Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-03-24
2001-04-24
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090410, C123S19800E
Reexamination Certificate
active
06220213
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a rocker arm installed in a cylinder head of a valve train of an internal combustion engine, said rocker arm comprising on a first end of an undersurface, a support for a cam-actuated push rod, on a second end of the undersurface, a contact surface for at least one gas exchange valve, and between the first and second ends, a cross-bore through which the rocker arm is pivoted on an axle, the rocker arm can be uncoupled in a region of the axle at least partially from a pivoting movement in a region of the contact surface when the rocker arm is subjected to a tilt loading by the push rod.
BACKGROUND OF THE INVENTION
In a rocker arm of the pre-cited type known form DE-A 33 13 437, the axle is connected to a clearance compensation element. A slide connected to a solenoid acts on the one-way valve of the clearance compensation element in opening direction, i.e. in a direction toward a high pressure chamber. During a positive loading of the one-way valve by the slide when the solenoid is active, the hydraulically maintained rigidity of the high pressure chamber is neutralized. Upon a lifting motion of the cam, the axle of the rocker arm can now be displaced toward the solenoid so that the rocker arm pivots about its contact surface on the gas exchange valve which thus remains closed.
A drawback of this prior art rocker arm is that it is supported by hydraulic means so that it possesses a certain degree of undesired elasticity in support direction in the region of its axle. It must be remarked further that the uncoupling unit comprising the solenoid and the slide is a mechanism of a relatively complicated structure and is expensive to manufacture.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a rocker arm of the pre-cited type which eliminates the above-mentioned drawbacks.
This and other objects and advantages of the invention will become obvious from the following detailed description.
SUMMARY OF THE INVENTION
The invention achieves the above objects by the fact that the axle is guided in a slot of a pedestal fixed at least indirectly on the cylinder head, said slot extending in a direction toward the cylinder head, each of the axle and the pedestal comprising at least one reception for a total of at least one locking element, for uncoupling the pivoting movement, said locking element extends entirely in one of the receptions and for coupling the pivoting movement, the locking element can be partly displaced into the other of the receptions which is situated opposite thereto.
The measures proposed by the invention create a simple mechanism by which the rocker arm can be uncoupled at its end comprising the contact surface for the gas exchange valve at least partly, but preferably completely, from the lifting movement of the cam which actuates the push rod. The coupling means can be configured as at least one slide, but in a preferred embodiment, the coupling means comprises three slides.
The stop proposed by the invention for the axle on the cylinder head-proximate end of the slot creates an exact definition of the position of the receptions for the locking elements (slides) in the base circle phase of the actuating cam.
According to a further proposition of the invention, a spring means acts on the axle in valve direction. In the run-off phase of the cam, this spring means effects in a simple manner, a re-displacement of the axle together with the rocker arm out of the uncoupled state. In this way, the rocker arm is maintained together with the push rod in permanent contact with the cam (lost motion effect).
Advantageously, the spring means is installed in the slot and is supported at one end on this slot and at the other end, on a top surface of the axle.
Although it is conceivable to arrange the receptions for the coupling of the axle to the pedestal at an inclined position relative to the rocker arm, it is preferred to have these receptions extend in the longitudinal direction of the rocker arm. The scope of the invention also extends to a locking element in the form of one single slide but it is preferable to arrange a slide in each reception, in which case, the slide in the axle extends, in the uncoupled state, over the entire length of its reception.
In a preferred embodiment of the invention, the entire assembly of slides is displaced in at least one direction of displacement, for instance, in the uncoupling direction, by hydraulic medium pressure. In the other direction (coupling direction), the slide assembly may be displaced by the force of a spring means such as at least one compression spring. Thus, in the absence of hydraulic medium pressure, for instance when the engine has just been started, the rocker arm is in a coupled state and the gas exchange valve concerned can open.
According to still another feature of the invention, the servo medium is routed to an end face of one or both of the outer slides through at least one channel for each slide arranged in the pedestal and communicating with a supply in the cylinder head. Another possibility is to route the hydraulic medium to the respective slide through a duct extending along the axle.
The compression spring proposed as a displacing means for the slides may be replaced with an electromagnetic, magnetic or other similar means.
According to a final proposition of the invention, the two ends of the axle may project out of the rocker arm and each end may be guided in a slot of a separate pedestal.
The invention will now be described more closely with reference to the appended drawings.
REFERENCES:
patent: 5893344 (1999-04-01), Church
patent: 3313437 (1983-10-01), None
patent: 3239941 (1984-05-01), None
patent: 19604866 (1997-08-01), None
patent: 19500575 (1998-07-01), None
patent: 2068495 (1981-08-01), None
Haas Michael
Schmidt Dieter
Speil Walter
Bierman, Muserlian and Lucas
Ina Walzlager Schaeffler OHG
Lo Weilun
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