust pipe 21 and reaches the catalyst 35 at high temperature. Therefore, the catalyst 35 can quickly reach an activation temperature at which the purification action can be exhibited from the start of the engine 10, and the purification performance of the catalyst 35 can be improved.
In addition, since the surrounding pipe 30 covers at least the front portion 22 of the exhaust pipe 21, it is possible to prevent the exhaust pipe 21 from being overcooled by the traveling wind from the front of the vehicle body, and the exhaust gas reaches the catalyst 35 with high temperature. It can be done.

  Further, the curved portion 25 of the exhaust pipe 21 has a large projected area and is easily hit by the traveling wind when viewed from the front of the vehicle body, and therefore, is the most easily cooled position. In the present embodiment, the surrounding pipe 30 covers the curved portion 25 of the exhaust pipe 21 to prevent the exhaust pipe 21 from being overcooled by the traveling wind from the front of the vehicle body, and the catalyst 35 keeps the exhaust gas at a high temperature. Can be reached.

  In addition, the exhaust pipe 21 is disposed inward of the vehicle body in a space 32 in the surrounding pipe 30. Therefore, the distance between the exhaust pipe 21 and the outer surface of the surrounding pipe 30 which is likely to be cooled by the traveling wind can be increased. Therefore, the exhaust pipe 21 can suppress the heat conduction with the surrounding pipe 30, and can make the exhaust gas reach the catalyst 35 as it is at a high temperature.

  Further, the exposed portion 29 of the exhaust pipe 21 exposed from the surrounding pipe 30 is disposed more inward of the outer surface of the surrounding pipe 30 than the surface of the surrounding pipe 30 in the vehicle width direction. Therefore, when viewed from the front of the vehicle body, the exposed portion 29 is disposed at a position hidden by the surrounding pipe 30, so that the traveling wind does not easily hit the exposed portion 29. Therefore, cooling of the exposed portion 29 of the exhaust pipe 21 by the traveling wind from the front of the vehicle body can be suppressed.

Further, the surrounding pipe 30 extends to the side of the cylinder block 13 or the cylinder head 14 of the engine 10. Therefore, the length of the exposed portion 29 of the exhaust pipe 21 can be shortened, and the heat radiation from the exhaust pipe 21 can be suppressed.
In addition, since the exhaust pipe 21 has the bypass pipe 27 that brings the space 28 in the exhaust pipe 21 into communication with the space 32 in the surrounding pipe 30, the surrounding pipe 30 can function as a resonator. By making the surrounding pipe 30 function as a resonator, sufficient output can be obtained even if the length of the exhaust pipe 21 is short. Can be implemented. Here, the output characteristic improvement means that the output in the low engine speed range does not decrease. Further, by causing the surrounding pipe 30 to function as a resonator, there is no need for a bracket for fixing the resonator, and there is no risk of dropping off due to vibration.

As mentioned above, although this invention was demonstrated using embodiment mentioned above, this invention is not limited only to embodiment mentioned above, A change etc. are possible within the scope of the present invention.
Although the case where exhaust system 20 of an internal-combustion engine was applied to motorcycle 100 was explained by the embodiment mentioned above, it is not restricted to this case, and may be applied to a three-wheeled motor vehicle or a four-wheeled vehicle.
Although the case where a water-cooled single-cylinder engine is applied to the engine 10 has been described in the above-described embodiment, the present invention is not limited to this case, and a multi-cylinder engine may be applied. In this case, each exhaust pipe connected to each exhaust port is preferably covered by a surrounding pipe.

  In the embodiment described above, the exhaust pipe 21 extends from the exhaust port 17 toward the front of the vehicle body and then bends, and the exhaust pipe 21 extends toward the rear of the vehicle body via the side of the engine 10, This is not limited to this case. For example, the exhaust pipe may extend from the exhaust port 17 toward the front of the vehicle body and then be curved, and may extend toward the rear of the vehicle body below the engine 10. In this case, it is possible to prevent the overcooling of the exhaust pipe due to the traveling wind from the front of the vehicle body by bulging the surrounding pipe covering the outer periphery of the exhaust pipe downward.

  Although the cylinder head 14 is provided with the intake port 16 and the exhaust port 17 in the embodiment described above, the present invention is not limited to this case, and the intake port 16 and the exhaust port 17 are provided in the cylinder block 13. It is also good.

  Reference Signs List 10: engine 11: crank case 13: cylinder block 14: cylinder head 15: cylinder head cover 21: exhaust pipe 22: front 23: middle portion 24: rear portion 25: curved portion 26: connection portion 27: pie bus pipe 28: space 29: Exposed part 30: Surrounding pipe (outer wall part) 31: Welded part 32: Space 34: Muffler 35: Catalyst 100: Motorcycle

Claims (6)

An exhaust pipe extending toward the rear of the vehicle body via a curved portion after extending toward the front of the vehicle body from an exhaust port provided in the internal combustion engine;
An exhaust system for an internal combustion engine, comprising: a catalyst for purifying exhaust gas induced by the exhaust pipe;
Wherein in a state along a portion of the exhaust pipe, it has a outer wall that covers the entire curved portion located on the front of the exhaust pipe,
The curved portion is disposed inward of the vehicle body in the vehicle body width direction so as to provide a space in front of the vehicle body in the space in the outer wall portion,
An exhaust system for an internal combustion engine , wherein an exposed portion of the exhaust pipe exposed from a rear end of the outer wall portion is disposed more inward of a vehicle body than a surface of the outer wall portion outside the vehicle body in the vehicle body width direction . The distance between the surface of the exhaust pipe on the outer side of the vehicle body and the outer wall portion is larger than the distance between the surface of the exhaust pipe on the inner side of the vehicle body and the outer wall portion. Exhaust system for internal combustion engines. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein the outer wall portion integrally covers the portion of the exhaust pipe up to the uppermost position continuously with the curved portion. The exhaust system for an internal combustion engine according to any one of claims 1 to 3 , wherein the outer wall portion extends to a side of a cylinder block or a cylinder head of the internal combustion engine. The exhaust system for an internal combustion engine according to any one of claims 1 to 4 , wherein the exhaust pipe has a bypass pipe that brings the space in the exhaust pipe into communication with the space in the outer wall. The outer wall is a surrounding pipe,
The space in the surrounding pipe is formed wider as it goes from the one end and the other end of the surrounding pipe to the side of the bypass pipe in a plan view. Exhaust system for internal combustion engines.

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