Internal-combustion engines – Four-cycle – Variable clearance
Reexamination Certificate
1998-10-30
2001-06-19
Kamen, Noah (Department: 3747)
Internal-combustion engines
Four-cycle
Variable clearance
C123S0480AA
Reexamination Certificate
active
06247430
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application Nos. 297 19 343.0 filed Oct. 31, 1997, 198 13 386.3 filed Mar. 26, 1998 and 198 41 381.5 filed Sep. 10, 1998, which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
In normal reciprocating piston-type machines the position of the pistons in the respective engine cylinders depends exclusively from the angular position of the crankshaft. According to a conventional arrangement for changing the compression ratio as a function of operational conditions, the connecting rod of each piston is subdivided into two connecting rod parts which are coupled with one another by a central joint. Further, a control arm is articulated at one end to the connecting rod and is secured, at its other end, to a pivotal support slidable on the machine housing.
The above-outlined constructions are described, for example, in German Offenlegungsschriften (applications published without examination) 29 35 073, 29 35 977, 30 30 615 (to which corresponds U.S. Pat. No. 4,437,438) and 37 15 391 (to which corresponds U.S. Pat. No. 4,957,069). In the structures described therein the control arm is directly coupled to the central joint, giving rise to substantial structural and operational problems. The central joint has a substantial width and thus has a large weight which, at the given spatial availabilities, cannot be compensated for by counterweights mounted on the crankshaft. On the whole, it is a disadvantage of the prior art structures that the moved masses, that is, the piston and the connecting rod, are increased and therefore greater mass forces have to be overcome.
To avoid the above-noted disadvantages, it is known to change the compression ratio by supporting the crankshaft in eccentric rings which are angularly displaceably (rotatably) supported in the cylinder block and are connected with a setting drive. By rotating the eccentric rings, the position of the crankshaft is shifted such that in the upper dead center position the pistons have a greater or lesser distance from the cylinder roof. For this purpose, German Offenlegungsschrift 30 04 402 provides that each eccentric ring is coupled with a toothed gear meshing with a pinion mounted on a setting shaft which extends parallel to the crankshaft and which is coupled with a setting drive. Apart from a substantial structural and technological input, increased space is needed for accommodating the eccentric rings and the gears disposed in their vicinity.
Further, German Offenlegungsschrift 36 01 528 describes an arrangement wherein the eccentric rings which support the crankshaft bearings are connected with a partial cylinder shell arranged concentrically to the eccentric rings and extending over the entire length of the cylinder block. The partial cylinder shell is provided on its exterior with a toothed segment which meshes with a setting worm extending transversely to the crankshaft and connected with a setting drive. Despite a favorable structural length of the crankshaft support, such a system has the disadvantage that a very compact structural component for the synchronous shifting of the eccentric rings is provided, and that because of the eccentricity of the crankshaft axis relative to the support axis of the eccentric rings, torques appearing during operation may be taken up only through the setting worm. Since in such a construction only a few teeth are in a meshing relationship with a small degree of overlap, the stress on the component materials is substantial because of the fluctuating loads generated during operation. Even a small play between the toothed segment and the setting worm may lead to a rapidly progressing wear.
Further, German Offenlegungsschrift 36 44 721 describes a system in which each eccentric ring is connected with a laterally projecting lever carrying a bearing block on its free end. Laterally of and parallel to the crankshaft a setting shaft is supported which has a setting drive and which is provided with a fork-like jaw straddling the bearing block of an eccentric ring. Since the bearing blocks cannot be guided in a play-free manner, such a system too, is disadvantageous because the fluctuating torques exerted on the eccentric rings during operation lead in this region to a significant stress on the system which is coupled with an increasing wear in the zone of the bearing block guidance.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved internal-combustion engine of the above-outlined type from which the discussed disadvantages are eliminated.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the internal-combustion engine includes a cylinder block; a plurality of cylinders arranged in line in the cylinder block; a piston accommodated for reciprocating motion in the respective cylinders; a crankshaft received in the cylinder block; a connecting rod coupling each piston with the crankshaft; and a plurality of eccentric rings surrounding and supporting the crankshaft. Each eccentric ring is rotatable about a common ring axis radially spaced from the crankshaft axis. Further, ring-supporting bearing housings are accommodated in the cylinder block for supporting the eccentric rings. A ring-turning assembly adjusts in unison the angular position of the eccentric rings to radially shift the crankshaft, whereby the upper dead center position of the pistons is altered for varying the compression ratio thereof. The ring-turning assembly includes a setting drive for exerting a force upon actuation thereof; a ring-turning component connected to at least some of the eccentric rings; and a coupling element connecting the setting drive with the ring-turning components for transmitting the force exerted by the setting drive to the ring-turning components for rotating the eccentric rings.
The invention provides that in an internal-combustion engine in which the compression ratio may be altered, the support for the setting arrangement does not require an extension of the crankshaft support in the cylinder block so that the usual structural lengths for such cylinder blocks need not be increased. The ring-turning components, the bearing housings and the eccentric rings are expediently dimensioned in such a manner that an axial support for the eccentric rings is obtained. By virtue of the fact that all ring-turning components are connected to one another by means of a coupling element, a synchronous rotation of the eccentric rings is ensured.
According to an advantageous feature of the invention, that portion of an eccentric ring which is oriented towards the associated cylinder has, on its exterior, a circumferentially extending groove which is provided with a radially inwardly oriented bore and further, in the cylinder block a central oil channel is arranged from which branch channels extend which terminate with their open end at the ring-supporting bearing housing in the region of the groove provided in the eccentric ring. This arrangement ensures that the bearing surfaces of the eccentric rings as well as the crankshaft bearings arranged in the eccentric rings are supplied with lubricant.
In accordance with a further advantageous feature of the invention, at least some of the ring-supporting bearing housings are provided with a respective window through which the turning component for the associated eccentric ring passes. In this manner, a compact structure for the entire arrangement and for the turning component is obtained. The coupling element which connects the turning components with one another and with the setting drive may be, according to a further feature of the invention, formed by a setting shaft connected with the setting device and provided with pinions which mesh with the corresponding toothed elements of the respective turning components. According to a further advantageous feature of the invention, the turning components may be pivotal levers which preferably extend downwar
FEV Motorentechnik GmbH & Co. Kommandgesellschaft
Kamen Noah
Kelemen Gabor J.
Venable
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