Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
2000-03-29
2001-06-26
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090270
Reexamination Certificate
active
06250269
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an arrangement for supporting a rocker shaft in an engine.
2. Description of the Related Art
Four-stroke engines are provided with a valve-moving device within the cylinder head. The main component members in such valve-moving devices are a cam shaft, which rotates in motion with a crank shaft, an intake valve and an exhaust valve, valve-moving intake and exhaust cams provided on the cam shaft, intake and exhaust rocker arms, which transmit the rotational motion of the intake and exhaust cams to the two valves, a rocker shaft supporting the rocker arms with freedom of rotation, and the like.
A known method of supporting the rocker shaft within the cylinder head is, by way of example, to provide bearing bosses, which support the cam shaft with adequate excess materials, to run to an insertion hole, which is parallel with the cam shaft through the excess material, and to pass through a rocker shaft through this run-through hole.
In addition, normally a single rocker shaft is used for both the intake and the exhaust rocker arms.
Rocker shafts require an extremely high degree of precision in cases where a run-through hole for the rocker shaft is machined into the excess material of a bearing boss since any discrepancy in positioning has a major effect on the performance of the valve-moving device, not least in that it produces variations in the valve timing.
However, high-precision machining is undesirable since it requires special equipment and the machining itself entails costs.
Further, providing a bearing boss with excess material for supporting a rocker shaft also produces problems in that it causes increased weight, and pores are liable to occur during casting if a large amount of excess material is formed.
Meanwhile, if a single rocker shaft is used for both the intake and the exhaust rocker arms, there are limits on factors such as the position in which the valves are installed, and the degree of freedom in the layout of the valve-moving device is reduced.
SUMMARY OF THE INVENTION
The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the advantages and purposes of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
The present invention has taken the above situation into account and aims to provide an arrangement for supporting a rocker shaft in an engine allowing installation of the rocker shaft without incurring high costs, while employing a simple arrangement.
Another exemplary aim of the present invention is to provide an arrangement for supporting a rocker shaft in an engine whereby the degree of the freedom in the layout of the valve-moving device is increased.
Yet another exemplary aim of the present invention is to provide an arrangement for supporting a rocker shaft in an engine whereby rocker shaft positioning is facilitated.
In order to overcome the exemplary problems discussed above as well as to provide additional advantages, the arrangement for supporting a rocker shaft in an engine according to the present invention involves an engine equipped with valve-moving devices such as a cam shaft inside a cylinder head, intake and exhaust valves, intake and exhaust cams, intake and exhaust rocker arms, rocker shafts, which support these rocker arms with freedom of rotation, and the like, wherein bearing bosses for supporting the cam shaft are formed inside the cylinder head, flat seats are formed on the bearing bosses, and flat seats are formed on the rocker shafts, and the rocker shafts are fitted on the bearing bosses with the flat seats matched against each other.
Further, in order to overcome the exemplary problems discussed above, the rocker shafts are fixed on the bearing bosses via a bracket, and a thrust-receiving part is integrally formed on the bracket, and a spacer spring is installed between this thrust-receiving part and the supported parts of the rocker arms such that the rocker arms are held on the rocker shafts.
Also, in order to further overcome the problems discussed above and provide further advantages, the rocker shafts are provided, respectively one apiece, in the intake rocker arm and exhaust rocker arm.
Furthermore, in order to overcome the problems discussed above and provide still other advantages, the abovementioned bracket is integrated in such a way that it extends across both the intake rocker shaft and the exhaust rocker shaft.
In addition, in order to overcome the problems discussed above and provide additional advantages, knock pins are installed between the rocker shafts and the bearing bosses when fitting the rocker shafts.
REFERENCES:
patent: 4086887 (1978-05-01), Schoonover et al.
patent: 4402284 (1983-09-01), Honma
patent: 4537166 (1985-08-01), Kimura et al.
patent: 5339778 (1994-08-01), Reckzugel et al.
patent: 5363818 (1994-11-01), Iwata et al.
patent: 5605077 (1997-02-01), Tsunoda et al.
patent: 8-100700 (1996-04-01), None
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Lo Weilun
Suzuki Motor Corporation
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