Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
2000-06-01
2001-08-14
Lo, Wellun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090420, C074S559000, C029S888200
Reexamination Certificate
active
06273044
ABSTRACT:
The present invention pertains to a valve actuating lever for transmitting movement of a cam arranged on a camshaft to a gas changing valve of an internal combustion engine.
The task of the invention and its solution will be described in the following using the example of a drag lever. It is to be pointed out that this description is not to be understood as a restriction of the present invention in any way, in fact it is quite possible to realize the present invention with differently configured valve actuating levers as, for example, with rocker arms or with non-roller-actuated valve actuating levers.
A drag lever of this type is known from DE 195 43 657 A1.
Known valve actuating levers have a U-shaped base body having a socket-like recess disposed at one end thereof for supporting the lever in mounted state by means of a supporting element on the cylinder head. A valve contact area is provided at the other end for actuating the gas shuttle valve of the internal combustion engine depending upon the position of the cam on the camshaft.
The cam contacts said valve actuating lever in a cam contact area, whereby with a drag lever, a roller rotatably mounted by means of roller elements is arranged in said cam contact area.
Although this known valve actuating lever fulfills its function to a very satisfactory degree, there is nevertheless still a need to further increase its technical functionality by reducing the weight and thus decreasing the moment of inertia of the lever about its axis of rotation without diminishing stability. In addition, there is a desire to further lower manufacturing costs.
It is therefore the task of the present invention to provide a valve actuating lever and especially a drag lever as well as a method for its manufacture, in which the lever's moment of inertia about the axis of rotation is decreased. A further aspect of this task is to design the inventive valve actuating lever in such a manner that stability is increased relative the state of the art and allows manufacturing at reasonable costs.
This task is solved in accordance with the present invention.
The valve actuating lever in accordance with the present invention has an oblong base body of essentially non-cutting structure, preferably having a U-shaped profile. Said base body is arranged in a longitudinal symmetry plane extending essentially symmetrically longitudinal therefrom. Tabs are arranged at both sides of said longitudinal symmetry plane in the valve contact area, each tab respectively having a lateral surface facing said longitudinal symmetry plane. The tabs are formed onto an end edge of said base body and bent over into the valve contact area.
At least one of said tabs has a connecting portion extending out from said longitudinal symmetry plane in which the clearance spacing between said lateral surfaces increases as well as at least one parallel portion in which said lateral surfaces run essentially parallel to said longitudinal symmetry plane.
The two tabs are arranged spaced at a clearance at the end edge of the base body, said clearance being smaller than the clearance of the lateral surfaces in the parallel portion, whereby said clearance is respectively defined perpendicular to said longitudinal symmetry plane.
The inventive design has numerous substantial advantages.
The clearance spacing of the tabs at the end edge of the elongated base body is a design dimension which defines the width of the elongated base body in the valve contact area. As this spacing is decreased, the width of the elongated base body is simultaneously decreased at least in the valve contact area and thus also its weight. Since the valve contact area is radially distanced from the axis of rotation of the valve actuating lever, a fundamental decrease of the moment of inertia about the axis of rotation of the lever results. This results in a reduction of the force required for actuating the lever at the same number of revolutions and increases the upper allowable rotational limit for the valve operating mechanism with respect to the actuating force.
Since it is possible, with otherwise the same dimensions, to reduce the width of the lever, the lever's bent length is thus also reduced transverse to its longitudinal direction, which allows for an increasing of its stability.
Furthermore, reducing the lever width decreases the material expenditure, which in turn lowers manufacturing costs. In contrast to other manufacturing procedures, the non-cut structure, in which also the tabs are manufactured by a simple stamping and bending process, has in itself considerable cost advantages.
The reduction in lever width has the further advantage that the valve operating mechanism as a whole can be fabricated narrower. Since, due to demands of space economics and weight optimization, engine designers are compelled to develop engines having an overall shortest structural length as possible, the width reduction is of particular significance when, but not only expressly limited thereto, three or more valves per cylinder are to be employed due to performance, consumption and exhaust value mandates.
In a first preferred embodiment, the tabs are formed on the base body before the bending process in such a manner that they extend parallel to the longitudinal symmetry plane, meaning they extend linearly. Bending then transpires in such a manner that one or both tabs are bent away from the longitudinal symmetry plane to form the connecting portion. At the end of said connecting portion, the tabs are then bent in such a manner that the inner lateral surface of said tabs facing the symmetry plane run parallel thereto.
According to structural requirements, a further narrowed portion can be adjoined to these parallel sections in which one or both tabs are again facing the longitudinal symmetry plane.
In a second preferred embodiment of the present invention, the tabs are stamped such that the connecting portion and the parallel portion are already provided in the undeformed tabs. The tabs then only have to be bent 180° and already have the desired contour in the valve contact area in their unbent state without the realization of any further bending process.
The first and second embodiment may also be combined with one another. In this case, the tabs are brought into their initial form by means of a stamping process, then are subsequently bent 180° and then brought into their final form by an additional bending toward or away from the longitudinal symmetry plane.
It is furthermore possible to treat the tabs differently so that, for example, only one tab is subjected to a bending of about 180°, while the other tab undergoes both this bending as well as also a further bending in particular toward or away from said longitudinal symmetry plane. Here the initial form of the tabs can be identical; e.g. the form of an elongated rectangular block having longitudinal edges running parallel to the longitudinal symmetry plane or which differ from one another.
REFERENCES:
patent: 5016582 (1991-05-01), Mills
patent: 5655490 (1997-08-01), Nagano et al.
patent: 5775280 (1998-07-01), Schmidt et al.
patent: 195 43 657 (1997-05-01), None
patent: 196 17 668 (1997-11-01), None
Engelhardt Helmut
Mayer Wolfgang
Meyer Johannes
Bayerische Motoren Werke AG
Lo Wellun
Pearne & Gordon LLP
LandOfFree
Valve actuating lever does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Valve actuating lever, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Valve actuating lever will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2517717