Saddle riding vehicle

1. A saddle riding vehicle comprising:

a body frame;

a unit swing engine having a cylinder section disposed substantially horizontally and a crankcase, the unit swing engine being swingably supported on the body frame through a link member; and

an exhaust device connected to the unit swing engine and including an exhaust pipe and a catalyst device disposed at an intermediate portion of the exhaust pipe,

wherein the exhaust pipe extends downward from the unit swing engine,

the exhaust pipe includes a catalyst device accommodating exhaust pipe accommodating the catalyst device therein, an upstream-side exhaust pipe disposed on an upstream side of the catalyst device accommodating exhaust pipe, and a downstream-side exhaust pipe disposed on a downstream side of the catalyst device accommodating exhaust pipe,

the catalyst device is larger in diameter than a diameter of the upstream-side exhaust pipe and than a diameter of the downstream-side exhaust pipe,

the link member is disposed on an upper side of the crankcase,

in side view, at least part of the catalyst device is disposed below the cylinder section and is located in a region between

an imaginary line connecting a link member coupling section for coupling the link member to the body frame and a front end of the crankcase and

an imaginary line connecting an exhaust pipe connection section of the unit swing engine connected with an end of the exhaust pipe and the link member coupling section, and

an exhaust device coupling section for coupling the crankcase and the exhaust device is provided.

2. The saddle riding vehicle as claimed in claim 1 ,

wherein the catalyst device is disposed in such a direction that a longitudinal direction of the catalyst device is oriented in a transverse direction, and

the exhaust device coupling section and the exhaust pipe connection section connecting the exhaust pipe and the cylinder section are disposed in a manner of being allocated to left and right sides, with respect to a longitudinal directional center line of the catalyst device as viewed from a bottom.

3. The saddle riding vehicle as claimed in claim 2 ,

wherein the exhaust device coupling section has a crankcase-side stay and an exhaust-device-side stay coupled to the crankcase-side stay,

the crankcase-side stay and the exhaust-device-side stay are disposed with an offset in the transverse direction, and

the crankcase-side stay and the exhaust-device-side stay are coupled with each other while being overlapped with each other in the transverse direction.

4. The saddle riding vehicle as claimed in claim 1 ,

wherein the exhaust device coupling section has a crankcase-side stay and an exhaust-device-side stay coupled to the crankcase-side stay,

the crankcase-side stay and the exhaust-device-side stay are disposed with an offset in the transverse direction, and

the crankcase-side stay and the exhaust-device-side stay are coupled with each other while being overlapped with each other in the transverse direction.

5. The saddle riding vehicle as claimed in claim 4 ,

wherein the crankcase is split at a crankcase split surface into left and right portions,

the exhaust pipe of the exhaust device has a vertical section extending downward from the exhaust pipe connection section of the cylinder section, a side extension section being continuous to a downstream side of the vertical section and extending toward one side with respect to an imaginary line passing through the crankcase split surface of the crankcase as viewed from a bottom, and a curved section being continuous with the side extension section and turning back in a U shape, and

the crankcase-side stay is provided on the other side with respect to the imaginary line passing through the crankcase split surface as viewed from a bottom.

6. The saddle riding vehicle as claimed in claim 4 , wherein the exhaust-device-side stay of the exhaust device coupling section is provided on a catalyst device accommodating exhaust pipe accommodating the catalyst device.

7. The saddle riding vehicle as claimed in claim 6 ,

wherein the crankcase is split at a crankcase split surface into left and right portions,

the exhaust pipe of the exhaust device has a vertical section extending downward from the exhaust pipe connection section of the cylinder section, a side extension section being continuous to a downstream side of the vertical section and extending toward one side with respect to an imaginary line passing through the crankcase split surface of the crankcase as viewed from a bottom, and a curved section being continuous with the side extension section and turning back in a U shape, and

the crankcase-side stay is provided on the other side with respect to the imaginary line passing through the crankcase split surface as viewed from a bottom.

8. The saddle riding vehicle as claimed in claim 1 , wherein

the exhaust pipe guides an exhaust gas of the unit swing engine; and

the catalyst device accommodating exhaust pipe has a catalyst case section accommodating the catalyst device,

the catalyst device accommodating exhaust pipe has a structure having a first half and a second half split along an exhaust gas flow direction wherein joint edge sections of the first half and the second half are mated and united with each other,

the catalyst case section of the catalyst device accommodating exhaust pipe includes reduced diameter sections holding the catalyst device, and

the joint edge sections in the same section as the reduced diameter sections in a case of cutting perpendicularly to a splitting direction of the catalyst device accommodating exhaust pipe are made to be enlarged diameter sections larger than an outside diameter of the catalyst device.

9. The saddle riding vehicle as claimed in claim 8 , wherein the reduced diameter sections are provided on an upstream side in regard to an exhaust gas flow direction of the catalyst device and hold the catalyst device.

10. The saddle riding vehicle as claimed in claim 8 ,

wherein the catalyst device includes a tubular outer shell section serving as an outer shell, and a catalyst accommodated in the outer shell section, and

the enlarged diameter sections are provided with a gap between the enlarged diameter sections and the outer shell section, and the reduced diameter sections are put in contact with the outer shell section.

11. The saddle riding vehicle as claimed in claim 10 ,

wherein the catalyst case section includes case sections larger in diameter than the outer shell section, and

the case sections are provided with a gap between the case sections and the outer shell section.

12. The saddle riding vehicle as claimed in claim 8 , wherein the catalyst device accommodating exhaust pipe has the structure wherein the first half and the second half are united with each other by welding the joint edge sections of the first half and the second half.

13. The saddle riding vehicle as claimed in claim 12 ,

wherein the catalyst device includes a tubular outer shell section serving as an outer shell, and a catalyst accommodated in the outer shell section, and

the enlarged diameter sections are provided with a gap between the enlarged diameter sections and the outer shell section, and the reduced diameter sections are put in contact with the outer shell section.

14. The saddle riding vehicle as claimed in claim 12 , wherein the reduced diameter sections are provided on an upstream side in regard to an exhaust gas flow direction of the catalyst device and hold the catalyst device.

15. The saddle riding vehicle as claimed in claim 1 , wherein

the exhaust pipe has a curved section;

the catalyst device includes a catalyst disposed in the exhaust pipe on a downstream side of the curved section of the exhaust pipe,

a center axis of the catalyst is offset toward a curving directionally outer side with respect to a center axis of the curved section of the exhaust pipe, and

a diffusion member is disposed on a curving directionally outer side with respect to the center axis of the exhaust pipe and on an upstream side of the catalyst.

16. The saddle riding vehicle as claimed in claim 15 , wherein the diffusion member has a straightening vane inclining at an acute angle in relation to the center axis of a downstream end of the curved section of the exhaust pipe, faces a flow of an exhaust gas, and is oriented toward a curving directionally inner side with respect to the center axis of the exhaust pipe.

17. The saddle riding vehicle as claimed in claim 16 , wherein the straightening vane has a communication opening through which an upstream side and a downstream side of an exhaust gas flow communicate with each other.

18. The saddle riding vehicle as claimed in claim 17 , wherein the catalyst device accommodating exhaust pipe with the catalyst accommodated therein is connected to a downstream side of the curved section, the catalyst device accommodating exhaust pipe has a connection section enlarged in diameter along an exhaust gas flow direction on an upstream side of the catalyst, and the diffusion member is disposed inside the connection section.

19. The saddle riding vehicle as claimed in claim 16 ,

wherein the catalyst device accommodating exhaust pipe with the catalyst accommodated therein is connected to a downstream side of the curved section,

the catalyst device accommodating exhaust pipe has a connection section enlarged in diameter along an exhaust gas flow direction on an upstream side of the catalyst, and

the diffusion member is disposed inside the connection section.

20. The saddle riding vehicle having as claimed in claim 19 , wherein the diffusion member has an outer peripheral edge section formed to be along an inner peripheral surface of the connection section of the catalyst device accommodating exhaust pipe by turning back an upstream-side peripheral edge of the straightening vane in an outer peripheral side downstream direction, and the outer peripheral edge section is attached to the connection section.