JP6922492B2 - Exhaust gas sensor layout structure and motorcycle - Google Patents

Description

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

With the recent exhaust gas regulations, it is required to monitor the deterioration status of the catalyst that purifies the exhaust gas in the exhaust system of the vehicle engine. 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.

Specifically, in Patent Document 1, the inside of the silencer is partitioned by a plurality of partition walls (separators), and a plurality of expansion chambers are formed. A catalyst is arranged inside the silencer, and extends until the downstream end of the catalyst protrudes into a predetermined expansion chamber. Further, a plurality of exhaust pipes are connected to each expansion chamber and the catalyst. The oxygen sensor is mounted so as to penetrate the exhaust pipe on the downstream side of the catalyst.

Japanese Unexamined Patent Publication No. 2016-160914

However, in Patent Document 1, a part of the outer wall of the silencer is recessed in order to arrange the oxygen sensor. Therefore, the volume of the expansion chamber is reduced by the amount that the outer wall is recessed, and the sound deadening effect of the exhaust gas may be reduced. Further, since the temperature of the exhaust gas decreases as it goes downstream, there is a possibility that the oxygen concentration of the exhaust gas cannot be appropriately detected while ensuring the exhaust purification performance from the viewpoint of temperature activation of the catalyst and the oxygen sensor.

The present invention has been made in view of the above points, and provides an exhaust gas sensor arrangement structure and a motorcycle capable of improving the exhaust gas purification performance and arranging the exhaust gas sensor without impairing the detection accuracy of the exhaust gas component. The purpose is to do.

The arrangement structure of the exhaust gas sensor according to one aspect of the present invention includes an engine having a cylinder and a cylinder head arranged in front of a crankcase, an exhaust pipe attached to an exhaust port of the cylinder head, and an arrangement in the middle of the exhaust pipe. The cylinder is provided with a catalyst to be formed and a first exhaust gas sensor attached to the exhaust pipe on the upstream side of the catalyst, the axis of the cylinder is directed in a substantially horizontal direction, and the exhaust port is on the lower side of the cylinder head. The exhaust pipe has a first piping portion extending in the vehicle width direction below the cylinder head, and the catalyst is provided in the first piping portion so that the axial direction faces the vehicle width direction. disposed, the first exhaust gas sensor is arranged coaxially in parallel to the axial direction of the catalyst, characterized in Rukoto.

According to the present invention, it is possible to improve the exhaust gas purification performance and arrange the exhaust gas sensor without impairing the detection accuracy of the exhaust gas component.

It is a right side view which shows the schematic structure of the motorcycle to which the arrangement structure of the exhaust gas sensor which concerns on this embodiment is applied. It is a right side view which shows the engine peripheral structure of the motorcycle shown in FIG. It is the figure which omitted the partial structure from FIG. It is a bottom view of the engine peripheral configuration shown in FIG. It is the figure which omitted the partial structure from FIG. It is a front view of the engine peripheral configuration shown in FIG. It is a perspective view of the exhaust system which concerns on this embodiment. It is a top view around the exhaust pipe which concerns on this embodiment. It is a view of arrow A of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying 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 target is not limited to this 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, buggy type motorcycles, motorcycles and the like. Further, regarding the directions, the front of the vehicle is indicated by an arrow FR, the rear of the vehicle is indicated by an arrow RE, the upper part of the vehicle is indicated by an arrow UP, the lower part of the vehicle is indicated by an arrow LO, the left direction of the vehicle is indicated by an arrow L, and the right direction of the vehicle is indicated by an arrow R. Further, in each of the following figures, some configurations are omitted for convenience of explanation.

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

As shown in FIG. 1, the small scooter type motorcycle 1 is configured by suspending the engine 2 on an underbone type body frame 3 (see FIG. 2). The engine 2 is composed of, for example, a single cylinder engine. In particular, in the present embodiment, a unit swing type engine in which the transmission mechanism to the engine 2, the transmission (CVT unit or the like described later) and the rear wheel 26 is integrated with the swing arm is adopted.

Various covers for the exterior of the vehicle body are attached to the vehicle body frame and the engine 2. Specifically, on the front side of the vehicle, a leg shield 11 that protects the driver's undercarriage is provided in front of the vehicle. 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 surface of the vehicle is provided behind the footboard 13.

A front fork 15 is rotatably supported in front of the vehicle via a steering shaft (not shown). A handlebar 17 for steering the front wheels 16 is provided above the front fork 15. A front wheel 16 is rotatably supported under the front fork 15.

A seat 18 is provided on the upper side of the side frame cover 14. A rear fender 19 is provided at the rear of the side frame cover 14. The engine 2 as an internal combustion engine is arranged from the inside to the rear of the side frame cover 14.

The engine 2 extends back and forth behind the footboard 13. The front end portion of the engine 2 is connected to the vehicle body frame 3, and the entire engine 2 can swing up and down with the connecting portion as a fulcrum. A 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 the exhaust port 22 (see FIGS. 4 and 5) of the engine 2 as an exhaust system. The exhaust pipe 6 extends below the engine 2 toward the rear. The muffler 7 is connected to the rear end of the exhaust pipe 6 and is arranged so as to overlap the rear wheel 26 in a side view. A muffler cover 70 is provided on the right side surface of the muffler 7.

Next, the engine and its peripheral configuration according to the present embodiment will be described with reference to FIGS. 2 to 6. FIG. 2 is a right side view showing the engine peripheral configuration of the motorcycle shown in FIG. FIG. 3 is a diagram in which a partial configuration is omitted from FIG. FIG. 4 is a bottom view of the engine peripheral configuration shown in FIG. FIG. 5 is a diagram in which a partial configuration is omitted from FIG. FIG. 6 is a front view of the engine peripheral configuration shown in FIG.

As described above, the engine 2 according to the present embodiment is composed of a unit swing type engine adopted in the scooter type motorcycle 1 (see FIG. 1). As shown in FIGS. 2 to 6, the engine 2 is oscillatedly suspended from the vehicle body frame 3 via the engine suspension bracket 4.

The vehicle body frame 3 includes an underframe 30 extending forward and backward below the footboard 13 (see FIG. 1), a pair of side frames 31 extending rearward and upward from the rear end of the underframe 30, an underframe 30 and a pair of side frames. It is configured to include a connecting frame 32 that connects 31s.

The underframe 30 extends forward and backward in the front lower part of the engine 2 so as to pass through substantially the center in the vehicle width direction (on the center line C1 of the cylinder described later). The connecting frame 32 is connected to the rear end of the under 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 by arranging a cylinder 21a, a cylinder head 21b, and a cylinder head cover 21c in this order in front of a crankcase 20 in which various components such as a crankshaft (not shown) are housed. The cylinder 21a is arranged so as to be tilted forward so that the axis line faces in the substantially horizontal direction.

Specifically, the axis of the cylinder 21a is oriented in a direction (substantially horizontal direction) in which the front side (cylinder head cover 21c side) is slightly higher than the horizontal direction. That is, the horizontal direction in the present embodiment does not mean only the complete horizontal direction, but is a concept having a predetermined width within a range that does not deviate from the gist of the present invention.

The cylinder 21a is attached to the front portion of the crankcase 20. A cylindrical cylinder bore (combustion chamber) for accommodating a piston is formed inside the cylinder 21a (both not shown). The cylinder head 21b is attached to the front portion of the cylinder 21a. The cylinder head 21b is formed with an intake port (not shown) and an exhaust port 22 communicating with the combustion chamber. The exhaust port 22 is provided on the lower side (lower surface side) of the cylinder head 21b and 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 serves to cover the cylinder head 21b. Inside the cylinder head 21b and the cylinder head cover 21c, an intake / exhaust valve (not shown) and a valve operating mechanism (not shown) for opening / closing the intake / exhaust valve are housed.

The crankcase 20 is configured by connecting the left and right case 23 and the right case 24, which are split left and right, with bolts or the like. The mating surface of the left case 23 and the right case 24 passes through the center of the cylinder axis. In FIG. 3, a straight line passing through the axis center of the cylinder (the mating surface of the left case 23 and the right case 24) is represented by the center line C1. A crankshaft is housed in the crankcase 20, and the crankshaft is arranged so that the axial direction is horizontal in the vehicle width direction. In FIG. 3, the center of the crankshaft is indicated by the center line C2.

In particular, the left case 23 extends rearward, and the rear wheels 26 are rotatably attached to the rear end via the gear case 27. That is, the left case 23 constitutes a swing arm that cantileverly supports the rear wheel 26. The left side surface of the left case 23 is open, and a CVT unit (not shown) as a transmission is housed inside. The CVT unit is composed of a so-called belt-type continuously variable transmission, and realizes shifting by changing the winding radius of the belt. An engine cover 25 is attached to the left side of the left case 23, and the opening of the left case 23 is closed. A reduction gear (not shown) is housed in the gear case 27.

Further, the left case 23 and the right case 24 are formed with engine suspension portions 23a and 24a for connecting (suspending) the engine 2 to the vehicle body frame 3. The engine suspension portions 23a and 24a are formed so as to project forward from the lower surfaces of the left case 23 and the right case 24 toward the lower side of the cylinder 21a. The engine suspension portions 23a and 24a are arranged side by side in the vehicle width direction and face each other with the center line C1 in between. The tips of the engine suspension portions 23a and 24a form a swing shaft (pivot portion) of the engine 2.

A pair of engine suspension brackets 4 are attached to the engine suspension portions 23a and 24a. The engine suspension bracket 4 extends forward from the tips of the engine suspension portions 23a and 24a. The pair of engine suspension brackets 4 are arranged below the cylinder head 21b in the vehicle width direction corresponding to the engine suspension portions 23a and 24a, and face each other with the center line C1 in between.

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

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

A muffler 7 is connected to the exhaust port 22 of the engine 2 via an exhaust pipe 6. The exhaust gas generated by the combustion of the engine 2 is muted by the muffler 7 from the exhaust port 22 through the exhaust pipe 6 and then discharged to the outside. The details of the exhaust pipe 6 will be described later.

Next, the exhaust system according to the present embodiment will be described with reference to FIGS. 7 to 9. FIG. 7 is a perspective view of the exhaust system according to the present embodiment. FIG. 8 is a top view of the vicinity of the exhaust pipe according to the present embodiment. FIG. 9 is a view taken along the arrow A of FIG.

As shown in FIG. 7, in the exhaust system according to the present embodiment, the exhaust pipe 6 connected to the exhaust port 22 (see FIGS. 4 and 5) and the muffler 7 connected to the downstream end of the exhaust pipe 6 are connected. Consists of including. As shown in FIGS. 7 to 9, the exhaust pipe 6 is attached to the exhaust port 22 of the engine 2 (cylinder head 21b (see FIG. 5)) via the flange 60.

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

Specifically, the exhaust pipe 6 is formed by welding and joining the first bent portion 61, the first piping portion 62, the second bent portion 63, and the second piping portion 64 in this order from the upstream side. The first bent portion 61 has an L-shaped front view that extends downward from the flange 60 and then bends to the right at a substantially right angle. That is, the first bent portion 61 bends the exhaust flow path in the vertical direction in the horizontal direction (horizontal direction) on the upstream side of the first piping portion 62. Further, the first bent portion 61 is formed by welding and joining the divided bodies (first half portion and the second half portion) divided in the direction intersecting in the axial direction and in the front-rear direction in FIG. Further, the first bent portion 61 is formed so that the cross section of the flow path becomes larger toward the downstream.

The first piping portion 62 is connected to the downstream end of the first bent portion 61 and extends in the vehicle width direction below the mating surface of the cylinder 21a and the cylinder head 21b (see FIGS. 2 to 5). The first piping portion 62 has a cylindrical shape extending to the right while keeping the size of the cross section of the flow path at the downstream end of the first bent portion 61 constant. Further, the first piping portion 62 is formed by welding and joining the divided bodies (upper half portion and lower half portion) divided in the direction intersecting in the axial direction and in the vertical direction in FIG. 7. Although details will be described later, the first piping portion 62 is provided with a catalyst 50 for purifying the exhaust gas.

The second bent portion 63 has an L-shaped plan view that is connected to the downstream end of the first piping portion 62, protrudes to the right, and then bends rearward at a substantially right angle. That is, the second bent portion 63 bends the exhaust flow path in the vehicle width direction (left-right direction) in the front-rear direction on the downstream side of the second piping portion 64. Further, the second bent portion 63 is formed by welding and joining the divided bodies (upper half portion and lower half portion) divided in the direction intersecting in the axial direction and in the vertical direction in FIG. 7. Further, the second bent portion 63 is formed so that the cross section of the flow path becomes smaller toward the downstream.

The second piping portion 64 is connected to the downstream end of the second bent portion 63 and extends to the rear of the vehicle with a diameter smaller than the flow path diameter of the first piping portion 62. More specifically, in the side view shown in FIG. 2, the second piping portion 64 is formed in a substantially V shape. The second piping portion 64 extends rearwardly and downwardly from the upstream end of the second bent portion 63, and then slightly bends upwardly near the center of the crankshaft below the fan cover 28 and extends rearwardly and upwardly.

The muffler 7 has a cylindrical shape having a sufficiently large outer diameter as compared with the exhaust pipe 6. Specifically, in the muffler 7, the head portion 7a constituting the upstream end, the case portion 7b connected to the rear of the head portion 7a, and the tail portion 7c connected to the rear of the case portion 7b are welded and joined. It is composed.

The head portion 7a has a bowl-shaped shape with an open rear portion, 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-shaped shape with an open front and is joined to the downstream end of the case portion 7b. A catalyst 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 the substantially front half portion of the head portion 7a and the case portion 7b. Further, on the right side of the muffler 7, a muffler cover 70 for protecting the muffler 7 is provided.

As described above, the catalysts 50 and 51 for purifying the exhaust gas are arranged in the middle of the exhaust pipe 6 and in the muffler 7. The catalysts 50 and 51 are composed of, for example, a three-way catalyst, and convert pollutants (carbon monoxide, hydrocarbons, nitrogen oxides, etc.) in the exhaust gas into harmless substances (carbon dioxide, water, nitrogen, etc.). ..

Further, on the upstream side and the downstream side of the catalyst 50, the exhaust pipe 6 is provided with an upstream side sensor 8 and a downstream side sensor 9 as an exhaust gas sensor for detecting a predetermined component in the exhaust gas. Although the details will be described later, the upstream side sensor 8 is provided in the first bending portion 61, and the downstream side sensor 9 is provided in the second piping portion 64.

The upstream side sensor 8 and the downstream side sensor 9 are composed of, for example, a zirconia type oxygen sensor that detects oxygen as a predetermined component in the exhaust gas. The upstream side sensor 8 and the downstream side sensor 9 are formed in a columnar shape having a predetermined length, one end side serves as a detection unit, and wiring (not shown) is connected to the other end side. In the upstream sensor 8 and the downstream sensor 9, the output (current value) changes according to the oxygen concentration in the exhaust gas. The current value is output to an ECU (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 controls various operations in the motorcycle 1 in an integrated manner. The ECU is composed of a processor, a memory, and the like that execute various processes in the motorcycle 1. The memory is composed of a storage medium such as a ROM (Read Only Memory) or a RAM (Random Access Memory) depending on the application. A control program or the like for controlling each part of the motorcycle 1 is stored in the memory. In particular, in the present embodiment, the ECU determines the deterioration of the catalyst 50 based on the output of the exhaust gas sensor. For example, the deterioration of the catalyst 50 is determined based on the ratio of the number of output reversals between the rich lean of the upstream sensor 8 and the downstream sensor 9. In order to determine the deterioration of the catalyst 50, not only the ratio of the number of output inversions is used, but also the output difference between the upstream sensor 8 and the downstream sensor 9 may be used.

By the way, as described above, in the exhaust system of a motorcycle, it is required to monitor the deterioration state of the catalyst as an exhaust gas purification device. In order to determine the deterioration of the catalyst, it is necessary to install exhaust gas sensors upstream and downstream of the catalyst.

For example, it has been conventionally practiced to detect the oxygen concentration in the exhaust gas with an exhaust gas sensor (oxygen sensor) provided on the upstream side of the catalyst and control the air-fuel ratio. However, if an exhaust gas sensor is to be placed on the downstream side of the catalyst for the purpose of determining deterioration of the catalyst, the exhaust gas sensor is brought closer to the downstream side of the catalyst while ensuring a predetermined detection accuracy due to layout restrictions peculiar to motorcycles. It was difficult.

In this respect, in the automobile, the catalyst can be arranged in a place where there is enough space, such as in the engine room, so that the exhaust gas sensor can be arranged and protected relatively easily. On the other hand, in a motorcycle, the catalyst is often arranged in the chamber or the muffler, and as described above, it is difficult to arrange the exhaust gas sensor close to the catalyst due to its structure. Further, even when the catalyst is arranged in the middle of the exhaust pipe, the exhaust pipe and peripheral parts are often close to each other, and it is difficult to secure a space for arranging the exhaust gas sensor. Further, since the exhaust system of the motorcycle is exposed to the outside, it is assumed that the temperature of the catalyst tends to drop and the sensor output cannot be obtained appropriately, for example, in winter or when traveling in the rain. In addition, protection of the exhaust gas sensor also becomes a problem.

For example, when a catalyst is provided in a silencer such as a chamber or a muffler, it is conceivable to dent the outer wall to secure a space for arranging the exhaust gas sensor. However, as a result of reducing the volume of the chamber and muffler, there is a risk of affecting the original functions (increasing output and muffling). It is also conceivable to arrange the catalyst itself on the front side of the vehicle, but this is not very realistic because it is difficult to secure a space for arranging the catalyst in the first place and a large design change is required. Further, various problems such as heat damage caused by the catalyst as a heat source approaching the rider, a decrease in output, a method for protecting the exhaust gas sensor, and deterioration in appearance design occur.

In particular, in the case of a small scooter type motorcycle, it is necessary to dispose the exhaust pipe in a narrow space between the engine and the frame, and the exhaust pipe is set to a relatively small pipe diameter. In this case, it is very difficult to arrange the catalyst and the exhaust gas sensor in the exhaust pipe while securing a gap with the peripheral parts.

Further, in a small scooter, it is conceivable to arrange an exhaust gas sensor directly on the muffler. However, in the muffler (expansion chamber), it is difficult for the exhaust gas sensor to accurately detect the oxygen concentration due to the turbulent flow of the exhaust gas, so that the performance of the exhaust gas sensor cannot be fully satisfied. Further, the temperature of the exhaust gas decreases toward the downstream of the exhaust flow path. Therefore, depending on the layout of the exhaust gas sensor, it may take some time to reach the active temperature range of the exhaust gas sensor. This causes the exhaust gas sensor to become difficult to work in the cold state of the engine. Further, if the exhaust gas sensor is arranged on the muffler, it will be located at the rear of the vehicle, so that the wiring of the exhaust gas sensor becomes long, which may complicate the wiring and increase the number of fixed points.

In other words, it will be difficult to meet the standards of exhaust gas regulations that will become stricter in the future, and in order to meet those standards, it is inevitable that the size of the catalyst will increase. As a countermeasure, it is conceivable to arrange the catalyst as close to the exhaust port as possible, but the closer it is, the more severe the restrictions on the arrangement of the exhaust pipe and the arrangement of other parts (exhaust gas sensor, etc.) become. In particular, in the case of a lower suspension type scooter in which the engine 2 is suspended on the vehicle body frame 3 below the cylinder 21a and the cylinder head 21b shown in FIG. 2, the restrictions are further severe.

Therefore, in the small scooter type motorcycle 1, the inventor extends a part of the exhaust pipe 6 (first piping portion 62) below the cylinder head 21b in the vehicle width direction, and extends the shaft in the first piping portion 62. The catalyst 50 was placed along the direction. Further, the upstream sensor 8 is arranged on the exhaust pipe 6 (first bent portion 61) on the upstream side of the catalyst 50 and directly below the exhaust port 22.

According to this configuration, the catalyst 50 and the upstream sensor 8 can be arranged close to the cylinder 21a and the cylinder head 21b which are heat sources. Therefore, the catalyst 50 and the upstream sensor 8 can be warmed and activated at an early stage after the engine 2 is started. Therefore, it is possible to improve the exhaust gas purification performance and the detection accuracy of the exhaust gas component. In addition, the degree of freedom in arranging peripheral parts can be improved, and the engine 2 can be made compact.

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

As shown in FIGS. 2 to 7, the catalyst 50 is arranged in the first piping portion 62 so that the axial direction faces the vehicle width direction. Further, although not shown, a slight space is formed between the first piping portion 62 and the catalyst 50, forming a double pipe structure. Therefore, it is difficult for the heat of the first piping portion 62 and the catalyst 50 to be transferred to the outside. Therefore, it is possible to suppress heat damage to the rider.

Further, as shown in FIG. 3, the catalyst 50 is located directly below the exhaust port 22 between the center line C1 passing through the shaft center of the cylinder 21a and the center line C3 passing through the shaft center of the second piping portion 64. There is. Therefore, the catalyst 50 can be arranged as close to the exhaust port 22 as possible.

Further, since the first piping portion 62, the first bent portion 61, and the second bent portion 63 are composed of two divided bodies, the two divided bodies are formed in advance by press working or the like, and then the first piping portion 62, The first bent portion 61 and the second bent portion 63 can be formed.

In particular, the first bent portion 61 and the second bent portion 63 are divided into two parts by a front-rear split or a vertical split, that is, a plane parallel to the plane that defines each bending direction, so that the straight pipe is bent. The bending radius of the first bent portion 61 and the second bent portion 63 can be reduced as compared with the case of forming the first bent portion 61 and the second bent portion 63. Therefore, the first bent portion 61 and the second bent portion 63 can be subjected to a sharp bending, and the degree of freedom in layout is improved. As a result, it has become possible to form an exhaust pipe 6 having a sharp bend in the vicinity of the exhaust port 22. Therefore, the catalyst 50 can also be arranged closer to the exhaust port 22.

Further, the catalyst 50 is arranged between the cylinder head 21b and the engine suspension bracket 4 in the side view shown in FIG. Therefore, even in the lower suspension type engine 2, the catalyst 50 can be arranged directly under the cylinder head 21b. The catalyst 50 is surrounded by a vehicle body frame 3 in the front, a crankcase 20 in the rear, a cylinder head 21b in the upper part, and an engine suspension bracket 4 in the lower part. As a result, the catalyst 50 can be protected from flying stones, water, and the like without being covered with a special cover, and can be made inconspicuous in appearance.

The upstream sensor 8 is attached to the bent portion of the first bent portion 61 from the left side. Specifically, the nut 80 is welded on the split surface on the left side of the first bent portion 61. By arranging the nut 80 on the split surface, it is easy to secure the seat surface when welding the nut 80. The upstream side sensor 8 is attached so that one end side is screwed into the nut 80 and the tip thereof penetrates into the exhaust pipe 6 (first bent portion 61). As a result, the exhaust gas flowing in the first bent portion 61 can be detected by the upstream sensor 8.

In particular, the tip of the upstream sensor 8 is provided at a position overlapping the exhaust port 22 (flange 60) when viewed from the axial direction of the exhaust port 22. By locating the tip of the upstream sensor 8 so as to face the exhaust port 22 in this way, the upstream sensor 8 can be attached near the exhaust port 22 even if the catalyst 50 is arranged directly under the cylinder head 21b. can. As a result, the early activation of the upstream sensor 8 is promoted, and the detection accuracy of the exhaust gas component is improved.

Further, the upstream side sensor 8 has its axial direction directed to the vehicle width direction, and is arranged coaxially parallel to the axial direction of the catalyst 50. Further, the upstream sensor 8 and the catalyst 50 are arranged so as to sandwich the exhaust port 22 in a plan view. Further, the upstream sensor 8 is arranged directly below the exhaust port 22 within the width of the cylinder head 21b and between the pair of engine suspension brackets 4. Like the catalyst 50, the upstream sensor 8 is surrounded by the vehicle body frame 3 in the front, the crankcase 20 in the rear, the cylinder head 21b in the upper part, and the engine suspension bracket 4 in the lower part. As a result, it is possible to protect the upstream sensor 8 from flying stones, water, etc. without covering it with a dedicated cover, and to make it inconspicuous in appearance.

Further, the catalyst 50 and the upstream sensor 8 are arranged near the pivot portion (tips of the engine suspension portions 23a and 24a). Therefore, the amount of movement of the catalyst 50 and the upstream sensor 8 due to the swing of the engine 2 can be reduced, and interference with peripheral parts can be prevented. In particular, the upstream sensor 8 can facilitate wiring.

The downstream sensor 9 is attached from the right side in the front half of the second piping portion 64. Specifically, the nut 90 is welded to the right side surface of the second piping portion 64. One end side of the downstream sensor 9 is screwed into the nut 90, and the tip is attached so as to penetrate into the second piping portion 64. As a result, the exhaust gas flowing in the second piping portion 64 can be detected by the downstream sensor 9.

Further, the downstream sensor 9 is arranged in front of and below the center of the crankshaft (the center of the cooling fan 28a) in the side view shown in FIG. Further, the downstream side sensor 9 has its axial direction directed in the vehicle width direction and its tip directed inward in the vehicle width direction. That is, the downstream sensor 9 is provided on the opposite side of the center line C1 from the upstream sensor 8. By pointing the tips of the upstream sensor 8 and the downstream sensor 9 both toward the inside of the vehicle in this way, it is possible to arrange the detection unit at the tip of each sensor closer to the exhaust port 22. Therefore, the exhaust gas can be detected on the upstream side of the exhaust as much as possible, and the detection accuracy is improved.

As described above, in the present embodiment, by arranging the two exhaust gas sensors (upstream side sensor 8 and downstream side sensor 9) in the exhaust pipe 6 on the upstream side of the muffler 7, the capacity of the muffler 7 is not reduced. , Exhaust gas can be detected upstream and downstream of the catalyst 50. Therefore, the exhaust gas before being diffused in the muffler 7 can be detected, and the detection accuracy is improved.

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

Further, in the above embodiment, the vehicle body frame 3 is composed of an underbone type frame, but the present invention is not limited to this configuration. The body frame 3 may be, for example, a diamond type or twin spar type frame.

Further, in the above embodiment, the unit swing type engine 2 has been described as an example, but the present invention is not limited to this configuration. The engine may be another type of engine in which the crankcase and the swing arm are made of separate parts.

Further, in the above embodiment, the structure in which the muffler 7 is formed in a cylindrical shape has been described, but the structure is not limited to this structure. The muffler 7 may have, for example, a rectangular cross section or a modified cross section.

Further, in the above embodiment, the first piping portion 62 is formed by connecting the upper and lower split bodies, but the configuration is not limited to this. The first piping portion 62 may be formed of a simple cylindrical pipe.

Further, in the above embodiment, the exhaust pipe 6 is configured to be along the right side of the engine 2, but the configuration is not limited to this. The bending direction of the exhaust pipe 6 can be changed as appropriate. For example, the exhaust pipe 6 may be provided along the left side of the engine 2.

Further, in the above embodiment, the first bent portion 61 is divided into front and rear parts, and the first piping portion 62 and the second bent portion 63 are divided into upper and lower parts, but the present invention is not limited to this configuration and can be changed as appropriate. The first bent portion 61 and the second bent portion 63 may be formed by connecting the divided bodies divided in the directions intersecting in the axial direction, and can be changed according to the bending direction. Further, the first piping portion 62 may be composed of front and rear splits.

Further, in the above embodiment, the downstream sensor 9 is attached from the right side surface of the second piping portion 64, but the configuration is not limited to this. The downstream sensor 9 may be attached from, for example, the right side surface of the second bent portion 63. In this case, it is preferable that the downstream sensor 9 is screwed into the nut 90 by welding the nut 90 on the split surface of the second bent portion 63.

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

Moreover, although the present embodiment and the modified example have been described, as another embodiment of the present invention, the above-described embodiment and the modified example may be combined in whole or in part.

Further, the embodiment of the present invention is not limited to the above-described embodiment, and may be variously modified, replaced, or modified without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way by the advancement of the technology or another technology derived from it, it may be carried out by using that method. Therefore, the scope of claims covers all embodiments that may be included within the scope of the technical idea of the present invention.

As described above, the present invention has the effect of improving the exhaust gas purification performance and arranging the exhaust gas sensor without impairing the detection accuracy of the exhaust gas component, and is particularly applicable to motorcycles. It is useful for the arrangement structure of the exhaust gas sensor.

1 Motorcycle 2 Engine 20 Crankcase 21a Cylinder 21b Cylinder head 22 Exhaust port 3 Body frame (frame)
4 Engine suspension bracket (bracket)
50 Catalyst 6 Exhaust pipe (exhaust pipe)
61 1st bent part 62 1st piping part 63 2nd bent part 64 2nd piping part 8 Upstream side sensor (1st exhaust gas sensor)
9 Downstream sensor (second exhaust gas sensor)

Claims (10)

An engine with a cylinder and cylinder head located in front of the crankcase,
An exhaust pipe attached to the exhaust port of the cylinder head and
A catalyst placed in the middle of the exhaust pipe and
A first exhaust gas sensor attached to the exhaust pipe on the upstream side of the catalyst is provided.
The axis of the cylinder is oriented substantially horizontally, and the exhaust port is provided below the cylinder head.
The exhaust pipe has a first piping portion extending in the vehicle width direction below the cylinder head.
The catalyst is arranged in the first piping portion so that the axial direction faces the vehicle width direction .
It said first exhaust gas sensor, the arrangement of the exhaust gas sensor, wherein Rukoto arranged coaxially in parallel to the axial direction of the catalyst. An engine with a cylinder and cylinder head located in front of the crankcase,
An exhaust pipe attached to the exhaust port of the cylinder head and
A catalyst placed in the middle of the exhaust pipe and
A first exhaust gas sensor attached to the exhaust pipe on the upstream side of the catalyst is provided.
The axis of the cylinder is oriented substantially horizontally, and the exhaust port is provided below the cylinder head.
The exhaust pipe has a first piping portion extending in the vehicle width direction below the cylinder head.
The catalyst is arranged in the first piping portion so that the axial direction faces the vehicle width direction.
It said first exhaust gas sensor and the catalyst, the arrangement of the exhaust gas sensor you being disposed so as to sandwich the exhaust port in a plan view. An engine with a cylinder and cylinder head located in front of the crankcase,
An exhaust pipe attached to the exhaust port of the cylinder head and
A catalyst placed in the middle of the exhaust pipe and
A first exhaust gas sensor attached to the exhaust pipe on the upstream side of the catalyst is provided.
The axis of the cylinder is oriented substantially horizontally, and the exhaust port is provided below the cylinder head.
The exhaust pipe has a first piping portion extending in the vehicle width direction below the cylinder head.
The catalyst is arranged in the first piping portion so that the axial direction faces the vehicle width direction.
A second exhaust gas sensor attached to the exhaust pipe on the downstream side of the catalyst is further provided.
The second exhaust gas sensor is arranged forward and below the center of the crankshaft .
The second exhaust gas sensor is arranged on the opposite side of the first exhaust gas sensor with the cylinder in between.
Arrangement of the exhaust gas sensor, wherein a distal end of said first exhaust gas sensor and said second exhaust gas sensor is both inward. The exhaust pipe has a first bent portion that bends the exhaust flow path on the upstream side of the first piping portion.
The arrangement structure of the exhaust gas sensor according to any one of claims 1 to 3, wherein the first bent portion is formed by connecting the divided bodies divided in the directions intersecting in the axial direction. Further equipped with a bracket for suspending the engine on the frame,
The bracket is provided below the cylinder head and
The arrangement structure of an exhaust gas sensor according to any one of claims 1 to 4, wherein the catalyst is arranged between the cylinder head and the bracket. The first exhaust gas sensor is attached to the first bent portion and is attached to the first bent portion.
The arrangement structure of the exhaust gas sensor according to claim 4 , wherein the tip of the first exhaust gas sensor overlaps the exhaust port when viewed from the axial direction of the exhaust port. The arrangement structure of the exhaust gas sensor according to any one of claims 1 to 6 , wherein the first exhaust gas sensor is arranged immediately below the exhaust port and within the width of the cylinder head. A pair of the brackets are provided side by side in the vehicle width direction.
The arrangement structure of the exhaust gas sensor according to claim 5 , wherein the first exhaust gas sensor is arranged directly under the exhaust port and between the pair of brackets. The exhaust pipe
A second bent portion that bends the exhaust flow path on the downstream side of the first piping portion, and a second bent portion.
It has a second piping portion connected to the downstream side of the second bending portion, and has.
The second bent portion is formed by joining the divided bodies divided in the directions intersecting in the axial direction.
The arrangement structure of the exhaust gas sensor according to claim 3, wherein the second exhaust gas sensor is attached to the second bent portion or the second piping portion. A motorcycle comprising the arrangement structure of the exhaust gas sensor according to any one of claims 1 to 9.

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