Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
2000-06-19
2001-08-28
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090420, C074S559000
Reexamination Certificate
active
06279525
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a finger lever for a valve train of an internal combustion engine, said finger lever being made by shaping without chip removal and comprising two side walls which are connected to each other in a first end region by a first bottom wall to form an upwardly open U-shape, the first bottom wall comprising a downwardly facing semi-spherical recess for receiving a support element, said side walls being connected to each other in a second end region by a second bottom wall to form an upwardly open U-shape, said second bottom wall comprising a contact surface for a valve stem of a gas exchange valve, and the contact surface comprising lateral guides spaced apart from each other.
BACKGROUND OF THE INVENTION
A generic finger lever of the pre-cited type having lateral guides is known from U.S. Pat. No. 5,016,582. These guides bear against the valve stem of a gas exchange valve and have the function of guiding the finger lever laterally, i.e. they prevent the finger lever from slipping off the valve stem. These lateral guides are formed by a doubling of the side walls, i.e. the side walls merge at their lower ends into parallel, upwardly extending inner side walls that are connected to each other by a bottom wall. In this way, a downwardly facing recess is formed in the finger lever for the valve stem, said recess being defined by the two inner side walls and the bottom wall.
A drawback of this finger lever is that this type of lateral guidance necessitates a complicated shaping procedure and the finger lever has a large mass due to the doubling of the side walls.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an improved finger lever whose lateral guides are substantially simpler to manufacture.
The invention achieves this object in that, in the region of the contact surface of the valve stem and/or in the region of the semi-spherical recess, the side walls comprise partially punched-out sections that are bent through nearly 180° toward the valve stem and/or toward the support element respectively, so that retaining tabs are formed for the lateral guidance of the finger lever on the valve stem and/or the support element.
The advantage of this solution is, on the one hand, that the retaining tabs serving as lateral guides can be made with a negligible amount of additional work compared to the prior art by a simple punching and bending operation as a part of the general manufacturing process. On the other hand, the mass of the lever can be reduced because the retaining tabs originally form a part of the side walls and do not have to be formed out of additional material. Still another advantage is that the retaining tabs can be arranged both in the end region of the valve stem and in the end region of the support element. While the arrangement in the end region of the valve stem is intended mainly for the lateral guidance of the finger lever on the valve stem, retaining tabs in the end region comprising the semi-spherical recess are to be understood as lateral safety devices for mounting that prevent a lateral tilting of the lever when it is brought into place before the mounting of the camshaft. Such a tilting would otherwise be possible due to the fact that the center of gravity of the lever as a whole is situated distinctly higher than the points of support.
The upper boundary of the punched-out section is situated below the upper edge of the side walls This means that the side walls from which the retaining tabs are punched out are not completely severed. This assures that a residual cross-section remains in the upper part of the side walls so that an adequate rigidity is maintained in the region of the pressure zone of the finger lever.
The shape of the upper edge of the side walls in the region of the punched-out section is matched to the profile of the punched-out section. This means that the side walls follow the profile of the punched-out section so that, for example, if the punched-out section has an arcuate configuration, the side walls will also have an arcuate shape. This enlarges the residual cross-section of the side walls and thus enhances the stability of the lever.
According to a further feature of the invention, the residual cross-section of the side wall formed by the partially punched-out section is displaced into the pocket by the bent-over retaining tab. Thus, by a simple shaping operation, for example pressing, this residual cross-section is displaced toward the valve stem or toward the support element respectively, so that, on the one hand, the large cross-section which favors stiffness is approximately maintained and, on the other hand, possible problems in free movement due to the enveloping circle of the cam, especially in the case of miniaturized levers, are avoided.
According to a further additional feature of the invention, the retaining tabs may have a rectangular, a trapezoid or a semicircular configuration. These are all equally efficient forms and the choice depends only on tool availability and suitability for the particular case of use. One factor to be kept in mind when choosing the shape of the retaining tab is that the most favorable possible distribution of stress in the residual cross-section should be achieved.
The retaining tabs may be subjected to an after-treatment of stamping. By this is meant that a modification of the cross-section is effected by a subsequent shaping process, so that the surface area of the retaining tab is enlarged, for example, by ironing.
It can be advantageous if the retaining tabs are parallel to or are bent to extend at a defined angle to the side walls. If the retaining tabs are parallel to the side walls, they are advantageously arranged inwardly offset from the side walls.
Finally, the upper edges of the side walls in the region in front of and behind the retaining tabs is bend inward at a right angle. This inward bending makes up for the loss of stiffness caused by the punching out of the retaining tabs.
The invention will now be described more closely with the help of the following example of embodiment.
REFERENCES:
patent: 2943612 (1960-07-01), Middler
patent: 5016582 (1991-05-01), Mills
patent: 5775280 (1998-07-01), Schmidt et al.
patent: 19617668 (1997-11-01), None
patent: 19630775 (1998-02-01), None
patent: 586819 (1993-04-01), None
Bierman, Muserlian and Lucas
Ina Walzlager Schaeffler OHG
Lo Weilun
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