Internal-combustion engines – Poppet valve operating mechanism – Plural valve trains – single actuator
Patent
1997-11-25
1998-11-03
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Plural valve trains, single actuator
123 9027, F01L 126
Patent
active
058294007
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a valve drive of an internal combustion engine comprising at least two equally acting gas exchange valves loaded in lifting direction by at least one cam of a camshaft, said gas exchange valves extending at a small, defined angle to each other.
BACKGROUND OF THE INVENTION
Multi-valve drives of the aforesaid type are being increasingly used in engine construction. The technical journal MTZ--Motortechnische Zeitschrift--No. 2, 1995, for instance, describes a four-cylinder engine with a five-valve technique i.e., with three intake and two exhaust valves per cylinder. Therefore, five cup-shaped tappets are required for each cylinder as transmitting elements. The intake valves are arranged on two different planes (two valves being arranged on a common plane), because the outer surface of the combustion chamber is domed and the available valve cross-section is limited. The loading of the intake valves disposed at a slant to one another necessitates a cam produced by complicated grinding for each intake valve.
OBJECT OF THE INVENTION
It is therefore an object of the invention to create a valve drive of the pre-cited type in which the aforesaid drawbacks are substantially eliminated and particularly to provide a simultaneous loading of at least two equally acting gas exchange valves using fewer parts and less complicated manufacturing procedures.
SUMMARY OF THE INVENTION
The valve drive (1) of the invention of an internal combustion engine comprising at least two equally acting gas exchange valves (2) loaded in lifting direction by at least one cam of a camshaft (3), said gas exchange valves (2) extending at a small, defined angle to each other, is in that a cam follower is arranged in driving relationship between the cam(s) and the gas exchange valves, the cam follower comprising a bridge which is guided for linear displacement relative to a cylinder head of the external combustion engine by guide means, and a longitudinal axis extending through the guide means of the bridge is at least approximately parallel to a bisector of the angle, or the longitudinal axis extending through the guide means is approximately parallel to a longitudinal axis situated between the longitudinal axes of the gas exchange valves, along which longitudinal axis, a sum of the reaction forces acting from the bridge on the guide means is zero or minimal.
The bridge described herein which, for example, can have a girder-like configuration, enables an equally acting loading of at least two gas exchange valves. Longitudinal axes of the gas exchange valves can extend, for example, so that their point of intersection is situated on the side of camshaft-proximate ends of the gas exchange valves (see description of figures). Thus only at least one cam is required for each cylinder and number of equally acting valves. Another minimal requirement consists in that only one transmitting element is required in the bridge for transmission to the gas exchange valve. At the same time, the otherwise complicated manufacturing of cams for each gas exchange valve is simplified.
An essential basic idea of the invention is to arrange the bridge so that the ends of the valve stems can only migrate to a small extent on the transmitting elements on the under surface of the bridge. This is achieved by the previously described arrangement of the guide means of the bridge parallel to a bisector between the planes of the gas exchange valves. Since, however, as is the case in the example of valve configuration, two same function gas exchange valves are situated on one common plane, a much larger reaction force is transmitted to the guide means by these two same function gas exchange valves than by the third gas exchange valve. According to the invention therefore, the guide means of the bridge is not necessarily arranged parallel to the bisector but parallel to a longitudinal axis along which the sum of the reaction forces acting from the bridge on the guide means is minimal.
However, the configuration and arrang
REFERENCES:
patent: 4660529 (1987-04-01), Yoshikawa
patent: 4809663 (1989-03-01), De Tomaso
patent: 5228419 (1993-07-01), Nonogawa
patent: 5303680 (1994-04-01), Nielson
patent: 5445117 (1995-08-01), Mendler
Von Wilhelm und Franz Lukas Article (pgs. 680-688) 1994.
Haas Michael
Speil Walter
Ina Walzlager KG
Lo Weilun
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