JP2017206999A - Exhaust gas sensor arrangement structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arrange an exhaust gas sensor before and behind a catalyst without impairing detection accuracy.SOLUTION: An exhaust gas sensor arrangement structure includes a cylinder (21) the axial direction of which is inclined to the front side, a crankcase (20) provided behind the cylinder, a floor tunnel (12) covering the cylinder and the crankcase, a passenger foot board (14) on which a crew's foot is put, a catalyst (8) for purifying exhaust gas from an engine (2), and an exhaust gas sensor (9) for performing the deterioration determination of the catalyst. The passenger foot board is provided extending from each vehicle-cross-direction end side of the floor tunnel in the longitudinal direction, the catalyst is arranged on the lateral side of the crankcase below the passenger foot board, and the exhaust gas sensor is arranged below the passenger foot board before and behind the catalyst.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an arrangement structure of exhaust gas sensors.

  In an automobile, it is obliged to monitor the exhaust gas control status with an in-vehicle computer. As an item to be monitored, for example, a deterioration state of a catalyst that purifies exhaust gas can be cited (see Patent Document 1). In Patent Document 1, oxygen sensors are provided before and after the catalyst, respectively, and it is determined whether the catalyst has deteriorated based on the output values of these two oxygen sensors.

  Specifically, the number of output inversions between the rich leans of the two oxygen sensors is used. For example, when the catalyst is normal and can sufficiently adsorb oxygen, the number of output inversions of the downstream oxygen sensor approaches zero. For this reason, the ratio of the number of output reversals of the upstream oxygen sensor with respect to the downstream side is increased. On the other hand, when the catalyst deteriorates and the oxygen adsorption capacity decreases, the output reversal count of the downstream oxygen sensor approaches the output reversal count of the upstream oxygen sensor. For this reason, the ratio of the number of output inversions of the upstream oxygen sensor with respect to the downstream side becomes small. Therefore, it can be determined that the catalyst has deteriorated when the above ratio falls below a predetermined value.

JP 2003-206784 A

  By the way, when determining deterioration of a catalyst in a motorcycle, it is difficult to arrange two oxygen sensors before and after the catalyst while ensuring detection accuracy due to restrictions on the structure and layout of the exhaust pipe and muffler.

  The present invention has been made in view of this point, and an object thereof is to provide an exhaust gas sensor arrangement structure in which exhaust gas sensors can be arranged in front of and behind a catalyst without impairing detection accuracy.

  The exhaust gas sensor arrangement structure according to the present invention includes a cylinder whose axial direction is inclined forward, an engine case provided behind the cylinder, a floor tunnel covering the cylinder and the engine case, and a passenger's foot. A footboard, a catalyst for purifying the exhaust gas of the engine, and an exhaust gas sensor for detecting an exhaust gas component of the engine, wherein the footboard is front and rear at both ends in the vehicle width direction of the floor tunnel. The catalyst is disposed on the side of the engine case and below the footboard, and the exhaust gas sensor is disposed on the front and back of the catalyst below the footboard. And

  According to this configuration, the exhaust gas sensor can be disposed close to the catalyst before and after the catalyst by disposing the catalyst in the space below the footboard. For this reason, it is possible to appropriately determine the deterioration of the catalyst without impairing the detection accuracy of the exhaust gas sensor.

  Moreover, in the arrangement structure of the exhaust gas sensor according to the present invention, it is preferable that the exhaust gas sensor is arranged on the inner side in the vehicle width direction from the end portion of the foot board in the vehicle width direction. According to this configuration, it is possible to prevent the exhaust gas sensor from protruding outward in the vehicle width direction from the footboard. Therefore, the exhaust gas sensor can be protected from contact during boarding, flying stones during traveling, and the like. Further, the cover for protecting the exhaust gas sensor can be omitted, and the configuration can be simplified.

  The exhaust gas sensor arrangement structure according to the present invention includes a catalyst case that houses the catalyst, a muffler that extends rearward from the rear end of the catalyst case, and a rearward extension from the rear end of the engine case. A swing arm, and the exhaust gas sensor includes an upstream sensor provided on the upstream side of the catalyst, and a downstream sensor provided on the downstream side of the catalyst. It is preferable that the catalyst case, the muffler, the swing arm, and the footboard are disposed in a space surrounded by the catalyst case and attached to the catalyst case. According to this configuration, even if the downstream sensor is disposed at a position where it is easily exposed to the outside, the downstream sensor can be protected from flying stones and the like while traveling without being damaged by surrounding structure. it can.

  In the exhaust gas sensor arrangement structure according to the present invention, the footboard includes a driver's footboard and a passenger's footboard provided behind the driver's footboard, and the driver Preferably, the passenger footboard and the passenger footboard are provided independently, and the passenger footboard is provided above the driver footboard. According to this configuration, since the driver's footboard and the passenger's footboard are separately provided, the degree of freedom of the arrangement position of the passenger's footboard is increased. Further, since the passenger footboard is provided above the driver footboard, a space below the passenger footboard can be secured. As a result, it is possible to easily arrange the catalyst and the exhaust gas sensor in the space.

  The exhaust gas sensor arrangement structure according to the present invention further includes a fixing portion for fixing the catalyst case to the engine case, and the fixing portion is sandwiched between the upstream sensor and the downstream sensor. It is preferable to be provided at a position. According to this configuration, the space between the upstream sensor and the downstream sensor can be effectively utilized by sandwiching the fixed portion between the upstream sensor and the downstream sensor. Further, since the vicinity of the exhaust gas sensor is fixed by the fixing portion, vibration of the exhaust gas sensor is suppressed.

  According to the present invention, the exhaust gas sensors can be disposed before and after the catalyst without impairing the detection accuracy.

1 is a right side view showing a schematic configuration of a motorcycle to which an exhaust gas sensor arrangement structure according to the present embodiment is applied. 1 is a perspective view of a motorcycle to which an exhaust gas sensor arrangement structure according to the present embodiment is applied as viewed from the right rear. 1 is a right side view showing a configuration around an engine of a motorcycle according to the present embodiment. 1 is a top view showing a configuration around an engine of a motorcycle according to the present embodiment. It is an enlarged view which shows the arrangement structure of the exhaust gas sensor which concerns on this Embodiment. It is the enlarged view which looked at the periphery structure of the catalyst which concerns on this Embodiment from the downward direction. It is sectional drawing which follows the AA line 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 large scooter type motorcycle will be described, but the application target is not limited to this and can be changed. For example, the exhaust gas sensor arrangement structure according to the present invention may be applied to other types of motorcycles, buggy type motorcycles, automobiles, and the like. Regarding the direction, the front of the vehicle is indicated by an arrow FR, and the rear of the vehicle is indicated by an arrow RE. In the following drawings, a part of the configuration is omitted for convenience of explanation.

  With reference to FIGS. 1 and 2, a schematic configuration of a motorcycle to which the exhaust gas sensor arrangement structure according to the present embodiment is applied will be described. FIG. 1 is a right side view showing a schematic configuration of a motorcycle to which an exhaust gas sensor arrangement structure according to the present embodiment is applied. FIG. 2 is a perspective view of a motorcycle to which the exhaust gas sensor arrangement structure according to the present embodiment is applied as viewed from the right rear.

  As shown in FIGS. 1 to 2, a large scooter type motorcycle 1 is configured by suspending an engine 2 on an underbone body frame (not shown). The engine 2 is composed of, for example, a parallel 2-cylinder engine. In particular, the present embodiment employs a unit swing type engine in which the engine 2, the transmission (CVT unit 27 described later) and the transmission mechanism (the final gear case 40 described later) to the rear wheel 36 are integrated with the swing arm. Yes. The peripheral configuration of the engine 2 and the transmission will be described later.

  Various covers as a vehicle body exterior are mounted on the vehicle body frame and the engine 2. Specifically, a front cowl 11 is provided on the front side of the vehicle. A floor tunnel 12 that covers the engine 2 is provided behind the front cowl 11. The floor tunnel 12 has a cross-sectional arch shape (not shown) and extends rearward.

  Further, on the back side of the front cowl 11, a driver's footboard 13 and a passenger's footboard 14 are provided for placing the passenger's feet. The driver's foot board 13 and the passenger's foot board 14 are provided in pairs so as to sandwich the floor tunnel 12 between the left and right sides. The driver's footboard 13 and the passenger's footboard 14 are formed to be connected to the left and right ends of the floor tunnel 12. Specifically, the driver footboard 13 and the passenger footboard 14 are formed so as to protrude outward in the vehicle width direction from both lower ends of the floor tunnel 12 and extend in the front-rear direction.

  The driver footboard 13 extends rearward and downward along the shape of the front cowl 11, then bends in the horizontal direction, and further extends rearward. The passenger footboard 14 is provided independently of the driver footboard 13 and extends rearward slightly above the driver footboard 13. Although details will be described later, air for introducing air into the belt cooling duct 29 of the CVT unit 27 (both see FIGS. 3 and 4) on the side surface of the floor tunnel 12 at the front upper side of the passenger footboard 14. An introduction port 12a is formed.

  A rider seat 15 and a pillion seat 16 are provided behind the floor tunnel 12 and above the CVT unit 27 so as to extend rearward and upward. A seat cowl 17 is provided below the rider seat 15 and the pillion seat 16. The seat cowl 17 extends rearward and upward so as to be continuous with the floor tunnel 12. A backrest 18 and a grab bar 19 are provided on the rear side of the pillion seat 16.

  On the front side of the vehicle, a pair of left and right front forks 30 are supported so as to be steerable via a steering shaft (not shown) provided on a head pipe (not shown). A handle 31 is provided above the front fork 30. A front wheel 32 is rotatably supported at a lower portion of the front fork 30, and an upper portion of the front wheel 32 is covered with a front fender 33. A headlamp 34 is provided on the front surface of the front cowl 11, and a windscreen 35 for windbreak is provided above the headlamp 34.

  The swing arm unit 4 provided on the rear side of the engine 2 extends rearward from the passenger footboard 14. The swing arm unit 4 is configured to be swingable up and down, and a rear suspension (not shown) is provided between the swing arm unit 4 and the vehicle body frame. A rear wheel 36 is rotatably supported at the rear end of the swing arm unit 4. The rear upper part of the rear wheel 36 is covered with a rear fender 37. The details of the swing arm unit 4 will be described later.

  An exhaust pipe 6 and a muffler 7 are connected to each exhaust port of the engine 2 as an exhaust system. A plurality of exhaust pipes 6 (two in the present embodiment) extend downward from each exhaust port, bend rearward at the front lower side of the engine 2, and then are combined into one. A catalyst 8 for purifying exhaust gas is provided at the downstream end of the exhaust pipe 6.

  The catalyst 8 is made of, for example, a three-way catalyst and is accommodated in a cylindrical catalyst case 80. The catalyst 8 converts pollutants (carbon monoxide, hydrocarbons, nitrogen oxides, etc.) in the exhaust gas into harmless substances (carbon dioxide, water, nitrogen, etc.). The muffler 7 is connected to the downstream side of the catalyst 8 via a connecting pipe 70 (see FIG. 3). The muffler 7 extends rearward and upward along the seat cowl 17. A muffler cover 71 that protects the muffler 7 is attached to the outer surface of the muffler 7. The muffler cover 71 has a length from the rear side of the muffler 7 to the rear half of the catalyst case 80.

  Exhaust gas generated by the combustion of the engine 2 is purified by the catalyst 8 through the exhaust pipe 6. Then, after the exhaust noise is reduced by the muffler 7, the exhaust gas is discharged outside.

  Although details will be described later, an exhaust gas sensor 9 for detecting an exhaust gas component of the engine and determining deterioration of the catalyst 8 is disposed before and after the catalyst 8. Specifically, the exhaust gas sensor 9 includes an upstream sensor 90 provided on the front side (upstream side) of the catalyst 8 and a downstream sensor 91 provided on the rear side (downstream side) of the catalyst 8. The exhaust gas sensor 9 is composed of, for example, a zirconia oxygen sensor, and the output (current value) changes according to the oxygen concentration in the exhaust gas. The current value is output to the ECU 10 (Electronic Control Unit). The exhaust gas sensor 9 is not limited to an oxygen sensor, and may be an air-fuel ratio sensor, for example.

  The ECU 10 performs overall control of various operations in the motorcycle 1. The ECU 10 includes a processor, 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) according to the application. The memory stores a control program for controlling each part of the motorcycle 1. In particular, in the present embodiment, the ECU 10 determines the deterioration of the catalyst 8 based on the output of the exhaust gas sensor 9. For example, the deterioration of the catalyst 8 is determined based on the ratio of the number of output inversions between the rich lean of the upstream sensor 90 and the downstream sensor 91. In order to determine the deterioration of the catalyst 8, the output difference between the upstream sensor 90 and the downstream sensor 91 may be used without being limited to the case of using the ratio of the number of output inversions.

  Next, the peripheral configuration of the engine according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a right side view showing the engine peripheral configuration of the motorcycle according to the present embodiment. FIG. 4 is a top view showing an engine peripheral configuration of the motorcycle according to the present embodiment.

  As shown in FIGS. 3 and 4, the engine 2 includes a cylinder 21, a cylinder head 22, and a cylinder head cover 23 in this order in front of a crankcase 20 that houses various components such as a crankshaft (not shown). Installed and configured. The cylinder 21 is arranged such that the axial direction is inclined forward. Specifically, the axial direction of the cylinder 21 is directed to a direction (substantially horizontal direction) in which the front side is slightly higher than the horizontal direction.

  The crankcase 20 extends in the front-rear direction and is configured to be divided into left and right. A magnet cover 24 and a clutch cover 25 are provided on the left side surface of the crankcase 20 from the front. A starter clutch cover 26 is provided on the front side of the right side surface of the crankcase 20. Further, a CVT unit 27 as a transmission is provided on the right rear side of the crankcase 20.

  The CVT unit 27 is a so-called belt-type continuously variable transmission, and includes a primary pulley and a secondary pulley (both not shown) housed in a CVT case 28. A drive belt (not shown) is wound around the primary pulley and the secondary pulley. The CVT unit 27 changes speed by changing the winding radius of the drive belt. In the present embodiment, the crankcase 20 and the CVT case 28 are collectively referred to as an engine case.

  A belt cooling duct 29 is attached to the right side surface of the CVT case 28. The belt cooling duct 29 is provided at a position corresponding to the air inlet 12a (see FIG. 1) formed in the floor tunnel 12. Outside air is introduced into the belt cooling duct 29 from the air inlet, and the outside air is supplied to the drive belt through the belt cooling duct 29, whereby the drive belt is cooled.

  A swing arm unit 4 is provided at the rear end of the crankcase 20 and extends rearward in a substantially horizontal direction. The swing arm unit 4 is composed of a final gear case 40 that is arranged to be deviated toward the left side of the vehicle and a right swing arm 41 that is arranged to be deviated to the right side of the vehicle. In the final gear case 40, various gears for transmitting power to the rear wheel 36 are accommodated side by side. As described above, the rear wheel 36 is rotatably provided at the rear end of the swing arm unit 4 (the final gear case 40 and the right swing arm 41).

  In the shaft arrangement of the unit swing type engine configured as described above, as shown in FIG. 4, the axis C2 of the primary pulley is located behind the axis C1 of the crankshaft. The secondary pulley axis C3 is located behind the axis C2. The axis C3 is coaxial with the clutch axis. The axis C4 of the final drive gear is located behind the axis C3. The axis C4 is coaxial with the swing center (pivot shaft) of the swing arm unit 4. The axis C5 of the final driven gear (the center of rotation of the rear wheel 36) is located behind the axis C4.

  By the way, in a motorcycle exhaust system, it is required to monitor a deterioration state of a 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 heretofore been practiced to detect the oxygen concentration in the exhaust gas with an exhaust gas sensor (oxygen sensor) provided upstream of the catalyst and control the air-fuel ratio. However, if an exhaust gas sensor is arranged 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 a layout restriction unique to the motorcycle. It was difficult.

  In this regard, in an automobile, since the catalyst can be arranged in a space where there is enough space, such as in the engine room, it is easy to arrange and protect the exhaust gas sensor. On the other hand, in a motorcycle, a catalyst is often arranged in a chamber or a muffler, and it is difficult to arrange the downstream sensor close to the catalyst because of the structure. Even when a 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. Furthermore, since the exhaust system of the motorcycle is exposed to the outside, it may be assumed that the temperature of the catalyst is likely to decrease, for example, during winter or rainy weather, and sensor output cannot be obtained appropriately. Also, protection of the exhaust gas sensor becomes a problem.

  For example, when a catalyst is provided in a chamber or a muffler, it can be considered that the outer wall is recessed to secure a space for arranging the exhaust gas sensor. However, as a result of the volume of the chamber and muffler being reduced, the original function (output increase and noise reduction) may be affected. Although it is conceivable to arrange the catalyst itself on the front side of the vehicle, it is difficult to secure the catalyst arrangement space in the first place, and it is not practical because it requires a significant design change. Furthermore, 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 an exhaust gas sensor, and deterioration in appearance design occur.

  Accordingly, the present inventor has conceived the present invention by paying attention to a limited space below a footboard (especially a passenger's footboard 14) on which a rider can put his / her foot in the large scooter type motorcycle 1. . Specifically, in the present embodiment, two exhaust gas sensors are arranged so that the catalyst 8 is disposed below the passenger footboard 14 on the right side of the engine case (crankcase 20), and the catalyst 8 is sandwiched between the catalyst 8 and the catalyst 8. 9 (upstream sensor 90 and downstream sensor 91) are arranged.

  According to this configuration, the exhaust gas sensor 9 can be disposed close to the catalyst 8 before and after the catalyst 8 by disposing the catalyst 8 below the passenger footboard 14. In particular, the downstream sensor 91 can be brought closer to the catalyst 8 by disposing the downstream sensor 91 in a relatively roomy space below the passenger footboard 14. By disposing the downstream sensor 91 immediately after the catalyst 8, the purified exhaust gas directly contacts the downstream sensor 91 without being diffused. As a result, an output can be stably obtained, and the detection accuracy of the exhaust gas sensor 9 is not impaired. Thus, by effectively utilizing the space below the passenger footboard 14, the exhaust gas sensor 9 can be disposed without requiring a significant design change and without affecting the appearance design. Became. Furthermore, by providing the catalyst 8 near the engine 2, it is possible to suppress the temperature drop of the catalyst 8, and to suppress the exhaust gas purification effect from deteriorating or affecting the sensor output. . Therefore, it is possible to appropriately determine the deterioration of the catalyst 8.

  Next, the exhaust system according to the present embodiment will be described in detail with reference to FIGS. FIG. 5 is an enlarged view showing an arrangement structure of the exhaust gas sensor according to the present embodiment. FIG. 6 is an enlarged view of the peripheral configuration of the catalyst according to the present embodiment as viewed from below. FIG. 7 is a cross-sectional view taken along the line AA of FIG.

  As shown in FIG. 3 to FIG. 6, in the exhaust system according to the present embodiment, the exhaust pipe 6 includes two exhaust pipes 6 a and 6 b that extend downward from the exhaust ports of the cylinder head 22. It is configured as one (see particularly FIG. 6).

  The exhaust pipes 6 a and 6 b are bent backward at the front lower side of the crankcase 20. A collecting pipe 60 is connected to the rear ends of the exhaust pipes 6a and 6b. The collecting pipe 60 is formed in a cylindrical shape by welding the upper half and the lower half, and extends rearward and upward. The catalyst 8 accommodated in the catalyst case 80 is connected to the rear end of the collecting pipe 60. As shown in FIG. 5, the catalyst 8 is disposed below the air inlet 12 a and below the passenger footboard 14. The catalyst 8 is formed in a columnar shape, and is disposed slightly biased to the front side (a straight portion 81 described later) in the catalyst case 80.

  The catalyst case 80 is formed in a cylindrical shape by welding the upper half and the lower half, and extends rearward. Specifically, the catalyst case 80 extends horizontally corresponding to the length of the catalyst 8 (referred to as a straight portion 81), then bends slightly upward and extends backward (referred to as a bent portion 82). A fixing portion 83 for fixing the catalyst case 80 to the CVT case 28 is provided on the outer surface of the upper half of the catalyst case 80. The fixing portion 83 is located directly above the catalyst 8 (straight portion 81), and is attached to the CVT case 28 via a vibration isolating member (not shown). The muffler 7 is connected to the rear end of the catalyst case 80 via a connecting pipe 70.

  Further, as described above, the exhaust gas sensor 9 is disposed before and after the catalyst 8. The exhaust gas sensor 9 is formed in a cylindrical shape having a predetermined length. One end side of the exhaust gas sensor 9 serves as a detection unit, and wiring (not shown) is connected to the other end side.

  Specifically, the upstream sensor 90 is attached so that one end side penetrates into the collecting pipe 60 at a substantially center in the front-rear direction of the upper half of the collecting pipe 60. The other end side of the upstream sensor 90 is slightly inclined forward. The upstream sensor 90 is provided between the primary pulley and the secondary pulley of the CVT unit 27 (between the axis C2 and the axis C3) below the air inlet 12a (belt cooling duct 29).

  The downstream sensor 91 is attached immediately after the catalyst 8 so that one end side penetrates into the catalyst case 80. Specifically, the downstream sensor 91 is disposed in the upper half of the bent portion 82, and the other end side is slightly inclined forward. Further, the downstream sensor 91 is provided at a position higher than the upstream sensor 90 behind the drive shaft (final drive gear axis C4).

  As shown in FIG. 5, the downstream sensor 91 is disposed in a space surrounded by the catalyst case 80, the muffler 7, the right swing arm 41, and the passenger footboard 14. Therefore, even if the downstream sensor 91 is disposed at a place where it is easily exposed to the outside, the downstream sensor 91 can be protected from a flying stone or the like while traveling without being impaired by being surrounded by the peripheral configuration.

  In particular, as described with reference to FIG. 1, the muffler cover 71 extends to the latter half of the catalyst case 80. Specifically, the muffler cover 71 covers not only the muffler 7 but also the connecting pipe 70 and the bent portion 82 of the catalyst case 80. Thereby, since the downstream sensor 91 provided in the bending part 82 is also covered with the muffler cover 71, the downstream sensor 91 can be more effectively protected from flying stones, rainwater, and the like.

  In addition, since the fixing portion 83 that fixes the catalyst case 80 to the CVT case 28 is sandwiched between the upstream sensor 90 and the downstream sensor 91, the space between the upstream sensor 90 and the downstream sensor 91 is increased. It can be used effectively. Further, since the vicinity of the downstream sensor 91 is fixed by the fixing portion 83, the vibration of the downstream sensor 91 is suppressed. Further, since the vibration isolating member (not shown) is provided in the fixed portion 83, the vibration of the vehicle is hardly transmitted to the downstream sensor 91.

  Further, as shown in FIGS. 6 and 7, the downstream sensor 91 is disposed on the inner side in the vehicle width direction from the end portion in the vehicle width direction of the passenger footboard 14. According to this configuration, it is possible to prevent the downstream sensor 91 from protruding outward from the passenger footboard 14 in the vehicle width direction. Can be protected. As shown in FIG. 4, the upstream sensor 90 is disposed on the inner side in the vehicle width direction than the end of the belt cooling duct 29, and thus can be disposed further on the inner side than the downstream sensor 91. Therefore, it is not necessary to provide a protective cover dedicated to the upstream sensor 90, and the configuration can be simplified.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, the upstream sensor 90 is disposed in the collecting pipe 60 immediately before the catalyst 8, but the present invention is not limited to this configuration. The upstream sensor 90 may be arranged at any position as long as it is upstream from the catalyst 8. For example, one upstream sensor 90 may be arranged in each exhaust pipe 6 a, 6 b in front of the engine 2.

  In the embodiment described above, the single catalyst 8 is provided. However, the present invention is not limited to this configuration. The catalyst 8 may be composed of a plurality of catalysts (for example, a sub catalyst and a main catalyst). For example, in order to establish a layout when the capacity of the catalyst is further required, a sub catalyst for determining catalyst deterioration is arranged in the middle of the exhaust pipe, and a main catalyst for exhaust gas purification is arranged in the muffler. Also good. Further, both the sub catalyst and the main catalyst may be arranged in the middle of the exhaust pipe. In these cases, it is preferable to arrange the exhaust gas sensors 9 before and after the sub catalyst.

  In the above-described embodiment, the axial direction of the cylinder 21 is inclined forward in a substantially horizontal direction. However, the present invention is not limited to this configuration. The axial direction of the cylinder 21 can be arbitrarily changed.

  In the above-described embodiment, the parallel two-cylinder engine 2 has been described as an example. However, the present invention is not limited to this configuration. The engine 2 may be a single cylinder or three or more cylinders.

  In the above-described embodiment, the driver footboard 13 and the passenger footboard 14 are provided independently, and the passenger footboard 14 is provided above the driver footboard 13. Explains the case. According to this configuration, the driver's footboard 13 and the passenger's footboard 14 are provided separately, so that the degree of freedom of the arrangement position of the passenger's footboard 14 is increased. Further, since the passenger footboard 14 is provided above the driver footboard 13, a space below the passenger footboard 14 can be secured. As a result, the catalyst 8 and the exhaust gas sensor 9 can be easily arranged in the space. However, it is not limited to this configuration and can be changed as appropriate. For example, the driver footboard 13 and the passenger footboard 14 may be integrally formed, or the driver footboard 13 and the passenger footboard 14 may be arranged at the same height.

  As described above, the present invention has an effect that exhaust gas sensors can be arranged before and after the catalyst without impairing detection accuracy, and is particularly useful for an arrangement structure of exhaust gas sensors.

1 Motorcycle 12 Floor tunnel 13 Driver's footboard (footboard)
14 Passenger footboard (footboard)
2 Engine 20 Crankcase (Engine case)
21 cylinder 28 CVT case (engine case)
4 Swing arm unit (swing arm)
40 Final gear case (swing arm)
41 Right swing arm (swing arm)
7 Muffler 8 Catalyst 80 Catalyst case 83 Fixed part 9 Exhaust gas sensor 90 Upstream sensor 91 Downstream sensor

Claims (5)

A cylinder whose axial direction is tilted forward,
An engine case provided behind the cylinder;
A floor tunnel covering the cylinder and the engine case;
A footboard to put the passenger's feet,
A catalyst for purifying engine exhaust gas,
An exhaust gas sensor for detecting an exhaust gas component of the engine,
The footboard is provided so as to extend back and forth at both ends in the vehicle width direction of the floor tunnel,
The catalyst is disposed on the side of the engine case and below the footboard,
The exhaust gas sensor is disposed below and in front of the catalyst below the footboard.   2. The exhaust gas sensor arrangement structure according to claim 1, wherein the exhaust gas sensor is arranged on an inner side in a vehicle width direction than an end portion of the foot board in the vehicle width direction. A catalyst case containing the catalyst;
A muffler extending rearward from the rear end of the catalyst case;
A swing arm extending rearward from the rear end of the engine case,
The exhaust gas sensor has an upstream sensor provided on the upstream side of the catalyst, and a downstream sensor provided on the downstream side of the catalyst,
The said downstream sensor is arrange | positioned in the space enclosed by the said catalyst case, the said muffler, the said swing arm, and the said foot board, and is attached to the said catalyst case. Structure of exhaust gas sensor. The footboard has a driver's footboard and a passenger's footboard provided behind the driver's footboard,
The driver footboard and the passenger footboard are provided independently of each other,
The exhaust gas sensor arrangement structure according to claim 3, wherein the passenger footboard is provided above the driver footboard. A fixing portion for fixing the catalyst case to the engine case;
The exhaust gas sensor arrangement structure according to claim 3 or 4, wherein the fixing portion is provided at a position sandwiched between the upstream sensor and the downstream sensor.

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