WO2016002953A1

WO2016002953A1 - Saddle-driven vehicle

Info

Publication number: WO2016002953A1
Application number: PCT/JP2015/069352
Authority: WO
Inventors: 昌登西垣; 裕次荒木; 一裕石澤; 誠脇村
Original assignee: ヤマハ発動機株式会社
Priority date: 2014-07-04
Filing date: 2015-07-03
Publication date: 2016-01-07
Also published as: JP2017149166A; TW201612407A

Abstract

Provided is a saddle-driven vehicle capable of increasing the purification performance of exhaust gas by a catalyst, suppressing an increase in the size of the vehicle in the vertical direction thereof, and reducing the effect caused by the heat of a catalyst. An opening (17) is formed in the front section of a chassis cover (11). The chassis cover (11) covers at least part of the upper surface of an engine body (20), and includes an engine cover section (16) formed in a manner such that both end sections thereof in the left-right direction are positioned below the center section thereof in the left-right direction. At least part of an intake channel section (33) is positioned between the engine cover section (16) and the upper surface of the engine body (20). A fuel injection device (48) is positioned to the front of the rearmost end of the intake channel section (33). When viewing the engine unit (19) and the chassis cover (11) from the front, at least part of the fuel injection device (48) is positioned in a location which is visible inside the opening (17).

Description

Saddle riding vehicle

The present invention relates to a saddle riding type vehicle.

Conventionally, there is a straddle-type vehicle equipped with a single cylinder four-stroke engine unit. And the structure which arrange | positions a catalyst upstream from the silencer of an exhaust passage is proposed (for example, patent document 1). According to the proposal of Patent Document 1, high-temperature exhaust gas can flow into the catalyst. The activity of the catalyst increases at higher temperatures. Therefore, the exhaust gas purification performance by the catalyst can be improved.

JP 2006-207571 A

However, the catalyst is very hot compared to the engine body. Therefore, if the catalyst is arranged upstream of the silencer, it is necessary to take measures against heat damage to the catalyst. On the other hand, the saddle-ride type vehicle of Patent Document 1 needs to secure a vertical distance between the ground and the single-cylinder four-stroke engine unit. Therefore, for example, when a heat insulating member is provided between the engine main body and the catalyst, the engine main body needs to be arranged further upward. Therefore, there is a problem that the saddle riding type vehicle is enlarged in the vertical direction.

An object of the present invention is to provide a straddle-type vehicle that can improve the purification performance of exhaust gas by a catalyst, suppress an increase in the size of the vehicle in the vertical direction, and reduce the influence of the heat of the catalyst. is there.

The above proposal of Patent Document 1 was examined in detail. The saddle riding type vehicle of Patent Document 1 includes an engine body having a crankcase portion and a horizontal cylinder portion extending in the front-rear direction from the crankcase portion. The saddle riding type vehicle of Patent Literature 1 includes a catalyst below the engine body of a single cylinder four-stroke engine unit. Therefore, the hot air from the catalyst rises along the periphery of the engine body. Further, the saddle riding type vehicle of Patent Document 1 includes a vehicle body cover above the engine body so as to cover at least a part of the upper surface of the engine body. Therefore, the heat that has risen from the engine body and the catalyst tends to be trapped in the space covered by the vehicle body cover above the engine body. Moreover, in a vehicle such as the saddle riding type vehicle of Patent Document 1, the intake pipe and the fuel injection device are often arranged above the horizontal cylinder portion. Therefore, in a saddle-ride type vehicle such as Patent Document 1 having a horizontal cylinder portion, intake system components or fuel supply system components are arranged in a space where the heat is generated. And if the fuel supply system components become high temperature, the performance of the engine may change.

The inventors of the present application paid attention to the shape of the space covered by the vehicle body cover above the engine body during research and development. In the space covered by the vehicle body cover above the engine body of the saddle riding type vehicle as in Patent Document 1, the distance between the front part and the engine body is formed larger than the distance between the center part or the rear part and the engine body. . Moreover, the front portion of the space covered by the vehicle body cover above the engine body is open to the front of the vehicle. Therefore, by utilizing the shape of the space covered by the vehicle body cover above the engine body of the saddle riding type vehicle, the arrangement of the intake system parts or the fuel supply system parts can be devised so that hot air rises from the catalyst. I came up with the idea that the effects of heat on the intake system components or fuel supply system components can be reduced. In addition, by utilizing the shape of the space covered by the vehicle body cover above the engine body of the saddle riding type vehicle, the heat of the catalyst affects the surroundings by devising the arrangement of intake system components or fuel supply system components. I noticed that the heat insulation structure can be simplified so as not to reach. Furthermore, it has been found that even if the catalyst is enlarged in order to improve the purification performance by the catalyst, the influence of the heat of the catalyst can be suppressed.

A straddle-type vehicle according to the present invention is a straddle-type vehicle on which a single-cylinder four-stroke engine unit is mounted, and the single-cylinder four-stroke engine unit is a part of which is defined by an inner surface of a cylinder hole. A combustion chamber, a single combustion chamber cylinder intake passage portion through which air supplied to the one combustion chamber flows, and a single combustion chamber cylinder exhaust passage portion through which exhaust gas discharged from the one combustion chamber flows; An engine main body having a horizontal cylinder portion provided so that a center line of the cylinder hole extends in the front-rear direction of the saddle riding type vehicle; and at least a part of the engine main body is disposed above the engine main body. A single combustion chamber intake passage portion connected to the upstream end of the single combustion chamber cylinder intake passage portion, and at least a part of the intake passage portion is disposed below the engine body, and the front A single combustion chamber exhaust pipe connected to the downstream end of the single combustion chamber cylinder exhaust passage portion of the engine body, and a discharge port facing the atmosphere, and connected to the single combustion chamber exhaust pipe The exhaust gas flowing in from the downstream end of the exhaust pipe for the single combustion chamber is caused to flow to the discharge port, and the silencer for the single combustion chamber for reducing the sound generated by the exhaust gas is disposed in the exhaust pipe for the single combustion chamber. , For a single combustion chamber that is at least partially disposed below the engine body and most purifies the exhaust gas discharged from the one combustion chamber in the exhaust path from the one combustion chamber to the discharge port. The main catalyst is provided in the single combustion chamber intake passage portion or the single combustion chamber cylinder intake passage portion, and in front of the rear end of the single combustion chamber intake passage portion in the front-rear direction. Placed and before A fuel injection device for injecting fuel into the air sucked from the upstream end of the intake passage portion for the single combustion chamber, covering at least a part of the upper surface of the engine body, and of the straddle-type vehicle A single combustion chamber intake passage, comprising: a vehicle body cover including an engine cover portion formed such that both ends in the left-right direction are positioned below the center in the left-right direction, and an opening is formed in a front portion thereof; The portion is at least partially disposed between the engine cover portion and the upper surface of the engine body, and in the front-rear direction, a rear end thereof is disposed behind the opening of the vehicle body cover, The single combustion chamber exhaust pipe is disposed at least partially behind the opening of the vehicle body cover in the front-rear direction, and the fuel injection device is configured to be a single-cylinder four-stroke engine unit. When the robot and the vehicle body cover are viewed from the front, at least a part of the vehicle body cover is disposed at a position where it can be seen in the opening of the vehicle body cover.

According to this configuration, the single-cylinder four-stroke engine unit mounted on the saddle riding type vehicle of the present invention includes an engine body, a single combustion chamber intake passage, a single combustion chamber exhaust pipe, and a single combustion. A chamber silencer, a single combustion chamber main catalyst, and a fuel injection device are provided. The engine body has a horizontal cylinder portion. In the horizontal cylinder portion, one combustion chamber, a single combustion chamber cylinder intake passage portion, and a single combustion chamber cylinder exhaust passage portion are formed. A part of the combustion chamber is defined by the inner surface of the cylinder hole. In the single combustion chamber cylinder intake passage portion, air supplied to one combustion chamber flows. The exhaust gas discharged from one combustion chamber flows through the cylinder exhaust passage for the single combustion chamber. The single combustion chamber intake passage portion is connected to the upstream end of the single combustion chamber cylinder intake passage portion of the engine body. The single combustion chamber exhaust pipe is connected to the downstream end of the single combustion chamber cylinder exhaust passage portion of the engine body. The single combustion chamber silencer has an outlet facing the atmosphere. The single combustion chamber silencer is connected to the single combustion chamber exhaust pipe and flows the exhaust gas flowing in from the downstream end of the single combustion chamber exhaust pipe to the discharge port. The single combustion chamber silencer reduces the noise produced by the exhaust gas. The main catalyst for the single combustion chamber is disposed in the exhaust pipe for the single combustion chamber. The main catalyst for a single combustion chamber purifies the exhaust gas discharged from one combustion chamber most in the exhaust path from one combustion chamber to the discharge port. The fuel injection device injects fuel into the air sucked from the upstream end of the single combustion chamber intake passage portion. The fuel injection device is provided in a single combustion chamber intake passage portion or a single combustion chamber cylinder intake passage portion. The horizontal cylinder portion is provided such that the center line of the cylinder hole extends in the front-rear direction of the saddle riding type vehicle. Accordingly, at least a portion of the single combustion chamber intake passage portion is disposed above the engine body. Further, at least a part of the single combustion chamber exhaust pipe is disposed below the engine body. At least a part of the single combustion chamber main catalyst is disposed below the engine body. Therefore, the hot air from the main catalyst for the single combustion chamber rises to the upper part of the engine body through the periphery of the engine body.

At least a part of the upper surface of the engine body is covered with the engine cover part of the vehicle body cover. Further, the engine cover portion disposed above the engine body is formed such that both end portions in the left-right direction are located below the center in the left-right direction. Further, at least a part of the single combustion chamber exhaust pipe is disposed behind the front opening of the vehicle body cover. Therefore, the heat that has risen from the main catalyst for the single combustion chamber and the engine body is likely to go into the space covered by the vehicle body cover above the engine body.

Also, the rear end of the intake passage for the single combustion chamber is arranged behind the opening of the vehicle body cover. At least a portion of the single combustion chamber intake passage portion is disposed between the engine cover portion and the upper surface of the engine body. That is, at least a part of the single combustion chamber intake passage portion is disposed in a space covered by the vehicle body cover above the engine body. As described above, in the space covered by the vehicle body cover above the engine main body, the heat that has risen from the main catalyst for the single combustion chamber and the engine main body tends to be generated.

However, the body cover of the straddle-type vehicle of the present invention has an opening formed at the front thereof. Therefore, the front part of the space covered with the vehicle body cover above the engine body is open to the front of the vehicle. For this reason, the heat generated in the space covered by the vehicle body cover above the engine body easily escapes forward. That is, the temperature at the front of the space is relatively low. The fuel injection device for a saddle-ride type vehicle according to the present invention is disposed in front of the rear end of the intake passage portion for a single combustion chamber. That is, the fuel injection device is disposed at a position close to the opening of the vehicle body cover. Furthermore, when the single-cylinder four-stroke engine unit and the vehicle body cover are viewed from the front, at least a part of the fuel injection device is visible in the opening of the vehicle body cover. Therefore, even if heat is generated in the space covered by the vehicle body cover above the engine body, the influence of heat on the fuel injection device can be suppressed. That is, even if hot air rises from the single combustion chamber main catalyst, the influence of heat on the fuel injection device can be suppressed. Therefore, even if the single combustion chamber main catalyst is enlarged in order to improve the purification performance of the single combustion chamber main catalyst, the influence of the heat of the single combustion chamber main catalyst can be suppressed.

Thus, by devising the arrangement position of the fuel injection device, the influence of the heat of the single combustion chamber main catalyst on the fuel injection device can be suppressed. Therefore, it is possible to simplify the structure for heat insulation so that the heat of the single combustion chamber main catalyst does not affect the surroundings. Therefore, even if the single combustion chamber main catalyst is enlarged in order to improve the purification performance of the single combustion chamber main catalyst, the vehicle can be prevented from being enlarged in the vertical direction.

As described above, the straddle-type vehicle according to the present invention can suppress the increase in the size of the vehicle in the vertical direction while reducing the exhaust gas purification performance of the catalyst, and can reduce the influence of the heat of the catalyst.

In the straddle-type vehicle of the present invention, it is preferable that a part of the fuel injection device is disposed in front of the single combustion chamber intake passage portion.

With this configuration, the fuel injection device is arranged at a position closer to the front opening of the vehicle body cover. Therefore, even if hot air rises from the single combustion chamber main catalyst, the influence of heat on the fuel injection device can be further suppressed. Therefore, even if the single combustion chamber main catalyst is enlarged in order to improve the purification performance of the single combustion chamber main catalyst, the influence of the heat of the single combustion chamber main catalyst can be further suppressed.

In the saddle riding type vehicle according to the present invention, the vehicle body cover has a maximum vertical separation distance between a front end of the engine cover portion and an upper surface of the engine body so that a center or a rear end in the front-rear direction of the engine cover portion and the engine It is preferable to be formed so as to be larger than the maximum vertical separation distance from the upper surface of the main body.

According to this configuration, the vertical distance between the front end of the engine cover portion and the upper surface of the engine body is larger than the vertical distance between the center or the rear end of the engine cover portion and the upper surface of the engine body. Therefore, the front part of the space covered by the vehicle body cover above the engine body has a longer vertical length than the center or rear part in the front-rear direction of the space. For this reason, the heat generated in the space covered by the vehicle body cover above the engine body is more likely to escape forward. That is, the temperature of the front part of the space can be further reduced. Therefore, the influence of heat on the fuel injection device can be further suppressed. Therefore, even if the single combustion chamber main catalyst is enlarged in order to improve the purification performance of the single combustion chamber main catalyst, the influence of the heat of the single combustion chamber main catalyst can be further suppressed.

In the saddle riding type vehicle according to the present invention, it is preferable that the engine cover portion covers at least a part of a left surface or a right surface of the engine body.

The straddle-type vehicle of the present invention includes a head pipe and a vehicle body frame having a main frame extending rearward and downward from the head pipe, and the vehicle body cover covers at least a part of the main frame from above. Preferably, the engine body is disposed below the main frame and is supported by the main frame so as not to swing.

In the saddle riding type vehicle according to the present invention, the exhaust pipe for the single combustion chamber is connected to a catalyst arrangement passage section where the main catalyst for the single combustion chamber is arranged, and an upstream end of the catalyst arrangement passage section. The cross-sectional area perpendicular to the exhaust gas flow direction of the catalyst disposition passage part is larger than the cross-sectional area of the upstream passage part perpendicular to the exhaust gas flow direction. Larger is preferred.

According to this configuration, the single combustion chamber exhaust pipe has the catalyst arrangement passage portion in which the single combustion chamber main catalyst is arranged. Further, an area of a cross section orthogonal to the flow direction of the exhaust gas in the catalyst arrangement passage portion is assumed to be Sa. The area Sa is larger than the area of the cross section orthogonal to the flow direction of at least a part of the upstream passage portion. Therefore, the exhaust gas purification performance by the catalyst can be improved as compared with the case where the area Sa is smaller than or equal to the area of the cross section orthogonal to the flow direction of the exhaust gas in the upstream passage portion.

In the straddle-type vehicle of the present invention, the engine body has a crankcase portion including a crankshaft extending in a left-right direction of the straddle-type vehicle, and at least a part of the single combustion chamber main catalyst includes the It is preferable that the saddle type vehicle is positioned in front of the center line of the crankshaft in the front-rear direction.

According to this configuration, at least a part of the main catalyst for the single combustion chamber is disposed in front of the saddle riding type vehicle from the center line of the crankshaft. Therefore, the single combustion chamber main catalyst is disposed at a position relatively close to the combustion chamber. Therefore, it can suppress that temperature falls before the exhaust gas discharged | emitted from the combustion chamber flows in into the main catalyst for single combustion chambers. That is, a decrease in the temperature of the exhaust gas flowing into the single combustion chamber main catalyst can be suppressed. Therefore, the exhaust gas purification performance of the single combustion chamber main catalyst can be further improved.

In the saddle riding type vehicle according to the present invention, the engine body includes a crankcase portion including a crankshaft extending in a left-right direction of the saddle riding type vehicle, and the single body is seen from the left side. It is preferable that at least a part of the combustion chamber main catalyst is positioned forward of the straight line perpendicular to the center line of the cylinder hole and perpendicular to the center line of the crankshaft in the front-rear direction.

Suppose that a straight line perpendicular to the center line of the cylinder hole and perpendicular to the center line of the crankshaft is a straight line L. The center line of the cylinder hole passes through the center line of the crankshaft. The center line of the cylinder hole extends in the front-rear direction. Therefore, the straight line L extends downward from the crankshaft. At least a part of the single combustion chamber main catalyst is located in front of the straight line L when viewed from the left-right direction. Therefore, the main catalyst for a single combustion chamber is disposed at a position close to the combustion chamber. Therefore, it can suppress that temperature falls before the exhaust gas discharged | emitted from the combustion chamber flows in into the main catalyst for single combustion chambers. That is, a decrease in the temperature of the exhaust gas flowing into the single combustion chamber main catalyst can be suppressed. Therefore, the exhaust gas purification performance of the single combustion chamber main catalyst can be further improved.

In the saddle riding type vehicle according to the present invention, the single catalyst for the single combustion chamber has a path length from the single combustion chamber to the upstream end of the single catalyst for the single combustion chamber. It is preferable to be disposed at a position that is shorter than the path length from the downstream end to the discharge port.

According to this configuration, the path length from one combustion chamber to the upstream end of the single catalyst for the single combustion chamber is shorter than the path length from the downstream end of the main catalyst for the single combustion chamber to the discharge port. Therefore, the main catalyst for a single combustion chamber is disposed at a position close to the combustion chamber. Therefore, it can suppress that temperature falls before the exhaust gas discharged | emitted from the combustion chamber flows in into the main catalyst for single combustion chambers. That is, a decrease in the temperature of the exhaust gas flowing into the single combustion chamber main catalyst can be suppressed. Therefore, the exhaust gas purification performance of the single combustion chamber main catalyst can be further improved.

In the saddle riding type vehicle according to the present invention, the single catalyst for the single combustion chamber has a path length from the single combustion chamber to the upstream end of the single catalyst for the single combustion chamber. It is preferable to arrange at a position shorter than the path length from the downstream end to the downstream end of the single combustion chamber exhaust pipe.

According to this configuration, the path length from one combustion chamber to the upstream end of the single combustion chamber main catalyst is the path length from the downstream end of the single combustion chamber main catalyst to the downstream end of the single combustion chamber exhaust pipe. Shorter than the length. Therefore, the main catalyst for a single combustion chamber is disposed at a position close to the combustion chamber. Therefore, it can suppress that temperature falls before the exhaust gas discharged | emitted from the combustion chamber flows in into the main catalyst for single combustion chambers. That is, a decrease in the temperature of the exhaust gas flowing into the single combustion chamber main catalyst can be suppressed. Therefore, the exhaust gas purification performance of the single combustion chamber main catalyst can be further improved.

In the straddle-type vehicle of the present invention, the exhaust pipe for the single combustion chamber has at least a part upstream of the main combustion catalyst for the single combustion chamber in the flow direction of the exhaust gas so as to cover the inner pipe and the inner pipe. It is preferable that it is composed of a multiple tube with one outer tube.

According to this configuration, at least a part of the exhaust pipe for the single combustion chamber upstream of the main catalyst for the single combustion chamber is configured by multiple tubes. Multiple tubes have a high thermal insulation effect. Therefore, it can suppress that temperature falls before the exhaust gas discharged | emitted from the combustion chamber flows in into the main catalyst for single combustion chambers. That is, a decrease in the temperature of the exhaust gas flowing into the single combustion chamber main catalyst can be suppressed. Therefore, the exhaust gas purification performance of the single combustion chamber main catalyst can be further improved.

In the straddle-type vehicle of the present invention, the single combustion chamber exhaust pipe has a catalyst arrangement passage portion in which the single combustion chamber main catalyst is arranged, and the single cylinder four-stroke engine unit includes the catalyst It is preferable to provide a catalyst protector that covers at least a part of the outer surface of the arrangement passage portion.

According to this configuration, the single combustion chamber exhaust pipe has the catalyst arrangement passage portion in which the single combustion chamber main catalyst is arranged. At least a part of the outer surface of the catalyst arrangement passage portion is covered with a catalyst protector. Therefore, a decrease in the temperature of the single combustion chamber main catalyst can be suppressed. Therefore, the exhaust gas purification performance of the single combustion chamber main catalyst can be further improved.

In the straddle-type vehicle of the present invention, the single cylinder four-stroke engine unit has a flow of exhaust gas more than the single combustion chamber main catalyst in the single combustion chamber cylinder passage or the single combustion chamber exhaust pipe. It is preferable to provide an upstream sub catalyst for a single combustion chamber that is provided upstream in the direction and purifies exhaust gas. The straddle-type vehicle according to any one of claims 1 to 12.

According to this configuration, the single cylinder four-stroke engine unit includes the upstream sub catalyst for the single combustion chamber upstream of the main catalyst for the single combustion chamber. Therefore, in addition to the single combustion chamber main catalyst, the exhaust gas is purified by the single combustion chamber upstream sub-catalyst. Therefore, the exhaust gas purification performance by the catalyst can be further improved. In addition, the single combustion chamber main catalyst and the single combustion chamber upstream sub-catalyst can be reduced in size as compared with the case where only the single combustion chamber main catalyst is provided while maintaining the exhaust gas purification performance of the catalyst. Thereby, at the time of engine start, the upstream sub catalyst for the single combustion chamber can be raised to the activation temperature at an early stage. Therefore, the exhaust gas purification performance by the catalyst can be improved while suppressing an increase in the size of the vehicle in the vertical direction.

In the straddle-type vehicle according to the present invention, the single cylinder four-stroke engine unit is configured such that the single combustion chamber cylinder passage portion, the single combustion chamber exhaust pipe, or the single combustion chamber silencer has the single unit. It is preferable to include a downstream sub catalyst for a single combustion chamber that is provided downstream of the combustion chamber main catalyst in the exhaust gas flow direction and purifies the exhaust gas.

According to this configuration, the single cylinder four-stroke engine unit includes the single combustion chamber upstream sub-catalyst downstream of the single combustion chamber main catalyst. Therefore, in addition to the single combustion chamber main catalyst, the exhaust gas is purified by the single combustion chamber downstream sub-catalyst. Therefore, the exhaust gas purification performance by the catalyst can be further improved. In addition, the single combustion chamber main catalyst and the single combustion chamber downstream sub-catalyst can be reduced in size as compared with the case where only the single combustion chamber main catalyst is provided while maintaining the exhaust gas purification performance of the catalyst. Thereby, at the time of engine starting, the main catalyst for single combustion chambers can be raised to the activation temperature at an early stage. Therefore, the exhaust gas purification performance by the catalyst can be improved while suppressing an increase in the size of the vehicle in the vertical direction.
Moreover, the heat | fever discharge | released from the main catalyst for single combustion chambers can be reduced by size reduction of the main catalyst for single combustion chambers. The single combustion chamber downstream sub-catalyst can be disposed at a position away from the fuel injection device in the front-rear direction. Therefore, the influence of heat on the fuel injection device can be further suppressed.

According to the present invention, it is possible to suppress the increase in size of the vehicle in the vertical direction while reducing the exhaust gas purification performance by the catalyst, and to reduce the influence of the heat of the catalyst.

1 is a side view of a motorcycle according to an embodiment of the present invention. FIG. 2 is a side view of the motorcycle of FIG. 1 with a vehicle body cover and the like removed. FIG. 3 is a bottom view of FIG. 2. FIG. 2 is a control block diagram of the motorcycle of FIG. 1. FIG. 2 is a schematic diagram showing an engine body and an exhaust system of the motorcycle shown in FIG. 1. FIG. 2 is a front view of a single cylinder four-stroke engine unit and a vehicle body cover of the motorcycle of FIG. 1. FIG. 2 is a drawing in which a front view of a vehicle body cover is combined with a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is a partially enlarged view of FIG. 2. FIG. 6 is a partially enlarged view of a side view of a motorcycle according to another embodiment of the present invention. FIG. 6 is a schematic diagram showing an engine body and an exhaust system of a motorcycle according to another embodiment of the present invention. FIG. 6 is a partial cross-sectional view of an exhaust pipe applied to a motorcycle according to another embodiment of the present invention. FIG. 6 is a partially enlarged view of a side view of a motorcycle according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. An example in which the saddle riding type vehicle of the present invention is applied to a motorcycle will be described. In the following description, front, rear, left, and right mean front, rear, left, and right, respectively, as viewed from a motorcycle occupant. However, it is assumed that the motorcycle is placed on a horizontal ground. Reference numerals F, Re, L, and R attached to the drawings represent front, rear, left, and right, respectively.

[overall structure]
FIG. 1 is a side view of the motorcycle according to the present embodiment. FIG. 2 is a side view of the motorcycle according to the present embodiment with the vehicle body cover and the like removed. FIG. 3 is a bottom view of the motorcycle according to the present embodiment with the vehicle body cover and the like removed. FIG. 5 is a schematic diagram showing an engine and an exhaust system of the motorcycle according to the present embodiment. FIG. 8 is a partially enlarged view of FIG.

The saddle riding type vehicle of the present embodiment is a so-called underbone type motorcycle 1. As shown in FIG. 2, the motorcycle 1 includes a body frame 2. The vehicle body frame 2 includes a head pipe 3, a main frame 4, and a seat rail 5. The main frame 4 extends rearward and downward from the head pipe 3. The seat rail 5 extends rearward and upward from the middle part of the main frame 4.

A steering shaft is rotatably inserted into the head pipe 3. A handle 7 (see FIG. 1) is provided on the upper portion of the steering shaft. A display device (not shown) is disposed in the vicinity of the handle 7. The display device displays vehicle speed, engine speed, various warnings, and the like.

A pair of left and right front forks 6 are supported at the bottom of the steering shaft. An axle 8 a is fixed to the lower end portion of the front fork 6. A front wheel 8 is rotatably attached to the axle 8a. A fender 10 is provided above and behind the front wheel 8.

A seat 9 (see FIG. 1) is supported on the seat rail 5. As shown in FIG. 2, the seat rail 5 is connected to upper ends of a pair of left and right rear cushion units 13. The lower end portion of the rear cushion unit 13 is supported by the rear portions of the pair of left and right rear arms 14. The front portion of the rear arm 14 is connected to the vehicle body frame 2 via a pivot shaft 14a. The rear arm 14 can swing up and down around the pivot shaft 14a. A rear wheel 15 is supported at the rear portion of the rear arm 14.

As shown in FIG. 2, an engine body 20 is disposed below the main frame 4. The engine body 20 is supported by the body frame 2. The engine body 20 is supported by the main frame 4 so as not to swing. Specifically, the upper part of the engine body 20 is fixed to the bracket 4a provided on the main frame 4 by bolts 4b. More specifically, an upper front portion of a crankcase portion 21 (to be described later) of the engine body 20 is fixed to the bracket 4a. The rear portion of the engine body 20 is also fixed to another bracket provided on the vehicle body frame 2. An air cleaner 32 is disposed below the main frame 4 and above the engine body 20.

As shown in FIG. 1, the motorcycle 1 has a vehicle body cover 11 that covers the vehicle body frame 2 and the like. The vehicle body cover 11 includes a main cover 11b and a front cover 11a. The front cover 11 a is disposed in front of the head pipe 3. The main cover 11 b is disposed behind the head pipe 3. The main cover 11b covers the main frame 4 from above. The main cover 11b covers the seat rail 5 from above. The main cover 11b and the front cover 11a cover the left and right sides of the front portion of the engine body 20. The front cover 11 a covers the left and right sides of the air cleaner 32.

An opening 17 is formed in the front portion of the vehicle body cover 11. The opening 17 is formed in the front cover 11a. As shown in FIG. 6, the opening 17 is formed in an inverted U shape when viewed from the front. FIG. 6 is a front view of the single-cylinder four-stroke engine unit and the vehicle body cover of the motorcycle. The maximum width in the left-right direction of the opening 17 is larger than the width in the left-right direction of the front wheel 8. Further, the maximum width in the left-right direction of the opening 17 is larger than the width in the left-right direction of the fender 10. Further, the upper end of the opening 17 is located above the front wheel 8. The upper end of the opening 17 is located above the engine body 20. The lower end of the opening 17 is substantially the same height as the lower end of the engine body 20. As shown in FIG. 1, most (part) of the engine body 20 is located behind the opening 17. Most of the air cleaner 32 is located behind the opening 17.

As shown in FIG. 1, the vehicle body cover 11 includes an engine cover portion 16. The engine cover portion 16 covers at least a part of the upper surface of the engine body 20. The engine cover portion 16 is formed such that both end portions in the left-right direction are located below the center portion 16a in the left-right direction.

As shown in FIG. 7, the cross section orthogonal to the front-rear direction of the engine cover portion 16 is formed in an inverted U shape. 7 is a drawing in which the front view of the vehicle body cover 11 is combined with the cross-sectional view taken along the line AA in FIG. The engine cover portion 16 is formed symmetrically. The center 16 a in the left-right direction of the engine cover part 16 forms the upper end of the engine cover part 16. Further, the engine cover portion 16 covers a part of the left side and the right side of the engine body 20. More specifically, the engine cover portion 16 covers a part of a left surface and a right surface of a cylinder portion 22 described later of the engine body 20.

As shown in FIG. 1, the maximum vertical distance between the front end of the engine cover portion 16 and the upper surface of the engine body 20 is D1. The distance D 1 is a vertical distance between the front end of the center 16 a in the left-right direction of the engine cover 16 and the upper surface of the engine body 20. The maximum vertical separation distance between the center of the engine cover portion 16 in the front-rear direction and the upper surface of the engine body 20 is defined as D2. The distance D 2 is a vertical distance between the center in the front-rear direction of the center 16 a in the left-right direction of the engine cover 16 and the upper surface of the engine body 20. A maximum distance in the vertical direction between the rear end of the engine cover portion 16 and the upper surface of the engine body 20 is defined as D3. The distance D 1 is a vertical distance between the front end of the center 16 a in the left-right direction of the engine cover portion 16 and the upper surface of the engine body 20. The distance D1 is larger than the distance D2. The distance D1 is larger than the distance D3. The upper end (the center 16a in the left-right direction) of the engine cover portion 16 extends rearward and downward as a whole.

As shown in FIG. 1, the body cover 11 has a lower portion between the seat 9 and the head pipe 3. Further, as shown in FIG. 2, the main frame 4 has a lower portion between the seat 9 and the head pipe 3. As a result, the underbone type motorcycle 1 has a recess 12 formed behind the head pipe 3, ahead of the seat 9 and above the main frame 4 when viewed from the left-right direction of the vehicle. The recess 12 makes it easier for the occupant to straddle the vehicle body.

The motorcycle 1 has a single-cylinder four-stroke engine unit 19. The single-cylinder four-stroke engine unit 19 includes an engine body 20, an air cleaner 32, an intake passage 33 (single combustion chamber intake passage), an exhaust pipe 34, a silencer 35, and a main catalyst 39 (single A combustion chamber main catalyst) and an upstream oxygen detection member 37. Although details will be described later, the main catalyst 39 is disposed in the exhaust pipe 34. The main catalyst 39 purifies the exhaust gas flowing through the exhaust pipe 34. The upstream oxygen detection member 37 is disposed upstream of the main catalyst 39 in the exhaust pipe 34. The upstream oxygen detection member 37 detects the oxygen concentration in the exhaust gas flowing through the exhaust pipe 34.

The engine body 20 is a single-cylinder four-stroke engine. As shown in FIGS. 2 and 3, the engine main body 20 includes a crankcase portion 21 and a cylinder portion 22. The cylinder part 22 extends forward from the crankcase part 21.

The crankcase portion 21 includes a crankcase body 23, a crankshaft 27 accommodated in the crankcase body 23, a transmission mechanism, and the like. Hereinafter, the center line Cr1 of the crankshaft 27 is referred to as a crankshaft line Cr1. The crank axis Cr1 extends in the left-right direction. Lubricating oil is stored in the crankcase body 23. Such oil is conveyed by an oil pump (not shown) and circulates in the engine body 20.

The cylinder part 22 has a cylinder body 24, a cylinder head 25, a head cover 26, and components housed therein. As shown in FIG. 2, the cylinder body 24 is connected to the front portion of the crankcase body 23. The cylinder head 25 is connected to the front part of the cylinder body 24. The head cover 26 is connected to the front part of the cylinder head 25.

As shown in FIG. 5, a cylinder hole 24 a is formed in the cylinder body 24. A piston 28 is accommodated in the cylinder hole 24a so as to be able to reciprocate. The piston 28 is connected to the crankshaft 27 via a connecting rod 28a. Hereinafter, the center line Cy1 of the cylinder hole 24a is referred to as a cylinder axis Cy1. As shown in FIG. 2, the engine body 20 is arranged such that the cylinder axis Cy 1 extends in the front-rear direction (horizontal direction). More specifically, the direction of the cylinder axis Cy1 from the crankcase portion 21 toward the cylinder portion 22 is front-upward. The inclination angle θ1 (see FIG. 8) of the cylinder axis Cy1 with respect to the horizontal direction is not less than 0 degrees and not more than 45 degrees. The cylinder axis Cy 1 passes through the center of the motorcycle 1 in the left-right direction. Note that the center in the left-right direction of the motorcycle 1 is a straight line position passing through the center in the left-right direction of the front wheel 8 and the center in the left-right direction of the rear wheel 15 when viewed from above and below. The cylinder axis Cy1 may be shifted from the center in the left-right direction of the motorcycle 1 to the right or left.

As shown in FIG. 5, one combustion chamber 29 is formed inside the cylinder portion 22. The combustion chamber 29 is formed by the inner surface of the cylinder hole 24 a of the cylinder body 24, the cylinder head 25, and the piston 28. That is, a part of the combustion chamber 29 is partitioned by the inner surface of the cylinder hole 24a. In the combustion chamber 29, a tip end portion of a spark plug (not shown) is arranged. The spark plug ignites a mixed gas of fuel and air in the combustion chamber 29. As shown in FIG. 2, the combustion chamber 29 is located in front of the crank axis Cr1. This is paraphrased as follows. A straight line passing through the crank axis Cr1 and extending in parallel with the vertical direction is defined as L1. When viewed from the left-right direction, the combustion chamber 29 is disposed in front of the straight line L1.

As shown in FIG. 5, the cylinder head 25 is formed with a cylinder intake passage portion 30 (a single combustion chamber cylinder intake passage portion) and a cylinder exhaust passage portion 31 (a single combustion chamber cylinder exhaust passage portion). ing. In the present specification, the “passage part” is a structure that forms a space (path) through which gas or the like passes. In the cylinder head 25, an intake port 30 a and an exhaust port 31 a are formed in a wall portion that forms the combustion chamber 29. The cylinder intake passage portion 30 extends from the intake port 30 a to an intake port formed on the outer surface (upper surface) of the cylinder head 25. The cylinder exhaust passage 31 extends from the exhaust port 31 a to a discharge port formed on the outer surface (lower surface) of the cylinder head 25. Air supplied to the combustion chamber 29 passes through the cylinder intake passage portion 30. The exhaust gas discharged from the combustion chamber 29 passes through the cylinder exhaust passage portion 31.

The cylinder intake passage 30 is provided with an intake valve V1. An exhaust valve V 2 is disposed in the cylinder exhaust passage portion 31. The intake valve V 1 and the exhaust valve V 2 are operated by a valve operating mechanism (not shown) that is linked to the crankshaft 27. The intake port 30a is opened and closed by the movement of the intake valve V1. The exhaust port 31a is opened and closed by the movement of the exhaust valve V2. An intake passage 33 is connected to the upstream end (suction port) of the cylinder intake passage 30. An exhaust pipe 34 is connected to the downstream end (discharge port) of the cylinder exhaust passage portion 31. The path length of the cylinder exhaust passage portion 31 is a1.

[Configuration of intake system]
Hereinafter, the intake system of the motorcycle 1 of the present embodiment will be described. In the description of the intake system in the present specification, the upstream means the upstream in the flow direction of the air supplied to the combustion chamber 29. Further, “downstream” means downstream in the flow direction of the air supplied to the combustion chamber 29.

The downstream end of the intake passage portion 33 is connected to the upstream end of the cylinder intake passage portion 30. The upstream end of the intake passage portion 33 is connected to the air cleaner 32. As shown in FIG. 6, when viewed from the front, the intake passage portion 33 extends from the upper surface of the cylinder portion 22 as follows. The intake passage portion 33 extends upward from the upper surface of the cylinder portion 22 and then bends and extends upward. After that, it bends and extends upward. In addition, as shown in FIG. 8, the intake passage portion 33 is disposed above the engine body 20. Further, at least a part of the intake passage portion 33 is disposed above the upper surface of the engine body 20.

The intake passage portion 33 is disposed between the engine cover portion 16 and the upper surface of the engine body 20. As shown in FIG. 8, let L3 be a straight line that passes through the rearmost end of the intake passage portion 33 and extends in parallel with the vertical direction. The straight line L3 is located behind the opening 17. That is, the rearmost end of the intake passage portion 33 is disposed behind the opening 17 of the vehicle body cover 11.

As shown in FIG. 9, the intake passage 33 is provided with an injector 48 (fuel injection device). The injector 48 injects fuel in the cylinder intake passage portion 30. That is, the injector 48 injects fuel into the air sucked from the upstream end of the intake passage portion 33. The injector 48 may be configured to inject fuel in the intake passage portion 33.

The injector 48 is provided in the front portion of the intake passage portion 33. A part of the injector 48 is disposed in front of the intake passage portion 33. The injector 48 is disposed in front of the straight line L3. That is, the injector 48 is disposed in front of the rear end of the intake passage portion 33.

As shown in FIGS. 2 and 8, a straight line that passes through the foremost end of the main catalyst 39 and extends in parallel with the vertical direction is L4. The injector 48 is disposed in front of the straight line L4. That is, the injector 48 is disposed in front of the main catalyst 39. The injector 48 is disposed behind the opening 17 of the vehicle body cover 11. In addition, at least a portion of the injector 48 is disposed below the air cleaner 32.

As shown in FIG. 6, when the single-cylinder four-stroke engine unit 19 and the vehicle body cover 11 are viewed from the front, a part of the injector 48 is visible in the opening 17 of the vehicle body cover 11. That is, the entire injector 48 is not hidden by the vehicle body cover 11 and the single cylinder four-stroke engine unit 19 when viewed from the front. When viewed from the front, a part (lower part) of the injector 48 is hidden by the cylinder part 22 (engine body 20).

A throttle body 50 is provided in the middle of the intake passage portion 33. A throttle valve 51 is built in the throttle body 50. That is, the throttle valve 51 is disposed in the intake passage portion 33. The amount of air supplied to the engine body 20 is adjusted by changing the opening of the throttle valve 51.

The air cleaner 32 is disposed above the front part of the cylinder part 22 (engine body 20). The intake passage portion 33 is connected to the rear portion of the air cleaner 32. The air cleaner 32 purifies the air supplied to the engine body 20. The air purified by passing through the air cleaner 32 is supplied to the engine body 20 through the intake passage portion 33.

[Exhaust system configuration]
Hereinafter, the exhaust system of the motorcycle 1 of the present embodiment will be described. In the description of the exhaust system in the present specification, upstream means upstream in the flow direction of exhaust gas. Further, the downstream means downstream in the flow direction of the exhaust gas. In the description of the exhaust system of the present specification, the path direction is the direction in which exhaust gas flows.

As described above, the single cylinder four-stroke engine unit 19 includes the engine body 20, the exhaust pipe 34, the silencer 35, the main catalyst 39, and the upstream oxygen detection member 37. The silencer 35 has a discharge port 35e facing the atmosphere. A path from the combustion chamber 29 to the discharge port 35e is an exhaust path 41 (see FIG. 5). The exhaust path 41 is formed by the cylinder exhaust passage portion 31, the exhaust pipe 34, and the silencer 35. The exhaust path 41 is a space through which exhaust gas passes.

As shown in FIG. 5, the upstream end portion of the exhaust pipe 34 is connected to the cylinder exhaust passage portion 31. The downstream end of the exhaust pipe 34 is connected to a silencer 35. A catalyst unit 38 is provided in the middle of the exhaust pipe 34. A portion of the exhaust pipe 34 upstream from the catalyst unit 38 is referred to as an upstream exhaust pipe 34a. A portion of the exhaust pipe 34 downstream from the catalyst unit 38 is referred to as a downstream exhaust pipe 34b. In FIG. 5, the exhaust pipe 34 and the intake passage portion 33 are drawn in a straight line for simplification, but the exhaust pipe 34 and the intake passage portion 33 are not in a straight line.

As shown in FIG. 3, the exhaust pipe 34 is provided in the right part of the motorcycle 1. As shown in FIG. 2, a part of the exhaust pipe 34 is disposed below the engine body 20 when viewed from the left-right direction. Specifically, a portion including the upstream end of the exhaust pipe 34 is disposed below the engine body 20 when viewed from the left-right direction. A straight line passing through the lowermost end of the engine body 20 and extending in parallel with the front-rear direction is denoted as L5. A part of the exhaust pipe 34 is disposed below the straight line L5. That is, a part of the exhaust pipe 34 is disposed below the lower surface of the engine body 20. The exhaust pipe 34 is disposed behind the opening 17 of the vehicle body cover 11. As shown in FIG. 2, a part of the exhaust pipe 34 is positioned below the crank axis Cr1.

The exhaust pipe 34 has two bent portions. Of the two bent portions, the upstream bent portion is simply referred to as an upstream bent portion. Of the two bent portions, the downstream bent portion is simply referred to as a downstream bent portion. As shown in FIG. 2, the upstream bent portion changes the flow direction of the exhaust gas from the direction extending in the vertical direction to the direction extending in the front-rear direction when viewed from the left-right direction. More specifically, the bent portion changes the flow direction of the exhaust gas from downward to rearward as viewed from the left-right direction. Further, as shown in FIG. 3, the upstream bent portion changes the flow direction of the exhaust gas when viewed from below. As shown in FIG. 2, the downstream bent portion changes the flow direction of the exhaust gas from the rear upward direction to the rear direction as viewed from the left-right direction. Moreover, as shown in FIG. 3, the downstream bent portion changes the flow direction of the exhaust gas from the rear right direction to the rear direction as viewed from below. A portion slightly downstream from the downstream bent portion is positioned below the crank axis Cr1. The main catalyst 39 is disposed between the two bent portions.

The exhaust gas discharged from the downstream end of the exhaust pipe 34 flows into the silencer 35. The silencer 35 is connected to the exhaust pipe 34. The silencer 35 is configured to suppress pulsating waves of exhaust gas. Thereby, the silencer 35 can reduce the volume of the sound (exhaust sound) generated by the exhaust gas. In the silencer 35, a plurality of expansion chambers and a plurality of pipes communicating the expansion chambers are provided. The downstream end of the exhaust pipe 34 is disposed in the expansion chamber of the silencer 35. At the downstream end of the silencer 35, a discharge port 35e facing the atmosphere is provided. As shown in FIG. 5, the path length of the exhaust path from the downstream end of the exhaust pipe 34 to the discharge port 35e is defined as e1. The path length of the expansion chamber in the silencer 35 is the length of the path connecting the center of the expansion chamber inlet to the center of the expansion chamber outlet at the shortest distance. The exhaust gas that has passed through the silencer 35 is discharged to the atmosphere from the discharge port 35e. As shown in FIG. 2, the discharge port 35e is located behind the crank axis Cr1.

The main catalyst 39 is disposed in the exhaust pipe 34. The catalyst unit 38 includes a cylindrical casing 40 and a main catalyst 39. The upstream end of the casing 40 is connected to the upstream exhaust pipe 34a. The downstream end of the casing 40 is connected to the downstream exhaust pipe 34b. The casing 40 constitutes a part of the exhaust pipe 34. The main catalyst 39 is fixed inside the casing 40. The exhaust gas is purified by passing through the main catalyst 39. All exhaust gas discharged from the exhaust port 31 a of the combustion chamber 29 passes through the main catalyst 39. The main catalyst 39 purifies the exhaust gas discharged from the combustion chamber 29 most in the exhaust path 41.

The main catalyst 39 is a so-called three-way catalyst. The three-way catalyst is removed by oxidizing or reducing three substances of hydrocarbon, carbon monoxide, and nitrogen oxide contained in the exhaust gas. The three-way catalyst is one type of redox catalyst. The main catalyst 39 has a base material and a catalytic material attached to the surface of the base material. The catalytic material has a support and a noble metal. The carrier is provided between the noble metal and the substrate. The carrier carries a noble metal. This noble metal purifies the exhaust gas. Examples of the noble metal include platinum, palladium, and rhodium that remove hydrocarbons, carbon monoxide, and nitrogen oxides, respectively.

The main catalyst 39 has a porous structure. The porous structure refers to a structure in which a hole is formed in a cross section perpendicular to the path direction of the exhaust path 41. An example of the porous structure is a honeycomb structure. The main catalyst 39 has a plurality of holes sufficiently narrower than the path width of the upstream exhaust pipe 34a.

The main catalyst 39 may be a metal base catalyst or a ceramic base catalyst. The metal base catalyst is a catalyst whose base is made of metal. The ceramic base catalyst is a catalyst whose base is made of ceramic. The base material of the metal base catalyst is formed, for example, by alternately stacking and winding metal corrugated plates and metal flat plates. The base material of the ceramic base catalyst is, for example, a honeycomb structure.

As shown in FIG. 5, the length of the main catalyst 39 in the path direction is c1. The maximum width in the direction perpendicular to the path direction of the main catalyst 39 is w1. The length c1 of the main catalyst 39 is longer than the maximum width w1 of the main catalyst 39. The cross-sectional shape orthogonal to the path direction of the main catalyst 39 is, for example, a circular shape. The cross-sectional shape may be a shape in which the horizontal length is longer than the vertical length.

As shown in FIG. 5, the casing 40 includes a catalyst arrangement passage portion 40b, an upstream passage portion 40a, and a downstream passage portion 40c. The main catalyst 39 is arranged in the catalyst arrangement passage portion 40b. In the path direction, the upstream end and the downstream end of the catalyst arrangement passage portion 40 b are at the same positions as the upstream end and the downstream end of the main catalyst 39, respectively. The area of the cross section perpendicular to the path direction of the catalyst arrangement passage portion 40b is substantially constant in the path direction. The upstream passage portion 40a is connected to the upstream end of the catalyst arrangement passage portion 40b. The downstream passage portion 40c is connected to the upstream end of the catalyst arrangement passage portion 40b.

The upstream passage portion 40a is at least partially tapered. The tapered portion has an inner diameter that increases toward the downstream. The downstream passage portion 40c is at least partially tapered. The tapered portion has an inner diameter that decreases toward the downstream. The area of the cross section orthogonal to the path direction of the catalyst arrangement passage portion 40b is S1. The area of the cross section orthogonal to the route direction of at least a part of the upstream passage portion 40a is smaller than the area S1. Here, at least a part of the upstream passage portion 40a includes the upstream end of the upstream passage portion 40a. The area of the cross section perpendicular to the path direction of at least a part of the downstream passage portion 40c is smaller than the area S1. Here, at least a part of the downstream passage portion 40c includes the downstream end of the downstream passage portion 40c.

As shown in FIGS. 2 and 8, the main catalyst 39 is disposed below the engine body 20 when viewed from the left-right direction. Further, as shown in FIG. 2, a part of the main catalyst 39 is located below the straight line L5. That is, a part of the main catalyst 39 is disposed below the lower surface of the engine body 20. As shown in FIG. 3, the main catalyst 39 does not overlap the engine body 20 when viewed from below. Note that the main catalyst 39 may overlap the engine body 20 as viewed from below.

2 and 3, the main catalyst 39 is disposed in front of the crank axis Cr1. That is, the main catalyst 39 is disposed in front of the straight line L1 when viewed from the left-right direction. As described above, the straight line L1 is a straight line that passes through the crank axis Cr1 and extends parallel to the vertical direction. Of course, the upstream end of the main catalyst 39 is also arranged in front of the crank axis Cr1. Further, the main catalyst 39 is located in front (downward) of the cylinder axis Cy1 when viewed from the left-right direction.

As shown in FIG. 2, let L2 be a straight line that is orthogonal to the cylinder axis Cy1 and orthogonal to the crank axis Cr1. When viewed from the left-right direction, the main catalyst 39 is located in front of the straight line L2.

As shown in FIG. 5, the path length from the upstream end of the exhaust pipe 34 to the upstream end of the main catalyst 39 is b1. The path length b 1 is the path length of the passage portion including the upstream exhaust pipe 34 a and the upstream passage portion 40 a of the catalyst unit 38. In other words, the path length b1 is the path length from the downstream end of the cylinder exhaust passage portion 31 to the upstream end of the main catalyst 39. The path length from the downstream end of the main catalyst 39 to the downstream end of the exhaust pipe 34 is defined as d1. The path length d1 is the path length of the passage portion including the downstream passage portion 40c and the downstream exhaust pipe 34b of the catalyst unit 38. The path length from the combustion chamber 29 to the upstream end of the main catalyst 39 is a1 + b1. The path length from the downstream end of the main catalyst 39 to the discharge port 35e is d1 + e1.

The main catalyst 39 is disposed at a position where the path length a1 + b1 is shorter than the path length d1 + e1. The main catalyst 39 is disposed at a position where the path length a1 + b1 is shorter than the path length d1. Further, the main catalyst 39 is disposed at a position where the path length b1 is shorter than the path length d1.

The upstream oxygen detection member 37 is disposed in the exhaust pipe 34. The upstream oxygen detection member 37 is disposed upstream of the main catalyst 39. The upstream oxygen detection member 37 is a sensor that detects the concentration of oxygen contained in the exhaust gas. The upstream oxygen detection member 37 may be an oxygen sensor that detects whether the oxygen concentration is higher or lower than a predetermined value. Further, the upstream oxygen detection member 37 may be a sensor (for example, an A / F sensor: Air Fuel ratio sensor) that outputs a detection signal representing the oxygen concentration in a plurality of steps or linearly. The upstream oxygen detection member 37 has one end (detection unit) disposed in the exhaust pipe 34 and the other end disposed outside the exhaust pipe 34. The detection unit of the upstream oxygen detection member 37 can detect the oxygen concentration when it is heated to a high temperature and activated. The detection result of the upstream oxygen detection member 37 is output to the electronic control unit 45.

Next, control of the single cylinder four-stroke engine unit 19 will be described. FIG. 4 is a control block diagram of the motorcycle according to the present embodiment.

As shown in FIG. 4, the single-cylinder four-stroke engine unit 19 includes an engine speed sensor 46a, a throttle opening sensor 46b (throttle position sensor), an engine temperature sensor 46c, an intake pressure sensor 46d, and an intake temperature sensor 46e. The engine rotation speed sensor 46a detects the rotation speed of the crankshaft 27, that is, the engine rotation speed. The throttle opening sensor 46b detects the opening of the throttle valve 51 (hereinafter referred to as the throttle opening) by detecting the position of the throttle valve 51. The engine temperature sensor 46c detects the temperature of the engine body. The intake pressure sensor 46d detects the pressure (intake pressure) in the intake passage portion 33. The intake air temperature sensor 46e detects the temperature of air in the intake passage portion 33 (intake air temperature).

The single-cylinder four-stroke engine unit 19 includes an electronic control unit (ECU: Electronic Control Unit) 45 that controls the engine body 20. The electronic control unit 45 is connected to various sensors such as an engine speed sensor 46a, an engine temperature sensor 46c, a throttle opening sensor 46b, an intake pressure sensor 46d, an intake air temperature sensor 46e, and a vehicle speed sensor. The electronic control unit 45 is connected to an ignition coil 47, an injector 48, a fuel pump 49, a display device (not shown), and the like. The electronic control unit 45 includes a control unit 45a and an operation instruction unit 45b. The operation instructing unit 45b includes an ignition drive circuit 45c, an injector drive circuit 45d, and a pump drive circuit 45e.

The ignition drive circuit 45c, the injector drive circuit 45d, and the pump drive circuit 45e drive the ignition coil 47, the injector 48, and the fuel pump 49, respectively, in response to a signal from the control unit 45a. When the ignition coil 47 is driven, a spark discharge is generated at the spark plug, and the mixed gas is ignited. The fuel pump 49 is connected to the injector 48 via a fuel hose. When the fuel pump 49 is driven, fuel in a fuel tank (not shown) is pumped to the injector 48.

The control unit 45a is, for example, a microcomputer. The controller 45a controls the ignition drive circuit 45c, the injector drive circuit 45d, and the pump drive circuit 45e based on the signal from the upstream oxygen detection member 37, the signal from the engine rotation speed sensor 46a, and the like. The controller 45a controls the ignition timing by controlling the ignition drive circuit 45c. The controller 45a controls the fuel injection amount by controlling the injector drive circuit 45d and the pump drive circuit 45e.

In order to increase the combustion efficiency and the purification efficiency of the main catalyst 39, the air-fuel ratio of the air-fuel mixture in the combustion chamber 29 is preferably the stoichiometric air-fuel ratio (stoichiometry). The controller 45a increases or decreases the fuel injection amount as necessary.

Hereinafter, an example of fuel injection amount control (combustion control) by the controller 45a will be described.
First, the controller 45a calculates the basic fuel injection amount based on signals from the engine speed sensor 46a, the throttle opening sensor 46b, the engine temperature sensor 46c, and the intake pressure sensor 46d. Specifically, the intake air amount is calculated using a map in which the intake air amount is associated with the throttle opening and the engine rotational speed, and a map in which the intake air amount is associated with the intake pressure and the engine rotational speed. Ask. Then, based on the intake air amount obtained from the map, the basic fuel injection amount that can achieve the target air-fuel ratio is determined. When the throttle opening is small, a map in which the intake air amount is associated with the intake pressure and the engine speed is used. On the other hand, when the throttle opening is large, a map in which the intake air amount is associated with the throttle opening and the engine speed is used.

Further, the control unit 45a calculates a feedback correction value for correcting the basic fuel injection amount based on the signal from the upstream oxygen detection member 37. Specifically, first, based on the signal from the upstream oxygen detection member 37, it is determined whether the air-fuel mixture is lean or rich. Note that rich means that the fuel is excessive with respect to the stoichiometric air-fuel ratio. Lean means a state where air is excessive with respect to the stoichiometric air-fuel ratio. When determining that the air-fuel mixture is lean, the control unit 45a calculates a feedback correction value so that the next fuel injection amount increases. On the other hand, when determining that the air-fuel mixture is rich, the control unit 45a obtains a feedback correction value so that the next fuel injection amount is reduced.

Further, the control unit 45a calculates a correction value for correcting the basic fuel injection amount based on the engine temperature, the outside air temperature, the outside air pressure, and the like. Furthermore, the control unit 45a calculates a correction value according to the transient characteristics during acceleration and deceleration.

The control unit 45a calculates the fuel injection amount based on the basic fuel injection amount and a correction value such as a feedback correction value. Based on the fuel injection amount thus determined, the fuel pump 49 and the injector 48 are driven. Thus, the electronic control unit 45 processes the signal of the upstream oxygen detection member 37. The electronic control unit 45 performs combustion control based on the signal from the upstream oxygen detection member 37.

The configuration of the motorcycle 1 according to this embodiment has been described above. The motorcycle 1 of the present embodiment has the following characteristics.

The cylinder portion 22 (horizontal cylinder portion) is provided so that the cylinder axis Cy1 extends in the front-rear direction of the motorcycle 1. Accordingly, at least a part of the intake passage portion 33 is disposed above the engine body 20. Further, at least a part of the exhaust pipe 34 is disposed below the engine body 20. At least a part of the main catalyst 39 is disposed below the engine body 20. Therefore, the hot air from the main catalyst 39 rises to the upper part of the engine body 20 through the periphery of the engine body 20.

At least a part of the upper surface of the engine body 20 is covered by the engine cover portion 16 of the vehicle body cover 11. Further, the engine cover portion 16 disposed above the engine body 20 is formed such that both end portions in the left-right direction are located below the center 16a in the left-right direction. Further, at least a part of the exhaust pipe 34 is disposed behind the opening 17 at the front portion of the vehicle body cover 11. Therefore, the heat that has risen from the main catalyst 39 and the engine main body 20 tends to go into the space covered by the vehicle body cover 11 above the engine main body 20.

In addition, the rearmost end of the intake passage portion 33 is disposed behind the opening 17 of the vehicle body cover 11. At least a part of the intake passage portion 33 is disposed between the engine cover portion 16 and the upper surface of the engine body 20. That is, at least a part of the intake passage portion 33 is disposed in a space covered by the vehicle body cover 11 above the engine body 20. As described above, in the space covered by the vehicle body cover 11 above the engine body 20, the heat that has risen from the main catalyst 39 and the engine body 20 is likely to be generated. However, the vehicle body cover 11 has an opening 17 formed at the front thereof. Therefore, the front part of the space covered with the vehicle body cover 11 above the engine body 20 is open to the front of the vehicle. For this reason, the heat generated in the space covered by the vehicle body cover 11 above the engine body 20 tends to escape forward. That is, the temperature at the front of the space is relatively low. The injector 48 is disposed in front of the rear end of the intake passage portion 33. That is, the injector 48 is disposed at a position close to the opening 17 of the vehicle body cover 11. Further, when the single-cylinder four-stroke engine unit and the vehicle body cover 11 are viewed from the front, at least a part of the injector 48 is visible in the opening 17 of the vehicle body cover 11. Therefore, even if heat is generated in the space covered by the vehicle body cover 11 above the engine body 20, the influence of heat on the injector 48 can be suppressed. That is, even if hot air rises from the main catalyst 39, the influence of heat on the injector 48 can be suppressed. Therefore, even if the main catalyst 39 is enlarged to improve the purification performance of the main catalyst 39, the influence of the heat of the main catalyst 39 can be suppressed.

Thus, by devising the arrangement position of the injector 48, the influence of the heat of the main catalyst 39 on the injector 48 can be suppressed. Therefore, it is possible to simplify the structure for heat insulation so that the heat of the main catalyst 39 does not affect the surroundings. Therefore, even if the main catalyst 39 is enlarged in order to improve the purification performance by the main catalyst 39, the vehicle can be prevented from being enlarged in the vertical direction.

As described above, the motorcycle 1 according to the present invention can improve the exhaust gas purification performance of the catalyst, suppress the increase in size of the vehicle in the vertical direction, and reduce the influence of the heat of the catalyst.

A part of the injector 48 is disposed in front of the intake passage portion 33. Thereby, the injector 48 is disposed at a position closer to the opening 17 at the front portion of the vehicle body cover 11. Therefore, even if hot air rises from the main catalyst 39, the influence of heat on the injector 48 can be further suppressed. Therefore, even if the main catalyst 39 is enlarged to improve the purification performance of the main catalyst 39, the influence of the heat of the main catalyst 39 can be further suppressed.

Further, the engine cover portion 16 covers at least a part of the left side or the right side of the engine body 20. Therefore, heat is more likely to be generated in the space above the engine body 20. Further, at least a part of the air cleaner 32 is disposed between the engine body 20 and the engine cover portion 16. Therefore, the air cleaner 32 blocks the heat in the space above the engine body 20 from escaping forward. Therefore, heat is easily generated by the space covered by the vehicle body cover 11 above the engine body 20. In spite of such a situation, the influence of heat on the injector 48 can be reduced by devising the arrangement position of the injector 48 as described above.

The engine cover portion is formed such that the distance D1 is larger than the distance D2 or the distance D3. The distance D1 is a vertical distance between the center of the engine cover portion 16 in the front-rear direction and the upper surface of the engine body 20. The distance D 2 is a vertical distance between the center of the engine cover portion 16 in the front-rear direction and the upper surface of the engine body 20. The distance D3 is a vertical distance between the rear end of the engine cover portion 16 and the upper surface of the engine body 20. Accordingly, the front portion of the space covered by the vehicle body cover 11 above the engine body 20 has a longer vertical length than the center or the rear portion in the front-rear direction of the space. For this reason, the heat generated in the space covered by the vehicle body cover 11 above the engine body 20 is more likely to escape forward. That is, the temperature of the front part of the space can be further reduced. Therefore, the influence of heat on the injector 48 can be further suppressed. Therefore, even if the main catalyst 39 is enlarged to improve the purification performance of the main catalyst 39, the influence of the heat of the main catalyst 39 can be further suppressed.

Further, at least a part of the injector 48 is disposed in front of the main catalyst 39. Therefore, the injector 48 is not easily affected by the heat rising from the main catalyst 39.

The cross-sectional area S1 of the catalyst arrangement passage part 40b is larger than at least a part of the cross-sectional area of the upstream passage part 40a. Therefore, compared with the case where the cross-sectional area S1 is smaller than or equal to the area of the cross section perpendicular to the flow direction of the exhaust gas in the upstream passage portion 40a, the exhaust gas purification performance by the catalyst can be improved.

At least a part of the main catalyst 39 is disposed in front of the motorcycle 1 in the front-rear direction of the motorcycle 1 from the crank axis Cr1. Therefore, the main catalyst 39 is arranged at a position relatively close to the combustion chamber 29. Therefore, it is possible to suppress the temperature from dropping before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, a decrease in the temperature of the exhaust gas flowing into the main catalyst 39 can be suppressed. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

When viewed from the left-right direction, at least a part of the main catalyst 39 is located in front of the straight line L2. The straight line L2 is a straight line that is orthogonal to the cylinder axis Cy1 and orthogonal to the crank axis Cr1. The cylinder axis Cy1 extends in the front-rear direction. Therefore, the straight line L2 extends downward from the crank axis Cr1. Therefore, the main catalyst 39 is disposed at a position close to the combustion chamber 29. Therefore, it is possible to suppress the temperature from dropping before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, a decrease in the temperature of the exhaust gas flowing into the main catalyst 39 can be suppressed. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

The path length (a1 + b1) from one combustion chamber 29 to the upstream end of the main catalyst 39 is shorter than the path length (d1 + e1) from the downstream end of the main catalyst 39 to the discharge port 35e. Therefore, the main catalyst 39 is disposed at a position close to the combustion chamber 29. Therefore, it is possible to suppress the temperature from dropping before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, a decrease in the temperature of the exhaust gas flowing into the main catalyst 39 can be suppressed. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

The path length (a1 + b1) from one combustion chamber 29 to the upstream end of the main catalyst 39 is shorter than the path length (d1) from the downstream end of the main catalyst 39 to the downstream end of the exhaust pipe 34. Therefore, the main catalyst 39 is disposed at a position closer to the combustion chamber 29. Therefore, it is possible to further suppress “a decrease in temperature before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, a decrease in the temperature of the exhaust gas flowing into the main catalyst 39 can be further suppressed. The exhaust gas purification performance of the main catalyst 39 can be further improved.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. Moreover, the example of a change mentioned later can be implemented in combination as appropriate.

The shape of the vehicle body cover 11 is not limited to the shape of the above embodiment. Moreover, the shape of the engine cover part 16 is not limited to the shape of the said embodiment. For example, the engine cover unit 16 may not cover the right side and the left side of the engine body 20. The engine cover portion 16 may cover the entire right surface and the entire left surface of the engine body 20.

The arrangement position of the injector 48 is not limited to the position of the above embodiment. However, the injector 48 is disposed in front of the rear end of the intake passage portion 33. Furthermore, when the single-cylinder four-stroke engine unit 19 and the vehicle body cover 11 are viewed from the front, at least a part of the injector 48 is disposed at a position that can be seen in the opening 17 of the vehicle body cover 11.

In the above embodiment, the injector 48 is provided in the intake passage portion 33. However, the injector 48 may be provided in the cylinder intake passage portion 30 of the cylinder portion 22. Further, the injector 48 may be arranged to inject fuel into the combustion chamber 29.

In the above embodiment, the injector 48 is disposed in front of the main catalyst 39. However, a part of the injector 48 may be disposed in front of the main catalyst 39. Further, the injector 48 may not be disposed in front of the main catalyst 39. FIG. 9 is an example in which a part of the injector 48 is disposed in front of the main catalyst 39. A straight line L14 shown in FIG. 9 is a straight line that passes through the foremost end of the main catalyst 39 and extends in parallel with the vertical direction. A portion of the injector 48 is disposed in front of the straight line L14. Further, the inclination angle θ2 of the cylinder axis Cy2 shown in FIG. 9 is larger than the inclination angle θ1 of the cylinder axis Cy1 of the above embodiment.

The shapes of the exhaust pipe 34 and the intake passage portion 33 in the above embodiment are not limited to the shapes in the above embodiment. Moreover, the internal structure of the silencer 35 is not limited to the structure shown in the schematic diagram of FIG.

In the above embodiment, the intake passage portion 33 is disposed between the engine cover portion 16 and the upper surface of the engine body 20. However, at least a part of the intake passage portion 33 may be disposed between the engine cover portion 16 and the upper surface of the engine body 20.

In the above embodiment, a part of the exhaust pipe 34 is located below the crank axis Cr1. However, a part of the exhaust pipe (single combustion chamber exhaust passage pipe) may be located above the crank axis Cr1.

In the above embodiment, the exhaust pipe 34 is disposed behind the opening 17 of the vehicle body cover 11. However, at least a part of the exhaust pipe 34 may be disposed behind the opening 17 of the vehicle body cover 11.

In the above embodiment, the exhaust pipe 34 is partially disposed below the lower surface of the engine body 20. However, at least a part of the exhaust pipe 34 may be disposed below the lower surface of the engine body 20.

In the above embodiment, the main catalyst 39 and the silencer 35 are arranged on the right side of the center of the motorcycle 1 in the left-right direction. However, the main catalyst and the silencer may be arranged on the left side of the motorcycle in the left-right direction center.

The arrangement position of the main catalyst 39 is not limited to the position of the above embodiment. However, the main catalyst 39 is disposed in the exhaust pipe 34. Further, at least a part of the main catalyst 39 is disposed below the engine body 20. Hereinafter, a specific example of changing the arrangement position of the main catalyst will be described.

In the above embodiment, a part of the main catalyst 39 is disposed below the lower surface of the engine body 20. However, at least a part of the main catalyst 39 may be disposed below the lower surface of the engine body 20.

In the above embodiment, the main catalyst 39 is entirely disposed in front of the crank axis Cr1. However, at least a part of the main catalyst may be disposed in front of the crank axis Cr1. Further, at least a part of the main catalyst may be arranged behind the crank axis Cr1.

The main catalyst 39 of the above embodiment is disposed in front of the straight line L2 as viewed from the left-right direction. However, at least a part of the main catalyst may be disposed in front of the straight line L2 when viewed from the left-right direction. Further, when viewed from the left-right direction, at least a part of the main catalyst may be disposed behind the straight line L2.

The main catalyst 39 of the above embodiment is disposed at a position where the path length a1 + b1 is shorter than the path length d1 + e1. However, the main catalyst 39 may be disposed at a position where the path length a1 + b1 is longer than the path length d1 + e1. The path length a1 + b1 is a path length from the combustion chamber 29 to the upstream end of the main catalyst 39. The path length d1 + e1 is a path length from the downstream end of the main catalyst 39 to the discharge port 35e.

The main catalyst 39 of the above embodiment is disposed at a position where the path length a1 + b1 is shorter than the path length d1. However, the main catalyst 39 may be disposed at a position where the path length a1 + b1 is longer than the path length d1. The path length a1 + b1 is a path length from the combustion chamber 29 to the upstream end of the main catalyst 39. The path length d 1 is a path length from the downstream end of the main catalyst 39 to the downstream end of the exhaust pipe 34.

The main catalyst 39 of the above embodiment is disposed at a position where the path length b1 is shorter than the path length d1. However, the main catalyst 39 may be disposed at a position where the path length b1 is longer than the path length d1. The path length b1 is a path length from the upstream end of the exhaust pipe 34 to the upstream end of the main catalyst 39. The path length d 1 is a path length from the downstream end of the main catalyst 39 to the downstream end of the exhaust pipe 34.

The number of catalysts provided in the single cylinder four-stroke engine unit of the above embodiment is one. However, the number of catalysts provided in the single-cylinder four-stroke engine unit of the present invention may be plural. When there are a plurality of catalysts, the catalyst that most purifies the exhaust gas discharged from the combustion chamber in the exhaust path corresponds to the main catalyst for a single combustion chamber of the present invention. When there is one catalyst, this one catalyst is the main catalyst for a single combustion chamber of the present invention.

At least one upstream sub catalyst (upstream sub catalyst for a single combustion chamber) may be provided upstream of the main catalyst. For example, as shown in FIG. 10A, FIG. 10B, and FIG. 10C, the upstream sub-catalyst 200 may be provided in the exhaust pipe. Further, the upstream sub catalyst may be provided in the cylinder exhaust passage portion 31.

The upstream sub-catalyst 200 may be composed only of the catalyst substance attached to the inner wall of the exhaust pipe 34. In this case, the base material to which the catalytic material of the upstream sub-catalyst 200 is attached is the inner wall of the exhaust pipe 34. Further, the upstream sub-catalyst 200 may have a base material disposed inside the exhaust pipe 34. In this case, the upstream sub-catalyst 200 includes a base material and a catalyst material. The base material of the upstream sub-catalyst 200 has a plate shape, for example. The shape of the cross section orthogonal to the path direction of the plate-like substrate may be S-shaped, circular, or C-shaped. Further, the upstream sub-catalyst 200 may have a porous structure.

The main catalyst 39 purifies the exhaust gas discharged from the combustion chamber 29 in the exhaust passage 41 more than the upstream sub catalyst 200. In other words, the upstream sub-catalyst 200 has a lower contribution to purify the exhaust gas than the main catalyst 39. The respective contributions of purification of the main catalyst 39 and the upstream sub-catalyst 200 can be measured by the following method. In the description of the measurement method, among the main catalyst 39 and the upstream sub-catalyst 200, a catalyst disposed upstream is referred to as a front catalyst, and a catalyst disposed downstream is referred to as a rear catalyst. That is, the upstream sub catalyst 200 is a front catalyst, and the main catalyst 39 is a rear catalyst. In the following description, an engine unit having a front catalyst and a rear catalyst is referred to as a modified engine unit.

The engine unit of the modified example is operated, and the concentration of harmful substances contained in the exhaust gas discharged from the discharge port 35e in the warm-up state is measured. The exhaust gas measurement method shall be in accordance with European regulations. In the warm-up state, the main catalyst 39 and the upstream sub-catalyst 200 are activated at a high temperature. Therefore, the main catalyst 39 and the upstream sub-catalyst 200 can sufficiently exhibit purification performance when in the warm-up state.

Next, remove the rear catalyst of the engine unit used in the test, and place only the base material of the rear catalyst instead. The engine unit in this state is referred to as a measurement engine unit A. And similarly, the density | concentration of the harmful | toxic substance contained in the waste gas discharged | emitted from the discharge port 35e at the time of a warm-up state is measured.

Also, the front catalyst of this measurement engine unit A is removed, and only the base material of the front catalyst is arranged instead. The engine unit in this state is referred to as a measurement engine unit B. And similarly, the density | concentration of the harmful | toxic substance contained in the waste gas discharged | emitted from the discharge port 35e at the time of a warm-up state is measured. When the upstream sub-catalyst 200 (front catalyst) has a configuration in which a catalytic material is directly attached to the inner wall of the exhaust pipe 34, the exhaust pipe 34 corresponds to the base material. The arrangement of only the base material of the upstream sub-catalyst 200 in place of the upstream sub-catalyst 200 is to prevent the catalyst material from adhering to the inner wall of the exhaust pipe 34.

The measurement engine unit A has a front catalyst and does not have a rear catalyst. The measurement engine unit B does not have a front catalyst and a rear catalyst. Therefore, the degree of contribution of the purification of the front catalyst (upstream sub-catalyst 200) is calculated from the difference between the measurement result of the measurement engine unit A and the measurement result of the measurement engine unit B. Further, the contribution of the purification of the rear catalyst (main catalyst 39) is calculated from the difference between the measurement result of the measurement engine unit A and the measurement result of the engine unit of the modified example.

The purification capacity of the upstream sub-catalyst 200 may be smaller or larger than the purification capacity of the main catalyst 39. The purification capacity of the upstream sub catalyst 200 is smaller than the purification capacity of the main catalyst 39. The exhaust gas purification rate when only the upstream sub catalyst 200 is provided is the purification of exhaust gas when only the main catalyst 39 is provided. That is less than the rate.

By providing the upstream sub catalyst upstream of the main catalyst 39, the following effects can be obtained. The exhaust gas is purified by the upstream sub catalyst in addition to the main catalyst 39. Therefore, the exhaust gas purification performance by the catalyst can be further improved. In addition, the main catalyst 39 and the upstream sub-catalyst can be reduced in size as compared with the case where only the main catalyst 39 is provided while maintaining the exhaust gas purification performance by the catalyst. Thereby, the upstream sub-catalyst can be raised to the activation temperature at an early stage when the engine is started. Therefore, the exhaust gas purification performance by the catalyst can be improved while suppressing an increase in the size of the vehicle in the vertical direction.

At least one downstream sub-catalyst (downstream sub-catalyst for a single combustion chamber) may be provided downstream of the main catalyst. The downstream subcatalyst may or may not have a porous structure. A specific example in the case of not having a porous structure is the same as that of the upstream sub-catalyst 200. For example, as shown in FIGS. 10 (d) and 10 (e), the downstream sub-catalyst 400 may be provided in the exhaust pipe 34. Further, the downstream sub-catalyst may be provided in the silencer 35. The downstream sub-catalyst may be provided downstream from the downstream end of the exhaust pipe 34. Further, when the downstream sub catalyst is provided, the upstream sub catalyst 200 may be provided upstream of the main catalyst.

By providing the downstream sub catalyst downstream of the main catalyst 39, the following effects can be obtained. The exhaust gas is purified by the downstream sub catalyst in addition to the main catalyst 39. Therefore, the exhaust gas purification performance by the catalyst can be further improved. Further, the main catalyst 39 and the downstream sub-catalyst can be reduced in size as compared with the case where only the main catalyst 39 is provided while maintaining the exhaust gas purification performance by the catalyst. Thereby, the main catalyst 39 can be raised to the activation temperature at an early stage when the engine is started. Therefore, the exhaust gas purification performance by the catalyst can be improved while suppressing an increase in the size of the vehicle in the vertical direction.
Further, the heat released from the main catalyst 39 can be reduced by downsizing the main catalyst 39. The downstream sub-catalyst can be disposed at a position away from the injector 48 in the front-rear direction. Therefore, the influence of heat on the injector 48 can be further suppressed.

When the downstream sub-catalyst is provided downstream of the main catalyst, the main catalyst most purifies the exhaust gas discharged from the combustion chamber in the exhaust path. The degree of contribution of purification of each of the main catalyst and the downstream sub-catalyst can be measured by the measurement method described in the modification in which the upstream sub-catalyst is provided. In the above measurement method, the “front catalyst” is the main catalyst, and the “rear catalyst” is the “downstream sub-catalyst”.

When the downstream sub-catalyst is provided downstream of the main catalyst, the purification capacity of the downstream sub-catalyst may be smaller or larger than the purification capacity of the main catalyst. That is, the exhaust gas purification rate when only the downstream sub-catalyst is provided may be smaller or larger than the exhaust gas purification rate when only the main catalyst is provided.

When the downstream sub-catalyst is provided downstream of the main catalyst, the main catalyst deteriorates faster than the downstream sub-catalyst. Therefore, when the cumulative travel distance becomes long, the magnitude relationship between the contributions of purification of the main catalyst and the downstream sub-catalyst may be reversed. The main catalyst for a single combustion chamber of the present invention purifies the exhaust gas discharged from the combustion chamber most in the exhaust path. This is a state before the reverse phenomenon as described above occurs. That is, the cumulative travel distance has not reached a predetermined distance (for example, 1000 km).

In the above embodiment, the main catalyst 39 is a three-way catalyst. However, the main catalyst for a single combustion chamber of the present invention may not be a three-way catalyst. The main catalyst for the single combustion chamber may be a catalyst that removes any one or two of hydrocarbon, carbon monoxide, and nitrogen oxide. Further, the main catalyst for the single combustion chamber may not be a redox catalyst. The main catalyst may be an oxidation catalyst or a reduction catalyst that removes harmful substances only by either oxidation or reduction. An example of a reduction catalyst is a catalyst that removes nitrogen oxides by a reduction reaction. This modification may be applied to the upstream sub-catalyst and the downstream sub-catalyst.

In the above embodiment, the length c1 of the main catalyst 39 in the path direction is larger than the maximum width w1. However, in the main catalyst for a single combustion chamber of the present invention, the length in the path direction may be shorter than the maximum width in the direction perpendicular to the path direction. However, the main catalyst for a single combustion chamber of the present invention is configured to purify the exhaust gas most in the exhaust path. The exhaust path here is a path from the combustion chamber to the discharge port facing the atmosphere.

The main catalyst for a single combustion chamber of the present invention may have a configuration in which a plurality of pieces of catalyst are arranged close to each other. Each piece has a substrate and a catalytic material. Here, proximity means a state in which the distance between pieces is shorter than the length of each piece in the path direction. The composition of the multi-piece substrate may be one type or plural types. The precious metal of the catalyst material of the multi-piece catalyst may be one kind or plural kinds. The composition of the support of the catalyst substance may be one type or a plurality of types. This modification may be applied to the upstream sub-catalyst and the downstream sub-catalyst.

The arrangement position of the upstream oxygen detection member 37 is not limited to the position of the above embodiment. However, the upstream oxygen detection member 37 is disposed upstream of the main catalyst 39. The upstream oxygen detection member may be disposed in the cylinder exhaust passage portion 31 of the cylinder portion 22. The number of upstream oxygen detection members provided upstream of the main catalyst 39 may be two or more.

When the upstream sub-catalyst 200 is provided upstream of the main catalyst 39, for example, as shown in FIG. 10B, the upstream oxygen detection member 37 is preferably provided upstream of the upstream sub-catalyst 200. For example, as shown in FIG. 10A, the upstream oxygen detection member 37 may be provided downstream from the upstream sub-catalyst 200. For example, as shown in FIG. 10C, two upstream oxygen detection members 37 A and 37 B may be provided upstream and downstream of the upstream sub-catalyst 200.

At least one downstream oxygen detection member may be provided downstream of the main catalyst. The specific configuration of the downstream oxygen detection member is the same as that of the upstream oxygen detection member 37 of the above embodiment. For example, as shown in FIG. 10A, FIG. 10B, FIG. 10D, and FIG. 10E, the downstream oxygen detection member 437 may be provided in the exhaust pipe. Further, the downstream oxygen detection member may be provided in the silencer 35. The downstream oxygen detection member may be provided so as to detect exhaust gas downstream from the downstream end of the exhaust pipe 34. Further, when the main catalyst is provided in the cylinder exhaust passage portion, the downstream oxygen detection member may be provided in the cylinder exhaust passage portion.

When the downstream sub-catalyst 400 is provided downstream of the main catalyst 39, the downstream oxygen detection member 437 may be disposed at any of the following two positions. For example, as shown in FIG. 10D, the downstream oxygen detection member 437 may be provided downstream of the main catalyst 39 and upstream of the downstream sub-catalyst 400. For example, as shown in FIG. 10E, the downstream oxygen detection member 437 may be provided downstream of the downstream sub-catalyst 400. Further, downstream oxygen detection members may be provided upstream and downstream of the downstream sub-catalyst 400, respectively.

When the downstream oxygen detection member is provided downstream from the main catalyst, the electronic control unit processes the signal of the downstream oxygen detection member. The electronic control unit may determine the purification capacity of the main catalyst based on the signal from the downstream oxygen detection member. The electronic control unit may determine the purification capacity of the main catalyst based on signals from the upstream oxygen detection member and the downstream oxygen detection member. The electronic control unit may perform combustion control based on signals from the upstream oxygen detection member and the downstream oxygen detection member.

An example of a specific method for determining the purification capacity of the main catalyst based on the signal from the downstream oxygen detection member will be described. First, the fuel injection amount is controlled so that the mixed gas repeats rich and lean for a certain period (several seconds). And the delay of the change of the signal of the downstream oxygen detection member with respect to the change of the fuel injection amount is detected. When the delay of the signal change of the downstream oxygen detection member is large, it is determined that the purification capacity of the main catalyst has decreased from a predetermined level. In this case, a signal is sent from the electronic control unit to the display device. Then, a warning light (not shown) of the display device is turned on. Thereby, it is possible to prompt the passenger to replace the main catalyst.

Thus, the deterioration of the main catalyst can be detected by using the signal of the downstream oxygen detection member disposed downstream of the main catalyst. For this reason, it is possible to notify before the deterioration of the main catalyst reaches a predetermined level, and to promote the replacement of the main catalyst. Thereby, the initial performance regarding exhaust gas purification of the saddle riding type vehicle can be maintained for a longer period.

An example of a specific method for determining the purification capacity of the main catalyst based on signals from the upstream oxygen detection member and the downstream oxygen detection member will be described. For example, the purification capability of the main catalyst may be determined by comparing the change in the signal of the upstream oxygen detection member and the change in the signal of the downstream oxygen detection member. By using the signals of the two oxygen detection members arranged upstream and downstream of the main catalyst, the degree of deterioration of the main catalyst can be detected with higher accuracy. Therefore, the replacement of the main catalyst for the single combustion chamber can be promoted at a more appropriate timing as compared with the case where the deterioration of the main catalyst is determined using only the signal of the downstream oxygen detection member. Therefore, it is possible to use one main catalyst for a longer period while maintaining the initial performance related to the exhaust gas purification performance of the vehicle.

An example of a specific method for performing combustion control based on signals from the upstream oxygen detection member and the downstream oxygen detection member will be described. First, as in the above embodiment, the basic fuel injection amount is corrected based on the signal from the upstream oxygen detection member 37 and fuel is injected from the injector 48. The exhaust gas generated by the combustion of the fuel is detected by the downstream oxygen detection member. Then, the fuel injection amount is corrected based on the signal from the downstream oxygen detection member. Thereby, the deviation of the air-fuel ratio of the mixed gas with respect to the target air-fuel ratio can be further reduced.

The actual purification status by the main catalyst can be grasped by using the signals of the two oxygen detection members arranged upstream and downstream of the main catalyst. Therefore, when the fuel control is performed based on the signals of the two oxygen detection members, the accuracy of the fuel control can be improved. Further, the upstream oxygen detection member can stably detect the oxygen concentration in the exhaust gas. Therefore, the accuracy of fuel control can be further improved. Thereby, since the progress of the deterioration of the main catalyst can be delayed, the initial performance regarding the exhaust purification of the saddle riding type vehicle can be maintained for a longer period.

In the above embodiment, the ignition timing and the fuel injection amount are controlled based on the signal from the upstream oxygen detection member 37. However, the control process based on the signal from the upstream oxygen detection member 37 is not particularly limited, and may be only one of the ignition timing and the fuel injection amount. Further, the control process based on the signal from the upstream oxygen detection member 37 may include a control process other than the above.

The upstream oxygen detection member may incorporate a heater. The detection part of the upstream oxygen detection member can detect the oxygen concentration when it is heated to a high temperature and activated. Therefore, if the upstream oxygen detection member has a built-in heater, the start of oxygen detection can be accelerated by heating the detection unit with the heater simultaneously with the start of operation. When the downstream oxygen detection member is provided downstream from the main catalyst, this modification may be applied to the downstream oxygen detection member.

At least a part of the exhaust pipe upstream from the main catalyst may be composed of multiple pipes. The multiple tube has an inner tube and at least one outer tube covering the inner tube. FIG. 11 shows an example in which at least a part of the exhaust pipe 534 upstream of the main catalyst is configured with a double pipe 500. For example, as shown in FIG. 11, at least a part of the exhaust pipe 534 upstream of the main catalyst may be constituted by a double pipe. The double tube 500 includes an inner tube 501 and an outer tube 502 that covers the inner tube 501. In FIG. 11, the inner tube 501 and the outer tube 502 are in contact with each other only at both ends. The inner tube and the outer tube of the multiple tube may be in contact with each other at both ends. For example, the inner tube and the outer tube may be in contact with each other at the bent portion. The contact area is preferably smaller than the non-contact area. Further, the inner tube and the outer tube may be in contact with each other. When the exhaust pipe has a multiple pipe, the upstream oxygen detection member is preferably arranged in the middle of the multiple pipe or downstream of the multiple pipe. Multiple tubes have a high thermal insulation effect. Therefore, it is possible to suppress the temperature from dropping before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, a decrease in the temperature of the exhaust gas flowing into the main catalyst 39 can be suppressed. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

For example, as shown in FIG. 12, at least a part of the outer surface of the catalyst arrangement passage portion 40b may be covered with a catalyst protector 600. The catalyst protector 600 is formed in a substantially cylindrical shape. By providing the catalyst protector 600, the catalyst arrangement passage portion 40b and the main catalyst 39 can be protected. Furthermore, by providing the catalyst protector 600, a decrease in the temperature of the main catalyst 39 can be suppressed. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

In the above embodiment, the gas flowing through the exhaust passage 41 when the engine is driven is only the exhaust gas discharged from the combustion chamber 29. However, the single-cylinder four-stroke engine unit of the present invention may include a secondary air supply mechanism that supplies air to the exhaust path. A known configuration is adopted as a specific configuration of the secondary air supply mechanism. The secondary air supply mechanism may be configured to forcibly supply air to the exhaust path using an air pump. Further, the secondary air supply mechanism may be configured to draw air into the exhaust path by the negative pressure of the exhaust path. In this case, the secondary air supply mechanism includes a reed valve that opens and closes in response to pressure pulsation caused by exhaust gas. When the secondary air supply mechanism is provided, the upstream oxygen detection member may be disposed upstream or downstream of the position where air flows.

In the above embodiment, only one exhaust port 31 a is provided for one combustion chamber 29. However, a plurality of exhaust ports may be provided for one combustion chamber. For example, the case where a variable valve mechanism is provided corresponds to this modification. However, the exhaust paths extending from the plurality of exhaust ports gather upstream from the main catalyst. The exhaust paths extending from the plurality of exhaust ports are preferably gathered at the cylinder portion.

The combustion chamber of the present invention may have a configuration having a main combustion chamber and a sub-combustion chamber connected to the main combustion chamber. In this case, one combustion chamber is formed by the main combustion chamber and the sub-combustion chamber.

In the above embodiment, the crankcase body 23 and the cylinder body 24 are separate bodies. However, the crankcase body and the cylinder body may be integrally formed. In the above embodiment, the cylinder body 24, the cylinder head 25, and the head cover 26 are separate bodies. However, any two or three of the cylinder body, the cylinder head, and the head cover may be integrally formed.

In the above embodiment, a motorcycle is exemplified as the saddle riding type vehicle including the single cylinder four-stroke engine unit. However, the straddle-type vehicle of the present invention may be any straddle-type vehicle as long as it is a straddle-type vehicle that moves with the power of the single-cylinder four-stroke engine unit. The saddle riding type vehicle of the present invention may be a scooter type motorcycle. The straddle-type vehicle of the present invention may be a straddle-type vehicle other than a motorcycle. Saddle-type vehicles refer to all vehicles that ride in a state in which an occupant straddles a saddle. The saddle riding type vehicle includes a motorcycle, a tricycle, a four-wheel buggy (ATV: All Terrain Vehicle), a water bike, a snowmobile, and the like.

In the present specification and the present invention, the upstream end of the main catalyst means the end of the main catalyst that has the shortest path length from the combustion chamber. The downstream end of the main catalyst means the end where the path length from the combustion chamber is the longest in the main catalyst. Similar definitions apply to upstream and downstream ends of elements other than the main catalyst.

In the present specification and the present invention, the passage means a wall body or the like that surrounds the route to form the route, and the route means a space through which the object passes. The exhaust passage portion means a wall body that surrounds the exhaust path and forms the exhaust path. The exhaust path means a space through which exhaust passes.

In the present specification and the present invention, the length of the exhaust path refers to the length of the line in the middle of the exhaust path. Further, the path length of the expansion chamber of the silencer means the length of the path connecting the middle of the inlet of the expansion chamber to the middle of the outlet of the expansion chamber in the shortest distance.

In this specification, the route direction means the direction of the route passing through the middle of the exhaust route and the direction in which the exhaust gas flows.

In this specification, the expression of the area of a cross section perpendicular to the path direction of the passage portion is used. Moreover, in this specification and this invention, the expression of the area of the cross section orthogonal to the direction through which the waste gas flows of a channel | path part is used. The area of the cross section of the passage portion here may be the area of the inner peripheral surface of the passage portion or the area of the outer peripheral surface of the passage portion.

Further, in the present specification and the present invention, the term “a member or a straight line extends in the A direction” does not indicate only a case where the member or the straight line is arranged in parallel with the A direction. The member or straight line extending in the A direction includes the case where the member or straight line is inclined within a range of ± 45 ° with respect to the A direction. The A direction does not indicate a specific direction. The A direction can be replaced with a horizontal direction or a front-rear direction.

The crankcase body 23 in the present specification corresponds to the crankcase portion 18 in the specification of the basic application of the present application. The cylinder body 24 in the present specification corresponds to the cylinder portion 24 in the specification of the basic application described above. The engine body 20 in the present specification corresponds to the engine 20 in the specification of the basic application described above. The cylinder exhaust passage portion 31 of the present specification corresponds to a passage portion that forms the exhaust gas passage P2 in the specification of the basic application described above.

The present invention is any implementation including equivalent elements, modifications, deletions, combinations (eg, combinations of features across various embodiments), improvements, and / or changes that may be recognized by one of ordinary skill in the art based on the disclosure herein. It includes forms. Claim limitations should be construed broadly based on the terms used in the claims. Claim limitations should not be limited to the embodiments described herein or in the process of this application. Such an embodiment should be construed as non-exclusive. For example, in the present specification, the terms “preferably” and “good” are non-exclusive, and “preferably but not limited to” or “good but not limited thereto”. It means "not."

1 Motorcycle (saddle-ride type vehicle)
DESCRIPTION OF SYMBOLS 2 Body frame 3 Head pipe 4 Main frame 11 Body cover 16 Engine cover part 17 Opening part 19 Single cylinder 4 stroke engine unit 20 Engine main body 21 Crankcase part 22 Cylinder part 24a Cylinder hole 27 Crankshaft 28 Piston 29 Combustion chamber 30 Cylinder intake Passage (Cylinder intake passage for single combustion chamber)
31 Cylinder exhaust passage (cylinder exhaust passage for single combustion chamber)
34 Exhaust pipe (Cylinder exhaust pipe for single combustion chamber)
35 Silencer (Cylinder silencer for single combustion chamber)
35e Discharge port 38 Catalyst unit 39 Main catalyst (Main catalyst for single combustion chamber)
40a Upstream passage part 40b Catalyst arrangement passage part 40c Downstream passage part 41 Exhaust path 48 Injector (fuel injection device)
200 Upstream sub-catalyst (upstream sub-catalyst for single combustion chamber)
400 Downstream sub-catalyst (downstream sub-catalyst for single combustion chamber)
500 Double pipe 501 Inner pipe 502 Outer pipe 600 Catalyst protector Cr1 Crank axis (centerline of crankshaft)
Cy1 Cylinder axis (Cylinder hole center line)
L2 Straight line perpendicular to the crank axis and cylinder axis

Claims

A straddle-type vehicle equipped with a single-cylinder four-stroke engine unit,
The single-cylinder four-stroke engine unit is
One combustion chamber, a part of which is defined by the inner surface of the cylinder hole, a single combustion chamber cylinder intake passage through which air supplied to the one combustion chamber flows, and exhaust gas discharged from the one combustion chamber An engine main body having a horizontal cylinder portion formed so that a flowing cylinder exhaust passage portion for a single combustion chamber is formed, and a center line of the cylinder hole extends in a front-rear direction of the saddle riding type vehicle;
A single combustion chamber intake passage portion that is disposed at least partially above the engine body and connected to an upstream end of the single combustion chamber cylinder intake passage portion of the engine body;
An exhaust pipe for a single combustion chamber disposed at least partially below the engine body and connected to a downstream end of the cylinder exhaust passage for the single combustion chamber of the engine body;
A discharge port facing the atmosphere is connected to the exhaust pipe for the single combustion chamber, and the exhaust gas flowing in from the downstream end of the exhaust pipe for the single combustion chamber flows to the discharge port to reduce the sound generated by the exhaust gas. A single combustion chamber silencer,
Arranged in the exhaust pipe for the single combustion chamber, at least a part is disposed below the engine body, and is discharged from the one combustion chamber in an exhaust path from the one combustion chamber to the discharge port. The main catalyst for the single combustion chamber that most purifies the exhaust gas,
It is provided in the single combustion chamber intake passage portion or the single combustion chamber cylinder intake passage portion, and is disposed in front of the rear end of the single combustion chamber intake passage portion in the front-rear direction. A fuel injection device for injecting fuel into the air sucked from the upstream end of the intake passage portion for the single combustion chamber;
Have
An engine cover portion that covers at least a part of the upper surface of the engine body and is formed so that both left and right end portions of the saddle-ride type vehicle are positioned below the center in the left and right direction; A vehicle body cover with an opening formed in the
The single combustion chamber intake passage portion is at least partially disposed between the engine cover portion and the upper surface of the engine body, and the rearmost end thereof is the opening of the vehicle body cover in the front-rear direction. It is arranged at the rear,
The single combustion chamber exhaust pipe is at least partially disposed behind the opening of the vehicle body cover in the front-rear direction,
The fuel injection device is disposed at a position where at least a part of the fuel injection device can be seen in the opening of the vehicle body cover when the single cylinder four-stroke engine unit and the vehicle body cover are viewed from the front. A straddle-type vehicle.
The straddle-type vehicle according to claim 1, wherein a part of the fuel injection device is disposed in front of the intake passage portion for the single combustion chamber.
The vehicle body cover has a maximum vertical distance between the front end of the engine cover portion and the upper surface of the engine body in the vertical direction between the center or rear end of the engine cover portion and the upper surface of the engine body. The straddle-type vehicle according to claim 1 or 2, wherein the straddle-type vehicle is formed to be larger than a separation distance.
The straddle-type vehicle according to any one of claims 1 to 3, wherein the engine cover portion covers at least a part of a left surface or a right surface of the engine body.
A vehicle body frame having a head pipe and a main frame extending rearward and downward from the head pipe;
The vehicle body cover covers at least a part of the main frame from above,
The straddle-type vehicle according to any one of claims 1 to 4, wherein the engine body is disposed below the main frame and is supported by the main frame so as not to swing.
The single combustion chamber exhaust pipe has a catalyst arrangement passage portion in which the single catalyst for the single combustion chamber is arranged, and an upstream passage portion connected to an upstream end of the catalyst arrangement passage portion. ,
The area of the cross section perpendicular to the flow direction of the exhaust gas in the catalyst arrangement passage portion is larger than the area of the cross section perpendicular to the flow direction of the exhaust gas in at least a part of the upstream passage portion. The straddle-type vehicle according to any one of 5.
The engine body has a crankcase portion including a crankshaft extending in the left-right direction of the saddle riding type vehicle,
The at least part of the single combustion chamber main catalyst is located in front of the saddle type vehicle in the front-rear direction with respect to the center line of the crankshaft. The saddle riding type vehicle described in 1.
The engine body has a crankcase portion including a crankshaft extending in the left-right direction of the saddle riding type vehicle,
When the straddle-type vehicle is viewed from the left-right direction, at least a part of the single combustion chamber main catalyst is a straight line perpendicular to the center line of the cylinder hole and perpendicular to the center line of the crankshaft. The straddle-type vehicle according to any one of claims 1 to 7, wherein the straddle-type vehicle is located in front of the direction.
The single combustion chamber main catalyst has a path length from the one combustion chamber to the upstream end of the single combustion chamber main catalyst from the downstream end of the single combustion chamber main catalyst to the discharge port. The straddle-type vehicle according to any one of claims 1 to 8, wherein the straddle-type vehicle is disposed at a position shorter than a route length.
The single combustion chamber main catalyst has a path length from the one combustion chamber to the upstream end of the single combustion chamber main catalyst, so that the single combustion chamber main catalyst for the single combustion chamber extends from the downstream end of the single combustion chamber main catalyst. The straddle-type vehicle according to any one of claims 1 to 9, wherein the straddle-type vehicle is disposed at a position shorter than a path length to a downstream end of the exhaust pipe for use.
The single combustion chamber exhaust pipe is a multiple pipe in which at least part of the exhaust gas flow direction upstream of the single combustion chamber main catalyst includes an inner pipe and at least one outer pipe covering the inner pipe. The straddle-type vehicle according to any one of claims 1 to 10, wherein the straddle-type vehicle is configured as follows.
The single combustion chamber exhaust pipe has a catalyst arrangement passage portion in which the single combustion chamber main catalyst is arranged,
The single-cylinder four-stroke engine unit is
The straddle-type vehicle according to any one of claims 1 to 11, further comprising a catalyst protector that covers at least a part of an outer surface of the catalyst arrangement passage portion.
The single-cylinder four-stroke engine unit is provided upstream of the single combustion chamber main catalyst in the flow direction of exhaust gas in the single combustion chamber cylinder passage or in the single combustion chamber exhaust pipe. The straddle-type vehicle according to any one of claims 1 to 12, further comprising an upstream sub-catalyst for a single combustion chamber to be purified.
The single-cylinder four-stroke engine unit is configured to emit more exhaust gas than the single combustion chamber main catalyst in the single combustion chamber cylinder passage, the single combustion chamber exhaust pipe, or the single combustion chamber silencer. The straddle-type vehicle according to any one of claims 1 to 13, further comprising a downstream sub-catalyst for a single combustion chamber that is provided downstream in a flow direction and purifies exhaust gas.