Saddle-type vehicle

Abstract

Provided is a saddle-type vehicle comprising a vehicle body frame F, a unit swing engine P swingably supported by the vehicle body frame F via a link member 11, and an exhaust device 50 equipped with an exhaust pipe 51 and a catalyst device 53. The exhaust pipe 51 extends downward from the unit swing engine P and comprises a catalyst device-accommodating exhaust pipe 100, an upstream exhaust pipe 80, and a downstream exhaust pipe 90. An exhaust gas sensor S1 is arranged in the downstream exhaust pipe 90. In a side view of the vehicle body, the exhaust gas sensor S1 and the catalyst device 53 are positioned in an area between a first virtual line L1 connecting the center of rotation CL of a crankshaft 21 and a link member-connecting section 13 connecting the link member 11 to the vehicle body frame F and a second virtual line L2 connecting the link member-connecting section 13 and an exhaust pipe connection section 24c to which the end of the exhaust pipe 51 is connected. The saddle-type vehicle thus enables early warm-up of the exhaust gas sensor, suppresses exhaust gas turbulence in the pipe, and improves the accuracy of the exhaust gas sensor.

Description

[Technical Field]

[0001] The present invention relates to a straddle-type vehicle equipped with a unit swing engine. [Background technology]

[0002] A conventional saddle-type vehicle is disclosed that is equipped with a unit swing engine, has a catalytic device disposed midway in an exhaust pipe connected to the internal combustion engine of the unit swing engine, and has an exhaust gas sensor disposed upstream of the catalytic device in the exhaust pipe (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication WO 2018 / 025652 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional saddle-type vehicles, exhaust gas sensors are installed in the exhaust pipe upstream of the catalytic converter to measure the oxygen concentration of the exhaust gas before it passes through the catalytic converter, but measuring the exhaust gas after it has passed through the catalytic converter allows for more accurate detection of the oxygen concentration in the exhaust gas. On the other hand, if an exhaust gas sensor is installed in the exhaust pipe downstream of the catalytic converter, depending on its installation position, it may be farther away from the internal combustion engine, making it difficult to warm up the exhaust gas sensor quickly. Also, if the exhaust gas sensor is installed close to the exhaust pipe's open-air port, when negative pressure occurs inside the exhaust pipe, outside air flowing in from the open-air port disrupts the flow of exhaust gas inside the exhaust pipe, affecting the detection accuracy of the exhaust gas sensor. [Means for solving the problem]

[0005] The present invention has been made in consideration of the above-mentioned problems, and provides a unit swing engine having a body frame, a cylinder portion arranged with a cylinder axis facing forward, a crankcase, and a crankshaft, the unit swing engine being swingably supported by the body frame via a link member; an exhaust system connected to the unit swing engine and including an exhaust pipe and a catalytic converter disposed midway through the exhaust pipe; The exhaust pipe extends downward from the unit swing engine, the exhaust pipe includes a catalytic converter-accommodating exhaust pipe that accommodates the catalytic converter therein, an upstream exhaust pipe connected to the upstream side of the catalytic converter-accommodating exhaust pipe, and a downstream exhaust pipe connected to the downstream side of the catalytic converter-accommodating exhaust pipe, an exhaust gas sensor is disposed in the downstream exhaust pipe; The exhaust gas sensor and the catalytic converter are configured as follows when viewed from the side of the vehicle body: a first imaginary line connecting a link member connecting portion that connects the link member to the body frame and a rotation center of the crankshaft; This is a saddle-type vehicle characterized in that it is located in an area between a second imaginary line connecting the exhaust pipe connection portion of the unit swing engine to which the end of the exhaust pipe is connected and the link member connection portion.

[0006] According to the above configuration, by providing an exhaust gas sensor in the downstream exhaust pipe downstream of the catalytic device, it is possible to measure the exhaust gas after it has passed through the catalytic device and detect the oxygen concentration in the exhaust gas more accurately. In addition, by shortening the distance between the exhaust gas sensor and the internal combustion engine, it is possible to warm up the exhaust gas sensor earlier. Furthermore, since the exhaust gas sensor is positioned far from the atmospheric opening of the exhaust pipe, even if the flow of exhaust gas in the exhaust pipe is disturbed by outside air flowing in from the atmospheric opening when the exhaust pipe becomes negative pressure, this does not affect the detection accuracy of the exhaust gas sensor, and the accuracy of the exhaust gas sensor can be improved.

[0007] Furthermore, in the present invention, at least a portion of the downstream exhaust pipe is located on an extension line of the body frame when viewed from below the vehicle, In a front view of the vehicle, at least a portion of the exhaust gas sensor overlaps with the body frame.

[0008] According to the above configuration, when viewed from below the vehicle, at least a portion of the downstream exhaust pipe is located on an extension of the body frame, and when viewed from the front of the vehicle, at least a portion of the exhaust gas sensor overlaps with the body frame, thereby providing protection from obstacles such as flying stones from the front of the vehicle.

[0009] In addition, in the present invention, the downstream exhaust pipe is located outward in a vehicle width direction from the crankcase in a bottom view of the vehicle, The crankcase has an oil filter that is taken out toward the side of the vehicle, The exhaust gas sensor is characterized in that it is disposed on a downstream exhaust pipe further forward of the oil filter in a side view of the vehicle.

[0010] According to the above configuration, when the oil filter 66 is removed toward the side of the vehicle, the work can be easily performed without the exhaust gas sensor S1 becoming an obstacle.

[0011] Furthermore, the present invention provides a vehicle engine having a fan that introduces outside air into the unit swing engine, and a fan cover that covers the fan from the side of the vehicle, The downstream exhaust pipe does not overlap with an outside air inlet of the fan cover in a side view of the vehicle.

[0012] According to the above configuration, the downstream exhaust pipe is positioned so that it does not overlap with the outside air inlet of the fan cover when viewed from the side of the vehicle, making it difficult for warmed air around the downstream exhaust pipe to be drawn into the power unit, thereby improving the cooling efficiency of the power unit by the fan.

[0013] In the present invention, a mesh portion is provided on the outer edge of the fan cover.

[0014] According to the above configuration, the fan exhausts air from inside the fan cover through the mesh portion on the outer edge of the fan cover, so that the air can be directed at the downstream exhaust pipe near the fan cover to cool it, thereby increasing the rigidity of the metal that makes up the exhaust pipe.

[0015] Furthermore, the present invention is characterized in that at least a portion of the exhaust pipe has a divided body structure.

[0016] According to the above configuration, by making the exhaust pipe a divided structure, it becomes easier to form a curved portion with a small curvature, and there are fewer restrictions on the curvature of the piping.

[0017] Furthermore, the present invention is directed to a method for manufacturing a vehicle having an exhaust pipe, the exhaust pipe having a divided body structure having at least two divided portions, At least one divided body structure is a divided body structure in which divided end edges of each divided body are joined together by a joint structure to form an integrated body, Another divided body structure is characterized in that the divided end edge of one divided body has a jockle portion that protrudes outward to fit into the divided end edge of the other divided body, and the divided end edge of one divided body and the divided end edge of the other divided body are joined together by a jockle fitting structure to form a single unit.

[0018] According to the above configuration, the joint area between the segments is larger in a segment structure joined by a jockle joint than in a segment structure joined by a clasp joint. Therefore, if all of the segment structures at two or more locations are only segment structures with a jockle joint, the joint between the halves is stronger than in a segment structure with a clasp joint. However, when the curved portion of the metal exhaust pipe is subjected to heat damage and a force that returns it to a straight shape, stress concentrates at the joint between the segments. By making some of the segment structures provided in the exhaust pipe segments joined by a clasp joint, rigidity can be reduced and stress can be dispersed. [Effects of the Invention]

[0019] According to the present invention, by installing an exhaust gas sensor in the downstream exhaust pipe downstream of the catalytic device, it is possible to measure the exhaust gas after it has passed through the catalytic device and detect the oxygen concentration in the exhaust gas more accurately, and by shortening the distance between the exhaust gas sensor and the internal combustion engine, it is possible to warm up the exhaust gas sensor earlier.Furthermore, since the exhaust gas sensor is positioned far from the atmospheric opening of the exhaust pipe, even if the flow of exhaust gas in the exhaust pipe is disturbed by outside air flowing in from the atmospheric opening when the exhaust pipe becomes negative pressure, this does not affect the detection accuracy of the exhaust gas sensor, and the accuracy of the exhaust gas sensor can be improved. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is an overall left side view of a motorcycle to which an intake structure for an internal combustion engine according to one embodiment of the present invention is applied; [Figure 2] FIG. 2 is an enlarged right side view of a main part of the vehicle shown in FIG. [Figure 3] FIG. 2 is a left side view of the power unit, the intake system device, and the exhaust system shown in FIG. [Figure 4] FIG. 3 is a plan view of FIG. 2. [Figure 5] FIG. [Figure 6] FIG. 2 is a partial cross-sectional view taken along the crankshaft of the internal combustion engine of the power unit. [Figure 7] 3 is an enlarged left side view of a main part of the vehicle shown in FIG. 2, showing a state in which an internal combustion engine is suspended from a body frame. [Figure 8] FIG. 2 is a front view of the main part of the vehicle with the cover removed, as viewed from the front. [Figure 9] FIG. 2 is a perspective view showing a part of an exhaust pipe. [Figure 10] FIG. 2 is a front view of the exhaust pipe, with a first upstream exhaust pipe shown in phantom lines. [Figure 11] 10 is a cross-sectional view taken along the line XI-XI in FIG. 9. [Figure 12] FIG. 10 is a cross-sectional view taken along the line XII-XII in FIG. 9. [Figure 13]10A and 10B are diagrams showing other mounting positions of the exhaust gas sensor. [Figure 14] FIG. 10 is a diagram showing still another installation position of the exhaust gas sensor. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of a saddle-ride type vehicle according to the present invention will now be described with reference to Figures 1 to 14. The saddle-ride type vehicle of this embodiment is a scooter-type motorcycle 1, the left side view of which is shown in Figure 1. In the explanations in this specification, the directions of front, back, left, right, and up and down will follow the usual standard of the straight-ahead direction of the motorcycle 1 in this embodiment being the forward direction, and in the drawings, FR indicates the forward direction, RE indicates the rearward direction, LH indicates the leftward direction, RH indicates the rightward direction, UP indicates the upward direction, and DW indicates the downward direction.

[0022] As shown in FIG. 1, the motorcycle 1 has a front body 1F and a rear body 1R connected via a low floor portion 1C, and the body frame F, which forms the skeleton of the body, is generally composed of a down tube 3 and a main pipe 4. That is, a down tube 3 extends downward from a head pipe 2 at the front part 1F of the vehicle body, bends horizontally at its lower end and extends rearward below the floor part 1C, and is connected at its rear end to a pair of left and right main pipes 4, which form an inclined section 4a that extends diagonally upward and rearward from the connected section, and the upper part of the inclined section 4a is further bent to form a horizontal section 4b that extends rearward approximately horizontally.

[0023] A storage box 5 is supported in front between the pair of main pipes 4, and a fuel tank (not shown) is supported in the rear, with a seat 7 covering the storage box 5 and the fuel tank. At the front body 1F, a handlebar 8 is provided above and journaled on the head pipe 2, and a front fork 9 extends below, with a front wheel 10 journaled at its lower end.

[0024] At the front body part 1F, the head pipe 2 and the upper and lower directional portions of the down tube 3 are covered from the front and rear by a front cover 1a and a leg shield 1b, at the floor part 1C, the front and rear directional portions of the down tube 3 are covered by a lower side cover 1c, and at the rear body part 1R, the main pipe 4 is covered on the left, right and rear sides by a body cover 1d.

[0025] The motorcycle 1 is equipped with a power unit P as a unit swing engine located below the main pipe 4. As shown in FIG. 3, the power unit P has a single-cylinder, four-stroke, air-cooled internal combustion engine 20 disposed in the front portion thereof and a belt-type continuously variable transmission disposed in the rear portion thereof.

[0026] 7, the power unit P is provided with a pair of left and right engine hangers 22h that protrude forward from the upper part of the crankcase 22. A link member 11 protrudes from the rear of the main pipe 4, and ends of the engine hangers 22h are connected to the link member 11 via a pivot shaft 12, so that the power unit P is connected and supported to the body frame F in a swingable manner.

[0027] 3, the internal combustion engine 20 is configured by stacking a crankcase 22, a cylinder block 23, a cylinder head 24, and a head cover 25 in that order, with the cylinder axis C projecting forward and tilting forward to a nearly horizontal position. A crankshaft 21 is rotatably supported in the crankcase 22 and oriented in the vehicle width direction.

[0028] 1, an intake port 24a is formed on the upper surface of the cylinder head 24, and an inlet pipe 31 serving as an intake pipe extends upward from the intake port 24a. An exhaust port 24b is formed on the lower surface of the cylinder head 24, and an exhaust pipe 51 extends downward from the exhaust port 24b. In addition, an ignition plug 26 is inserted into the cylinder head 24 near the center head cover 25 as shown in FIG. 3, and an oxygen concentration sensor 27 is inserted into the location where the exhaust pipe 51 extends as shown in FIG.

[0029] Referring to Figure 6, the crankcase 22 is split into left and right parts, a left crankcase part 22L and a right crankcase part 22R, and the crankshaft 21 oriented in the vehicle width direction is rotatably supported by the left crankcase part 22L and the right crankcase part 22R via main bearings 21b, 21b, respectively.

[0030] An AC generator 55 is provided on the right shaft portion of the crankshaft 21, and a centrifugal cooling fan 56 is integrally attached to an outer rotor 55r of the AC generator 55. A fan cover 57 that covers the right crankcase portion 22R from the right side houses the centrifugal cooling fan 56 inside. Referring also to Figure 2, the fan cover 57 has a grill 57g that serves as an outside air inlet, facing the centrifugal cooling fan 56. As shown in Figure 2, the fan cover 57 has a mesh portion 57f formed in an area diagonally below and rear of an outer edge 57e that surrounds the grill 57g. The outside air introduced through the grill 57g is discharged to the outside of the fan cover 57 through the mesh portion 57f by the rotational force of the centrifugal cooling fan 56.

[0031] As shown in FIGS. 2 and 6, a shroud 70 surrounds the cylinder block 23 and the cylinder head 24, and the shroud 70 is connected to the fan cover 57 on the right side.

[0032] 6, the left crankcase 22L extends rearward and doubles as a transmission case, and a transmission case cover 65 covers the transmission case (left crankcase) 22L from the left side, with a belt-type continuously variable transmission 60 disposed inside. A drive chain sprocket 58 is provided adjacent to the main bearing 21b on the left shaft portion of the crankshaft 21, and a drive pulley 61 of the belt-type continuously variable transmission 60 is provided on the end of the left shaft. Power is transmitted to a valve mechanism on the cylinder head 24 side by a cam chain 59 wound around the drive chain sprocket 58.

[0033] 1 and 3, the reduction gear output shaft of the reduction gear mechanism 64 provided at the rear of the belt-type continuously variable transmission 60 is the rear axle 28a, and the rear wheel 28 is provided on the rear axle 28a. A rear cushion (not shown) is interposed between the upper end of the rear part of the transmission case 22L that houses the reduction gear mechanism 64 and the upper bent part of the main pipe 4.

[0034] 3, a driven pulley 63 of the belt-type continuously variable transmission 60 is journaled on a reducer input shaft 64a of the reduction mechanism 64, a belt 62 is wound around a drive pulley 61 provided on the crankshaft 21 and the driven pulley 63 provided on the reducer input shaft 64a, and the power of the internal combustion engine 20 is transmitted to the driven pulley 63 via the belt 62, and the rotation of the driven pulley 63 is transmitted to the reducer input shaft 64a of the reduction mechanism 64 via a centrifugal clutch (not shown), and is then reduced in speed by the reduction mechanism 64 before being transmitted to the rear wheel 28. As shown in FIG. 6, an outside air intake fan 61F is formed on the left pulley half of the drive pulley 61.

[0035] As shown in FIG. 2, an oil filter 66 is disposed below the crankcase 22 and extends out toward the side of the vehicle. The oil filter 66 filters the oil supplied to various parts of the internal combustion engine 20.

[0036] 1, an intake device 30 that draws in outside air and sends it to the internal combustion engine 20 is connected to an intake port 24a of the internal combustion engine 20. Also referring to Figure 4, the intake device 30 includes an air cleaner device 40 that takes in and purifies the outside air, a connecting tube 36 that is connected to the air cleaner device 40, a throttle body 33 that is connected to the downstream side of the connecting tube 36, and an inlet pipe 31 that is connected to the upstream side of the throttle body 33 and has a butterfly-type throttle valve (not shown) provided therein, and these components form an intake system. As shown in Figure 4, a fuel injection valve 37 that injects fuel into the intake passage is provided in the intake port 24a and the inlet pipe 31.

[0037] The intake device 30 will now be described in further detail. As shown in Figure 4, the air cleaner device 40 of the intake device 30 has an air cleaner case 41 which is formed by combining left and right unpurified chamber cases 42 and purified chamber cases 43, and a partition section 45 which is disposed between the unpurified chamber case 42 and the purified chamber case 43 and in which an air cleaner element 44 is disposed, dividing the air cleaner element 44 into an unpurified chamber Ca on the unpurified chamber case 42 side and a purified chamber Cb on the purified chamber case 43 side.

[0038] 3, an air intake pipe 47 that takes in airflow from running is disposed in the unpurified chamber case 42 with its opening 47a facing forward. The intake air introduced through the opening 47a passes through the unpurified chamber Ca and the air cleaner element 44, where it is purified, and then sent to the purified chamber Cb. The purified chamber Cb of the air cleaner device 40 is connected to the throttle body 33 by an elastically deformable connecting tube 36 made of rubber.

[0039] As shown in Fig. 1, an exhaust device 50 is connected to the downstream end of the exhaust port 24b of the cylinder head 24. Referring to Fig. 5, an exhaust pipe connection portion 24c to which the upstream of the exhaust device 50 is connected is provided on the underside of the cylinder head 24. The exhaust device 50 includes an exhaust pipe 51 connected to the exhaust port 24b of the internal combustion engine 20 and discharging exhaust gas, a catalytic converter 53 disposed midway inside the exhaust pipe 51 and purifying the exhaust gas, and a muffler 52 connected downstream of the exhaust pipe 51, these components forming an exhaust system.

[0040] 2 and 5, exhaust pipe 51 communicates with exhaust port 24b, extends downward from the underside of cylinder head 24, bends diagonally forward to the left, curves further rearward, bends to the right, runs along the lower part of crankcase 22 from left to right, bends further rearward, extends rearward, and is connected to muffler 52 disposed on the right side of rear wheel 28. A catalytic device 53 is provided midway through exhaust pipe 51, and exhaust pipe 51 is made up of a catalytic device-accommodating exhaust pipe 100 that accommodates catalytic device 53, an upstream exhaust pipe 80 connected to the upstream side of catalytic device-accommodating exhaust pipe 100, and a downstream exhaust pipe 90 connected to the downstream side of catalytic device-accommodating exhaust pipe 100.

[0041] 5, in a bottom view of the vehicle, at least a portion of the downstream exhaust pipe 90 is located on an extension of the body frame F, and is positioned outward in the vehicle width direction than the crankcase 22. Furthermore, as shown in FIG. 2, the downstream exhaust pipe 90 is positioned so as not to overlap with the grill 57g, which serves as an outside air inlet of the fan cover 57, in a side view, so that heated air around the exhaust pipe 51 is not introduced.

[0042] Exhaust gas emitted from the internal combustion engine 20 passes through the upstream exhaust pipe 80 from the exhaust port 24b, and is purified by passing through the catalytic device 53 in the catalytic device-accommodating exhaust pipe 100. Thereafter, the exhaust gas passes through the downstream exhaust pipe 90 and the muffler 52, and is discharged into the outside air from the atmosphere-opening port 52a of the muffler 52. The catalytic device 53 is a honeycomb-shaped porous structure having many pores extending along its axial direction, and supports, for example, platinum, rhodium, or palladium as a catalyst that decomposes exhaust gas components.

[0043] 9 and 10 show the main part of the exhaust pipe 51. The upstream exhaust pipe 80 of the exhaust pipe 51 includes a vertical section 80a extending downward from the exhaust pipe connection section 24c of the cylinder head 24, a lateral extension section 80b extending in front of the catalytic device 53 to the other side of the cut surface of the crankcase, and a curved section 80c that curves rearward from the downstream end of the lateral extension section 80b and to one side of the cut surface of the crankcase and then folds back in a U-shape, and the downstream end of the curved section 80c is connected to the catalytic device-accommodated exhaust pipe 100.

[0044] 9, the upstream exhaust pipe 80 is made up of a first upstream exhaust pipe 81 connected to the exhaust port 24b, and a second upstream exhaust pipe 82 connected to a downstream end 81b of the first upstream exhaust pipe 81. The upstream exhaust pipe 80 is divided into the first upstream exhaust pipe 81 and the second upstream exhaust pipe 82 midway along a curved portion 80c of the upstream exhaust pipe 80.

[0045] An upstream end 82a of the second upstream exhaust pipe 82 has a larger diameter than a downstream end 81b of the first upstream exhaust pipe 81. The first upstream exhaust pipe 81 and the second upstream exhaust pipe 82 are joined together by welding around the circumference to form an integrated upstream exhaust pipe 80 after the downstream end 81b of the first upstream exhaust pipe 81 is fitted onto the upstream end 82a of the second upstream exhaust pipe 82.

[0046] A flange portion 80d is fixed to an upstream end 81a of the first upstream exhaust pipe 81. The flange portion 80d is attached to the exhaust pipe connecting portion 24c of the internal combustion engine 20. A pair of bolt insertion holes 80e is formed in the flange portion 80d, and as shown in Fig. 5, the flange portion 80d is attached to the exhaust pipe connecting portion 24c of the cylinder head 24 with bolts 69. As shown in Fig. 9, a downstream end 82b of the second upstream exhaust pipe 82 is connected to an upstream end 100a of the catalyst device-accommodated exhaust pipe 100.

[0047] As shown in Figure 10, the second upstream exhaust pipe 82 has a divided body structure that is divided into approximately two parts along the exhaust flow direction, and is made up of a first divided body 83 and a second divided body 84. As shown in Figure 11, when the first divided body 83 and the second divided body 84 are fitted together, the inner circumferential surface 82d of the second upstream exhaust pipe 82 is formed into a substantially circular shape by the inner circumferential surface 83a of the first divided body 83 and the inner circumferential surface 84a of the second divided body 84.

[0048] The divided end edge 83b of the first divided body 83 and the divided end edge 83b of the second divided body 84 respectively form mating portions 83c and 84c, and the mating portion 83c of the first divided body 83 protrudes outward in a step by a dimension equivalent to the plate thickness of the mating portion 84c of the second divided body 84, forming a jockle portion 84d that extends along the divided end edge 84b. The first divided body 83 and the second divided body 84 are joined together by welding at their mating portions 83c, 84c in a so-called jockle joint structure.

[0049] 5, the downstream exhaust pipe 90 is connected to the downstream end 100b of the catalytic converter-accommodated exhaust pipe 100, extends to the right from the catalytic converter-accommodated exhaust pipe 100, and then extends rearward to be connected to the muffler 52 on the right side of the rear wheel 28. The downstream exhaust pipe 90 is disposed so that at least a portion of it is positioned on an extension line of the body frame F.

[0050] 9, the downstream exhaust pipe 90 is made up of a first downstream exhaust pipe 91, the upstream end 91a of which is connected to the downstream end 100b of the catalytic device-accommodating exhaust pipe 100, and a second downstream exhaust pipe 92, the upstream end 92a of which is connected to the downstream end 91b of the first downstream exhaust pipe 91. The downstream exhaust pipe 90 is divided into the first downstream exhaust pipe 91 and the second downstream exhaust pipe 92 at the curved portion.

[0051] The downstream end b of the first downstream-side exhaust pipe 91 has a larger diameter than the upstream end 92a of the second downstream-side exhaust pipe 92. The first downstream-side exhaust pipe 91 and the second downstream-side exhaust pipe 92 are joined by welding around the circumference to form an integrated downstream-side exhaust pipe 90 after the upstream end 92a of the second downstream-side exhaust pipe 92 is fitted onto the downstream end 91b of the first downstream-side exhaust pipe 91.

[0052] As shown in Fig. 10, the first downstream-side exhaust pipe 91 has a divided body structure that is divided into approximately two parts along the exhaust flow direction, and is made up of a first divided body 93 and a second divided body 94. As shown in Fig. 12, when the first divided body 93 and the second divided body 94 are fitted together, an inner circumferential surface 91d of the first downstream-side exhaust pipe 91 is formed into a substantially circular shape by the inner circumferential surface 93a of the first divided body 93 and the inner circumferential surface 94a of the second divided body 94.

[0053] The divided end edge 93b of the first divided body 93 and the divided end edge 93b of the second divided body 94 are folded outward and overlapped, forming a so-called interlocking structure. The divided end edges 93b, 94b of the first divided body 93 and the second divided body 94 are interlocked, and the overlapping ends are joined together by welding.

[0054] In this embodiment, there are two divided body structures, but any number of divided body structures may be provided as long as there are two or more divided body structures in exhaust pipe 51. Furthermore, among the multiple divided body structures, at least one divided body structure may be a divided body structure joined by a joint structure, and the other divided body structures may be divided body structures joined by a jockle joint structure.

[0055] 2, an exhaust gas sensor S1 is provided in the exhaust pipe 90 downstream of the exhaust pipe 51 to detect the oxygen concentration and other parameters in the exhaust gas after it has passed through the catalytic device 53 in order to purify the exhaust gas. The exhaust gas sensor S1 is an LAF sensor or an O2 sensor.

[0056] The exhaust gas sensor S1 is attached so as to be inserted into the exhaust pipe 51 from the upper surface of the second downstream exhaust pipe 92. In a side view of the vehicle, the exhaust gas sensor S1 is provided in the downstream exhaust pipe 90 in a predetermined area located on the lower right side of the internal combustion engine 20, as shown in FIG.

[0057] The exhaust gas sensor S1 and the catalytic converter 53 are disposed in an area surrounded by a first imaginary line L1 and a second imaginary line L2 in Fig. 7. The first imaginary line L1 is an imaginary line that connects a link member connecting portion 13, which is the portion where the link member 11 and the main pipe 4 of the body frame F are joined, to the rotation center CL of the crankshaft 21 of the internal combustion engine 20, in a side view of the vehicle. The second imaginary line L2 is an imaginary line that connects the link member connecting portion 13 and an exhaust pipe connecting portion 24c where the exhaust pipe 51 is connected to the internal combustion engine 20.

[0058] The exhaust gas sensor S1 and the catalytic converter 53 can be arranged compactly by being disposed in the area surrounded by the first imaginary line L1 and the second imaginary line L2 in Fig. 7. Furthermore, by disposing the exhaust gas sensor S1 and the catalytic converter 53 in a position close to the exhaust port 24b of the internal combustion engine 20, the exhaust gas sensor S1 and the catalytic converter 53 can be warmed up quickly.

[0059] Furthermore, as shown in FIG. 2, the exhaust gas sensor S1 is provided on the downstream exhaust pipe 90, further forward of the oil filter 66 in a side view of the vehicle. This allows for easy removal of the oil filter 66 to the side of the vehicle without the exhaust gas sensor S1 becoming an obstacle.

[0060] Furthermore, as shown in FIG. 8, the exhaust gas sensor S1 is disposed in a position where at least a portion thereof overlaps with the body frame F, thereby preventing damage caused by obstacles such as flying stones from the front.

[0061] In the motorcycle 1 of this embodiment, the exhaust gas sensor S1 is attached from above the second downstream exhaust pipe 92, but it may be attached in any position that satisfies the above-mentioned conditions. For example, it may be attached from above the first downstream exhaust pipe 91 as shown in FIG. 13, or it may be attached to the rear of the first downstream exhaust pipe 91 as shown in FIG. 14.

[0062] The motorcycle 1, which is a straddle-type vehicle according to the embodiment of the present invention, is configured as described above, and therefore provides the following effects.

[0063] The motorcycle 1 is equipped with a body frame F, a cylinder block 23 arranged with a cylinder axis C facing forward, a crankcase 22, and a crankshaft 21, and a power unit P swingably supported on the body frame F via a link member 11, and an exhaust system 50 connected to the power unit P and equipped with an exhaust pipe 51 and a catalytic converter 53 arranged midway through the exhaust pipe 51, the exhaust pipe 51 extending downward from the power unit P, and the exhaust pipe 51 includes a catalytic converter-accommodating exhaust pipe 100 that accommodates the catalytic converter 53 therein, and a catalytic converter-accommodating exhaust pipe 110. 00, and a downstream exhaust pipe 90 connected to the downstream side of the catalytic device-accommodating exhaust pipe 100, and an exhaust gas sensor S1 is arranged in the downstream exhaust pipe 90, and the exhaust gas sensor S1 and the catalytic device 53 are located in an area between a first imaginary line L1 connecting the link member connection portion 13 that connects the link member 11 to the body frame F and the center of rotation CL of the crankshaft 21, and a second imaginary line L2 that connects the exhaust pipe connection portion 24c of the power unit P to which the end of the exhaust pipe 51 is connected and the link member connection portion 13.

[0064] Because of this configuration, by providing the exhaust gas sensor S1 in the downstream exhaust pipe 90 downstream of the catalytic device 53, it is possible to measure the exhaust gas after it has passed through the catalytic device 53 and detect the oxygen concentration in the exhaust gas more accurately. In addition, by shortening the distance between the exhaust gas sensor S1 and the internal combustion engine 20, it is possible to warm up the exhaust gas sensor S1 earlier. Furthermore, since the exhaust gas sensor S1 is positioned far from the atmosphere opening port 52a of the exhaust pipe 51, even if the flow of exhaust gas in the exhaust pipe 51 is disturbed by outside air flowing in from the atmosphere opening port 52a when the exhaust pipe 51 becomes negative pressure, this does not affect the detection accuracy of the exhaust gas sensor S1, and the accuracy of the exhaust gas sensor S1 can be improved.

[0065] Furthermore, when viewed from below the vehicle, at least a portion of the downstream exhaust pipe 90 is located on an extension of the body frame F, and when viewed from the front of the vehicle, at least a portion of the exhaust gas sensor S1 overlaps with the body frame F, thereby providing protection from obstacles such as flying stones from the front of the vehicle.

[0066] Furthermore, when viewed from the bottom of the vehicle, the downstream exhaust pipe 90 is located further outward in the vehicle width direction than the crankcase 22, the crankcase 22 has an oil filter 66 that is removed toward the side of the vehicle, and the exhaust gas sensor S1 is positioned on the downstream exhaust pipe 90 further forward of the oil filter 66 when viewed from the side of the vehicle, so that when the oil filter 66 is removed toward the side of the vehicle, the work can be easily performed without the exhaust gas sensor S1 becoming an obstacle.

[0067] Furthermore, the vehicle is equipped with a centrifugal cooling fan 56 that introduces outside air into the power unit P and a fan cover 57 that covers the centrifugal cooling fan 56 from the side of the vehicle, and the downstream exhaust pipe 90 is positioned so that it does not overlap with the grill 57g that serves as an outside air inlet for the fan cover 57 when viewed from the side of the vehicle, making it difficult for warmed air around the downstream exhaust pipe 90 to be drawn into the power unit P, and the cooling efficiency of the power unit P by the centrifugal cooling fan 56 can be improved.

[0068] In addition, a mesh portion 57f is provided on the outer edge 57e of the fan cover 57, and air inside the fan cover 57 is exhausted from the mesh portion 57f by the rotation of the centrifugal cooling fan 56, so that the air can be blown onto the downstream exhaust pipe 90 near the fan cover 57 to cool it, and the rigidity of the metal that makes up the exhaust pipe 51 can be increased.

[0069] Furthermore, at least a portion of the exhaust pipe 51 is made up of the second upstream exhaust pipe 82 and the first downstream exhaust pipe 91 as a divided body structure, which makes it easier to create curved sections with small curvatures, and reduces restrictions on the curvature of the piping.

[0070] Furthermore, the exhaust pipe 51 has at least two divided body structures 82, 91, at least one of which has a divided body structure like the first downstream exhaust pipe 91, in which divided end edges 93b, 94b of each first divided body 93 and second divided body 94 are joined together using a jockle structure to form an integrated unit, and the other has a divided body structure like the second upstream exhaust pipe 82, in which the divided end edge 83b of one of the first divided bodies 83 is formed into a jockle portion 84d that protrudes outward so that the divided end edge 84b of the second divided body 84 can be fitted into it, and the divided end edge 83b and the divided end edge 84b are joined together using a jockle structure to form an integrated unit.

[0071] The joint area between the segments is larger in a segment structure joined by a jockle joint than in a segment structure joined by a clasp joint. Therefore, if all of the segment structures in two or more locations are only segment structures with a jockle joint, the joint between the halves will be stronger than in a segment structure with a clasp joint. However, when the curved portion of the metal exhaust pipe is subjected to heat damage and a force that returns it to a straight shape, stress will concentrate at the joint between the segments. By making some of the segment structures in the exhaust pipe segments joined by a clasp joint, rigidity can be reduced and stress can be dispersed.

[0072] The above describes an intake structure for an internal combustion engine mounted on a vehicle according to one embodiment of the present invention, but the aspects of the present invention are not limited to the above embodiment and include various aspects that can be implemented within the scope of the gist of the present invention. [Explanation of symbols]

[0073] P...power unit, C...cylinder axis, CL...crankshaft rotation center, F...vehicle frame, S1...exhaust gas sensor, 1...Motorcycle, L1...First imaginary line, L2...Second imaginary line, 11...link member, 13...link member connecting portion, 20... internal combustion engine, 21... crankshaft, 22... crankcase, 23... cylinder block, 24... cylinder head, 24c... exhaust pipe connection portion, 50...exhaust system, 51...exhaust pipe, 53...catalytic device, 56...fan, 57...fan cover, 57e...outer edge, 57f...mesh part, 57g...grill, 80... upstream exhaust pipe, 82... second upstream exhaust pipe, 83... division body, 83b... division edge, 84... division body, 84b... division edge, 84d... jockle portion, 90... downstream side exhaust pipe, 91... first downstream side exhaust pipe, 93... division body, 93b... division edge, 94... division body, 94b... division edge, 100...Exhaust pipe housing catalytic converter.

Claims

1. a unit swing engine (P) having a body frame (F), a cylinder section (23) arranged with a cylinder axis (C) facing forward, a crankcase (22), and a crankshaft (21), and supported swingably on the body frame (F) via a link member (11); an exhaust system (50) connected to the unit swing engine (P) and including an exhaust pipe (51) and a catalytic converter (53) disposed midway in the exhaust pipe (51); The exhaust pipe (51) extends downward from the unit swing engine (P), The exhaust pipe (51) comprises a catalytic device-accommodating exhaust pipe (100) that accommodates the catalytic device (53) therein, an upstream exhaust pipe (80) connected to the upstream side of the catalytic device-accommodating exhaust pipe (100), and a downstream exhaust pipe (90) connected to the downstream side of the catalytic device-accommodating exhaust pipe (100), An exhaust gas sensor (S1) is disposed in the downstream exhaust pipe (90), The exhaust gas sensor (S1) and the catalytic converter (53) are arranged as follows in a side view of the vehicle body: a first imaginary line (L1) connecting a link member connecting portion (13) that connects the link member (11) to the body frame (F) and a rotation center (CL) of the crankshaft (21); the exhaust pipe is located in a region between an exhaust pipe connection portion (24c) of the unit swing engine (P) to which an end of the exhaust pipe (51) is connected and a second imaginary line (L2) connecting the link member connection portion (13), At least a portion of the exhaust pipe (51) has a split structure (82, 91), The exhaust pipe (51) has a divided body structure (82, 91) at at least two locations, At least one divided body structure (91) is a divided body structure (91) in which divided end edges (93b, 94b) of each divided body (93, 94) are joined together by a clasp structure to form an integrated body, Another divided body structure (82) is a saddle-type vehicle characterized in that the divided end edge (83b) of one divided body (83) has a jockle portion (84d) protruding outward so as to fit into the divided end edge (84b) of the other divided body (84), and the one divided end edge (83b) and the other divided end edge (84b) are joined together by a jockle fitting structure to form a single body.

2. When viewed from below the vehicle, at least a portion of the downstream exhaust pipe (90) is located on an extension line of the vehicle body frame (F), 2. The straddle-type vehicle according to claim 1, wherein at least a portion of the exhaust gas sensor (S1) overlaps with the body frame (F) in a front view of the vehicle.

3. The downstream exhaust pipe (90) is located outward in the vehicle width direction from the crankcase (22) when viewed from below the vehicle, The crankcase (22) has an oil filter (66) that is taken out toward the side of the vehicle, 3. The straddle-type vehicle according to claim 1, wherein the exhaust gas sensor (S1) is disposed on a downstream exhaust pipe (90) further forward than the oil filter (66) in a side view of the vehicle.

4. a fan (56) that introduces outside air into the unit swing engine (P), and a fan cover (57) that covers the fan (56) from the side of the vehicle; 3. The straddle-type vehicle according to claim 1, wherein the downstream exhaust pipe (90) does not overlap with an outside air inlet (57g) of the fan cover (57) in a side view of the vehicle.

5. 5. The straddle-type vehicle according to claim 4, wherein a mesh portion (57f) is provided on an outer edge (57e) of the fan cover (57).

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