Internal-combustion engines – Poppet valve operating mechanism – Tappet
Reexamination Certificate
1999-08-11
2001-04-10
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
Tappet
C123S090120, C123S090160
Reexamination Certificate
active
06213076
ABSTRACT:
FILED OF THE INVENTION
The invention relates to a cylinder head assembly of an internal combustion engine, and more particularly to a tappet for a valve drive of an internal combustion engine, including an outer circular ring shaped section which encloses a circular section movable axially relative thereto, with both sections acted upon in the area of their bottoms by cams of different lifts, and selectively interconnectable by coupling elements which lap over a ring surface between the sections and acted upon at least in one direction of displacement by a servo means, such as hydraulic fluid, with the servo means being conducted from a feed bore, terminating in the receiving bore of the cylinder head, through a juncture in the skirt in communication with the feed bore, along at least one channel extending preferably on the inner wall of the skirt, to a first reservoir between the bottom of the circular ring shaped section and a radial web disposed underneath the bottom in direction of the tappet and arranged between the skirt and the circular section.
BACKGROUND OF THE INVENTION
A tappet of this type is disclosed in German publication DE-OS 43 14 619. In the event, the tappet should be installed in its receiving bore in the cylinder head at a significant angle to the vertical, i.e. in an extreme slanted disposition, an unfavorable assembly situation may occur in which the annular reservoir, which is bounded by the circular ring shaped section, as well as partial regions of a central reservoir, which is enclosed by the circular section, may substantially run empty on hydraulic fluid. This, for example, may be ascertained when the tappet should be integrated in a valve drive of an opposed engine with cylinder barrels extending orthogonal to the vertical.
The lack of sufficient hydraulic fluid and the resultant accumulation of air in the reservoirs leads, on the one hand, to a restriction of a clearance compensation function of a hydraulic clearance compensation element, which is connected to the circular section, as a consequence of compressibility of its high pressure chamber over a certain period, and, on the other hand, to misalignments of the coupling elements for selectively connecting the sections to one another.
OBJECT OF THE INVENTION
It is thus an object of the invention to provide a slantingly mounted tappet of the afore-stated type, obviating the afore-stated drawbacks and so designed as to result in a tappet which reliably prevents leakage of servo means with particularly simple measures.
SUMMARY OF THE INVENTION
This object is attained by the providing the receiving bore for the tappet at an angle of 45-90° with respect to the vertical, with the juncture of the skirt being disposed at a lowest point of the tappet, when viewed in direction of gravity, and with a port of the channel into the first reservoir being positioned in the area of a highest section of an edge of the radial web, when viewed in direction of gravity.
By disposing the juncture of the skirt at the lowest point of the tappet, when viewed in direction of gravity, and at the same time positioning the port of the channel into the first reservoir at the highest section of an edge of its radial web, when viewed in direction of gravity, the first ring-shaped reservoir, when shutting down the internal combustion engine, runs empty on hydraulic fluid only to the level of the port of the channel. Thus, a sufficiently large amount of hydraulic fluid is retained in this reservoir when restarting the internal combustion engine, whereby this amount ensures, on the one hand, an unobjectionable clearance compensation function of the clearance compensation element, and, on the other hand, the immediate availability of a sufficient hydraulic fluid column in front of the coupling elements for displacement of the coupling elements.
According to a first embodiment of the invention, it is proposed to design the channel, starting from the juncture in the skirt, as circumferential groove at the inner wall and subsequently continued in the form of a longitudinal channel on the inner wall of the skirt in the direction towards the edge of the radial web. This circumferential groove may also be substituted by a helical groove which extends at the inner wall of the skirt up to the port at the edge of the radial web.
The invention is, in particular, appropriate when positioning the feed bore for supply of the hydraulic fluid to the juncture in the skirt substantially beneath the tappet, when viewed in direction of gravity. A disposition of the feed bores above the tappet eliminates the problems, as referred to above, and relating to an emptying of the first reservoir of hydraulic fluid.
Instead of the described helical configuration or configuration of an annular channel with subsequent axial channel, other designs are conceivable as well, as long as the port into the first reservoir is arranged at a geodetic elevated position of the tappet.
A concrete feature of the invention includes the formation of the channel in a separate axial section which extends along the inner wall of the skirt. According to a further development of the invention, this separate axial section may be an integral part of a radial web which bounds the first reservoir in cam-distal direction. Suitably, the axial section and the radial web are made of sheet metal or similarly appropriate material.
Application of the features according to the invention is in particular useful when providing the tappet with a hydraulic clearance compensation element. At the same time, it is proposed to provide in the skirt only one juncture for hydraulic fluid for acting commonly upon the clearance compensation element and the coupling elements. This measure particularly simplifies the assembly.
The invention is not limited to the cup-shaped tappet as involved here, but relates also to further valve drive elements, such as roller tappets, hydraulic support elements or like members that run the risk that their reservoirs empty when installed in slanted disposition.
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Fischer Gerald
Haas Michael
Maas Gerhard
Dahbour Fadi H.
Feiereisen Henry M.
Ina Walzlager Schaeffler OHG
Walberg Teresa
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