Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1998-07-31
2000-04-25
Lo, Wellun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 905, 123 9055, F01L 1300, F01L 125, F01L 114
Patent
active
060531339
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Field of the Invention
The invention concerns a tappet for a valve train of an internal combustion engine for a valve train, which tappet (1) is installed in a bore (6) of a cylinder head (7) of an internal combustion engine and can be switched to different valve lifts for at least one gas exchange valve, said tappet (1) comprising an annular and a circular bottom section (2, 3) arranged concentrically to each other and contactable each one by a cam of different lift, the tappet (1) being guided in the bore (6) by a skirt (4) connected to the annular bottom section (2), said annular and circular bottom sections (2, 3) being dispaceable relative to each other and adapted to be coupled to each other in the region of their common annular plane (8) by coupling means (10) which are displaceable radially or secant-like by a servo medium at least in a first direction of displacement, the skirt (4) comprising at least one inlet (25) for the servo medium, which inlet (25) serves to convey the servo medium from one end (22) of a supply gallery (23) which intersects the bore (6) of the cylinder head (7) to a reservoir (15) arranged in at least one of the bottom sections (2, 3).
2. Background of the Invention
Such a tappet is known for example from EP-OS 06 20 36. A drawback of this tappet is that its hydraulic medium supply paths are situated in the bore of the cylinder head. This requires complicated modifications to cylinder heads of known design or an expensive manufacture of these paths in the cylinder heads. At the same time, due to their height, it is not guaranteed that the coupling means can be permanently supplied with hydraulic medium. Besides this, the prior an contains no suggestion for a person skilled in the art as to how the switching operation of the coupling means can be accelerated. Under unfavorable conditions, it is possible, especially at high engine speeds that the available switching time window is not sufficient to build up the pressure required for a displacement of the coupling means in the reservoir concerned, Since, as a rule, such coupling means are reset by mechanical spring means, it is only the short time interval "cam base circle" that is available to the spring means to reset the coupling means with falling servo medium pressure by pressing the servo medium back into the gallery
At the same time, according to EP-OS 06 20 360, a separate path leading from the cylinder head is provided for a hydraulic medium supply to a hydraulic clearance compensation clement arranged in the tappet. This separate path in the cylinder head necessitates separate oil ducts in the tappet concerned. This likewise increases the costs of manufacture both of the cylinder head and the tappet.
OBJECT OF THE INVENTION
It Is therefore the object of the invention to create a tappet of the initially cited type in which the mentioned drawbacks are eliminated and a low-wear switching is permitted even at high engine speeds, particularly with the use of simple means.
SUMMARY OF THE INVENTION
The tappet of the invention for a valve train, which tappet is installed in a bore of a cylinder head of an internal combustion engine and can be switched to different valve lifts for at least one gas exchange valve, said tappet comprising an annular and a circular bottom section arranged concentrically to each other and contactable each one by a cam of different lift, the tappet being guided in the bore by a skirt connected to the annular bottom section, said annular and circular bottom sections being displaceable relative to each other and adapted to be coupled to each other in the region of their common annular plane by coupling means which are displaceable radially or secant-like by a servo medium at least in a first direction of displacement, the skirt comprising at least one inlet for the servo medium, which inlet serves to convey the servo medium from one end of a supply gallery which intersects the bore of the cylinder head to a reservoir arranged in at least one of the bottom sections, is characteriz
REFERENCES:
patent: 5351662 (1994-10-01), Dopson et al.
patent: 5431133 (1995-07-01), Spath et al.
patent: 5615651 (1997-04-01), Miyachi
patent: 5651335 (1997-07-01), Elendt et al.
Faria Christof
Maas Gerhard
Ina Walzlager Schaeffler OHG
Lo Wellun
LandOfFree
Tappet for an internal combustion engine valve drive 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 an internal combustion engine valve drive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tappet for an internal combustion engine valve drive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-985012