Internal-combustion engines – Poppet valve operating mechanism – Tappet
Patent
1997-05-27
1998-03-17
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Tappet
123 9049, F01L 124
Patent
active
057275092
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a cam follower in the form of a tappet or a lever for a valve drive of an internal combustion engine comprising a hollow cylindrical housing (2) with which the tappet (1) oscillates in a reception bore of a cylinder head, one end (3) of the tappet being closed by a disc-like bottom (4) while a hydraulic clearance compensation element (5) is arranged concetric to the housing (2) in the tappet (1), said clearance compensation element (5) comprising a cylindrical guide element (6) which bears against the bottom (4) and is arranged in a bore of an axially displaceable pressure piston (7) whose bottom (8) faces a gas exchange valve, an annular guide element (10) starting from an inner peripheral surface (9) of the housing (2) merges radially inwardly into a hollow cylindrical axial extension (11) pointing in cam-remote direction and in whose bore (12) the pressure piston (7) extends, the bottom (8) of the pressure piston (7) having a reduced diameter (13) which cooperates with an annular retention element extending radially inwards from an end of the axial extension (11), the guide element (10) comprising a diameter enlargement (14) on one end in which the retention element having a substantially radially outwards acting retention force is fixed by at least one of force engagement and positive engagement.
A tappet of the generic type is known from EP-A 30 781. The axial extension in this tappet starts from the guide element and is relatively thick-walled and of a solid configuration (see e.g. FIG. 6). An additional, separate annular groove is provided in a bore of the axial extension for fixing the clearance compensation element in cam-remote direction. A locking ring is arranged in this annular groove to prevent the clearance compensation element from falling out in cam-remote direction. A drawback of this prior art tappet is that the relatively solid configuration of the axial extension and the guide element unnecessarily increases the mass of the tappet. The machining of the groove is not only unfavorable with regard to manufacturing costs but it also weakens the cross-section of the axial extension so that material has to be added at another point to obtain the required strength.
Further, GB-A 21 62 680 discloses, for example, in FIG. 1, a lever-type cam follower having a clearance compensation element which is fixed in cam-remote direction by a separate locking ring. One drawback of this solution is that the lower end has a relatively solid configuration which has a negative influence on the overall mass of the cam follower. A further drawback is the additional work step required for making the groove for the locking ring.
It is therefore an object of the invention to create a tappet and a lever-type cam follower of the pre-cited type in which the mentioned drawbacks are eliminated and which furnishes a low-cost and easily implementable retention of the clearance compensation element in cam-remote direction while at the same time minimizing the danger of clamping of the clearance compensation element.
In one embodiment, the guide element together with its axial extension is made as a separate thin-walled component, a tappet with a simple retention means for its clearance compensation element is created which is particularly advantageous as regards its total mass, while the retention means for the hydraulic element is simple to manufacture. Fixing of the guide element on the housing can be achieved, for example, by swaging, welding, gluing, roller burnishing and the like. Due to the fact that the retention element in the form of a ring or a Belleville-type spring washer with a radially outwards acting retention force is fixed in a diameter enlargement, a simple means is created for preventing the pressure piston of the clearance compensation element from clamping on the retention element during its axial clearance compensating motion. Because the diameter enlargement is an integral part of the axial extension of the guide element, or of the bore of the lever-type cam follower, the add
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Patent Abstracts of Japan vol. 10, No. 286 Sep. 1986 & JP-A-61 104110 May 1986.
INA Walzlager Schaeffler KG
Lo Weilun
LandOfFree
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