TWI611098B - Vehicle and single cylinder four-stroke engine unit - Google Patents

Abstract

An object of the present invention is to provide a vehicle having a single-cylinder four-stroke engine unit that can simplify the support structure and improve the exhaust gas purification performance of the catalyst, and maintain the initial performance of the vehicle with respect to exhaust gas purification for a long time. The upstream end of the single-combustion-chamber main catalyst 39 is arranged upstream of the exhaust gas flow direction than the upstream end of the single-combustion-chamber muffler 35. The single-combustion-chamber main catalyst 39 is in the exhaust path from one combustion chamber 29 to the discharge outlet 35e to purify the exhaust gas discharged from one combustion chamber 29 to the greatest extent. An upstream oxygen detection member 36 for a single combustion chamber is disposed further upstream than the main catalyst 39 for a single combustion chamber. Further downstream of the single-combustion-chamber main catalyst 39, a single-combustion-chamber downstream oxygen detection member 37 is disposed.

Description

Vehicle and single-cylinder four-stroke engine unit

The invention relates to a vehicle and a single-cylinder four-stroke engine unit.

Patent Document 1 discloses a vehicle equipped with a single-cylinder four-stroke engine unit. This single-cylinder four-stroke engine unit has a structure in which a catalyst is arranged in a muffler. The catalyst purifies the exhaust gas discharged from the engine body. The muffler reduces the sound produced by the exhaust gas.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2007-85234

The industry looks forward to improving exhaust purification performance of vehicles equipped with single-cylinder four-stroke engine units. Therefore, it is considered to arrange the catalyst further upstream. That is, it is considered to arrange at least a part of the catalyst upstream of the muffler.

In order to maintain the purification performance for a long time, it is considered to increase the size of the catalyst. However, when a large-sized catalyst is disposed upstream of the muffler, a supporting structure must be added to ensure vibration resistance. The muffler and engine are supported on the body frame. However, in general, an exhaust pipe connecting an engine body and a muffler is not supported on a vehicle body frame. Therefore, if the enlarged catalyst is arranged in the exhaust pipe, the exhaust pipe is liable to vibrate. Therefore, in order to ensure vibration resistance, a supporting structure must be added.

An object of the present invention is to provide a vehicle having a single-cylinder four-stroke engine unit and a single-cylinder four-stroke engine unit capable of simplifying the support structure and improving the exhaust gas purification performance of the catalyst and maintaining the initial performance of the vehicle with respect to exhaust gas purification for a long time. .

Conventionally, as a device for maintaining the initial performance of a vehicle with respect to exhaust gas purification for a longer period of time, the size of a catalyst has been considered. The inventors of the present case have reexamined the reason for making the catalyst larger.

Depending on the vehicle's usage conditions, the degree of catalyst degradation varies. That is, there is an example in which the deterioration of the catalyst is promoted according to the use condition of the vehicle. In order to maintain the initial performance of the vehicle with respect to exhaust gas purification for a longer period of time when the catalyst deteriorates, the catalyst usually has room for purification. In this way, the catalyst has a large capacity because it has room for purification capability.

However, the inventors of the present case conducted research, and as a result, they learned that examples of degradation advancement occur less frequently. Therefore, the inventor of this case does not assume that the catalyst with less frequent degradation can promote the purification ability of the catalyst, but considers to maintain the initial performance of the vehicle with regard to exhaust purification for a longer time based on the following two different technical ideas .

A technical idea to control the engine in a way that slows down the progress of catalyst degradation. By slowing down the progress of catalyst degradation, it is possible to reduce the frequency of occurrence of instances of catalyst degradation progress. The other is to be able to prompt the replacement of the catalyst before the deterioration of the catalyst reaches a certain level.

As a concept for achieving such a technical idea, it is thought to adopt the following configuration. That is, it is conceivable to arrange oxygen detecting means upstream and downstream of the catalyst, and to provide a control device that processes signals of the two oxygen detecting means.

According to this technical idea, it is believed that the size of the catalyst can be maintained and the initial performance of the vehicle with respect to exhaust purification can be maintained for a longer time. Furthermore, by suppressing the enlargement of the catalyst, even if the catalyst is arranged in the exhaust pipe, it is possible to suppress the vibration of the exhaust pipe. With this, recognize In order to improve the purification performance of the catalyst and simplify the supporting structure of the single-cylinder four-stroke engine unit.

The vehicle of the present invention is characterized in that it is equipped with a single-cylinder four-stroke engine unit. The single-cylinder four-stroke engine unit is provided with an engine body having a cylinder portion formed with a combustion chamber and supplied from the above. A single cylinder exhaust passage portion for a single combustion chamber through which exhaust gas from a combustion chamber flows; a single combustion chamber exhaust pipe connected to the downstream end of the single exhaust chamber cylinder exhaust passage portion of the engine body; a single combustion chamber A muffler having a release port facing the atmosphere is connected to the exhaust pipe for the single combustion chamber to allow the exhaust gas flowing in from the downstream end of the exhaust pipe for the single combustion chamber to flow to the exhaust port to reduce the The sound produced; a main catalyst for a single combustion chamber, which is arranged in the exhaust passage portion of the cylinder for the single combustion chamber or in the exhaust pipe for the single combustion chamber, and whose upstream end is arranged more than the silencer for the single combustion chamber. The upstream end is closer to the upstream of the exhaust gas flow direction, and the exhaust path from the above one combustion chamber to the above-mentioned outlet is purified to the greatest extent. Exhaust gas exhausted from the combustion chamber; upstream oxygen detection means for a single combustion chamber, which is arranged in the exhaust path of the single combustion chamber cylinder or the exhaust pipe for the single combustion chamber is located closer to the exhaust gas than the main catalyst for the single combustion chamber Upstream of the flow direction, the oxygen concentration in the exhaust gas is detected; the downstream oxygen detection member for the single combustion chamber is located in the cylinder exhaust passage of the single combustion chamber, the exhaust pipe for the single combustion chamber, or the muffler for the single combustion chamber. It is located downstream of the single-combustion-chamber main catalyst, downstream of the flow direction of the exhaust gas, and detects the oxygen concentration in the exhaust gas; and a control device that processes the signal of the single-combustion-chamber upstream oxygen detection member and the single-combustion-chamber downstream Signal of oxygen detection component.

According to this configuration, the single-cylinder four-stroke engine unit provided in the vehicle includes an engine body, a single combustion chamber exhaust pipe, a single combustion chamber muffler, a single combustion chamber main catalyst, a single combustion chamber upstream oxygen detection member, and a single A downstream oxygen detection member for a combustion chamber and a control device. The engine body includes a cylinder portion in which a single combustion chamber and a single cylinder exhaust passage portion for the combustion chamber are formed. Single combustion chamber cylinder exhaust passage is supplied from one combustion Exhaust gas from the chamber circulates. The single combustion chamber exhaust pipe is connected to the downstream end of the single combustion chamber cylinder exhaust passage portion of the engine body. The single-chamber silencer has a vent facing the atmosphere. The single-combustion-chamber muffler is connected to the single-combustion-chamber exhaust pipe so that exhaust gas flowing in from the downstream end of the single-combustion-chamber exhaust pipe flows to the discharge port. The muffler for single combustion chamber reduces the sound generated by exhaust gas. The single-combustion-chamber main catalyst is arranged in a single-combustion-chamber exhaust passage or a single-combustion-chamber exhaust pipe. The main catalyst for a single combustion chamber is used in the exhaust path from one combustion chamber to the outlet to purify the exhaust gas discharged from one combustion chamber to the greatest extent. The upstream end of the single-combustion-chamber main catalyst is disposed further upstream than the upstream end of the single-combustion-chamber silencer. That is, the main catalyst for a single combustion chamber is disposed relatively close to the combustion chamber. Therefore, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be improved.

In addition, a single combustion chamber upstream oxygen detection member is disposed in a single combustion chamber cylinder exhaust passage portion or a single combustion chamber exhaust pipe. The single-combustion-chamber upstream oxygen detection member is disposed more upstream than the single-combustion-chamber main catalyst. Further, a single-combustion-chamber downstream oxygen detecting member is disposed in a single-combustion-chamber exhaust passage section, a single-combustion-chamber exhaust pipe, or a single-combustion-chamber silencer. The single-combustion-chamber downstream oxygen detection member is disposed further downstream than the single-combustion-chamber main catalyst. The control device processes a signal from an upstream oxygen detection member for a single combustion chamber and a signal from a downstream oxygen detection member for a single combustion chamber.

The signal of the downstream oxygen detection member for a single combustion chamber disposed downstream of the main catalyst for a single combustion chamber can be used to detect the deterioration of the main catalyst for a single combustion chamber. Therefore, the deterioration of the single-combustion-chamber main catalyst can be notified before the deterioration reaches a certain level, and the replacement of the single-combustion-chamber main catalyst can be prompted. Thereby, the initial performance of the vehicle with respect to exhaust gas purification can be maintained for a longer time by using a plurality of single combustion chamber main catalysts. The deterioration of the single-combustion-chamber main catalyst can be detected without using a signal from an upstream oxygen detection member for a single-combustion chamber. It is also possible to detect a main catalyst for a single combustion chamber based on a signal from a downstream oxygen detection unit for a single combustion chamber and a signal from an upstream oxygen detection unit for a single combustion chamber. Of degradation. By using the signals of the two oxygen detection members, the degree of deterioration of the main catalyst for a single combustion chamber can be detected more accurately. Therefore, it is possible to prompt the replacement of the single-combustion-chamber main catalyst at a more appropriate timing than when the deterioration of the single-chamber-combustion main catalyst is detected using only the signal of the downstream oxygen detection member for the single-combustion chamber. Thereby, a single main catalyst for a combustion chamber can be used for a longer time.

In addition, the actual purification status of the main catalyst for a single combustion chamber can be grasped by the signal of the upstream oxygen detection means for a single combustion chamber and the signal of the downstream oxygen detection means for a single combustion chamber. Therefore, when the amount of fuel to be supplied to the combustion chamber is controlled based on the signals from the two oxygen detection members (hereinafter, referred to as combustion control), the accuracy of the combustion control can be improved. This makes it possible to slow down the deterioration of the main catalyst for a single combustion chamber. Therefore, the initial performance of the vehicle with respect to exhaust purification can be maintained for a longer time.

In this way, the initial performance of the vehicle with respect to exhaust gas purification can be maintained for a longer time without increasing the size of the main catalyst for a single combustion chamber. Thereby, the support structure can be simplified, and the initial performance of the vehicle with respect to exhaust gas purification can be maintained for a long time.

According to the above circumstances, a vehicle provided with the single-cylinder four-stroke engine unit of the present invention can simplify the support structure and improve the catalyst's exhaust gas purification performance, and maintain the vehicle's initial performance regarding exhaust gas purification for a long time.

In the vehicle of the present invention, it is preferable that the engine body has a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, and at least a part of the one combustion chamber of the cylinder portion is disposed at a centerline of the crankshaft. Further to the front and rear directions of the vehicle, the release port of the single-combustion-chamber silencer is disposed further behind the vehicle than the centerline of the crankshaft, and at least a portion of the single-combustion-chamber main catalyst is used. It is arranged in front of the vehicle in the front-rear direction than the centerline of the crankshaft.

According to this configuration, at least a part of the combustion chamber of the cylinder portion is disposed more forward than the center line of the crankshaft. The outlet of the muffler for a single combustion chamber is arranged at the centerline of the crankshaft Further back. The main catalyst for a single combustion chamber is provided between the combustion chamber and the release port. At least a part of the main catalyst for a single combustion chamber is disposed more forward than the centerline of the crankshaft. Therefore, the main catalyst for a single combustion chamber is disposed closer to the combustion chamber. Therefore, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be further improved.

In the vehicle of the present invention, the engine body may include a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, and at least a part of the one combustion chamber of the cylinder portion may be disposed at a centerline of the crankshaft. Further to the front and rear directions of the vehicle, the release port of the single-combustion-chamber silencer is disposed further behind the vehicle than the centerline of the crankshaft, and at least a portion of the single-combustion-chamber main catalyst It is arranged behind the front-rear direction of the vehicle than the centerline of the crankshaft.

In the vehicle of the present invention, it is preferable that the engine body has a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, the cylinder portion of the engine body has a cylinder hole in which a piston is disposed, and the above of the cylinder portion At least a part of one combustion chamber is disposed in front of the vehicle in the front-rear direction relative to the centerline of the crankshaft, and the release port of the single-combustion chamber silencer is disposed in the vehicle in the front-rear direction relative to the centerline of the crankshaft When the vehicle is viewed from left to right, at least a portion of the single combustion chamber main catalyst is located in a straight line orthogonal to the center line of the cylinder bore and orthogonal to the center line of the crankshaft, and is in front of the vehicle. .

According to this configuration, at least a part of the combustion chamber of the cylinder portion is disposed more forward than the center line of the crankshaft. The outlet of the muffler for a single combustion chamber is arranged further behind the centerline of the crankshaft. The main catalyst for a single combustion chamber is provided between the combustion chamber and the release port. The center line of the cylinder bore extends from the crankshaft in any direction upward, forward, upward, or forward. Here, 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 straight line L extends from the crankshaft in any of the forward, downward, and downward directions. When viewed from left and right, single combustion At least a part of the main catalyst for the combustion chamber is located in front of the straight line L. Therefore, the main catalyst for a single combustion chamber is arranged closer to the combustion chamber. Therefore, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be further improved.

In the vehicle of the present invention, the engine body may include a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, the cylinder portion of the engine body may have a cylinder hole in which a piston is arranged, At least a part of one combustion chamber is disposed in front of the vehicle in the front-rear direction relative to the centerline of the crankshaft, and the release port of the single-combustion chamber silencer is disposed in the vehicle in the front-rear direction relative to the centerline of the crankshaft When the vehicle is viewed from the left and right, at least a part of the single combustion chamber main catalyst is located on a straight line orthogonal to the center line of the cylinder bore and orthogonal to the center line of the crankshaft. .

In the vehicle of the present invention, it is preferable that the single-combustion-chamber main catalyst is disposed at a path from the one combustion chamber to the upstream end of the single-combustion-chamber main catalyst, and is shorter than the single-combustion-chamber main catalyst. A long path from the downstream end to the release port.

According to this configuration, the path length from one combustion chamber to the upstream end of the single-chamber main catalyst is shorter than the path length from the downstream end of the single-chamber main catalyst to the release port. Therefore, the main catalyst for a single combustion chamber can be arranged closer to the combustion chamber. Therefore, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be further improved.

In the vehicle of the present invention, it is preferable that the single-combustion-chamber main catalyst is disposed at a path from the one combustion chamber to the upstream end of the single-combustion-chamber main catalyst, and is shorter than the single-combustion-chamber main catalyst The path from the downstream end to the downstream end of the single combustion chamber exhaust pipe 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 shorter 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 main catalyst for a single combustion chamber can be arranged more Near the combustion chamber. Therefore, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be further improved.

In the vehicle of the present invention, the single-combustion-chamber main catalyst may also be arranged at a path from the one combustion chamber to the upstream end of the single-combustion-chamber main catalyst, which is longer than the downstream end of the single-combustion-chamber main catalyst. The long path to the downstream end of the single combustion chamber exhaust pipe.

In the vehicle of the present invention, the upstream oxygen detection member for the single combustion chamber may be disposed at a path from the one combustion chamber to the upstream end of the upstream oxygen detection member for the single combustion chamber, which is shorter than the path from the single combustion chamber. The upstream oxygen detecting member has a long path to the upstream end of the single combustion chamber main catalyst.

According to this configuration, the path from one combustion chamber to the upstream end of the upstream oxygen detection member for a single combustion chamber is longer than the path from the upstream oxygen detection member for a single combustion chamber to the upstream end of the main catalyst for a single combustion chamber. Therefore, the single-combustion-chamber upstream oxygen detection member is disposed closer to the combustion chamber. Therefore, when the engine is started, the upstream oxygen detection member for a single combustion chamber can be heated up to the activation temperature more quickly. Therefore, the detection accuracy of the upstream oxygen detection member for a single combustion chamber can be improved. Thereby, the combustion control based on the signal of the upstream oxygen detection member for a single combustion chamber can be performed more accurately. As a result, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be further improved. In addition, by improving the accuracy of the combustion control, the progress of the deterioration of the main catalyst for a single combustion chamber can be slowed down. Therefore, the initial performance of the vehicle with respect to exhaust purification can be maintained for a longer time.

In the vehicle of the present invention, the upstream oxygen detection member for the single combustion chamber may be arranged at a path from the one combustion chamber to the upstream end of the upstream oxygen detection member for the single combustion chamber, which is longer than the upstream from the single combustion chamber. The oxygen detecting member has a long path to the upstream end of the single combustion chamber main catalyst.

According to this configuration, the path from one combustion chamber to the upstream end of the upstream oxygen detection member for a single combustion chamber is longer than that from the upstream oxygen detection member for a single combustion chamber to a single combustion chamber. The path upstream of the main catalyst is long. Therefore, the single-combustion-chamber upstream oxygen detection member is disposed near the main catalyst for the single-combustion chamber. Therefore, the oxygen concentration of the exhaust gas flowing into the main catalyst for a single combustion chamber can be detected more accurately. Thereby, the combustion control based on the signal of the upstream oxygen detection member for a single combustion chamber can be performed more accurately. As a result, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be further improved. In addition, by improving the accuracy of the combustion control, the progress of the deterioration of the main catalyst for a single combustion chamber can be slowed down. Therefore, the initial performance of the vehicle with respect to exhaust purification can be maintained for a longer time.

In the vehicle of the present invention, it is preferable that the exhaust pipe for a single combustion chamber includes a catalyst arrangement passage portion in which the main catalyst for the single combustion chamber is disposed, and an upstream passage portion connected to an upstream end of the catalyst arrangement passage portion, And, an area of a cross section orthogonal to an exhaust gas flow direction of at least a part of the upstream passage portion is smaller than an area of a cross section orthogonal to the exhaust gas flow direction of the catalyst arrangement passage portion.

According to this configuration, the single combustion chamber exhaust pipe includes a catalyst arrangement passage portion and an upstream passage portion. The catalyst disposing passage portion disposes a main catalyst for a single combustion chamber. The upstream passage portion is connected to an upstream end of the catalyst arrangement passage portion. It is assumed that the area of the cross section of the catalyst arrangement passage portion orthogonal to the flow direction of the exhaust gas is Sa. At least a part of the upstream passage portion has an area of a cross section orthogonal to the flow direction of the exhaust gas smaller than Sa. Therefore, as the main catalyst for a single combustion chamber, a catalyst having a large cross-sectional area can be used. Therefore, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be improved.

In the vehicle of the present invention, it is preferable that at least a part of the exhaust pipe for the single combustion chamber, which is located upstream of the exhaust gas flow direction than the main catalyst for the single combustion chamber, includes an inner pipe and at least one covering the inner pipe. Multiple tubes for outer tube.

According to this configuration, at least a part of the exhaust pipe for a single combustion chamber more than the main catalyst for a single combustion chamber includes multiple pipes. The multiple pipe includes an inner pipe and at least one outer pipe covering the inner pipe. By providing multiple pipes, it is possible to suppress a decrease in exhaust gas temperature. Therefore, when the engine is started, the upstream oxygen detection member for a single combustion chamber can be heated up to activation more quickly. temperature. Therefore, the detection accuracy of the upstream oxygen detection member for a single combustion chamber can be improved. Thereby, the combustion control based on the signal of the upstream oxygen detection member for a single combustion chamber can be performed more accurately. As a result, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be further improved. In addition, by improving the accuracy of the combustion control, the progress of the deterioration of the main catalyst for a single combustion chamber can be slowed down. Therefore, the initial performance of the vehicle with respect to exhaust purification can be maintained for a longer time.

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

According to this configuration, the single combustion chamber exhaust pipe has a catalyst arrangement passage portion. The catalyst disposing passage portion disposes a main catalyst for a single combustion chamber. At least a part of the outer surface of the catalyst arrangement passage portion is covered by a catalyst protector. By providing a catalyst protector, the temperature of the main catalyst for a single combustion chamber can be increased more quickly. Therefore, the exhaust gas purification performance of the main catalyst for a single combustion chamber can be improved.

In the vehicle of the present invention, it is preferable that the single-cylinder four-stroke engine unit includes an upstream sub-catalyst for a single combustion chamber, and the upstream sub-catalyst for the single combustion chamber is located in an exhaust passage portion of the cylinder for the single-combustion chamber or the single combustion. The exhaust pipe for the chamber is disposed upstream of the exhaust gas flowing direction than the main catalyst for the single combustion chamber, and purifies the exhaust gas.

According to this configuration, the single-combustion-chamber upstream subcatalyst is provided in the single-combustion-chamber exhaust passage portion or the single-combustion-chamber exhaust pipe. The upstream sub-catalyst for a single combustion chamber is located further upstream than the main catalyst for a single combustion chamber. Therefore, the deterioration of the upstream sub-catalyst for a single combustion chamber progresses faster than the main catalyst for a single combustion chamber. However, even if the degradation of the upstream sub-catalyst for a single combustion chamber reaches a certain level, the purification performance of the exhaust gas can be maintained by the single-combustion main catalyst. Therefore, the initial performance of the vehicle with respect to exhaust purification can be maintained for a longer time.

In the vehicle of the present invention, the upstream oxygen detection member for the single combustion chamber may be disposed upstream of the exhaust gas flowing direction than the upstream sub-catalyst for the single combustion chamber.

According to this configuration, the upstream oxygen detection member for a single combustion chamber is disposed more upstream than the upstream sub-catalyst for a single combustion chamber. Therefore, the upstream oxygen detection means for a single combustion chamber can detect the oxygen concentration of the exhaust gas flowing into the upstream sub-catalyst for a single combustion chamber. Therefore, by performing the combustion control based on the signal of the upstream oxygen detection member for a single combustion chamber, the exhaust gas purification performance of the upstream sub-catalyst for a single combustion chamber can be improved.

In the vehicle of the present invention, it is preferable that the single-cylinder four-stroke engine unit includes a downstream subcatalyst for a single combustion chamber, and the downstream subcatalyst for the single combustion chamber is in the exhaust pipe for the single combustion chamber or the single combustion chamber. The muffler is arranged in the downstream of the exhaust gas flow direction than the main catalyst for a single combustion chamber to purify the exhaust gas.

According to this configuration, the downstream subcatalyst for a single combustion chamber is provided in the exhaust pipe for a single combustion chamber or the silencer for a single combustion chamber. The downstream sub-catalyst for a single combustion chamber is located further downstream than the main catalyst for a single combustion chamber. Therefore, the deterioration of the main catalyst for a single combustion chamber progresses faster than the downstream sub-catalyst for a single combustion chamber. However, even if the degradation of the main catalyst for a single combustion chamber reaches a certain level, the purification performance of the exhaust gas can be maintained by the downstream sub-catalyst for a single combustion chamber. Therefore, the initial performance of the vehicle with respect to exhaust purification can be maintained for a longer time.

In the vehicle of the present invention, the above-mentioned single-combustion-chamber downstream oxygen detection member may be disposed further downstream than the single-combustion-chamber main catalyst in the direction of exhaust gas flow, and further disposed than the single-combustion-chamber downstream sub-catalyst. Upstream of the direction of exhaust gas flow.

In the vehicle of the present invention, the single-combustion-chamber downstream oxygen detection member may be disposed further downstream than the single-combustion-chamber downstream sub-catalyst in the direction of exhaust gas flow.

In the vehicle of the present invention, it is preferable that the control device includes a notification device that determines the purification ability of the main catalyst for the single combustion chamber based on a signal from the downstream oxygen detection member for the single combustion chamber. Judging the above single combustion Notify when the purification ability of the main catalyst for the room decreases to a certain level.

According to this configuration, the control device determines the purification ability of the main catalyst for the single combustion chamber based on a signal from the downstream oxygen detection means for the single combustion chamber. Furthermore, when the control device determines that the purification ability of the catalyst has decreased to a specific level, the notification device notifies. Thereby, it is possible to prompt replacement of the single-combustion-chamber main catalyst before the deterioration of the single-chamber-combustion main catalyst reaches a certain level. Thereby, the initial performance of the vehicle with respect to exhaust gas purification can be maintained for a longer time by using a plurality of single combustion chamber main catalysts.

In the vehicle of the present invention, it is preferable that the single-cylinder four-stroke engine unit includes a fuel supply device that supplies fuel to the one combustion chamber, and the control device is based on a signal from the upstream oxygen detection means for the single combustion chamber. And the signal of the downstream oxygen detecting means for the single combustion chamber, to control the amount of fuel supplied from the fuel supply device to the one combustion chamber.

By using the signal of the upstream oxygen detection member for a single combustion chamber and the signal of the downstream oxygen detection member for a single combustion chamber, the actual purification status of the main catalyst for a single combustion chamber can be grasped. Therefore, by performing the combustion control based on the signals of the two oxygen detecting members, the accuracy of the combustion control can be improved. This makes it possible to slow down the deterioration of the main catalyst for a single combustion chamber. As a result, the initial performance of the vehicle regarding the exhaust purification performance can be maintained for a longer time.

The single-cylinder four-stroke engine unit of the present invention is characterized in that it is the above-mentioned single-cylinder four-stroke engine unit mounted on the vehicle, and is provided with an engine body having a cylinder portion formed with a combustion chamber and a supply chamber. A single cylinder exhaust passage portion for a single combustion chamber through which exhaust gas discharged from the above one combustion chamber flows; a single exhaust pipe for a single combustion chamber connected to the downstream end of the exhaust passage portion of the single cylinder for a combustion chamber of the engine body; A muffler for a combustion chamber has a release port facing the atmosphere, and is connected to the exhaust pipe for the single combustion chamber so that the exhaust gas flowing in from the downstream end of the exhaust pipe for the single combustion chamber flows to the release port, reducing the cause. Exhaust sound; main catalyst for single combustion chamber, its configuration It is located in the exhaust passage of the single combustion chamber cylinder or the exhaust pipe of the single combustion chamber, and its upstream end is arranged upstream of the exhaust gas flow direction than the upstream end of the single combustion chamber muffler. The exhaust path from one combustion chamber to the above-mentioned outlet is to purify exhaust gas exhausted from the above-mentioned one combustion chamber to the greatest extent; the upstream oxygen detection member for a single combustion chamber is located in the cylinder exhaust passage of the single combustion chamber or the single combustion The exhaust pipe for the chamber is located upstream of the exhaust gas flow direction than the main catalyst for the single combustion chamber, and detects the oxygen concentration in the exhaust gas; the downstream oxygen detection member for the single combustion chamber exhausts the gas in the cylinder for the single combustion chamber. The passage part, the exhaust pipe for the single combustion chamber, or the silencer for the single combustion chamber is disposed downstream of the exhaust gas flow direction than the main catalyst for the single combustion chamber, and detects the oxygen concentration in the exhaust gas; and a control device that The signal of the upstream oxygen detection member for the single combustion chamber and the signal of the downstream oxygen detection member for the single combustion chamber are processed.

With this configuration, the same effects as those of the vehicle of the present invention described above can be obtained.

According to the present invention, in a vehicle provided with a single-cylinder four-stroke engine unit, the support structure can be simplified and the catalyst's exhaust gas purification performance can be improved, and the vehicle's initial performance regarding exhaust gas purification can be maintained for a long time.

1, 50, 80, 120‧‧‧ locomotive (vehicle)

2, 53, 81, 121‧‧‧ body frame

3‧‧‧ head tube

4‧‧‧ main frame

4a‧‧‧ bracket

4b‧‧‧bolt

5‧‧‧ seat rail

6‧‧‧ Fork

7‧‧‧handle

8‧‧‧ front wheel

8a‧‧‧ axle

9‧‧‧ seat

10‧‧‧ Fender

11‧‧‧ body shell

12‧‧‧ recess

13‧‧‧ rear shock absorption unit

14‧‧‧ hind arm

14a‧‧‧ Pivot

15‧‧‧ rear wheel

16‧‧‧Main shell

17‧‧‧ front case

19‧‧‧ single-cylinder four-stroke engine unit

20, 61, 94, 133‧‧‧ engine body

21‧‧‧Crankcase

22, 63, 99, 137‧‧‧ cylinder

23, 64, 100, 138‧‧‧‧Crankcase body

24, 65, 101, 139‧‧‧ cylinder block

24a, 65a, 101a, 139a ‧‧‧ cylinder bore

25, 66, 102, 140‧‧‧ cylinder head

26, 67, 103, 141‧‧‧ head covers

27, 68, 104, 142‧‧‧ crankshaft

28, 69, 105, 143‧‧‧ Pistons

29, 70, 106, 144‧‧‧combustion chamber

30‧‧‧Cylinder intake passage

30a‧‧‧air inlet

31, 72, 108, 146‧‧‧ cylinder exhaust passage section (cylinder exhaust passage section for single combustion chamber)

31a, 72a, 108a, 146a‧‧‧ exhaust port

32‧‧‧air cleaner

33‧‧‧Air inlet pipe

34, 75, 111, 149‧‧‧ exhaust pipe (exhaust pipe for single combustion chamber)

34a, 75a, 111a, 149a‧‧‧ Upstream exhaust pipe

34b, 75b, 111b, 149b ‧‧‧ downstream exhaust pipe

35, 76, 112, 150‧‧‧ muffler (muffler for single combustion chamber)

35a‧‧‧upstream end of silencer

35e, 76e, 112e, 150e, 435e, 535e

36, 77, 113, 151‧‧‧ upstream oxygen detection means (upstream oxygen detection means for single combustion chamber)

36A, 36B‧‧‧upstream oxygen detection component

37, 78, 114, 152‧‧‧ downstream oxygen detection component (downstream oxygen detection component for single combustion chamber)

38, 79, 115, 153, 2115‧‧‧ catalyst units

39, 116, 154, 180‧‧‧Main catalyst (main catalyst for single combustion chamber)

40, 181, 117, 155‧‧‧ shell

40a, 117a, 155a, 181a, 2117a

40b, 117b, 155b, 181b, 2117b‧‧‧ catalyst arrangement passage

40c, 117c, 155c, 181c, 2117c ‧‧‧ downstream channel

41, 118, 156, 182‧‧‧ exhaust path

45‧‧‧ECU

45a‧‧‧Control Department

45b‧‧‧action instructions

45c‧‧‧Ignition driving circuit

45d‧‧‧Injector drive circuit

45e‧‧‧Pump drive circuit

46a‧‧‧engine speed sensor

46b‧‧‧throttle opening sensor

46c‧‧‧engine temperature sensor

46d‧‧‧Air Pressure Sensor

46e‧‧‧Intake air temperature sensor

47‧‧‧Ignition induction coil

48‧‧‧ Ejector

49‧‧‧ fuel pump

51‧‧‧ fuel tank

52‧‧‧Seat

53a‧‧‧head tube

53b‧‧‧Upper main frame

53c‧‧‧Under the main frame

53d‧‧‧Seat frame

54‧‧‧body shell

55‧‧‧handle

56‧‧‧ Fork

57‧‧‧ front wheel

58‧‧‧ hind arm

59‧‧‧ rear wheel

60‧‧‧Single-cylinder four-stroke engine unit

62‧‧‧Crankcase

71‧‧‧cylinder intake passage

71a‧‧‧air inlet

73‧‧‧air cleaner

74‧‧‧Air inlet pipe

76a‧‧‧upstream end of silencer

81a‧‧‧ head tube

81b‧‧‧Main frame

81c‧‧‧Side Frame

81d‧‧‧ post frame

81e‧‧‧Seat frame

82‧‧‧handle

83‧‧‧ Fork

84‧‧‧ front wheel

85‧‧‧foot board

86‧‧‧Seat

87‧‧‧body shell

87a‧‧‧Front housing

87b‧‧‧ leg guard

87c‧‧‧Main shell

87d‧‧‧ bottom case

88‧‧‧ rear wheel

89‧‧‧ Pivot

90L‧‧‧Left link member

90R‧‧‧Right link member

91‧‧‧ Pivot

93‧‧‧Single-cylinder four-stroke engine unit

95‧‧‧Power Transmission Department

96‧‧‧Air deflector

97‧‧‧fan

98‧‧‧Crankcase

107‧‧‧cylinder intake passage

107a‧‧‧air inlet

110‧‧‧Air inlet pipe

112a‧‧‧upstream end of silencer

121a‧‧‧ head tube

121b‧‧‧Main frame

121c‧‧‧bottom frame

121d‧‧‧cross member

122L‧‧‧Left seat rail

122R‧‧‧Right seat rail

123‧‧‧handle

124‧‧‧ Fork

125‧‧‧ front wheel

126‧‧‧Seat

127‧‧‧ body shell

127a‧‧‧Front case

127b‧‧‧Main shell

127c‧‧‧ bottom case

128‧‧‧ rear wheel

129‧‧‧ Pivot

130L‧‧‧Left link member

130R‧‧‧Right link member

131‧‧‧ Pivot

132‧‧‧Single-cylinder four-stroke engine unit

134‧‧‧Power Transmission Department

135‧‧‧water cooling device

135a‧‧‧Shell

136‧‧‧Crankcase

145‧‧‧cylinder intake passage

145a‧‧‧air inlet

147‧‧‧air cleaner

148‧‧‧Air inlet pipe

Upstream end of 150a‧‧‧silencer

234‧‧‧Exhaust pipe (exhaust pipe for single combustion chamber)

234a‧‧‧upstream exhaust pipe

234b‧‧‧downstream exhaust pipe

275‧‧‧Exhaust pipe (exhaust pipe for single combustion chamber)

275a‧‧‧upstream exhaust pipe

275b‧‧‧downstream exhaust pipe

300‧‧‧upstream sub-catalyst (upstream sub-catalyst for single combustion chamber)

301‧‧‧downstream sub-catalyst (downstream sub-catalyst for single combustion chamber)

334‧‧‧Exhaust pipe (exhaust pipe for single combustion chamber)

334a‧‧‧upstream exhaust pipe

334b‧‧‧downstream exhaust pipe

400‧‧‧The first expansion chamber

401‧‧‧ 2nd expansion chamber

402‧‧‧3rd expansion chamber

403‧‧‧The first tube

404‧‧‧Tube 2

405‧‧‧Tube 3

434, 534, 634, 1534, 2534‧‧‧ exhaust pipe (exhaust pipe for single combustion chamber)

435‧‧‧silencer (silencer for single combustion chamber)

435a‧‧‧upstream end of silencer

500‧‧‧The first expansion chamber

501‧‧‧ 2nd expansion chamber

502‧‧‧3rd expansion chamber

503‧‧‧The first tube

504‧‧‧ 2nd tube

505‧‧‧Tube 3

534b‧‧‧downstream exhaust pipe

535‧‧‧silencer (silencer for single combustion chamber)

535a‧‧‧upstream end of silencer

600‧‧‧ double tube

601‧‧‧Inner tube

602‧‧‧ Outer tube

700‧‧‧ catalyst protector

1534b‧‧‧downstream exhaust pipe

2111‧‧‧Exhaust pipe (exhaust pipe for single combustion chamber)

2111a‧‧‧upstream exhaust pipe

2111b‧‧‧downstream exhaust pipe

2117‧‧‧shell

2149‧‧‧Exhaust pipe (exhaust pipe for single combustion chamber)

2149a‧‧‧upstream exhaust pipe

2149b‧‧‧downstream exhaust pipe

2534b‧‧‧downstream exhaust pipe

a1‧‧‧Cylinder exhaust path length

a2‧‧‧Cylinder exhaust path length

a3‧‧‧Cylinder exhaust path length

a4‧‧‧Cylinder exhaust path length

b1‧‧‧Long path from upstream end of exhaust pipe to upstream end of main catalyst

b2‧‧‧The path length from the upstream end of the exhaust pipe to the upstream end of the main catalyst

b3‧‧‧The path length from the upstream end of the exhaust pipe to the upstream end of the main catalyst

b4‧‧‧The path length from the upstream end of the exhaust pipe to the upstream end of the main catalyst

b11‧‧‧Long path from upstream end of exhaust pipe to upstream end of main catalyst

b12‧‧‧Long path from upstream end of exhaust pipe to upstream end of main catalyst

b13‧‧‧Long path from upstream end of exhaust pipe to upstream end of main catalyst

b14‧‧‧Long path from upstream end of exhaust pipe to upstream end of main catalyst

b21‧‧‧Long path from upstream end of exhaust pipe to upstream end of main catalyst

c1‧‧‧length of path direction of main catalyst

c2‧‧‧length of path direction of main catalyst

c3‧‧‧length of path direction of main catalyst

c4‧‧‧length of path direction of main catalyst

Cr1, Cr2, Cr3, Cr4 ‧‧‧ crankshaft line (center line of crankshaft)

Cy1, Cy2, Cy3, Cy4‧‧‧ cylinder axis (center line of cylinder hole)

d1‧‧‧The path length from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe

d2‧‧‧The path from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe is long

d3‧‧‧The path length from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe

d4‧‧‧The path length from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe

d11‧‧‧The path from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe is long

d12‧‧‧The path from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe is long

d13‧‧‧The path length from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe

d14‧‧‧The path length from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe

d21‧‧‧The path from the downstream end of the autonomous catalyst to the downstream end of the exhaust pipe is long

e1‧‧‧The path length of the exhaust path from the downstream end of the exhaust pipe to the release port

e2‧‧‧The path of the exhaust path from the downstream end of the exhaust pipe to the release port is long

e3‧‧‧The path of the exhaust path from the downstream end of the exhaust pipe to the release port is long

e4‧‧‧The path of the exhaust path from the downstream end of the exhaust pipe to the release port is long

F‧‧‧ before

G1‧‧‧space

h1‧‧‧ The path from the combustion chamber to the upstream oxygen detection member is long

h2‧‧‧ The path length from the upstream oxygen detection member to the upstream end of the main catalyst

h3‧‧‧The path from the combustion chamber to the upstream oxygen detection component is long

h4‧‧‧ The path length from the upstream oxygen detection member to the upstream end of the main catalyst

h5‧‧‧ The path from the combustion chamber to the upstream oxygen detection member is long

h6‧‧‧ The path length from the upstream oxygen detection member to the upstream end of the main catalyst

h7‧‧‧Long path from the combustion chamber to the upstream oxygen detection component

h8‧‧‧The path length from the upstream oxygen detection member to the upstream end of the main catalyst

h11‧‧‧The path from the combustion chamber to the upstream oxygen detection member is long

h12‧‧‧The path length from the upstream oxygen detection member to the upstream end of the main catalyst

h13‧‧‧The path from the combustion chamber to the upstream oxygen detection component is long

h14‧‧‧The path length from the upstream oxygen detection member to the upstream end of the main catalyst

h15‧‧‧The path from the combustion chamber to the upstream oxygen detection component is long

h16‧‧‧The path length from the upstream oxygen detection member to the upstream end of the main catalyst

h17‧‧‧The path from the combustion chamber to the upstream oxygen detection member is long

h18‧‧‧The path length from the upstream oxygen detection member to the upstream end of the main catalyst

h21‧‧‧The path from the combustion chamber to the upstream oxygen detection component is long

h22‧‧‧ The path length from the upstream oxygen detection member to the upstream end of the main catalyst

L‧‧‧ Left

L1‧‧‧A straight line extending parallel to the vertical direction through the crankshaft line

L2, L4, L6, L8 ‧‧‧ a line orthogonal to the crankshaft line and cylinder axis

L3‧‧‧ a straight line extending parallel to the vertical direction through the crankshaft line

L5‧‧‧ A straight line extending parallel to the vertical direction through the crankshaft line

L7‧‧‧A straight line extending parallel to the vertical direction through the crankshaft line

R‧‧‧ right

After Re‧‧‧

V1‧‧‧Air inlet valve

V2‧‧‧ exhaust valve

V3‧‧‧Air inlet valve

V4‧‧‧ exhaust valve

V5‧‧‧Air inlet valve

V6‧‧‧ exhaust valve

V7‧‧‧Air inlet valve

V8‧‧‧ exhaust valve

w1‧‧‧Maximum width of the main catalyst in a direction perpendicular to the path direction

w2‧‧‧Maximum width of the main catalyst in a direction perpendicular to the path direction

w3‧‧‧Maximum width of the main catalyst in a direction perpendicular to the path direction

w4‧‧‧Maximum width of the main catalyst in a direction perpendicular to the path direction

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

FIG. 2 is a side view of a state in which a vehicle body shell and the like are removed from the locomotive of FIG. 1. FIG.

FIG. 3 is a bottom view of FIG. 2.

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

FIG. 5 is a schematic diagram showing an engine body and an exhaust system of the locomotive of FIG. 1. FIG.

Fig. 6 is a side view showing a state in which a car body shell and the like of a locomotive of a modification 1-1 of the first embodiment are removed.

FIG. 7 is a bottom view of FIG. 6.

FIG. 8 is a schematic diagram showing an engine body and an exhaust system of the locomotive of FIG. 6.

FIG. 9 is a side view of a state in which a car body shell and the like of a locomotive of Modification 1-2 of Embodiment 1 are removed.

FIG. 10 is a schematic diagram showing an engine body and an exhaust system of the locomotive of FIG. 9.

Fig. 11 is a side view of a locomotive according to a second embodiment of the present invention.

FIG. 12 is a bottom view of FIG. 11.

Fig. 13 is a side view showing a state in which a vehicle body shell and the like are removed from the locomotive of Fig. 11.

FIG. 14 is a bottom view of FIG. 13.

FIG. 15 is a schematic diagram showing an engine body and an exhaust system of the locomotive of FIG. 11. FIG.

FIG. 16 is a side view of a state in which a car body shell and the like of a locomotive of Modification 2-1 of Embodiment 2 is removed.

FIG. 17 is a bottom view of FIG. 16.

FIG. 18 is a schematic diagram showing an engine body and an exhaust system of the locomotive of FIG. 16.

Fig. 19 is a side view of a locomotive according to a third embodiment of the present invention.

FIG. 20 is a bottom view of FIG. 19.

Fig. 21 is a side view showing a state in which a vehicle body shell and the like are removed from the locomotive of Fig. 19;

FIG. 22 is a bottom view of FIG. 21.

Fig. 23 is a schematic diagram showing an engine body and an exhaust system of the locomotive of Fig. 19.

FIG. 24 is a side view showing a state in which a vehicle body shell and the like of a locomotive according to Modification 3-1 of Embodiment 3 is removed.

FIG. 25 is a bottom view of FIG. 24.

FIG. 26 is a schematic diagram showing an engine body and an exhaust system of the locomotive of FIG. 24.

Fig. 27 is a side view of a locomotive according to a fourth embodiment of the present invention.

FIG. 28 is a bottom view of FIG. 27.

FIG. 29 is a side view showing a state in which a vehicle body shell and the like are removed from the locomotive of FIG. 27.

FIG. 30 is a bottom view of FIG. 29.

FIG. 31 is a schematic diagram showing an engine body and an exhaust system of the locomotive of FIG. 27.

FIG. 32 is a side view showing a state in which a vehicle body shell and the like of a locomotive according to a modification 4-1 of the fourth embodiment is removed.

FIG. 33 is a bottom view of FIG. 32.

FIG. 34 is a schematic diagram showing an engine body and an exhaust system of the locomotive of FIG. 32.

Fig. 35 is a schematic diagram of the periphery of a muffler of a locomotive according to another embodiment of the present invention.

Fig. 36 is a sectional view of a muffler of a locomotive according to another embodiment of the present invention.

Fig. 37 is a sectional view of a muffler of a locomotive according to another embodiment of the present invention.

Fig. 38 is a sectional view of a muffler of a locomotive according to another embodiment of the present invention.

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

Fig. 40 is a schematic diagram of an engine body of a locomotive according to another embodiment of the present invention.

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

Fig. 42 is a partially enlarged view of 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 vehicle of the present invention is applied to a locomotive will be described. In the following description, front, back, left, and right respectively represent the front, back, left, and right of the rider of the motorcycle. Among them, the locomotive is arranged on a level ground. The symbols F, Re, L, and R attached to each drawing represent front, back, left, and right, respectively.

(Embodiment 1)

[Overall composition]

Fig. 1 is a side view of a locomotive according to a first embodiment of the present invention. Fig. 2 is a side view showing a state in which a car body shell and the like of the locomotive of the first embodiment are removed. Fig. 3 shows the locomotive of the first embodiment Bottom view of the body shell and other parts removed. 5 is a schematic diagram showing an engine and an exhaust system of a locomotive according to the first embodiment.

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

A rotatable steering shaft is inserted into the head pipe 3. A handle 7 (see FIG. 1) is provided above the steering shaft. A display device (not shown) is arranged near the handle 7. The display device displays vehicle speed, engine speed, various warnings, and the like.

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

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

As shown in FIG. 2, an engine body 20 is disposed below the main frame 4. The engine body 20 is supported by the vehicle body frame 2. Specifically, the upper portion of the engine body 20 is fixed to a bracket 4a provided on the main frame 4 by a bolt 4b. More specifically, the engine body 20 is fixed to the bracket 4a above the crankcase portion 21 and the front portion described later. The rear portion of the engine body 20 is also fixed to another bracket provided on the vehicle body frame 2. An air cleaner 32 is arranged 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 a vehicle body frame 2 and the like. The vehicle body casing 11 includes a main casing 16 and a front casing 17. The front case 17 is disposed in front of the head pipe 3. The main casing 16 is disposed behind the head pipe 3. The main casing 16 covers the main frame 4 and the seat rail 5. The main casing 16 and the front casing 17 cover the left and right sides of the front portion of the engine body 20. Front shell 17 cover The left and right sides of the air cleaner 32.

The portions of the main frame 4 and the body shell 11 between the seat portion 9 and the head pipe 3 become lower. As a result, when viewed from the left and right directions of the vehicle, the chassis-type locomotive 1 is formed with a recess 12 formed behind the head pipe 3 and before the seat portion 9 and above the main frame 4. With this recessed portion 12, the rider easily crosses the vehicle body.

The locomotive 1 includes 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 pipe 33, an exhaust pipe 34, a muffler 35, a main catalyst 39 (main catalyst for a single combustion chamber), and an upstream oxygen detection member 36 (single An upstream oxygen detection means for a combustion chamber) and a downstream oxygen detection means 37 (a downstream oxygen detection means for a single combustion chamber). The details will be described later. The main catalyst 39 is disposed in the exhaust pipe 34. The main catalyst 39 purifies the exhaust gas flowing through the exhaust pipe 34. The upstream oxygen detection member 36 is disposed upstream of the main catalyst 39 in the exhaust pipe 34. The downstream oxygen detection member 37 is disposed downstream of the main catalyst 39 in the exhaust pipe 34. The upstream oxygen detection means 36 and the downstream oxygen detection means 37 detect the amount of oxygen or 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 section 21 includes a crankcase body 23, a crankshaft 27 accommodated in the crankcase body 23, a transmission mechanism, and the like. Hereinafter, the center line Cr1 of the crankshaft 27 is referred to as a crankshaft line Cr1. The crank line Cr1 extends in the left-right direction. Lubricating oil is stored in the crankcase body 23. This oil is transported by an oil pump (not shown) and circulates in the engine body 20.

The cylinder section 22 includes 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 connected to the front portion of the crankcase body 23. The cylinder head 25 is connected to the front of the cylinder block 24. The head cover 26 is connected to the front of the cylinder head 25.

As shown in FIG. 5, a cylinder hole 24 a is formed in the cylinder block 24. A reciprocating piston 28 is housed in the cylinder hole 24a. The piston 28 is connected to the crankshaft 27 via a connecting rod. Following, will The center line Cy1 of the cylinder hole 24a is referred to as a cylinder axis Cy1. As shown in FIG. 2, the engine body 20 is arranged so that the cylinder axis Cy1 extends in the front-rear direction (horizontal direction). More specifically, the direction from the crankcase portion 21 toward the cylinder portion 22 from the cylinder axis Cy1 is forward and upward. The inclination angle of the cylinder axis Cy1 with respect to the horizontal direction is 0 degrees or more and 45 degrees or less.

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 hole 24 a of the cylinder block 24, the cylinder head 25 and the piston 28. That is, a part of the combustion chamber 29 is partitioned by the inner surface of the cylinder hole 24a. A front end of a spark plug (not shown) is arranged in the combustion chamber 29. The Mars plug ignites a mixture of fuel and air in the combustion chamber 29. As shown in FIG. 2, the combustion chamber 29 is located further forward than the crank line Cr1. This situation is replaced by the following expression. A straight line passing through the crankshaft line Cr1 and extending parallel to the vertical direction is defined as L1. When viewed from the left and right directions, the combustion chamber 29 is disposed in front of the straight line L1.

As shown in FIG. 5, a cylinder intake passage portion 30 and a cylinder exhaust passage portion 31 (a cylinder exhaust passage portion for a single combustion chamber) are formed in the cylinder head 25. In this specification, the "passage part" means a structure which 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 forming the combustion chamber 29. The cylinder intake passage portion 30 extends from the intake port 30 a to an intake port formed on the outer surface (upper surface) of the cylinder head 25. The cylinder exhaust passage portion 31 extends from the exhaust port 31 a 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 operated by a valve operating mechanism (not shown) that is linked to the crankshaft 27. The intake port 30a is opened and closed by the movement of the intake valve V1. The exhaust port 31a is opened and closed by the movement of the exhaust valve V2. An intake pipe 33 is connected to an end (suction port) of the cylinder intake passage portion 30. An exhaust pipe 34 is connected to an end portion (discharge port) of the cylinder exhaust passage portion 31. The path length of the cylinder exhaust passage portion 31 is set to a1.

An injector 48 (see FIG. 4) is disposed in the cylinder intake passage portion 30 or the intake pipe 33. spray The injector 48 is used to supply fuel to the combustion chamber 29. More specifically, the injector 48 injects fuel into the cylinder intake passage portion 30 or the intake pipe 33. The injector 48 may be arranged to inject fuel into the combustion chamber 29. A throttle valve (not shown) is disposed in the intake pipe 33.

As shown in FIG. 2, viewed from the left and right directions, the intake pipe 33 extends upward from the upper surface of the cylinder head 25. The intake pipe 33 is connected to the air cleaner 32. The air cleaner 32 purifies the air supplied to the engine body 20. The air purified by passing through the air cleaner 32 is supplied to the engine body 20 through the intake pipe 33.

The detailed structure of the exhaust system will be described later.

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

As shown in FIG. 4, the single-cylinder four-stroke engine unit 19 includes an engine speed sensor 46 a, a throttle opening sensor 46 b (throttle position sensor), an engine temperature sensor 46 c, and an intake pressure sensor. Sensor 46d and intake air temperature sensor 46e. The engine speed sensor 46a detects the speed of the crankshaft 27, that is, the engine speed. The throttle opening degree sensor 46b detects the position of a throttle valve (not shown), and detects the opening degree of the throttle valve (hereinafter referred to as the throttle valve opening degree). The engine temperature sensor 46c detects the temperature of the engine body. The intake pressure sensor 46d detects a pressure (intake pressure) in the intake pipe 33. The intake air temperature sensor 46e detects the temperature (intake air temperature) of the air in the intake pipe 33.

The single-cylinder four-stroke engine unit 19 includes an electronic control unit (ECU: Electronic Control Unit) 45 that controls the engine body 20. The electronic control unit 45 corresponds to the control device of the present invention. The electronic control unit 45 is connected to an engine speed sensor 46a, an engine temperature sensor 46c, a throttle opening sensor 46b, an intake pressure sensor 46d, an intake temperature sensor 46e, a vehicle speed sensor, etc. Various sensor connections. The electronic control unit 45 is connected to an ignition induction coil 47, an injector 48, a fuel pump 49, a display device (not shown), and the like. The electronic control unit 45 includes a control unit 45a and an operation instruction unit 45b. The operation instruction portion 45b includes ignition The drive circuit 45c, the injector drive circuit 45d, and the 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 to drive the ignition induction coil 47, the injector 48, and the fuel pump 49, respectively. When the ignition induction coil 47 is driven, a spark discharge is generated by the spark plug to ignite the mixed gas. 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 pressure-fed 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 a signal from the upstream oxygen detection member 36, a signal from the engine speed sensor 46a, and the like. The control unit 45a controls the timing of 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 better air-fuel ratio of the mixed gas in the combustion chamber 29 is the theoretical air-fuel ratio (stoichiometry). The control unit 45a increases or decreases the fuel injection amount as necessary.

An example of the control of the fuel injection amount by the control unit 45a will be described below.

The control unit 45a first calculates a basic fuel injection amount based on signals from the engine speed sensor 46a, the throttle opening sensor 46b, the engine temperature sensor 46c, and the intake pressure sensor 46d. Specifically, a map of intake air volume related to throttle opening and engine speed and a map of intake air volume related to intake pressure and engine speed are used to determine the intake air volume. Then, based on the intake air amount obtained from the self-mapping table, a basic fuel injection amount capable of achieving the target air-fuel ratio is determined. When the throttle opening is small, a mapping table for intake air pressure and engine speed in relation to the intake air volume is used. On the other hand, when the opening degree of the throttle valve is large, a mapping table for the amount of intake air related to the opening degree of the throttle valve and the engine speed is used.

In addition, the control unit 45a calculates a feedback correction value for correcting the basic fuel injection amount based on the signal from the upstream oxygen detection means 36. Specifically, first, based on the upstream oxygen detection member 36 Signal to determine whether the mixed gas is lean air-fuel ratio or rich air-fuel ratio. In addition, the so-called rich air-fuel ratio refers to a state where there is excess fuel relative to the theoretical air-fuel ratio. The so-called lean air-fuel ratio refers to a state where there is excess air relative to the theoretical air-fuel ratio. When the control unit 45a determines that the mixture is a lean air-fuel ratio determination, it calculates a feedback correction value so that the next fuel injection amount increases. On the other hand, if the control unit 45a determines that the mixed gas is rich in air-fuel ratio, it determines the feedback correction value so that the next fuel injection amount decreases.

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

The control unit 45a calculates the fuel injection amount based on correction values such as the basic fuel injection amount and the feedback correction value. Based on the fuel injection amount obtained in this manner, the fuel pump 49 and the injector 48 are driven. In this way, the electronic control unit 45 (control device) processes the signal of the upstream oxygen detection member 36. The electronic control unit 45 (control device) performs combustion control based on a signal from the upstream oxygen detecting means 36.

The electronic control unit 45 (control device) processes the signal of the downstream oxygen detecting means 37. The electronic control unit 45 (control device) determines the purification ability of the main catalyst 39 based on the signal of the downstream oxygen detecting member 37. Hereinafter, an example of a specific method for determining the purification ability of the main catalyst 39 based on a signal from the downstream oxygen detecting means 37 will be described.

First, the fuel injection amount is controlled such that the mixed gas becomes the rich air-fuel ratio and the lean air-fuel ratio repeatedly over a certain period of time (a few seconds). Then, the delay of the change in the signal of the downstream oxygen detection member 37 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 37 is large, it is determined that the purification ability of the main catalyst 39 has been reduced from a specific level. In this case, a signal is sent from the electronic control unit 45 to the display device. Then, a warning lamp (not shown) of the display device is turned on. Thereby, the rider can be prompted to replace the main catalyst 39.

In this way, by using the downstream oxygen detecting member 37 disposed downstream of the main catalyst 39 The signal can determine the purification ability of the main catalyst 39. Therefore, the deterioration of the main catalyst 39 can be notified before the deterioration of the main catalyst 39 reaches a certain level to prompt the replacement of the main catalyst 39. Thereby, the initial performance of the locomotive 1 with respect to exhaust gas purification can be maintained for a longer time by using a plurality of main catalysts.

[Composition of the exhaust system]

The exhaust system of the locomotive 1 according to the first embodiment will be described below. In the description of the exhaust system in this specification, the so-called upstream refers to the upstream of the exhaust gas flowing direction. The term "downstream" means downstream of the direction in which the exhaust gas flows. In the description of the exhaust system in this specification, the direction of the path means the direction of flow 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, the upstream oxygen detection member 36, and the downstream oxygen detection member 37. The muffler 35 has a release port facing the atmosphere. The path from the combustion chamber 29 to the release port 35e is referred to as an exhaust path 41 (see FIG. 5). The exhaust path 41 is formed by a cylinder exhaust passage portion 31, an exhaust pipe 34, and a muffler 35. The exhaust path 41 is a space through which exhaust gas passes.

As shown in FIG. 5, the upstream end portion of the exhaust pipe 34 is connected to the cylinder exhaust passage portion 31. The downstream end of the exhaust pipe 34 is connected to the muffler 35. A catalyst unit 38 is provided in the middle of the exhaust pipe 34. An upstream exhaust pipe 34 a is a portion of the exhaust pipe 34 that is more upstream than the catalyst unit 38. A portion of the exhaust pipe 34 further downstream than the catalyst unit 38 is set as a downstream exhaust pipe 34b. In addition, in FIG. 5, the exhaust pipe 34 is drawn in a straight line for simplifying the description, but the exhaust pipe 34 is not a straight line.

As shown in FIG. 3, the exhaust pipe 34 is provided on the right side of the locomotive 1. As shown in FIG. 2, a part of the exhaust pipe 34 is located below the crank line Cr1. The exhaust pipe 34 has two curved portions. An upstream bent portion of the two bent portions is simply referred to as an upstream bent portion. The downstream bent portion of the two bent portions is simply referred to as a downstream bent portion. Viewed from the left and right directions, the upstream curved portion changes the direction of exhaust gas flow from a direction extending in the up and down direction to a direction extending in the front and back direction. More specifically, when viewed from the left and right directions, the curved portion changes the exhaust gas flow direction from downward to upward and backward. When viewed from left and right, the downstream bend makes the exhaust gas flow direction It changes from back to top and back. The portion slightly downstream from the downstream bent portion is located below the crank line Cr1. The main catalyst 39 is disposed between two curved 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 rhythmic wave of the exhaust gas. Thereby, the muffler 35 can reduce the volume of the sound (exhaust sound) generated by the exhaust gas. In the muffler 35, a plurality of expansion chambers and a plurality of pipes connecting the expansion chambers to each other are provided. The downstream end of the exhaust pipe 34 is arranged in the expansion chamber of the muffler 35. A discharge port 35e facing the atmosphere is provided at the downstream end of the muffler 35. As shown in FIG. 5, the path length of the exhaust path from the downstream end of the exhaust pipe 34 to the release port 35e is set to e1. In addition, the path length of the expansion chamber in the muffler 35 is the length of the path that connects the center of the inlet of the expansion chamber to the center of the outlet of the expansion chamber as the shortest. The exhaust gas passing through the muffler 35 is released to the atmosphere from the self-release outlet 35e. As shown in FIG. 2, the release port 35e is located further behind the crank line Cr1.

The main catalyst 39 is disposed in the exhaust pipe 34. The upstream end of the main catalyst 39 is disposed further upstream than the upstream end 35 a of the muffler 35. The catalyst unit 38 includes a cylindrical case 40 and a main catalyst 39. The upstream end of the casing 40 is connected to the upstream exhaust pipe 34a. The downstream end of the casing 40 is connected to the downstream exhaust pipe 34b. The casing 40 constitutes a part of the exhaust pipe 34. The main catalyst 39 is fixed inside the casing 40. The exhaust gas is purified by passing through the main catalyst 39. All the exhaust gas discharged from the exhaust port 31 a of the combustion chamber 29 passes through the main catalyst 39. The main catalyst 39 purifies the exhaust gas discharged from the combustion chamber 29 to the maximum extent in the exhaust path 41.

The main catalyst 39 is a so-called three-way catalyst. The so-called three-way catalyst is removed by oxidizing or reducing three kinds of substances contained in the exhaust gas, such as hydrocarbons, carbon monoxide, and nitrogen oxides. Three-way catalyst is a kind of redox catalyst. The main catalyst 39 includes a substrate and a catalyst substance attached to the surface of the substrate. The catalyst substance has a support and a noble metal. The carrier is provided between the precious metal and the substrate. The carrier carries a precious metal. This precious metal purifies the exhaust gas. Examples of the noble metal include hydrocarbons, carbon monoxide, and nitrogen oxides, respectively. Platinum, palladium, rhodium, etc.

The main catalyst 39 has a porous structure. The porous structure refers to a structure in which a porous structure is formed in a cross section perpendicular to the path direction of the exhaust path 41. An example of a porous structure is a honeycomb structure. A plurality of holes are formed in the main catalyst 39 with a sufficiently small width compared to 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 refers to a catalyst made of a metal substrate. The ceramic substrate catalyst refers to a ceramic substrate. The base material of the metal base catalyst is formed by, for example, alternately winding a wave plate made of metal and a flat plate made of metal. The substrate of the ceramic substrate catalyst is, for example, a honeycomb structure.

As shown in FIG. 5, the length in the path direction of the main catalyst 39 is c1. The maximum width of the main catalyst 39 in a 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 be a shape whose length in the left-right direction is longer than that in the vertical direction.

As shown in FIG. 5, the case 40 includes a catalyst arrangement passage portion 40 b, an upstream passage portion 40 a, and a downstream passage portion 40 c. A main catalyst 39 is arranged in the catalyst arrangement passage portion 40b. In the path direction, the upstream end and the downstream end of the catalyst arrangement passage portion 40b are at the same positions as the upstream end and the downstream end of the main catalyst 39, respectively. The area of a 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 tapered portion has a larger inner diameter toward the downstream. At least a part of the downstream passage portion 40c is formed in a tapered shape. The tapered portion has a smaller inner diameter toward the downstream. The area of the cross section orthogonal to the path direction of the catalyst arrangement passage portion 40b is set to S1. A section orthogonal to the path direction of at least a part of the upstream passage portion 40a The area of the face is smaller than the area S1. Here, at least a part of the upstream passage portion 40a includes an upstream end of the upstream passage portion 40a. The area of at least a portion of the downstream passage portion 40c that is orthogonal to the path direction is smaller than the area S1. Here, at least a part of the downstream passage portion 40c includes a downstream end of the downstream passage portion 40c.

As shown in FIG. 2 and FIG. 3, the main catalyst 39 is disposed more forward than the crank line Cr1. That is, when viewed from the left and right directions, the main catalyst 39 is arranged in front of the straight line L1. As described above, the straight line L1 is a straight line extending parallel to the vertical direction through the crankshaft line Cr1. When viewed from the left and right directions, the main catalyst 39 is positioned in front of (below) the cylinder axis Cy1.

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

As shown in FIG. 5, the path length from the upstream end of the exhaust pipe 34 to the upstream end of the main catalyst 39 is set to b1. The path length b1 is the path length of the passage portion including the upstream exhaust pipe 34 a and the upstream passage portion 40 a of the catalyst unit 38. In other words, the path length b1 is a path length from the downstream end of the cylinder exhaust passage portion 31 to the upstream end of the main catalyst 39. The path length from the downstream end of the autonomous catalyst 39 to the downstream end of the exhaust pipe 34 is d1. The path length d1 is a path length including the downstream passage portion 40c of the catalyst unit 38 and the passage portion of 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. The path length from the downstream end of the autonomous catalyst 39 to the release outlet 35e is d1 + e1.

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

The upstream oxygen detection member 36 is arranged in the exhaust pipe 34. The upstream oxygen detection member 36 is disposed further upstream than the main catalyst 39. The upstream oxygen detection member 36 is arranged in the upstream exhaust pipe 34a (see FIG. 5). The upstream oxygen detecting means 36 is a sensor that detects the oxygen concentration contained in the exhaust gas. The upstream oxygen detecting member 36 may also be an oxygen sensor that detects whether the oxygen concentration is higher or lower than a specific value. The upstream oxygen detection means 36 may output a plurality of stages or linearly express the oxygen concentration. Sensor (eg A / F sensor: Air Fuel ratio sensor). One end portion (detection portion) of the upstream oxygen detection member 36 is disposed inside the exhaust pipe 34, and the other end portion is disposed outside the exhaust pipe 34. The detection portion of the upstream oxygen detection member 36 can detect the oxygen concentration when heated to a high temperature and activated. The detection result of the upstream oxygen detection member 36 is output to the electronic control unit 45.

As shown in FIG. 5, the path length from the combustion chamber 29 to the upstream oxygen detection member 36 is set to h1. The path length from the upstream oxygen detection member 36 to the upstream end of the main catalyst 39 is set to h2. The upstream oxygen detecting member 36 is disposed at a position where the path length h1 is shorter than the path length h2.

The downstream oxygen detection member 37 is disposed in the exhaust pipe 34. The downstream oxygen detecting member 37 is disposed further downstream than the main catalyst 39. The downstream oxygen detection member 37 is disposed in the downstream exhaust pipe 34b (see FIG. 5). The downstream oxygen detection member 37 is disposed further upstream than the muffler 35. The downstream oxygen detecting means 37 is a sensor that detects the oxygen concentration contained in the exhaust gas. The downstream oxygen detecting member 37 may also be an oxygen sensor that detects whether the oxygen concentration is higher or lower than a specific value. In addition, the downstream oxygen detecting member 37 may be a sensor (for example, an A / F sensor: Air Fuel ratio sensor) that outputs a detection signal that expresses an oxygen concentration in a plurality of stages or linearly. One end portion (detection portion) of the downstream oxygen detection member 37 is disposed inside the exhaust pipe 34, and the other end portion is disposed outside the exhaust pipe 34. The detection result of the downstream oxygen detection member 37 is output to the electronic control unit 45.

The configuration of the locomotive 1 according to the first embodiment has been described above. The locomotive 1 according to the first embodiment has the following features.

At least a part of the combustion chamber 29 is disposed more forward than the crank line Cr1. The outlet 35e of the muffler 35 is disposed further behind the crank line Cr1. At least a part of the main catalyst 39 is disposed more forward than the crank line Cr1. The upstream end of the main catalyst 39 is disposed further upstream than the upstream end 35 a of the muffler 35. That is, the main catalyst 39 is disposed relatively close to the combustion chamber 29. Therefore, the exhaust gas purification performance of the main catalyst 39 can be improved.

The downstream oxygen detecting member 37 is disposed further downstream than the main catalyst 39. By the signal of the downstream oxygen detecting member 37, the deterioration of the main catalyst 39 can be detected. Therefore, the main catalyst The deterioration of the agent 39 is notified before the deterioration reaches a certain level, and the replacement of the main catalyst 39 is prompted. Thereby, a plurality of main catalysts 39 can be used to maintain the initial performance of the locomotive 1 with respect to exhaust gas purification for a longer time. In addition, the deterioration of the main catalyst 39 may be detected based on the signal of the downstream oxygen detection member 37 and the signal of the upstream oxygen detection member 36 disposed upstream of the main catalyst 39. By using the signals of the two oxygen detecting members 36 and 37, the degree of deterioration of the main catalyst 39 can be detected more accurately. Therefore, compared to a case where the degradation of the main catalyst 39 is detected using only the signal of the downstream oxygen detection member 37, the initial performance of the locomotive 1 with respect to exhaust purification can be maintained, and one main catalyst 39 can be used for a longer time.

The actual purification capability of the main catalyst 39 can be detected by a signal disposed on the upstream oxygen detection member 36 located upstream from the main catalyst 39 and a signal disposed on the downstream oxygen detection member 37 located downstream from the main catalyst 39. Therefore, in the case where the combustion control is performed based on the signals of the two oxygen detection members 36 and 37, the accuracy of the combustion control can be improved. Thereby, the progress of deterioration of the main catalyst 39 can be slowed. Therefore, the initial performance of the locomotive 1 with respect to exhaust gas purification can be maintained for a longer time.

In this way, the initial performance of the locomotive 1 with respect to exhaust gas purification can be maintained for a longer time without increasing the size of the main catalyst 39. Thereby, the support structure can be simplified, and the initial performance of the locomotive 1 with respect to exhaust gas purification can be maintained for a long time.

According to the above, the locomotive 1 provided with the single-cylinder four-stroke engine unit 19 of this embodiment can simplify the supporting structure and improve the exhaust purification performance of the catalyst, and maintain the initial performance of the locomotive 1 with respect to the exhaust purification for a long time.

At least a part of the main catalyst 39 is disposed more forward than the crank line Cr1. Therefore, the main catalyst 39 is disposed closer to the combustion chamber 29. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

The straight line L2 is a straight line orthogonal to the cylinder axis Cy1 and orthogonal to the crankshaft line Cr1. This straight line L2 extends downward from the crankshaft 27. When viewed from left and right, at least a part of the main catalyst 39 is located in front of the straight line L2. Therefore, the main catalyst 39 is disposed closer to the combustion chamber 29 position. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

The path length (a1 + b1) from one combustion chamber 29 to the upstream end of the main catalyst 39 is shorter than the path length (d1 + e1) from the downstream end of the autonomous catalyst 39 to the release outlet 35e. Therefore, the main catalyst 39 can be disposed closer to the combustion chamber 29. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

The path length (a1 + b1) from one combustion chamber 29 to the upstream end of the main catalyst 39 is shorter than the path length (d1) of the downstream end of the autonomous catalyst 39 to the downstream end of the exhaust pipe 34. Therefore, the main catalyst 39 can be disposed closer to the combustion chamber 29. Therefore, the exhaust gas purification performance of the main catalyst 39 can be further improved.

The path length (h1) from one combustion chamber 29 to the upstream end of the upstream oxygen detection member 36 is shorter than the path length (h2) from the upstream oxygen detection member 36 to the upstream end of the main catalyst 39. Therefore, the upstream oxygen detecting means is disposed closer to the combustion chamber 29. Therefore, when the engine is started, the upstream oxygen detection member 36 can be heated up to the activation temperature more quickly. Therefore, the detection accuracy of the upstream oxygen detection member 36 can be improved. Thereby, the combustion control based on the signal of the upstream oxygen detection member 36 can be performed more accurately. As a result, the exhaust gas purification performance of the main catalyst 39 can be further improved. In addition, by improving the accuracy of the combustion control, the progress of the deterioration of the main catalyst 39 can be slowed down. Therefore, the initial performance of the locomotive 1 with respect to exhaust gas purification can be maintained for a longer time.

The area of at least a part of the upstream passage portion 40a in a cross section orthogonal to the flow direction of the exhaust gas is smaller than the area S1. The area S1 is an area of a cross section orthogonal to the exhaust gas flow direction of the catalyst arrangement passage portion 40b. Therefore, as the main catalyst 39, a catalyst having a large cross-sectional area can be used. Therefore, the exhaust gas purification performance of the main catalyst 39 can be improved.

(Modification 1-1 of Embodiment 1)

Fig. 6 is a side view showing a state in which a car body shell and the like of a locomotive of a modification 1-1 of the first embodiment are removed. FIG. 7 is a bottom view of a state in which a vehicle body shell and the like of a locomotive according to a modification 1-1 of the first embodiment is removed. Fig. 8 is a diagram showing an engine body and a row of a modified example 1-1 of the first embodiment;

Diagram of air system. In Modified Example 1-1, the same components as those in Embodiment 1 are denoted by the same reference numerals, and detailed descriptions are omitted.

As shown in FIG. 6, in the modified example 1-1, the main catalyst 39 is arranged downstream compared with the first embodiment. The specific structure of the main catalyst 39 is the same as that of the first embodiment. The main catalyst 39 of the modification 1-1 is arranged in the exhaust pipe 234. As in the first embodiment, the upstream end of the main catalyst 39 is disposed further upstream than the upstream end 35 a of the muffler 35.

The exhaust pipe 234 is connected to the cylinder exhaust passage portion 31 (see FIG. 8) and the muffler 35 in the same manner as the exhaust pipe 34 of the first embodiment. A catalyst unit 38 is provided in the middle of the exhaust pipe 234. As shown in FIG. 8, a portion of the exhaust pipe 234 that is more upstream than the catalyst unit 38 is an upstream exhaust pipe 234 a. A portion of the exhaust pipe 234 further downstream than the catalyst unit 38 is set as a downstream exhaust pipe 234b. The downstream exhaust pipe 234 b is disposed inside the muffler 35. In addition, in FIG. 8, the exhaust pipe 234 is drawn in a straight line for simplifying the description.

As shown in FIG. 6, the main catalyst 39 is disposed further behind the crank line Cr1. That is, when viewed from the left and right directions, the main catalyst 39 is disposed behind the straight line L1. As described above, the straight line L1 is a straight line extending parallel to the vertical direction through the crankshaft line Cr1. When viewed from the left and right directions, the main catalyst 39 is positioned in front of (below) the cylinder axis Cy1.

As shown in FIG. 6, when viewed from the left and right directions, the main catalyst 39 is located in front of the straight line L2. The straight line L2 is a straight line orthogonal to the cylinder axis Cy1 and orthogonal to the crank line Cr1.

As shown in FIG. 8, the path length from the upstream end of the exhaust pipe 234 to the upstream end of the main catalyst 39 is b11. The path length from the downstream end of the autonomous catalyst 39 to the downstream end of the exhaust pipe 234 is set to d11. The path length from the combustion chamber 29 to the upstream end of the main catalyst 39 is a1 + b11. The path length from the downstream end of the autonomous catalyst 39 to the release outlet 35e is d11 + e1.

As in the first embodiment, the main catalyst 39 of the modified example 1-1 is arranged at a position where the path length a1 + b11 is shorter than the path length d11 + e1. In addition, unlike the first embodiment, the main catalyst 39 of the modification 1-1 is arranged at a path length a1 + b11 longer than a path length d11. Home. Furthermore, unlike the first embodiment, the main catalyst 39 of the modification 1-1 is arranged at a position where the path length b11 is longer than the path length d11.

The upstream oxygen detection member 36 is arranged in the exhaust pipe 234. The upstream oxygen detection member 36 is disposed further upstream than the main catalyst 39. The upstream oxygen detection member 36 is arranged in the upstream exhaust pipe 234a (see FIG. 8).

As shown in FIG. 8, the path length from the combustion chamber 29 to the upstream oxygen detection member 36 is set to h11. The path length from the upstream oxygen detection member 36 to the upstream end of the main catalyst 39 is set to h12. As in the first embodiment, the upstream oxygen detecting means 36 is arranged at a position where the path length h11 is shorter than the path length h12.

The downstream oxygen detection member 37 is disposed in the exhaust pipe 234. The downstream oxygen detecting member 37 is disposed further downstream than the main catalyst 39. The downstream oxygen detection member 37 is arranged in the downstream exhaust pipe 234a (see FIG. 8). The downstream oxygen detecting member 37 penetrates a side wall portion of the muffler 35. One end portion (detection portion) of the downstream oxygen detection member 37 is disposed in the downstream exhaust pipe 234a. The other end portion of the downstream oxygen detecting member 37 is disposed outside the muffler 35.

In Modified Example 1-1, the same configuration as the above-mentioned first embodiment achieves the effects described in the first embodiment.

(Modification 1-2 of Embodiment 1)

Fig. 9 is a side view of a locomotive according to a modification 1-2 of the first embodiment. FIG. 10 is a schematic diagram showing an engine body and an exhaust system according to Modification 1-2 of Embodiment 1. FIG. In Modification 1-2, the same components as those in Embodiment 1 are denoted by the same reference numerals, and detailed descriptions are omitted.

As shown in FIGS. 9 and 10, the upstream sub-catalyst 300 (upstream sub-catalyst for a single combustion chamber), the main catalyst 39, the upstream oxygen detection member 36, and the downstream oxygen detection member 37 are arranged in the exhaust pipe 334. The exhaust pipe 334 is connected to the cylinder exhaust passage portion 31 (see FIG. 10) and the muffler 35 in the same manner as the exhaust pipe 34 of the first embodiment. A catalyst unit 38 is provided in the middle of the exhaust pipe 334. As shown in FIG. 10, the exhaust pipe 334 is positioned further upstream than the catalyst unit 38. A part is set as the upstream exhaust pipe 334a. A portion of the exhaust pipe 334 further downstream than the catalyst unit 38 is a downstream exhaust pipe 334b. In addition, in FIG. 10, the exhaust pipe 334 is drawn in a straight line for simplifying the description, but the exhaust pipe 334 is not a straight line.

The upstream sub-catalyst 300 is provided further upstream than the main catalyst 39. The upstream sub-catalyst 300 is provided in the upstream exhaust pipe 334a (exhaust pipe 334). The upstream sub-catalyst 300 may include only a catalyst substance attached to the inner wall of the exhaust pipe 334. In this case, the base material to which the catalyst substance of the upstream sub-catalyst 300 is attached is the inner wall of the exhaust pipe 334. The upstream sub-catalyst 300 may include a base material disposed inside the exhaust pipe 334. In this case, the upstream sub-catalyst 300 includes a substrate and a catalyst substance. The base material of the upstream sub-catalyst 300 is, for example, a plate. The shape of the cross section orthogonal to the path direction of the plate-shaped substrate may be S-shaped, circular, or C-shaped. When the upstream sub-catalyst 300 has a base material or when it does not have a base material, the upstream sub-catalyst 300 does not have a porous structure. Therefore, compared with the main catalyst 39, the reflection effect of the pressure rhythm caused by the exhaust gas generated by the upstream sub-catalyst 300 is smaller. Moreover, compared with the main catalyst 39, the upstream sub-catalyst 200 has less resistance to the exhaust gas flow.

The main catalyst 39 purifies the exhaust gas discharged from the combustion chamber 29 to the greatest extent in the exhaust path 41. That is, the purification ability of the main catalyst 39 in the exhaust path 41 for the exhaust gas discharged from the combustion chamber 29 is higher than that of the upstream sub-catalyst 300. In other words, compared to the main catalyst 39, the exhaust gas purification contribution of the upstream sub-catalyst 300 is lower.

The purification contribution of each of the main catalyst 39 and the upstream sub-catalyst 300 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 300 is referred to as a pre-catalyst, and the catalyst disposed downstream is referred to as a post-catalyst. In Variation 1-2, the upstream sub-catalyst 300 is a front catalyst, and the main catalyst 39 is a rear catalyst.

The engine unit of the modification example 1 was operated, and the concentration of harmful substances contained in the exhaust gas discharged from the self-release outlet 35e was measured in the warm-up state. Exhaust gas is measured in accordance with European regulations 定 方法。 Method. In the preheating state, the main catalyst 39 and the upstream sub-catalyst 200 become hot and become activated. Therefore, the main catalyst 39 and the upstream sub-catalyst 200 can fully exhibit purification performance in the warm-up state.

Secondly, the catalyst after the engine unit used in the test was removed, and only the base material of the rear catalyst was arranged instead. The engine unit in this state is referred to as a measurement engine unit A. In addition, the concentration of harmful substances contained in the exhaust gas discharged from the self-release outlet 35e was also measured in the preheated state.

In addition, the catalyst before the measurement engine unit A was removed, and only the base material of the front catalyst was disposed instead. The engine unit in this state is referred to as a measurement engine unit B. In the same manner, the concentration of harmful substances contained in the exhaust gas discharged from the self-release outlet 35e is measured in the preheated state. When the upstream sub-catalyst 200 (front catalyst) has a configuration in which a catalyst substance is directly attached to the inner wall of the exhaust pipe 234, the exhaust pipe 234 corresponds to a base material. The so-called replacement of the upstream sub-catalyst 200 and the arrangement of only the substrate of the upstream sub-catalyst 200 means that no catalyst substance is attached to the inner wall of the exhaust pipe 234.

The measurement engine unit A has a front catalyst and does not have a rear catalyst. The measurement engine unit B does not include a front catalyst and a rear catalyst. Therefore, based on the difference between the measurement result of the measurement engine unit A and the measurement result of the measurement engine unit B, the purification contribution degree of the front catalyst (upstream sub-catalyst 300) is calculated. Further, based on the difference between the measurement result of the measurement engine unit A and the measurement result of the engine unit of the modified example 1-2, the purification contribution degree of the post-catalyst (main catalyst 39) was calculated.

The purification ability of the upstream sub-catalyst 200 may be smaller than the purification ability of the main catalyst 39, or may be greater than the purification ability of the main catalyst 39. The purification capacity of the upstream sub-catalyst 200 is smaller than that 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 that of the exhaust gas when only the main catalyst 39 is provided.

As shown in FIG. 9, the main catalyst 39 is disposed more forward than the crank line Cr1. When viewed from the left and right directions, the main catalyst 39 is located in front of the straight line L2. Moreover, the straight line L2 The definition is the same as in the first embodiment. That is, the straight line L2 is a straight line orthogonal to the cylinder axis Cy1 and orthogonal to the crank line Cr1.

As shown in FIG. 10, the path length from the upstream end of the exhaust pipe 334 to the upstream end of the main catalyst 39 is set to b21. The path length from the downstream end of the autonomous catalyst 39 to the downstream end of the exhaust pipe 334 is set to d21. The path length from the combustion chamber 29 to the upstream end of the main catalyst 39 is a1 + b21. The path length from the downstream end of the autonomous catalyst 39 to the release outlet 35e is d21 + e1.

As in Embodiment 1, the main catalyst 39 is arranged at a position where the path length a1 + b21 is shorter than the path length d21 + e1. In addition, as in the first embodiment, the main catalyst 39 is arranged at a position where the path length a1 + b21 is shorter than the path length d21. Furthermore, as in Embodiment 1, the main catalyst 39 is arranged at a position where the path length b21 is shorter than the path length d21.

The upstream oxygen detection member 36 is arranged in the exhaust pipe 334. The upstream oxygen detection member 36 is disposed further upstream than the upstream sub-catalyst 300. The upstream oxygen detection member 36 is disposed in the upstream exhaust pipe 334a (see FIG. 13).

The path length from the combustion chamber 29 to the upstream oxygen detection member 36 is set to h21. The path length from the upstream oxygen detection member 36 to the upstream end of the main catalyst 39 is h22. As in the first embodiment, the upstream oxygen detecting means 36 is arranged at a position where the path length h21 is shorter than the path length h22.

The downstream oxygen detection member 37 is arranged in the exhaust pipe 334. The downstream oxygen detecting member 37 is disposed further downstream than the main catalyst 39. The downstream oxygen detection member 37 is disposed in the downstream exhaust pipe 334b (see FIG. 13). The downstream oxygen detection member 37 is disposed further upstream than the muffler 35.

In the modification 1-2, the same configuration as the above-mentioned first embodiment achieves the effects described in the first embodiment.

Further, in Modification 1-2, an upstream sub-catalyst 300 is provided upstream of the main catalyst 39. The deterioration of the upstream sub-catalyst 300 progresses faster than the main catalyst 39. However, even if the degradation of the upstream sub-catalyst 300 reaches a certain level, the purification performance of the exhaust gas can be maintained by the main catalyst 39. Therefore, the initial performance of the locomotive with respect to exhaust purification can be maintained more For a long time.

The upstream oxygen detection member 36 is disposed further upstream than the upstream sub-catalyst 300. Therefore, the upstream oxygen detection member 36 can detect the oxygen concentration of the exhaust gas flowing into the upstream sub-catalyst 300. Therefore, by performing the combustion control based on the signal of the upstream oxygen detection member 36, the exhaust gas purification performance of the upstream sub-catalyst 300 can be improved.

(Embodiment 2)

Fig. 11 is a side view of a locomotive according to a second embodiment of the present invention. Fig. 12 is a bottom view of a locomotive according to the second embodiment. Fig. 13 is a side view showing a state in which a car body shell and the like of the locomotive of the second embodiment are removed. Fig. 14 is a bottom view showing a state in which a car body shell and the like of the locomotive of the second embodiment are removed. 15 is a schematic diagram showing an engine and an exhaust system of a locomotive according to the second embodiment.

The vehicle of the second embodiment is a so-called street-type locomotive 50. As shown in FIG. 13, the locomotive 50 includes a vehicle body frame 53. The vehicle body frame 53 includes a head pipe 53a, an upper main frame 53b, a lower main frame 53c, and a seat portion frame 53d. The upper main frame 53b extends downward from the head pipe 53a, and then bends downward and extends downward. The lower main frame 53c is located below the upper main frame 53b. The lower main frame 53c extends rearward and downward from the head pipe 53a. The seat portion frame 53d extends rearward from a midway portion of the upper main frame 53b.

A freely rotatable steering shaft is inserted into the head pipe 53a. A handle 55 is provided above the steering shaft. A display device (not shown) is arranged near the handle 55. The display device displays vehicle speed, engine speed, various warnings, and the like.

The upper and lower ends of the steering shaft are connected to a pair of left and right front forks 56 via a bracket. A front wheel 57 is supported at the lower end of the front fork 56 for free rotation.

A front end portion of a pair of left and right rear arms 58 swinging freely is supported at the rear portion of the vehicle body frame 53. A rear wheel 59 is supported at the rear end of the rear arm 58 for free rotation.

A fuel tank 51 is supported on the upper main frame 53b (see FIG. 11). The seat portion frame 53d supports a seat portion 52 (see FIG. 11). An engine body 61 is supported on the vehicle body frame 53. An air cleaner 73 is supported on the vehicle body frame 53 (see FIG. 13). As shown in Figure 13, viewed from left and right It is observed that the upper part of the engine body 61 is arranged between the upper main frame 53b and the lower main frame 53c. The air cleaner 73 is disposed behind the engine body 61.

As shown in FIG. 11, the locomotive 50 includes a vehicle body casing 54 that covers a vehicle body frame 53 and the like. The vehicle body casing 54 covers the upper portion of the engine body 61 and the air cleaner 73.

The locomotive 50 has a single-cylinder four-stroke engine unit 60. The single-cylinder four-stroke engine unit 60 includes an engine body 61, an air cleaner 73 (see FIG. 13), an intake pipe 74, an exhaust pipe 75, a muffler 76, a main catalyst 180 (a main catalyst for a single combustion chamber), and upstream oxygen. Detection means 77 (upstream oxygen detection means for single combustion chamber), and downstream oxygen detection means 78 (downstream oxygen detection means for single combustion chamber). The single-cylinder four-stroke engine unit 60 includes the same electronic control unit as the electronic control unit 45 of the first embodiment. The electronic control unit controls the engine body 61.

The engine body 61 is a single-cylinder four-stroke engine. As shown in FIG. 13, the engine body 61 includes a crankcase portion 62 and a cylinder portion 63. The cylinder portion 63 extends forward and upward from the crankcase portion 62.

The crankcase portion 62 includes a crankcase body 64, a crankshaft 68 housed in the crankcase body 64, a transmission mechanism, and the like. A center line (crank line) Cr2 of the crankshaft 68 extends in the left-right direction. Lubricating oil is stored in the crankcase body 64. This oil is transported by an oil pump (not shown) and circulates in the engine body 61.

The cylinder portion 63 includes a cylinder block 65, a cylinder head 66, a head cover 67, and components housed therein. As shown in FIG. 13, the cylinder block 65 is connected to the upper portion of the crankcase body 64. The cylinder head 66 is connected to an upper portion of the cylinder block 65. The head cover 67 is connected to the upper part of the cylinder head 66.

As shown in FIG. 15, a cylinder hole 65 a is formed in the cylinder block 65. A piston 69 that can reciprocate is housed in the cylinder hole 65a. The piston 69 is connected to the crankshaft 68 via a connecting rod. Hereinafter, the center line Cy2 of the cylinder hole 65a is referred to as a cylinder axis Cy2. As shown in FIG. 13, the engine body 61 is arranged so that the cylinder axis Cy2 extends in the vertical direction. In more detail, since The direction of the crankcase portion 62 of the cylinder axis Cy2 toward the cylinder portion 63 is forward and upward. The inclination angle of the cylinder axis Cy2 with respect to the horizontal direction is 45 degrees or more and 90 degrees or less.

As shown in FIG. 15, a combustion chamber 70 is formed inside the cylinder portion 63. The combustion chamber 70 is formed by an inner surface of a cylinder hole 65 a of a cylinder block 65, a cylinder head 66, and a piston 69. As shown in FIG. 13, the combustion chamber 70 is located further forward than the crank line Cr2. This situation is replaced by the following expression. A straight line passing through the crankshaft line Cr2 and extending parallel to the vertical direction is defined as L3. When viewed from the left and right directions, the combustion chamber 70 is disposed in front of the straight line L3.

As shown in FIG. 15, a cylinder intake passage 71 and a cylinder exhaust passage 72 (a cylinder exhaust passage for a single combustion chamber) are formed in the cylinder head 66. In the cylinder head 66, an intake port 71 a and an exhaust port 72 a are formed in a wall portion forming the combustion chamber 70. The cylinder intake passage portion 71 extends from the intake port 71 a to an intake port formed on an outer surface (rear surface) of the cylinder head 66. The cylinder exhaust passage portion 72 extends from the exhaust port 72 a to a discharge port formed on the outer surface (front surface) of the cylinder head 66. The air supplied to the combustion chamber 70 passes through the cylinder intake passage portion 71. The exhaust gas discharged from the combustion chamber 70 passes through the cylinder exhaust passage portion 72.

An intake valve V3 is disposed in the cylinder intake passage portion 71. An exhaust valve V4 is disposed in the cylinder exhaust passage portion 72. The intake port 71a is opened and closed by the movement of the intake valve V3. The exhaust port 72a is opened and closed by the movement of the exhaust valve V4. An intake pipe 74 is connected to an end (suction port) of the cylinder intake passage portion 71. An exhaust pipe 75 is connected to an end portion (discharge port) of the cylinder exhaust passage portion 72. The path length of the cylinder exhaust passage portion 72 is set to a2.

The single-cylinder four-stroke engine unit 60 includes a spark plug, a valve operating mechanism, an injector, and a throttle valve in the same manner as the engine body 20 of the first embodiment. The single-cylinder four-stroke engine unit 60 includes various sensors such as an engine speed sensor and a throttle opening sensor, as in the first embodiment.

As described above, the single-cylinder four-stroke engine unit 60 includes the engine body 61, the exhaust pipe 75, the muffler 76, the main catalyst 180, the upstream oxygen detection member 77, and the downstream oxygen detection member 78. The muffler 76 has a vent 76e facing the atmosphere. Pass combustion chamber 70 to release port 76e The path is referred to as an exhaust path 182 (see FIG. 15). The exhaust path 182 is formed by a cylinder exhaust passage portion 72, an exhaust pipe 75, and a muffler 76. The exhaust path 182 is a space through which exhaust gas passes.

As shown in FIG. 15, the upstream end portion of the exhaust pipe 75 is connected to the cylinder exhaust passage portion 72. The downstream end of the exhaust pipe 75 is connected to a muffler 76. A catalyst unit 79 is provided in the middle of the exhaust pipe 75. A part of the exhaust pipe 75 which is more upstream than the catalyst unit 79 is an upstream exhaust pipe 75a. A portion of the exhaust pipe 75 further downstream than the catalyst unit 79 is set as a downstream exhaust pipe 75b. In addition, in FIG. 15, the exhaust pipe 75 is drawn in a straight line to simplify the description, but the exhaust pipe 75 is not a straight line.

As shown in FIGS. 12 and 14, most of the exhaust pipe 75 is provided on the right side of the locomotive 50. As shown in FIG. 13, a part of the exhaust pipe 75 is located below the crank line Cr2. The exhaust pipe 75 has two curved portions. The upstream bend among the two bends is simply referred to as an upstream bend. A downstream bent portion of the two bent portions is simply referred to as a downstream bent portion. Viewed from the left and right directions, the upstream bend changes the direction of exhaust gas flow from a direction extending in the front-rear direction to a direction extending in the up-down direction. More specifically, when viewed from the left and right directions, the upstream curved portion changes the flow direction of the exhaust gas from front to bottom to rear to bottom. Viewed from the left and right directions, the downstream bent portion changes the direction of exhaust gas flow from a direction extending in the up and down direction to a direction extending in the front and back direction. More specifically, when viewed from the left and right directions, the downstream curved portion changes the exhaust gas flow direction from rearward to downward and rearward. A portion further downstream than the downstream bent portion is located below the crank line Cr2. The main catalyst 180 is disposed between the two bent portions.

The muffler 76 flows into the exhaust gas discharged from the downstream end of the exhaust pipe 75. The muffler 76 is connected to the exhaust pipe 75. The muffler 76 is configured so as to suppress the rhythmic wave of the exhaust gas. Thereby, the muffler 76 can reduce the volume of the sound (exhaust sound) generated by the exhaust gas. In the muffler 76, a plurality of expansion chambers and a plurality of pipes connecting the expansion chambers to each other are provided. A downstream end portion of the exhaust pipe 75 is disposed in an expansion chamber of the muffler 76. At the downstream end of the muffler 76, Gas release outlet 76e. As shown in FIG. 15, the path length of the exhaust path from the downstream end of the exhaust pipe 75 to the release port 76e is set to e2. After passing through the muffler 76, the exhaust gas release port 76e is released to the atmosphere. As shown in FIG. 13, the release port 76e is located further behind the crank line Cr2.

The main catalyst 180 is disposed in the exhaust pipe 75. The upstream end of the main catalyst 180 is disposed further upstream than the upstream end 76 a of the muffler 76. The catalyst unit 79 includes a cylindrical case 181 and a main catalyst 180. An upstream end of the case 181 is connected to an upstream exhaust pipe 75a. The downstream end of the case 181 is connected to a downstream exhaust pipe 75b. The casing 181 constitutes a part of the exhaust pipe 75. The main catalyst 180 is fixed inside the casing 181. The exhaust gas is purified by passing through the main catalyst 180. All the exhaust gas discharged from the exhaust port 72 a of the combustion chamber 70 passes through the main catalyst 180. The main catalyst 180 purifies the exhaust gas discharged from the combustion chamber 70 to the maximum extent in the exhaust path 182.

The material of the main catalyst 180 is the same as that of the main catalyst 39 of the first embodiment. The main catalyst 180 has a porous structure. The main catalyst 180 is formed with a plurality of holes that are sufficiently finer than the path width of the upstream exhaust pipe 75a. As shown in FIG. 15, the length in the path direction of the main catalyst 180 is c2. The maximum width of the main catalyst 180 in a direction perpendicular to the path direction is set to w2. The length c2 of the main catalyst 180 is longer than the maximum width w2 of the main catalyst 180.

As shown in FIG. 15, the case 181 includes a catalyst arrangement passage portion 181 b, an upstream passage portion 181 a, and a downstream passage portion 181 c. A main catalyst 180 is arranged in the catalyst arrangement passage portion 181b. In the path direction, the upstream end and the downstream end of the catalyst arrangement passage portion 181b are the same positions as the upstream end and the downstream end of the main catalyst 180, respectively. The area of the cross section orthogonal to the path direction of the catalyst arrangement passage portion 181b is substantially constant. The upstream passage portion 181a is connected to the upstream end of the catalyst arrangement passage portion 181b. The downstream passage portion 181c is connected to the upstream end of the catalyst arrangement passage portion 181b.

At least a part of the upstream passage portion 181a is formed in a tapered shape. The tapered portion has a larger inner diameter toward the downstream. At least a part of the downstream passage portion 181c is formed in a tapered shape. This cone is oriented The inner diameter becomes smaller downstream. The area of a cross section of the catalyst arrangement passage portion 181b orthogonal to the path direction is S2. The area of at least a portion of the upstream passage portion 181a orthogonal to the path direction is smaller than the area S2. Here, at least a part of the upstream passage portion 181a includes an upstream end of the upstream passage portion 181a. The area of at least a portion of the downstream passage portion 181c that is orthogonal to the path direction is smaller than the area S2. Here, at least a part of the downstream passage portion 181c includes a downstream end of the downstream passage portion 181c.

As shown in FIG. 13, the main catalyst 180 is disposed more forward than the crank line Cr2. That is, when viewed from the left and right directions, the main catalyst 180 is arranged in front of the straight line L3. As described above, the straight line L3 is a straight line extending parallel to the vertical direction through the crankshaft line Cr2. When viewed from the left and right directions, the main catalyst 180 is located in front of the cylinder axis Cy2.

As shown in FIG. 13, a straight line orthogonal to the cylinder axis Cy2 and orthogonal to the crank line Cr2 is defined as L4. Viewed from the left and right directions, the main catalyst 180 is located in front of the straight line L4.

As shown in FIG. 15, the path length from the upstream end of the exhaust pipe 75 to the upstream end of the main catalyst 180 is set to b2. The path length b2 is a path length of a passage portion including the upstream exhaust pipe 75a and the upstream passage portion 181a of the catalyst unit 79. In other words, the path length b2 is the path length from the downstream end of the cylinder exhaust passage portion 72 to the upstream end of the main catalyst 180. The path length from the downstream end of the autonomous catalyst 180 to the downstream end of the exhaust pipe 75 is d2. The path length d2 is a path length including the downstream passage portion 181c of the catalyst unit 79 and the passage portion of the downstream exhaust pipe 75b. The path from the combustion chamber 70 to the upstream end of the main catalyst 180 is a2 + b2. The path from the downstream end of the autonomous catalyst 180 to the release outlet 76e is d2 + e2.

As in the first embodiment, the main catalyst 180 is arranged at a position where the path length a2 + b2 is shorter than the path length d2 + e2. In addition, as in the first embodiment, the main catalyst 180 is disposed at a position where the path length a2 + b2 is shorter than the path length d2. Furthermore, as in the first embodiment, the main catalyst 180 is disposed at a position where the path length b2 is shorter than the path length d2.

The upstream oxygen detection member 77 is disposed on the exhaust pipe 75. The upstream oxygen detecting member 77 is disposed further upstream than the main catalyst 180. The upstream oxygen detecting member 77 is arranged in the upstream exhaust Tube 75a (see FIG. 15). The upstream oxygen detecting means 77 is a sensor that detects the oxygen concentration contained in the exhaust gas. The structure of the upstream oxygen detection member 77 is the same as that of the upstream oxygen detection member 37 of the first embodiment.

As shown in FIG. 15, the path length from the combustion chamber 70 to the upstream oxygen detection member 77 is set to h3. The path length from the upstream oxygen detection member 77 to the upstream end of the main catalyst 180 is set to h4. As in the first embodiment, the upstream oxygen detecting means 77 is arranged at a position where the path length h3 is shorter than the path length h4.

The downstream oxygen detection member 78 is disposed in the exhaust pipe 75. The downstream oxygen detecting member 78 is disposed further downstream than the main catalyst 180. The downstream oxygen detection member 78 is arranged in the downstream exhaust pipe 75b (see FIG. 15). The downstream oxygen detecting member 78 is disposed more upstream than the muffler 76. The downstream oxygen detecting member 78 is a sensor that detects the oxygen concentration contained in the exhaust gas. The structure of the downstream oxygen detection member 78 is the same as that of the upstream oxygen detection member 37 of the first embodiment.

As described above, the locomotive 50 according to the second embodiment includes an upstream oxygen detection member 77 and a downstream oxygen detection member 78 upstream and downstream of the main catalyst 180. Otherwise, it has the same arrangement relationship as the locomotive 1 of the first embodiment. Regarding the same arrangement relationship as the first embodiment, the same effects as those described in the first embodiment are achieved.

In addition, the locomotive 50 of the second embodiment can also apply the configuration of the exhaust system of the aforementioned modification 1-2. In this case, the same effect as that of Modification 1-2 is obtained.

(Modification 2-1 of Embodiment 2)

FIG. 16 is a side view of a state in which a car body shell and the like of a locomotive of Modification 2-1 of Embodiment 2 is removed. FIG. 17 is a bottom view of a state in which a vehicle body shell and the like of a locomotive according to a modified example 2-1 of the second embodiment is removed. 18 is a schematic diagram showing an engine body and an exhaust system according to a modification 2-1 of the second embodiment. In Modified Example 2-1, the same components as those in Embodiment 2 are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

As shown in FIG. 16, compared with the second embodiment, the main catalyst 180 of Modification 2-1 is disposed downstream. The specific structure of the main catalyst 180 is the same as that of the second embodiment. Variety The main catalyst 180 of Example 2-1 is disposed in an exhaust pipe 275. As in the second embodiment, the upstream end of the main catalyst 180 is disposed more upstream than the upstream end 76 a of the muffler 76.

The exhaust pipe 275 is connected to the cylinder exhaust passage portion 72 (see FIG. 18) and the muffler 76 in the same manner as the exhaust pipe 75 of the second embodiment. A catalyst unit 79 is provided in the middle of the exhaust pipe 275. As shown in FIG. 18, the exhaust pipe 275 is positioned upstream of the catalyst unit 79 as an upstream exhaust pipe 275a. A part of the exhaust pipe 275 which is further downstream than the catalyst unit 79 is set as a downstream exhaust pipe 275b. The downstream exhaust pipe 275 b is disposed inside the muffler 76. In addition, in FIG. 18, the exhaust pipe 275 is drawn in a straight line for simplifying the description, but the exhaust pipe 275 is not a straight line.

As shown in FIG. 16, the main catalyst 180 is disposed further behind the crank line Cr2. That is, when viewed from the left and right directions, the main catalyst 180 is disposed behind the straight line L3. As described above, the straight line L3 is a straight line extending parallel to the vertical direction through the crankshaft line Cr2. When viewed from the left and right directions, the main catalyst 180 is located in front of the cylinder axis Cy2.

As shown in FIG. 16, when viewed from the left and right directions, the main catalyst 180 is located behind the straight line L4. The straight line L4 is a straight line orthogonal to the cylinder axis Cy2 and orthogonal to the crank line Cr2.

As shown in FIG. 18, the path length from the upstream end of the exhaust pipe 275 to the upstream end of the main catalyst 180 is set to b12. The path length from the downstream end of the autonomous catalyst 180 to the downstream end of the exhaust pipe 275 is set to d12. The path from the combustion chamber 70 to the upstream end of the main catalyst 180 is a2 + b12. The path length from the downstream end of the autonomous catalyst 180 to the release outlet 76e is d12 + e2.

As in the second embodiment, the main catalyst 180 of the modified example 2-1 is arranged at a position where the path length a2 + b12 is shorter than the path length d12 + e2. Also, unlike the second embodiment described above, the main catalyst 180 of the modification 2-1 is arranged at a position where the path length a2 + b12 is longer than the path length d12. Furthermore, unlike the second embodiment described above, the main catalyst 180 of the modification 2-1 is arranged at a position where the path length b12 is longer than the path length d12.

The upstream oxygen detection member 77 is disposed in the exhaust pipe 275. Upstream oxygen detection member 77 series It is placed further upstream than the main catalyst 180. The upstream oxygen detection member 77 is disposed in the upstream exhaust pipe 275a (see FIG. 18).

As shown in FIG. 18, the path length from the combustion chamber 70 to the upstream oxygen detection member 77 is set to h13. The path length from the upstream oxygen detection member 77 to the upstream end of the main catalyst 180 is set to h14. As in the second embodiment, the upstream oxygen detecting means 77 is arranged at a position where the path length h13 is shorter than the path length h14.

The downstream oxygen detection member 78 is disposed in the exhaust pipe 275. The downstream oxygen detecting member 78 is disposed further downstream than the main catalyst 180. The downstream oxygen detection member 78 is arranged in the downstream exhaust pipe 275a (see FIG. 18). The downstream oxygen detecting member 78 is disposed more upstream than the muffler 76.

In the modification 2-1, the same configuration as the above-mentioned first embodiment achieves the effects described in the first embodiment.

(Embodiment 3)

Fig. 19 is a side view of a locomotive according to a third embodiment of the present invention. Fig. 20 is a bottom view of the locomotive according to the third embodiment. Fig. 21 is a side view showing a state in which a car body shell and the like of the locomotive of the third embodiment are removed. Fig. 22 is a bottom view of a state in which a vehicle body shell and the like of the locomotive of the third embodiment are removed. Fig. 23 is a schematic diagram showing an engine and an exhaust system of a locomotive according to the third embodiment.

The vehicle according to the third embodiment is a so-called speed locomotive 80. As shown in FIG. 21, the locomotive 80 includes a vehicle body frame 81. The vehicle body frame 81 includes a head pipe 81a, a main frame 81b, a left and right pair of side frames 81c, a left and right pair of rear frames 81d, and a left and right pair of seat portion frames 81e. The main frame 81b extends rearward and downward from the head pipe 81a. The left and right pair of side frames 81c extend substantially horizontally downward from the lower end portion of the autonomous frame 81b. A pair of left and right rear frames 81d extend from the rear ends of the side frames 81c toward the upper rear. The pair of left and right seat frame 81e extends substantially horizontally from the rear end of the rear frame 81d to the rear.

A freely rotatable steering shaft is inserted into the head pipe 81a. A handle 82 is provided above the steering shaft. A display device (not shown) is arranged near the handle 82. A car is displayed on the display device Speed, engine speed, various warnings, etc.

A pair of left and right front forks 83 are supported below the steering shaft. A front wheel 84 is supported at the lower end of the front fork 83 for free rotation.

A leg plate 85 is attached to the left and right pair of side frames 81c (see FIG. 19). The footrest 85 is a place where a rider who sits on the seat portion 86 described later places his feet.

A seat portion 86 is supported on the seat portion frame 81e (see FIG. 19). The seat portion 86 extends from the middle portion of the vehicle body frame 81 toward the rear end portion in the vehicle front-rear direction.

A space G1 is formed below the seat portion 86 (see FIG. 21). A storage box (not shown) is arranged in the space G1. The storage box is formed in a box shape with an open top. The seat 86 also functions as a lid for opening and closing an opening on the upper surface of the storage box. The storage box is arranged between the left and right seat frame 81e. The storage box is supported by the rear frame 81d and the seat frame 81e.

As shown in FIG. 19, the locomotive 80 includes a vehicle body casing 87 that covers a vehicle body frame 81 and the like. The vehicle body casing 87 includes a front casing 87a, a leg shield 87b, a main casing 87c, and a bottom casing 87d. The front case 87a is disposed in front of the head pipe 81a. The leg shield 87b is disposed behind the head tube 81a. The front shell 87a and the leg shield 87b cover the head pipe 81a and the main frame 81b. The main casing 87c has a form in which the rear portion of the leg plate 85 is erected upward. The main case 87c covers substantially the entirety of the storage box. The bottom case 87d is disposed below the front case 87a, the leg shield 87b, and the main case 87c. The bottom case 87d covers the front upper part of the engine body 94 described later from the front, left and right sides.

A single-cylinder four-stroke engine unit 93 of a unit swing type is attached to the vehicle body frame 81. The single-cylinder four-stroke engine unit 93 includes an engine body 94 and a power transmission unit 95 (see FIGS. 20 and 22). The power transmission section 95 is connected to the rear of the engine body 94. The power transmission unit 95 is disposed on the left side of the engine body 94. A transmission is housed in the power transmission unit 95. The power transmission section 95 supports the rear wheels 88 so as to be rotatable.

The engine body 94 and the power transmission portion 95 can swing integrally with respect to the vehicle body frame 81. Specifically, as shown in FIGS. 21 and 22, right and left link members 90R and 90L are connected to left and right end portions of the lower portion of the engine body 94. Right link member 90R and left link The member 90L extends forward from the engine body 94. A front end portion of each of the right link member 90R and the left link member 90L is rotatably connected to the vehicle body frame 81 via a pivot shaft 89. The right link member 90R and the left link member 90L are rotatably connected to the engine body 94 via a pivot shaft 91 (see FIG. 21). In addition, FIG. 20 is a display which partially removed the right link member 90R and the engine body 94 and the wind deflector 96 described later.

The single-cylinder four-stroke engine unit 93 includes an engine body 94, a power transmission unit 95, an air cleaner (not shown), an intake pipe 110 (see FIG. 23), an exhaust pipe 111, a muffler 112, and a main catalyst 116 (single The main catalyst for the combustion chamber), the upstream oxygen detection means 113 (the upstream oxygen detection means for the single combustion chamber), and the downstream oxygen detection means 114 (the upstream oxygen detection means for the single combustion chamber). The single-cylinder four-stroke engine unit 93 includes the same electronic control unit as the electronic control unit 45 of the first embodiment. The electronic control unit controls the engine body 94.

The engine body 94 is a single-cylinder four-stroke engine. The engine body 94 is a forced air-cooled engine. The engine body 94 includes a wind deflector 96, a fan 97, a crankcase portion 98, and a cylinder portion 99.

The cylinder portion 99 extends forward from the crankcase portion 98. The air deflector 96 covers the entire periphery of the rear part of the cylinder part 99. Specifically, the air deflector 96 covers the entire circumference of the entire cylinder block 101 and the entire cylinder head 102 described later. However, the periphery of the exhaust pipe 111 connected to the cylinder head 102 is not covered. The air deflector 96 covers a right side portion of the crankcase portion 98.

The fan 97 is disposed between the air deflector 96 and the crankcase portion 98. A portion of the air deflector 96 facing the fan 97 is formed with an inlet for inhaling air. The fan 97 generates airflow for cooling the engine body 94. More specifically, the air is introduced into the wind guide plate 96 by the rotation of the fan 97. The airflow hits the engine body 94 to cool the crankcase portion 98 and the cylinder portion 99.

The crankcase portion 98 includes a crankcase body 100, a crankshaft 104 accommodated in the crankcase body 100, and the like. The center line (crank line) Cr3 of the crankshaft 104 extends in the left-right direction. A fan 97 capable of integral rotation is connected to a right end portion of the crankshaft 104. Fan 97 is rotated by crankshaft 104 Driven instead. Lubricating oil is stored in the crankcase body 100. This oil is transported by an oil pump (not shown) and circulates in the engine body 94.

The cylinder portion 99 includes a cylinder block 101, a cylinder head 102, a head cover 103, and components housed therein. As shown in FIG. 20, the cylinder block 101 is connected to the front portion of the crankcase body 100. The cylinder head 102 is connected to the front of the cylinder block 101. The head cover 103 is connected to the front of the cylinder head 102.

As shown in FIG. 23, a cylinder hole 101 a is formed in the cylinder block 101. A reciprocating piston 105 is housed in the cylinder hole 101a. The piston 105 is connected to the crankshaft 104 via a connecting rod. Hereinafter, the center line Cy3 of the cylinder hole 101a is referred to as a cylinder axis Cy3. As shown in FIG. 21, the engine body 94 is arrange | positioned so that the cylinder axis Cy3 may extend along a front-back direction. More specifically, the direction of the cylinder axis Cy3 from the crankcase portion 98 toward the cylinder portion 99 is forward and upward. The inclination angle of the cylinder axis Cy3 with respect to the horizontal direction is 0 degrees or more and 45 degrees or less.

As shown in FIG. 23, a combustion chamber 106 is formed inside the cylinder portion 99. The combustion chamber 106 is formed by an inner surface of a cylinder hole 101 a of a cylinder block 101, a cylinder head 102, and a piston 105. As shown in FIG. 21, the combustion chamber 106 is located further forward than the crank line Cr3. This situation is replaced by the following expression. A straight line extending parallel to the vertical direction through the crankshaft line Cr3 is defined as L5. When viewed from the left and right, the combustion chamber 106 is arranged in front of the straight line L5.

As shown in FIG. 23, a cylinder intake passage portion 107 and a cylinder exhaust passage portion 108 (a cylinder exhaust passage portion for a single combustion chamber) are formed in the cylinder head 102. In the cylinder head 102, an intake port 107 a and an exhaust port 108 a are formed on a wall portion forming the combustion chamber 106. The cylinder intake passage 107 is an intake port extending from the intake port 107 a to an outer surface (upper surface) of the cylinder head 102. The cylinder exhaust passage portion 108 extends from the exhaust port 108 a to a discharge port formed on the outer surface (lower surface) of the cylinder head 102. The air supplied to the combustion chamber 106 passes through the cylinder intake passage 107. The exhaust gas discharged from the combustion chamber 106 passes through the cylinder exhaust passage portion 108.

An intake valve V5 is disposed in the cylinder intake passage portion 107. For cylinder exhaust passage 108 It is equipped with an exhaust valve V6. The intake port 107a is opened and closed by the movement of the intake valve V5. The exhaust port 108a is opened and closed by the movement of the exhaust valve V6. An intake pipe 110 is connected to an end (suction port) of the cylinder intake passage portion 107. An exhaust pipe 111 is connected to an end portion (discharge port) of the cylinder exhaust passage portion 108. The path length of the cylinder exhaust passage portion 108 is set to a3.

As described above, FIG. 20 is a display with the right link member 90R, the wind deflector 96, and the like partially removed. Thereby, the connection portion between the lower surface of the cylinder head 102 and the exhaust pipe 111 can be seen. As shown in FIGS. 20 and 22, when viewed from below, the upstream end portion of the exhaust pipe 111 is located between the right link member 90R and the left link member 90L. However, as shown in FIG. 21, the exhaust pipe 111 passes above the right link member 90R and the left link member 90L when viewed from the left and right directions. Therefore, the exhaust pipe 111 does not pass between the right link member 90R and the left link member 90L.

The single-cylinder four-stroke engine unit 93 is provided with a spark plug, a valve mechanism, an injector, and a throttle valve in the same manner as the engine body 20 of the first embodiment. The single-cylinder four-stroke engine unit 93 is provided with various sensors such as an engine speed sensor and a throttle opening sensor, as in the first embodiment.

As described above, the single-cylinder four-stroke engine unit 93 includes the engine body 94, the exhaust pipe 111, the muffler 112, the main catalyst 116, the upstream oxygen detection member 113, and the downstream oxygen detection member 114. The muffler 112 has a release port 112e facing the atmosphere. The path from the combustion chamber 106 to the outlet 112e is referred to as an exhaust path 118 (see FIG. 23). The exhaust path 118 is formed by a cylinder exhaust passage portion 108, an exhaust pipe 111, and a muffler 112. The exhaust path 118 is a space through which exhaust gas passes.

As shown in FIG. 23, the upstream end portion of the exhaust pipe 111 is connected to the cylinder exhaust passage portion 108. The downstream end of the exhaust pipe 111 is connected to the muffler 112. A catalyst unit 115 is provided in the middle of the exhaust pipe 111. The upstream portion of the exhaust pipe 111 that is more upstream than the catalyst unit 115 is an upstream exhaust pipe 111a. A portion of the exhaust pipe 111 that is further downstream than the catalyst unit 115 is set as a downstream exhaust pipe 111b. In addition, in FIG. 23, the exhaust pipe 111 is drawn in a straight line for simplifying the description, but the exhaust pipe 111 is not a straight line.

As shown in FIG. 20, the exhaust pipe 111 is provided on the right portion of the locomotive 80. As shown in FIG. 21, a part of the exhaust pipe 111 is located below the crank line Cr3. The exhaust pipe 111 has two curved portions. An upstream bent portion of the two bent portions is simply referred to as an upstream bent portion. The downstream bent portion of the two bent portions is simply referred to as a downstream bent portion. Viewed from the left and right directions, the upstream curved portion changes the exhaust gas flow direction from downward to rearward and downward. Viewed from the left and right directions, the downstream curved portion changes the direction of exhaust gas flow from rearward downward to rearward upward. The portion further downstream than the downstream bent portion is located below the crank line Cr3. The downstream end of the main catalyst 116 is disposed at a downstream bent portion.

The muffler 112 flows into the exhaust gas discharged from the downstream end of the exhaust pipe 111. The muffler 112 is connected to the exhaust pipe 111. The muffler 112 is configured to suppress the rhythmic wave of the exhaust gas. Thereby, the muffler 112 can reduce the volume of the sound (exhaust sound) generated by the exhaust gas. A plurality of expansion chambers and a plurality of pipes connecting the expansion chambers to each other are provided in the muffler 112. The downstream end of the exhaust pipe 111 is arranged in the expansion chamber of the muffler 112. A release port 112e facing the atmosphere is provided at the downstream end of the muffler 112. As shown in FIG. 23, the path length of the exhaust path from the downstream end of the exhaust pipe 111 to the release port 112e is set to e3. The exhaust gas passing through the muffler 112 is released to the atmosphere from the self-release outlet 112e. As shown in FIG. 21, the release port 112e is located further behind the crank line Cr3.

The main catalyst 116 is disposed in the exhaust pipe 111. The upstream end of the main catalyst 116 is disposed further upstream than the upstream end 112 a of the muffler 112. The catalyst unit 115 includes a cylindrical case 117 and a main catalyst 116. The upstream end of the casing 117 is connected to the upstream exhaust pipe 111a. The downstream end of the casing 117 is connected to the downstream exhaust pipe 111b. The casing 117 constitutes a part of the exhaust pipe 111. The main catalyst 116 is fixed inside the casing 117. The exhaust gas is purified by passing through the main catalyst 116. All exhaust gases discharged from the exhaust port 108 a of the combustion chamber 106 pass through the main catalyst 116. The main catalyst 116 purifies the exhaust gas discharged from the combustion chamber 106 to the maximum extent in the exhaust path 118.

The material of the main catalyst 116 is the same as that of the main catalyst 39 of the first embodiment. Main catalyst 116 has a porous structure. A plurality of holes are formed in the main catalyst 116 sufficiently finely than the path width of the upstream exhaust pipe 111a. As shown in FIG. 23, the length in the path direction of the main catalyst 116 is c3. The maximum width of the main catalyst 116 in a direction perpendicular to the path direction is set to w3. The length c3 of the main catalyst 116 is longer than the maximum width w3 of the main catalyst 116.

As shown in FIG. 23, the case 117 includes a catalyst arrangement passage portion 117b, an upstream passage portion 117a, and a downstream passage portion 117c. A main catalyst 116 is arranged in the catalyst arrangement passage portion 117b. In the direction of the path, the upstream end and the downstream end of the catalyst arrangement passage portion 117 b are at the same positions as the upstream end and the downstream end of the main catalyst 116, respectively. The area of the cross section orthogonal to the path direction of the catalyst arrangement passage portion 117b is substantially constant. The upstream passage portion 117a is connected to the upstream end of the catalyst arrangement passage portion 117b. The downstream passage portion 117c is connected to the upstream end of the catalyst arrangement passage portion 117b.

At least a part of the upstream passage portion 117a is formed in a tapered shape. The tapered portion has a larger inner diameter toward the downstream. At least a part of the downstream passage portion 117c is formed in a tapered shape. The tapered portion has a smaller inner diameter toward the downstream. The area of a cross section orthogonal to the path direction of the catalyst arrangement passage portion 117b is S3. The area of the cross section orthogonal to the path direction of the upstream end (at least a part) of the upstream passage portion 117a is smaller than the area S3. The area of at least a portion of the downstream passage portion 117c that is orthogonal to the path direction is smaller than the area S3. Here, at least a part of the downstream passage portion 117c includes a downstream end of the downstream passage portion 117c.

As shown in FIG. 21, the main catalyst 116 is disposed further forward than the crank line Cr3. That is, when viewed from the left and right directions, the main catalyst 116 is disposed in front of the straight line L5. As described above, the straight line L5 is a straight line extending parallel to the vertical direction through the crankshaft line Cr3. Of course, the upstream end of the main catalyst 116 is also disposed more forward than the crank line Cr3. When viewed from the left and right directions, the main catalyst 116 is positioned in front of (below) the cylinder axis Cy3.

As shown in FIG. 21, a straight line orthogonal to the cylinder axis Cy3 and orthogonal to the crank line Cr3 is defined as L6. Viewed from the left and right directions, the main catalyst 116 is located in front of the straight line L6.

As shown in FIG. 23, from the upstream end of the exhaust pipe 111 to the upstream end of the main catalyst 116 The path length is set to b3. The path length b3 is the path length of the passage portion including the upstream exhaust pipe 111a and the upstream passage portion 117a of the catalyst unit 115. In other words, the path length b3 is a path length from the downstream end of the cylinder exhaust passage portion 108 to the upstream end of the main catalyst 116. The path length from the downstream end of the autonomous catalyst 116 to the downstream end of the exhaust pipe 111 is d3. The path length d3 is a path length including the downstream passage portion 117c of the catalyst unit 115 and the passage portion of the downstream exhaust pipe 111b. The path from the combustion chamber 106 to the upstream end of the main catalyst 116 is a3 + b3. The path length from the downstream end of the autonomous catalyst 116 to the release outlet 112e is d3 + e3.

As in the first embodiment, the main catalyst 116 is disposed at a position where the path length a3 + b3 is shorter than the path length d3 + e3. In addition, as in the first embodiment, the main catalyst 116 is disposed at a position where the path length a3 + b3 is shorter than the path length d3. Furthermore, as in the first embodiment, the main catalyst 116 is disposed at a position where the path length b3 is shorter than the path length d3.

The upstream oxygen detection member 113 is arranged in the exhaust pipe 111. The upstream oxygen detection member 113 is disposed further upstream than the main catalyst 116. The upstream oxygen detection member 113 is arranged in the upstream exhaust pipe 111a (see FIG. 23). The upstream oxygen detecting means 113 is a sensor that detects the oxygen concentration contained in the exhaust gas. The structure of the upstream oxygen detecting means 113 is the same as that of the upstream oxygen detecting means of the first embodiment.

As shown in FIG. 23, the path length from the combustion chamber 106 to the upstream oxygen detection member 113 is set to h5. The path length from the upstream oxygen detection member 113 to the upstream end of the main catalyst 116 is set to h6. Unlike the first embodiment, the upstream oxygen detecting means 113 is arranged at a position where the path length h5 is longer than the path length h6.

The downstream oxygen detection member 114 is disposed in the exhaust pipe 111. The downstream oxygen detecting member 114 is disposed further downstream than the main catalyst 116. The downstream oxygen detection member 114 is disposed in a case 117 of the catalyst unit 115. More specifically, the downstream oxygen detection member 114 is disposed in the downstream passage portion 117c (see FIG. 23). The downstream oxygen detecting member 114 is a sensor that detects the oxygen concentration contained in the exhaust gas. The structure of the downstream oxygen detection member 114 is the same as that of the upstream oxygen detection member 37 of the first embodiment.

As described above, the locomotive 80 according to the third embodiment includes the upstream oxygen detection means 113 and the downstream oxygen detection means 114 upstream and downstream of the main catalyst 116. Otherwise, it has the same arrangement relationship as the locomotive 1 of the first embodiment. Regarding the same arrangement relationship as the first embodiment, the same effect as that described in the first embodiment is achieved.

The path length (h5) from one combustion chamber 106 to the upstream end of the upstream oxygen detection member 113 is longer than the path length (h6) from the upstream oxygen detection member 113 to the upstream end of the main catalyst 116. Therefore, the upstream oxygen detection member 113 is disposed near the main catalyst 116. Therefore, the oxygen concentration of the exhaust gas flowing into the main catalyst 116 can be detected more accurately. Thereby, the combustion control based on the signal of the upstream oxygen detection means 113 can be performed more accurately. As a result, the exhaust gas purification performance of the main catalyst 116 can be further improved. In addition, by improving the accuracy of the combustion control, the progress of the deterioration of the main catalyst 116 can be slowed down. Therefore, the initial performance of the locomotive 80 with respect to exhaust gas purification can be maintained for a longer time.

In addition, the locomotive 80 of the third embodiment can also apply the configuration of the exhaust system of the aforementioned modification 1-2. In this case, the same effect as that of Modification 1-2 is obtained.

(Modification 3-1 of Embodiment 3)

FIG. 24 is a side view showing a state in which a vehicle body shell and the like of a locomotive according to Modification 3-1 of Embodiment 3 is removed. Fig. 25 is a bottom view of a state in which a vehicle body shell and the like of a locomotive according to Modification 3-1 of Embodiment 3 is removed. FIG. 26 is a schematic diagram showing an engine body and an exhaust system according to Modification 3-1 of Embodiment 3. FIG. In Modified Example 3-1, the same constituent elements as those in Embodiment 3 are denoted by the same reference numerals and detailed descriptions are omitted.

As shown in FIG. 24, compared to the third embodiment, the main catalyst 116 of the modified example 3-1 is arranged downstream. The specific structure of the main catalyst 116 is the same as that of the third embodiment. The main catalyst 116 of the modified example 3-1 is arranged in the exhaust pipe 2111. As in the third embodiment, the upstream end of the main catalyst 116 is disposed further upstream than the upstream end 112 a of the muffler 112.

The exhaust pipe 2111 is connected to the cylinder exhaust passage portion 108 (see FIG. 26) and the muffler 112 in the same manner as the exhaust pipe 111 of the third embodiment. A catalyst sheet is provided in the middle of the exhaust pipe 2111 $ 2115. As shown in FIG. 26, the exhaust pipe 2111 is positioned upstream of the catalyst unit 2115 as an upstream exhaust pipe 2111 a. A portion of the exhaust pipe 2111 that is further downstream than the catalyst unit 2115 is set as a downstream exhaust pipe 2111b. The downstream exhaust pipe 2111b is arranged inside the muffler 112. In addition, in FIG. 26, the exhaust pipe 2111 is drawn in a straight line for simplifying the description, but the exhaust pipe 2111 is not a straight line.

The catalyst unit 2115 includes a main catalyst 116 and a case 2117. The housing 2117 includes an upstream passage portion 2117a, a catalyst arrangement passage portion 2117b, and a downstream passage portion 2117c. In the path direction, the upstream end and the downstream end of the catalyst arrangement passage portion 2117b are at the same positions as the upstream end and the downstream end of the main catalyst 116, respectively.

As shown in FIG. 24, the main catalyst 116 is disposed further behind the crank line Cr3. That is, when viewed from the left and right directions, the main catalyst 116 is disposed behind the straight line L5. As described above, the straight line L5 is a straight line extending parallel to the vertical direction through the crankshaft line Cr3. When viewed from the left and right directions, the main catalyst 116 is positioned in front of (below) the cylinder axis Cy3.

As shown in FIG. 24, when viewed from the left and right directions, the main catalyst 116 is located behind the straight line L6. The straight line L6 is a straight line orthogonal to the cylinder axis Cy3 and orthogonal to the crankshaft line Cr3.

As shown in FIG. 26, the path length from the upstream end of the exhaust pipe 2111 to the upstream end of the main catalyst 116 is set to b13. The path length from the downstream end of the autonomous catalyst 116 to the downstream end of the exhaust pipe 2111 is set to d13. The path from the combustion chamber 106 to the upstream end of the main catalyst 116 is a3 + b13. The path length from the downstream end of the autonomous catalyst 116 to the release outlet 112e is d13 + e3.

As in the third embodiment, the main catalyst 116 of the modified example 3-1 is arranged at a position where the path length a3 + b13 is shorter than the path length d13 + e3. In addition, unlike the third embodiment, the main catalyst 116 of the modified example 3-1 is arranged at a position where the path length a3 + b13 is longer than the path length d13. Furthermore, unlike the third embodiment, the main catalyst 116 of the modified example 3-1 is arranged at a position where the path length b13 is longer than the path length d13.

The upstream oxygen detection member 113 is disposed on the exhaust pipe 2111. The upstream oxygen detection member 113 is disposed further upstream than the main catalyst 116. The upstream oxygen detection member 113 is arranged in the upstream exhaust pipe 2111a (see FIG. 26).

As shown in FIG. 26, the path length from the combustion chamber 106 to the upstream oxygen detection member 113 is set to h15. The path length from the upstream oxygen detection member 113 to the upstream end of the main catalyst 116 is set to h16. Unlike the third embodiment described above, the upstream oxygen detecting means 113 is arranged at a position where the path length h15 is shorter than the path length h16. This configuration is the same as that of the first embodiment.

The downstream oxygen detection member 114 is disposed in the exhaust pipe 2111. The downstream oxygen detecting member 114 is disposed further downstream than the main catalyst 116. The downstream oxygen detection member 114 is disposed in the downstream exhaust pipe 2111b (see FIG. 26). The downstream oxygen detection member 114 penetrates a side wall portion of the muffler 112. One end portion (detection portion) of the downstream oxygen detection member 114 is disposed in the downstream exhaust pipe 2111b. The other end portion of the downstream oxygen detecting member 114 is disposed outside the muffler 112.

In the modification 3-1, the same configuration as the above-mentioned first embodiment achieves the effects described in the first embodiment.

(Embodiment 4)

Fig. 27 is a side view of a locomotive according to a fourth embodiment of the present invention. Fig. 28 is a bottom view of a locomotive according to the fourth embodiment. Fig. 29 is a side view showing a state in which a vehicle body shell and the like of the locomotive of the fourth embodiment are removed. Fig. 30 is a bottom view of a state in which a vehicle body shell and the like of the locomotive of the fourth embodiment are removed. Fig. 31 is a schematic diagram showing an engine and an exhaust system of a locomotive according to a fourth embodiment.

The vehicle according to the fourth embodiment is a so-called sports scooter 120 locomotive. As shown in FIG. 29, the locomotive 120 includes a vehicle body frame 121. The vehicle body frame 121 includes a head pipe 121a, a main frame 121b, a right seat rail 122R, a left seat rail 122L, a pair of left and right bottom frames 121c, and a cross member 121d (see FIG. 30). The main frame 121b extends rearward and downward from the head pipe 121a. The bottom frame 121c extends from the middle portion of the autonomous frame 121b toward the lower back, and then bends backward and extends substantially horizontally toward the rear. As shown in FIG. 30, the cross member 121d is connected to the left and right bottom frames 121c. The horizontal member 121d extends in the left-right direction. As shown in Figure 29, the left seat rail 122L The middle portion of the autonomous frame 121b extends upward and rearward. As shown in FIG. 30, the right seat rail 122R is connected to the right end portion of the cross member 121d. As shown in FIG. 29, the right seat rail 122R extends upward from the cross member 121d, and then bends rearward. The rear part of the right seat rail 122R extends substantially parallel to the left seat rail 122L.

A rotatable steering shaft is inserted into the head pipe 121a. A handle 123 is provided above the steering shaft. A display device (not shown) is arranged near the handle 123. The display device displays vehicle speed, engine speed, various warnings, and the like.

A pair of left and right front forks 124 are supported below the steering shaft. A front wheel 125 is supported at the lower end of the front fork 124 for free rotation.

The left and right seat rails 122L and 122R support seat portions 126 (see FIG. 27).

As shown in FIG. 27, the locomotive 120 includes a vehicle body casing 127 that covers a vehicle body frame 121 and the like. The vehicle body casing 127 includes a front casing 127a, a main casing 127b, and a bottom casing 127c. The front case 127a covers the upper portion of the head pipe 121a and the main frame 121b. The lower portion of the main frame 121b is covered by a main case 127b and a bottom case 127c. The main casing 127b covers the right seat rail 122R and the left seat rail 122L. The bottom case 127c covers the bottom frame 121c and the cross member 121d. The main casing 127b covers a front portion of an engine body 133 described later and an air cleaner 147 (see FIG. 29). The air cleaner 147 is disposed in front of the engine body 133.

A single-cylinder four-stroke engine unit 132 of a unit swing type is mounted on the vehicle body frame 121. The single-cylinder four-stroke engine unit 132 includes an engine body 133 and a power transmission unit 134 (see FIGS. 28 and 30). The power transmission portion 134 is connected to the rear portion of the engine body 133. The power transmission section 134 is disposed on the left side of the engine body 133. A transmission is housed in the power transmission section 134. The power transmission portion 134 supports the rear wheels 128 so as to be rotatable.

The engine body 133 and the power transmission part 134 can swing integrally with respect to the vehicle body frame 121. Specifically, as shown in FIGS. 29 and 30, right and left link members 130R and 130L are connected to left and right end portions of the lower portion of the engine body 133. The right link member 130R and the left link member 130L extend forward from the engine body 133. Right link member 130R and The front end of each of the left link members 130L is rotatably connected to the vehicle body frame 121 (the bottom frame 121c) via a pivot 129. The right link member 130R and the left link member 130L are rotatably connected to the engine body 133 via a pivot 131, respectively.

The single-cylinder four-stroke engine unit 132 is a water-cooled engine. The single-cylinder four-stroke engine unit 132 includes an engine body 133, a water cooling device 135, a power transmission unit 134, an air cleaner 147 (see FIGS. 29 and 30), an intake pipe 148 (see FIG. 29), an exhaust pipe 149, The muffler 150, the main catalyst 154 (main catalyst for single combustion chamber), the upstream oxygen detection member 151 (upstream oxygen detection member for single combustion chamber), and the downstream oxygen detection member 152 (upstream oxygen detection member for single combustion chamber). The single-cylinder four-stroke engine unit 132 includes the same electronic control unit as the electronic control unit 45 of the first embodiment. The electronic control unit controls the engine body 133.

The water cooling device 135 includes a radiator (not shown), a water pump (not shown), a fan (not shown), and a case portion 135a. The fan is disposed on the right side of the rear portion of the engine body 133. The heat sink is located on the right side of the fan. The case portion 135a covers the heat sink from the right side. Furthermore, the case portion 135a covers the radiator and the fan from above, below, and from front to back.

The engine body 133 is a single-cylinder four-stroke engine. As shown in FIG. 29, the engine body 133 includes a crankcase portion 136 and a cylinder portion 137. The cylinder portion 137 extends forward from the crankcase portion 136.

The crankcase portion 136 includes a crankcase body 138, a crankshaft 142 housed in the crankcase body 138, and the like. A center line (crank line) Cr4 of the crankshaft 142 extends in the left-right direction. Lubricating oil is stored in the crankcase body 138. This oil is transported by an oil pump (not shown) and circulates in the engine body 133.

A fan of an integrally rotatable water cooling device 135 is connected to the right end of the crankshaft 142. The fan is driven by the rotation of the crankshaft 142. The fan generates airflow for cooling the engine body 133. More specifically, air is sucked into the housing portion 135a by the rotation of the fan. The sucked air exchanges heat with the cooling water of the radiator, thereby cooling the cooling water. but. Then, the engine body 133 is cooled by the cooled cooling water.

The cylinder portion 137 includes a cylinder block 139, a cylinder head 140, a head cover 141, and components housed therein. 29 and 30, the cylinder block 139 is connected to the front portion of the crankcase body 138. The cylinder head 140 is connected to the front of the cylinder block 139. As shown in FIG. 29, the head cover 141 is connected to the front of the cylinder head 140.

As shown in FIG. 31, a cylinder hole 139 a is formed in the cylinder block 139. A reciprocating piston 143 is housed in the cylinder hole 139a. The piston 143 is connected to the crankshaft 142 via a connecting rod. Hereinafter, the center line Cy4 of the cylinder hole 139a is referred to as a cylinder axis Cy4. As shown in FIG. 29, the engine body 133 is arranged so that the cylinder axis Cy4 extends in the front-rear direction. More specifically, the direction of the crankcase portion 136 from the cylinder axis Cy4 toward the cylinder portion 137 is forward and upward. The inclination angle of the cylinder axis Cy4 with respect to the horizontal direction is 0 degrees or more and 45 degrees or less.

As shown in FIG. 31, a combustion chamber 144 is formed inside the cylinder portion 137. The combustion chamber 144 is formed by an inner surface of a cylinder hole 139 a of the cylinder block 139, a cylinder head 140, and a piston 143. As shown in FIG. 20, the combustion chamber 144 is located further forward than the crank line Cr4. This situation is replaced by the following expression. A straight line extending parallel to the vertical direction through the crankshaft line Cr4 is defined as L7. When viewed from the left and right directions, the combustion chamber 144 is arranged in front of the straight line L7.

As shown in FIG. 31, a cylinder intake passage 145 and a cylinder exhaust passage 146 (a single combustion chamber cylinder exhaust passage) are formed in the cylinder head 140. In the cylinder head 140, an intake port 145 a and an exhaust port 146 a are formed on a wall portion forming the combustion chamber 144. The cylinder intake passage portion 145 extends from the intake port 145 a to an intake port formed on the outer surface (upper surface) of the cylinder head 140. The cylinder exhaust passage portion 146 extends from the exhaust port 146 a to a discharge port formed on the outer surface (lower surface) of the cylinder head 140. The air supplied to the combustion chamber 144 passes through the cylinder intake passage portion 145. The exhaust gas discharged from the combustion chamber 144 passes through the cylinder exhaust passage portion 146.

An intake valve V7 is disposed in the cylinder intake passage portion 145. An exhaust valve V8 is disposed in the cylinder exhaust passage portion 146. The intake port 145a is opened and closed by the movement of the intake valve V7. exhaust The port 146a is opened and closed by the movement of the exhaust valve V8. An intake pipe 148 is connected to an end portion (suction port) of the cylinder intake passage portion 145. An exhaust pipe 149 is connected to an end portion (discharge port) of the cylinder exhaust passage portion 146. The path length of the cylinder exhaust passage portion 146 is set to a4.

As shown in FIG. 30, the exhaust pipe 149 is connected to the lower surface of the cylinder head 140. Viewed from below, the upstream end of the exhaust pipe 149 is located between the right link member 130R and the left link member 130L. Further, as shown in FIG. 29, when viewed from the left and right directions, a part of the exhaust pipe 149 overlaps the right link member 130R and the left link member 130L. Therefore, the exhaust pipe 149 passes between the right link member 130R and the left link member 130L.

The single-cylinder four-stroke engine unit 132 is provided with a spark plug, a valve operating mechanism, an injector, and a throttle in the same manner as in the first embodiment. The single-cylinder four-stroke engine unit 132 includes various sensors such as an engine speed sensor and a throttle opening sensor, as in the first embodiment.

As described above, the single-cylinder four-stroke engine unit 132 includes the engine body 133, the exhaust pipe 149, the muffler 150, the main catalyst 154, the upstream oxygen detection member 151, and the downstream oxygen detection member 152. The muffler 150 has a release port 150e facing the atmosphere. The path from the combustion chamber 144 to the release port 150e is set as an exhaust path 156 (see FIG. 31). The exhaust path 156 is formed by a cylinder exhaust passage portion 146, an exhaust pipe 149, and a muffler 150. The exhaust path 156 is a space through which exhaust gas passes.

As shown in FIG. 31, the upstream end portion of the exhaust pipe 149 is connected to the cylinder exhaust passage portion 146. A downstream end portion of the exhaust pipe 149 is connected to the muffler 150. A catalyst unit 153 is provided in the middle of the exhaust pipe 149. A part of the exhaust pipe 149 which is more upstream than the catalyst unit 153 is an upstream exhaust pipe 149a. A portion of the exhaust pipe 149 that is further downstream than the catalyst unit 153 is a downstream exhaust pipe 149b. In addition, in FIG. 31, the exhaust pipe 149 is drawn in a straight line for simplifying the description, but the exhaust pipe 149 is not a straight line.

As shown in FIGS. 28 and 30, most of the exhaust pipe 149 is provided on the right side of the locomotive 120. An upstream end portion of the exhaust pipe 149 is located at a substantially central portion in the left-right direction of the locomotive 120. As shown in FIG. 29, a part of the exhaust pipe 149 is located below the crank line Cr4. Exhaust pipe 149 There are 2 bends. An upstream bent portion of the two bent portions is simply referred to as an upstream bent portion. The downstream bent portion of the two bent portions is simply referred to as a downstream bent portion. Viewed from the left and right directions, the upstream curved portion changes the direction of exhaust gas flow from a direction extending in the up-down direction to a direction extending in the front-rear direction. More specifically, when viewed from the left and right directions, the upstream curved portion changes the exhaust gas flow direction from downward to rearward and downward. Viewed from the left and right directions, the downstream curved portion changes the direction of exhaust gas flow from backward to downward and rearward. A portion further downstream than the downstream bent portion is located below the crank line Cr4. The main catalyst 154 is disposed between the two curved portions.

The muffler 150 flows into the exhaust gas discharged from the downstream end of the exhaust pipe 149. The muffler 150 is connected to the exhaust pipe 149. The muffler 150 is configured to suppress the rhythmic wave of the exhaust gas. Thereby, the muffler 150 can reduce the volume of the sound (exhaust sound) generated by the exhaust gas. A plurality of expansion chambers and a plurality of pipes connecting the expansion chambers to each other are provided in the muffler 150. The downstream end of the exhaust pipe 149 is disposed in the expansion chamber of the muffler 150. A release port 150e facing the atmosphere is provided at the downstream end of the muffler 150. As shown in FIG. 31, the path length of the exhaust path from the downstream end of the exhaust pipe 149 to the release port 150e is set to e4. The exhaust gas passing through the muffler 150 is released to the atmosphere from the self-release outlet 150e. As shown in FIG. 29, the release port 150e is located further behind the crank line Cr4.

The main catalyst 154 is disposed in the exhaust pipe 149. The upstream end of the main catalyst 154 is disposed further upstream than the upstream end 150 a of the muffler 150. The catalyst unit 153 includes a cylindrical case 155 and a catalyst unit 153. The upstream end of the casing 155 is connected to the upstream exhaust pipe 149a. The downstream end of the casing 155 is connected to the downstream exhaust pipe 149b. The casing 155 constitutes a part of the exhaust pipe 149. The main catalyst 154 is fixed inside the casing 155. The exhaust gas is purified by passing through the main catalyst 154. All the exhaust gas discharged from the exhaust port 146 a of the combustion chamber 144 passes through the main catalyst 154. The main catalyst 154 purifies the exhaust gas discharged from the combustion chamber 144 in the exhaust path 156 to the greatest extent.

The material of the main catalyst 154 is the same as that of the main catalyst 39 of the first embodiment. Main catalyst The agent 154 has a porous structure. The main catalyst 154 is formed with a plurality of holes which are sufficiently finer than the path width of the upstream exhaust pipe 149a. As shown in FIG. 31, the length in the path direction of the main catalyst 154 is c4. The maximum width of the main catalyst 154 in a direction perpendicular to the path direction is set to w4. The length c4 of the main catalyst 154 is longer than the maximum width w4 of the main catalyst 154.

As shown in FIG. 31, the case 155 includes a catalyst arrangement passage portion 155b, an upstream passage portion 155a, and a downstream passage portion 155c. A main catalyst 154 is arranged in the catalyst arrangement passage portion 155b. In the path direction, the upstream end and the downstream end of the catalyst arrangement passage portion 155b are at the same positions as the upstream end and the downstream end of the main catalyst 154, respectively. The area of the cross section orthogonal to the path direction of the catalyst arrangement passage portion 155b is substantially constant. The upstream passage portion 155a is connected to the upstream end of the catalyst arrangement passage portion 155b. The downstream passage portion 155c is connected to the upstream end of the catalyst arrangement passage portion 155b.

At least a part of the upstream passage portion 155a is formed in a tapered shape. The tapered portion has a larger inner diameter toward the downstream. At least a part of the downstream passage portion 155c is formed in a tapered shape. The tapered portion has a smaller inner diameter toward the downstream. The area of the cross section orthogonal to the path direction of the catalyst arrangement passage portion 155b is set to S4. The area of at least a portion of the upstream passage portion 155a that is orthogonal to the path direction is smaller than the area S4. At least a part of the upstream passage portion 155a here includes an upstream end of the upstream passage portion 155a. The area of at least a portion of the downstream passage portion 155c that is orthogonal to the path direction is smaller than the area S4. At least a part of the downstream passage portion 155c here includes a downstream end of the downstream passage portion 155c.

As shown in FIG. 29, the main catalyst 154 is disposed further forward than the crank line Cr4. That is, the main catalyst 154 is arranged in front of the straight line L7 when viewed from the left and right directions. As described above, the straight line L7 is a straight line extending parallel to the vertical direction through the crankshaft line Cr4. Of course, the upstream end of the main catalyst 154 is also disposed more forward than the crank line Cr4. When viewed from the left and right directions, the main catalyst 154 is positioned in front of (below) the cylinder axis Cy4.

As shown in FIG. 29, a straight line orthogonal to the cylinder axis Cy4 and orthogonal to the crank line Cr4 Set to L8. Viewed from the left and right directions, the main catalyst 154 is located in front of the straight line L8.

As shown in FIG. 31, the path length from the upstream end of the exhaust pipe 149 to the upstream end of the main catalyst 154 is set to b4. The path length b4 is the path length of the passage portion including the upstream exhaust pipe 149a and the upstream passage portion 155a of the catalyst unit 153. In other words, the path length b4 is a path length from the downstream end of the cylinder exhaust passage portion 146 to the upstream end of the main catalyst 154. The path length from the downstream end of the autonomous catalyst 154 to the downstream end of the exhaust pipe 149 is d4. The path length d4 is the path length of the path portion including the downstream passage portion 155c of the catalyst unit 153 and the downstream exhaust pipe 149b. The path length from the combustion chamber 144 to the upstream end of the main catalyst 154 is a4 + b4. The path length from the downstream end of the autonomous catalyst 154 to the release outlet 150e is d4 + e4.

As in the first embodiment, the main catalyst 154 is disposed at a position where the path length a4 + b4 is shorter than the path length d4 + e4. In addition, as in the first embodiment, the main catalyst 154 is disposed at a position where the path length a4 + b4 is shorter than the path length d4. Further, as in the first embodiment, the main catalyst 154 is disposed at a position where the path length b4 is shorter than the path length d4.

The upstream oxygen detection member 151 is disposed in the exhaust pipe 149. The upstream oxygen detection member 151 is disposed further upstream than the main catalyst 154. The upstream oxygen detection member 151 is a sensor that detects the oxygen concentration contained in the exhaust gas. The structure of the upstream oxygen detecting means 151 is the same as that of the upstream oxygen detecting means of the first embodiment.

As shown in FIG. 31, the path length from the combustion chamber 144 to the upstream oxygen detection member 151 is set to h7. The path length from the upstream oxygen detection member 151 to the upstream end of the main catalyst 154 is set to h8. As in the first embodiment, the upstream oxygen detecting means 151 is arranged at a position where the path length h7 is shorter than the path length h8.

As described above, the locomotive 120 according to the fourth embodiment includes an upstream oxygen detection member 151 and a downstream oxygen detection member 152 upstream and downstream of the main catalyst 154. Otherwise, it has the same arrangement relationship as the locomotive 1 of the first embodiment. Regarding the same arrangement relationship as the first embodiment, the same effect as that described in the first embodiment is achieved.

In addition, in the locomotive 120 according to the fourth embodiment, the exhaust gas of the above-mentioned modified example 1-2 may also be applied. The composition of the system. In this case, the same effect as that of Modification 1-2 is obtained.

(Modification 4-1 of Embodiment 4)

FIG. 32 is a side view showing a state in which a vehicle body shell and the like of a locomotive according to a modification 4-1 of the fourth embodiment is removed. FIG. 33 is a bottom view of a state in which a vehicle body shell and the like of a locomotive according to a modification 4-1 of the fourth embodiment is removed. Fig. 34 is a schematic diagram showing an engine body and an exhaust system according to a modification 4-1 of the fourth embodiment. In Modified Example 4-1, the same components as those in Embodiment 4 are denoted by the same reference numerals, and detailed descriptions are omitted.

As shown in FIG. 32, compared with the fourth embodiment, the main catalyst 154 of the modification 4-1 is disposed downstream. The specific structure of the main catalyst 154 is the same as that of the fourth embodiment. The main catalyst 154 of the modification 4-1 is arranged in the exhaust pipe 2149. As in the fourth embodiment, the upstream end of the main catalyst 154 is disposed further upstream than the upstream end 150 a of the muffler 150.

The exhaust pipe 2149 is connected to the cylinder exhaust passage portion 146 (see FIG. 34) and the muffler 150 in the same manner as the exhaust pipe 149 of the fourth embodiment. A catalyst unit 153 is provided in the middle of the exhaust pipe 2149. As shown in FIG. 34, the upstream part of the exhaust pipe 2149 which is more upstream than the catalyst unit 153 is set as the upstream exhaust pipe 2149a. A portion of the exhaust pipe 2149 further downstream than the catalyst unit 153 is set as a downstream exhaust pipe 2149b. The downstream exhaust pipe 2149b is disposed inside the muffler 150. In addition, in FIG. 34, the exhaust pipe 2149 is drawn in a straight line for simplifying the description, but the exhaust pipe 2149 is not a straight line.

As shown in FIG. 32, the main catalyst 154 is disposed further behind the crank line Cr4. That is, when viewed from the left and right directions, the main catalyst 154 is disposed behind the straight line L7. As described above, the straight line L7 is a straight line extending parallel to the vertical direction through the crankshaft line Cr4. When viewed from the left and right directions, the main catalyst 154 is positioned in front of (below) the cylinder axis Cy4.

As shown in FIG. 32, when viewed from the left and right directions, the main catalyst 154 is located behind the straight line L8. The straight line L8 is a straight line orthogonal to the cylinder axis Cy4 and orthogonal to the crankshaft line Cr4.

As shown in FIG. 34, from the upstream end of the exhaust pipe 2149 to the upstream end of the main catalyst 154 The path length is set to b14. The path length from the downstream end of the autonomous catalyst 154 to the downstream end of the exhaust pipe 2149 is set to d14. The path length from the combustion chamber 144 to the upstream end of the main catalyst 154 is a4 + b14. The path length from the downstream end of the autonomous catalyst 154 to the release outlet 150e is d14 + e4.

As in the fourth embodiment, the main catalyst 154 of the modified example 4-1 is arranged at a position where the path length a4 + b14 is shorter than the path length d14 + e4. In addition, unlike the fourth embodiment, the main catalyst 154 of the modified example 4-1 is arranged at a position where the path length a4 + b14 is longer than the path length d14. Furthermore, unlike the fourth embodiment, the main catalyst 154 of the modified example 4-1 is arranged at a position where the path length b14 is longer than the path length d14.

The upstream oxygen detection member 151 is disposed in the exhaust pipe 2149. The upstream oxygen detection member 151 is disposed further upstream than the main catalyst 154. The upstream oxygen detection member 151 is disposed in the upstream exhaust pipe 2149a (see FIG. 34).

As shown in FIG. 34, the path length from the combustion chamber 144 to the upstream oxygen detection member 151 is set to h17. The path length from the upstream oxygen detection member 151 to the upstream end of the main catalyst 154 is set to h18. As in the fourth embodiment, the upstream oxygen detecting means 151 is arranged at a position where the path length h17 is shorter than the path length h18.

The downstream oxygen detecting member 152 is disposed in the exhaust pipe 2149. The downstream oxygen detecting member 152 is disposed further downstream than the main catalyst 154. The downstream oxygen detection member 152 is disposed in the downstream exhaust pipe 2149b (see FIG. 34). The downstream oxygen detection member 152 penetrates a side wall portion of the muffler 150. One end portion (detection portion) of the downstream oxygen detection member 152 is disposed in the downstream exhaust pipe 2149b. The other end portion of the downstream oxygen detecting member 152 is disposed outside the muffler 150.

In the modification 4-1, the same configuration as the above-mentioned first embodiment achieves the effects described in the first embodiment.

As mentioned above, although the preferred embodiment of this invention was described, this invention is not limited to the said embodiment, Various changes are possible as long as it does not go beyond the description of a patent application range. In addition, the modification examples described later can be appropriately combined and implemented.

In the first to fourth embodiments, the casings 40, 181, 117, and 155 of the catalyst units 38, 79, 115, and 153 and the upstream exhaust pipes 34a, 75a, 111a, and 149a are respectively formed and then joined. However, the casings 40, 181, 117, and 155 of the catalyst units 38, 79, 115, and 153 and the upstream exhaust pipes 34a, 75a, 111a, and 149a may be integrally formed.

In Embodiments 1 to 4, the casings 40, 181, 117, and 155 of the catalyst units 38, 79, 115, and 153 and the downstream exhaust pipes 34b, 75b, 111b, and 149b are respectively formed and then joined. However, the casings 40, 181, 117, and 155 of the catalyst units 38, 79, 115, and 153 and the downstream exhaust pipes 34b, 75b, 111b, and 149b may be integrally formed.

The shape of the exhaust pipe 34 in the first embodiment is not limited to the shape shown in FIGS. 1 to 3. The internal structure of the muffler 35 is not limited to the structure shown in the schematic diagram of FIG. 5. The same applies to the exhaust pipes 75, 111, and 149, and the mufflers 76, 112, and 150 of the second to fourth embodiments.

In the first to fourth embodiments, the main catalysts 39, 116, 180, and 154 and the muffler 35, 76, 112, and 150 are arranged more to the right than the center in the left-right direction of the locomotive 1, 50, 80, and 120. However, the main catalyst and the muffler may also be arranged more to the left than the center in the left-right direction of the locomotive. In addition, the center of the locomotive in the left-right direction refers to a position passing a straight line between the center of the left-right direction of the front wheel and the center of the left-right direction of the rear wheel when viewed from the up-down direction.

In the first to fourth embodiments, a part of the exhaust pipes 34, 75, 111, and 149 is located below the crankshaft lines Cr1 to Cr4. However, a part of the exhaust pipe (exhaust pipe for a single combustion chamber) may be located above the crankshaft line.

In Embodiments 1 to 4, the main catalysts 39, 180, 116, and 154 are three-way catalysts. However, the single-chamber main catalyst of the present invention may not be a three-way catalyst. The main catalyst for a single combustion chamber may be a catalyst for removing any one or both of hydrocarbons, carbon monoxide, and nitrogen oxides. The main catalyst for a single combustion chamber may not be a redox catalyst. The main catalyst may be an oxidation catalyst or a reduction catalyst that removes harmful substances only by either oxidation or reduction. An example of a reduction catalyst is a reduction reaction. Catalyst for removing nitrogen oxides. This modification can also be applied to the upstream sub-catalyst 300.

In the first embodiment, the length c1 in the path direction of the main catalyst 39 is larger than the maximum width w1. The same applies to the main catalysts 180, 116, and 154 of Embodiments 2 to 4 described above. However, the main catalyst for a single combustion chamber of the present invention may have a length in a path direction shorter than a maximum width in a direction perpendicular to the path direction. The main catalyst for a single combustion chamber of the present invention is configured to purify exhaust gas to the greatest extent in the exhaust path. The exhaust path here refers to the path from the combustion chamber to the release port facing the atmosphere.

The main catalyst for a single combustion chamber of the present invention may be configured as a plurality of catalysts arranged in close proximity. Each sheet has a substrate and a catalyst substance. Here, the so-called proximity refers to a state where the distance between the sheets is shorter than the length in the path direction of each sheet. The composition of the plurality of substrates may be one type or plural types. The precious metal of the catalyst substance of the plurality of pieces of catalyst may be one kind or plural kinds. The composition of the carrier of the catalyst substance may be one kind or plural kinds. This modification can also be applied to the upstream sub-catalyst 200.

In the modified example 1-2 of the first embodiment, the upstream sub-catalyst 300 does not have a porous structure. However, the upstream sub-catalyst 300 may have a porous structure.

The arrangement positions of the main catalysts 39, 180, 116, and 154 are not limited to the positions shown in the drawings. Among them, the upstream end of the main catalyst is arranged more upstream than the upstream end of the muffler. Hereinafter, a specific modification example of the arrangement position of the main catalyst will be described.

In Embodiments 1 to 4, the main catalysts 39, 180, 116, and 154 are arranged in the exhaust pipes 34, 75, 111, and 149. However, the main catalyst may be disposed in the cylinder exhaust passage sections 31, 72, 108, and 146 of the cylinder sections 22, 63, 99, and 137.

In the first to fourth embodiments and the modified examples 1-1, 1-2, 2-1, 3-1, and 4-1, the downstream ends of the main catalysts 39, 180, 116, and 154 are located closer to the muffler 35, The upstream ends of 76, 112, and 150 are further upstream. However, for example, as shown in FIG. 35, the downstream end of the main catalyst 39 and the upstream end 435a of the muffler 435 may be at substantially the same position in the path direction. For example, as shown in FIG. 36, FIG. 37, and FIG. 38, the downstream end of the main catalyst 39 may be It is located further downstream than the upstream end 535a of the muffler 535.

At least a part of the main catalysts 39, 180, 116, and 154 may be disposed further forward than the crankshaft lines Cr1 to Cr4. In addition, at least a part of the main catalysts 39, 180, 116, and 154 may be disposed further behind the crankshaft lines Cr1 to Cr4.

When viewed from the left and right directions, at least a part of the main catalysts 39, 180, 116, and 154 may be disposed in front of the straight lines L2, L4, L6, and L8. In addition, at least a part of the main catalysts 39, 180, 116, and 154 may be arranged behind the straight lines L2, L4, L6, and L8 when viewed from the left and right directions.

The main catalyst 39 of the first embodiment is arranged at a position where the path length a1 + b1 is shorter than the path length d1 + e1. However, the main catalyst 39 may be disposed at a position where the path length a1 + b1 is longer than the path length d1 + e1. The path length a1 + b1 is the path length from the combustion chamber 29 to the upstream end of the main catalyst 39. The path length d1 + e1 is the path length from the downstream end of the autonomous catalyst 39 to the release outlet 35e. This modification can also be applied to the main catalysts 180, 116, and 154 of the second to fourth embodiments.

The upstream sub-catalyst 300 according to the modification 1-2 of the above embodiment is disposed further upstream than the main catalyst 39. Specifically, the upstream sub-catalyst 300 is provided in the upstream exhaust pipe 34a. However, the arrangement position of the upstream sub-catalyst (upstream sub-catalyst for a single combustion chamber) provided upstream of the main catalyst 39 is not limited to the upstream exhaust pipe 34a. The upstream sub-catalyst may be provided in the cylinder exhaust passage portion 31. The upstream sub-catalyst may be provided in the upstream passage portion 40 a of the catalyst unit 38. This modification can also be applied to the second to fourth embodiments.

A downstream sub-catalyst (a downstream sub-catalyst for a single combustion chamber) may also be provided downstream of the main catalyst. The downstream sub-catalyst may have the same configuration as the upstream sub-catalyst 300 according to the modification example 1-2 of the above embodiment. The downstream sub-catalyst may have a porous structure. For example, as shown in FIGS. 39 (c) and 39 (d), a downstream sub-catalyst 301 may be provided in the exhaust pipe 34. The downstream sub-catalyst may be provided in the muffler 35. In addition, the downstream sub-catalyst can also be set It is placed further downstream than the downstream end of the exhaust pipe 34. When the main catalyst is provided in the cylinder exhaust passage portion, the downstream sub-catalyst may be provided in the cylinder exhaust passage portion. These modified examples can also be applied to the second to fourth embodiments. When a downstream sub-catalyst is provided, an upstream sub-catalyst 300 may be provided upstream of the main catalyst. The downstream sub-catalyst is located further downstream than the main catalyst. Therefore, the degradation of the main catalyst progresses faster than the downstream sub-catalyst. However, even if the degradation of the main catalyst reaches a certain level, the purification performance of the exhaust gas can be maintained by the downstream sub-catalyst. Therefore, the initial performance of the locomotive with respect to exhaust purification can be maintained for a longer time.

When 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 greatest extent. The purification contribution of each of the main catalyst and the downstream sub-catalyst can be measured by the measurement method described in Variation 1-2. In the measurement method described in Variation 1-2, the "front catalyst" is set as the main catalyst, and the "post catalyst" is set as the "downstream sub-catalyst".

In the case where a downstream sub-catalyst is provided downstream of the main catalyst, the purification ability of the downstream sub-catalyst may be smaller than the purification ability of the main catalyst, or 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 greater than the exhaust gas purification rate when only the main catalyst is provided.

When a downstream sub-catalyst is provided downstream of the main catalyst, the main catalyst deteriorates faster than the downstream sub-catalyst. Therefore, if the cumulative travel distance becomes longer, the relationship between the purification contribution of the main catalyst and the downstream sub-catalyst may be reversed. The main catalyst for a single combustion chamber of the present invention purifies the exhaust gas discharged from the combustion chamber to the greatest extent in the exhaust path. This is the state before the reversal phenomenon described above. That is, this is a state where the cumulative travel distance does not reach a specific distance (for example, 1000 km).

In the present invention, the number of catalysts provided in a single-cylinder four-stroke engine unit may be one or plural. In the case of a plurality of catalysts, the catalyst that purifies exhaust gas discharged from the combustion chamber to the greatest extent in the exhaust path is equivalent to the single main combustion chamber for the present invention. catalyst. When there is one catalyst, the one catalyst is the main catalyst for a single combustion chamber of the present invention. An upstream sub-catalyst and a downstream sub-catalyst can also be provided upstream and downstream of the main catalyst. It is also possible to provide more than two upstream sub-catalysts upstream of the main catalyst. Moreover, two or more downstream sub-catalysts may be provided further downstream than the main catalyst.

The arrangement positions of the upstream oxygen detection members 36, 77, 113, and 151 (upstream oxygen detection members for a single combustion chamber) are not limited to the positions shown in the drawings. Among them, the upstream oxygen detecting members 36, 77, 113, and 151 are arranged more upstream than the main catalysts 39, 180, 116, and 154. Hereinafter, a specific modification example of the arrangement position of the upstream oxygen detection member will be described.

In the first to fourth embodiments, the upstream oxygen detecting members 36, 77, 113, and 151 are arranged in the exhaust pipes 34, 75, 111, 149, and 334. However, for example, as shown in FIG. 40, the upstream oxygen detection member 36 may be disposed in the cylinder exhaust passage portion 31.

In the third embodiment, the path length (h5) from the combustion chamber 106 to the upstream oxygen detection member 113 is longer than the path length (h6) from the upstream oxygen detection member 113 to the upstream end of the main catalyst 116. Among the above-mentioned first to fourth embodiments and their modifications, only the above-mentioned third embodiment has this arrangement. However, this arrangement can also be applied to the above-mentioned embodiments 1, 2, and 4.

The upstream oxygen detection member 36 of the above-mentioned modification 1-2 is disposed upstream of the upstream sub-catalyst 300. However, in a case where the upstream sub-catalyst 300 is provided upstream of the main catalyst 39, the arrangement position of the upstream oxygen detection member 36 may be the following position. For example, as shown in FIG. 39 (a), the upstream oxygen detection member 36 may be disposed further downstream than the upstream sub-catalyst 300. Further, for example, as shown in FIG. 39 (b), two upstream oxygen detection members 36A, 36B may be provided upstream and downstream of the upstream sub-catalyst 300. The upstream oxygen detection member 36A is provided upstream of the upstream sub-catalyst 300. The upstream oxygen detecting member 36B is disposed further downstream than the upstream sub-catalyst 300 and upstream from the main catalyst 39.

By arranging the upstream oxygen detecting means upstream of the upstream sub-catalyst, the following effects are obtained. The upstream oxygen detecting means can detect the oxygen concentration of the exhaust gas flowing into the upstream sub-catalyst. Therefore, by performing the combustion control based on the signal of the upstream oxygen detecting member, it is possible to improve Exhaust gas purification performance of upstream sub-catalyst.

In the first to fourth embodiments and the modified examples 1-1, 1-2, 2-1, 3-1, and 4-1, the upstream oxygen detection members 36, 77, 113, and 151 are placed on the main catalysts 39, 180, There is only one upstream of 116 and 154. However, the number of upstream oxygen detection members for a single combustion chamber provided in the vehicle of the present invention may be two or more.

The arrangement positions of the downstream oxygen detection members 37, 78, 114, and 152 (downstream oxygen detection members for a single combustion chamber) are not limited to the positions shown in the drawings. Among them, the downstream oxygen detecting members 37, 78, 114, and 152 are disposed further downstream than the main catalysts 39, 180, 116, and 154. Hereinafter, a specific modification example of the arrangement position of the downstream oxygen detection member will be described.

In the first to fourth embodiments, the downstream oxygen detecting members 37, 78, 114, and 152 are arranged in the exhaust pipes 34, 75, 111, 149, and 334. However, for example, as shown in FIG. 35, FIG. 36, FIG. 37, and FIG. 38, the downstream oxygen detecting member 37 may be configured to detect exhaust gas that is more downstream than the downstream ends of the exhaust pipes 434, 534, 1534, and 2534. Object. Hereinafter, the arrangement position of the downstream oxygen detection member 37 in FIGS. 35, 36, 37, and 38 will be described in detail.

First, FIG. 35 will be described. The muffler 435 of FIG. 35 has three expansion chambers 400, 401, and 402, and three pipes 403, 404, and 405. A third expansion chamber 402 is formed between the first expansion chamber 400 and the second expansion chamber 401. The downstream end of the catalyst unit 38 is arranged in the first expansion chamber 400. The first expansion chamber 400 and the second expansion chamber 401 communicate with each other through a first pipe 403. The second expansion chamber 401 and the third expansion chamber 402 communicate with each other through a second pipe 404. The upstream end of the third pipe 405 is arranged in the third expansion chamber 402. The third pipe 405 penetrates a side wall portion of the muffler 435. The third tube 405 has a release port 435e facing the atmosphere. The first pipe 403 is disposed near a side wall portion of the muffler 435. The detection portion (front end portion) of the downstream oxygen detection member 37 is disposed near the downstream end of the first tube 403. The exhaust gas discharged from the first pipe 403 is blown to the detection section of the downstream oxygen detection member 37.

Next, FIG. 36 will be described. The muffler 535 of FIG. 36 has three expansion chambers 500, 501, and 502, and three pipes 503, 504, and 505. Between the second expansion chamber 501 and the third expansion chamber 502 A first expansion chamber 500 is formed therebetween. The downstream end of the downstream exhaust pipe 534b is arranged in the first expansion chamber 500. The first expansion chamber 500 and the second expansion chamber 501 communicate with each other through a first pipe 503. The second expansion chamber 501 and the third expansion chamber 502 communicate with each other via a second pipe 504. The upstream end of the third pipe 505 is arranged in the third expansion chamber 502. The third pipe 505 penetrates a side wall portion of the muffler 535. The third tube 505 has a vent 535e facing the atmosphere. In the cross section of the main catalyst 39 orthogonal to the path direction, the main catalyst 39 is disposed at approximately the center of the muffler 535. The flow direction of the exhaust gas passing through the main catalyst 39 is set to the L direction. The downstream exhaust pipe 534b extends in a direction inclined with respect to the L direction. The downstream end of the downstream exhaust pipe 534b is arranged near the side wall portion of the muffler 535. The detection portion (front end portion) of the downstream oxygen detection member 37 is disposed near the downstream end of the downstream exhaust pipe 534b. The exhaust gas discharged from the downstream exhaust pipe 534b is blown to the detection section of the downstream oxygen detection member 37.

Next, FIG. 37 will be described. Components that are substantially the same as those in FIG. 36 are denoted by the same reference numerals, and detailed descriptions thereof are omitted. The downstream end of the downstream exhaust pipe 1534b is arranged in the first expansion chamber 500. The main catalyst 39 is disposed near a side wall portion of the muffler 535. The downstream end of the downstream exhaust pipe 1534b is also disposed near the side wall portion of the muffler 535. The detection portion (front end portion) of the downstream oxygen detection member 37 is disposed near the downstream end of the downstream exhaust pipe 1534b. The exhaust gas discharged from the downstream exhaust pipe 1534b is blown to the detection section of the downstream oxygen detection member 37.

Next, FIG. 38 will be described. Components that are substantially the same as those in FIG. 36 are denoted by the same reference numerals, and detailed descriptions thereof are omitted. The downstream end of the downstream exhaust pipe 2534b is arranged in the first expansion chamber 500. The downstream oxygen detecting means 37 is arranged in the third pipe 505.

When a downstream sub-catalyst 301 is provided downstream of the main catalyst 39, the arrangement position of the downstream oxygen detection member may be any of the following two positions. For example, as shown in FIG. 39 (c), the downstream oxygen detection member 37 may be provided further downstream than the main catalyst 39 and more upstream than the downstream sub-catalyst 301. Further, for example, as shown in FIG. 39 (d), the downstream oxygen detecting member 37 may be provided further downstream than the downstream sub-catalyst 301. Further, a downstream oxygen detecting means may be provided upstream and downstream of the downstream sub-catalyst 301, respectively.

In the first to fourth embodiments, only one downstream oxygen detecting member 37, 78, 114, and 152 is disposed upstream of the main catalysts 39, 180, 116, and 154. However, the number of downstream oxygen detection members for a single combustion chamber provided in the vehicle of the present invention may be two or more.

In the first to fourth embodiments described above, the purification ability of the main catalyst is determined based on the signal of the downstream oxygen detecting means. However, the method of using the signal of the downstream oxygen detecting means is not limited to this. The electronic control unit (control device) can also determine the purification ability of the main catalyst based on the signals of the upstream oxygen detection component and the downstream oxygen detection component. The electronic control unit (control device) may perform combustion control based on signals from the upstream oxygen detection means and the downstream oxygen detection means.

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

An example of a specific method for performing combustion control based on signals from the upstream oxygen detection means and the downstream oxygen detection means will be described. First, as in the first embodiment, the basic fuel injection amount is corrected based on a signal from the upstream oxygen detecting means 37, and fuel is injected from the injector 48. Exhaust gas generated by the combustion of the fuel is detected by a downstream oxygen detection member. Then, the fuel injection amount is corrected based on a signal from the downstream oxygen detecting means. This makes it possible to further reduce the deviation of the air-fuel ratio of the mixed gas with respect to the target air-fuel ratio.

By using the signals of two oxygen detection members arranged upstream and downstream of the main catalyst, the actual purification status of the main catalyst can be grasped. Therefore, by using two oxygen detection The signals from the components are used for combustion control, which can improve the accuracy of combustion control. Thereby, the progress of the deterioration of the main catalyst can be slowed down. As a result, the initial performance of the locomotive regarding the exhaust purification performance can be maintained for a longer time.

In the first embodiment described above, the ignition timing and the fuel injection amount are controlled based on the signal from the upstream oxygen detecting means 36. This configuration is also the same in the second to fourth embodiments. However, the control processing based on the signal of the upstream oxygen detection member 36 is not particularly limited, and may be only one of the ignition timing and the fuel injection amount. The control processing based on the signal from the upstream oxygen detection means 36 may include control processing other than the above.

The downstream oxygen detecting members 37, 78, 114, and 152 may also have a built-in heater. When the detection sections of the downstream oxygen detection members 37, 78, 114, and 152 are heated to a high temperature and become activated, they can detect the oxygen concentration. Therefore, if the downstream oxygen detection members 37, 78, 114, and 152 have built-in heaters, the detection section is heated by the heater at the same time as the operation is started, whereby the oxygen detection can be started as soon as possible. In addition, the upstream oxygen detection members 36, 77, 113, and 151 may have built-in heaters.

At least a part of the exhaust pipe upstream of the main catalyst may include multiple pipes. The multiple tube has an inner tube and at least one outer tube covering the inner tube. FIG. 41 shows an example in which the exhaust pipe 634 includes a double pipe 600 at least in a part upstream of the main catalyst. The double tube 600 includes an inner tube 601 and an outer tube 602 covering the inner tube 601. In FIG. 41, only two ends of the inner tube 601 and the outer tube 602 are in contact with each other. The inner tube and the outer tube of the multiple tube may also contact at portions other than the two end portions. For example, the inner tube and the outer tube may be in contact with each other at the bent portion. The contact area is preferably smaller than the non-contact area. In addition, the inner tube and the outer tube may be integrally contacted. By providing multiple pipes, it is possible to suppress a decrease in the temperature of the exhaust gas. This makes it possible to increase the temperature of the upstream oxygen detection member to the activation temperature more quickly when the engine is started. Therefore, the detection accuracy of the upstream oxygen detection member can be improved. Thereby, the combustion control based on the signal of the upstream oxygen detection member can be performed more accurately. As a result, the exhaust gas purification performance of the main catalyst can be further improved. In addition, by improving the accuracy of combustion control, the progress of deterioration of the main catalyst can be slowed. Therefore, the initial performance of the locomotive with respect to exhaust purification can be maintained for a longer time.

For example, as shown in FIG. 42, at least a part of the outer surface of the catalyst arrangement passage portion 40 b may be covered by the catalyst protector 700. The catalyst protector 700 is formed in a substantially cylindrical shape. By providing a catalyst protector, the temperature of the main catalyst 39 can be increased more quickly. Therefore, the exhaust gas purification performance of the main catalyst 39 can be improved. This modification can also be applied to the second to fourth embodiments.

In Embodiments 1 to 4, the gas flowing through the exhaust paths 41, 182, 118, and 156 when the engine is driven is only the exhaust gas discharged from the combustion chambers 29, 70, 106, and 144. However, the single-cylinder four-stroke engine unit of the present invention may be provided with a secondary air supply mechanism that supplies air to the exhaust path. The specific configuration of the secondary air supply mechanism is a known configuration. The secondary air supply mechanism may be configured to forcibly supply air to the exhaust path by an air pump. The secondary air supply mechanism may be configured to draw air into the exhaust path by the negative pressure of the exhaust path. In this case, the secondary air supply mechanism 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 a secondary air supply mechanism is provided, the arrangement position of the upstream oxygen detecting member may be set more upstream or downstream than the position where the air flows in.

In Embodiments 1 to 4, the injectors are used to supply fuel to the combustion chambers 29, 70, 106, and 144. The fuel supply device that supplies fuel to the combustion chamber is not limited to an injector. For example, a fuel supply device that supplies fuel to the combustion chamber by a negative pressure may be provided.

In the first to fourth embodiments, only one exhaust port 31a, 72a, 108a, 146a is provided in one combustion chamber 29, 70, 106, 144. However, a plurality of exhaust ports may be provided in one combustion chamber. For example, a case where a variable valve mechanism is provided corresponds to this modification. Among them, the exhaust path extending from the plurality of exhaust ports is gathered more upstream than the main catalyst. The exhaust path extending from the plurality of exhaust ports is preferably assembled at the cylinder portion.

The combustion chamber of the present invention may be configured as 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 auxiliary combustion chamber.

In the first to fourth embodiments and the modified examples 1-2, the combustion chambers 29, 70, 106, 144 as a whole is located more forward than the crankshaft lines Cr1, Cr2, Cr3, and Cr4. However, the combustion chamber of the present invention only needs to be located at least partially forward of the crankshaft line. That is, a part of the combustion chamber may be located further behind the crankshaft line. This modification can be realized when the cylinder axis extends in the vertical direction.

In Embodiments 1 to 4 and Modifications 1-2 described above, the crankcase bodies 23, 64, 100, and 138 and the cylinder blocks 24, 65, 101, and 139 are separate members. However, the crankcase body and the cylinder block may be integrally formed. In the first to fourth embodiments and the modified examples 1-2, the cylinder blocks 24, 65, 101, 139, the cylinder heads 25, 66, 102, 140, and the head covers 26, 67, 103, and 141 are separate members. . However, any two or three of the cylinder block, the cylinder head, and the head cover may be integrally formed.

In the first to fourth embodiments and the modified examples 1-2, the locomotive is exemplified as a vehicle including a single-cylinder four-stroke engine unit. However, the vehicle of the present invention may be any vehicle as long as it is a vehicle that is moved by the power of a single-cylinder four-stroke engine unit. The vehicle of the present invention may be a straddle type vehicle other than a locomotive. The so-called straddle-type vehicles refer to all vehicles that riders ride in a saddle-like state. Straddle-type vehicles include locomotives, three-wheeled locomotives, four-wheeled off-road vehicles (ATV: All Terrain Vehicle), water locomotives, and snowmobiles. The vehicle of the present invention may not be a straddle type vehicle. In addition, the vehicle of the present invention may be a rider but not a rider. In addition, the vehicle of the present invention may be a person who can drive without carrying a person. In such cases, the so-called forward direction of the vehicle refers to the forward direction of the vehicle.

The single-cylinder four-stroke engine units 93 and 132 of the third and fourth embodiments described above are unit swing type. The engine bodies 94 and 133 are provided so as to be swingable with respect to the vehicle body frames 81 and 121. Therefore, the position of the crankshaft lines Cr3 and Cr4 relative to the main catalysts 116 and 154 changes depending on the driving conditions. In this specification and the present invention, the so-called main catalyst is located in front of the crankshaft line means that the main catalyst is located in front of the crankshaft when the engine body is in any position within the movable range. The positional relationship other than this can be achieved in any one of the movable ranges of the engine body.

In this specification and the present invention, the upstream end of the main catalyst refers to the end with the shortest path length from the combustion chamber in the main catalyst. The so-called downstream end of the main catalyst refers to the end with the longest path length from the combustion chamber in the main catalyst. The same definitions apply to the upstream and downstream ends of elements other than the main catalyst.

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

In this specification and the present invention, the path length of the exhaust path refers to the path length of the middle line of the exhaust path. The path length of the expansion chamber of the muffler refers to the length of the path that connects the center of the inlet of the expansion chamber and the center of the outlet of the expansion chamber to 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 this specification, the expression of the area of the cross section of the passage portion orthogonal to the direction of the path is used. In this specification and the present invention, the expression of the area of the cross section of the passage portion orthogonal to the flow direction of the exhaust gas is used. The cross-sectional area of the passage portion here may be the area of the inner peripheral surface of the passage portion, or the area of the outer peripheral surface of the passage portion.

In the present specification and the present invention, the term “member or straight line extending along the A direction” does not merely mean that the member or straight line is arranged parallel to the A direction. The so-called member or straight line extends along the A direction, and includes a case where the member or straight line is inclined within a range of ± 45 ° with respect to the A direction. Moreover, the A direction does not mean a specific direction. The A direction can be replaced with a horizontal direction or a front-back direction.

The crankcase bodies 23, 64, 100, and 138 in this specification correspond to the crankcase portions 18, 61, 95, and 135 in the description of the basic application of this case, respectively. The cylinder blocks 24, 65, 101, and 139 in this specification correspond to the cylinder sections 24, 62, 96, and 136 in the description of the above-mentioned basic application, respectively. The engine bodies 20, 61, 94, and 133 in this manual are equivalent to Engines 20, 60, 93, 131 in the description of the above-mentioned basic application. The cylinder exhaust passage portion 31 in this specification corresponds to the passage portion forming the exhaust passage P2 in the description of the above-mentioned basic application.

The present invention also includes all embodiments including equivalent elements, corrections, deletions, combinations (such as feature combinations across various embodiments), improvements, and / or changes that can be identified by the industry based on the disclosure of this specification. Limitations of the scope of a patent application should be broadly understood based on the terms used in the scope of the patent application. The matters limiting the scope of the patent application should not be limited to the embodiments described in the description or the embodiment of the case. This embodiment should be understood as non-exclusive. For example, in this specification, the terms "better" and "good" are non-exclusive and mean "better but not limited to this" and "good but not limited to this."

1‧‧‧ Locomotive (vehicle)

2‧‧‧ body frame

3‧‧‧ head tube

4‧‧‧ main frame

4a‧‧‧ bracket

4b‧‧‧bolt

5‧‧‧ seat rail

6‧‧‧ Fork

8‧‧‧ front wheel

8a‧‧‧ axle

13‧‧‧ rear shock absorption unit

14‧‧‧ hind arm

14a‧‧‧ Pivot

15‧‧‧ rear wheel

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‧‧‧Air inlet pipe

34‧‧‧Exhaust pipe

35‧‧‧ Silencer

35a‧‧‧upstream end of silencer

35e‧‧‧release

36‧‧‧Upstream oxygen detection component

37‧‧‧downstream oxygen detection component

38‧‧‧ catalyst unit

39‧‧‧Main catalyst (main catalyst for single combustion chamber)

40‧‧‧shell

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

Cy1‧‧‧ cylinder axis (center line of cylinder hole)

F‧‧‧ before

L1‧‧‧A straight line extending parallel to the vertical direction through the crankshaft line

L2‧‧‧A straight line orthogonal to the crankshaft line and cylinder axis

After Re‧‧‧

Claims (23)

A vehicle is characterized in that it is equipped with a single-cylinder four-stroke engine unit. The single-cylinder four-stroke engine unit includes: an engine body having a cylinder portion formed with a combustion chamber; A single cylinder exhaust passage for a single combustion chamber through which exhaust gas discharged from a combustion chamber flows; a single exhaust pipe for a single combustion chamber connected to the downstream end of the single cylinder exhaust passage for the single combustion chamber; and a single combustion chamber The muffler has a release port facing the atmosphere, and is connected to the exhaust pipe for the single combustion chamber so that the exhaust gas flowing in from the downstream end of the exhaust pipe for the single combustion chamber flows to the exhaust port to reduce the generation of the exhaust gas. Sound; a main catalyst for a single combustion chamber, which is arranged in the exhaust passage section of the cylinder for the single combustion chamber or in the exhaust pipe for the single combustion chamber, and whose upstream end is disposed upstream of the muffler for the single combustion chamber The end is more upstream of the exhaust gas flow direction, and the exhaust path from the above one combustion chamber to the above-mentioned discharge port is purified to the greatest extent. Exhaust gas exhausted from the chamber; upstream oxygen detection means for a single combustion chamber, which is arranged in the exhaust path of the single combustion chamber cylinder or the exhaust pipe for the single combustion chamber, and is located closer to the exhaust gas than the main catalyst for the single combustion chamber. Upstream of the direction, the oxygen concentration in the exhaust gas is detected; the downstream oxygen detection member for the single combustion chamber is located in the cylinder exhaust passage of the single combustion chamber, the exhaust pipe for the single combustion chamber, or the muffler for the single combustion chamber. It is located downstream of the flow direction of the exhaust gas than the main catalyst for the single combustion chamber, and detects the oxygen concentration in the exhaust gas; and a control device that processes the signal of the upstream oxygen detection member for the single combustion chamber. And the signal of the downstream oxygen detecting member for the single combustion chamber. For example, the vehicle of claim 1, wherein the engine body has a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, and at least a part of the one combustion chamber of the cylinder portion is disposed closer to the centerline than the centerline of the crankshaft. The front and rear directions of the vehicle, the release port of the single-combustion-chamber muffler is disposed behind the vehicle in the front-rear direction, and at least a part of the single-combustion-chamber main catalyst is disposed more The centerline of the crankshaft is further in front of the vehicle. The vehicle of claim 2, wherein the engine body has a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, the cylinder portion of the engine body has a cylinder hole in which a piston is arranged, and the one combustion chamber of the cylinder portion At least a part of the muffler for the single combustion chamber is located at the front side of the vehicle in the front-rear direction of the crankshaft. And when the vehicle is viewed from the left and right directions, at least a part of the single combustion chamber main catalyst is located in a front-rear direction of the vehicle on a straight line orthogonal to the center line of the cylinder bore and orthogonal to the center line of the crankshaft. The vehicle of claim 2, wherein the engine body has a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, the cylinder portion of the engine body has a cylinder hole in which a piston is arranged, and the one combustion chamber of the cylinder portion At least a part of the muffler for the single combustion chamber is located at the front side of the vehicle in the front-rear direction of the crankshaft. And When the vehicle is viewed from the left and right directions, at least a part of the single-combustion-chamber main catalyst is located behind the vehicle in a front-rear direction on a straight line orthogonal to the center line of the cylinder bore and orthogonal to the center line of the crankshaft. For example, the vehicle of claim 1, wherein the engine body has a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, the cylinder portion of the engine body has a cylinder hole in which a piston is disposed, and the one combustion chamber of the cylinder portion At least a part of the muffler for the single combustion chamber is located at the front side of the vehicle in the front-rear direction of the crankshaft. And when the vehicle is viewed from the left and right directions, at least a part of the single-combustion-chamber main catalyst is located behind the vehicle in a front-rear direction on a straight line orthogonal to the centerline of the cylinder bore and orthogonal to the centerline of the crankshaft. For example, the vehicle of claim 5, wherein the engine body has a crankcase portion including a crankshaft extending in the left-right direction of the vehicle, and at least a part of the one combustion chamber of the cylinder portion is disposed closer to the center line than the centerline of the crankshaft. The front and rear directions of the vehicle, the release port of the single-combustion-chamber muffler is disposed behind the vehicle in the front-rear direction, and at least a part of the single-combustion-chamber main catalyst is disposed more The centerline of the crankshaft is further behind the front-rear direction of the vehicle. The vehicle according to any one of claims 2 to 6, wherein the main catalyst for the single combustion chamber is arranged at a path from the one combustion chamber to the upstream end of the main catalyst for the single combustion chamber, and is shorter than the distance from the single combustion The path from the downstream end of the chamber main catalyst to the above-mentioned release port is long. As in the vehicle of claim 1, wherein the main catalyst for a single combustion chamber is arranged in The path from the one combustion chamber to the upstream end of the single-combustion-chamber main catalyst is longer than the position where the path from the downstream end of the single-combustion-chamber main catalyst to the release port is long. For the vehicle of claim 8, wherein the single-combustion-chamber main catalyst is located at a path from the one combustion chamber to the upstream end of the single-combustion-chamber main catalyst, and is shorter than the downstream of the single-combustion-chamber main catalyst. The path from the end to the downstream end of the single combustion chamber exhaust pipe is long. For example, the vehicle of claim 8, wherein the single-combustion-chamber main catalyst is arranged at a path from the one combustion chamber to the upstream end of the single-combustion main catalyst, and is longer than the downstream end of the single-combustion main-catalyst. The long path to the downstream end of the single combustion chamber exhaust pipe. For the vehicle according to any one of claims 6, 8 to 10, wherein the upstream oxygen detection member for the single combustion chamber is arranged at a path from the one combustion chamber to the upstream end of the upstream oxygen detection member for the single combustion chamber, A position shorter than the path from the upstream oxygen detection member for the single combustion chamber to the upstream end of the main catalyst for the single combustion chamber. For the vehicle according to any one of claims 6, 8 to 10, wherein the upstream oxygen detection member for the single combustion chamber is arranged at a path from the one combustion chamber to the upstream end of the upstream oxygen detection member for the single combustion chamber, The position is longer than the path from the upstream oxygen detection member for the single combustion chamber to the upstream end of the main catalyst for the single combustion chamber. The vehicle according to any one of claims 6, 8 to 10, wherein the exhaust pipe for a single combustion chamber has a catalyst arrangement passage section in which the main catalyst for the single combustion chamber is disposed, and an upstream end connected to the catalyst arrangement passage section. The upstream passage portion, and at least a part of the upstream passage portion has an area of a cross section orthogonal to the flow direction of the exhaust gas that is smaller than a cross section of the catalyst arrangement passage portion orthogonal to the flow direction of the exhaust gas The area of the face. The vehicle according to any one of claims 6, 8 to 10, wherein at least a part of the exhaust pipe for the single combustion chamber that is located upstream of the exhaust gas flow direction than the main catalyst for the single combustion chamber includes an inner pipe and covers the above. Multiple tubes of at least one outer tube of inner tube. The vehicle according to any one of claims 6, 8 to 10, wherein the exhaust pipe for a single combustion chamber has a catalyst arrangement passage section for disposing the main catalyst for a single combustion chamber, and the single-cylinder four-stroke engine unit includes: catalyst protection A device covering at least a part of an outer surface of the catalyst disposing passage portion. The vehicle according to any one of claims 6, 8 to 10, wherein the single-cylinder four-stroke engine unit is provided with an upstream sub-catalyst for a single combustion chamber, and the upstream sub-catalyst for the single combustion chamber is in an exhaust path of the single-combustion cylinder cylinder. The inside or the exhaust pipe for the single combustion chamber is disposed upstream of the exhaust gas flow direction than the main catalyst for the single combustion chamber to purify the exhaust gas. The vehicle according to claim 16, wherein the above-mentioned single-combustion-chamber upstream oxygen detection member is arranged upstream of the exhaust gas flowing direction than the above-mentioned single-combustion-chamber upstream sub-catalyst. The vehicle according to any one of claims 6, 8 to 10, wherein the single-cylinder four-stroke engine unit is provided with a downstream sub-catalyst for a single combustion chamber, and the downstream sub-catalyst for the single combustion chamber is in an exhaust pipe for the single combustion chamber Or the muffler for the single combustion chamber is arranged in the downstream of the exhaust gas flow direction than the main catalyst for the single combustion chamber to purify the exhaust gas. For example, the vehicle of claim 18, wherein the above-mentioned single-combustion-chamber downstream oxygen detecting member is disposed downstream of the exhaust gas flow direction than the single-combustion-chamber main catalyst, and is disposed closer to the single-combustion-chamber downstream subcatalyst. Exhaust gas flow Direction upstream. The vehicle according to claim 18, wherein the single-combustion-chamber downstream oxygen detection member is disposed further downstream than the single-combustion-chamber downstream sub-catalyst in the direction of exhaust gas flow. For example, the vehicle according to any one of claims 6, 8 to 10, wherein the control device determines the purification capability of the main catalyst for the single combustion chamber based on a signal from the downstream oxygen detection member for the single combustion chamber, and has a notification device, When the control device determines that the purification capability of the main catalyst for a single combustion chamber has been reduced to a specific level, the notification device notifies. The vehicle according to any one of claims 6, 8 to 10, wherein the single-cylinder four-stroke engine unit includes a fuel supply device for supplying fuel to the one combustion chamber, and the control device is based on the upstream oxygen detection means for the single combustion chamber. The signal and the signal of the downstream oxygen detection member for the single combustion chamber control the amount of fuel supplied from the fuel supply device to the one combustion chamber. A single-cylinder four-stroke engine unit is characterized in that it is mounted on the vehicle of claim 1 and includes an engine body having a cylinder portion formed with a combustion chamber and a combustion chamber for the combustion. A single cylinder exhaust path for a single combustion chamber through which exhaust gas from a chamber flows; a single exhaust pipe for a single combustion chamber connected to the downstream end of the exhaust path section for the single cylinder for a combustion chamber; a silencer for a single combustion chamber Device having a release port facing the atmosphere, connected to the exhaust pipe for the single combustion chamber and downstream from the exhaust pipe for the single combustion chamber The inflowing exhaust gas flows to the above-mentioned release port to reduce the sound generated by the exhaust gas; the main catalyst for a single combustion chamber is arranged in the exhaust passage portion of the cylinder for the single combustion chamber or the exhaust pipe for the single combustion chamber, And its upstream end is arranged upstream of the exhaust gas flow direction than the upstream end of the single combustion chamber muffler, and the exhaust path from the one combustion chamber to the release outlet is purified to the greatest extent and discharged from the one combustion chamber. Exhaust gas; upstream oxygen detection member for single combustion chamber, which is arranged in the exhaust passage of the single combustion chamber cylinder or the exhaust pipe for the single combustion chamber in a direction closer to the exhaust gas flow direction than the main catalyst for the single combustion chamber. The upstream detects the oxygen concentration in the exhaust gas; the downstream oxygen detection means for a single combustion chamber is arranged in the exhaust passage of the cylinder for the single combustion chamber, the exhaust pipe for the single combustion chamber, or the muffler for the single combustion chamber. It is closer to the downstream of the exhaust gas flow direction than the main catalyst for a single combustion chamber, and detects the oxygen concentration in the exhaust gas; and a control device, where It said single combustion chamber upstream signal of an oxygen detection means and said signal a single combustion chamber downstream oxygen detection means purposes.