JPH10317954A - Exhaust manifold for 3-cylinder engine - Google Patents

Abstract

(57) [Summary] [Object] To provide an exhaust manifold of a three-cylinder engine capable of maintaining the output of each cylinder of the three-cylinder engine evenly. In an exhaust manifold 20 of a three-cylinder engine in which exhaust pipes 22 and 23 of both cylinders are integrated with an exhaust pipe 21 of a central cylinder at a central part in a crankshaft direction, the exhaust manifold 20 of the central cylinder is viewed in the crankshaft direction. Exhaust pipe 21
From the exhaust pipes 22 and 23 of the other two-sided cylinders by e outside in the width direction. According to the present invention, the length from the exhaust port in the exhaust pipe 21 of the central cylinder to the gathering point can be made equal to that in the exhaust pipes 22 and 23 of the other two-sided cylinders. Each of the exhaust pipes 21 to 2 is discharged to the manifold 20.
The exhaust volume up to the collection point of the exhaust gas flowing through the inside 3 is substantially the same in the central cylinder and the other two-sided cylinders, and the output of each cylinder in the engine is substantially equal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust manifold for a three-cylinder engine.

[0002]

2. Description of the Related Art For example, an exhaust manifold connected to an exhaust system of a three-cylinder engine mounted on a watercraft is constructed by integrating exhaust pipes of both cylinders into an exhaust pipe of a central cylinder, and each cylinder of the engine is provided with an exhaust pipe. The exhaust gas generated by the combustion of the air-fuel mixture at the center is collected and discharged at the center.

In order to maintain a good output balance by equalizing the output of each cylinder in a three-cylinder engine and to facilitate the setting of the carburetor, exhaust gas discharged from each exhaust port to an exhaust manifold is required. Must be equal for each cylinder.

Therefore, when the inside diameter of each exhaust pipe of the exhaust manifold is the same, the length from each exhaust port of the engine to the gathering point of the exhaust manifold must be set to be substantially equal.

[0005]

However, the exhaust manifold of the conventional three-cylinder engine is constructed by integrally integrating the exhaust pipes of both cylinders with the exhaust pipe of the central cylinder as described above. The length of the cylinder exhaust pipe was longer than that of the central cylinder exhaust pipe, making it impossible to make the length from each exhaust port of the engine to the collection point of the exhaust manifold approximately equal for each exhaust pipe .

Accordingly, it is an object of the present invention to provide an exhaust manifold of a three-cylinder engine capable of maintaining the output of each cylinder of the three-cylinder engine uniformly.

In a watercraft having a foot step on the left and right, a three-cylinder engine is mounted such that its crankshaft extends in the longitudinal direction of the hull, and the exhaust gas is connected to the exhaust system of the three-cylinder engine. Although the manifold extends outward in the width direction of the hull, if the point of collection of each exhaust pipe of this exhaust manifold is located below the engine, it is difficult to lay out the foot step formed outside of the engine. turn into.

Accordingly, it is an object of the present invention to provide an exhaust manifold for a three-cylinder engine which does not impose any restrictions on the layout of a footstep base of a hull having left and right footsteps.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, the exhaust pipes of the two-sided cylinders are integrated with the exhaust pipe of the central cylinder at the central portion in the crankshaft direction. In the exhaust manifold of a cylinder engine, the exhaust pipe of the central cylinder is made to project outward in the width direction from the exhaust pipes of the other two-sided cylinders when viewed in the crankshaft direction.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the diameter of the exhaust pipe of the central cylinder is larger than that of the exhaust pipes of the other two-sided cylinders.

According to a third aspect of the present invention, there is provided an exhaust manifold connected to an exhaust port of an engine mounted on a hull in which a deck and a hull are assembled, wherein exhaust pipes of both cylinders are connected to an exhaust pipe of a central cylinder. In an exhaust manifold of a three-cylinder engine integrated and integrated at a central portion in the crankshaft direction, the exhaust pipes are guided upward from the exhaust pipes of the respective cylinders to be assembled and sandwiched between the exhaust ports of the central cylinder and the exhaust ports of both cylinders. The exhaust pipe further includes a protrusion protruding above the exhaust port and separating the exhaust port of the central cylinder and the exhaust ports of both cylinders.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the hull has a seat at the center in the width direction, a foot step on the left and right sides of the seat, and the exhaust pipe as viewed in the crankshaft direction. After being guided from the exhaust port toward the outside of the engine, and then bent upward and toward the inside of the engine, so that the central portion of each exhaust pipe is located inside the bent portion of the center line of each exhaust pipe. It is characterized by.

According to a fifth aspect of the present invention, there is provided an exhaust manifold for a three-cylinder engine in which exhaust pipes of both cylinders are integrated with an exhaust pipe of a central cylinder at a central portion in a crankshaft direction. Is larger than that of the exhaust pipes of the other two-sided cylinders.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the exhaust pipe of the central cylinder projects outward in the width direction from the exhaust pipes of the other two cylinders.

According to a seventh aspect of the present invention, in the first to fifth or sixth aspects of the present invention, a common integral flange is provided at an end connected to the engine, and each of the integral flanges is provided in a front view. A part that does not overlap with the exhaust pipe is provided.

Therefore, according to the first aspect of the present invention, the exhaust pipe of the central cylinder projects outward in the width direction from the exhaust pipes of the other two cylinders in the crankshaft direction. The length from the port to the collecting point can be equal to that in the exhaust pipes of the other two-sided cylinders, and from the exhaust port of each cylinder of the engine to the exhaust manifold to the exhaust manifold that flows through each exhaust pipe to the exhaust manifold The exhaust volume of the central cylinder and the other two cylinders are almost the same, and the output of each cylinder in the engine is almost equal, so the setting of the carburetor of each cylinder needs to be performed according to the output of each cylinder as before. According to the second aspect of the present invention, the inner diameter of the exhaust pipe of the central cylinder is changed to the other two-sided cylinder. Since the inner diameter of the exhaust pipe is larger than the inner diameter of the exhaust pipe, even when the center lines of the three exhaust pipes are aligned in the crankshaft direction, the exhaust volume to the collection point of the exhaust gas flowing through the exhaust pipe of the central cylinder is different. The exhaust gas flowing through the exhaust pipes of the two-sided cylinders can be made substantially equal to that of the exhaust gas, and the amount of projection of the exhaust pipe of the central cylinder outward in the width direction can be suppressed when viewed from the crankshaft direction.

According to the third aspect of the invention, when the hull overturns, there is a possibility that water may enter the cylinder from the air intake of the air supply device, and the infiltrated water may be discharged from the exhaust port. However, since the exhaust pipe sandwiched between the exhaust port of the central cylinder and the exhaust port of both cylinders has a projection that protrudes above the exhaust port and partitions the exhaust port of the central cylinder and the exhaust port of both cylinders, In the capsized state, the water discharged from the exhaust ports of the cylinders is prevented from flowing toward the exhaust ports of the other cylinders, smoothly flows toward the collecting portion of the exhaust pipe, and is reliably discharged to the outside.

According to the fourth aspect of the present invention, the exhaust pipe is guided from the exhaust port toward the outside of the engine and then bent upward and toward the inside of the engine when viewed in the crankshaft direction, so that the center line of each exhaust pipe is bent. The central portion of each exhaust pipe is located at the center of the exhaust pipe, so that the amount of projection of the exhaust pipe outward in the width direction when viewed from the crankshaft direction can be reduced, and the seat width can be reduced. Maneuverability can be improved.

According to the fifth aspect of the present invention, the exhaust volume from the exhaust port of each cylinder of the engine to the collection point of the exhaust gas flowing through each exhaust pipe discharged to the exhaust manifold is increased by the central cylinder and the other two-sided cylinders. Thus, the output of each cylinder in the engine is substantially equal, and the setting of the carburetor of each cylinder is not required to be performed according to the output of each cylinder as in the related art, so that the setting of the carburetor is facilitated.

According to the present invention, the length from the exhaust port in the exhaust pipe of the central cylinder to the gathering point can be made equal to that in the exhaust pipes of the other two cylinders. Even if the inner diameter and the inner diameter of the exhaust pipes of the two-sided cylinders are not significantly changed, the exhaust volume of the exhaust gas flowing through the exhaust pipe of the central cylinder to the collection point becomes substantially equal to that of the exhaust gas flowing through the exhaust pipes of the other two-sided cylinders. Thus, it is not necessary to increase the inner diameter of the exhaust pipe of the central cylinder with respect to the inner diameter of the exhaust pipes of the two cylinders, and the pitch between the exhaust ports can be reduced.

According to the seventh aspect of the present invention, the integral flange formed at the end of the exhaust manifold connected to the engine has a portion which does not overlap with each exhaust pipe in a front view (ie, is exposed to the outside). ), High heat dissipation is secured to the integral flange, and its thermal deformation is suppressed to a small value.

[0022]

FIG. 1 is a cutaway side view of a watercraft.
2 is a front view of a three-cylinder engine mounted on the watercraft, FIG. 3 is a front view of an exhaust manifold according to the present invention, FIG. 4 is a plan view of the exhaust manifold, and FIG. 5 is a side view of the exhaust manifold. It is.

A two-cycle three-cylinder engine 3 serving as a driving source is mounted at substantially the center of the hull 2 of the watercraft 1 shown in FIG. 1 in the front-rear direction (left-right direction in FIG. 1). A fuel tank 4 is disposed in front of the vehicle. The upper portion of the fuel tank 4 of the hull 2 is covered by a cowling 5, and a steering handle 6 is provided diagonally outside the cowling 5 above the fuel tank 4, and a seat 7 is provided behind the steering handle 6. Are detachably provided.
The hull 2 is formed by connecting a hull 2a made of FRP (fiber reinforced plastic) and a deck 2b with a gunnel 2c, and the inside of the hull 2 communicates with the atmosphere through front and rear intake ducts 8,9. . As shown in FIGS. 1 and 2, a foot step 2 d on which the occupant seated on the seat 7 places his or her feet is provided on the left and right sides of the hull 2.

The three-cylinder engine 3 has three cylinders arranged in the front-rear direction. The engine 3 is elastically supported on the bottom of the hull 2 via a plurality of engine mounts 10 and has a crankshaft. Reference numeral 11 is arranged in the front-rear direction of the hull. As shown in FIG. 2, an intake pipe 12 is connected to each of the cylinders in an intake system on the right side (on the right side in the traveling direction and on the left side in FIG. 2) of the three-cylinder engine 3. A common intake silencer 13 is connected to the three intake pipes 12, and a carburetor 14 is connected to each intake pipe 12. In FIG. 2,
13a is an air intake of the intake silencer 13, 15 is a throttle valve shaft, 16 is a pulley around which a throttle valve operation wire is wound, 17 is an oil pump, 18 is an oil pump operation wire, and 19 is a wire harness of a flywheel magneto (not shown). This is the extraction hole.

In the exhaust system on the left side of the three-cylinder engine 3, exhaust ports (not shown) of the respective cylinders are opened at equal intervals in the front-rear direction. The exhaust manifold 20 according to the present invention is connected to these exhaust ports. It is connected. The exhaust manifold 20 rises upward, and an exhaust pipe 26 is connected to an end thereof.

The exhaust pipe 26 extends substantially horizontally above the engine 3 toward the front, is bent in a U-shape and extends rearward, and is provided with a water lock 27 disposed behind the engine 3. It is connected to the. An exhaust pipe 28 extends upward from the upper portion of the water lock 27, and the exhaust pipe 28 extends toward the rear of the hull 2. In the present embodiment, a catalyst (not shown) is built in the maximum diameter portion at the highest position of the exhaust pipe 26.

On the other hand, as shown in FIG. 1, a pump chamber 29 is formed at the rear of the hull 2, and a propulsion unit 30 is disposed inside the pump chamber 29. The propulsion unit 30 includes a housing 3 that opens to the bottom and the rear.
In the housing 31, an impeller shaft 32 arranged coaxially with the crankshaft 11 faces, and the impeller shaft 32 is connected to the crankshaft 11 by a coupling 33. An impeller 34 housed in the housing 31 is connected to a rear end of the impeller shaft 32.

The rear end of the housing 31 is open rearward, and a deflector 35 is provided in the opening.
Are swingably mounted on the left and right. The deflector 35 is linked to the steering handle 6 via a cable (not shown), and the watercraft 1 is steered by changing the direction of the deflector 35 by the steering operation of the steering handle 6.

Here, the exhaust manifold 20 according to the present invention will be described with reference to FIGS.

The exhaust manifold 20 has a total of three exhaust pipes 21, 22, 2 corresponding to each cylinder of the three-cylinder engine 3.
3 collectively integrated in the crankshaft direction central portion, front view center line m ₁ of the exhaust pipe 21 to 23 (FIG. 3) to
The gathering point P of m _{3 is} the center point Q of the exhaust port of the central cylinder.
, A rectangular plate-like integral flange 24 common to the three exhaust pipes 21 to 23 is formed at one end on the side connected to the engine 3.
The integral flange 24 is provided with a plurality of (twelve in the illustrated example) bolt insertion holes 24a for passing a fastening bolt (not shown).

As shown in FIG. 5, the three exhaust pipes 21 to 23 are bent upward in a U-shape from the integral flange 24. However, as shown in FIG. The pipe 21 rises vertically when viewed from the front, and the exhaust pipes 22 and 23 of the other two cylinders rise diagonally toward the exhaust pipe 21 of the center cylinder, respectively, as viewed from the front. It is assembled and integrated. As a result, as shown in FIG. 3, the collecting point P of the center lines m _{1 to} m ₃ of the _three exhaust pipes 21 to 23 is located above the center point Q of the exhaust port of the engine 3 by h. .

In the exhaust manifold 20, a substantially rectangular plate-like flange 25 is integrally formed at the end where the three exhaust pipes 21 to 23 are gathered and integrated. Are provided with four bolt insertion holes 25a through which fastening bolts (not shown) are passed.

As shown in FIG. 2, one end of the exhaust manifold 20 constructed as described above has an integral flange 2.
4 is attached to the surface where the exhaust port of the three-cylinder engine 3 is opened by a fastening bolt (not shown) inserted into the bolt insertion hole 24a (see FIG. 3). One end flange portion 26a of the exhaust pipe 26 is attached by a not-shown tightening bolt inserted into 25a (see FIGS. 3 and 4).

In the exhaust manifold 20 according to the present embodiment, as shown in FIGS. 4 and 5, the exhaust pipe 21 of the central cylinder is replaced with the exhaust pipes 22 of the other two-sided cylinders as viewed in the crankshaft direction. 23, it protrudes outward by e in the width direction. In addition, in FIG. 5, R point is each exhaust pipe 21-23.
Are the bending points of the center lines m _{1 to} m ₃ .

By the way, if all the exhaust pipes 21 to 23 are bent at the same curvature so as to overlap each other when viewed from the crankshaft direction, the exhaust pipe 21 of the central cylinder is formed due to a geometrical relationship.
, The length from the exhaust port center point Q to the gathering point P is shorter than that of the exhaust pipes 22 and 23 of the other two cylinders, the inner diameter of the exhaust pipe 21 of the central cylinder and the exhaust pipes 22 and 23 of the two cylinders. When the inner diameters are equal to each other, the exhaust volume of the exhaust gas discharged from the exhaust port of each cylinder of the engine 3 to the exhaust manifold 20 to the collection point P of the exhaust gas flowing through each of the exhaust pipes 21 to 23 becomes larger than the central cylinder and the other cylinders. It is different for both cylinders. Specifically, the exhaust volume of the exhaust gas flowing through the exhaust pipe 21 of the central cylinder becomes smaller than that of the exhaust gas flowing through the exhaust pipes 22 and 23 of the other two-sided cylinders.

As described above, if there is a difference in the exhaust volume between the exhaust gas flowing through the exhaust pipe 21 of the central cylinder and the exhaust gas flowing through the exhaust pipes 22 and 23 of the other two cylinders, a difference in exhaust resistance and the like will occur. This causes a difference in the output of each cylinder in the engine 3. For example, it is necessary to adjust the setting of the carburetor 14 according to the output of each cylinder, and the adjustment work is complicated and troublesome. or,
The performance of the engine 3 cannot be sufficiently exhibited.

However, in this embodiment, the exhaust pipe 21 of the central cylinder is replaced with the exhaust pipes 2 of the other two cylinders in the crankshaft direction.
Because e protruded outward in the width direction from 2, 23,
The length from the center point Q of the exhaust port to the collecting point P in the exhaust pipe 21 of the central cylinder is set to the exhaust pipe 2 of the other two-sided cylinder.
2 and 23.
As a result, the exhaust volume of the exhaust gas discharged from the exhaust port of each cylinder of the engine 3 to the exhaust manifold 20 and flowing through the exhaust pipes 21 to 23 to the collecting point P is substantially equal between the central cylinder and the other two-sided cylinders. As a result, the output of each cylinder in the engine 3 becomes substantially equal, and the setting of the carburetor 14 of each cylinder does not need to be performed in accordance with the output of each cylinder as in the related art, and the setting of the carburetor 14 is facilitated. The effect is obtained. In this case, as in the present embodiment, the center line m ₁ of the exhaust pipe 21 of the central cylinder is the center line m ₂ , m of the exhaust pipes 22 and 23 of both cylinders.
_It is not necessary to be located outside in the width direction than _3, and it is only necessary that a part of the exhaust pipe 21 of the central cylinder protrudes outward in the width direction from the exhaust pipes 22 and 23 of both cylinders.

Also, in the watercraft 1 having the foot steps 2d (see FIGS. 1 and 2) on the left and right sides of the hull 2 as in the present embodiment, the three exhaust pipes 21 to 23 of the exhaust manifold 20 are described above. Set point P of engine 3
As a result, the amount of protrusion e of the exhaust pipe 21 of the central cylinder outward in the width direction when viewed from the crankshaft direction can be suppressed small, and the foot step 2d layout is exhaust manifold 2
You are not restricted by 0.

Further, in the exhaust manifold 20 according to the present embodiment, the exhaust pipes 21 to 21 are formed on the integral flange 24 formed at the end connected to the engine 3 in a front view.
Since a portion that does not overlap with the portion 23 (that is, a portion exposed to the outside) is provided, the integrated flange 24 has a high heat radiation property, and its thermal deformation is suppressed to a small value.

Incidentally, in the exhaust manifold 20 according to the present embodiment, since the three exhaust pipes 21 to 23 have the same inner diameter, the exhaust volume of the exhaust gas flowing through each of the exhaust pipes 21 to 23 to the collecting point P is reduced. As means for making the center cylinder substantially equal to the other two-sided cylinders, the exhaust pipe 21 of the center cylinder is projected outward by a width e from the exhaust pipes 22 and 23 of the other two-sided cylinders when viewed from the crankshaft direction. Although the configuration is adopted, FIG. 6 shows that the exhaust volume of the exhaust gas flowing through the exhaust pipe 21 of the central cylinder to the collection point P is substantially equal to that of the exhaust gas flowing through the exhaust pipes 22 and 23 of the other two cylinders. As shown, the inner diameter d ₁ of the exhaust pipe 21 of the central cylinder is changed to the exhaust pipes 22 and 23 of the other two-sided cylinders.
If greater than the inner diameter d _2, d ₃ of _{(d 1> d 2 = d} 3), it is possible to match the center line of the three exhaust pipes 21 to 23 crankshaft direction as viewed. However, even in this case, the exhaust pipe 21 of the central cylinder projects outward in the width direction from the exhaust pipes 22 and 23 of the other two cylinders by the larger inner diameter in the crankshaft direction. Of course, after setting d ₁ > d ₂ = d ₃ , the center line m ₁ of the exhaust pipe 21 of the central cylinder is shifted outward in the width direction with respect to the center lines m ₂ and m ₃ of the exhaust pipes 22 and 23 of both cylinders. It may be located. Each exhaust pipe 2 shown in FIG.
In 1 to 23, the inner diameters d _{1 to} d ₃ from each exhaust port to the collecting point P are set to be the same. FIG.
In the figure, 37 is a water jacket.

As described above, the exhaust pipe 21 of the center cylinder is replaced with the exhaust pipes 22 and 2 of the other two cylinders as viewed from the crankshaft direction.
If it is configured to protrude outward by e in the width direction beyond 3, the length from the exhaust port in the exhaust pipe 21 of the central cylinder to the gathering point P is increased by the exhaust pipes 22 and 2 of the other two-sided cylinders.
It can be equal to that in 3, without changing much the internal diameter d _2, d ₃ of the inner diameter d ₁ and both side cylinder exhaust pipe 22 of the exhaust pipe 21 of the central cylinder, an exhaust pipe 21 of the central cylinder can discharge volume of up to a set point P of the exhaust gas flowing is set to be substantially equal to that of the exhaust gas flowing through the exhaust pipe 22, 23 other sides cylinders, both sides an inner diameter d ₁ of the exhaust pipe 21 of the central cylinder Cylinder exhaust pipe 22,
It is not necessary to increase the inner diameters d ₂ and d ₃ of the nozzle 23, and the pitch between the exhaust ports can be reduced.

FIG. 6 shows the state of the exhaust manifold 20 when the hull 2 is overturned. In the manifold 20, exhaust pipes 21 to 23 sandwiched between the exhaust port of the central cylinder and the exhaust ports of both cylinders are shown. In addition, since the projecting portions A and B projecting upward from the exhaust port and separating the exhaust port of the central cylinder and the exhaust ports of the two-sided cylinders are formed, the water discharged from the exhaust port of each cylinder in the overturned state is separated from other exhaust ports. The flow toward the exhaust port of the cylinder is prevented by the protruding portions A and B, flows smoothly toward the collecting point P of the exhaust pipes 21 to 23, and is reliably discharged to the outside.

Further, in this embodiment, as shown in FIGS. 2 and 5, the exhaust pipes 21 to 2 are viewed in the crankshaft direction.
After guiding the exhaust pipe 3 from the exhaust port to the outside of the engine 3, the exhaust pipe ₃ is bent upward and toward the inside of the engine 3, and each of the exhaust pipes 21 to 23 is positioned inside the bending point R of the center line m _{1 to} m ₃ of each exhaust pipe 21 to 23. Since the gathering point P of the center lines m _{1 to} m ₃ of the exhaust pipes 21 to 23 is located, the amount of projection of the exhaust pipes 21 to 23 outward in the width direction when viewed from the crankshaft direction (particularly, the upper part of the exhaust manifold 20) (The amount of protrusion outward in the width direction) can be reduced, and the width of the seat 7 can be reduced to enhance the maneuverability.

Next, the operation of the watercraft 1 according to this embodiment will be outlined.

When the three-cylinder engine 3 is driven in the watercraft 1, the rotation of the crankshaft 11 is transmitted to the impeller shaft 32 via the coupling 33, and the impeller shaft 32 and the impeller connected thereto are rotated. 34 are integrally rotated at a predetermined speed.

When the impeller 34 is driven to rotate as described above, the impeller 34 raises the pressure of the water sucked from the boat bottom opening in the housing 31 and pressurizes the water.
Since the water is jetted backward from 5, the water jet generates a required propulsion, and the propulsion causes the watercraft 1 to sail at a predetermined speed.

Incidentally, the above description is particularly applied to the watercraft 3
Although the embodiment in which the present invention is applied to an exhaust manifold attached to a cylinder engine has been described, it is needless to say that the present invention is similarly applicable to an exhaust manifold attached to any other three-cylinder engine.

[0048]

As is apparent from the above description, claim 1
According to the described invention, since the exhaust pipe of the central cylinder projects outward in the width direction from the exhaust pipes of the other two-sided cylinders when viewed in the crankshaft direction, the length from the exhaust port of the exhaust pipe of the central cylinder to the gathering point is increased. Can be made equal to that in the exhaust pipes of the other two-sided cylinders, and the discharge volume from the exhaust port of each cylinder of the engine to the exhaust manifold to the collection point of exhaust gas flowing through each exhaust pipe is equal to that of the central cylinder and other The output of each cylinder in the engine is almost equal, and the setting of the carburetor for each cylinder needs to be performed according to the output of each cylinder as in the past, making it easier to set the carburetor. According to the second aspect of the present invention, the inner diameter of the exhaust pipe of the central cylinder is made larger than the inner diameter of the exhaust pipes of the other two-sided cylinders. Therefore, even when the center lines of the three exhaust pipes are aligned in the crankshaft direction, the exhaust volume of the exhaust gas flowing through the exhaust pipe of the central cylinder to the collection point flows through the exhaust pipes of the other two cylinders. The exhaust gas can be made substantially equal to that of the exhaust gas, and the effect that the amount of protrusion of the exhaust pipe of the central cylinder outward in the width direction as viewed in the crankshaft direction can be reduced.

According to the third aspect of the invention, when the hull overturns, there is a possibility that water may enter the cylinder from the air intake of the air supply device, and the infiltrated water may be discharged from the exhaust port. However, since the exhaust pipe sandwiched between the exhaust port of the central cylinder and the exhaust port of both cylinders has a projection that protrudes above the exhaust port and partitions the exhaust port of the central cylinder and the exhaust port of both cylinders, In the capsized state, the water discharged from the exhaust port of each cylinder is prevented from flowing toward the exhaust port of the other cylinder, smoothly flows toward the gathering portion of the exhaust pipe, and is reliably discharged to the outside. The effect is obtained.

According to the fourth aspect of the present invention, the exhaust pipe is guided from the exhaust port toward the outside of the engine and then bent upward and toward the inside of the engine when viewed from the crankshaft direction. The central portion of each exhaust pipe is located at the center of the exhaust pipe, so that the amount of projection of the exhaust pipe outward in the width direction when viewed from the crankshaft direction can be reduced, and the seat width can be reduced. The effect that maneuverability can be improved is obtained.

According to the fifth aspect of the present invention, the exhaust volume from the exhaust port of each cylinder of the engine to the collection point of the exhaust gas flowing through each exhaust pipe discharged to the exhaust manifold is increased by the central cylinder and the other two-sided cylinders. And the output of each cylinder in the engine is substantially equal, eliminating the need to set the carburetor of each cylinder in accordance with the output of each cylinder as in the past, thus facilitating the setting of the carburetor. Is obtained.

According to the sixth aspect of the present invention, the length from the exhaust port of the exhaust pipe of the central cylinder to the gathering point can be made equal to that of the exhaust pipes of the other two cylinders. Even if the inner diameter and the inner diameter of the exhaust pipes of the two-sided cylinders are not significantly changed, the exhaust volume of the exhaust gas flowing through the exhaust pipe of the central cylinder to the collection point becomes substantially equal to that of the exhaust gas flowing through the exhaust pipes of the other two-sided cylinders. This eliminates the need to increase the inner diameter of the exhaust pipe of the central cylinder with respect to the inner diameter of the exhaust pipes of the two-sided cylinders, and has the effect of reducing the pitch between the exhaust ports.

According to the seventh aspect of the invention, the integral flange formed at the end of the exhaust manifold connected to the engine has a portion that does not overlap with each exhaust pipe in a front view (ie, is exposed to the outside). Since the integral flange is provided, high heat dissipation is ensured in the integral flange, and the effect that the thermal deformation thereof is suppressed to be small can be obtained.

[Brief description of the drawings]

FIG. 1 is a cutaway side view of a watercraft.

FIG. 2 is a front view of a three-cylinder engine mounted on the watercraft.

FIG. 3 is a front view of an exhaust manifold according to the present invention.

FIG. 4 is a plan view of an exhaust manifold according to the present invention.

FIG. 5 is a side view of the exhaust manifold according to the present invention.

FIG. 6 is a cutaway front view showing a state of the exhaust manifold when the hull is overturned.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Watercraft 2 Hull 2a Hull 2b Deck 2d Footstep 3 3-cylinder engine 7 Seat 11 Crankshaft 20 Exhaust manifold 21 Central cylinder exhaust pipe 22, 23 Exhaust pipe of both cylinders 24 Integrated flange A, B Projection e Central cylinder Exhaust pipe protrusion amount m _{1 to} m ₃ Exhaust pipe center line P Exhaust pipe gathering point R Exhaust pipe center line bending point

Claims (7)

[Claims] 1. An exhaust manifold for a three-cylinder engine in which exhaust pipes of both cylinders are integrated with an exhaust pipe of a central cylinder at a central portion in a crankshaft direction, wherein an exhaust pipe of the central cylinder is viewed in a crankshaft direction. An exhaust manifold for a three-cylinder engine characterized by projecting outward in the width direction from the exhaust pipes of the other two-sided cylinders. 2. The exhaust manifold for a three-cylinder engine according to claim 1, wherein the diameter of the exhaust pipe of the central cylinder is larger than that of the exhaust pipes of the other two-sided cylinders. 3. An exhaust manifold connected to an exhaust port of an engine mounted on a hull in which a deck and a hull are assembled, wherein exhaust pipes of both cylinders are arranged at a central portion in a crank axis direction with respect to an exhaust pipe of a central cylinder. Collectively integrated 3
In the exhaust manifold of the cylinder engine, the exhaust pipes are guided upward from the exhaust pipes of the respective cylinders to be assembled, and the exhaust pipes interposed between the exhaust port of the central cylinder and the exhaust ports of both cylinders project upward from the exhaust ports. An exhaust manifold for a three-cylinder engine, wherein a protruding portion is formed to partition an exhaust port of a central cylinder and an exhaust port of both cylinders. 4. The hull has a seat at the center in the width direction, and has a foot step on the left and right sides of the seat.
After guiding the exhaust pipe from the exhaust port toward the outside of the engine in the crankshaft direction, the exhaust pipe is bent upward and toward the inside of the engine, and the center line of each exhaust pipe is located inside the bent portion of the center line of each exhaust pipe. 4. An exhaust manifold for a three-cylinder engine according to claim 3, wherein a gathering portion is located. 5. An exhaust manifold for a three-cylinder engine in which exhaust pipes of both cylinders are integrated with an exhaust pipe of a central cylinder at a central part in a crankshaft direction. An exhaust manifold for a three-cylinder engine, wherein the exhaust manifold is larger than that of a cylinder exhaust pipe. 6. The exhaust manifold for a three-cylinder engine according to claim 5, wherein the exhaust pipe of the central cylinder projects outward in the width direction from the exhaust pipes of the other two cylinders. 7. An end portion on a side connected to the engine has a common integral flange, and the integral flange is provided with a portion which does not overlap with each exhaust pipe in a front view. An exhaust manifold for a three-cylinder engine according to claim 5 or 6.