JP2020169589A - Motor cycle - Google Patents

Abstract

To facilitate temperature rising of an exhaust gas sensor to early activate the exhaust gas sensor.SOLUTION: A motor cycle includes: a cylinder 32; a cylinder head 33 coupled to the cylinder 32 from the front and provided with an exhaust port 43; an exhaust pipe 51 connected to the exhaust port 43; an exhaust gas sensor 52 attached to the exhaust pipe 51; and an engine cover 11 covering the cylinder 32 and the cylinder head 33. The exhaust pipe 51 includes: a first pipe part 57 extending downward from the exhaust port 43; a second pipe part 58 extending from the first pipe part 57 to the outer side in a vehicle width direction; and a third pipe part 59 extending rearward from the second pipe part 58. The exhaust gas sensor 52 is disposed below the cylinder 32 and is attached to the first pipe part 57 so that a tip part 52a is oriented to the rear. In the engine cover 11, a cutout part 75 is provided in an area where the cylinder 32 and the exhaust gas sensor 52 are overlapped in a vehicle lower surface view.SELECTED DRAWING: Figure 3

Description

The present invention relates to a motorcycle.

Conventionally, a motorcycle is provided with an exhaust gas sensor that detects the oxygen concentration of the exhaust gas flowing in the exhaust pipe, and fuel injection control of the engine is executed based on the oxygen concentration of the exhaust gas detected by the exhaust gas sensor. In recent years, as exhaust gas regulations have become stricter, it is required to improve the detection accuracy of the exhaust gas sensor. In order to meet such demands, the exhaust gas sensor is placed upstream of the exhaust pipe, and the high temperature exhaust gas immediately after being discharged from the engine promotes the temperature rise of the exhaust gas sensor to activate the exhaust gas sensor at an early stage. It is important to let them do it.

For example, in the motorcycle described in Patent Document 1, an oxygen sensor is attached to an exhaust pipe arranged upstream of the first catalyst and connected to an exhaust port.

Japanese Patent No. 4555710

When the exhaust gas sensor is arranged upstream of the exhaust pipe as described above, if the traveling wind hits the exhaust gas sensor, the exhaust gas sensor is cooled by the traveling wind. When the exhaust gas sensor is cooled by the running wind in this way, the temperature rise of the exhaust gas sensor is delayed by that amount, and it becomes difficult to activate the exhaust gas sensor at an early stage.

Further, when the engine is covered with the engine cover, if the radiant heat from the engine to the exhaust gas sensor is blocked by the engine cover, the exhaust gas sensor cannot be heated by the radiant heat from the engine. Along with this, the temperature rise of the exhaust gas sensor is delayed, and it becomes difficult to activate the exhaust gas sensor at an early stage.

Therefore, an object of the present invention is to promote the temperature rise of the exhaust gas sensor and to activate the exhaust gas sensor at an early stage.

The motorcycle according to the present invention is connected to an engine case accommodating a crank shaft, a cylinder connected to the engine case from the front, a cylinder head connected to the cylinder from the front and provided with an exhaust port, and the exhaust port. The exhaust pipe is provided with an exhaust pipe to be formed, an exhaust gas sensor attached to the exhaust pipe, an engine cover covering the cylinder and the cylinder head, and the exhaust pipe includes a first piping portion extending downward from the exhaust port. A second piping portion extending outward in the vehicle width direction from the first piping portion and a third piping portion extending rearward from the second piping portion are provided, and the exhaust gas sensor is arranged below the cylinder. The engine cover is attached to the first piping portion so that the tip portion faces rearward, and the engine cover is provided with a notch at a position where the cylinder and the exhaust gas sensor overlap when viewed from the bottom of the vehicle. It is a feature.

According to the present invention, it is possible to promote the temperature rise of the exhaust gas sensor and activate the exhaust gas sensor at an early stage.

It is a right side view which shows the motorcycle which concerns on one Example of this invention. It is a right side view which shows the engine which concerns on one Example of this invention and its periphery. It is a bottom view which shows the front part of the engine which concerns on one Example of this invention, and its periphery. It is a front view which shows the front part of the engine which concerns on one Example of this invention, and its periphery. It is a left side view which shows the front part of the engine which concerns on one Example of this invention, and its periphery.

In the motorcycle according to the embodiment of the present invention, the exhaust gas sensor is attached to the first piping portion. By adopting such a configuration, the exhaust gas sensor can be arranged upstream of the exhaust pipe. Therefore, the temperature rise of the exhaust gas sensor can be promoted by the high-temperature exhaust gas immediately after being discharged from the exhaust port of the cylinder head, and the exhaust gas sensor can be activated at an early stage.

Further, in the motorcycle according to the embodiment of the present invention, the exhaust gas sensor is attached to the first piping portion so that the tip portion faces rearward. By adopting such a configuration, the traveling wind toward the exhaust gas sensor is blocked by the first piping portion, so that it is possible to suppress the exhaust gas sensor from being cooled by the traveling wind. Therefore, the temperature rise of the exhaust gas sensor can be further promoted, and the exhaust gas sensor can be activated at an earlier stage.

Further, in the motorcycle according to the embodiment of the present invention, the engine cover is provided with a notch at a position where the cylinder and the exhaust gas sensor overlap when viewed from the bottom of the vehicle. By adopting such a configuration, the exhaust gas sensor can be heated by the radiant heat from the cylinder to the exhaust gas sensor. Therefore, the temperature rise of the exhaust gas sensor can be further promoted, and the exhaust gas sensor can be activated at an earlier stage.

(Motorcycle 1)
Hereinafter, a scooter-type motorcycle 1 according to an embodiment of the present invention will be described with reference to the drawings. Hereinafter, terms indicating directions such as front-back, up-down, left-right, etc. are used with reference to the direction seen from the rider of the motorcycle 1. The arrows Fr, Rr, U, Lo, L, and R appropriately attached to each figure indicate the front, the rear, the upper, the lower, the left, and the right of the motorcycle 1, respectively.

With reference to FIGS. 1 and 2, the motorcycle 1 includes a vehicle body frame 2, a vehicle body cover 3 covering the vehicle body frame 2, a steering mechanism 4 and front wheels 5 arranged in front of the vehicle body frame 2, and a vehicle body frame 2. An engine 6 and a rear wheel 7 arranged below the rear, an intake device 8 and an exhaust device 9 connected to the front part of the engine 6, and a fan cowl covering the right side (outside in the vehicle width direction) of the front part of the engine 6. It is mainly composed of 10 and an engine cover 11 that covers the outer periphery of the front portion of the engine 6. Hereinafter, the components of the motorcycle 1 will be described in order.

(Body frame 2)
With reference to FIG. 1, the vehicle body frame 2 is, for example, an underbone type. The vehicle body frame 2 includes a head pipe 14, an under frame 15 that extends downward from the head pipe 14 and is bent rearward, and a seat rail 16 that extends rearward and upward from the rear end portion of the underframe 15. An engine suspension bracket 17 is attached to the rear end of the underframe 15.

(Body cover 3)
With reference to FIG. 1, the vehicle body cover 3 includes a front cover 21, a rear cover 22 arranged behind the front cover 21, and a step board 23 connecting the lower portion of the front cover 21 and the lower portion of the rear cover 22. ing. A rider seat 24 is provided above the rear cover 22.

(Steering mechanism 4 and front wheels 5)
With reference to FIG. 1, the steering mechanism 4 is rotatably supported by a head pipe 14. The steering mechanism 4 includes a steering wheel device 26 and a pair of left and right front forks 27 connected to the steering wheel device 26. The front wheels 5 are rotatably supported at the lower ends of the pair of left and right front forks 27.

(Engine 6 and rear wheel 7)
With reference to FIGS. 1 to 3, the engine 6 is, for example, a unit swing type single cylinder engine. The engine 6 includes an engine case 31, a cylinder 32 that is coupled to the engine case 31 from the front, a cylinder head 33 that is coupled to the cylinder 32 from the front, and a head cover 34 that is coupled to the cylinder head 33 from the front.

The engine case 31 is divided into left and right parts, and includes a right case portion 31a and a left case portion 31b. A pair of left and right suspension bosses 36 project forward from the front end of the engine case 31. Each suspension boss 36 is attached to the engine suspension bracket 17 via a pivot shaft 37. As a result, the engine 6 can swing around the pivot shaft 37.

A crankshaft 38 is housed in the front portion of the engine case 31. A cooling fan 39 is provided at the right end of the crankshaft 38. The crankshaft 38 is connected to the rear wheels 7 via a stepless transmission and a clutch (neither shown).

The cylinder 32 protrudes from the engine case 31 in a forward leaning posture. A piston (not shown) is housed in the cylinder 32. The piston is connected to the crankshaft 38 via a connecting rod (not shown).

The cylinder head 33 projects from the cylinder 32 in a forward leaning posture. A combustion chamber 41 is provided between the cylinder 32 and the cylinder head 33. An intake port 42 communicating with the combustion chamber 41 is provided on the upper surface of the cylinder head 33. An exhaust port 43 communicating with the combustion chamber 41 is provided on the lower surface of the cylinder head 33.

(Intake device 8)
With reference to FIG. 2, the intake device 8 includes an air cleaner 45 arranged above the engine case 31, a throttle body 46 arranged in front of the air cleaner 45, and an outlet tube 47 connecting the air cleaner 45 and the throttle body 46. And an intake pipe 48 that connects the throttle body 46 and the intake port 42 of the cylinder head 33.

(Exhaust device 9)
Hereinafter, when the term "upstream side" or "downstream side" is used in the description of the exhaust device 9, it means the "upstream side" or "downstream side" in the exhaust gas flow direction (see the alternate long and short dash line arrow in FIG. 2). It shall be.

With reference to FIG. 2, the exhaust device 9 includes an exhaust pipe 51 connected to the exhaust port 43 of the cylinder head 33, an exhaust gas sensor 52 attached to the exhaust pipe 51, and a sub-catalyst 53 housed in the exhaust pipe 51. A muffler 54 connected to the exhaust pipe 51 and a main catalyst 55 housed in the muffler 54 are provided.

(Exhaust pipe 51 of the exhaust device 9)
With reference to FIGS. 2 to 4, the exhaust pipe 51 of the exhaust device 9 has a first piping portion 57 extending downward from the exhaust port 43 of the cylinder head 33 and a right side (outside in the vehicle width direction) from the first piping portion 57. ), And a third piping portion 59 extending rearward from the second piping portion 58.

The first piping portion 57 is formed from a single portion formed integrally. That is, the first piping portion 57 has an integral structure. The upper end portion (upstream end portion) of the first piping portion 57 is connected to the exhaust port 43 of the cylinder head 33. A flange 61 is attached to the upper end of the first piping portion 57. The flange 61 is attached to the lower surface of the cylinder head 33 via a pair of bolts 62. As a result, the upper end of the first piping portion 57 is fixed to the lower surface of the cylinder head 33 via the flange 61.

The upper portion (upstream side portion) of the first piping portion 57 extends directly below the exhaust port 43 of the cylinder head 33. The lower portion (downstream side portion) of the first piping portion 57 is curved toward the right side (outside in the vehicle width direction). A cylindrical mounting boss 63 projects rearward from the lower part of the first piping portion 57.

The second piping portion 58 is not provided horizontally and is inclined rearward and downward when viewed from the side of the vehicle. The second piping section 58 includes a catalyst case 64 that houses the sub-catalyst 53, and a connecting pipe 65 that connects the catalyst case 64 and the first piping section 57. The catalyst case 64 and the connecting pipe 65 are formed separately from each other.

The catalyst case 64 of the second piping portion 58 is formed in a hollow shape by joining the upper portion and the lower portion formed separately from each other. That is, the catalyst case 64 has a monaca structure. The catalyst case 64 includes a main body portion 66 extending linearly toward the rear right, and a reduced diameter portion 67 curved rearward from the right rear end portion (downstream end portion) of the main body portion 66. There is. The main body 66 is provided with the same diameter from the left front end (upstream end) to the right rear end (downstream end). The diameter-reduced portion 67 is reduced in diameter from the front side (upstream side) to the rear side (downstream side).

The connecting pipe 65 of the second piping portion 58 is formed in a hollow shape by joining the upper portion and the lower portion formed separately from each other. That is, the connecting pipe 65 has a monaca structure. The connecting pipe 65 is curved toward the right rear side. The diameter of the connecting pipe 65 increases from the left front side (upstream side) to the right rear side (downstream side). The left front end portion (upstream side end portion) of the connecting pipe 65 is connected to the lower end portion (downstream side end portion) of the first piping portion 57. The right rear end portion (downstream side end portion) of the connecting pipe 65 is connected to the left front end portion (upstream side end portion) of the main body 66 of the catalyst case 64.

The third piping portion 59 is formed from a single portion formed integrally. That is, the third piping portion 59 has an integral structure. The third piping portion 59 extends in the front-rear direction of the vehicle. The front end portion (upstream side end portion) of the third piping portion 59 is connected to the rear end portion (downstream side end portion) of the reduced diameter portion 67 of the catalyst case 64.

(Exhaust gas sensor 52 of the exhaust device 9)
With reference to FIGS. 3 to 5, the exhaust gas sensor 52 of the exhaust device 9 is composed of, for example, an O2 sensor, and detects the oxygen concentration in the exhaust gas flowing in the first piping portion 57 of the exhaust pipe 51. .. The exhaust gas sensor 52 is arranged in front of the engine case 31. Since the exhaust gas sensor 52 is arranged below the cylinder 32, the exhaust gas sensor 52 overlaps the cylinder 32 when viewed from the bottom of the vehicle. The exhaust gas sensor 52 is arranged inside the pair of left and right suspension bosses 36 in the vehicle width direction when viewed from the bottom of the vehicle. The exhaust gas sensor 52 is attached to a mounting boss 63 provided in the first piping portion 57 of the exhaust pipe 51, and protrudes rearward from the first piping portion 57 of the exhaust pipe 51.

The tip portion 52a of the exhaust gas sensor 52 faces rearward and is exposed from the first piping portion 57 of the exhaust pipe 51. When viewed from the bottom of the vehicle, the tip end 52a of the exhaust gas sensor 52 is located within the width of the flange 61 in the vehicle width direction and faces the axis X of the cylinder 32. The tip end portion 52a of the exhaust gas sensor 52 is connected to the ECU 69 (engine control unit) via the sensor harness 68. Since the sensor harness 68 and the ECU 69 are schematically displayed in FIG. 3, the positions of the sensor harness 68 and the ECU 69 in FIG. 3 do not necessarily match the positions of the sensor harness 68 and the ECU 69 in the actual space. Absent.

(Subcatalyst 53 of the exhaust device 9)
With reference to FIGS. 2 to 5, the sub-catalyst 53 of the exhaust device 9 is composed of, for example, a honeycomb-structured three-way catalyst. The subcatalyst 53 changes the exhaust gas into harmless components (for example, carbon dioxide, water, nitrogen) by a chemical reaction from harmful components (for example, carbon monoxide, hydrocarbons, nitrogen oxides) in the exhaust gas. Purify.

The sub-catalyst 53 is arranged in front of the crankshaft 38. The sub-catalyst 53 is housed in the main body 66 of the catalyst case 64 provided in the second piping 58 of the exhaust pipe 51. When viewed from the bottom of the vehicle, the sub-catalyst 53 is arranged outside the pair of left and right suspension bosses 36 in the vehicle width direction and does not overlap with the cylinder 32. When viewed from the bottom of the vehicle, the left end portion (inner end portion in the vehicle width direction) of the sub-catalyst 53 overlaps with the engine cover 11. When viewed from the bottom of the vehicle, most of the sub-catalyst 53 except the left end overlaps with the fan cowl 10. The sub-catalyst 53 is arranged on the right side (side) of the exhaust gas sensor 52. When viewed from the side of the vehicle, the sub-catalyst 53 overlaps the lower part of the exhaust gas sensor 52.

(Muffler 54 of the exhaust device 9)
With reference to FIG. 2, the muffler 54 of the exhaust device 9 is attached to the engine case 31 via the attachment bracket 70. The muffler 54 extends in the front-rear direction of the vehicle. The front end portion (upstream side end portion) of the muffler 54 is connected to the rear end portion (downstream side end portion) of the third piping portion 59 of the exhaust pipe 51.

(Main catalyst 55 of the exhaust device 9)
With reference to FIG. 2, the main catalyst 55 of the exhaust device 9 is composed of, for example, a honeycomb-structured three-way catalyst. The main catalyst 55 converts the exhaust gas into harmless components (for example, carbon dioxide, water, nitrogen) by a chemical reaction from harmful components (for example, carbon monoxide, hydrocarbons, nitrogen oxides) in the exhaust gas. Purify. The main catalyst 55 is larger in size than the subcatalyst 53.

(Fan cowl 10)
With reference to FIGS. 2 to 4, the fan cowl 10 includes an accommodating portion 71 for accommodating the cooling fan 39, and a duct portion 72 projecting forward from the upper portion of the accommodating portion 71. The accommodating portion 71 covers the right side (outside in the vehicle width direction) of the engine case 31. On the right side of the accommodating portion 71, a cooling air intake port 73 is provided on the right side (outside in the vehicle width direction) of the cooling fan 39. The duct portion 72 covers the right side (outside in the vehicle width direction) of the cylinder 32 and the cylinder head 33. The duct portion 72 connects the accommodating portion 71 and the engine cover 11.

(Engine cover 11)
With reference to FIGS. 2 to 5, the engine cover 11 is provided on the left side (inside in the vehicle width direction) of the duct portion 72 of the fan cowl 10 in succession with the duct portion 72 of the fan cowl 10. The engine cover 11 covers the outer periphery of the cylinder 32 and the cylinder head 33. The engine cover 11 is divided into upper and lower parts, and includes an upper cover portion 11a and a lower cover portion 11b.

A notch 75 is provided on the lower surface of the engine cover 11 at a position where the cylinder 32 and the exhaust gas sensor 52 overlap each other when viewed from the lower surface of the vehicle and around the same. When viewed from the bottom of the vehicle, the entire exhaust gas sensor 52 is housed inside the notch 75. When viewed from the bottom of the vehicle, the front portion of the notch 75 overlaps the entire flange 61. Therefore, the entire flange 61 can be visually recognized through the notch 75 when viewed from the bottom of the vehicle. The length of the front portion of the notch 75 in the vehicle width direction is slightly larger than the length of the flange 61 in the vehicle width direction. The length of the notch 75 in the vehicle width direction gradually narrows from the front to the rear.

A first wall portion 76 is provided on the lower surface of the engine cover 11 on the right side (side side) of the notch 75. In the vehicle width direction, the first wall portion 76 is arranged on the right side (the same side as the sub-catalyst 53) with respect to the exhaust gas sensor 52. The first wall portion 76 has a shape along the outer peripheral surfaces of the cylinder 32 and the cylinder head 33. A second wall portion 77 is provided on the lower surface of the engine cover 11 on the left side (side side) of the notch 75. In the vehicle width direction, the second wall portion 77 is arranged on the left side (opposite side of the sub-catalyst 53) with respect to the exhaust gas sensor 52. The second wall portion 77 projects downward with respect to the first wall portion 76. When viewed from the side of the vehicle, the second wall portion 77 overlaps the upper portion of the exhaust gas sensor 52.

(Exhaust gas flow)
The alternate long and short dash arrow attached to FIG. 2 indicates the flow direction of the exhaust gas.

When the engine 6 is driven, exhaust gas is discharged from the exhaust port 43 of the cylinder head 33. The exhaust gas discharged from the exhaust port 43 of the cylinder head 33 passes through the first piping portion 57 of the exhaust pipe 51 and then flows into the second piping portion 58 of the exhaust pipe 51. The exhaust gas that has flowed into the second piping portion 58 of the exhaust pipe 51 is purified by the sub-catalyst 53 and then discharged from the second piping portion 58 of the exhaust pipe 51. The exhaust gas discharged from the second piping portion 58 of the exhaust pipe 51 passes through the third piping portion 59 of the exhaust pipe 51 and then flows into the muffler 54. The exhaust gas that has flowed into the muffler 54 is purified by the main catalyst 55 and then discharged from the rear end of the muffler 54 to the rear of the vehicle.

(Cooling air flow)
The white arrows attached to FIGS. 3 and 4 indicate the flow direction of the cooling air.

Since the crankshaft 38 rotates when the engine 6 is driven, the cooling fan 39 provided at the right end of the crankshaft 38 also rotates. When the cooling fan 39 rotates in this way, the cooling air is taken into the accommodating portion 71 of the fan cowl 10 via the intake port 73. The cooling air taken into the accommodating portion 71 of the fan cowl 10 flows into the engine cover 11 through the duct portion 72 of the fan cowl 10, and forcibly cools the cylinder 32 and the cylinder head 33. The cooling air (hereinafter, referred to as “exhaust air”) warmed by forcibly cooling the cylinder 32 and the cylinder head 33 is discharged below the engine cover 11 through the notch 75. At that time, a part of the exhaust air hits the exhaust gas sensor 52.

(effect)
In this embodiment, the exhaust gas sensor 52 is attached to the first piping portion 57. By adopting such a configuration, the exhaust gas sensor 52 can be arranged upstream of the exhaust pipe 51. Therefore, the temperature rise of the exhaust gas sensor 52 can be promoted by the high-temperature exhaust gas immediately after being discharged from the exhaust port 43 of the cylinder head 33, and the exhaust gas sensor 52 can be activated at an early stage.

Further, when the exhaust gas sensor 52 is attached to the cylinder head 33, the cylinder head 33 must be provided with the attachment portion of the exhaust gas sensor 52, and the configuration of the cylinder head 33 needs to be significantly changed. On the other hand, in this embodiment, since the exhaust gas sensor 52 is attached to the first piping portion 57 as described above, it is not necessary to change the configuration of the cylinder head 33, and the manufacturing cost of the motorcycle 1 is increased. It can be suppressed.

Further, when the exhaust gas sensor 52 is attached to the cylinder head 33, the entire exhaust gas sensor 52 is housed in the engine cover 11. Along with this, the cooling air before cooling the cylinder 32 and the cylinder head 33 may intensively hit the exhaust gas sensor 52, and the exhaust gas sensor 52 may be cooled by the cooling air. On the other hand, in this embodiment, as described above, the exhaust gas sensor 52 is attached to the first piping portion 57, and a part of the exhaust gas sensor 52 is exposed to the outside of the engine cover 11 (see FIG. 5). ). Therefore, the cooling air before cooling the cylinder 32 and the cylinder head 33 is less likely to hit the exhaust gas sensor 52, and it is possible to prevent the exhaust gas sensor 52 from being cooled by the cooling air.

Further, the exhaust gas sensor 52 is attached to the first piping portion 57 so that the tip portion 52a faces rearward. By adopting such a configuration, since the traveling wind toward the exhaust gas sensor 52 is blocked by the first piping portion 57, it is possible to suppress the exhaust gas sensor 52 from being cooled by the traveling wind. Therefore, the temperature rise of the exhaust gas sensor 52 can be further promoted, and the exhaust gas sensor 52 can be activated even earlier.

Further, the engine cover 11 is provided with a notch 75 at a position where the cylinder 32 and the exhaust gas sensor 52 overlap when viewed from the lower surface of the vehicle. By adopting such a configuration, the exhaust gas sensor 52 can be heated by the radiant heat from the cylinder 32 toward the exhaust gas sensor 52. Therefore, the temperature rise of the exhaust gas sensor 52 can be further promoted, and the exhaust gas sensor 52 can be activated even earlier.

As described above, in this embodiment, the temperature rise of the exhaust gas sensor 52 is promoted by the plurality of configurations, and the exhaust gas sensor 52 is activated at an early stage. Therefore, even when the motorcycle 1 is started from the cold state, the exhaust gas sensor 52 can be quickly moved to a state where the oxygen concentration in the exhaust gas can be detected with high accuracy. Therefore, it is not necessary to warm up the motorcycle 1 for a long time in order to shift the exhaust gas sensor 52 to a state where the oxygen concentration in the exhaust gas can be detected accurately, and the usability and energy saving of the motorcycle 1 are improved. be able to.

Further, since the temperature rise of the exhaust gas sensor 52 can be promoted by the plurality of configurations as described above, it is not necessary to install a dedicated heater for heating the exhaust gas sensor 52. Therefore, it is possible to suppress an increase in the manufacturing cost of the motorcycle 1.

Further, when viewed from the side of the vehicle, the engine cover 11 overlaps a part of the exhaust gas sensor 52. By adopting such an arrangement, the engine cover 11 can cover a part of the exhaust gas sensor 52 and improve the heat retention of the exhaust gas sensor 52. Therefore, the temperature rise of the exhaust gas sensor 52 can be further promoted, and the exhaust gas sensor 52 can be activated even earlier.

Further, the sub-catalyst 53 is housed in the second piping portion 58, and the sub-catalyst 53 overlaps a part of the exhaust gas sensor 52 when viewed from the side of the vehicle. By adopting such an arrangement, the sub-catalyst 53 can be arranged as close to the exhaust gas sensor 52 as possible, and the exhaust gas sensor 52 can be heated by the radiant heat from the sub-catalyst 53. Therefore, the temperature rise of the exhaust gas sensor 52 can be further promoted, and the exhaust gas sensor 52 can be activated even earlier.

Further, the engine cover 11 is arranged on the right side (the same side as the sub-catalyst 53) of the exhaust gas sensor 52 and the left side (opposite side of the sub-catalyst 53) of the exhaust gas sensor 52. The second wall portion 77 is provided with a second wall portion 77, and the second wall portion 77 projects downward with respect to the first wall portion 76. By projecting the second wall portion 77 downward with respect to the first wall portion 76 in this way, a part of the exhaust gas sensor 52 can be covered by the second wall portion 77, and the heat retention of the exhaust gas sensor 52 can be improved. Further, since the first wall portion 76 is recessed above the second wall portion 77, the radiant heat from the sub-catalyst 53 toward the exhaust gas sensor 52 is suppressed from being blocked by the first wall portion 76, and the sub-catalyst 53 from the sub-catalyst 53. The exhaust gas sensor 52 can be heated by radiant heat. As described above, the exhaust gas sensor 52 can be heated by the radiant heat from the sub-catalyst 53 while the second wall portion 77 enhances the heat retention of the exhaust gas sensor 52. Therefore, the temperature of the exhaust gas sensor 52 can be raised efficiently, and the exhaust gas sensor 52 can be activated even earlier.

Further, when viewed from the bottom of the vehicle, a part of the sub-catalyst 53 overlaps with the engine cover 11. By adopting such an arrangement, the sub-catalyst 53 can be arranged as close to the inside in the vehicle width direction as possible and brought close to the exhaust gas sensor 52, so that the exhaust gas sensor 52 can be easily heated by the radiant heat from the sub-catalyst 53. Therefore, the temperature rise of the exhaust gas sensor 52 can be further promoted, and the exhaust gas sensor 52 can be activated even earlier. Further, since not only the exhaust gas sensor 52 but also the sub-catalyst 53 can be arranged upstream of the exhaust pipe 51, the purification performance of the sub-catalyst 53 with respect to the exhaust gas can be improved.

Further, when viewed from the lower surface of the vehicle, the front portion of the notch 75 overlaps with the flange 61, and the length of the notch 75 in the vehicle width direction gradually narrows from the front to the rear. By adopting such a configuration, it is possible to improve the heat retention of the exhaust gas sensor 52 by minimizing the opening area of the notch 75 while ensuring the ease of attaching / detaching the flange 61. Therefore, the temperature rise of the exhaust gas sensor 52 can be further promoted, and the exhaust gas sensor 52 can be activated even earlier.

Further, when viewed from the bottom of the vehicle, the entire exhaust gas sensor 52 is contained inside the notch 75. By adopting such a configuration, it becomes easy to heat the exhaust gas sensor 52 by the radiant heat from the cylinder 32 toward the exhaust gas sensor 52. Therefore, the temperature rise of the exhaust gas sensor 52 can be further promoted, and the exhaust gas sensor 52 can be activated even earlier.

(Modification example)
The layout of the exhaust pipe 51 described in this embodiment is merely an example and can be changed in other different embodiments. For example, in other different embodiments, the layout of the exhaust pipe 51 may be laterally opposite to that of the present embodiment.

In this embodiment, the sub-catalyst 53 is arranged in the second piping portion 58, and the main catalyst 55 is arranged in the muffler 54. On the other hand, in another different embodiment, the main catalyst 55 may be arranged in the second piping portion 58, and the sub catalyst 53 may be arranged in the muffler 54.

In this embodiment, the catalyst having the larger size is defined as the main catalyst 55, and the catalyst having the smaller size is defined as the sub catalyst 53. On the other hand, in another different embodiment, the catalyst having the higher purification contribution rate of the exhaust gas may be defined as the main catalyst 55, and the catalyst having the lower purification contribution rate of the exhaust gas may be defined as the sub catalyst 53. ..

In this embodiment, the sub-catalyst 53 overlaps a part of the exhaust gas sensor 52 when viewed from the side of the vehicle. On the other hand, in another different embodiment, the sub-catalyst 53 may overlap the entire exhaust gas sensor 52 in the vehicle side view.

In this embodiment, the engine cover 11 overlaps a part of the exhaust gas sensor 52 when viewed from the side of the vehicle. On the other hand, in another different embodiment, the engine cover 11 may overlap the entire exhaust gas sensor 52 in the vehicle side view.

In this embodiment, a part of the sub-catalyst 53 overlaps with the engine cover 11 when viewed from the bottom of the vehicle. On the other hand, in another different embodiment, the entire sub-catalyst 53 may overlap the engine cover 11 when viewed from the bottom of the vehicle.

In this embodiment, the entire exhaust gas sensor 52 fits inside the notch 75 when viewed from the bottom of the vehicle. On the other hand, in another different embodiment, a part of the exhaust gas sensor 52 may be contained inside the notch 75 when viewed from the bottom of the vehicle.

In this embodiment, the configuration of the present invention is applied to the scooter type motorcycle 1. On the other hand, in another different embodiment, the configuration of the present invention may be applied to a motorcycle 1 other than the scooter type such as a sports type or an off-road type.

1 Motorcycle 11 Engine cover 31 Engine case 32 Cylinder 33 Cylinder head 38 Crankshaft 43 Exhaust port 51 Exhaust pipe 52 Exhaust gas sensor 52a Exhaust gas sensor tip 53 Subcatalyst 57 1st piping 58 2nd piping 59 3rd piping 61 Flange 64 Catalyst case 65 Connection pipe 75 Notch 76 1st wall 77 2nd wall

Claims (7)

An engine case that houses the crankshaft and
A cylinder that connects to the engine case from the front
A cylinder head that is connected to the cylinder from the front and is provided with an exhaust port,
The exhaust pipe connected to the exhaust port and
An exhaust gas sensor attached to the exhaust pipe and
An engine cover that covers the cylinder and the cylinder head is provided.
The exhaust pipe
The first piping part extending downward from the exhaust port and
The second piping portion extending outward in the vehicle width direction from the first piping portion and
A third piping portion extending rearward from the second piping portion is provided.
The exhaust gas sensor is arranged below the cylinder, and is attached to the first piping portion so that the tip portion faces rearward.
A motorcycle characterized in that the engine cover is provided with a notch at a position where the cylinder and the exhaust gas sensor overlap when viewed from the bottom of the vehicle. The motorcycle according to claim 1, wherein the engine cover overlaps at least a part of the exhaust gas sensor when viewed from the side of the vehicle. A catalyst for purifying the exhaust gas flowing through the exhaust pipe is provided.
The catalyst is housed in the second piping section.
The motorcycle according to claim 1 or 2, wherein the catalyst overlaps at least a part of the exhaust gas sensor when viewed from the side of the vehicle. A catalyst for purifying the exhaust gas flowing through the exhaust pipe is provided.
The engine cover
A first wall portion arranged on the same side as the catalyst with respect to the exhaust gas sensor,
A second wall portion arranged on the opposite side of the catalyst with respect to the exhaust gas sensor is provided.
The motorcycle according to any one of claims 1 to 3, wherein the second wall portion projects downward with respect to the first wall portion. A catalyst for purifying the exhaust gas flowing through the exhaust pipe is provided.
The motorcycle according to any one of claims 1 to 4, wherein at least a part of the catalyst is overlapped with the engine cover when viewed from the bottom of the vehicle. A flange for fixing the first piping portion to the cylinder head is provided.
When viewed from the bottom of the vehicle, the front part of the notch overlaps the flange.
The motorcycle according to any one of claims 1 to 5, wherein the length of the notch in the vehicle width direction is gradually narrowed from the front to the rear. The motorcycle according to any one of claims 1 to 6, wherein the entire exhaust gas sensor is housed inside the notch when viewed from the bottom of the vehicle.

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