Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1996-05-28
1997-08-12
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 9041, 123 9043, 123 9046, F01L 134, F01L 124, F02D 1302
Patent
active
056554877
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a switchable support element for a lever valve drive of an internal combustion engine comprising a hollow cylindrical housing arranged with an outer peripheral surface in a reception bore of a cylinder head, an inner element supported on the housing by a compression spring being arranged for axial displacement within the housing, while one front end of the housing or of the inner element bears at least indirectly against a finger lever and a second front end bears against the cylinder head, the housing and the inner element each comprising at least one radial or tangential bore aligned with each other in a base circle phase of a cam, a coupling means in form of a piston is arranged in at least one of the said bores while being displaceable in bore direction so that in a coupled state, the piston bridges an annular gap between the housing and the inner element thus causing a positive engagement therebetween, and a coupling and an uncoupling of the two elements concerned being effected optionally by a spring force or by a hydraulic medium.
A device of the aforesaid type, known from WO-A-91/12 415, likewise comprises an inner element arranged for axial displacement in a housing. Two pistons serving as coupling means are associated with the inner element. To effect coupling, hydraulic medium can be fed to the pistons from the base of a bore of housing. A basic drawback of this construction is that the support element in conjunction with the associated levered drive is of a rather complicated design to enable it to achieve at least two different lifting curves. Thus, for example, this prior art solution comprises two cams with differing lifts which act on at least two finger levers one of which is supported on a support element of the generic type. A further drawback of the known support structure is that the arrangement and configuration of the coupling means results in a relatively large overall axial height of the support element. Moreover, the prior art document discloses no measures, for example, for coupling the housing and the inner element in the absence of hydraulic medium pressure, and no concrete means for a supply of hydraulic medium to the coupling elements are described.
It is therefore an object of the invention to provide an improved support element of the initially mentioned type in which the aforesaid drawbacks are eliminated and which particularly comprises a coupling mechanism using simple means and functioning reliably both in the presence and in the absence of hydraulic medium pressure.
The invention achieves this object by the fact that the spring force is produced by a compression spring which is supported at one end on a base of a bore of the housing and whose second end acts on a front end of the piston which, in the uncoupled state of the housing and the inner element, is arranged for axial displacement in the bore of the housing and to accomplish coupling, engages by parts of its outer peripheral surface into the bore of the inner element. The pistons described here permit a reliable positive locking and unlocking between the housing of the support element and its inner element. Advantageously, two locking pistons are used, but it is also conceivable to use several locking elements spaced along the length of the support element to permit a graduated switching to smaller valve lifts. It is likewise possible to configure the pistons merely as indirect coupling means which act on direct coupling means such as sliders. It is possible in all envisaged embodiments to provide for a displacement of the coupling means at least partially in an axial direction. Needles, wedges and the like may also be used as coupling means. The bores then have any required shape so that they can be regarded, in general, as recesses for the coupling means.
The scope of protection of the switching device of the invention also covers insertion elements for rocker arms, bridge-type drives for simultaneous actuation of two gas exchange valves, and the like. The invention likewise envisages th
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Patent Abstracts of Japan, vol. 10, No. 304, Jun. 1986 Publication No. JP61118518 (1 page).
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Haas Michael
Maas Gerhard
INA Walzlager Schaeffler KG
Lo Weilun
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