Saddle-type vehicle including an exhaust secondary air valve

Details Saddle-type vehicle including an exhaust secondary air valve Saddle-type vehicle including an exhaust secondary air valve

2000-01-18

2001-06-26

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

C060S293000, C060S307000, C180S068300

Reexamination Certificate

active

06250076

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust secondary air valve, more particularly, an exhaust secondary air valve for a saddle-type vehicle including an engine disposed under a main frame and behind a down frame.
2. Background Art
Japanese Patent Laid-open No. Hei 6-270878 describes an exhaust secondary air system for feeding secondary air to an exhaust passage of an engine mounted on a saddle-type vehicle. Using this arrangement, a motorcycle is capable of oxidizing HC and CO contained in exhaust gas discharged from a combustion chamber of the engine into the exhaust passage.
The exhaust secondary air system described in the above document, which includes an air cleaner used for secondary air and a reed valve, is mounted on a bracket fastened to a mounting plate provided between right and left main frames positioned behind a head pipe of the motorcycle. An air outlet of the reed valve of the exhaust secondary air system is directed rearwardly of the vehicle. Accordingly, a secondary air feed pipe connected from a reed valve to an exhaust port of the engine extends slightly obliquely and upwardly from the air outlet of the reed valve to the rear side of the vehicle, being U-turned, and extends slightly obliquely and downwardly to the front side of the vehicle to be returned again to the vicinity of the reed valve. The secondary air feed pipe is then curved downwardly substantially at right angles, extending to the vicinity of the cylinder head of the engine, and further extends to be communicated to the exhaust port of the engine.
SUMMARY OF THE INVENTION
According to the above-described background art structure, because the exhaust secondary air system is disposed between the right and left main frames of the vehicle at an upper position of the vehicle relatively apart from the engine, the length of the secondary air feed pipe is relatively long. Furthermore, since the secondary air feed pipe is curved, for example, U-turned once over the cylinder head cover as described above, the length of the secondary air feed pipe is unnecessarily extended, with a result that it is difficult to make compact the exhaust secondary air system including the secondary air feed pipe. Additionally, since it is required to ensure a space for containing the longer curved secondary air feed pipe, the layout of the components around the exhaust secondary air system is limited. As a result, it becomes difficult to realize a compact layout of the components around the exhaust secondary air system.
Since the exhaust secondary air system is mounted to the vehicular frame via the bracket and the mounting plate, it is required to additionally prepare the mounting plate for mounting the exhaust secondary air system to the vehicle.
In view of the disadvantages of conventional exhaust secondary valves, an object of the present invention is to provide an exhaust secondary air system configured such that an exhaust secondary air valve is mounted on a vehicular frame for supporting an engine in a manner which implements relatively short secondary air feed pipes, thus resulting in a compact exhaust secondary air system. Another object of the present invention is to provide an exhaust secondary air valve and secondary air feed pipes which are air-cooled.
To achieve the above objects, there is provided a saddle-type vehicle including a main frame extending rearwardly from a head pipe; a down frame extending downwardly from the head pipe; an engine disposed under the main frame and behind the down frame; and an exhaust secondary air valve, connected to a secondary air feed pipe, for feeding secondary air to an exhaust passage of the engine via the secondary air feed pipe, wherein the exhaust secondary air valve is mounted on the down frame.
With this configuration, the down frame of the saddle-type vehicle for supporting the engine is located near the engine, while extending downwardly toward the engine positioned under the main frame, and the exhaust secondary air valve mounted on the down frame is also located near the engine. As a result, the length of the secondary air feed pipes extending from the exhaust secondary air valve to the exhaust passage of the engine can be shortened and thereby the exhaust secondary air system can be made compact.
Since the down frame of the saddle-type vehicle is exposed to airflow, the exhaust secondary air valve mounted on the down frame and the secondary air feed pipes connected thereto are sufficiently cooled. As a result, the exhaust secondary air valve and the secondary air feed pipes are prevented from being overheating due to heat released from the engine. Therefore, improved durability of the exhaust secondary air valve is achieved. Furthermore, since air flowing in the secondary air feed pipes does not reach excessively high temperature, it is possible to lower the reduction in density of the air and hence to suppress the reduction in purifying ratio of the exhaust gas.
Moreover, since the exhaust secondary air valve is mounted on the down frame constituting part of the existing frame structure of the vehicle, and additional mounting plate is not required to employ the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


REFERENCES:
patent: 4387565 (1983-06-01), Otani et al.
patent: 4417442 (1983-11-01), Ikenoya et al.
patent: 4434615 (1984-03-01), Ikenoya et al.
patent: 4508189 (1985-04-01), Kato
patent: 5657628 (1997-08-01), Takeuchi
patent: 59-68514 (1984-04-01), None
patent: 59-90715 (1984-05-01), None
patent: 59-99023 (1984-06-01), None
patent: 59-99020 (1984-06-01), None
patent: 60-79115 (1985-05-01), None
patent: 62-270878 (1994-09-01), None

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