Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1991-01-14
1992-05-12
Cross, E. Rollins
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 9031, 464 2, F01L 134
Patent
active
051117800
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to a drive arrangement for a camshaft in accordance with the introductory portion of claim 1.
In such drive arrangements for camshafts, which are known, for example, from U.S. Pat. No. 3,258,937 or from the German Offenlegungsschrift 36 16 234, the gear-change sleeve is shifted axially in order to change the valve control times, the gear-change sleeve being rotated relative to the drive wheel because of the spiral gearing. This rotation is passed on to the camshaft by way of the straight gear.
In equipment according to U.S. Pat. No. 3,258,937, the drive wheel is fastened to a shaft, which runs on bearings near the driving wheel in the cylinder head and, at its end averted from the drive wheel, in a recess in the adjacent front side of the camshaft. In a front side recess, it accommodates the gear-change sleeve, which is in driving connection at one end over an external spiral gearing with the driving shaft and, at the other end, over a straight gear with the camshaft. The gear-change sleeve is shifted in the one direction by a spring, which is disposed between the drive shaft and the gear-change sleeve, and, in the other direction, by the oil pressure acting in a pressure chamber. It is possible to change the pressure in this chamber by slide valve, which is disposed axially displaceably in the drive shaft and which controls an outflow opening from the pressure chamber as a function of the rotational speed. In its axial extent, this known cam shaft drive arrangement is appreciably larger than a normal cam shaft drive arrangement with constant valve control times. It is therefore practically not possible to provide a particular internal combustion engine either with a normal camshaft drive arrangement or with a camshaft drive arrangement with variable control times or to modify a camshaft with a normal camshaft drive arrangement subsequently to a camshaft with variable control times. If the internal combustion engine is to be installed in motor vehicles and, particularly, in passenger cars, the accommodation of an internal combustion engine, which is only slightly larger in any dimension, creates exceptional problems because of the exceedingly confined space conditions in the engine compartment and these problems frequently necessitate a costly change in the car body.
In the embodiment of the German Offenlegungsschrift 36 16 234, the drive wheel is rotatably supported on bearings at the end of the cam shaft and connected with a sleeve, which protrudes into a recess on the face of the camshaft and has an internal spiral gearing, which interacts with an corresponding external spiral gearing of the gear-change sleeve, which is also disposed in his recess. The gear-change sleeve, moreover, is provided with an external straight gear, which interacts with a corresponding internal straight gear in the aforementioned recess on the face. In this case, the gear-change sleeve is shifted in both directions by oil pressure. For this purpose, the gear-change sleeve is connected over a universal joint with a doubly acting operation piston, which is disposed in a cylinder and divides the space of this cylinder into two working spaces, which either are acted up by oil under pressure or from which such pressure is released. By these means, it becomes possible to shift the gear-change sleeve in both directions and to change correspondingly the position of the camshaft relative to the drive wheel. This drive arrangement for the camshaft has appreciably larger axial dimensions than does a normal camshaft driving arrangement, so that it cannot be installed in place of the latter. Moreover, the camshaft bearing next to the drive wheel must have a much larger diameter than normally, because the camshaft must be constructed with a larger than normal diameter at this end in order to be able to accommodate the adjusting device.
It is an object of the invention to provide a camshaft driving arrangement of the specified type, which is sufficiently compact, so that it can be used without significant changes in
REFERENCES:
patent: 4787345 (1988-11-01), Thoma
patent: 4903650 (1990-02-01), Ohlendorf et al.
patent: 4976229 (1990-12-01), Charles
Audi AG
Cross E. Rollins
Lo Weilun
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