Internal-combustion engines – Poppet valve operating mechanism – Tappet
Patent
1996-03-19
1997-06-10
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Tappet
123 9051, F01L 125
Patent
active
056366043
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a tappet for a valve drive of an internal combustion engine comprising a hollow cylindrical housing guided for axial displacement by a jacket thereof in a reception bore of a cylinder head, an end of the housing facing a cam being closed by a bottom, a guide sleeve arranged concentrically in the tappet for guiding a hydraulic clearance compensation element being supported by a connected web against the jacket which is made of two separate, bush-like sections of approximately equal diameter separated from each other preferably in the region of a central transverse plane, and a first cup-shaped section of the jacket being connected at a cam-proximate end thereof to the bottom.
A tappet of this type is described in EP-A-04 85 007 and likewise comprises a tappet jacket divided along a central transverse plane and having an upper section closed by a bottom. A web comprising a guide portion for receiving a hydraulic clearance compensation element extends radially inwards from the lower section. An oil channel leads through a plastic cushion arranged in the annular oil reservoir into the central oil reservoir for supplying hydraulic medium to the clearance compensation element. A drawback of the tappet known from EP-A-04 85 007, which is considered as the generic prior art, is that the bottom together with the two separate jacket sections and the web is a relatively solid structure. Moreover, the plastic cushion arranged in the annular oil reservoir also has a detrimental effect on the total mass and thus also on the oscillating mass of the valve drive. Due to the fact of direct suction into the reservoir which is situated at a higher lever, there exists the inherent danger of air and oil foam being sucked into the high pressure chamber during the base circle phase of the tappet. This is particularly unfavorable when the internal combustion engine is operated only for short periods, for example in the so-called "taxi" or "stop-and-go" mode and results in an undesired yielding of the valve drive during the high-pressure phase of the tappet, i.e. during valve lift. In addition, the oil transfer bead arranged in the bottom detracts from the rigidity of the bottom which as a result has to be made with a larger thickness.
A further prior art document, EP-A-04 43 146, discloses a tappet whose jacket is made integrally with the bottom and the jacket itself is also a one-piece structure. Within the tappet, there is arranged coaxial with the jacket surface, a thin-walled guide element comprising an ascending groove for hydraulic oil. This prior art document too, does not disclose any means for reducing the mass of the tappet because its jacket has a relatively solid configuration and is made integrally with the bottom. Moreover, the aforesaid guide element also increases the total mass.
It is therefore an object of the invention to provide a tappet of the precited type in which the discussed drawbacks are eliminated and which, particularly, is simple to manufacture and possesses a high strength.
The invention achieves this object by the fact that the second, lower section comprises an extension starting axially adjacent the first section and extending into the immediate vicinity of the bottom, the second section with its extension has a smaller wall thickness than the first section and is made as a sheet metal or plastic element, the extension bears by an outer peripheral surface thereof against an inner peripheral surface of the first section, the web extends from a bottom-proximate edge of the extension in cam-remote direction to support the guide sleeve, an annular groove is formed in the second section between a cam-remote edge of the first section and a facing edge of the second section oriented towards the cam, and at least one channel extends from the annular groove to feed oil into the tappet interior, said channel extending axially between the outer peripheral surface of the extension and the inner peripheral surface of the first section.
The two-piece configuration of the tappet described
REFERENCES:
patent: 5239953 (1993-08-01), Shida
Copy of Hydraulic Valve . . . Engine Abstract, vol. 10, No. 14, (M-447) (2071) Sep. 1985 (1 pg.) Patent Abstract of Japan.
INA Walzlager Schaeffler KG
Lo Weilun
LandOfFree
Tappet for a valve drive of an internal combustion engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Tappet for a valve drive of an internal combustion engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tappet for a valve drive of an internal combustion engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-758273