Internal-combustion engines – Poppet valve operating mechanism – Tappet
Patent
1997-06-09
1999-09-21
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Tappet
123 9049, 123 9051, F01L 124, F01L 114
Patent
active
059540206
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a cup-shaped valve tappet for actuating a gas exchange valve of an internal combustion engine, comprising a cylindrical jacket closed at one end by a bottom and guided in a bore of a cylinder head, the valve tappet being actuated by a cam of a camshaft acting on the bottom of the tappet.
A cup-shaped valve tappet is for actuating a gas exchange valve (17) of an internal combustion engine, comprising a cylindrical jacket (6) closed at one end by a bottom (7) and guided in a bore (2) of a cylinder head (3), the valve tappet (1) being actuated by a cam (4) of a camshaft (5) acting on the bottom (7) of the tappet (1) is known from EP-A-00 30 781. This valve tappet comprises a hydraulic valve clearance compensation element lodged in a guide sleeve which is concentric with the jacket and extends from a web starting from the inner wall of the jacket. The bottom, the jacket and the web are all configured with relatively thick walls so that the valve tappet has a high overall weight. It is known that valve drives involving large masses require high spring forces for controlling their dynamics. However, these high spring forces lead to an increase of friction in the valve drive which results in higher fuel consumption. A further disadvantage of higher valve spring forces is the intensification of noises in the valve drive.
Efforts have therefore already been made in the past to reduce the weight of valve tappets by making them of a light-weight material such as aluminum, for example. However, such aluminum tappets require special measures for the configuration of the bottom because this is contacted by the cam of the camshaft usually made of steel. For this reason, the bottom was either provided with a wear-resistant layer, or it was made as a separate part of steel and fixed in the aluminum tappet. Such a configuration of a valve tappet is relatively expensive and not suitable for production in series.
The object of the invention is a considerable reduction of the weight of a valve tappet of the generic type by using simple means, so that friction in the valve drive and thus also fuel consumption of the internal combustion engine can be considerably reduced. At the same time, the valve drive must have an adequate rigidity for absorbing the valve actuating forces.
The invention achieves this object by the fact that the bottom and the jacket are steel components having wall thicknesses A, B dimensioned so that a product P.sub.1 of the wall thicknesses, A.times.B, expressed in millimeters is .ltoreq.2.3, the wall thickness A of the bottom being 1.7 to 2.5 mm and the wall thickness B of the jacket being 0.7 to 1.0 mm. Hitherto, there existed reservations in the technical field regarding a further reduction of the wall thicknesses of valve tappets because it was feared that their rigidity would no longer be adequate. Calculations with the finite element method and test series have very clearly shown that the cup-shaped tappet of the invention, made preferably as a deep drawn part, has an adequate rigidity while the weight of the tappet is drastically reduced. Thus, the stated wall thickness ranges lie considerably below the wall thicknesses implemented in the past.
The cup-shaped tappet comprises a web starting from the jacket and merging into a guide sleeve which is concentric with the jacket and in which a hydraulic clearance compensation element is guided. The wall thickness C of the web made of a steel material is dimensioned so that a product P.sub.2 of the wall thicknesses of the bottom, jacket and web, A.times.B.times.C, expressed in millimeters is .ltoreq.1.9, the wall thickness C of the web being 0.6 to 0.8 mm. Insofar as its rigidity proves to be inadequate, a thin-walled web of this type can be additionally supported, if necessary, by a sleeve extending up to the bottom and provided for enabling a suction of the oil supplied to the valve clearance compensation element at a lower level of the tappet (cf. DE-A-35 42 192). The use of such a thin-walled web likewise has a positive effect on
REFERENCES:
patent: 4465038 (1984-08-01), Speil
patent: 4602409 (1986-07-01), Schnaeffler
patent: 4702406 (1987-10-01), Sullivan et al.
Ammon Reinhard
Grell Karl Ludwig
Miereisz Wolfgang
Schmidt Dieter
Speil Walter
Castro Arnold
INA Walzlager Schaeffler KG
Lo Weilun
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