Internal-combustion engines – Poppet valve operating mechanism – Valve driven closed
Patent
1998-05-18
1999-08-03
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Valve driven closed
123 9026, F01L 130
Patent
active
059311304
DESCRIPTION:
BRIEF SUMMARY
This patent application concerns a desmodromic distribution system for four-stroke engines consisting of an articulated joint between tappet and valve.
It is common knowledge that in desmodromic distribution systems, the opening and closing of the valve is performed by means of two camshafts, whose cams act on the same tappet, connected solidly to the stem of the respective valve, and whose alternating strokes consequently follow those of the tappet.
The solid connection between the tappet and valve causes problems when the engine runs at high speed due to the minor distortions that may occur--as a result of the thermal expansion of the transmission components between the sliding axle of the tappet and that of the respective valve.
More specifically, even minor distortions cause serious stress on the valve, on which the tappet discharges a force having a non null transverse component with respect to the sliding axle of the valve.
The scope of this invention is to prevent these problems by introducing an articulated joint between the tappet and the respective valve, able to support minor distortions between the tappet and the valve so that the force transmitted by the tappet to the valve is always perfectly directed along the sliding axle of the valve itself.
This articulated joint consists of a special joint, having a hollow cylinder whose surface is at one end characterised by a longitudinal through slot, and on the opposing end, by a mushroom-shaped element with ball head projecting externally. A cylindrical groove which can house and slide inside the cylinder being provided on the tappet; the longitudinal axle of said cylindrical groove being perpendicular to the sliding axle of the tappet.
The spherical head of said mushroom-shaped element, on the other hand, houses exactly inside a conforming housing within a pair of cotters designed to connect to the top of the valve stem.
The coupling between the cylindrical groove of the tappet and the cylindrical housing of said special joint allows the tappet to translate in a direction orthogonal to the sliding axis of the valve.
The ball coupling between the pair of cotters and the mushroom-shaped element of the special joint in question allows angular deviations of the sliding axis of the tappet with respect to the sliding axis of the valve.
For major clarity the description continues with reference to the enclosed drawings which are intended for purposes of illustration and not in a limiting sense where:
FIG. 1 is a schematic view of the transverse section of the head of a four-stroke engine using the desmodromic distribution system according to the invention;
FIGS. 2, 4 and 5 are three orthogonal projections showing the mechanical components utilised by the desmodromic distribution system according to the invention;
FIG. 3 is a cross-section of FIG. 5 with plane III--III;
FIG. 6 is an axonometric exploded view of the mechanical components utilized by the desmodromic distribution system according to the invention .
The parts numbered and represented in FIG. 1 are as follows for the lower shaft (11); (15); the valve stem; valve-guide (21);
FIG. 2 is a top view of the distribution system shown in FIG. 4; FIG. 2 shows the following:
FIG. 3 shows the lower camshaft (11).
FIG. 6 shows the following: which allows the above cylindrical groove (14) to fit into the cylindrical duct of the joint (15); with the joint (15), in opposing position with respect to the longitudinal through slot; cavities (23) designed to form together a spherical seat in which the ball head of the mushroom-shaped element (16) can house as well as a pair of semicircular cavities (22) designed to fasten the stem of the valve (19) whose end has an annular connection groove for this purpose; to house and fasten the pair of cotters (17); the pair of cotters (17).
It is now much clearer from the description referring to the above figures how the articulated joint between tappet and valve is achieved in the desmodromic distribution system according to the invention.
The coupling between the cylindri
REFERENCES:
patent: 2831470 (1958-04-01), Lorscheidt
patent: 4887565 (1989-12-01), Bothwell
patent: 4928650 (1990-05-01), Matayoshi et al.
patent: 5048474 (1991-09-01), Mayayoshi et al.
Bloom Leonard
Lo Weilun
LandOfFree
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