Internal-combustion engines – Four-cycle – Variable clearance
Reexamination Certificate
2001-10-05
2003-07-08
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Four-cycle
Variable clearance
C123S0480AA
Reexamination Certificate
active
06588384
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application No. 100 51 271.2 filed Oct. 16, 2000, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to an apparatus for changing the compression ratio in a reciprocating piston type internal-combustion engine.
In the usual piston drives in internal-combustion engines the position of the piston in its cylinder depends exclusively from the angular position of the engine crankshaft. For changing the compression ratio as a function of operational conditions, it is known to provide an adjusting arrangement in which the connecting rod of the piston is subdivided into two connecting rod portions which are coupled to one another by a central joint and further, a control arm is articulated at one end to the connecting rod. The other end of the control arm is secured to a support which is displaceably mounted on the engine housing. Such constructions are described, for example, in German Published Applications 29 35 073, 29 35 977, 30 30 615 and 37 15 391. In these constructions the control arm is directly coupled to the central joint which involves significant structural and operational problems. The central joint has a substantial width and is therefore very heavy. Its substantial weight, however, cannot be compensated for by counterweights mounted on the crankshaft because of the limited space available in the engine. It is an overall disadvantage of these prior art constructions that the moved masses, that is, the pistons and the connecting rods are increased and thus a larger weight has to be overcome.
To avoid the above-outlined disadvantages, it has been attempted to change the compression ratio by supporting the crankshaft in eccentric rings rotatably mounted in the engine block and connected with a setting drive. By turning the eccentric rings the position of the rotary axis of the crankshaft is shifted, as a result of which in the upper dead center of the piston its the distance from the cylinder top (roof) is varied. For this purpose, German Published Patent Application 30 04 402 provides that each eccentric ring is coupled with a gear which meshes with a pinion mounted on a setting shaft. The setting shaft is oriented parallel to the crankshaft and is connected with a setting drive. Apart from the substantial structural outlay, such a construction requires increased space for accommodating the eccentric rings and the gears disposed adjacent thereto.
Further, German Published Application 36 01 528 discloses an arrangement in which the eccentric rings carrying the crankshaft bearing are connected with a partially cylindrical shell oriented concentrically to the eccentric rings and extending along the entire length of the engine block. On its outer face the shell is provided with a toothed segment which meshes with a setting worm oriented transversely to the crankshaft and being connected with a setting drive. Such a system, despite a favorable structural length as concerns the crankshaft bearing, has the disadvantage that a very compact structural member is provided for the synchronous shifting of the eccentric rings. Further, the torques generated due to the eccentricity of the crankshaft bearings relative to the bearing axis of the eccentric rings can be taken up solely by the setting worm. Since at all times only a few teeth are in a meshing relationship with such a setting worm with a slight degree of overlap, the material of the components is exposed to substantial stresses because of the pulsating loads occurring during operation. Even a slight play between the toothed segment and the setting worm may lead to a rapidly progressing wear.
In addition, German Published Application 36 44 721 describes a system in which each eccentric ring is connected with a laterally projecting lever which is coupled to a slide at its free end. Laterally and parallel to the crankshaft a setting shaft is supported which is provided with a setting drive and fork-like claws surrounding the slide of the respective eccentric rings. Since slides cannot be guided in a practically play-free manner, this system too, has the disadvantage that because of the pulsating torques acting through the eccentric rings, the components are, in that region, exposed to significant stresses. This leads to an increasing wear in the guide for the slides.
U.S. Pat. No. 6,247,430 discloses further examples of setting devices of the above-outlined type. All known embodiments, however, require a particular configuration of the engine block.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved compression ratio setting device of the above-outlined type which is structurally simpler and is easier to manufacture.
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 an engine block; a plurality of cylinders arranged in line in the engine block; a piston accommodated for reciprocating motion in respective cylinders and each having an upper dead center position; a plurality of eccentric rings; ring bearings for supporting the eccentric rings in the engine block for rotation about a ring axis; a crankshaft; a plurality of crankshaft bearings supported in respective eccentric rings and carrying the crankshaft for rotation about a crankshaft axis which is radially spaced from the ring axis; a connecting rod coupling each piston to the crankshaft; a setting arm secured to and projecting from each eccentric ring; a toothed element carried by each setting arm; and a setting shaft rotatably supported on the engine block parallel to the crankshaft. A plurality of pinion elements are provided, each having a first pinion fixedly secured to the setting shaft and meshing with the toothed element of one of the setting arms and a second pinion rotatable relative to the first pinion and meshing with the toothed element of one of the setting arms. A resilient connecting member couples the first and second pinions to one another and resiliently resists a rotation of the first and second pinions relative to one another. A setting drive turns the setting shaft for adjusting together an angular position of the eccentric rings to radially shift the crankshaft axis, whereby the upper dead center position of the pistons is altered for varying a compression ratio of the engine.
An internal-combustion engine constructed as outlined above has the advantage that the setting shaft situated laterally next to the crankshaft and extending parallel thereto may be arranged in a region of the engine block which is practically not exposed to forces acting between the cylinders on the one hand and the crankshaft on the other hand. Such an arrangement has the substantial advantage that the components of the engine block designed for the force path are undisturbed. Accordingly, an already existing engine block may be modified by slight and relatively simple configurational changes by adding the bearing region for the setting shaft. The outer dimensions of the crankshaft housing need practically not be changed and thus no increased space for the engine needs to be provided in the vehicle. It is particularly expedient to arrange the setting shaft, together with its bearing, laterally to the respective principal bearings of the crankshaft.
During operation, the force components oriented in the direction of the cylinder axis and acting on the crankshaft apply a torque on the eccentric rings as a function of their eccentricity. Since such a torque has to be taken up by the setting arms and the setting drive, the earlier-described conventional systems—inasmuch as the transmission of the setting forces is effected by gears—have the disadvantage that the teeth during operation become worn, which will lead to an unavoidable play between the teeth. By using the pinion element according to the invention, any play between the teeth can be eliminated by biasing the two pinions of the pinio
FEV Motorentechnik GmbH
Kunitz Norman N.
Salser Douglas A.
Yuen Henry C.
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