TW201606183A - Saddle-driven vehicle - Google Patents

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). At least part of a fuel injection device (48) is positioned to the front of a main catalyst (39).

Description

Straddle type vehicle

The present invention relates to a straddle type vehicle.

Previously, there was a straddle-type vehicle equipped with a single-cylinder four-stroke engine unit. Further, a structure in which the catalyst is disposed upstream of the muffler of the exhaust passage has been proposed (for example, Patent Document 1). According to the proposal of Patent Document 1, it is possible to cause a high-temperature exhaust gas to flow into the catalyst. When the catalyst becomes high temperature, the activity is improved. Therefore, the purification performance of the exhaust gas using the catalyst can be improved.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-207571

However, the temperature of the catalyst is also very high compared to the engine body. Therefore, if the catalyst is disposed upstream of the muffler, countermeasures against thermal damage of the catalyst are required. On the other hand, the straddle type vehicle of Patent Document 1 must ensure the distance between the ground and the upper and lower directions of the single-cylinder four-stroke engine unit. Therefore, for example, if a heat insulating member is provided between the engine body and the catalyst, the engine body must be disposed above. Therefore, there is a problem that the straddle type vehicle is enlarged in the vertical direction.

An object of the present invention is to provide a catalyst capable of reducing the size of the vehicle in the vertical direction while improving the purification performance of the exhaust gas using the catalyst. A straddle-type vehicle affected by heat.

The proposal of the above Patent Document 1 has been studied in detail. The straddle-type vehicle of Patent Document 1 includes an engine body having a crankcase portion and a horizontal cylinder portion extending from the crankcase portion in the front-rear direction. The straddle type vehicle of Patent Document 1 is provided with a catalyst below the engine body of the single-cylinder four-stroke engine unit. Therefore, the hot gas from the catalyst rises along the periphery of the engine body. Further, the straddle-type vehicle of Patent Document 1 includes a vehicle body casing above the engine body so as to cover at least a part of the upper surface of the engine body. Therefore, the heat rising from the engine body and the catalyst tends to accumulate in the space covered by the vehicle body casing above the engine body. Further, in the vehicle of the straddle type vehicle of Patent Document 1, the intake pipe and the fuel injection device are often disposed above the horizontal cylinder portion. Therefore, for a straddle-type vehicle having a horizontal cylinder portion as in Patent Document 1, parts of the intake system or parts of the fuel supply system are disposed in the space where the heat is accumulated. Moreover, if the parts of the fuel supply system become high temperature, there is a change in the performance of the engine.

In the course of research and development, the inventors of the present invention focused on the shape of the space covered by the vehicle body casing above the engine body. In the space covered by the vehicle body casing above the engine body of the straddle-type vehicle as in Patent Document 1, the distance between the front portion and the engine body is formed larger than the distance between the center portion or the rear portion and the engine body. Further, the space above the engine body covered by the vehicle body casing is open to the front of the vehicle. Therefore, it is conceivable to study the arrangement of the parts of the intake system or the parts of the fuel supply system by utilizing the shape of the space covered by the outer casing of the vehicle body above the engine body of the straddle type vehicle, and it is possible to suppress the heat pair even if the hot gas rises from the catalyst. Impact of intake system components or fuel supply system components. Further, it has been found that by using the shape of the space covered by the vehicle body casing above the engine body of the straddle type vehicle, the arrangement of the components of the intake system or the parts of the fuel supply system can be studied, and the influence of the heat of the catalyst on the surroundings can be simplified. The way to insulate the structure. Further, it has been found that even if the catalyst is increased in size in order to improve the purification performance of the catalyst, it is possible to suppress the catalyst. The effect of the heat of the catalyst.

The straddle type vehicle of the present invention is characterized in that it is equipped with a single-cylinder four-stroke engine unit having an engine body having a horizontal cylinder portion formed with a part of a cylinder a combustion chamber in which the inner surface of the hole is partitioned, a single-combustion-chamber intake passage portion through which air supplied to the one combustion chamber is circulated, and a single-combustion cylinder exhaust passage through which exhaust gas discharged from the one combustion chamber flows a portion of the cylinder bore extending in a front-rear direction of the straddle-type vehicle; at least a portion of the single-combustion intake passage portion is disposed above the engine body and connected to the above An upstream end of the single-combustion-chamber intake passage portion of the engine body; and a single-combustion exhaust pipe disposed at least in part below the engine body and connected to the single combustion chamber of the engine body a downstream end of the cylinder exhaust passage portion; a muffler for a single combustion chamber having a discharge port facing the atmosphere and connected The single-combustion-chamber exhaust pipe is supplied from the exhaust gas flowing from the downstream end of the single-combustion-chamber exhaust pipe to the discharge port to reduce the sound generated by the exhaust gas, and the single-combustion-chamber main catalyst is disposed in The exhaust pipe of the single combustion chamber is disposed at least partially below the engine body, and is exhausted from the combustion chamber to the maximum extent in an exhaust path from the one combustion chamber to the discharge port. And a fuel injection device provided in the single combustion chamber intake passage portion or the single combustion chamber cylinder intake passage portion, and at least partially disposed in the front-rear direction in the single combustion chamber main catalyst a fuel injection from the air sucked from the upstream end of the single intake passage passage portion; and a vehicle body casing including an engine casing portion and an opening portion formed in a front portion thereof The engine casing portion covers at least a portion of the upper surface of the engine body and the two ends of the straddle type vehicle are located at both ends The center of the left and right direction is formed further downward, and the single combustion chamber intake passage portion is disposed at least partially between the engine casing portion and the upper surface of the engine body, and the rear end thereof is disposed at the rear end thereof. Upper The opening portion of the vehicle body casing is further rearward, and the single combustion chamber exhaust pipe is disposed at least partially rearward of the opening portion of the vehicle body casing in the front-rear direction.

According to this configuration, the single-cylinder four-stroke engine unit mounted on the straddle type vehicle of the present invention includes an engine main body, a single combustion chamber intake passage portion, a single combustion chamber exhaust pipe, a single combustion chamber muffler, and a single combustion. The main catalyst for the chamber and the fuel injection device. The engine body has a 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 in the horizontal cylinder portion. A portion of the combustion chamber is zoned by the inner surface of the cylinder bore. The single-combustion chamber cylinder intake passage portion supplies air to be supplied to one combustion chamber. The single-combustion chamber uses a cylinder exhaust passage portion to supply exhaust gas discharged from one 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 silencer for a single combustion chamber has an outlet for the atmosphere. The single combustion chamber is connected to the single combustion chamber exhaust pipe by a muffler, and the exhaust gas flowing from the downstream end of the single combustion chamber exhaust pipe flows to the discharge port. A single combustion chamber muffler reduces the sound generated by the exhaust gas. The single combustion chamber main catalyst is disposed in a single combustion chamber exhaust pipe. The single combustion chamber uses the main catalyst to purify the exhaust gas discharged from a combustion chamber in the exhaust path from a combustion chamber to the discharge port. The fuel injection device injects fuel into the air taken in from the upstream end of the intake passage portion of the single combustion chamber. 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 disposed in such a manner that the center line of the cylinder bore extends in the front and rear directions of the straddle type vehicle. Therefore, at least a part of the intake passage portion for the single combustion chamber 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 portion of the single catalyst main catalyst is disposed below the engine body. Therefore, the hot gas from the single-chamber main catalyst rises above the engine body along the periphery of the engine body.

At least a portion of the upper surface of the engine body is covered by an engine casing portion of the body casing. Further, the engine casing 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 further rearward than the opening portion of the front portion of the vehicle body casing. Therefore, the heat rising from the single-combustion-chamber main catalyst and the engine body tends to accumulate in the space covered by the vehicle body casing above the engine body.

Further, the last end of the single combustion chamber intake passage portion is disposed further rearward than the opening of the vehicle body casing. At least a portion of the intake passage portion for the single combustion chamber is disposed between the engine casing portion and the upper surface of the engine body. That is, at least a part of the single intake air intake passage portion is disposed in a space covered by the vehicle body casing above the engine body. As described above, the heat rising from the single-combustion-chamber main catalyst and the engine body tends to accumulate in the space covered by the vehicle body casing above the engine body.

However, the body casing of the straddle type vehicle of the present invention has an opening formed at a front portion thereof. Therefore, the space above the engine body covered by the vehicle body casing is open to the front of the vehicle. Therefore, the heat of the space covered by the vehicle body casing gathered above the engine body easily escapes toward the front. That is, the temperature at the front of the space is relatively low. At least a part of the fuel injection device of the straddle type vehicle of the present invention is disposed further forward than the single catalyst main catalyst. Thus, the fuel injection device is less susceptible to heat rising from the single catalyst main catalyst. In addition to this, the fuel injection device is disposed at a position close to the opening of the vehicle body casing. Therefore, even if the heat is concentrated on the space covered by the vehicle body casing above the engine body, the influence of heat on the fuel injection device can be further suppressed. Therefore, even if the single-combustion-chamber main catalyst is increased in size 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.

As described above, by investigating the arrangement position of the fuel injection device, it is possible to suppress the influence of the heat of the single combustion chamber main catalyst on the fuel injection device. Therefore, it is possible to simplify the structure in which the heat of the main catalyst for the single combustion chamber is not thermally affected. because In this way, even if the single-combustion-chamber main catalyst is increased in size in order to improve the purification performance of the single-combustion-chamber main catalyst, it is possible to suppress an increase in the size of the vehicle in the vertical direction.

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

In the straddle-type vehicle of the present invention, preferably, the vehicle body casing has a maximum distance between a front end of the engine casing portion and a top surface of the engine body in a vertical direction that is greater than a front-to-back direction of the engine casing portion or The rear end is formed at a maximum distance from the upper surface of the upper surface of the engine body.

According to this configuration, the distance between the front end of the engine casing portion and the upper surface of the upper surface of the engine body is greater than the distance between the center or the rear end of the engine casing portion in the front and rear direction and the upper and lower surfaces of the upper surface of the engine body. Therefore, the front portion of the space covered by the vehicle body casing above the engine body has a longer length in the vertical direction than the center or the rear portion of the space in the front and rear directions. Therefore, the heat of the space covered by the vehicle body casing gathered above the engine body is more likely to escape toward the front. That is, the temperature of the front portion of the space can be further reduced. Therefore, the influence of heat on the fuel injection device can be more suppressed. Therefore, even if the single-combustion-chamber main catalyst is increased in size 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 straddle type vehicle of the present invention, preferably, the engine casing portion covers at least a part of a left side or a right side of the engine body.

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

In the straddle type vehicle of the present invention, preferably, the single combustion chamber exhaust pipe has a catalyst arrangement passage portion in which a single combustion chamber main catalyst is disposed, and an upstream a passage portion connected to an upstream end of the catalyst arrangement passage portion; an area of a cross section of the catalyst arrangement passage portion orthogonal to a flow direction of the exhaust gas is larger than an area of a cross section orthogonal to a flow direction of the exhaust gas of at least a part of the upstream passage portion .

According to this configuration, the exhaust pipe for a single combustion chamber has a catalyst arrangement passage portion in which a single catalyst main catalyst is disposed. Further, the area of the 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 the exhaust gas of at least a part of the upstream passage portion. Therefore, compared with the case where the area Sa is smaller than the area of the cross section of the upstream passage portion orthogonal to the flow direction of the exhaust gas, it is possible to improve the purification performance of the exhaust gas using the catalyst.

In the straddle type vehicle of the present invention, preferably, the engine body includes a crankcase portion including a crankshaft extending in a left-right direction of the straddle-type vehicle, and at least a portion of the single-combustion-chamber main catalyst is located at the above The center line of the crankshaft is further in front of the front and rear of the above-mentioned straddle type vehicle.

According to this configuration, at least a part of the single-combustion-chamber main catalyst is disposed in front of and behind the straddle-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. Thereby, it is possible to suppress a decrease in temperature before the exhaust gas discharged from the combustion chamber flows into the single-combustion-chamber main catalyst. In other words, it is possible to suppress a decrease in the temperature of the exhaust gas flowing into the single-combustion-chamber main catalyst. Therefore, the purification performance of the exhaust gas using the single catalyst main catalyst can be further improved.

In the straddle type vehicle of the present invention, preferably, the engine body includes a crankcase portion including a crankshaft extending in a left-right direction of the straddle-type vehicle, and the straddle-type vehicle is viewed from a left-right direction, and the single combustion At least a portion of the room main catalyst is located in front of the front-rear direction in a line perpendicular to a center line of the cylinder bore and orthogonal to a center line of the crankshaft.

A straight line orthogonal to the center line of the cylinder bore and orthogonal to the center line of the crankshaft is assumed to be a straight line L. The centerline of the cylinder bore passes through the centerline of the crankshaft. The center line of the cylinder bore The direction extends. Therefore, the straight line L extends downward from the crankshaft. Viewed from the right and left direction, at least a portion of the single catalyst main catalyst is located in front of the straight line L. Therefore, the single combustion chamber main catalyst is disposed at a position close to the combustion chamber. Thereby, it is possible to suppress a decrease in temperature before the exhaust gas discharged from the combustion chamber flows into the single-combustion-chamber main catalyst. In other words, it is possible to suppress a decrease in the temperature of the exhaust gas flowing into the single-combustion-chamber main catalyst. Therefore, the purification performance of the exhaust gas using the single catalyst main catalyst can be further improved.

In the straddle type vehicle of the present invention, preferably, the single-combustion-chamber main catalyst is disposed in a path length from the one combustion chamber to an upstream end of the single-combustion-chamber main catalyst, and is shorter than the single unit A position at which the path from the downstream end of the main catalyst for the combustion chamber to the outlet is long.

According to this configuration, the path length from one combustion chamber to the upstream end of the single-combustion-chamber main catalyst is longer than the path length from the downstream end of the single-combustion-chamber main catalyst to the discharge port. Therefore, the single combustion chamber main catalyst is disposed at a position close to the combustion chamber. Thereby, it is possible to suppress a decrease in temperature before the exhaust gas discharged from the combustion chamber flows into the single-combustion-chamber main catalyst. In other words, it is possible to suppress a decrease in the temperature of the exhaust gas flowing into the single-combustion-chamber main catalyst. Therefore, the purification performance of the exhaust gas using the single catalyst main catalyst can be further improved.

In the straddle type vehicle of the present invention, preferably, the single-combustion-chamber main catalyst is disposed in a path length from the one combustion chamber to an upstream end of the single-combustion-chamber main catalyst, and is shorter than the single unit A path from the downstream end of the main catalyst main combustion chamber to the downstream end of the single combustion chamber exhaust pipe is long.

According to this configuration, the path length from the combustion chamber to the upstream end of the single-combustion-chamber main catalyst is longer than 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. Therefore, the single combustion chamber main catalyst is disposed at a position close to the combustion chamber. Thereby, it is possible to suppress a decrease in temperature before the exhaust gas discharged from the combustion chamber flows into the single-combustion-chamber main catalyst. That is, it is possible to suppress the inflow to a single combustion chamber The temperature of the exhaust gas using the main catalyst is lowered. Therefore, the purification performance of the exhaust gas using the single catalyst main catalyst can be further improved.

In the straddle-type vehicle according to the present invention, it is preferable that the single-combustion-chamber exhaust pipe includes an inner tube and an inner tube covering the upstream of the single-combustion-chamber main catalyst in an upstream direction of the exhaust gas flow direction. Multiple tubes of at least one outer tube.

According to this configuration, at least a part of the single-combustion-chamber exhaust pipe upstream of the single-combustion-chamber main catalyst includes a plurality of tubes. The heat retention effect of the multiple tubes is high. Therefore, it is possible to suppress a decrease in temperature before the exhaust gas discharged from the combustion chamber flows into the single catalyst main catalyst. In other words, it is possible to suppress a decrease in the temperature of the exhaust gas flowing into the single-combustion-chamber main catalyst. Therefore, the purification performance of the exhaust gas using the single catalyst main catalyst can be further improved.

In the straddle-type vehicle of the present invention, preferably, the single-combustion-chamber exhaust pipe has a catalyst arrangement passage portion in which a single-combustion-chamber main catalyst is disposed, and the single-cylinder four-stroke engine unit includes a catalyst arrangement passage portion. Catalyst protector for at least a portion of the outer surface.

According to this configuration, the exhaust pipe for a single combustion chamber has a catalyst arrangement passage portion in which a single catalyst main catalyst is disposed. At least a portion of the outer surface of the catalyst arrangement passage portion is covered by the catalyst protector. Thereby, the temperature fall of the single catalyst main catalyst can be suppressed. Therefore, the purification performance of the exhaust gas using the single catalyst main catalyst can be further improved.

In the straddle type vehicle according to the present invention, preferably, the single-cylinder four-stroke engine unit includes a single-cylinder upstream sub-catalyst, and the single-combustion-chamber upstream sub-catalyst is in the single-combustion-chamber cylinder passage portion or the single unit The combustion chamber exhaust pipe is disposed upstream of the single-combustion-chamber main catalyst in the flow direction of the exhaust gas to purify the exhaust gas. A straddle type vehicle according to any one of claims 1 to 12.

According to this configuration, the single-cylinder four-stroke engine unit is provided with a single combustion chamber upstream sub-catalyst upstream of the single-combustion-chamber main catalyst. Therefore, the exhaust gas is divided into a single combustion In addition to the purification of the kiln by the main catalyst, it is also purified by the upstream sub-catalyst in a single combustion chamber. Therefore, the purification performance of the exhaust gas using the catalyst can be further improved. In addition, it is possible to reduce the size of the single-combustion-chamber main catalyst and the single-combustion-chamber upstream sub-catalyst, respectively, compared to the case where only the single-combustion-chamber main catalyst is provided while maintaining the purification performance of the exhaust gas using the catalyst. Thereby, it is possible to raise the temperature of the single combustion chamber upstream sub-catalyst to the activation temperature more quickly when the engine is started. Therefore, it is possible to improve the purification performance of the exhaust gas using the catalyst while suppressing an increase in the size of the vehicle in the vertical direction.

In the straddle type vehicle of the present invention, preferably, the single-cylinder four-stroke engine unit includes a single sub-catalyst for a combustion chamber, and the single sub-catalyst uses a downstream sub-catalyst in the single-combustion-chamber passage portion, the single unit The inside of the exhaust pipe for the combustion chamber or the muffler for the single combustion chamber is disposed downstream of the single-combustion-chamber main catalyst in the flow direction of the exhaust gas to purify the exhaust gas.

According to this configuration, the single-cylinder four-stroke engine unit is provided with a single combustion chamber upstream sub-catalyst downstream of the single-combustion-chamber main catalyst. Therefore, the exhaust gas is purified by the main catalyst for the single combustion chamber, and also by the downstream sub-catalyst for the single combustion chamber. Therefore, the purification performance of the exhaust gas using the catalyst can be further improved. In addition, it is possible to reduce the size of the single-combustion-chamber main catalyst and the single-combustion-chamber upstream sub-catalyst, respectively, compared to the case where only the single-combustion-chamber main catalyst is provided while maintaining the purification performance of the exhaust gas using the catalyst. Thereby, it is possible to raise the temperature of the single combustion chamber upstream sub-catalyst to the activation temperature more quickly when the engine is started. Therefore, it is possible to improve the purification performance of the exhaust gas using the catalyst while suppressing an increase in the size of the vehicle in the vertical direction.

Moreover, the heat released from the single-combustion-chamber main catalyst can be reduced by miniaturization of the single-combustion-chamber main catalyst. The downstream sub-catalyst for the single combustion chamber 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 an increase in the size of the vehicle in the vertical direction while reducing the purification performance of the exhaust gas using the catalyst, and it is possible to reduce the influence of the heat of the catalyst.

1‧‧‧Motorcycles (straddle-type vehicles)

2‧‧‧ body frame

3‧‧‧ head tube

4‧‧‧Main frame

4a‧‧‧ bracket

4b‧‧‧Bolts

5‧‧‧ seat rail

6‧‧‧ Front fork

7‧‧‧Hands

8‧‧‧ front wheel

8a‧‧‧ axle

9‧‧‧s

10‧‧‧Fenders

11‧‧‧ body shell

11a‧‧‧ front casing

11b‧‧‧ main housing

12‧‧‧ recess

13‧‧‧ Rear shock absorber unit

14‧‧‧ rear arm

14a‧‧‧ pivot

15‧‧‧ Rear wheel

16‧‧‧ engine casing

16a‧‧‧The left and right direction of the engine casing

17‧‧‧ openings

19‧‧‧Single cylinder four-stroke engine unit

20‧‧‧ Engine body

21‧‧‧ crankcase

22‧‧‧Cylinder Department

23‧‧‧ crankcase body

24‧‧‧Cylinder block

24a‧‧‧Cylinder bore

25‧‧‧ cylinder head

26‧‧‧ head cover

27‧‧‧ crankshaft

28‧‧‧Piston

28a‧‧‧ rod

29‧‧‧ combustion chamber

30‧‧‧Cylinder intake passage section (cylinder intake passage section for single combustion chamber)

30a‧‧‧Intake 埠

31‧‧‧Cylinder exhaust passage section (cylinder exhaust passage section for single combustion chamber)

31a‧‧‧Exhaust gas

32‧‧‧Air cleaner

33‧‧‧Intake passage department

34‧‧‧Exhaust pipe (cylinder exhaust pipe for single combustion chamber)

34a‧‧‧Upstream exhaust pipe

34b‧‧‧Down exhaust pipe

35‧‧‧Muffler (cylinder silencer for single combustion chamber)

35e‧‧‧ release

36‧‧‧Exhaust device

37‧‧‧Upstream oxygen detection component

37A, 37B‧‧‧ upstream oxygen detection component

38‧‧‧ Catalyst unit

39‧‧‧Main Catalyst (Main Catalyst for Single Combustion Chamber)

40‧‧‧shell

40a‧‧‧Upstream Access Department

40b‧‧‧Catalyst Disposition Section

40c‧‧‧Downstream Department

41‧‧‧Exhaust path

45‧‧‧Electronic Control Unit

45a‧‧‧Control Department

45b‧‧‧Instruction Department

45c‧‧‧Ignition drive circuit

45d‧‧‧Injector drive circuit

45e‧‧‧ pump drive circuit

46a‧‧‧Engine speed sensor

46b‧‧‧throttle opening sensor

46c‧‧‧Engine temperature sensor

46d‧‧‧Intake pressure sensor

46e‧‧‧Intake air temperature sensor

47‧‧‧Ignition induction coil

48‧‧‧Injector (fuel injection device)

49‧‧‧ fuel pump

50‧‧‧ throttle body

51‧‧‧ throttle valve

200‧‧‧Upstream secondary catalyst (upstream sub-catalyst for single combustion chamber)

400‧‧‧Downstream cocatalyst (downstream side catalyst for single combustion chamber)

437‧‧‧Downstream oxygen detection component

500‧‧‧ Double tube

501‧‧‧Inside

502‧‧‧External management

534‧‧‧Exhaust pipe

600‧‧‧catalyst protector

A1‧‧‧The path length of the cylinder exhaust passage

B1‧‧‧The path length from the upstream end of the exhaust pipe to the upstream end of the main catalyst

Length of path direction of c1‧‧‧main catalyst

Cr1‧‧‧ crankshaft line (center line of crankshaft)

Cy1‧‧‧Cylinder axis (center line of cylinder bore)

Cy2‧‧‧Cylinder axis

D1‧‧‧The path length from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe

D1‧‧‧ distance

D2‧‧‧ distance

D3‧‧‧ distance

E1‧‧‧Long path from the downstream end of the exhaust pipe to the exhaust path of the discharge port

Before F‧‧‧

L‧‧‧Left

L1‧‧‧Line extending through the crankshaft line parallel to the up and down direction

L2‧‧‧ Straight line of crankshaft line and cylinder axis

L3‧‧‧A line that extends through the last end of the intake passage and parallel to the up and down direction

L4‧‧‧ Straight line extending through the front end of the main catalyst and parallel to the up and down direction

L5‧‧‧ Straight line extending through the lowermost end of the engine body and parallel to the front-rear direction

L24‧‧‧ Straight line

R‧‧‧Right

After Re‧‧‧

V1‧‧‧ Intake valve

V2‧‧‧ exhaust valve

W1‧‧‧Maximum width of the main catalyst in the direction perpendicular to the path direction

Θ1‧‧‧ tilt angle of the cylinder axis with respect to the horizontal direction

Θ2‧‧‧ tilt angle of the cylinder axis

Fig. 1 is a side view of a locomotive according to the embodiment of the present invention.

Fig. 2 is a side view showing a state in which the locomotive of Fig. 1 is removed from the outer casing of the vehicle body or the like.

Figure 3 is a bottom view of Figure 2.

Figure 4 is a block diagram of the control block of the locomotive of Figure 1.

Fig. 5 is a schematic view showing the engine body and the exhaust system of the locomotive of Fig. 1.

Figure 6 is a front elevational view of the single-cylinder four-stroke engine unit and the vehicle body casing of the locomotive of Figure 1.

Fig. 7 is a view showing a combination of a front view of the vehicle body casing and a sectional view taken along line A-A of Fig. 1.

Figure 8 is a partial enlarged view of Figure 2.

Fig. 9 is a partially enlarged plan view showing a side view of a locomotive according to another embodiment of the present invention.

Fig. 10 is a partially enlarged plan view showing a side view of a locomotive according to another embodiment of the present invention.

11(a) to 11(e) are schematic diagrams showing an engine body and an exhaust system of a locomotive according to another embodiment of the present invention.

Fig. 12 is a partial cross-sectional view showing an exhaust pipe of a locomotive applied to another embodiment of the present invention.

Figure 13 is a partially enlarged plan view showing a side view of a locomotive 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 straddle type vehicle of the present invention is applied to a locomotive will be described. In the following description, the front, the rear, the left, and the right respectively indicate the front, the rear, the left, and the right of the rider of the locomotive. Among them, the locomotive is placed on the ground level. The symbols F, Re, L, and R attached to the respective drawings represent front, back, left, and right, respectively.

[Overall composition]

Fig. 1 is a side view of the locomotive of the embodiment. Fig. 2 is a side view showing a state in which a vehicle body casing or the like of the locomotive according to the embodiment is removed. Fig. 3 is a bottom view showing a state in which a vehicle body casing or the like of the locomotive according to the embodiment is removed. Fig. 5 is a schematic view showing an engine and an exhaust system of the locomotive according to the embodiment. Figure 8 is a partial enlarged view of Figure 2.

The straddle type vehicle of the present embodiment is a so-called undercarriage type locomotive 1. As shown in FIG. 2, the locomotive 1 is provided with a vehicle body frame 2. The body frame 2 includes a head pipe 3, a main frame 4, and a seat rail 5. The main frame 4 extends from the head pipe 3 toward the lower rear. The middle portion of the seat rail 5 autonomous frame 4 extends rearward and upward.

A rotatable steering shaft is inserted into the head pipe 3. A handle 7 is provided on the upper portion of the steering shaft (refer to FIG. 1). A display device (not shown) is disposed in the vicinity of the handle 7. Vehicle speed, engine speed, various warnings, and the like are displayed on the display device.

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

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

As shown in FIG. 2, the engine body 20 is disposed below the main frame 4. The engine body 20 is supported by the vehicle body frame 2. The engine body 20 is swingably supported by the main frame 4. Specifically, the upper portion of the engine body 20 is fixed to the bracket 4a provided in the main frame 4 by bolts 4b. More specifically, the engine body 20 is fixed to the bracket 4a at the front portion of the crankcase portion 21, which will be described later. Further, the rear portion of the engine body 20 is also fixed to another bracket provided in 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 locomotive 1 has a vehicle body casing 11 that covers the vehicle body frame 2 and the like. Outside the car The casing 11 has a main casing 11b and a front casing 11a. The front outer casing 11a is disposed in front of the head pipe 3. The main casing 11b is disposed behind the head pipe 3. The main casing 11b covers the main frame 4 from above. The main casing 11b covers the seat rail 5 from above. The main casing 11b and the front casing 11a cover the left and right sides of the front portion of the engine body 20. The front outer casing 11a covers the left and right sides of the air cleaner 32.

An opening portion 17 is formed in a front portion of the vehicle body casing 11. The opening portion 17 is formed in the front outer casing 11a. As shown in FIG. 6, the opening 17 is formed in an inverted U shape when viewed from the front. Furthermore, Fig. 6 is a front view of the single-cylinder four-stroke engine unit of the locomotive and the body casing. The maximum width of the opening portion 17 in the left-right direction is larger than the width of the front wheel 8 in the left-right direction. Further, the maximum width of the opening portion 17 in the left-right direction is larger than the width of the fender 10 in the left-right direction. Further, the upper end of the opening portion 17 is located above the front wheel 8. The upper end of the opening portion 17 is located above the engine body 20. The lower end of the opening portion 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 further rearward than the opening 17. Most of the air cleaner 32 is located further rearward than the opening portion 17.

As shown in FIG. 1, the body casing 11 includes an engine casing portion 16. The engine casing portion 16 covers at least a portion of the upper surface of the engine body 20. The engine casing 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 of the engine casing portion 16 orthogonal to the front-rear direction is formed in an inverted U shape. Further, Fig. 7 is a view in which a front view of the vehicle body casing 11 is combined with a sectional view taken along line A-A of Fig. 1. The engine casing portion 16 is formed to be bilaterally symmetrical. The center 16a of the engine casing portion 16 in the left-right direction forms the upper end of the engine casing portion 16. Further, the engine casing portion 16 covers one of the left and right sides of the engine body 20. More specifically, the engine casing portion 16 covers one of the left and right sides of the engine portion 20, which will be described later, of the cylinder portion 22.

As shown in FIG. 1, the maximum distance between the front end of the engine casing portion 16 and the upper surface of the upper surface of the engine body 20 is set to D1. The distance from the front end of the center 16a of the D1 system engine casing portion 16 in the left-right direction to the upper and lower surfaces of the upper surface of the engine body 20 is a distance. The front and rear direction of the engine casing portion 16 and the upper and lower surfaces of the upper surface of the engine body 20 are the largest. The distance is set to D2. The distance from the center of the front left direction of the D2 system engine casing portion 16 in the left-right direction to the upper and lower directions of the upper surface of the engine body 20 is a distance. The maximum distance between the rear end of the engine casing portion 16 and the upper and lower surfaces of the upper surface of the engine body 20 is set to D3. The distance from the front end of the center 16a of the D1 system engine casing portion 16 in the left-right direction to the upper and lower surfaces of the upper surface of the engine body 20 is a distance. The distance D1 is greater than the distance D2. The distance D1 is greater than the distance D3. The upper end (the center 16a in the left-right direction) of the engine casing portion 16 as a whole extends rearward and downward.

As shown in Fig. 1, the portion of the body casing 11 between the seat portion 9 and the head pipe 3 becomes lower. Further, as shown in FIG. 2, the portion of the main frame 4 between the seat portion 9 and the head pipe 3 becomes lower. Thereby, the undercarriage type locomotive 1 is formed behind the head pipe 3 and in front of the seat portion 9 and above the main frame 4 is formed with a recessed portion 12 as viewed from the left and right direction of the vehicle. With the recess 12, the rider easily crosses the vehicle body.

The locomotive 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 portion 33 (a single combustion chamber intake passage portion), an exhaust pipe 34, a muffler 35, and a main catalyst 39 (for a single combustion chamber) The main catalyst) and the upstream oxygen detecting member 37. The details will be described later, and 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 detecting member 37 is disposed upstream of the main pipe 39 of the exhaust pipe 34. The upstream oxygen detecting 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 body 20 includes a crankcase portion 21 and a cylinder portion 22 . The cylinder portion 22 extends forward from the crankcase portion 21.

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

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

As shown in FIG. 5, a cylinder bore 24a is formed in the cylinder block 24. A reciprocating piston 28 is housed in the cylinder bore 24a. The piston 28 is coupled to the crankshaft 27 via a rod 28a. Hereinafter, the center line Cy1 of the cylinder bore 24a is referred to as a cylinder axis Cy1. As shown in FIG. 2, the engine body 20 is disposed such that the cylinder axis Cy1 extends in the front-rear direction (horizontal direction). More specifically, the direction from the crankcase portion 21 of the cylinder axis Cy1 toward the cylinder portion 22 is the front upper side. The inclination angle θ1 (see FIG. 8) of the cylinder axis Cy1 with respect to the horizontal direction is 0 degrees or more and 45 degrees or less. The cylinder axis Cy1 passes through the center of the left and right direction of the locomotive 1. In addition, the center of the left and right direction of the locomotive 1 refers to a position passing through the straight line from 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 as viewed from the up-and-down direction. Further, the cylinder axis Cy1 may be shifted to the right or left from the center in the left-right direction of the locomotive 1.

As shown in FIG. 5, a combustion chamber 29 is formed inside the cylinder portion 22. The combustion chamber 29 is formed by the inner surface of the cylinder bore 24a of the cylinder block 24, the cylinder head 25, and the piston 28. That is, one portion of the combustion chamber 29 is partitioned by the inner surface of the cylinder bore 24a. A front end portion of a spark plug (not shown) is disposed in the combustion chamber 29. Mars is plugged into the combustion chamber 29 to ignite the mixture of fuel and air. As shown in FIG. 2, the combustion chamber 29 is located further forward than the crank line Cr1. Replace this situation with the following expression. A straight line that passes through the crank line Cr1 and extends in parallel with the vertical direction is denoted by L1. The combustion chamber 29 is disposed in front of the straight line L1 as viewed from the left and right direction.

As shown in FIG. 5, 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) are formed in the cylinder head 25. In the present specification, the term "passage portion" means a structure that forms a space (path) through which a gas or the like passes. In the cylinder head 25, an intake port 30a and an exhaust port 31a are formed in a wall portion where the combustion chamber 29 is formed. The cylinder intake passage portion 30 extends from the intake port 30a to a suction port formed on the outer surface (upper surface) of the cylinder head 25. The cylinder exhaust passage portion 31 is self-exhaust The crucible 31a extends to a discharge port formed on the outer surface (lower surface) of the cylinder head 25. The 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.

An intake valve V1 is disposed in the cylinder intake passage portion 30. An exhaust valve V2 is disposed in the cylinder exhaust passage portion 31. The intake valve V1 and the exhaust valve V2 are actuated by a valve mechanism (not shown) that is interlocked with 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 portion 33 is connected to an upstream end (suction port) of the cylinder intake passage portion 30. An exhaust pipe 34 is connected to a downstream end (discharge port) of the cylinder exhaust passage portion 31. The path length of the cylinder exhaust passage portion 31 is a1.

[Composition of air intake system]

Hereinafter, an intake system of the locomotive 1 of the present embodiment will be described. In the description of the intake system of the present specification, the upstream means the upstream of the flow direction of the air supplied to the combustion chamber 29. Further, the downstream means the downstream of 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, the intake passage portion 33 extends from the upper surface of the cylinder portion 22 as viewed from the front. The intake passage portion 33 extends upward from the upper surface of the cylinder portion 22, and is bent to extend to the upper right. It is then bent and extended upward. Moreover, 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 casing portion 16 and the upper surface of the engine body 20. As shown in FIG. 8, a straight line that passes through the last end of the intake passage portion 33 and extends in parallel with the vertical direction is denoted by L3. The straight line L3 is located further rearward than the opening portion 17. That is, the rear end of the intake passage portion 33 is disposed further rearward than the opening portion 17 of the vehicle body casing 11.

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

The injector 48 is provided in front of the intake passage portion 33. One of the injectors 48 is disposed in front of the intake passage portion 33. The injector 48 is disposed further forward than the straight line L3. That is, the injector 48 is disposed further forward than the last 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 referred to as L4. The injector 48 is disposed further forward than the straight line L4. That is, the ejector 48 is disposed further forward than the main catalyst 39. The injector 48 is disposed further rearward than the opening portion 17 of the vehicle body casing 11. Further, at least a portion of the ejector 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 casing 11 are viewed from the front, one portion of the injector 48 can be seen in the opening portion 17 of the vehicle body casing 11. That is, the ejector 48 is not entirely hidden by the vehicle body casing 11 and the single-cylinder four-stroke engine unit 19 when viewed from the front. One portion (lower portion) of the injector 48 is hidden by the cylinder portion 22 (engine body 20) as viewed from the front.

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 can be adjusted by changing the opening degree of the throttle valve 51.

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

[Composition of exhaust system]

Hereinafter, the exhaust system of the locomotive 1 of the present embodiment will be described. In the description of the exhaust system of the present specification, the term "upstream" means upstream of the flow direction of the exhaust gas. Again, the so-called Downstream refers to the downstream of the flow direction of the exhaust gas. Moreover, in the description of the exhaust system of the present specification, the path direction means the flow direction of the exhaust gas.

As described above, the single-cylinder four-stroke engine unit 19 includes the engine body 20, the exhaust pipe 34, the muffler 35, the main catalyst 39, and the upstream oxygen detecting member 37. The muffler 35 has an outlet port 35e facing the atmosphere. The path from the combustion chamber 29 to the discharge port 35e is referred to as 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 muffler 35. The exhaust path 41 is a space through which the 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 the muffler 35. A catalyst unit 38 is provided in the middle of the exhaust pipe 34. The portion of the exhaust pipe 34 that is further upstream than the catalyst unit 38 is set as the upstream exhaust pipe 34a. The portion of the exhaust pipe 34 that is further downstream than the catalyst unit 38 is set as the downstream exhaust pipe 34b. In FIG. 5, the exhaust pipe 34 and the intake passage portion 33 are drawn in a straight line shape for simplification of explanation, but the exhaust pipe 34 and the intake passage portion 33 are not linear.

As shown in FIG. 3, the exhaust pipe 34 is attached to the right side of the locomotive 1. As shown in FIG. 2, one portion of the exhaust pipe 34 is disposed below the engine body 20 as viewed in the left-right direction. Specifically, one portion of the exhaust pipe 34 including the upstream end is disposed below the engine body 20 as viewed in the right and left direction. A straight line that passes through the lowermost end of the engine body 20 and extends in parallel with the front-rear direction is set to L5. One portion of the exhaust pipe 34 is disposed below the straight line L5. That is, one portion of the exhaust pipe 34 is disposed below the lower surface of the engine body 20. The exhaust pipe 34 is disposed further rearward than the opening portion 17 of the vehicle body casing 11. As shown in FIG. 2, one portion of the exhaust pipe 34 is located below the crank line Cr1.

The exhaust pipe 34 has two bent portions. The curved portion upstream of the two curved portions is simply referred to as an upstream curved portion. The curved portion downstream of the two curved portions is simply referred to as a downstream curved portion. As shown in FIG. 2, the upstream curved portion changes the direction in which the exhaust gas flows from the direction extending in the up-and-down direction to the direction extending in the front-rear direction as viewed from the left-right direction. More specifically, when viewed from the left and right direction, the curved portion changes the flow direction of the exhaust gas from the downward direction to the rearward direction. square. Further, as shown in FIG. 3, the upstream curved portion changes the flow direction of the exhaust gas as viewed from below. As shown in Fig. 2, the downstream curved portion changes the flow direction of the exhaust gas from the rearward upper side to the rear side as viewed from the right and left direction. Further, as shown in FIG. 3, the downstream curved portion changes the flow direction of the exhaust gas from the right rear side toward the rear side as viewed from below. The portion further downstream than the downstream curved portion is located below the crank line Cr1. The main catalyst 39 is disposed between the two bent portions.

The muffler 35 flows into the exhaust gas discharged from the downstream end of the exhaust pipe 34. The muffler 35 is connected to the exhaust pipe 34. The muffler 35 is configured to suppress the rhythm of the exhaust gas. Thereby, the muffler 35 can reduce the volume of the sound (exhaust sound) generated by the exhaust gas. A plurality of expansion chambers and a plurality of root tubes connecting the expansion chambers are disposed in the muffler 35. The downstream end of the exhaust pipe 34 is disposed in the expansion chamber of the muffler 35. At the downstream end of the muffler 35, an outlet 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 set to e1. Further, the path length of the expansion chamber in the muffler 35 is the length of the path in which the middle of the inflow port of the expansion chamber is the shortest to the middle of the outlet of the expansion chamber. The exhaust gas passing through the muffler 35 is released to the atmosphere through the discharge port 35e. As shown in Fig. 2, the discharge port 35e is located further rearward than the crank line Cr1.

The main catalyst 39 is disposed in the exhaust pipe 34. The catalyst unit 38 has a cylindrical casing 40 and a main catalyst 39. The upstream end of the housing 40 is connected to the upstream exhaust pipe 34a. The downstream end of the housing 40 is connected to the downstream exhaust pipe 34b. The housing 40 forms 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 of the exhaust gas discharged from the exhaust port 31a 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 in the exhaust path 41 to the utmost extent.

The main catalyst 39 is a so-called three-way catalyst. The three-way catalyst is removed by oxidizing or reducing three types of hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust gas. The three-way catalyst is one of redox catalysts. The main catalyst 39 has a substrate, and a catalyst material attached to the surface of the substrate. The catalyst material has a carrier and a noble metal. The carrier is disposed between the noble metal and the substrate. The carrier carries a precious metal. The precious metal purifies the exhaust gas. Examples of the noble metal include platinum, palladium, rhodium, and the like which respectively remove hydrocarbons, carbon monoxide, and nitrogen oxides.

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

The main catalyst 39 may be a metal substrate catalyst or a ceramic substrate catalyst. The metal substrate catalyst means that the substrate is a catalyst made of metal. The ceramic substrate catalyst means that the substrate is a ceramic catalyst. The base material of the metal base catalyst is formed by, for example, alternately winding a metal wave plate and a metal plate. The substrate of the ceramic substrate catalyst is, for example, a honeycomb structure.

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

As shown in FIG. 5, the casing 40 has a catalyst arrangement passage portion 40b, an upstream passage portion 40a, and a downstream passage portion 40c. The main catalyst 39 is disposed in the catalyst arrangement passage portion 40b. In the path direction, the upstream end and the downstream end of the catalyst arrangement passage portion 40b are at the same position as the upstream end and the downstream end of the main catalyst 39, respectively. The area of the cross section orthogonal 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.

At least a part of the upstream passage portion 40a is formed in a tapered shape. The cone is facing downstream The inner diameter becomes larger. At least a part of the downstream passage portion 40c is formed in a tapered shape. The tapered portion faces downstream and the inner diameter becomes small. 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 path 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 orthogonal 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 as viewed in the left-right direction. Further, as shown in FIG. 2, one of the main catalysts 39 is located below the straight line L5. That is, one portion of the main catalyst 39 is disposed below the lower surface of the engine body 20. Further, as shown in FIG. 3, the main catalyst 39 does not overlap the engine body 20 as viewed from below. Further, the main catalyst 39 may overlap the engine body 20 as viewed from below.

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

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

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 set to b1. The path length b1 includes the path length of the upstream exhaust pipe 34a and the passage portion of the upstream passage portion 40a of the catalyst unit 38. In other words, the path length b1 is long from the downstream end of the cylinder exhaust passage portion 31 to the upstream end of the main catalyst 39. Further, the path length from the downstream end of the autonomous catalyst 39 to the downstream end of the exhaust pipe 34 is taken as d1. The path length d1 includes the path length of the passage portion of the downstream passage portion 40c of the catalyst unit 38 and the downstream exhaust pipe 34b. The path length from the combustion chamber 29 to the upstream end of the main catalyst 39 is a1 + b1. Autonomous catalyst 39 The path from the downstream end 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. Further, 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 detecting member 37 is disposed in the exhaust pipe 34. The upstream oxygen detecting member 37 is disposed upstream of the main catalyst 39. The upstream oxygen detecting member 37 is a sensor that detects the oxygen concentration contained in the exhaust gas. The upstream oxygen detecting member 37 may also be an oxygen sensor that detects whether the oxygen concentration is higher or lower than a specific value. Further, the upstream oxygen detecting member 37 may be a sensor that outputs a plurality of stages or a detection signal that linearly expresses the oxygen concentration (for example, an A/F sensor: Air Fuel Ratio sensor). One end portion (detection portion) of the upstream oxygen detecting member 37 is disposed in the exhaust pipe 34, and the other end portion is disposed outside the exhaust pipe 34. When the detection portion of the upstream oxygen detecting member 37 is heated to a high temperature and becomes an activated state, the oxygen concentration can be detected. The detection result of the upstream oxygen detecting member 37 is output to the electronic control unit 45.

Next, the control of the single-cylinder four-stroke engine unit 19 will be described. Fig. 4 is a block diagram showing the control block of the locomotive of the embodiment.

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

The single-cylinder four-stroke engine unit 19 is provided with an electronic control unit (ECU: Electronic Control Unit) 45 that controls the engine body 20. The electronic control unit 45 is coupled to the engine speed sensor 46a, the engine temperature sensor 46c, the throttle opening sensor 46b, and the intake pressure sensing. Various sensors such as the controller 46d, the intake air temperature sensor 46e, and the vehicle speed sensor are connected. Further, the electronic control unit 45 is connected to the ignition coil 47, the injector 48, the fuel pump 49, a display device (not shown), and the like. The electronic control unit 45 has a control unit 45a and an operation instruction unit 45b. The actuation 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 receive signals from the control unit 45a, and drive the ignition induction coil 47, the injector 48, and the fuel pump 49, respectively. When the ignition coil 47 is driven, the mixed gas is ignited by generating a spark discharge by the spark plug. The fuel pump 49 is connected to the injector 48 via a fuel hose. When the fuel pump 49 is driven, the fuel in the fuel tank (not shown) is pumped to the injector 48.

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

In order to improve the combustion efficiency and the purification efficiency of the main catalyst 39, the air-fuel ratio of the mixed gas in the combustion chamber 29 is preferably a stoichiometric air-fuel ratio (stoichiometric). The control unit 45a increases or decreases the fuel injection amount as needed.

Hereinafter, an example of control (combustion control) of the fuel injection amount by the control unit 45a will be described.

The control unit 45a first calculates the basic fuel injection amount based on the signals of the engine speed sensor 46a, the throttle opening degree sensor 46b, the engine temperature sensor 46c, and the intake pressure sensor 46d. Specifically, a map of the throttle opening degree and the engine speed associated with the intake air amount and a map of the intake air pressure and the engine speed associated with the intake air amount are used to determine the intake air amount. Then, based on the amount of intake air obtained from the map, the basic fuel injection amount at which the target air-fuel ratio can be achieved is determined. When the throttle opening is small, use the intake air A map of the pressure and engine speed associated with the amount of intake air. On the other hand, in the case where the throttle opening degree is large, a map for the throttle opening degree and the engine speed associated with the intake air amount is used.

Moreover, the control unit 45a calculates a feedback correction value for correcting the basic fuel injection amount based on the signal of the upstream oxygen detecting means 37. Specifically, first, based on the signal of the upstream oxygen detecting member 37, it is determined whether the mixed gas is a lean air-fuel ratio or a rich air-fuel ratio. In addition, the rich air-fuel ratio refers to a state in which the fuel is excessive with respect to the stoichiometric air-fuel ratio. The lean air-fuel ratio refers to a state in which the air is excessive with respect to the theoretical air-fuel ratio. When the control unit 45a determines that the mixed gas is the lean air-fuel ratio, the feedback correction value is calculated such that the fuel injection amount of the next time increases. On the other hand, when the control unit 45a determines that the mixed gas is rich air-fuel ratio, the feedback correction value is obtained by reducing the fuel injection amount of the next time.

Moreover, 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 external air pressure, and the like. Further, the control unit 45a calculates a correction value corresponding to the transient characteristics at the time of acceleration and deceleration.

The control unit 45a calculates the fuel injection amount based on the correction values such as the basic fuel injection amount and the feedback correction value. The fuel pump 49 and the injector 48 are driven based on the fuel injection amount obtained in this way. As such, the electronic control unit 45 processes the signals of the upstream oxygen detecting member 37. Further, the electronic control unit 45 performs combustion control based on the signal of the upstream oxygen detecting member 37.

The configuration of the locomotive 1 of the present embodiment has been described above. The locomotive 1 of the present embodiment has the following features.

The cylinder portion 22 (horizontal cylinder portion) is provided so as to extend in the front-rear direction of the locomotive 1 with the cylinder axis Cy1. Therefore, 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 portion of the main catalyst 39 is disposed below the engine body 20. Therefore, the hot gas from the main catalyst 39 rises above the engine body 20 along the periphery of the engine body 20.

At least a portion of the upper surface of the engine body 20 is covered by the engine casing portion 16 of the body casing 11. Further, the engine casing 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 further rearward than the opening portion 17 of the front portion of the vehicle body casing 11. Therefore, the heat of the rise of the autonomous catalyst 39 and the engine body 20 tends to accumulate in the space covered by the vehicle body casing 11 above the engine body 20.

Further, the rear end of the intake passage portion 33 is disposed further rearward than the opening portion 17 of the vehicle body casing 11. At least a portion of the intake passage portion 33 is disposed between the engine outer casing 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 casing 11 above the engine body 20. As described above, the heat of the rise of the autonomous catalyst 39 and the engine body 20 tends to collect in the space covered by the vehicle body casing 11 above the engine body 20. However, the body casing 11 is formed with an opening portion 17 at the front portion thereof. Therefore, the space above the engine body 20 covered by the vehicle body casing 11 is opened toward the front of the vehicle. Therefore, the heat of the space covered by the vehicle body casing 11 gathered above the engine body 20 easily escapes toward the front. That is, the temperature at the front of the space is relatively low. At least a portion of the ejector 48 is disposed further forward than the main catalyst 39. Thus, the injector 48 is less susceptible to the heat of the rise of the autonomous catalyst 39. In addition to this, the ejector 48 is disposed at a position close to the opening portion 17 of the vehicle body casing 11. Therefore, even if the heat is collected in the space covered by the vehicle body casing 11 above the engine body 20, the influence of heat on the ejector 48 can be further suppressed. That is, even if the hot gas autonomous catalyst 39 rises, the influence of heat on the ejector 48 can be suppressed. Therefore, even if the main catalyst 39 is increased in size in order 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 studying the arrangement position of the injectors 48, the influence of the heat of the main catalyst 39 on the injectors 48 can be suppressed. Therefore, it is possible to simplify the structure in which the heat of the main catalyst 39 does not affect the surroundings. Therefore, even if the main catalyst 39 is increased in size in order to improve the purification performance of the main catalyst 39, it is possible to suppress the vehicle from going up and down. Large size.

As described above, the locomotive 1 of the present invention can suppress the increase in the vertical direction of the vehicle while improving the purification performance of the exhaust gas using the catalyst, and can reduce the influence of the heat of the catalyst.

The engine casing portion is formed to have a distance D1 greater than the distance D2 or the distance D3. Further, the distance D1 is a distance between the center of the front and rear direction of the engine casing portion 16 and the upper and lower directions of the upper surface of the engine body 20. The distance D2 is a distance between the center of the front and rear direction of the engine casing portion 16 and the upper and lower directions of the upper surface of the engine body 20. The distance D3 is a distance between the rear end of the engine casing portion 16 and the upper surface of the upper surface of the engine body 20. Therefore, the front portion of the space covered by the vehicle body casing 11 above the engine body 20 has a longer length in the vertical direction than the center or the rear portion of the space in the front and rear directions. Therefore, the heat of the space covered by the vehicle body casing 11 gathered above the engine body 20 is more likely to escape to the front. That is, the temperature of the front portion of the space can be further reduced. Therefore, the influence of heat on the injector 48 can be more suppressed. Therefore, even if the main catalyst 39 is increased in size in order 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 casing portion 16 covers at least a part of the left or right side of the engine body 20. Therefore, heat is more likely to collect in the space above the engine body 20. Further, at least a portion of the air cleaner 32 is disposed between the engine body 20 and the engine casing portion 16. Therefore, the air cleaner 32 blocks the heat of the space above the engine body 20 from dissipating to the front. Thereby, heat is more likely to collect in the space covered by the vehicle body casing 11 above the engine body 20. Even in this case, the influence of heat on the ejector 48 can be reduced by studying the arrangement position of the ejector 48 as described above.

The cross-sectional area S1 of the catalyst arrangement passage portion 40b is larger than the cross-sectional area of at least a portion of the upstream passage portion 40a. Therefore, the cleaning performance of the exhaust gas using the catalyst can be improved as compared with the case where the sectional area S1 is smaller than the area of the cross section of the upstream passage portion 40a orthogonal to the flow direction of the exhaust gas.

At least a part of the main catalyst 39 is disposed in front of the front and rear directions of the locomotive 1 from the crank line Cr1. Therefore, the main catalyst 39 is disposed at a position relatively close to the combustion chamber 29. Thereby, it is possible to suppress the temperature from decreasing before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, it is possible to suppress a decrease in the temperature of the exhaust gas flowing into the main catalyst 39. Therefore, the purification performance of the exhaust gas using the main catalyst 39 can be further improved.

At least a part of the main catalyst 39 is located in front of the straight line L2 as viewed from the left and right direction. The straight line L2 is a line orthogonal to the cylinder axis Cy1 and orthogonal to the crank line Cr1. The cylinder axis Cy1 extends in the front-rear direction. Therefore, the straight line L2 extends downward from the crank line Cr1. Therefore, the main catalyst 39 is disposed at a position close to the combustion chamber 29. Thereby, it is possible to suppress the temperature from decreasing before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, it is possible to suppress a decrease in the temperature of the exhaust gas flowing into the main catalyst 39. Therefore, the purification performance of the exhaust gas using 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 autonomous catalyst 39 to the discharge port 35e. Therefore, the main catalyst 39 is disposed at a position close to the combustion chamber 29. Thereby, it is possible to suppress the temperature from decreasing before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, it is possible to suppress a decrease in the temperature of the exhaust gas flowing into the main catalyst 39. Therefore, the purification performance of the exhaust gas using 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) of the downstream end of the autonomous 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. Thereby, it is possible to further suppress the temperature from decreasing before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, it is possible to further suppress a decrease in the temperature of the exhaust gas flowing into the main catalyst 39. Therefore, the purification performance of the exhaust gas using the main catalyst 39 can be further improved.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various types of modifications can be made without departing from the scope of the claims. change. Further, it can be implemented by appropriately combining the modified examples described later.

The shape of the vehicle body casing 11 is not limited to the shape of the above embodiment. Further, the shape of the engine casing portion 16 is not limited to the shape of the above embodiment. For example, the engine casing portion 16 may not cover the right and left sides of the engine body 20. Further, the engine casing portion 16 may cover the entire right side of the engine body 20 and the entire left side.

The arrangement position of the ejector 48 is not limited to the position of the above embodiment. Among them, at least a part of the ejector 48 is disposed further forward than the main catalyst 39.

In the above embodiment, the ejector 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 disposed to inject fuel into the combustion chamber 29.

In the above embodiment, the ejector 48 is disposed further forward than the main catalyst 39. However, as long as at least a portion of the ejector 48 is disposed further forward than the main catalyst 39. Catalyst FIG. 9 is an example in which one portion of the ejector 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. One of the injectors 48 is disposed further forward than 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.

In the above embodiment, the ejector 48 is disposed further forward than the rear end of the intake passage portion 33. However, the injector 48 may not be disposed further forward than the last end of the intake passage portion 33. Fig. 10 is an example of this. The injector 48 shown in FIG. 10 is provided at the rear of the intake passage portion 33. One of the injectors 48 is disposed further rearward than the straight line L3. Further, the straight line L24 shown in FIG. 10 is a straight line passing through the foremost end of the main catalyst 39 and parallel to the vertical direction. The injector 48 of Fig. 10 is disposed further forward than the straight line L24. That is, the ejector 48 is disposed further forward than the main catalyst 39.

The shape of the exhaust pipe 34 and the intake passage portion 33 of the above embodiment is not limited to the shape of the above embodiment. Moreover, the internal structure of the muffler 35 is not limited to the mode of FIG. The structure shown in the figure.

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

In the above embodiment, one of the exhaust pipes 34 is located below the crank line Cr1. However, a portion of the exhaust pipe (exhaust passage pipe for a single combustion chamber) may also be located above the crank line Cr1.

In the above embodiment, the exhaust pipe 34 is disposed further rearward than the opening portion 17 of the vehicle body casing 11. However, at least a part of the exhaust pipe 34 is disposed further rearward than the opening portion 17 of the vehicle body casing 11.

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

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

The arrangement position of the main catalyst 39 is not limited to the position of the above embodiment. Among them, 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 modification of the arrangement position of the main catalyst will be described.

In the above embodiment, one of the main catalysts 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 entire main catalyst 39 is disposed further forward than the crank line Cr1. However, at least a portion of the main catalyst may be disposed further forward than the crank line Cr1. Further, at least a part of the main catalyst may be disposed further behind the crank line Cr1. square.

The main catalyst 39 of the above embodiment is viewed from the left-right direction, and is disposed entirely in front of the straight line L2. However, it may be observed from the left-right direction, and at least a part of the main catalyst may be disposed in front of the straight line L2. Further, it may be observed from the left-right direction, and 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. Further, 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 autonomous 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. Further, 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 is a path length from the downstream end of the autonomous 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 also be disposed at a position where the path length b1 is longer than the path length d1. Further, the path length b1 is long from the upstream end of the exhaust pipe 34 to the upstream end of the main catalyst 39. The path length d1 is a path length from the downstream end of the autonomous 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 also be plural. When the number of the catalysts is plural, the catalyst for purifying the exhaust gas discharged from the combustion chamber to the maximum extent in the exhaust path corresponds to the single catalyst main catalyst for the present invention. In the case where the catalyst is one, the one catalyst is the main catalyst for the single combustion chamber of the present invention.

It is also possible to provide at least one upstream sub-catalyst (upstream sub-catalyst for a single combustion chamber) upstream of the main catalyst. For example, as shown in FIGS. 11(a), 11(b), and 11(c), the upstream sub-catalyst 200 may be provided in the exhaust pipe 34. 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 a catalyst substance attached to the inner wall of the exhaust pipe 34. In this case, the substrate on which the catalyst 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 substrate disposed inside the exhaust pipe 34. In this case, the upstream sub-catalyst 200 comprises a substrate and a catalyst material. The substrate of the upstream sub-catalyst 200 is, for example, in the form of a plate. The shape of the cross section of the plate-shaped base material orthogonal to the path direction may be S-shaped, may be circular, or may be C-shaped. Further, the upstream sub-catalyst 200 may have a porous structure.

The main catalyst 39 in the exhaust path 41 further purifies the exhaust gas discharged from the combustion chamber 29 than the upstream sub-catalyst 200. In other words, the upstream sub-catalyst 200 has a lower contribution rate to the purified exhaust gas than the main catalyst 39. The purification contribution of each 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, the catalyst disposed upstream of the main catalyst 39 and the upstream sub-catalyst 200 is referred to as a procatalyst, and the catalyst disposed downstream is referred to as a post-catalyst. That is, the upstream sub-catalyst 200 is a procatalyst, and the main catalyst 39 is a post-catalyst. Further, in the following description, the engine unit having the pre-catalyst and the post-catalyst is an engine unit of a variation.

The engine unit of the modified example is operated, and the concentration of the harmful substance contained in the exhaust gas discharged from the discharge port 35e is measured in the preheating state. The method of measuring the exhaust gas is based on the measurement method specified in Europe. In the preheated state, the main catalyst 39 and the upstream sub-catalyst 200 become high temperature and are activated. Therefore, when the main catalyst 39 and the upstream sub-catalyst 200 are in the preheating state, the purification performance can be sufficiently exhibited.

Next, the catalyst unit used in the test was then discharged, and only the substrate of the post-catalyst was disposed. The engine unit in this state is set as the measurement engine unit A. Further, the concentration of the harmful substance contained in the exhaust gas discharged from the discharge port 35e is measured in the same preheating state.

Further, the catalyst for the measurement engine unit A was removed, and only the substrate of the procatalyst was placed. The engine unit in this state is set as the measurement engine unit B. Further, similarly, the concentration of the harmful substance contained in the exhaust gas discharged from the discharge port 35e is measured in the preheating state. In addition, when the upstream sub-catalyst 200 (pre-catalyst) is a structure in which a catalyst substance is directly adhered to the inner wall of the exhaust pipe 34, the exhaust pipe 34 corresponds to a base material. The arrangement of only the base material of the upstream sub-catalyst 200 instead of the upstream sub-catalyst 200 means that the catalyst material is not adhered to the inner wall of the exhaust pipe 34.

The engine unit A for measurement has a procatalyst without a post catalyst. The engine unit B for measurement does not have a pre-catalyst and a post-catalyst. Therefore, the purification contribution degree of the procatalyst (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. Moreover, the purification contribution degree of the post-catalyst (main catalyst 39) was calculated from the difference between the measurement result of the measurement engine unit A and the measurement result of the engine unit of the variation.

The purification ability of the upstream sub-catalyst 200 may be smaller than the purification ability of the main catalyst 39, and may be greater than the purification ability of the main catalyst 39. Further, the purification ability of the upstream sub-catalyst 200 is smaller than the purification ability of the main catalyst 39, which means that the purification rate of the exhaust gas when only the upstream sub-catalyst 200 is provided is smaller than the purification rate of the exhaust gas when only the main catalyst 39 is provided.

By providing the upstream sub-catalyst upstream of the main catalyst 39, the following effects can be obtained. In addition to being purified by the main catalyst 39, the exhaust gas is also purified by the upstream sub-catalyst. Therefore, the purification performance of the exhaust gas using the catalyst can be further improved. In addition, it is possible to reduce the size of the main catalyst 39 and the upstream sub-catalyst, respectively, compared to the case where only the main catalyst 39 is provided while maintaining the purification performance of the exhaust gas using the catalyst. Thereby, the upstream sub-catalyst can be heated up to the activation temperature more quickly when the engine is started. Therefore, it is possible to improve the purification performance of the exhaust gas using the catalyst while suppressing an increase in the size of the vehicle in the vertical direction.

At least one downstream sub-catalyst (a downstream sub-catalyst for a single combustion chamber) may also be disposed downstream of the main catalyst. The downstream sub-catalyst may be either a porous structure or a porous structure. A specific example in the case of a non-porous structure is the same as that of the upstream sub-catalyst 200. For example, as shown in FIGS. 11(d) and 11(e), the downstream sub-catalyst 400 may be provided in the exhaust pipe 34. Further, the downstream sub-catalyst may be provided in the muffler 35. The downstream sub-catalyst may also be disposed further downstream than the downstream end of the exhaust pipe 34. Further, in the case where the downstream sub-catalyst is provided, the upstream sub-catalyst 200 may be disposed upstream of the main catalyst.

By providing the downstream sub-catalyst downstream of the main catalyst 39, the following effects can be obtained. In addition to being purified by the main catalyst 39, the exhaust gas is also purified by the downstream sub-catalyst. Therefore, the purification performance of the exhaust gas using the catalyst can be further improved. In addition, it is possible to reduce the size of the main catalyst 39 and the downstream sub-catalyst, respectively, compared to the case where only the main catalyst 39 is provided while maintaining the purification performance of the exhaust gas using the catalyst. Thereby, the main catalyst 39 can be heated up to the activation temperature more quickly at the time of starting the engine. Therefore, it is possible to improve the purification performance of the exhaust gas using the catalyst while suppressing an increase in the size of the vehicle in the vertical direction.

Further, by the miniaturization of the main catalyst 39, the heat released by the autonomous catalyst 39 can be reduced. The downstream sub-catalyst can be disposed at a position away from the ejector 48 in the front-rear direction. Therefore, the influence of heat on the injector 48 can be more suppressed.

In the case where a downstream sub-catalyst is provided downstream of the main catalyst, the main catalyst is in the exhaust path to purify the exhaust gas discharged from the combustion chamber to the utmost extent. The purification contribution of each of the main catalyst and the downstream sub-catalyst can be measured by a measurement method described in the modification of the upstream sub-catalyst. The "precatalyst" in the above measurement method is referred to as a main catalyst, and the "post catalyst" is referred to as a "downstream sub-catalyst".

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

In the case where a downstream sub-catalyst is disposed downstream of the main catalyst, the main catalyst deteriorates faster than the downstream sub-catalyst. Therefore, if the cumulative travel distance becomes long, there is a case where the magnitude relationship between the purification contributions of the main catalyst and the downstream sub-catalyst is reversed. The single catalyst main catalyst of the present invention is used to maximize the purification of exhaust gas discharged from the combustion chamber in the exhaust path. This produces a state prior to the reversal phenomenon as described above. That is, this is a state in which the accumulated travel distance does not reach a certain distance (for example, 1000 km).

In the above embodiment, the main catalyst 39 is a three-way catalyst. However, the single catalyst main catalyst of the present invention may not be a three-way catalyst. The single catalyst combustor may also be a catalyst that removes either or both of hydrocarbons, carbon monoxide, and nitrogen oxides. Further, the single catalyst main catalyst may not be a redox catalyst. The main catalyst may also be an oxidation catalyst or a reduction catalyst which removes harmful substances only by either oxidation or reduction. As an example of the reduction catalyst, there is a catalyst which removes nitrogen oxides by a reduction reaction. This variation can also 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, the length of the path direction of the single catalyst main catalyst of the present invention may be shorter than the maximum width in the direction perpendicular to the path direction. Among them, the single catalyst main catalyst of the present invention is configured to purify exhaust gas to the utmost in the exhaust path. The term "exhaust path" as used herein refers to the path from the combustion chamber to the outlet opening facing the atmosphere.

The single catalyst main catalyst of the present invention may also be configured as a plurality of catalysts in close proximity. Each sheet has a substrate and a catalyst material. Here, the proximity finger is separated from each other by a distance shorter than the length of the path direction of each piece. The composition of the plurality of substrates may be one type or plural kinds. The noble metal of the catalyst material of the plurality of catalysts may be one type or plural kinds. The composition of the carrier of the catalyst material may be one type or plural kinds. This variation can also be applied to the upstream sub-catalyst and the downstream sub-catalyst.

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

In the case where the upstream sub-catalyst 200 is provided upstream of the main catalyst 39, for example, as shown in FIG. 11(b), the upstream oxygen detecting member 37 is preferably disposed upstream of the upstream sub-catalyst 200. Further, for example, as shown in FIG. 11(a), the upstream oxygen detecting member 37 may be provided downstream of the upstream sub-catalyst 200. Further, for example, as shown in FIG. 11(c), two upstream oxygen detecting members 37A and 37B may be provided upstream and downstream of the upstream sub-catalyst 200.

At least one downstream oxygen detecting member may also be disposed downstream of the main catalyst. The specific configuration of the downstream oxygen detecting member is the same as that of the upstream oxygen detecting member 37 of the above embodiment. For example, as shown in FIGS. 11(a), 11(b), 11(d), and 11(e), the downstream oxygen detecting member 437 may be provided in the exhaust pipe 34. Further, the downstream oxygen detecting member may be provided in the muffler 35. The downstream oxygen detecting member may also be disposed to detect the exhaust gas downstream of the downstream end of the exhaust pipe 34. Further, when the main catalyst is provided in the cylinder exhaust passage portion, the downstream oxygen detecting 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 arrangement position of the downstream oxygen detecting member 437 may be either of the following two positions. For example, as shown in FIG. 11(d), the downstream oxygen detecting member 437 may be disposed downstream of the main catalyst 39 and upstream of the downstream sub-catalyst 400. Further, for example, as shown in FIG. 11(e), the downstream oxygen detecting member 437 may be disposed downstream of the downstream sub-catalyst 400. Further, a downstream oxygen detecting member may be provided upstream and downstream of the downstream sub-catalyst 400, respectively.

The electronic control unit processes the signal of the downstream oxygen detecting member in the case where the downstream oxygen detecting member is disposed downstream of the main catalyst. The electronic control unit can also determine the purification ability of the main catalyst based on the signal of the downstream oxygen detecting member. Further, the electronic control unit may determine the purification ability of the main catalyst based on the signals of the upstream oxygen detecting member and the downstream oxygen detecting member. Further, the electronic control unit may perform combustion control based on signals from the upstream oxygen detecting member and the downstream oxygen detecting member.

An example of a specific method for determining the purification ability of the main catalyst based on the signal of the downstream oxygen detecting member will be described. First, the fuel injection amount is controlled such that the mixed gas repeats the rich air-fuel ratio and the lean air-fuel ratio for a certain period of time (several seconds). Then, the delay of the signal change of the downstream oxygen detecting member with respect to the change in the fuel injection amount is detected. When the delay of the signal change of the downstream oxygen detecting member is large, it is determined that the purification ability of the main catalyst is lower than a specific level. In this case, a signal is sent from the electronic control unit to the display device. Further, a warning light (not shown) of the display device is turned on. Thereby, the rider can be prompted to replace the main catalyst.

Thus, deterioration of the main catalyst can be detected by using a signal of the downstream oxygen detecting member disposed downstream of the main catalyst. Therefore, it is possible to notify before the deterioration of the main catalyst reaches a certain level, prompting the replacement of the main catalyst. Thereby, the initial performance related to exhaust gas purification of the straddle type vehicle can be maintained for a longer period of time.

An example of a specific method for determining the purification ability of the main catalyst based on the signals of the upstream oxygen detecting member and the downstream oxygen detecting member will be described. For example, the change in the signal of the upstream oxygen detecting member and the change in the signal of the downstream oxygen detecting member can be compared to determine the purification ability of the main catalyst. By using the signals of the two oxygen detecting members disposed upstream and downstream of the main catalyst, it is possible to more accurately detect the degree of deterioration of the main catalyst. Therefore, it is possible to prompt replacement of the single-combustion-chamber main catalyst at a more appropriate timing than in the case where the deterioration of the main catalyst is determined using only the signal of the downstream oxygen detecting means. Thereby, it is possible to use one main catalyst for a longer period of time while maintaining the initial performance related to the exhaust gas purification performance of the vehicle.

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

By using the signals of the two oxygen detecting members disposed upstream and downstream of the main catalyst, the actual purification state of the main catalyst can be grasped. Therefore, when fuel control is performed based on signals of two oxygen detecting members, the accuracy of fuel control can be improved. Further, the upstream oxygen detecting member can stably detect the oxygen concentration in the exhaust gas. Therefore, the accuracy of fuel control can be further improved. Thereby, the deterioration of the main catalyst can be slowed down, so that the initial performance related to the exhaust purification of the straddle type vehicle can be maintained for a longer period of time.

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

The upstream oxygen detecting member may also have a built-in heater. When the detection portion of the upstream oxygen detecting member is heated to a high temperature and is in an activated state, the oxygen concentration can be detected. Therefore, when the upstream oxygen detecting member incorporates the heater, the detection unit is heated by the heater at the start of the operation, whereby the oxygen detection can be started as soon as possible. This variation can also be applied to the downstream oxygen detecting member in the case where the downstream oxygen detecting member is disposed downstream of the main catalyst.

At least a portion of the exhaust pipe upstream of the main catalyst may also comprise multiple tubes. The multiple tube has an inner tube and at least one outer tube covering the inner tube. Fig. 12 shows an example in which at least a portion of the exhaust pipe 534 further upstream than the main catalyst includes the double pipe 500. For example, as shown in FIG. 12, at least a portion of the exhaust pipe 534 further upstream than the main catalyst may also include a double pipe. The double tube 500 includes an inner tube 501 and a tube 502 that covers the outer tube 501. In Fig. 12, the inner tube 501 and the outer tube 502 are only in contact with each other at both ends. The inner tube and the outer tube of the multiple tubes may also be in contact with portions other than the both ends. For example, the inner tube and the outer tube may also be in contact with the curved portion. The contact area is preferably smaller than the uncontacted area. Moreover, the inner tube and the outer tube can also be in overall contact. In the case where the exhaust pipe has multiple pipes, it is preferred that the upstream oxygen detecting member is disposed in the middle of the multiple pipes or more downstream of the heavy pipes. The heat retention effect of the multiple tubes is high. Therefore, can It is possible to suppress the temperature from decreasing before the exhaust gas discharged from the combustion chamber 29 flows into the main catalyst 39. That is, it is possible to suppress a decrease in the temperature of the exhaust gas flowing into the main catalyst 39. Therefore, the purification performance of the exhaust gas using the main catalyst 39 can be further improved.

For example, as shown in FIG. 13, at least a part of the outer surface of the catalyst arrangement passage portion 40b may be covered by the catalyst protector 600. The catalyst protector 600 is formed in a substantially cylindrical shape. The catalyst arrangement passage portion 40b and the main catalyst 39 can be protected by providing the catalyst protector 600. Further, by providing the catalyst protector 600, it is possible to suppress a decrease in the temperature of the main catalyst 39. Therefore, the purification performance of the exhaust gas using the main catalyst 39 can be further improved.

In the above embodiment, the gas flowing through the exhaust path 41 during engine driving is only the exhaust gas discharged from the combustion chamber 29. However, the single-cylinder four-stroke engine unit of the present invention may also include a secondary air supply mechanism that supplies air to the exhaust path. The specific configuration of the secondary air supply mechanism is a well-known configuration. The secondary air supply mechanism may be configured to forcibly supply air to the exhaust path by the 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 means is provided with a pilot valve that opens and closes in response to the pressure rhythm caused by the exhaust gas. In the case where the secondary air supply mechanism is provided, the arrangement position of the upstream oxygen detecting member may be set to be upstream or downstream of the position where the air flows in.

In the above embodiment, only one exhaust port 31a is provided in one combustion chamber 29. However, it is also possible to provide a plurality of exhaust ports in one combustion chamber. For example, the case where the variable valve mechanism is provided corresponds to this modification. Wherein, the exhaust path extending from the plurality of exhaust gases is collected upstream of the main catalyst. The exhaust path extending from the plurality of exhaust ports is preferably collected in the cylinder portion.

The combustion chamber of the present invention may be configured to have a main combustion chamber and a sub-combustion chamber connected to the main combustion chamber. In this case, a 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 block 24 are separate members. Of course Moreover, the crankcase body and the cylinder block can also be integrally formed. Further, in the above embodiment, the cylinder block 24, the cylinder head 25, and the head cover 26 are separate members. However, either or both of the cylinder block, the cylinder head, and the head cover may be integrally formed.

In the above embodiment, a locomotive is illustrated as a straddle type vehicle having a 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 is moved by the power of the single cylinder four-stroke engine unit. The straddle type vehicle of the present invention may also be a locomotive type locomotive. Further, the straddle type vehicle of the present invention may be a straddle type vehicle other than the locomotive. The so-called straddle-type vehicle refers to all the vehicles that the rider rides in such a state as to sit on the saddle. The straddle type vehicle includes a locomotive, a three-wheeled vehicle, a four-wheeled off-road vehicle (ATV: All Terrain Vehicle), an on-water locomotive, 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 which has the shortest path length from the combustion chamber. The downstream end of the main catalyst refers to the end of the main catalyst which has the longest path from the combustion chamber. The same definitions can be applied to the upstream and downstream ends of the elements other than the main catalyst.

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

In the present specification and the present invention, the path length of the exhaust path means the path length of the line in the middle of the exhaust path. Further, the path length of the expansion chamber of the muffler refers to the length of the path connecting the center of the inflow port of the expansion chamber to the center of the outlet of the expansion chamber as the shortest.

In the present specification, the path direction refers to the direction of the path passing through the center of the exhaust path and the direction in which the exhaust gas flows.

In the present specification, the expression of the area of the cross section orthogonal to the path direction of the passage portion is used. Further, in the present specification and the present invention, the passage portion and the exhaust gas flow side are used. The representation of the area of the orthogonal section. 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 may be the area of the outer peripheral surface of the passage portion.

Further, in the present specification and the present invention, the member or the straight line extends in the A direction, and it is not only the case where the member or the straight line is arranged in parallel with the A direction. The member or the straight line extends in the A direction, and includes a case where the member or the straight line is inclined within a range of ±45° with respect to the A direction. Furthermore, the A direction does not refer to a specific direction. It is possible to replace the A direction with the horizontal direction or the front and rear direction.

The crankcase body 23 of the present specification corresponds to the crankcase portion 18 in the specification of the basic application of the present application. The cylinder block 24 of the present specification corresponds to the cylinder portion 24 in the specification of the above-mentioned basic application. The engine body 20 of the present specification corresponds to the engine 20 in the specification of the above basic application. The cylinder exhaust passage portion 31 of the present specification corresponds to the passage portion forming the exhaust passage P2 in the specification of the above-mentioned basic application.

The present invention also encompasses all embodiments that are identified, equivalent, modified, deleted, combined (e.g., combined with features of various embodiments), modified, and/or modified, as recognized by the disclosure of the present specification. The limitation of the scope of the patent application should be broadly understood based on the terms used in the scope of the patent application. The limitation of the scope of the patent application is not limited to the embodiments described in the present specification or the embodiments of the present invention. Such an embodiment is to be understood as non-exclusive. For example, in this specification, the terms "better" and "good" are non-exclusive and mean "preferably, but not limited to" and "good but not limited to".

1‧‧‧Motorcycles (straddle-type vehicles)

2‧‧‧ body frame

3‧‧‧ head tube

4‧‧‧Main frame

4a‧‧‧ bracket

4b‧‧‧Bolts

5‧‧‧ seat rail

6‧‧‧ Front fork

8‧‧‧ front wheel

8a‧‧‧ axle

13‧‧‧ Rear shock absorber unit

14‧‧‧ rear arm

14a‧‧‧ pivot

15‧‧‧ Rear wheel

16a‧‧‧The left and right direction of the engine casing

17‧‧‧ openings

19‧‧‧Single cylinder four-stroke engine unit

20‧‧‧ Engine body

21‧‧‧ crankcase

22‧‧‧Cylinder Department

23‧‧‧ crankcase body

24‧‧‧Cylinder block

25‧‧‧ cylinder head

26‧‧‧ head cover

27‧‧‧ crankshaft

29‧‧‧ combustion chamber

32‧‧‧Air cleaner

33‧‧‧Intake passage department

34‧‧‧Exhaust pipe (cylinder exhaust pipe for single combustion chamber)

35‧‧‧Muffler (cylinder silencer for single combustion chamber)

35e‧‧‧ release

37‧‧‧Upstream oxygen detection component

38‧‧‧ Catalyst unit

39‧‧‧Main Catalyst (Main Catalyst for Single Combustion Chamber)

40‧‧‧shell

48‧‧‧Injector (fuel injection device)

Cr1‧‧‧ crankshaft line (center line of crankshaft)

Cy1‧‧‧Cylinder axis (center line of cylinder bore)

Before F‧‧‧

L1‧‧‧Line extending through the crankshaft line parallel to the up and down direction

L2‧‧‧ Straight line of crankshaft line and cylinder axis

L3‧‧‧A line that extends through the last end of the intake passage and parallel to the up and down direction

L4‧‧‧ Straight line extending through the front end of the main catalyst and parallel to the up and down direction

L5‧‧‧ Straight line extending through the lowermost end of the engine body and parallel to the front-rear direction

After Re‧‧‧

Claims (13)

A straddle type vehicle characterized in that it is equipped with a single-cylinder four-stroke engine unit, and the single-cylinder four-stroke engine unit has an engine body having a horizontal cylinder portion, and the horizontal cylinder portion is formed with a part of the cylinder hole a combustion chamber in which the inner surface is partitioned, a single-combustion-chamber intake passage portion through which the air supplied to the one combustion chamber is circulated, and a single-combustion-chamber exhaust passage portion through which the exhaust gas discharged from the one combustion chamber flows And the center line of the cylinder bore extends along the front and rear directions of the straddle type vehicle; the single combustion chamber intake passage portion is disposed at least a portion above the engine body and connected to the engine An upper end of the single-combustion-chamber intake passage portion of the main body; at least a portion of the single-combustion exhaust pipe is disposed below the engine body and connected to the single combustion chamber cylinder of the engine body a downstream end of the exhaust passage portion; a muffler for a single combustion chamber having a discharge port facing the atmosphere and connected to The single-combustion-chamber exhaust pipe supplies the exhaust gas flowing from the downstream end of the single-combustion-chamber exhaust pipe to the discharge port to reduce the sound generated by the exhaust gas; the single-combustion-chamber main catalyst is disposed in The exhaust pipe of the single combustion chamber is disposed at least partially below the engine body, and is exhausted from the combustion chamber to the maximum extent in an exhaust path from the one combustion chamber to the discharge port. And a fuel injection device provided in the single combustion chamber intake passage portion or the single combustion chamber cylinder intake passage portion, at least in part in the front-rear direction Arranged further forward than the single-combustion-chamber main catalyst, injecting fuel into the air sucked from the upstream end of the single-combustion-chamber intake passage portion; and having a vehicle body casing including an engine casing portion, An opening portion is formed in a front portion thereof, and the engine casing portion covers at least a part of an upper surface of the engine body, and both end portions of the straddle type vehicle in a left-right direction are located below the center of the left-right direction. The air intake passage portion for the single combustion chamber is disposed at least partially between the engine casing portion and the upper surface of the engine body, and the rear end thereof is disposed at the opening of the vehicle body casing in the front-rear direction. Further, the single combustion chamber exhaust pipe is disposed at least in part in the front-rear direction at a position rearward of the opening of the vehicle body casing. The straddle-type vehicle according to claim 1, wherein the vehicle body casing is formed in such a manner that a maximum distance between a front end of the engine casing portion and an upper surface of the engine body upper surface is greater than a front center direction of the engine casing portion Or the rear end is at a maximum distance from the upper surface of the upper surface of the engine body. A straddle-type vehicle according to claim 1 or 2, wherein said engine casing portion covers at least a portion of a left side or a right side of said engine body. The straddle-type vehicle according to any one of claims 1 to 3, comprising: a vehicle body frame having a head pipe and a main frame extending from the head pipe toward a rear lower side, wherein the vehicle body casing is The upper portion covers at least a part of the main frame, and the engine body is disposed below the main frame and is supported by the main frame without swinging. The straddle-type vehicle according to any one of claims 1 to 4, wherein the single-combustion-chamber exhaust pipe has a catalyst arrangement passage portion in which a single combustion-chamber main catalyst is disposed, and an upstream passage portion connected to the above The upstream end of the catalyst arrangement passage portion; The area of the cross section orthogonal to the flow direction of the exhaust gas in the catalyst arrangement passage portion is larger than the area of the cross section orthogonal to the flow direction of the exhaust gas of at least a part of the upstream passage portion. The straddle-type vehicle according to any one of claims 1 to 5, wherein 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 portion of the single-chamber main catalyst It is located in front of the front and rear of the straddle type vehicle above the center line of the crankshaft. The straddle-type vehicle according to any one of claims 1 to 6, wherein the engine body has a crankcase portion including a crankshaft extending in a left-right direction of the straddle-type vehicle, and the straddle-type vehicle is viewed from a left-right direction. At least a part of the single-combustion-chamber main catalyst is located in front of the front-rear direction orthogonal to a center line of the cylinder bore and perpendicular to a center line of the crankshaft. The straddle-type vehicle according to any one of claims 1 to 7, wherein the single-combustion-chamber main catalyst system is disposed in a path length from the one combustion chamber to an upstream end of the single-combustion-chamber main catalyst, which is shorter than a path length The path from the downstream end of the single-combustion-chamber main catalyst to the discharge port is long. The straddle-type vehicle according to any one of claims 1 to 8, wherein the single-combustion-chamber main catalyst system is disposed in a path length from the one combustion chamber to an upstream end of the single-combustion-chamber main catalyst, which is shorter than The path from the downstream end of the single-combustion-chamber main catalyst to the downstream end of the single-combustion-chamber exhaust pipe is long. The straddle-type vehicle according to any one of claims 1 to 9, wherein at least a part of the single-combustion-chamber exhaust pipe upstream of the single-combustion-chamber main catalyst in the flow direction of the exhaust gas includes an inner pipe and a cover a plurality of tubes of at least one outer tube of the inner tube. A straddle-type vehicle according to any one of claims 1 to 10, wherein said single combustion chamber is used The exhaust pipe has a catalyst arrangement passage portion in which a single catalyst main catalyst is disposed, and the single-cylinder four-stroke engine unit includes a catalyst protector that covers at least a part of a surface other than the catalyst arrangement passage portion. The straddle-type vehicle according to any one of claims 1 to 11, wherein the single-cylinder four-stroke engine unit includes a single-cylinder upstream sub-catalyst, and the single-combustion-chamber upstream sub-catalyst is in the single-combustion-chamber cylinder passage portion Or the exhaust gas in the single combustion chamber is disposed upstream of the single-combustion-chamber main catalyst in the flow direction of the exhaust gas to purify the exhaust gas. The straddle-type vehicle according to any one of claims 1 to 12, wherein the single-cylinder four-stroke engine unit includes a single combustion chamber downstream sub-catalyst, and the single combustion chamber uses a downstream sub-catalyst in the single combustion chamber cylinder passage portion. The exhaust gas in the single combustion chamber or the muffler for the single combustion chamber is disposed downstream of the single-combustion-chamber main catalyst in the flow direction of the exhaust gas to purify the exhaust gas.