JP7530505B2 - Motorcycles - Google Patents

Description

The present invention relates to a motorcycle.

Motorcycles that use engines as their driving source have been known for some time, but in recent years, there has been a strong demand for reducing the amount of air pollutants emitted from motorcycles in order to protect the global environment. For example, Patent Document 1 discloses a motorcycle that has a catalytic device installed in the exhaust pipe to purify the exhaust gas emitted from the engine.

Japanese Patent Registration No. 3154340

However, in the motorcycle of Patent Document 1, the catalytic converter is located in the exhaust pipe near the downstream end connected to the muffler or in front of the engine. When the catalytic converter is located near the downstream end of the exhaust pipe, the flow path from the exhaust port of the engine to the catalytic converter is long, and the exhaust gas discharged from the exhaust port of the engine is cooled by outside air, lowering the temperature of the exhaust gas supplied to the catalytic converter, making it difficult to activate the catalyst in the catalytic converter. In addition, when the catalytic converter is located in front of the engine, the catalytic converter is cooled by the wind while the engine is running, making it difficult to activate the catalyst in the catalytic converter. Thus, because the catalytic converter is difficult to activate in the catalytic converter of the motorcycle of Patent Document 1, there is room for improvement in the exhaust purification performance of the motorcycle.

The present invention provides a motorcycle with improved exhaust purification performance.

The present invention relates to
an engine having an exhaust port;
an exhaust pipe having an upstream end connected to the exhaust port of the engine,
The exhaust port of the engine is provided on a rear surface of the engine,
The exhaust pipe is
a rear extension portion having a front end portion that constitutes the upstream end portion, the front end portion being connected to the exhaust port and extending rearward;
a bent portion bent from a rear end portion of the rear extension portion to one side in a vehicle width direction;
a lateral extending portion extending from the bent portion to the one side in a vehicle width direction;
a forward extension portion extending forward from an end portion on the one side in the vehicle width direction of the lateral extension portion to face a side surface on the one side in the vehicle width direction of the engine,
The exhaust pipe is provided with a plurality of catalytic converters,
At least one of the catalytic converters is disposed rearward of the engine and is disposed adjacent the upstream end and on the laterally extending portion,
the catalytic converter is disposed at a position where at least a portion of the catalytic converter overlaps with the engine in a vehicle width direction when viewed from behind the motorcycle ,
At least one of the catalytic converters is provided on the forward extension and is disposed at a position where at least a portion of the catalytic converter overlaps with the engine in the front-rear direction.

According to the present invention, since the catalytic converter is provided near the upstream end, the exhaust gas supplied to the catalytic converter is less likely to be cooled by outside air. This allows hotter exhaust gas to be supplied to the catalytic converter, which makes it easier for the catalyst to be activated in the catalytic converter, improving the exhaust purification performance of the motorcycle.

1 is a side view of a motorcycle according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA of FIG. 1.

An embodiment of the motorcycle of the present invention will be described below with reference to the attached drawings. The drawings are to be viewed in the direction of the reference symbols. In order to simplify and clarify the description in this specification, the front/rear, left/right, and up/down directions are described according to the direction as seen by the rider of the motorcycle, and in the drawings, the front of the vehicle is indicated as Fr, the rear as Rr, the left as L, the right as R, the top as U, and the bottom as D.

<Overall structure of motorcycle>
As shown in Figure 1, a motorcycle 1 has a head pipe 2 at the front of the vehicle body. A handlebar 11 is attached above the head pipe 2 so as to be rotatable in the left and right direction. A pair of left and right front forks 13 are disposed below the head pipe 2.

An axle 14 is fixed to the lower ends of the pair of front forks 13. A front wheel 15 is rotatably attached to the axle 14. A front fender 16 that covers the upper part of the front wheel 15 is disposed above the front wheel 15.

A pair of left and right tank frames 3 that curve from the head pipe 2 outward in the vehicle width direction and extend rearward are connected to the head pipe 2, and a down frame 4 that extends rearward and downward from the head pipe 2.

A main frame 5 extending rearward and downward is connected to the rear end of each of the left and right tank frames 3. That is, a pair of main frames 5 are provided on the left and right, with one main frame 5 connected to the left tank frame 3 and the other main frame 5 connected to the right tank frame 3.

A pair of left and right lower frames 6 that curve outward in the vehicle width direction and extend rearward are connected to the lower end of the down frame 4. The rear ends of the left and right lower frames 6 are connected to the lower ends of the left and right main frames 5.

A plastic fuel tank 32 is disposed on the upper portion of the tank frame 3 so as to extend rearward from the head pipe 2. The front portion of a seat 33 is disposed above the fuel tank 32. The seat 33 is formed so as to extend rearward from the fuel tank 32.

The engine 17 is arranged below the fuel tank 32 in the space surrounded by the left and right tank frames 3, the down frame 4, the left and right main frames 5, and the left and right lower frames 6.

The engine 17 is fixed near the lower end of the down frame 4, the left and right main frames 5, and the left and right lower frames 6. The engine 17 is arranged so that the cylinder axis extending in the vertical direction is inclined rearward from the bottom to the top. The engine 17 in this embodiment is a single-cylinder engine having one cylinder.

The engine 17 is configured with a crankcase 17a that houses a rotating crankshaft (not shown), a cylinder section 17b, a cylinder head 17c arranged above the cylinder section 17b, and a cylinder head cover 17d. The cylinder section 17b of the engine 17 has one cylinder (not shown) therein. The cylinder head 17c of the engine 17 has an intake port 17e (see FIG. 2) provided at the front of the engine 17 and an exhaust port 17f (see FIG. 2) provided at the rear of the engine 17. In other words, the engine 17 is a single-cylinder engine with front intake and rear exhaust.

An upstream end 22a of an exhaust pipe 22 that guides exhaust gas from the engine 17 is connected to the rear surface of the cylinder head 17c of the engine 17. The exhaust pipe 22 extends rearward from the rear surface of the engine 17, and then extends to surround the left side, front, and right side of the engine 17. The exhaust pipe 22 extends further rearward after extending along the right side of the engine 17, and the downstream end of the exhaust pipe 22 connects to a muffler 23 disposed rearward of the engine 17. Therefore, exhaust gas discharged rearward from the exhaust port 17f of the engine 17 passes through the exhaust pipe 22 and is discharged from the muffler 23. Details of the exhaust pipe 22 will be described later.

Each of the left and right main frames 5 is provided with a pivot shaft 25 whose axis extends in the vehicle width direction. The front end of a rear arm 26 extending in the front-rear direction is journalled on the pivot shaft 25. The rear arm 26 is journalled so as to be rotatable up and down around the pivot shaft 25. A rear wheel 28 is rotatably attached to the rear end of the rear arm 26. A pair of rear arms 26 are provided on the left and right sides with the rear wheel 28 in between.

The rear wheel 28 is provided with a driven sprocket 28a that rotates together with the rear wheel 28. A chain 29 is wound around the driven sprocket 28a, and the chain 29 is driven by the engine 17. The driven sprocket 28a and the chain 29 are disposed on the left side in the vehicle width direction.

A rear suspension 27 is provided between the pair of left and right main frames 5 near the rear ends of the pair of left and right main frames 5. The rear suspension 27 has a generally cylindrical shape extending in the vertical direction, and extends in the vertical direction, tilting forward from bottom to top. The upper end of the rear suspension 27 is connected to the main frame 5. The lower end of the rear suspension 27 is connected to the rear arm 26 via a link mechanism 30. The rear suspension 27 is configured to be compressible and expandable in the vertical direction, and absorbs shocks when the rear wheels 28 move in the vertical direction.

<Exhaust pipe configuration>
As shown in FIG. 2, the engine 17 is provided at its front with an intake port 17e, and at its rear with an exhaust port 17f.

The exhaust pipe 22 has a front end portion that constitutes the upstream end portion 22a, a first rearward extending portion 221 that is connected to the exhaust port 17f and extends rearward, a bent portion 222 that bends from the rear end portion of the first rearward extending portion 221 to the left in the vehicle width direction, a first lateral extending portion 223 that extends from the bent portion 222 to the left in the vehicle width direction, and a left end portion of the first lateral extending portion 223 that extends forward in the vehicle width direction opposite the left side surface 17L of the engine 17. The engine 17 has a forward extension portion 224, a second lateral extension portion 225 that curves to the right from the front end of the forward extension portion 224 and extends in the vehicle width direction opposite the front surface 17F of the engine 17, and a second rearward extension portion 226 that extends rearward from the right end of the second lateral extension portion 225 opposite the right side surface 17R of the engine 17 and extends rearward beyond the right side surface 17R of the engine 17, and whose rear end constitutes the downstream end portion and is connected to the muffler 23.

A first catalytic device 241 is provided near the upstream end 22a of the exhaust pipe 22. More specifically, the first catalytic device 241 is provided in the first lateral extension 223, and is disposed behind the engine 17 such that at least a portion of the first catalytic device 241 overlaps with the engine 17 in the vehicle width direction.

Because the first catalytic device 241 is located near the upstream end 22a, the exhaust gas supplied to the first catalytic device 241 is less likely to be cooled by outside air. As a result, the first catalytic device 241 is supplied with hotter exhaust gas, which makes it easier for the catalyst to be activated in the first catalytic device 241, improving the exhaust purification performance of the motorcycle 1.

In addition, the first catalytic device 241 is positioned behind the engine 17, and at least a portion of it is positioned so as to overlap with the engine 17 in the vehicle width direction, so that the first catalytic device 241 can be provided near the upstream end 22a while suppressing the expansion of the motorcycle 1 in the vehicle width direction.

Furthermore, since the first catalytic device 241 is provided in the first lateral extension portion 223, the first catalytic device 241 can be provided near the upstream end portion 22a without increasing the overall length of the exhaust pipe 22.

A bulge 222a is formed in the bent portion 222 of the exhaust pipe 22. In this embodiment, the bulge 222a bulges in the right-rear direction. Note that the bulge 222a is not limited to the right-rear direction, and may bulge in the upper-rear direction or the lower-rear direction.

If the bent portion 222 does not have a bulge 222a, the exhaust gas discharged rearward from the exhaust port 17f of the engine 17 tends to flow in a straight line, and after passing through the first rear extension portion 221, most of the exhaust gas flows leftward along the rear side surface of the bent portion 222. Therefore, in the first catalytic device 241, while a lot of exhaust gas passes through the rear region, less exhaust gas passes through the front region, and the flow rate of the exhaust gas flowing through the first catalytic device 241 becomes uneven across the flow path cross section, and the exhaust purification performance of the first catalytic device 241 decreases.

In this embodiment, the bent portion 222 is formed with the bulge portion 222a, so that at least a portion of the exhaust gas discharged rearward from the exhaust port 17f of the engine 17 passes through the first rear extension portion 221, hits the bulge portion 222a, and flows turbulently to the first catalytic device 241. This makes the flow rate of the exhaust gas flowing through the first catalytic device 241 more uniform across the flow path cross section, improving the exhaust purification performance of the first catalytic device 241.

In this embodiment, the exhaust pipe 22 is provided with a second catalytic device 242 downstream of the first catalytic device 241. The second catalytic device 242 is provided in the forward extension portion 224 and is positioned so that at least a portion of the second catalytic device 242 overlaps with the engine 17 in the fore-and-aft direction.

In this way, by providing the second catalytic device 242 in addition to the first catalytic device 241, it is possible to reduce the size of the first catalytic device 241 and the second catalytic device 242. Furthermore, since the second catalytic device 242 is positioned so that at least a portion of it overlaps with the engine 17 in the fore-and-aft direction, it is possible to provide a catalytic device in the exhaust pipe 22 while suppressing dimensional expansion of the motorcycle 1 in the fore-and-aft direction and the vehicle width direction.

In addition, the second catalytic device 242 is provided on the forward extension portion 224 and is positioned so that at least a portion of it overlaps with the engine 17 in the fore-and-aft direction, so that the second catalytic device 242 can be positioned downstream of the first catalytic device 241 and in the vicinity of the first catalytic device 241. This makes it possible to prevent the exhaust gas that has been heated by passing through the first catalytic device 241 from being cooled by outside air before being supplied to the second catalytic device 242. Therefore, the second catalytic device 242 is supplied with exhaust gas at a higher temperature, which makes it easier to activate the catalyst in the second catalytic device 242, and further improves the exhaust purification performance of the motorcycle 1.

Although one embodiment of the present invention has been described above with reference to the attached drawings, it goes without saying that the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the claims, and it is understood that these naturally fall within the technical scope of the present invention. Furthermore, the components in the above embodiment may be combined in any manner as long as it does not deviate from the spirit of the invention.

For example, in this embodiment, the exhaust pipe 22 is provided with the second catalytic device 242 in addition to the first catalytic device 241, but the second catalytic device 242 does not have to be provided. In other words, the second catalytic device 242 can be omitted.

This specification describes at least the following items. In parentheses, corresponding components etc. in the above-mentioned embodiment are shown as examples, but are not limited to these.

(1) an engine (engine 17) provided with an exhaust port (exhaust port 17f);
an exhaust pipe (exhaust pipe 22) having an upstream end (upstream end 22a) connected to the exhaust port of the engine,
The exhaust port of the engine is provided on a rear surface of the engine,
The exhaust pipe is provided with a catalytic converter (first catalytic converter 241) near the upstream end thereof.

According to (1), since the catalytic converter is provided near the upstream end, the exhaust gas supplied to the catalytic converter is less likely to be cooled by outside air. This allows hotter exhaust gas to be supplied to the catalytic converter, which makes it easier for the catalyst to be activated in the catalytic converter, improving the exhaust purification performance of the motorcycle.

(2) The motorcycle according to (1),
The catalytic converter is disposed behind the engine and at least a portion of the catalytic converter is disposed at a position overlapping with the engine in a vehicle width direction.

According to (2), the catalytic converter is positioned behind the engine and at least a portion of the catalytic converter is positioned so as to overlap with the engine in the vehicle width direction. This makes it possible to provide the catalytic converter near the upstream end while suppressing the expansion of the motorcycle's width direction dimension.

(3) The motorcycle according to (2),
The exhaust pipe is
a rear extension portion (first rear extension portion 221) having a front end portion that constitutes the upstream end portion and is connected to the exhaust port and extends rearward;
a bent portion (bent portion 222) that bends from a rear end of the rear extension portion to one side in the vehicle width direction; and a lateral extension portion (first lateral extension portion 223) that extends from the bent portion to the one side in the vehicle width direction,
The catalytic converter is provided on the laterally extending portion.

According to (3), since the catalytic device is provided in the laterally extending portion, the catalytic device can be provided near the upstream end without increasing the overall length of the exhaust pipe.

(4) The motorcycle according to (3),
The motorcycle, wherein a bulge (bulge 222a) is formed at the bent portion of the exhaust pipe.

According to (4), since a bulge is formed at the bent portion, at least a portion of the exhaust gas discharged rearward from the exhaust port of the engine hits the bulge and flows into the catalytic converter as a turbulent flow. This makes the flow rate of the exhaust gas flowing through the catalytic converter more uniform across the cross section of the flow path, improving the exhaust purification performance of the catalytic converter.

(5) A motorcycle according to any one of (1) to (4),
The exhaust pipe is
A rear extension portion (first rear extension portion 221) whose front end portion is connected to the exhaust port and extends rearward;
a bent portion (bent portion 222) bent from a rear end portion of the rear extension portion to one side (left side) in the vehicle width direction;
A lateral extension portion (first lateral extension portion 223) extending from the bent portion to the one side in the vehicle width direction;
a forward extending portion (forward extending portion 224) extending forward from the end portion on the one side in the vehicle width direction of the lateral extending portion to face the side surface on the one side in the vehicle width direction of the engine,
The exhaust pipe is provided with a plurality of the catalytic devices,
At least one of the catalytic converters (first catalytic converter 241) is provided on the laterally extending portion and is disposed at a position where at least a portion of the catalytic converter overlaps with the engine in the vehicle width direction,
At least one of the catalytic converters (second catalytic converter 242) is provided on the forward extension portion and is disposed at a position where at least a portion of the catalytic converter overlaps with the engine in the front-rear direction.

According to (5), since the exhaust pipe is provided with a plurality of catalytic converters, each catalytic converter can be made compact. Furthermore, since the second catalytic converter is disposed at a position where at least a portion overlaps with the engine in the longitudinal direction, the catalytic converter can be provided in the exhaust pipe while suppressing the expansion of the motorcycle in the longitudinal direction and the vehicle width direction. Furthermore, since the second catalytic converter is disposed in the forward extension and at least a portion overlaps with the engine in the longitudinal direction, the second catalytic converter can be disposed downstream of the first catalytic converter and in the vicinity of the first catalytic converter. This prevents the exhaust gas that has been heated by passing through the first catalytic converter from being cooled by the outside air before being supplied to the second catalytic converter. Therefore, the second catalytic converter is supplied with a higher temperature exhaust gas, which makes it easier to activate the catalyst in the second catalytic converter, and further improves the exhaust purification performance of the motorcycle.

This application is based on a Japanese patent application (Patent Application No. 2021-052249) filed on March 25, 2021, the contents of which are incorporated herein by reference.

1 Motorcycle 17 Engine 17f Exhaust port 22 Exhaust pipe 22a Upstream end 221 First rear extension portion (rear extension portion)
222 Bent part 222a Swelling part 223 First horizontally extending part (laterally extending part)
224 Front extension part 241 First catalyst device (catalyst device)
242 Second catalyst device (catalyst device)

Claims (2)

An engine (17) provided with an exhaust port (17f);
an exhaust pipe (22) having an upstream end (22a) connected to the exhaust port (17f) of the engine (17),
The exhaust port (17f) of the engine (17) is provided on a rear surface of the engine (17),
The exhaust pipe (22)
a rear extension portion (221) whose front end portion constitutes the upstream end portion (22a) and whose front end portion is connected to the exhaust port (17f) and extends rearward;
A bent portion (222) bent from a rear end portion of the rear extension portion (221) to one side in the vehicle width direction;
A lateral extension portion (223) extending from the bent portion (222) to the one side in the vehicle width direction;
a forward extending portion (224) extending forward from the end portion on the one side in the vehicle width direction of the lateral extending portion (223) to face the side surface on the one side in the vehicle width direction of the engine (17),
The exhaust pipe (22) is provided with a plurality of catalytic devices (241, 242),
At least one catalytic converter (241) is disposed rearward of the engine (17) and is provided in the vicinity of the upstream end (22a) and on the lateral extension (223);
the catalytic converter (241) is disposed at a position where at least a portion of the catalytic converter overlaps with the engine (17) in a vehicle width direction when viewed from the rear of the motorcycle (1) ;
At least one of the catalytic devices (242) is provided on the front extension portion (224) and is disposed at a position where at least a portion of the catalytic device overlaps with the engine (17) in the front-rear direction. A motorcycle (1) according to claim 1,
The motorcycle (1), wherein a bulge (222a) is formed at the bent portion (222) of the exhaust pipe (22).

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