US 6,318,323 B2Granted

Tappet for a valve mechanism of an internal combustion engine

AssigneeIna Walzlager Schaeffler oHG

InventorWalter Speil

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Abstract

A tappet (1) with a hydraulic clearance compensation element (7), a positive opening of a one-way valve (15) being effected during a base circle region α of the contacting cam (5) whereby a closing member (16) of the one-way valve (15) is loaded by an adjusting element (21), the adjusting element (21) extends through a bottom (3) of the tappet (1) and cooperates with a groove (22) on the outer peripheral surface (23) of the cam (5), the groove (22) extends over the entire periphery of the cam (5) with the exception of its base circle region so that when the base circle region α comes to be situated opposite the bottom (3), a positive opening of the closing member (16) is effected whereby no undesired relieving of the gas exchange valve actuated by the tappet (1) nor its opening due to a transmission of undesired opening movements from the cam (5) to the clearance compensation element (7) can occur in the base circle region α of the cam (5).

Claims9

Dependent claims

A valve train of an internal combustion engine comprising a tappet (1) loaded by a cam (5) of a camshaft, which tappet (1) oscillates with a skirt (2) in a bore of a cylinder head and is contacted on a top surface (4) of a bottom (3) by the cam (5), a hydraulic clearance compensation element (7) being fixed against an undersurface (6) of the bottom (3) by a bushing (8) which is in contact by one of the bushing's peripheral surfaces (9) with a pressure piston (10) that is axially displaceable relative to the bushing (8), a bottom (11) of the pressure piston (10) faces at least one gas exchange valve, a high pressure chamber (13) is arranged axially between the bottom (11) and an annular shoulder (12) of the bushing (8) and a reservoir (14) for hydraulic medium is, arranged preferably axially between the annular shoulder (12) and the bottom (3), the annular shoulder (12) having at least one passage (19) which is closed on a side nearer the high pressure chamber (13) by a one-way valve (15) which opens towards the high pressure chamber (13), a closing member (16) of the one-way valve (15) is biased towards the reservoir (14) by a spring means (17), and the closing member (16) can be displaced toward the bottom (11) by an adjusting element (21) which extends through an opening (20) of the bottom (3) and cooperates with a groove (22) on the outer peripheral surface (23) of the cam (5), characterized in that

the groove (22) extends over the entire outer peripheral surface (23) of the cam (5) with the exception of a base circle region α, and the groove (22) has a depth so that the adjusting element (21) extending in the groove (22) releases the closing member (16) so that the closing member (16) bears against the passage (19) due to the force of the spring means (17);
the force of the spring means (17) has a magnitude so that for opening the closing member (16) during contact of the base circle region α of the cam (5), a hydraulic medium differential pressure of Δp≧0.4 bar is required at the cross-section A of the passage (19);
and
a closing ramp (β) adjoining a run-off flank (γ) of the cam (5), as seen in rotating direction of the cam (5), has a height of <0.1 mm.

1 more element

A valve train of an internal combustion engine with a means for avoiding high pressure in a high pressure chamber of a tappet during base circle operation of the engine, comprising a tappet (1) loaded by a cam (5) of a camshaft, which tappet (1) oscillates with a skirt (2) in a bore of a cylinder head and is contacted on a top surface (4) of a bottom (3) by the cam (5), a hydraulic clearance compensation element (7) being fixed against an undersurface (6) of the bottom (3) by a bushing (8) which is in contact by one of the bushing's peripheral surfaces (9) with a pressure piston (10) that is axially displaceable relative to the bushing (8), a bottom (11) of the pressure piston (10) faces at least one gas exchange valve, a high pressure chamber (13) is arranged axially between the bottom (11) and an annular shoulder (12) of the bushing (8) and a reservoir (14) for hydraulic medium is arranged preferably axially between the annular shoulder (12) and the bottom (3), the annular shoulder (12) having at least one passage (19) which is closed on a side nearer the high pressure chamber (13) by a one-way valve (15) which opens towards the high pressure chamber (13), a closing member (16) of the one-way valve (15) is biased towards the reservoir (14) by a spring means (17), and the closing member (16) can be displaced toward the bottom (11) by an adjusting element (21) which extends through an opening (20) of the bottom (3) and cooperates with a groove (22) on the outer peripheral surface (23) of the cam (5), wherein

the groove (22) extends over the entire outer peripheral surface (23) of the cam (5) with the exception of a base circle region α, and the groove (22) has a depth so that the adjusting element (21) extending in the groove (22) releases the closing member (16) so that the closing member (16) bears against the passage (19) due to the force of the spring means (17),
the force of the spring means (17) has a magnitude so that for opening the closing member (16) during contact of the base circle region α of the cam (5), a hydraulic medium differential pressure of Δp≧0.4 bar is required at the cross-section A of the passage (19);
and
a closing ramp (β) adjoining a run-off flank (γ) of the cam (5), as seen in rotating direction of the cam (5), has a height of <0.1 mm.

1 more element

Dependencies are inferred from the claim text.