CN109236440B

CN109236440B - Exhaust gas sensor arrangement structure and motorcycle

Info

Publication number: CN109236440B
Application number: CN201810677707.4A
Authority: CN
Inventors: 秋田佳克
Original assignee: Suzuki Motor Corp
Current assignee: Suzuki Motor Corp
Priority date: 2017-07-11
Filing date: 2018-06-27
Publication date: 2021-02-02
Anticipated expiration: 2038-06-27
Also published as: CN109236440A; JP6922492B2; JP2019015277A

Abstract

The invention provides an exhaust gas sensor arrangement structure and a motorcycle. The present invention can improve exhaust gas purification performance and can dispose an exhaust gas sensor without impairing the detection accuracy of exhaust gas components. The present invention is provided with: an engine (2) having a cylinder (21a) and a cylinder head (21b) disposed in front of a crankcase (20); an exhaust pipe (6) attached to an exhaust port (22) of the cylinder head; a catalyst device (50) disposed in the middle of the exhaust pipe; and an upstream sensor (8) attached to the exhaust pipe on the upstream side of the catalytic device. The axis of the cylinder is oriented in a substantially horizontal direction, and an exhaust port is provided on the lower side of the cylinder head. The exhaust pipe has a first pipe distribution portion (62) extending in the vehicle width direction below the cylinder head. The catalyst device is disposed in the first pipe portion so that the axial direction thereof faces the vehicle width direction.

Description

Exhaust gas sensor arrangement structure and motorcycle

Technical Field

The present invention relates to an arrangement structure of an exhaust gas sensor and a motorcycle.

Background

With the recent exhaust gas restriction, in an exhaust system of an engine for a vehicle, monitoring of a deterioration condition of a catalytic device that purifies exhaust gas is required. For example, in patent document 1, an oxygen sensor for detecting the oxygen concentration of the exhaust gas is provided on the downstream side of the catalyst device.

Specifically, in patent document 1, the interior of the muffler is divided by a plurality of partition walls (partitions) to form a plurality of expansion chambers. A catalytic device is disposed inside the muffler, and a downstream end of the catalytic device extends to protrude into a predetermined expansion chamber. Further, the expansion chambers and the catalytic devices are connected to a plurality of exhaust pipes. The oxygen sensor is installed to penetrate through an exhaust pipe on the downstream side of the catalytic device.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016 and 160914

Problems to be solved by the invention

However, in patent document 1, a part of the outer wall of the muffler is recessed in order to dispose the oxygen sensor. Accordingly, the volume of the expansion chamber is reduced in accordance with the amount of recess of the outer wall, and the silencing effect of the exhaust gas may be reduced. Further, since the temperature of the exhaust gas decreases as the exhaust gas goes downstream, there is a possibility that the oxygen concentration of the exhaust gas cannot be appropriately detected while ensuring the exhaust gas purification performance from the viewpoint of activating the temperature of the catalyst device or the oxygen sensor.

Disclosure of Invention

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an arrangement structure of an exhaust gas sensor and a motorcycle, in which the exhaust gas sensor can be arranged with improved exhaust gas purification performance without impairing detection accuracy of exhaust gas components.

Means for solving the problems

An arrangement structure of an exhaust gas sensor according to an aspect of the present invention includes: an engine having a cylinder and a cylinder head disposed in front of a crankcase; an exhaust pipe attached to an exhaust port of the cylinder head; a catalyst device disposed in the middle of the exhaust pipe; and a first exhaust gas sensor that is disposed upstream of the catalyst device and that is attached to the exhaust pipe, wherein an axis of the cylinder is oriented in a substantially horizontal direction, the exhaust port is provided below the cylinder head, the exhaust pipe has a first pipe portion that extends in a vehicle width direction below the cylinder head, and the catalyst device is disposed in the first pipe portion so that an axial direction thereof is oriented in the vehicle width direction.

Effects of the invention

According to the present invention, the exhaust gas sensor can be disposed without impairing the detection accuracy of the exhaust gas component while improving the exhaust gas purification performance.

Drawings

Fig. 1 is a right side view showing a schematic configuration of a motorcycle to which the arrangement configuration of the exhaust gas sensor according to the present embodiment is applied.

Fig. 2 is a right side view showing the engine peripheral structure of the motorcycle shown in fig. 1.

Fig. 3 is a view in which a part of the structure is omitted from fig. 2.

Fig. 4 is a bottom view of the peripheral structure of the engine shown in fig. 2.

Fig. 5 is a diagram in which a part of the structure is omitted from fig. 4.

Fig. 6 is a front view of the peripheral structure of the engine shown in fig. 2.

Fig. 7 is a perspective view of the exhaust system of the present embodiment.

Fig. 8 is a plan view of the periphery of the exhaust pipe of the present embodiment.

Fig. 9 is a view from direction a of fig. 8.

Description of the symbols

1 motorcycle

2 engines

20 crankcase

21a cylinder

21b cylinder head

22 exhaust port

3 vehicle body frame (frame)

4 Engine suspension bracket (bracket)

50 catalytic device

6 exhaust pipe (exhaust pipe)

61 first bend

62 first piping part

63 second bend

64 second piping part

8 upstream side sensor (first exhaust gas sensor)

9 downstream side sensor (second exhaust gas sensor)

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, an example in which the arrangement structure of the exhaust gas sensor according to the present invention is applied to a scooter type motorcycle will be described, but the application object is not limited thereto and can be changed. For example, the arrangement structure of the exhaust gas sensor according to the present invention may be applied to other types of motorcycles, off-road type motor tricycles, motor quadricycles, and the like. Further, the directions are indicated by an arrow FR, a vehicle front direction, an arrow RE, a vehicle rear direction, an arrow UP, a vehicle lower direction, an arrow L, and a vehicle right direction, respectively. In the following drawings, for convenience of explanation, some of the structures are omitted.

A schematic structure of the motorcycle according to the present embodiment will be described with reference to fig. 1. Fig. 1 is a right side view showing a schematic configuration of a motorcycle to which the arrangement configuration of the exhaust gas sensor according to the present embodiment is applied.

As shown in fig. 1, a scooter type motorcycle 1 is configured such that an engine 2 is suspended from a body frame 3 (see fig. 2) of an elbow beam type. The engine 2 is constituted by, for example, a single cylinder engine. In particular, in the present embodiment, a unit swing type engine in which the engine 2, a transmission (a CVT unit or the like described later), and a transmission mechanism to the rear wheel 26 are integrated with a swing arm is used.

Various covers as exterior vehicle body members are attached to the vehicle body frame and the engine 2. Specifically, a leg shield 11 for protecting the surroundings of the legs of the driver in front is provided on the vehicle front side. A center frame cover 12 is provided behind the leg shield 11. A footboard 13 extending rearward is provided at the lower end of the center frame cover 12. A side frame cover 14 that covers the side of the vehicle is provided behind the step 13.

The front fork 15 is rotatably supported at the vehicle front side via a steering shaft (not shown). A handlebar 17 for steering the front wheel 16 is provided above the front fork 15. The front wheel 16 is rotatably supported by a lower portion of the front fork 15.

A seat 18 is provided on the upper side of the side frame cover 14. A tailgate 19 is provided at the rear of the side frame cover 14. The engine 2, which is an internal combustion engine, is disposed from the inside to the rear of the side frame cover 14.

The engine 2 extends forward and rearward behind the step plate 13. The front end portion of the engine 2 is coupled to the vehicle body frame 3, and the entire engine 2 is configured to be swingable up and down about the coupling portion as a fulcrum. The rear wheel 26 is rotatably provided at the rear end of the engine 2.

An exhaust pipe 6 and a muffler 7 are connected to an exhaust port 22 (see fig. 4 and 5) of the engine 2 as an exhaust system. The exhaust pipe 6 extends rearward below the engine 2. The muffler 7 is connected to the rear end of the exhaust pipe 6 and is disposed to overlap the rear wheel 26 when viewed from the side. A muffler cover 70 is provided on the right side surface of the muffler 7.

Next, the engine and its peripheral structure of the present embodiment will be described with reference to fig. 2 to 6. Fig. 2 is a right side view showing the engine peripheral structure of the motorcycle shown in fig. 1. Fig. 3 is a view in which a part of the structure is omitted from fig. 2. Fig. 4 is a bottom view of the peripheral structure of the engine shown in fig. 2. Fig. 5 is a diagram in which a part of the structure is omitted from fig. 4. Fig. 6 is a front view of the peripheral structure of the engine shown in fig. 2.

As described above, the engine 2 of the present embodiment is a unit swing type engine used for the scooter type motorcycle 1 (see fig. 1). As shown in fig. 2 to 6, the engine 2 is swingably suspended to the vehicle body frame 3 via an engine mount 4.

The vehicle body frame 3 includes: a lower frame 30 extending forward and backward below the footrest 13 (see fig. 1); a pair of side frames 31 extending rearward and upward from the rear end of the lower frame 30; and a coupling frame 32 that couples the lower frame 30 and the pair of side frames 31.

The lower frame 30 extends forward and rearward in the front-lower direction of the engine 2 so as to pass through a substantially center in the vehicle width direction (on a center line C1 of a cylinder described later). The connecting frame 32 is connected to a rear end of the lower frame 30 and extends in the vehicle width direction (left-right direction). The lower ends of the pair of side frames 31 are connected to the left and right ends of the connecting frame 32.

The engine 2 is configured such that a cylinder 21a, a cylinder head 21b, and a head cover 21c are disposed in this order in front of a crankcase 20 that houses various components such as a crankshaft (not shown). The cylinder 21a is disposed so as to incline toward the front side with its axis directed in a substantially horizontal direction.

Specifically, the front side of the axis of the cylinder 21a (the side of the cylinder head cover 21 c) is directed slightly higher than the horizontal direction (substantially horizontal direction). That is, the horizontal direction of the present embodiment means not only a completely horizontal direction but also a concept having a predetermined width within a range not departing from the gist of the present invention.

The cylinder 21a is mounted to the front of the crankcase 20. A cylindrical bore (combustion chamber) (neither shown) for accommodating a piston is formed inside the cylinder 21 a. The cylinder head 21b is mounted to the front of the cylinder 21 a. An intake port (not shown) and an exhaust port 22 that communicate with the combustion chamber are formed in the cylinder head 21 b. The exhaust port 22 is provided on the lower side (lower surface side) of the cylinder head 21b, and the exhaust port 22 has an axial direction in the vertical direction.

The cylinder head cover 21c is attached to the front portion of the cylinder head 21b, and functions as a cover for the cylinder head 21 b. An intake/exhaust valve (not shown) and a valve mechanism (not shown) that opens and closes the intake/exhaust valve are housed in the cylinder head 21b and the cylinder head cover 21 c.

The crankcase 20 is configured by connecting a left case 23 and a right case 24, which are divided left and right, by bolts or the like. The joint surface of the left case 23 and the right case 24 passes through the axial center of the cylinder. In fig. 4, a straight line passing through the axial center of the cylinder (the joint surface between the left case 23 and the right case 24) is indicated by a center line C1. A crankshaft is housed in the crankcase 20, and the crankshaft is disposed so that the axial direction is horizontal in the vehicle width direction. In fig. 4, the center of the crankshaft is represented by a center line C2.

Specifically, the left case 23 extends rearward, and a rear wheel 26 is rotatably mounted to a rear end of the left case 23 via a gear case 27. That is, the left case 23 constitutes a swing arm that cantileverly supports the rear wheel 26. The left case 23 has an open left side surface, and a CVT unit (not shown) as a transmission is housed inside the left case 23. The CVT unit is constituted by a so-called belt-type continuously variable transmission, and realizes speed change by changing the winding radius of a belt. A hood 25 is attached to the left side of the left case 23, and the opening of the left case 23 is closed. The gear case 27 houses a reduction gear (not shown).

Engine mount portions

23a and 24a for coupling (suspending) the engine 2 to the vehicle body frame 3 are formed in the left case 23 and the right case 24. The

engine mount portions

23a and 24a are formed to protrude forward from the lower surfaces of the left and

right cases

23 and 24 toward the lower side of the cylinder 21 a. The

engine mount portions

23a, 24a are arranged in parallel in the vehicle width direction and face each other with a center line C1 therebetween. The tip ends of the

engine mount portions

23a, 24a constitute a swing shaft (pivot portion) of the engine 2.

A pair of engine mount brackets 4 are attached to the

engine mount portions

23a, 24 a. The engine mount 4 extends forward from the distal ends of the

engine mount portions

23a, 24 a. The pair of engine mount brackets 4 are disposed below the cylinder head 21b in parallel in the vehicle width direction so as to correspond to the

engine mount portions

23a and 24a, and face each other with a center line C1 interposed therebetween.

The

engine mount portions

23a, 24a and the rear end portion of the engine mount 4 are swingably coupled by a shaft portion 40 extending in the vehicle width direction. The tip end portion of the engine mount 4 is fixed to the connecting frame 32 via a mount pipe 41 extending in the vehicle width direction.

A cooling fan 28a is provided on the right side of the crankcase 20 coaxially with the crankshaft. Cooling fan 28a is covered by fan cover 28 provided on the right side surface of right case 24. The cooling fan 28a is a fan for forced air cooling of the engine, and takes outside air into the fan cover 28 to cool the cylinder 21a and the cylinder head 21 b.

The muffler 7 is connected to an exhaust port 22 of the engine 2 via an exhaust pipe 6. Exhaust gas generated by combustion in the engine 2 passes through the exhaust pipe 6 from the exhaust port 22, is silenced by the muffler 7, and is discharged to the outside. The exhaust pipe 6 will be described in detail later.

Next, the exhaust system of the present embodiment will be described with reference to fig. 7 to 9. Fig. 7 is a perspective view of the exhaust system of the present embodiment. Fig. 8 is a top view of the periphery of the exhaust pipe of the present embodiment. Fig. 9 is a view from direction a of fig. 8.

As shown in fig. 7, the exhaust system according to the present embodiment includes: an exhaust pipe 6 connected to an exhaust port 22 (see fig. 4 and 5); and a muffler 7 connected to the downstream end of the exhaust pipe 6. As shown in fig. 7 to 9, the exhaust pipe 6 is attached to the exhaust port 22 of the engine 2 (the cylinder head 21b (see fig. 5)) via a flange 60.

The exhaust pipe 6 protrudes downward from the exhaust port 22 and then bends to the right side in a substantially horizontal direction when viewed from the front. The exhaust pipe 6 extends rearward along the lower side of the engine 2 and the fan cover 28 (see fig. 2 and 3) in side view.

Specifically, the exhaust pipe 6 is formed by welding and joining a first bent portion 61, a first pipe portion 62, a second bent portion 63, and a second pipe portion 64 in this order from the upstream side. The first bent portion 61 has an L-shape in front view extending downward from the flange 60 and then bent at substantially right angles to the right. That is, the first bending portion 61 bends the exhaust gas flow in the vertical direction toward the horizontal direction (left-right direction) on the upstream side of the first pipe portion 62. The first bent portion 61 is formed by welding and joining divided bodies (front half portion and rear half portion) divided in a direction intersecting the axial direction, i.e., in the front-rear direction in fig. 5. The first curved portion 61 is formed so that the flow path cross section increases as it goes downstream.

The first pipe portion 62 is connected to a downstream end of the first curved portion 61, and extends in the vehicle width direction below a joint surface of the cylinder 21a and the cylinder head 21b (see fig. 2 to 5). The first piping portion 62 has a cylindrical shape extending rightward while maintaining a constant size of a flow path cross section at the downstream end of the first bent portion 61. The first pipe portion 62 is formed by welding and joining divided bodies (upper half portion and lower half portion) divided in the direction intersecting the axial direction, i.e., in the vertical direction in fig. 7. To be described in detail later, the first pipe portion 62 is provided with the catalyst device 50 for purifying the exhaust gas.

The second bent portion 63 is connected to the downstream end of the first pipe portion 62, and has an L-shape in plan view that protrudes rightward and is bent substantially at right angles rearward. That is, the second curved portion 63 curves the exhaust flow path in the vehicle width direction (left-right direction) in the front-rear direction on the downstream side of the second pipe portion 64. The second bent portion 6 is formed by welding and joining divided bodies (upper half portion and lower half portion) divided in the direction intersecting the axial direction, i.e., in the vertical direction in fig. 7. The second curved portion 63 is formed so that the flow path cross section decreases as it goes downstream.

The second pipe portion 64 is connected to the downstream end of the second bend portion 63 and extends rearward of the vehicle with a diameter smaller than the flow passage diameter of the first pipe portion 62. More specifically, the second piping portion 64 is formed in a substantially V-shape as viewed from the side as shown in fig. 2. The second piping portion 64 extends rearward and downward from the upstream end of the second bent portion 63, and then slightly bends upward near the center of the crankshaft below the fan cover 28 and extends rearward and upward.

The muffler 7 has a cylindrical shape having an outer diameter sufficiently larger than that of the exhaust pipe 6. Specifically, the muffler 7 is formed by welding and joining a head portion 7a constituting the upstream end, a case portion 7b connected to the rear of the head portion 7a, and a tail portion 7c connected to the rear of the case portion 7 b.

The head 7a has a bowl shape with an open rear, and is connected to the downstream end of the exhaust pipe 6. The case portion 7b has a cylindrical shape connected to the open end of the head portion 7a, and extends rearward. The tail portion 7c has a bowl shape with an open front, and is joined to the downstream end of the housing portion 7 b. A catalytic device 51 for purifying exhaust gas is provided in the muffler 7.

A bracket 71 for fixing the exhaust pipe 6 and the muffler 7 to the vehicle body side is provided in a portion extending from the rear end portion of the exhaust pipe 6 to substantially the front half of the head portion 7a and the housing portion 7 b. Further, a muffler cover 70 for protecting the muffler 7 is provided on the right side of the muffler 7.

As described above, the

catalytic devices

50 and 51 for purifying the exhaust gas are disposed in the exhaust pipe 6 and the muffler 7. The

catalytic devices

50 and 51 are, for example, three-way catalytic devices, and convert pollutants (carbon monoxide, hydrocarbons, nitrogen oxides, and the like) in the exhaust gas into harmless substances (carbon dioxide, water, nitrogen, and the like).

Further, an upstream sensor 8 and a downstream sensor 9 are provided as exhaust gas sensors for detecting predetermined components in the exhaust gas in the exhaust pipe 6 on the upstream side and the downstream side of the catalytic device 50. To be described in detail later, the upstream sensor 8 is provided in the first bending portion 61, and the downstream sensor 9 is provided in the second pipe portion 64.

The upstream sensor 8 and the downstream sensor 9 are, for example, zirconia type oxygen sensors that detect oxygen as a predetermined component in the exhaust gas. The upstream sensor 8 and the downstream sensor 9 are formed in a cylindrical shape having a predetermined length, one end side thereof is a detection unit, and the other end side thereof is connected to a wire (not shown). In the upstream sensor 8 and the downstream sensor 9, the output (current value) changes according to the oxygen concentration in the exhaust gas. This current value is output to an ECU (Electronic Control Unit/Electronic Control Unit), not shown. The exhaust gas sensor is not limited to the oxygen sensor, and may be, for example, an air-fuel ratio sensor.

The ECU totally controls various actions within the motorcycle 1. The ECU is constituted by a program, a memory, and the like that execute various processes in the motorcycle 1. The Memory is configured by a storage medium such as a ROM (Read Only Memory) or a RAM (Random Access Memory) depending on the application. The memory stores a control program and the like for controlling the respective parts of the motorcycle 1. In particular, in the present embodiment, the ECU performs the deterioration determination of the catalytic device 50 based on the output of the exhaust gas sensor. For example, the ratio of the number of times of output reversal between rich and lean of the upstream side sensor 8 and the downstream side sensor 9 determines the deterioration of the catalytic device 50. In order to determine the deterioration of the catalytic device 50, the output difference between the upstream sensor 8 and the downstream sensor 9 may be used instead of using the ratio of the number of times of output reversal.

However, as described above, in the exhaust system of the motorcycle, monitoring of the deterioration condition of the catalytic device as the exhaust gas purifying device is required. In order to perform the deterioration determination of the catalytic device, it is necessary to provide exhaust gas sensors upstream and downstream of the catalytic device.

For example, the following embodiments have been implemented: the air-fuel ratio is controlled by detecting the oxygen concentration in the exhaust gas by an exhaust gas sensor (oxygen sensor) provided on the upstream side of the catalytic device. However, when the exhaust gas sensor is disposed also on the downstream side of the catalyst device for the purpose of determining the deterioration of the catalyst device, it is difficult to bring the exhaust gas sensor closer to the downstream side of the catalyst device while ensuring a predetermined detection accuracy due to layout constraints specific to the motorcycle.

In this regard, in the automobile, since the catalyst device can be disposed in a space having a margin such as an engine room, the exhaust gas sensor can be easily disposed and protected. On the other hand, in many motorcycles, a catalyst device is disposed in a chamber or a muffler, and it is structurally difficult to dispose an exhaust gas sensor close to the catalyst device as described above. Further, even if the catalytic device is disposed in the middle of the exhaust pipe, the exhaust pipe and the peripheral components are often close to each other, and it is difficult to secure a space for disposing the exhaust gas sensor. Further, since the exhaust system of the motorcycle is exposed to the outside, it is also assumed that the temperature of the catalyst device is likely to decrease during running in winter or rainy weather, for example, and the sensor output cannot be obtained appropriately. In addition, protection of the exhaust gas sensor is also problematic.

For example, when a catalytic device is provided in a muffler such as a chamber or a muffler, it is conceivable to secure a space for disposing an exhaust gas sensor by recessing an outer wall. However, the volumes of the chamber and the muffler are reduced, and as a result, the original functions (increase in output and sound attenuation) may be affected.

Further, it is also conceivable to dispose the catalytic device itself on the front side of the vehicle, but it is not practical to secure the disposition space of the catalytic device originally, and it is necessary to change the design greatly. Further, various problems occur as follows: thermal damage due to the approach of the catalyst device as a heat source to the rider, a decrease in output, a method of protecting the exhaust gas sensor, deterioration in design, and the like.

Particularly in a small scooter type motorcycle, an exhaust pipe needs to be disposed in a narrow space between an engine and a frame, and the exhaust pipe is set to a small pipe diameter. In this case, it is very difficult to dispose a catalyst device or an exhaust gas sensor in the exhaust pipe while securing a gap between peripheral components.

In addition, in the scooter type motorcycle, it is considered to directly dispose an exhaust gas sensor in a muffler. However, in the muffler (in the expansion chamber), it is difficult to accurately detect the oxygen concentration by the exhaust gas sensor due to turbulence of the exhaust gas, and therefore the performance of the exhaust gas sensor cannot be sufficiently satisfied. Further, the temperature of the exhaust gas decreases toward the downstream of the exhaust gas flow path. Therefore, depending on the layout of the exhaust gas sensor, it takes time to reach the active temperature region of the exhaust gas sensor. This causes the exhaust gas sensor to be difficult to operate in the cold state of the engine. Further, if the exhaust gas sensor is disposed in the muffler, the exhaust gas sensor is located behind the vehicle, and therefore, the wiring of the exhaust gas sensor becomes long, which may complicate the wiring and increase the number of fixed parts.

That is, it is difficult to satisfy the standard of exhaust gas restriction which will become strict in the future, and it is inevitable to increase the size of the catalytic device in order to achieve the standard. As a countermeasure, it is conceivable to dispose the catalytic device as close to the exhaust port as possible, but restrictions on the disposition of the exhaust pipe and the disposition of other components (such as an exhaust gas sensor) become more severe as the exhaust port becomes closer. In particular, in a scooter type motorcycle of a lower suspension type in which the engine 2 is suspended from the body frame 3 below the cylinder 21a and the cylinder head 21b as shown in fig. 2, this restriction is more severe.

Therefore, in the scooter-type motorcycle 1, the inventors of the present invention extended a part of the exhaust pipe 6 (the first pipe portion 62) in the vehicle width direction below the cylinder head 21b, and disposed the catalyst device 50 in the axial direction inside the first pipe portion 62. Further, an upstream sensor 8 is disposed on the upstream side of the catalytic device 50 in the exhaust pipe 6 (first bend 61) directly below the exhaust port 22.

With this configuration, the catalyst device 50 and the upstream sensor 8 can be disposed close to the cylinder 21a and the cylinder head 21b as heat sources. Therefore, after the engine 2 is started, the catalyst device 50 and the upstream sensor 8 can be heated and activated as quickly as possible. This improves the exhaust gas purification performance and also improves the accuracy of detecting the exhaust gas component. In addition, the degree of freedom in the arrangement of peripheral components can be improved, and the engine 2 can be made compact.

Next, the arrangement structure of the catalytic device and the exhaust gas sensor according to the present embodiment will be described with reference to fig. 2 to 7.

As shown in fig. 2 to 7, the catalyst device 50 is disposed in the first pipe portion 62 so that the axial direction thereof faces the vehicle width direction. Although not shown, a minute space is formed between the first pipe portion 62 and the catalyst device 50, and a double pipe structure is formed. Therefore, the heat of the first pipe portion 62 and the catalyst device 50 is difficult to be transmitted to the outside. This can suppress thermal damage to the rider.

Further, as shown in fig. 4, the catalytic device 50 is located directly below the exhaust port 22 between a center line C1 passing through the axial center of the cylinder 21a and a center line C3 passing through the axial center of the second pipe portion 64. Therefore, the catalytic device 50 can be disposed as close to the exhaust port 22 as possible.

Further, by forming the first pipe portion 62, the first bent portion 61, and the second bent portion 63 by two divided bodies, the first pipe portion 62, the first bent portion 61, and the second bent portion 63 can be formed by forming the two divided bodies by press working in advance.

In particular, the first bending portion 61 and the second bending portion 63 are configured to be divided in the front-rear direction or in the vertical direction, that is, divided into two on a plane parallel to a plane defining the respective bending directions, so that the bending radii of the first bending portion 61 and the second bending portion 63 can be made smaller than those in the case of forming by bending a linear pipe. This allows the first bending portion 61 and the second bending portion 63 to be rapidly bent, thereby improving the degree of freedom of layout. As a result, the exhaust pipe 6 having a sharp bend can be formed in the vicinity of the exhaust port 22. Therefore, the catalytic device 50 can also be disposed closer to the exhaust port 22.

In addition, the catalytic device 50 is disposed between the cylinder head 21b and the engine mount 4 in a side view shown in fig. 2. Therefore, even in the lower suspension type engine 2, the catalytic device 50 can be disposed directly below the cylinder head 21 b. The front of the catalyst device 50 is surrounded by the body frame 3, the rear is surrounded by the crankcase 20, the upper is surrounded by the cylinder head 21b, and the lower is surrounded by the engine mount 4. This makes it possible to protect the catalytic device 50 from flying stones, water, and the like without covering with a dedicated cover, and the appearance is inconspicuous.

The upstream side sensor 8 is attached to the curved portion of the first curved portion 61 from the left. Specifically, the nut 80 is welded to the left split surface of the first bent portion 61. By disposing the nut 80 on the split surface, a seat surface when the nut 80 is welded can be easily secured. The upstream sensor 8 is attached such that one end thereof is screwed into the nut 80 and the tip thereof penetrates the exhaust pipe 6 (the first bent portion 61). Thereby, the exhaust gas flowing in the first curved portion 61 can be detected by the upstream sensor 8.

In particular, the tip end of the upstream sensor 8 is disposed at a position overlapping the exhaust port 22 (flange 60) when viewed in the axial direction of the exhaust port 22. In this way, the tip end of the upstream sensor 8 is positioned so as to face the exhaust port 22, and therefore, even if the catalytic device 50 is disposed directly below the cylinder head 21b, the upstream sensor 8 can be disposed in the vicinity of the exhaust port 22. As a result, the activation of the upstream sensor 8 is promoted as soon as possible, and the detection accuracy of the exhaust gas component is improved.

The upstream sensor 8 is disposed so that its axial direction is oriented in the vehicle width direction, and is parallel to and coaxial with the axial direction of the catalyst device 50. The upstream sensor 8 and the catalytic device 50 are arranged so as to sandwich the exhaust port 22 in plan view. Further, the upstream sensor 8 is disposed within the width of the cylinder head 21b and between the pair of engine mount brackets 4 on the lower surface of the exhaust port 22. The upstream sensor 8 is also surrounded by the body frame 3 at the front, the crankcase 20 at the rear, the cylinder head 21b at the upper side, and the engine mount 4 at the lower side, as in the case of the catalyst device 50. This can protect the upstream sensor 8 from flying stones, water, and the like without being covered with a dedicated cover, and is not visually conspicuous.

The catalytic device 50 and the upstream sensor 8 are disposed near the pivot portion (the distal ends of the

engine mount portions

23a, 24 a). Therefore, the amount of movement of the catalyst device 50 and the upstream sensor 8 accompanying the swing of the engine 2 can be reduced, and interference with peripheral components can be prevented. In particular, the wiring of the upstream sensor 8 can be easily handled.

The downstream side sensor 9 is attached to the front half of the second pipe portion 64 from the right. Specifically, the nut 90 is welded to the right side surface of the second pipe portion 64. The nut 90 is screwed into one end side of the downstream sensor 9, and the tip end of the downstream sensor 9 is attached so as to penetrate through the second pipe section 64. Thereby, the exhaust gas flowing through the second pipe portion 64 can be detected by the downstream side sensor 9.

In addition, the downstream side sensor 9 is disposed in front of and below the center of the crankshaft (the center of the cooling fan 28 a) when viewed from the side as shown in fig. 2. Further, the downstream side sensor 9 has an axial direction facing the vehicle width direction and a tip end facing the inside in the vehicle width direction. That is, the downstream side sensor 9 is provided on the opposite side of the upstream side sensor 8 with the center line C1 interposed therebetween. In this way, the tips of the upstream sensor 8 and the downstream sensor 9 are both directed toward the vehicle inside, and the detection portion at the tip of each sensor can be disposed closer to the exhaust port 22. This enables detection of the exhaust gas on the exhaust upstream side as much as possible, and improves the detection accuracy.

In this way, in the present embodiment, two exhaust gas sensors (the upstream side sensor 8 and the downstream side sensor 9) are disposed on the exhaust pipe 6 which is the upstream side of the muffler 7, and thus the exhaust gas can be detected upstream and downstream of the catalytic device 50 without reducing the capacity of the muffler 7. This enables detection of the exhaust gas before diffusion in the muffler 7, and improves the detection accuracy.

In the above embodiment, the single cylinder engine 2 is described as an example, but the present invention is not limited to this configuration. For example, the engine 2 may be a multi-cylinder engine having two or more cylinders, and the arrangement of the cylinders may be changed as appropriate.

In the above embodiment, the vehicle body frame 3 is configured by the underbeam type frame, but the configuration is not limited thereto. The body frame 3 may also be a rhombus-type, double-beam frame, for example.

In the above embodiment, the unit swing type engine 2 is described as an example, but the present invention is not limited to this configuration. The engine may also be another type of engine in which the crankcase and the swing arm are formed of different parts.

In the above embodiment, the configuration in which the muffler 7 is formed in the cylindrical shape has been described, but the configuration is not limited to this configuration. The muffler 7 may also have, for example, a rectangular cross section, or other profiled cross section.

In the above embodiment, the first pipe portion 62 is formed by connecting vertically divided bodies, but is not limited to this structure. The first pipe portion 62 may be formed of only a cylindrical pipe.

In the above embodiment, the exhaust pipe 6 is arranged along the right side of the engine 2, but the present invention is not limited to this configuration. The bending direction of the exhaust pipe 6 can be changed as appropriate, and for example, the exhaust pipe 6 may be configured to extend along the left side of the engine 2.

In the above embodiment, the first bending portion 61 is configured by being divided into the front and rear portions, and the first pipe portion 62 and the second bending portion 63 are configured by being divided into the upper and lower portions. The first bending portion 61 and the second bending portion 63 may be formed by joining two members, and may be changed according to the bending direction. The first pipe portion 62 may be divided into front and rear portions.

In the above embodiment, the downstream sensor 9 is attached from the right side surface of the second pipe portion 64, but the present invention is not limited to this configuration. The downstream side sensor 9 may be attached, for example, from the right side surface of the second curved portion 63. In this case, it is preferable that a nut 90 is welded to the divided surface of the second curved portion 63 and the downstream sensor 9 is screwed into the nut 90.

In the above embodiment, the engine 2 is suspended below the cylinder 21a and the cylinder head 21b by the lower suspension type unit swing engine, but the present invention is not limited to this configuration. For example, the engine may be a swing unit engine of an upper suspension type in which the engine 2 is suspended on the vehicle body frame 3 above the cylinder 21a and the cylinder head 21 b.

Further, although the present embodiment and the modification have been described, the above embodiments and modifications may be combined in whole or in part as another embodiment of the present invention.

The present invention is not limited to the above-described embodiments, and various changes, substitutions, and alterations can be made without departing from the spirit and scope of the present invention. Further, if the technical idea of the present invention can be realized by another method by using another technique derived from a technical advance, the present invention can be implemented by using the method. Therefore, the scope of the present invention covers all embodiments that can be included in the scope of the technical idea of the present invention.

Industrial applicability

As described above, the present invention has the following effects: the exhaust gas purifying performance can be improved, and the exhaust gas sensor can be arranged without impairing the detection accuracy of the exhaust gas component, and is particularly useful in an arrangement structure of the exhaust gas sensor applicable to a motorcycle.

Claims

1. An arrangement structure of an exhaust gas sensor includes:

an engine having a cylinder and a cylinder head disposed in front of a crankcase;

an exhaust pipe attached to an exhaust port of the cylinder head;

a catalyst device disposed in the middle of the exhaust pipe; and

a first exhaust gas sensor that is located on an upstream side of the catalytic device and that is attached to the exhaust pipe,

the arrangement structure of the exhaust gas sensor is characterized in that,

the axis of the cylinder is oriented in a substantially horizontal direction, the exhaust port is provided on the lower side of the cylinder head,

the exhaust pipe has a first pipe portion extending in the vehicle width direction below the cylinder head,

the catalyst device is disposed in the first pipe portion so that an axial direction thereof faces a vehicle width direction,

the exhaust pipe has a first bent portion that bends an exhaust flow path on an upstream side of the first pipe portion,

the first bent portion is formed by joining split bodies split in a direction intersecting with an axial direction.

2. The arrangement of exhaust gas sensors according to claim 1,

the first exhaust gas sensor is mounted to the first bent portion,

the tip end of the first exhaust gas sensor overlaps with the exhaust port as viewed from the axial direction of the exhaust port.

3. An arrangement structure of an exhaust gas sensor includes:

an exhaust pipe attached to an exhaust port of the cylinder head;

a catalyst device disposed in the middle of the exhaust pipe; and

the arrangement structure of the exhaust gas sensor is characterized in that,

the first exhaust gas sensor is parallel to and disposed coaxially with an axial direction of the catalytic device.

4. An arrangement structure of an exhaust gas sensor includes:

an exhaust pipe attached to an exhaust port of the cylinder head;

a catalyst device disposed in the middle of the exhaust pipe; and

the arrangement structure of the exhaust gas sensor is characterized in that,

the first exhaust gas sensor and the catalytic device are disposed on both sides of the exhaust port in a plan view.

5. An arrangement structure of an exhaust gas sensor includes:

an exhaust pipe attached to an exhaust port of the cylinder head;

a catalyst device disposed in the middle of the exhaust pipe; and

the arrangement structure of the exhaust gas sensor is characterized in that,

the first exhaust gas sensor is disposed within a width of the cylinder head below the exhaust port.

6. An arrangement structure of an exhaust gas sensor includes:

an exhaust pipe attached to an exhaust port of the cylinder head;

a catalyst device disposed in the middle of the exhaust pipe;

a first exhaust gas sensor that is located on an upstream side of the catalytic device and that is attached to the exhaust pipe; and

a bracket that suspends the engine from a frame,

the arrangement structure of the exhaust gas sensor is characterized in that,

the bracket is disposed below the cylinder head,

the catalytic device is disposed between the cylinder head and the bracket,

a pair of the brackets are arranged in parallel in the vehicle width direction,

the first exhaust gas sensor is disposed between the pair of brackets below the exhaust port.

7. An arrangement structure of an exhaust gas sensor includes:

an exhaust pipe attached to an exhaust port of the cylinder head;

a catalyst device disposed in the middle of the exhaust pipe;

a second exhaust gas sensor attached to the exhaust pipe on a downstream side of the catalytic device,

the arrangement structure of the exhaust gas sensor is characterized in that,

the second exhaust gas sensor is disposed forward and downward of the center of the crankshaft,

the second exhaust gas sensor is disposed on the opposite side of the first exhaust gas sensor with the cylinder interposed therebetween,

the top ends of the first exhaust gas sensor and the second exhaust gas sensor face towards the inner side.

8. An arrangement structure of an exhaust gas sensor includes:

an exhaust pipe attached to an exhaust port of the cylinder head;

a catalyst device disposed in the middle of the exhaust pipe;

a first exhaust gas sensor that is located on an upstream side of the catalytic device and that is attached to the exhaust pipe; a second exhaust gas sensor attached to the exhaust pipe on a downstream side of the catalytic device,

the arrangement structure of the exhaust gas sensor is characterized in that,

the exhaust pipe has:

a second curved portion that curves the exhaust gas flow path on a downstream side of the first pipe portion; and

a second pipe portion connected to a downstream side of the second bending portion,

the second bend is formed by joining together parts divided into two parts,

the second exhaust gas sensor is attached to the second bent portion or the second pipe portion.

9. A motorcycle, characterized by comprising:

the arrangement structure of an exhaust gas sensor according to any one of claims 1 to 8.