Saddle-type vehicle

Abstract

In a saddle-type vehicle comprising a case housing at least a portion of an exhaust pipe equipped with a catalyst, and an oxygen sensor connected to the case and the exhaust pipe for detecting the oxygen concentration of exhaust gas flowing through the exhaust pipe, the case can be made more space-saving. [Solution] The exhaust pipe 20 has a first pipe 31 in which at least a portion is located inside the case 13 and a first catalyst 41 is located inside it, and a second pipe 32 located inside the case 13 and to which an oxygen sensor 46 is connected. The case 13 has a convex protrusion 13a in a cross section perpendicular to the axis 32c of the second pipe 32, on the side away from the axis 32c of the second pipe 32. The oxygen sensor 46 is connected to the protrusion 13a of the case 13.

Description

【Technical Field】 【0001】 The present invention relates to a saddle-type vehicle. 【Background Art】 【0002】 A saddle-type vehicle such as a motorcycle equipped with an internal combustion engine has an exhaust device that discharges exhaust gas from the internal combustion engine. Conventionally, as an exhaust device, there is known one including an exhaust pipe through which exhaust gas flows, a catalyst disposed inside the exhaust pipe, and an oxygen sensor that detects the oxygen concentration of the exhaust gas. 【0003】 For example, Patent Document 1 describes an exhaust device including a muffler, a second exhaust pipe provided with a catalyst, a fourth exhaust pipe disposed downstream of the second exhaust pipe in the exhaust gas flow direction, and an oxygen sensor. The second exhaust pipe and the fourth exhaust pipe are disposed inside the muffler. The fourth exhaust pipe is provided with a collar to which the oxygen sensor can be attached. The muffler has a recess formed therein, and the collar is disposed in this recess. The oxygen sensor is attached to the recess of the muffler via the collar. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2016-160914 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 In the exhaust system described above, the silencer constitutes a case that houses at least a portion of the exhaust pipe on which the catalyst is installed. Figure 10 schematically shows an exhaust pipe 202 on which the catalyst 201 is installed, a case 203 that houses at least a portion of the exhaust pipe 202, a recess 204 formed in the case 203, and an oxygen sensor 205 positioned in the recess 204. In this way, when the oxygen sensor 205 is connected to the recess 204 of the case 203, a wasted space 206 is created around the oxygen sensor 205 inside the case 203. 【0006】 The object of the present invention is to enable space saving for a saddle-type vehicle comprising a case that houses at least a portion of an exhaust pipe equipped with a catalyst, and an oxygen sensor connected to the case and the exhaust pipe for detecting the oxygen concentration of exhaust gas flowing through the exhaust pipe. [Means for solving the problem] 【0007】 The saddle-type vehicle disclosed herein comprises an internal combustion engine, an exhaust pipe connected to the internal combustion engine for discharging exhaust gas from the internal combustion engine, a first catalyst for purifying the exhaust gas flowing through the exhaust pipe, an oxygen sensor for detecting the oxygen concentration of the exhaust gas flowing through the exhaust pipe, and a case. The exhaust pipe has a first pipe, at least a portion of which is located inside the case and in which the first catalyst is located, and a second pipe, located inside the case and to which the oxygen sensor is connected. The case has a convex portion in a cross section perpendicular to the axis of the second pipe, in the direction away from the axis of the second pipe. The oxygen sensor is connected to the convex portion of the case. 【0008】 In the above-described saddle-type vehicle, the oxygen sensor is connected to a protrusion on the case, so there is less wasted space inside the case and around the oxygen sensor. Therefore, the case can be made more space-saving. 【0009】 The protrusion of the case may be formed in a convex shape toward the axis away from the axis in a cross-section of the case that includes the axis of the second pipe. 【0010】 This further reduces wasted space inside the case and around the oxygen sensor. Therefore, the case can be made even more space-saving. 【0011】 The saddle-type vehicle may include a second catalyst positioned downstream of the first catalyst in the exhaust gas flow direction in the exhaust pipe. The exhaust pipe may have a third pipe, at least a portion of which is located inside the case and which contains the second catalyst. The second pipe may be positioned between the first pipe and the third pipe. 【0012】 As a result, the oxygen sensor detects the oxygen concentration in the exhaust gas after it has been purified by the first catalyst and before it is purified by the second catalyst. 【0013】 The second pipe may have, in a cross-section perpendicular to the axis of the second pipe, a first arc portion having a first curvature and a second arc portion having a second curvature greater than the first curvature. The oxygen sensor may be connected to the second arc portion of the second pipe. 【0014】 As a result, the second arc of the second pipe becomes a convex protrusion relative to the first arc. Similar to the case, the second pipe also has a protrusion. Since the oxygen sensor is connected to the protrusion of the case and the protrusion of the second pipe, it is possible to further suppress the occurrence of wasted space inside the case and around the oxygen sensor. 【0015】 The saddle-type vehicle may include a second catalyst positioned downstream of the first catalyst in the exhaust gas flow direction in the exhaust pipe. The exhaust pipe may have a third pipe, at least a portion of which is located inside the case and which contains the second catalyst, and a fourth pipe, which is located inside the case and positioned between the first pipe and the third pipe. The second pipe may be positioned upstream of the first pipe in the exhaust gas flow direction. 【0016】 As a result, the oxygen sensor detects the oxygen concentration of the exhaust gas before being purified by the first catalyst and the second catalyst. 【0017】 The second pipe may have a first arc portion having a first curvature and a second arc portion having a second curvature larger than the first curvature in a cross section perpendicular to the axis of the second pipe. The oxygen sensor may be connected to the second arc portion of the second pipe. 【0018】 As a result, the second arc portion of the second pipe becomes a convex portion convex with respect to the first arc portion. Similar to the case, the second pipe also has a convex portion. Since the oxygen sensor is connected to the convex portion of the case and the convex portion of the second pipe, it is possible to further suppress the occurrence of unnecessary space inside the case and around the oxygen sensor. 【0019】 The case may constitute at least a part of an exhaust chamber or a muffler that expands the exhaust gas. 【Advantages of the Invention】 【0020】 According to the present invention, in a saddle-riding type vehicle including a case that houses at least a part of an exhaust pipe provided with a catalyst, and an oxygen sensor that is connected to the case and the exhaust pipe and detects the oxygen concentration of the exhaust gas flowing through the exhaust pipe, the case can be made more space-saving. 【Brief Description of the Drawings】 【0021】 [Figure 1] FIG. 1 is a side view of a motorcycle according to an embodiment. [Figure 2] FIG. 2 is a perspective view of an exhaust device according to the first embodiment. [Figure 3] FIG. 3 is a schematic longitudinal sectional view of an exhaust chamber according to the first embodiment. [Figure 4] FIG. 4 is a sectional view taken along line IV-IV of FIG. 3. [Figure 5]FIG. 5 is a schematic longitudinal sectional view of an exhaust chamber according to the second embodiment. [Figure 6] FIG. 6 is a perspective view of an exhaust device according to the third embodiment. [Figure 7] FIG. 7 is a schematic longitudinal sectional view of a muffler according to the third embodiment. [Figure 8] FIG. 8 is a sectional view taken along line VIII-VIII of FIG. 7. [Figure 9] FIG. 9 is a schematic longitudinal sectional view of a muffler according to the fourth embodiment. [Figure 10] FIG. 10 is a schematic sectional view showing a part of a conventional exhaust device. 【BEST MODE FOR CARRYING OUT THE INVENTION】 【0022】 (First Embodiment) Hereinafter, embodiments of a straddle-type vehicle will be described with reference to the drawings. FIG. 1 is a side view of a motorcycle 1 which is an example of a straddle-type vehicle. The motorcycle 1 includes a vehicle body frame 4 having a head pipe 8, an internal combustion engine 5 supported by the vehicle body frame, a seat 9 supported by the vehicle body frame 4, a steering handle 7, a front wheel 2, and a rear wheel 3. The rear wheel 3 is connected to the internal combustion engine 5 via a power transmission mechanism (not shown). The rear wheel 3 is driven by the internal combustion engine 5. 【0023】 As shown in FIG. 2, the motorcycle 1 includes an exhaust device 10 that discharges exhaust gas from the internal combustion engine 5. In FIG. 1, the exhaust device 10 is not shown. The exhaust device 10 is connected to the internal combustion engine 5 and includes an exhaust pipe 20 that discharges exhaust gas from the internal combustion engine 5. As will be described later, the exhaust pipe 20 is composed of a plurality of pipes. The exhaust device 10 also includes an exhaust chamber 12 and a muffler 16. In the following description, with respect to the flow direction of the exhaust gas, the side from which the exhaust gas has flowed will be referred to as the upstream side, and the side to which the exhaust gas is flowing will be referred to as the downstream side. In other words, with respect to the flow path of the exhaust gas, the side of the internal combustion engine 5 will be referred to as the upstream side, and the side of the muffler 16 will be referred to as the downstream side. 【0024】 Although not particularly limited, the internal combustion engine 5 according to this embodiment is a single-cylinder internal combustion engine. The exhaust pipe 20 has an upstream pipe 21 connected to the cylinder of the internal combustion engine 5 and a tapered pipe 27 connected to the downstream end of the upstream pipe 21. The tapered pipe 27 is a pipe whose inner diameter increases towards the downstream side. The first pipe 31 is connected to the downstream end of the tapered pipe 27. 【0025】 The exhaust chamber 12 plays the role of expanding the exhaust gas. The exhaust chamber 12 comprises a hollow case 13. Figure 3 is a schematic longitudinal cross-sectional view of the exhaust chamber 12, schematically representing the case 13 and the internal structure of the case 13. 【0026】 As shown in Figure 3, the first pipe 31 is connected to the case 13. Part of the first pipe 31 is located inside the case 13, and the other part is located outside the case 13. Inside the case 13 are the second pipe 32 and the third pipe 33. The third pipe 33 is located downstream of the first pipe 31. The second pipe 32 is connected to both the first pipe 31 and the third pipe 33. The second pipe 32 is located between the first pipe 31 and the third pipe 33, connecting them. 【0027】 The downstream pipe 28 is connected to case 13. The downstream pipe 28 is located downstream of the third pipe 33. As shown in Figure 2, the downstream pipe 28 is connected to the silencer 16. 【0028】 As shown in Figure 3, a first catalyst 41 is located inside the first pipe 31, and a second catalyst 42 is located inside the third pipe 33. The second catalyst 42 is located downstream of the first catalyst 41. The first catalyst 41 purifies the exhaust gas flowing through the first pipe 31. The second catalyst 42 purifies the exhaust gas flowing through the third pipe 33. Known catalysts conventionally used for purifying exhaust gas can be used for the first catalyst 41 and the second catalyst 42. For example, the first catalyst 41 and the second catalyst 42 can be CO, CH, NO X It may also be a three-way catalyst that converts CO2, H2O, and N2. 【0029】 A cylindrical boss 43 is connected to the tapered pipe 27. A first oxygen sensor 45 for detecting the oxygen concentration of the exhaust gas is attached to the boss 43. The first oxygen sensor 45 is inserted into the boss 43. The first oxygen sensor 45 is connected to the tapered pipe 27 via the boss 43. The first oxygen sensor 45 is located upstream of the first catalyst 41. The first oxygen sensor 45 detects the oxygen concentration of the exhaust gas before it is purified by the first catalyst 41. 【0030】 Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3. In other words, Figure 4 is a cross-sectional view perpendicular to the axis 32c of the second pipe 32. As shown in Figure 4, the case 13 has a convex portion 13a that is convex away from the axis 32c of the second pipe 32. As shown in Figure 2, the convex portion 13a is formed in a shape as if a part of a spherical shell has been cut off. As shown in Figure 3, even in a cross-section including the axis 32c of the second pipe 32, the convex portion 13a is formed convex away from the axis 32c. 【0031】 As shown in Figure 4, the second pipe 32 has a first arc portion 32a having a first curvature and a second arc portion 32b having a second curvature greater than the first curvature. Since the second arc portion 32b has a greater curvature than the first arc portion 32a, the second arc portion 32b is a convex portion that moves away from the axis 32c relative to the first arc portion 32a. The second arc portion 32b is in surface contact with the convex portion 13a of the case 13. The second arc portion 32b is superimposed on the convex portion 13a of the case 13. 【0032】 A cylindrical boss 44 is connected to the protrusion 13a of case 13 and the second arc portion 32b of the second pipe 32. The method of connecting the boss 44 to the protrusion 13a and the second arc portion 32b is not particularly limited, but here the boss 44 is welded to the protrusion 13a and the second arc portion 32b. A second oxygen sensor 46 for detecting the oxygen concentration of exhaust gas is attached to the boss 44. The second oxygen sensor 46 is inserted into the boss 44. The second oxygen sensor 46 is connected to the protrusion 13a and the second arc portion 32b via the boss 44. As shown in Figure 3, the second oxygen sensor 46 is located downstream of the first catalyst 41 and upstream of the second catalyst 42. The second oxygen sensor 46 detects the oxygen concentration of exhaust gas after it has been purified by the first catalyst 41 and before it has been purified by the second catalyst 42. For example, by comparing the oxygen concentration detected by the first oxygen sensor 45 with the oxygen concentration detected by the second oxygen sensor 46, the degree of degradation of the first catalyst 41 can be determined. 【0033】 As shown in Figure 3, the second oxygen sensor 46 is configured to detect the oxygen concentration of the exhaust gas inside the second pipe 32. As shown in Figure 4, the outer surface of the second pipe 32 is curved in a cross-section perpendicular to the axis 32c. If the second pipe 32 were to contact the flat surface of the case 13, the second pipe 32 and the case 13 would be in point contact. On the other hand, according to this embodiment, the case 13 has a protrusion 13a. The second pipe 32 is in contact with the protrusion 13a of the case 13. Therefore, the second pipe 32 and the case 13 are in surface contact. The contact area between the second pipe 32 and the case 13 is relatively large. The boss 44 is connected to the protrusion 13a, which is the part of the case 13 that has a large contact area with the second pipe 32. 【0034】 As described above, according to this embodiment, the second oxygen sensor 46 is connected to the protrusion 13a of the case 13 via the boss 44. Therefore, wasted space is less likely to occur inside the case 13 and around the second oxygen sensor 46. Thus, the case 13 of the exhaust chamber 12 can be made more space-saving. 【0035】 Furthermore, since the contact area between the protrusion 13a of case 13 and the second pipe 32 is relatively large, good welding can be achieved when welding case 13 and the second pipe 32. Also, since it is easier to provide the protrusion 13a on case 13 than to provide a recess, the manufacturing of case 13 is easier. In addition, unlike a recess, water does not accumulate on the protrusion 13a, so if rainwater or other water falls on case 13, it is possible to prevent water from accumulating around the second oxygen sensor 46. 【0036】 The protrusion 13a is formed in a convex shape away from the axis 32c of the second pipe 32 in a cross section perpendicular to the axis 32c of the second pipe 32 (see Figure 4). The protrusion 13a does not necessarily have to be formed in a convex shape away from the axis 32c in a cross section that includes the axis 32c. However, according to this embodiment, the protrusion 13a is formed in a convex shape away from the axis 32c in both a cross section perpendicular to the axis 32c and a cross section that includes the axis 32c (see Figure 3). This further suppresses the creation of wasted space inside the case 13 and around the second oxygen sensor 46. Therefore, the case 13 of the exhaust chamber 12 can be made even more space-saving. 【0037】 As shown in Figure 4, according to this embodiment, the second pipe 32 has a first arc portion 32a and a second arc portion 32b. The second oxygen sensor 46 is connected to the second arc portion 32b via a boss 44. Here, the curvature of the second arc portion 32b is greater than the curvature of the first arc portion 32a. The second arc portion 32b is a convex portion that protrudes further away from the axis 32c than the first arc portion 32a. The second arc portion 32b is superimposed on the convex portion 13a of the case 13. Therefore, no wasted space is created between the convex portion 13a of the case 13 and the second arc portion 32b. According to this embodiment, it is possible to further suppress the creation of wasted space inside the case 13 and around the second oxygen sensor 46. 【0038】 In this embodiment, one set of tapered pipe 27, first pipe 31, second pipe 32, and third pipe 33 is provided. One set of first oxygen sensor 45 and second oxygen sensor 46 is provided. However, the number of these is not particularly limited and can be appropriately set according to, for example, the number of cylinders of the internal combustion engine 5. For example, if the internal combustion engine 5 has two cylinders, two sets of tapered pipe 27, first pipe 31, second pipe 32, third pipe 33, first oxygen sensor 45, and second oxygen sensor 46 may be provided. Inside the case 13 of the exhaust chamber 12, there may be two sets each of the first pipe 31, second pipe 32, and third pipe 33, and two second oxygen sensors 46 may be connected to the case 13. If the number of cylinders in the internal combustion engine 5 is even greater, three or more sets of tapered pipes 27, first pipe 31, second pipe 32, third pipe 33, first oxygen sensor 45, and second oxygen sensor 46 may be provided. 【0039】 In this embodiment, as shown in Figure 3, only a portion of the first pipe 31 is placed inside the case 13, but it is also possible to place the entire first pipe 31 inside the case 13. Furthermore, in this embodiment, the entire third pipe 33 is placed inside the case 13, but it is also possible to place only a portion of the third pipe 33 inside the case 13. 【0040】 (Second Embodiment) In the first embodiment, a portion of the first piping 31 was located outside the case 13 of the exhaust chamber 12 (see Figure 3). In contrast, in the second embodiment, the entire first piping 31 is located inside the case 13 of the exhaust chamber 12. In the following description, the same reference numerals will be used for parts similar to those in the first embodiment, and their descriptions will be omitted. 【0041】 Figure 5 is a schematic longitudinal cross-sectional view of the exhaust chamber 12 according to the second embodiment. In this embodiment, a portion of the tapered pipe 27 is located inside the case 13 of the exhaust chamber 12. The entirety of the first pipe 31, the entirety of the second pipe 32, and the entirety of the third pipe 33 are located inside the case 13. However, a portion of the third pipe 33 may be located outside the case 13. 【0042】 Case 13 has a protrusion 13b similar to the protrusion 13a. The protrusion 13b is formed convex toward the axis 27c in both the cross section perpendicular to the axis 27c of the tapered tube 27 and the cross section including the axis 27c. In the cross section perpendicular to the axis 27c, the tapered tube 27 has a first arc portion 27a and a second arc portion 27b. The curvature of the second arc portion 27b is greater than the curvature of the first arc portion 27a. The second arc portion 27b is a convex protrusion toward the axis 27c relative to the first arc portion 27a. The second arc portion 27b is superimposed on the protrusion 13b of case 13. The second arc portion 27b and the protrusion 13b are in surface contact. The boss 43 into which the first oxygen sensor 45 is inserted is connected to the protrusion 13b and the second arc portion 27b. The first oxygen sensor 45 is connected to the protrusion 13b of the case 13 and the second arc portion 27b of the tapered tube 27 via the boss 43. 【0043】 The other components are the same as in the first embodiment, so we will omit their explanation. 【0044】 In this embodiment, the first oxygen sensor 45 is connected to the protrusion 13b of the case 13 via a boss 43, and the second oxygen sensor 46 is connected to the protrusion 13a of the case 13 via a boss 44. Therefore, wasted space is less likely to occur inside the case 13 and around the first oxygen sensor 45, and inside the case 13 and around the second oxygen sensor 46. Thus, the case 13 of the exhaust chamber 12 can be made more space-saving. In addition, the same effects as in the first embodiment can be obtained in this embodiment as well. 【0045】 In this embodiment as well, the tapered pipe 27, the first pipe 31, the second pipe 32, and the third pipe 33 may be provided in two or more sets, or only in one set. 【0046】 (Third embodiment) In the first embodiment, an oxygen sensor (second oxygen sensor 46) was provided in the exhaust chamber 12 (see Figure 3). In contrast, in the third embodiment, the oxygen sensor was provided in the silencer 16 (see Figure 6). In this embodiment, the exhaust chamber 12 may or may not be present. 【0047】 Figure 7 is a schematic longitudinal cross-sectional view of the silencer 16 according to the third embodiment. Figure 8 is a cross-sectional view taken along line VIII-VIII in Figure 7. The silencer 16 includes a hollow case 17. The cross-sectional shape of the case 17 is not particularly limited. The cross-sectional shape of the case 17 may be a perfect circle, as shown in Figure 8, or it may be an oval. As shown in Figure 7, in this embodiment, a part of the first pipe 31, the entirety of the second pipe 32, and the entirety of the third pipe 33 are arranged inside the case 17. However, as will be described later, the entirety of the first pipe 31 may be arranged inside the case 17, and a part of the third pipe 33 may be arranged outside the case 17. 【0048】 Case 17 has a convex portion 17a that is positioned away from the axis 32c of the second pipe 32. The convex portion 17a has the same shape as the convex portion 13a of the case 13 of the exhaust chamber 12 described above. The convex portion 17a is formed in a convex shape away from the axis 32c in both a cross section perpendicular to the axis 32c (see Figure 8) and a cross section including the axis 32c (see Figure 7). The convex portion 17a is superimposed on the second arc portion 32b of the second pipe 32. 【0049】 As shown in Figure 7, the first oxygen sensor 45 is connected to the downstream pipe 28B via a boss 43. The first oxygen sensor 45 detects the oxygen concentration of the exhaust gas before it is purified by the first catalyst 41. The second oxygen sensor 46 is connected to the protrusion 17a of the case 17 and the second arc portion 32b of the second pipe 32 via a boss 44 (see Figure 8). The second oxygen sensor 46 detects the oxygen concentration of the exhaust gas after it has been purified by the first catalyst 41 and before it is purified by the second catalyst 42. 【0050】 The other components are the same as in the first embodiment, so we will omit their explanation. 【0051】 According to this embodiment, the second oxygen sensor 46 is connected to the protrusion 17a of the case 17 of the silencer 16 via the boss 44. Therefore, wasted space is less likely to occur inside the case 17 and around the second oxygen sensor 46. Thus, the case 17 of the silencer 16 can be made more compact. In addition, the same effects as in the first embodiment can be obtained in this embodiment as well. 【0052】 In this embodiment as well, the downstream pipe 28B, the first pipe 31, the second pipe 32, and the third pipe 33 may be provided as one set or as two or more sets. 【0053】 (Fourth Embodiment) In the third embodiment, a portion of the first piping 31 was located outside the case 17 of the silencer 16 (see Figure 7). In contrast, in the fourth embodiment, the entire first piping 31 was located inside the case 17 of the silencer 16. 【0054】 Figure 9 is a schematic longitudinal cross-sectional view of the silencer 16 according to the fourth embodiment. In this embodiment, a portion of the downstream pipe 28B is located inside the case 17 of the silencer 16. The entirety of the first pipe 31, the entirety of the second pipe 32, and the entirety of the third pipe 33 are located inside the case 17. However, a portion of the third pipe 33 may be located outside the case 17. 【0055】 Case 17 has a protrusion 17b similar to the protrusion 17a. The protrusion 17b is formed convex toward the axis 28c in both the cross section perpendicular to the axis 28c of the downstream pipe 28B and the cross section including the axis 28c. The downstream pipe 28B has a first arc portion 28a and a second arc portion 28b in the cross section perpendicular to the axis 28c. The curvature of the second arc portion 28b is greater than the curvature of the first arc portion 28a. The second arc portion 28b is a convex protrusion toward the axis 28c relative to the first arc portion 28a. The second arc portion 28b is superimposed on the protrusion 17b of case 17. The second arc portion 28b and the protrusion 17b are in surface contact. The boss 43 into which the first oxygen sensor 45 is inserted is connected to the protrusion 17b and the second arc portion 28b. The first oxygen sensor 45 is connected via a boss 43 to a protrusion 17b of the case 17 and a second arc portion 28b of the downstream pipe 28B. 【0056】 The other components are the same as in the third embodiment, so we will omit their explanation. 【0057】 In this embodiment, the first oxygen sensor 45 is connected to the protrusion 17b of the case 17 via a boss 43, and the second oxygen sensor 46 is connected to the protrusion 17a of the case 17 via a boss 44. Therefore, wasted space is less likely to occur inside the case 17 and around the first oxygen sensor 45, and inside the case 17 and around the second oxygen sensor 46. Thus, the case 17 of the silencer 16 can be made more compact. In addition, the same effects as in the first embodiment can be obtained in this embodiment as well. 【0058】 In this embodiment as well, the downstream pipe 28B, the first pipe 31, the second pipe 32, and the third pipe 33 may be provided as one set or as two or more sets. 【0059】 The above describes embodiments of the saddle-type vehicle, but the first to fourth embodiments mentioned above are merely examples. Many other embodiments are also possible. 【0060】 In each of the above embodiments, the motorcycle 1 is equipped with a first oxygen sensor 45 and a second oxygen sensor 46. However, in the first embodiment (see Figure 3) or the third embodiment (see Figure 7), the first oxygen sensor 45 may be omitted. Also, in the second embodiment (see Figure 5) or the fourth embodiment (see Figure 9), either the first oxygen sensor 45 or the second oxygen sensor 46 may be omitted. 【0061】 In the first to fourth embodiments, either the first pipe 31 or the third pipe 33 may be omitted, and either the first catalyst 41 or the second catalyst 42 may be omitted. 【0062】 In the first to fourth embodiments, the second pipe 32 does not have to have a second arc portion 32b. The cross-sectional shape of the second pipe 32 may be formed in a circular shape. 【0063】 A saddle-type vehicle is a vehicle that the rider straddles to ride. A saddle-type vehicle is not limited to a motorcycle. A saddle-type vehicle may also be, for example, a three-wheeled vehicle, an ATV (All Terrain vehicle), or a snowmobile. [Explanation of symbols] 【0064】 1 Motorcycle (saddle-type vehicle), 5 Internal combustion engine, 12 Exhaust chamber, 13 Case, 13a Protrusion, 13b Protrusion, 16 Silencer, 17 Case, 17a Protrusion, 17b Protrusion, 20 Exhaust pipe, 27 Tapered pipe (second piping), 27a First arc section, 27b Second arc section, 31 First piping, 32 Second piping (second piping, fourth piping), 32a First arc section, 32b Second arc section, 33 Third piping, 41 First catalyst, 42 Second catalyst, 45 First oxygen sensor (oxygen sensor), 46 Second oxygen sensor (oxygen sensor)

Claims

[Claim 1] Internal combustion engines and An exhaust pipe connected to the internal combustion engine and for discharging exhaust gas from the internal combustion engine, A first catalyst for purifying exhaust gas flowing through the aforementioned exhaust pipe, An oxygen sensor for detecting the oxygen concentration of exhaust gas flowing through the exhaust pipe, Equipped with a case, The exhaust pipe comprises a first pipe, at least a portion of which is located inside the case and which contains the first catalyst, and a second pipe, which is located inside the case and to which the oxygen sensor is connected. The case has a convex portion in a cross-section perpendicular to the axis of the second pipe, in the direction away from the axis of the second pipe. The oxygen sensor is connected to the protrusion of the case, in a saddle-type vehicle. [Claim 2] The saddle-type vehicle according to claim 1, wherein the protrusion of the case is formed in a convex shape toward the axis away from the axis in a cross-section of the case that includes the axis of the second pipe. [Claim 3] The exhaust pipe comprises a second catalyst positioned downstream of the first catalyst in the direction of exhaust gas flow, The exhaust pipe has a third pipe in which at least a portion is located inside the case and the second catalyst is located inside it. The saddle-type vehicle according to claim 1, wherein the second pipe is located between the first pipe and the third pipe. [Claim 4] The second pipe has, in a cross-section perpendicular to the axis of the second pipe, a first arc portion having a first curvature and a second arc portion having a second curvature greater than the first curvature. The saddle-type vehicle according to claim 3, wherein the oxygen sensor is connected to the second arc portion of the second piping. [Claim 5] The exhaust pipe comprises a second catalyst positioned downstream of the first catalyst in the direction of exhaust gas flow, The exhaust pipe comprises a third pipe, at least a portion of which is located inside the case and in which the second catalyst is located, and a fourth pipe, located inside the case and positioned between the first pipe and the third pipe. The saddle-type vehicle according to claim 1, wherein the second pipe is located upstream of the first pipe in the direction of exhaust gas flow. [Claim 6] The second pipe has, in a cross-section perpendicular to the axis of the second pipe, a first arc portion having a first curvature and a second arc portion having a second curvature greater than the first curvature. The saddle-type vehicle according to claim 5, wherein the oxygen sensor is connected to the second arc portion of the second piping. [Claim 7] The saddle-type vehicle according to claim 1, wherein the case constitutes at least a part of an exhaust chamber or silencer that expands the exhaust gas.

Images