Machine element or mechanism – Mechanical movements – Rotary to or from reciprocating or oscillating
Patent
1992-07-16
1994-03-29
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Rotary to or from reciprocating or oscillating
123 55AA, 1231974, F16H 2514, F02B 7522, F02B 7532
Patent
active
052974480
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
This invention relates to a crank mechanism for an internal combustion engine.
A conventional internal combustion engine employs a crankshaft to convert the reciprocating motion of the piston(s) into output torque to propel a vehicle or to act upon any other load. The crankshaft is inefficient in terms of converting the power available from the fuel combustion into usable output torque. This is because combustion of the fuel/air mixture takes place at approximately the top dead center (TDC) position of the piston. Not only the crankpin, but also the crankshaft main bearing, are consequently subjected to periodic heavy stresses. What is of greater significance, however, is that, with an internal combustion engine provided with conventional drive gear, the ignited fuel/air pressure forces cannot produce torque when the piston is either at TDC or bottom dead center (BDC), as the connecting rod and the crankpin are practically in a straight line so that there is no force component tangential to the crank circle. The torque necessary to carry the crankshaft through these two dead center positions is supplied by the inertia of the flywheel of the engine. Moreover, by the time the crankshaft has rotated through 90.degree. beyond TDC, where the turning moment is a maximum, the piston force is greatly reduced, so that the resulting torque is relatively small.
The present invention provides a crank mechanism for an internal combustion engine, the crank mechanism comprising a cylinder, a piston reciprocable within the cylinder, and a rotatable shaft, the piston being in drivable connection with the shaft via a connecting rod, a slipper and a torque lobe, the connecting rod being pivotally fixed to the piston, and the slipper being pivotally attached to the free end of the connecting rod, wherein the torque lobe is a circular plate eccentrically mounted on the shaft for rotation therewith about the axis thereof, wherein the slipper slidable along, but restrained to, the rim of the torque lobe, and wherein the slipper is constrained to move around a closed path whereby rectilinear movement of the piston is converted to rotary movement of the torque lobe or vice versa.
The invention also provides a crank mechanism for an internal combustion engine, the crank mechanism comprising a plurality of cylinders, a respective piston reciprocable within each of the cylinders, and a rotatable shaft, each of the pistons being in drivable connection with the shaft via a respective connecting rod, a respective slipper and a common torque lobe, each connecting rod being pivotally fixed to the associated piston, and each slipper being pivotally attached to the free end of the associated connecting rod, wherein the torque lobe is a circular plate eccentrically mounted on the shaft for rotation therewith about the axis thereof, wherein each slipper is slidable along, but restrained to, the rim of the torque lobe, and wherein each slipper is constrained to move around a respective closed path whereby rectilinear movement of the pistons is converted to rotary movement of the torque lobe or vice versa.
Advantageously, the or each slipper is provided with cam follower means which engage with associated cam track means adjacent to the torque lobe, the cam follower means and the cam track means constituting means for constraining that slipper to move round the associated closed path. Conveniently, the or each slipper is provided with a pair of cam followers which engage with a respective pair of cam tracks formed symmetrically in a pair of plates positioned on opposite sides of the torque lobe.
The cam followers of the or each slipper may be bearings, preferably roller bearings; and the associated cam tracks may be of elliptical configuration. In this case, the major axes of the or each pair of elliptical cam tracks do not pass through the shaft.
In a preferred embodiment, the rim of the torque lobe is constituted by a flange extending in both directions beyond the circular plate constituting the torque lobe, the or e
REFERENCES:
patent: 1783589 (1930-12-01), Shepard
patent: 1931401 (1933-10-01), Baisden
patent: 2120657 (1938-06-01), Tucker
patent: 2528386 (1950-10-01), Napper
Dodd Thomas J.
Herrmann Allan D.
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