JP6620677B2 - Exhaust gas sensor layout - Google Patents

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.

An exhaust gas sensor arrangement structure according to the present invention includes a catalyst that purifies exhaust gas of an engine, an exhaust gas sensor that detects an exhaust gas component of the engine, and a chamber that is disposed at the rear of the engine. The exhaust gas sensor is provided on the upstream side of the catalyst and is disposed below the engine; and disposed downstream of the catalyst has a downstream sensor that will be disposed in the chamber, communicating said chamber is in communication with the partition wall, a plurality of spaces between partitioned by the partition wall which partitions the inner space And the downstream sensor overlaps with the communication pipe on the downstream side of the communication pipe when viewed from the axial direction of the communication pipe. It is disposed, and, a top of the chamber, in the vehicle rear face view, and wherein arranged are possible between the bracket and the rear suspension link for securing the chamber to the body.

According to this configuration, since the catalyst is disposed below the engine, the exhaust gas sensor can be disposed close to the catalyst before and after the catalyst. In particular, even when the catalyst enters the chamber, the downstream sensor can be arranged in a relatively large space behind the engine by arranging the chamber behind the engine. Therefore, the degree of freedom when the downstream sensor is arranged close to the catalyst is improved. As a result, the detection accuracy of the exhaust gas sensor is not impaired. Further, since the downstream sensor is arranged immediately after the communication pipe, the exhaust gas collected in the communication pipe can easily come into contact with the downstream sensor. As a result, the detection accuracy of the downstream sensor can be improved. Furthermore, since the downstream sensor is arranged at the upper part of the chamber, the space above the chamber can be used effectively. Further, since the downstream sensor is surrounded by the peripheral configuration of the chamber such as the bracket and the rear suspension link, the downstream sensor can be protected from flying stones and the like.

  The exhaust gas sensor arrangement structure according to the present invention further includes a side stand configured to be swingable between a support position for supporting the vehicle and a storage position, and the side stand is in the storage position. The downstream sensor preferably overlaps the side stand in a side view of the vehicle. According to this configuration, when the side stand is in the storage position, the side of the downstream sensor is hidden by the side stand. As a result, the downstream sensor can be protected from flying stones and the like during traveling. Further, the cover for protecting the downstream sensor can be omitted, and the configuration can be simplified.

  Further, in the exhaust gas sensor arrangement structure according to the present invention, the chamber has a guide pipe for guiding exhaust gas from the downstream of the catalyst to the joint portion, and the guide pipe has an upstream end behind the catalyst. It is preferable that the downstream end extends to the downstream end of the joint portion while being separated from the end, and the downstream sensor is attached so as to penetrate the joint portion and the guide pipe. According to this configuration, the exhaust gas can be stably detected by the downstream sensor in the induction pipe without the exhaust gas being diffused.

  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 left 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 partially enlarged view of the motorcycle below the engine shown in FIG. 1. It is a top view which shows the exhaust system which concerns on this Embodiment. It is sectional drawing when cut along the AA line of FIG. It is a left view which shows the arrangement structure of the exhaust gas sensor which concerns on a 1st modification. It is a rear view which shows the arrangement structure of the exhaust gas sensor which concerns on a 1st modification. It is a left view which shows the arrangement structure of the exhaust gas sensor which concerns on a 2nd modification. It is a top view which shows the arrangement structure of the exhaust gas sensor which concerns on a 2nd modification. It is a top view which shows the arrangement structure of the exhaust gas sensor which concerns on a 3rd modification.

  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 exhaust gas sensor arrangement structure according to the present invention is applied to a sports 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 left 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 partially enlarged view below the engine in the motorcycle shown in FIG.

  As shown in FIGS. 1 and 2, the motorcycle 1 is configured by suspending an engine 3 on a vehicle body frame 2 on which components such as a power unit and an electrical system are mounted. The engine 3 is composed of, for example, a parallel 4-cylinder engine. The engine 3 is configured by attaching a cylinder head and a cylinder head cover (not shown) to an upper part of an engine case 30 in which a crankshaft (not shown) or the like is accommodated. An oil pan 31 is provided below the engine case 30.

  The vehicle body frame 2 is a twin spar type frame formed by aluminum casting, and is configured to obtain rigidity as a whole vehicle body by suspending the engine 3 as described above. The body frame 2 as a whole has a shape extending from the front to the rear and curved downward on the rear end side.

  Specifically, the vehicle body frame 2 includes a head frame 21 that extends bifurcated from the head pipe 20 toward the rear, a pair of left and right tank rails 22 that extend obliquely downward from the head frame 21 toward the rear of the vehicle body, and a tank. A body frame 23 extending downward from the rear end of the rail 22 is provided.

  The head frame 21 has a pair of left and right bracket portions 21a protruding downward, and supports the front side (cylinder head) of the engine 3 with the bracket portions 21a. The tank rail 22 is formed in a cylindrical shape having a hollow cross-sectional shape. The fuel tank 10 is disposed on the tank rail 22.

  The body frame 23 is configured by connecting upper and lower ends of a pair of frame portions 23 a extending downward from the rear ends of the tank rails 22 in the vehicle width direction. At the upper and lower ends of the body frame 23, the rear side of the engine 3 (rear part of the engine case 30) is supported. In addition, a swing arm pivot 23b for swingably supporting the swing arm 11 is formed at a substantially central portion of the body frame 23 in the vertical direction.

  In addition, a seat rail (not shown) and a back stay 24 that extend rearward and upward are provided at the upper end of the body frame 23. A rider seat 12 and a pillion seat 13 connected to the fuel tank 10 are provided on the seat rail.

  Various covers as a vehicle body exterior are attached to the vehicle body frame 2 and the engine 3 configured as described above. Specifically, the side surface of the vehicle body is covered with the side cowl 41 and the seat rail is covered with the rear cowl 42.

  A pair of left and right front forks 50 are supported on the head pipe 20 via a steering shaft (not shown) so as to be steerable. A front wheel 51 is rotatably supported at a lower portion of the front fork 50, and an upper portion of the front wheel 51 is covered with a front fender 52.

  The swing arm 11 extends rearward from the swing arm pivot 23b. A rear suspension 53 is provided between the swing arm 11 and the body frame 23. One end of the rear suspension 53 is supported on the upper end side of the body frame 23, and the other end is supported on the lower front side of the swing arm 11 via the rear suspension link 54. A rear wheel 55 is rotatably supported at the rear end of the swing arm 11. The upper portion of the rear wheel 55 is covered with a rear fender 56 provided at the rear portion of the rear cowl 42.

  Further, as shown in FIG. 2, a side stand 14 for supporting the vehicle is provided at the lower end of the left body frame 23. The side stand 14 extends in a rod shape with the lower portion of the body frame 23 as a base end, and is configured to be swingable with the base end portion as a fulcrum. Specifically, the side stand 14 is configured to be swingable between a support position for supporting the vehicle and a storage position. FIG. 2 shows a state where the solid line portion is in the storage position.

  Further, an exhaust pipe 6, a chamber 7, and a muffler 70 are connected to each exhaust port of the cylinder head as an exhaust system. A plurality of exhaust pipes 6 (four in the present embodiment) extend downward from the respective exhaust ports, bend rearward at the front lower side of the engine 3, and are combined into one. The chamber 7 is provided below the engine 3. A catalyst 8 for purifying exhaust gas is provided between the exhaust pipe 6 and the chamber 7.

  The catalyst 8 is composed of, for example, a three-way catalyst and is accommodated in a cylindrical catalyst case 80 (see FIG. 2). The rear end portion of the catalyst 8 enters the chamber 7. The catalyst 8 converts pollutants (carbon monoxide, hydrocarbons, nitrogen oxides, etc.) in the exhaust gas into harmless substances (carbon dioxide, water, nitrogen, etc.). A muffler 70 is connected to the downstream side of the catalyst 8 through the chamber 7. Exhaust gas generated by combustion of the engine 3 is purified by the catalyst 8 through the exhaust pipe 6. The exhaust gas is discharged outside after the exhaust noise is reduced by the muffler 70 through the chamber 7.

  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 15 (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 15 comprehensively controls various operations in the motorcycle 1. The ECU 15 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 this embodiment, the ECU 15 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.

  As described above, in accordance with recent exhaust gas regulations, it is required to monitor the deterioration state of a catalyst as an exhaust gas purification device in a motorcycle exhaust system. 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 the 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 the layout restriction inherent 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. In addition, it is conceivable to place the catalyst itself on the front side of the vehicle, but in the first place it is difficult to secure the catalyst placement space, and it is necessary to make a significant design change from the conventional layout, so it is not very realistic. Absent. 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.

  Therefore, the present inventor has conceived the present invention by focusing on the limited space below and behind the engine 3 in the sports type motorcycle 1. Specifically, in the present embodiment, the catalyst 8 is disposed below the engine case 30 (oil pan 31), and the chamber 7 is disposed behind the engine 3. At least a portion of the catalyst 8 is disposed in the chamber 7. The upstream sensor 90 is disposed upstream of the catalyst 8, and the downstream sensor 91 is disposed in the chamber 7 downstream of the catalyst 8.

  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 engine 3. In particular, even when the catalyst 8 enters the chamber 7, the downstream sensor 91 can be disposed in a relatively large space behind the engine 3 by arranging the chamber 7 behind the engine 3. it can. Therefore, the degree of freedom when the downstream sensor 91 is disposed close to the catalyst 8 is improved. 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 and behind the engine 3, the exhaust gas sensor 9 can be disposed without requiring a significant design change and without affecting the appearance design. It was. Furthermore, by providing the catalyst 8 near the engine 3, 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. .

  Next, the exhaust system according to the present embodiment will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a top view showing the exhaust system according to the present embodiment. 4 is a cross-sectional view taken along the line AA in FIG.

  As shown in FIG. 3, in the exhaust system according to the present embodiment, the exhaust pipe 6 includes exhaust pipes 6a-6d that extend downward from the exhaust ports of the cylinder head, first exhaust pipes 60a, 60b, and first exhaust pipes 6a-6b. The two collecting pipes 61 are combined into one. Specifically, as shown in FIG. 3, exhaust pipes 6a, 6b, 6c, and 6d are arranged from the left side in the vehicle width direction. The exhaust pipes 6a and 6d on the outer side in the vehicle width direction are connected by a connecting pipe 62a extending in the vehicle width direction. The exhaust pipes 6b and 6c on the inner side in the vehicle width direction are connected by a connection pipe 62b extending in the vehicle width direction.

  The four exhaust pipes 6 a to 6 d are bent backward at the front lower side of the engine case 30. The two left exhaust pipes 6a and 6b are connected to the first collecting pipe 60a and combined into one, and the two right exhaust pipes 6c and 6d are connected to the first collecting pipe 60b and combined into one. It is done. The first collecting pipes 60a and 60b each extend rearward, are connected to the second collecting pipe 61, and are combined into one.

  The second collecting pipe 61 extends rearward, and an exhaust control valve 61a for adjusting the flow rate of the exhaust gas is provided inside. The exhaust control valve 61 a is located on the downstream side of the second collecting pipe 61. The exhaust control valve 61a is configured by, for example, a butterfly valve, and adjusts the flow rate of the exhaust gas by expanding and contracting the flow passage cross-sectional area of the second collecting pipe 61. The catalyst 8 accommodated in the catalyst case 80 is connected to the rear end of the second collecting pipe 61. The chamber 7 is connected to the rear end of the catalyst case 80.

  The catalyst 8 has a columnar honeycomb portion that adsorbs a predetermined component in the exhaust gas and a cylindrical outer tube portion that covers the honeycomb portion (both not shown). The honeycomb part and the outer cylinder part extend into the chamber 7 downstream of the catalyst case 80.

  The chamber 7 is formed in a box shape having a predetermined expansion chamber. Specifically, the chamber 7 is formed of a substantially rectangular parallelepiped having a width in the front-rear direction and a left-right direction larger than the width in the vertical direction and having a rectangular shape in a front view and a side view. The chamber 7 is formed, for example, by welding the upper half opened at the bottom and the lower half opened at the top. A connection port 71 for connecting to the catalyst case 80 is formed on the front surface of the chamber 7. The connection port 71 is formed at a substantially central portion in the left-right direction on the front surface of the chamber 7, and has a cylindrical shape corresponding to the outer diameter of the catalyst case 80.

  A connecting pipe 72 for connecting the muffler 70 is provided at the right rear corner of the chamber 7. The connection pipe 72 communicates with the internal space (a downstream space described later) of the chamber 7, and the downstream end is directed to the upper right rear. As shown in FIG. 4, a pair of brackets 73 (not shown in FIG. 3) for fixing the chamber 7 to the vehicle body side (body frame 23 (see FIG. 1)) are provided on the upper surface of the chamber 7.

  A partition wall 75 is provided in the chamber 7 to divide the internal space back and forth. The partition wall 75 is formed to extend to the left and right at the approximate center in the front-rear direction of the chamber 7. The partition wall 75 divides the space in the chamber 7 into a front upstream space S1 and a rear downstream space S2.

  The partition wall 75 is provided with a communication pipe 76 that communicates the upstream space S1 and the downstream space S2. The communication pipe 76 is formed to extend forward and backward so as to penetrate the left partition wall 75. The upstream end of the communication pipe 76 has an enlarged diameter so that exhaust gas flowing from the catalyst case 80 into the upstream space S <b> 1 can be easily introduced into the communication pipe 76.

  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.

  The upstream sensor 90 is disposed below the engine 3 (see FIG. 1). Specifically, the upstream sensor 90 is attached so that one end side penetrates into the second collecting pipe 61 on the upstream side of the second collecting pipe 61. The upstream sensor 90 is attached to the front side of the exhaust control valve 61a so as to be biased to the left side from the central axis of the second collecting pipe 61, and the other end side is directed to the upper left.

  The downstream sensor 91 is attached to the upper half of the chamber 7 on the downstream side of the catalyst 8. Specifically, the downstream sensor 91 is attached so that one end side penetrates into the chamber 7 and is exposed in the upstream space S1. The downstream sensor 91 is attached to the upstream side of the communication pipe 76 so as to be biased to the left side from the central axis of the communication pipe 76, and the other end side is directed to the upper left. In particular, as shown in FIG. 4, the downstream sensor 91 is disposed so as to overlap the communication pipe 76 when viewed from the axial direction of the communication pipe 76. More specifically, one end of the downstream sensor 91 enters the radially inner side from the enlarged diameter portion of the communication pipe 76 in front view.

  Further, as shown in FIG. 2, the downstream sensor 91 is disposed so as to overlap the side stand 14 in a side view when the side stand 14 is in the storage position. According to this configuration, since the side (left side) of the downstream sensor 91 is concealed by the side stand 14, the downstream sensor 91 can be protected from flying stones during traveling. Further, the cover for protecting the downstream sensor 91 can be omitted, and the configuration can be simplified.

  In the exhaust system configured as described above, exhaust gas generated by the combustion of the engine 3 flows into the exhaust pipe 6 from an exhaust port (not shown) of the engine 3. Then, the flow rate of the exhaust gas is adjusted by the exhaust control valve 61 a and flows into the catalyst 8. The exhaust gas purified by the catalyst 8 flows into the upstream space S1 of the chamber 7. At this time, since the flow passage cross-sectional area of the exhaust gas increases rapidly, the flow rate of the exhaust gas is rapidly decreased. While the exhaust gas collides with the inner wall in the upstream space S1, the flow path is bent leftward.

  The exhaust gas flowing in the chamber 7 is collected in the communication pipe 76 when moving from the upstream space S1 to the downstream space S2, and flows into the downstream downstream space S2 through the communication pipe 76. As described above, the downstream sensor 91 is disposed on the upstream side of the communication pipe 76 so that one end enters the inside of the communication pipe 76 when viewed from the front. For this reason, when the exhaust gas flows into the communication pipe 76, the exhaust gas easily comes into contact with the downstream sensor 91. As a result, the detection accuracy of the downstream sensor 91 can be improved. Further, the exhaust gas is bent rightward while colliding with the inner wall in the downstream space S <b> 2 and flows into the muffler 70 through the connection pipe 72.

  Next, an arrangement structure of the exhaust gas sensor according to the first modification will be described with reference to FIGS. FIG. 5 is a left side view showing the arrangement structure of the exhaust gas sensor according to the first modification. FIG. 6 is a rear view showing the arrangement structure of the exhaust gas sensor according to the first modification. In the first modification, the arrangement location of the downstream sensor is different from the present embodiment. For this reason, the structure which is common in this Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted suitably.

  As shown in FIGS. 5 and 6, in the first modification, the downstream end of the communication pipe 76 increases in diameter toward the downstream. Further, a downstream sensor 91 is provided immediately after the communication pipe 76 (downstream side). Specifically, the downstream sensor 91 is attached to the upper portion of the chamber 7 with the axial direction oriented substantially in the vertical direction. The downstream sensor 91 is attached such that one end side penetrates into the chamber 7 and is exposed in the downstream space S1. That is, one end of the downstream side sensor 91 enters radially inward from the diameter-enlarged portion (downstream end) of the communication pipe 76 in the rear view.

  In particular, the downstream sensor 91 is disposed so as to overlap the communication pipe 76 when viewed from the axial direction of the communication pipe 76. More specifically, one end of the downstream sensor 91 enters the inside in the radial direction from the communication pipe 76 in the rear view. As described above, the downstream sensor 91 is arranged immediately after the communication pipe 76, so that the exhaust gas collected in the communication pipe 76 can easily come into contact with the downstream sensor 91 when flowing into the downstream space S2. . As a result, the detection accuracy of the downstream sensor 91 can be improved.

  Further, the downstream side sensor 91 is disposed in the upper part of the chamber 7 between the rear suspension link 54 and the bracket 73 that fixes the chamber 7 to the vehicle body (body frame 23) in the rear view. Specifically, the downstream sensor 91 is sandwiched between the bracket 73 and the rear suspension link 54 in the left-right direction.

  According to this configuration, the downstream sensor 91 is disposed on the upper portion of the chamber 7, so that the space above the chamber 7 can be used effectively. Further, since the downstream sensor 91 is surrounded by the peripheral configuration of the chamber 7 such as the bracket 73 and the rear suspension link 54, the downstream sensor 91 can be protected from flying stones and the like. Further, the cover for protecting the downstream sensor 91 can be omitted, and the configuration can be simplified.

  Next, the arrangement structure of the exhaust gas sensor according to the second and third modifications will be described with reference to FIGS. FIG. 7 is a right side view showing the arrangement structure of the exhaust gas sensor according to the second modification. FIG. 8 is a top view showing an arrangement structure of the exhaust gas sensor according to the second modification. FIG. 9 is a top view showing an arrangement structure of exhaust gas sensors according to a third modification. 8 and 9, the upper half of the chamber is omitted for convenience of explanation. Further, in the second and third modified examples, the configurations of the catalyst and the chamber and the location of the downstream sensor are different from the present embodiment and the first modified example. For this reason, the structure which is common in each said form is shown with the same code | symbol, and the description is abbreviate | omitted suitably.

  As shown in FIGS. 7 and 8, in the second modification, the chamber 101 is directly connected to the rear end of the second collecting pipe 61. The chamber 101 is formed in a box shape having a predetermined expansion chamber. The chamber 101 according to the second modification is different from the above-described embodiments in that the partition wall 75 and the communication pipe 76 are not provided.

  A joint portion 102 for connecting the muffler 70 is provided at the right rear corner of the chamber 101. The joint portion 102 communicates with the internal space of the chamber 101, and the downstream end is directed to the upper right rear. Specifically, the upstream end of the joint portion 102 is connected to the upper surface of the chamber 101 and has a rectangular shape that is long in the front-rear direction when viewed from above. And the joint part 102 is extended in the right rear upper direction so that it may reduce in diameter as it goes downstream and a downstream end may form a circular cross section.

  The catalyst 103 extends rearward from the downstream end of the second collecting pipe 61 to the substantially front half of the chamber 101. As shown in FIG. 8, the catalyst 103 extends from the approximate center of the front surface of the chamber 101 slightly inclined to the left rear in a top view. A guide pipe 104 that guides the exhaust gas after purification to the joint portion 102 is connected to the rear end of the catalyst 103. The guide pipe 104 bends rightward and rearward from the rear end of the catalyst 103 to the joint portion 102 toward the upstream end, and the downstream end is opened at the inlet of the joint portion 102.

  In the second modification, the downstream sensor 91 is attached to the upstream end of the joint portion 102. Specifically, the downstream sensor 91 is attached to the left side of the joint portion 102 with the axial direction directed substantially in the vertical direction (slightly upper left). The downstream sensor 91 is attached so that one end side penetrates into the joint portion 102 and is exposed in the exhaust gas flow path.

  In particular, as shown in FIG. 8, the downstream sensor 91 has an end portion (the other end side) opposite to the detection portion located in a range from the vehicle upper side to the front side in the vehicle side view, and the chamber 101 in the vehicle top view. It is arranged within the width. For this reason, it is possible to prevent the downstream sensor 91 from protruding from the chamber 101. Therefore, it is possible to easily secure a gap between the peripheral configuration of the chamber 101 and the downstream sensor 91, and the downstream sensor 91 is easily protected.

  In the second modified example configured as described above, the exhaust gas after being purified by the catalyst 103 is guided to the joint portion 102 by the guide pipe 104. As described above, the guide pipe 104 is attached to the downstream end (rear end) of the catalyst 103, and the downstream sensor 91 is provided in the joint portion 102, so that the exhaust gas is guided to the downstream sensor 91 without being diffused. It is burned. Therefore, the exhaust gas collected at the joint portion 102 is likely to come into contact with the downstream sensor 91. As a result, the detection accuracy of the downstream sensor 91 can be improved.

  As described above, since the exhaust gas is guided to the downstream sensor 91 by the guide pipe 104, the sensor output can be stably obtained without the exhaust gas being diffused. For example, even if the downstream sensor 91 is disposed at a location relatively away from the catalyst, the detection accuracy of the downstream sensor 91 is not impaired. Further, since the downstream end of the guide pipe 104 is opened at the entrance of the joint portion 102, the original function of the chamber 101 is not impaired. In the configuration of FIG. 8, there is no gap between the catalyst 103 and the guide pipe 104, but a gap may be provided to achieve the purpose of the chamber. Further, an interference hole may be formed.

  In the third modification shown in FIG. 9, the configuration of the guide pipe 105 is different from that of the second modification. As shown in FIG. 9, the guide pipe 105 is disposed with a slight gap from the rear end of the catalyst 103, and bends rightward and rearward toward the joint portion 102. The guide pipe 105 further extends to the downstream end of the joint portion 102 and is connected to the muffler together with the joint portion 102. Further, the outer diameter of the guide pipe 105 is smaller than the outer diameter of the catalyst 103 and larger than the radius of the catalyst 103. In particular, the upstream end of the guide pipe 105 is disposed slightly to the right with respect to the catalyst 103, and the upstream end of the catalyst 103 and the guide pipe 105 overlap when viewed from the axial direction of the catalyst 103.

  The downstream sensor 91 is attached to the upstream end of the joint portion 102 as in the second modification. Specifically, the downstream sensor 91 is attached to the left side of the joint portion 102 with the axial direction directed substantially in the vertical direction (slightly upper left). In particular, in the third modification, one end side of the downstream sensor 91 is attached so as to penetrate into the joint portion 102 and the guide pipe 105 and to be exposed in the exhaust gas flow path.

  Even with such a configuration, the exhaust gas collected in the joint portion 102 can easily come into contact with the downstream sensor 91. As described above, the catalyst 103 and the upstream end of the guide pipe 105 overlap, so that the exhaust gas after purification easily flows into the guide pipe 105. As a result, the exhaust gas can be easily guided to the downstream sensor 91, and the detection accuracy of the downstream sensor 91 can be improved. Further, since the exhaust gas is guided to the downstream sensor 91 by the guide pipe 105, the exhaust gas can be stably detected by the downstream sensor 91 in the guide pipe 105 without being diffused. Furthermore, since the upstream end of the guide pipe 105 is opened at the outlet of the catalyst 103, the original function of the chamber 101 is not impaired.

  As described above, according to each of the above embodiments, even if a part of the catalyst enters the chamber or the entire catalyst is provided in the chamber, the exhaust is performed without impairing the detection accuracy of the downstream sensor. The gas sensor can be optimally arranged.

  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 immediately before the catalyst 8, but the present invention is not limited to this configuration. The upstream sensor 90 may be disposed at any position as long as it is upstream of the catalyst 8, and may be disposed in front of the engine case 30, for example.

  In the embodiment described above, the single catalyst 8 is provided. However, the present invention is not limited to this configuration. For example, the catalyst may be composed of a divided catalyst or a plurality of catalysts.

  In the above-described embodiment, the space in the chamber 7 is divided into two spaces (the upstream space S1 and the downstream space S2) by the partition wall 73, but is not limited to this configuration. The space in the chamber 7 may be partitioned into three or more spaces.

  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.

DESCRIPTION OF SYMBOLS 1 Motorcycle 14 Side stand 3 Engine 54 Rear suspension link 7, 101 Chamber 70 Muffler 73 Bracket 75 Partition wall 76 Communication pipe 8, 103 Catalyst 9 Exhaust gas sensor 90 Upstream sensor 91 Downstream sensor 102 Joint part 104, 105 Guide pipe

Claims (5)

A catalyst for purifying engine exhaust gas,
An exhaust gas sensor for detecting an exhaust gas component of the engine;
A chamber disposed behind the engine,
The catalyst is provided below the engine, and at least a part of the catalyst is disposed in the chamber.
The exhaust gas sensor is disposed upstream of the catalyst, an upstream side sensor that is disposed below the engine, is provided on the downstream side of the catalyst, it has a downstream sensor that will be disposed in the chamber ,
The chamber has a partition wall that partitions an internal space, and a communication pipe that communicates a plurality of spaces partitioned by the partition wall,
The downstream sensor is disposed on the downstream side of the communication pipe so as to overlap the communication pipe when viewed from the axial direction of the communication pipe, and is an upper part of the chamber, and the chamber in the rear view of the vehicle An exhaust gas sensor arrangement structure, wherein the exhaust gas sensor is arranged between a bracket for fixing the vehicle to a vehicle body and a rear suspension link . A catalyst for purifying engine exhaust gas,
An exhaust gas sensor for detecting an exhaust gas component of the engine;
A chamber located behind the engine;
A joint for connecting the chamber and the muffler,
The catalyst is provided below the engine, and at least a part of the catalyst is disposed in the chamber.
The exhaust gas sensor has an upstream sensor provided on the upstream side of the catalyst and disposed below the engine, and a downstream sensor provided on the downstream side of the catalyst,
The downstream sensor is disposed in the joint portion, and an end opposite to the detection portion is positioned in a range from the top to the front of the vehicle in a side view of the vehicle, and is disposed within the width of the chamber in a top view of the vehicle. An exhaust gas sensor arrangement structure characterized by that. A catalyst for purifying engine exhaust gas,
An exhaust gas sensor for detecting an exhaust gas component of the engine;
A chamber located behind the engine;
A joint for connecting the chamber and the muffler,
The catalyst is provided below the engine, and at least a part of the catalyst is disposed in the chamber.
The exhaust gas sensor includes an upstream sensor provided on the upstream side of the catalyst and disposed below the engine, and a downstream sensor provided on the downstream side of the catalyst,
The downstream sensor is disposed in the joint portion,
The exhaust gas sensor arrangement structure, wherein the chamber includes a guide pipe that guides exhaust gas from a rear end of the catalyst to the joint portion. The chamber has a guide pipe for guiding exhaust gas from the downstream of the catalyst to the joint part,
The guide pipe has an upstream end separated from the rear end of the catalyst, while a downstream end extends to the downstream end of the joint part,
It said downstream sensor, the arrangement of the exhaust gas sensor according to claim 2 or claim 3 you characterized in that it is mounted so as to penetrate the joint portion and the guide pipe. A side stand configured to be swingable between a support position for supporting the vehicle and a storage position;
The exhaust gas sensor arrangement structure according to any one of claims 1 to 4 , wherein when the side stand is in the storage position, the downstream sensor overlaps the side stand in a side view of the vehicle.

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