Internal-combustion engines – Poppet valve operating mechanism – Tappet
Patent
1998-06-30
1999-11-02
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Tappet
123 905, F01L 124
Patent
active
059750383
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a tappet for the valve drive of an internal combustion engine, including a cup-shaped housing formed by a bottom and a cylinder wall, and an insert arranged inside the housing and including an outer sleeve, which bears upon the cylinder wall, as well as an inner guide tube connected with the sleeve and displaceably guiding therein a hydraulic clearance compensation element, with the insert forming with the cylinder wall an oil channel extending from a bottom-distant inlet opening of the cylinder wall to a port adjacent an oil chamber and neighboring the bottom, and with a piston part of the clearance compensation element subdividing the oil chamber in an inner oil reservoir and an outer oil reservoir which are connected to one another via a transfer opening arranged in the bottom.
BACKGROUND OF THE INVENTION
Hydraulic cup-shaped tappets with valve clearance compensation elements and inserts for restriction of the oil amount and maintaining the required oil reservoir in the compensation element are known. Document EP 0 443 146 B1 shows a tappet having an insert formed in one piece with the cylinder wall of the cup-shaped housing, resulting in a complicated structure and assembly.
Document DE 36 38 202 A1 discloses a tappet having a hydraulic clearance compensation element and provided with an anti-rotation device by means of a needle roller which partially projects out of the tappet housing and snugly fits in a groove of the machine part that surrounds the tappet and has a bore for guiding the tappet for displacement in an axial direction. This arrangement is however not directed to a cup-shaped tappet but to a differently designed roller tappet.
Document EP 0 187 217 B1 shows a cup-shaped tappet of the afore-stated type which slightly rotates about its longitudinal axis during reciprocating movement in the cylinder head bore. When this tappet is so arranged in the cylinder head that its longitudinal axis is inclined with respect to the vertical, the inlet opening for the hydraulic oil may migrate between a highest position and a lowest position. Even when the inlet opening has reached its lowest position, the inner oil reservoir of the clearance compensation element remains completely filled with a minimum amount when the combustion engine is shut down because the transfer opening, which connects the inner oil reservoir with the outer oil reservoir, is located at its highest point since in this design the port of the oil channel and the transfer opening oppose each other diametrically.
Thus, in view of the fact that the transfer opening as outlet of the inner reservoir occupies its highest point when the inlet opening is at its lowest point, oil is prevented from flowing out of the inner reservoir. However, in this disposition, the hydraulic oil may flow back at least partially from the outer oil reservoir, which surrounds the inner oil reservoir, via the port, the oil channel and the inlet opening into the supply conduit of the cylinder head. When the internal combustion engine is started again, the partially emptied outer oil reservoir of each cup-shaped tappet must therefore be filled first before the tappet exhibits its even operating behavior.
SUMMARY OF THE INVENTION
The invention is based on the object to so develop the tappet that the entire supply of hydraulic oil is available at any time to positively eliminate irregular operating behavior, in particular during the starting phase, and thus prevent e.g. resultant rattling noises.
This object is attained in accordance with a first proposal of the invention by configuring the insert of the oil channel as a helical groove formed in the outer sleeve. When arranging the tappet and the tappet bore in the cylinder head with inclined axis, the inlet opening for the hydraulic oil can then occupy the lowest point, with the port of the oil channel occupying its highest point so that oil is prevented from escaping from the outer oil reservoir.
According to another proposal, the object is attained in accor
REFERENCES:
patent: 4951619 (1990-08-01), Schaeffler
patent: 5651335 (1997-07-01), Elendt et al.
Fischer Gerald
Speil Walter
Feiereisen Henry M.
Ina Walzlager Schaeffler OHG
Lo Weilun
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