The PatVRA is an apparatus for reducing vibrations passing from an engine to a transmission line;
the crankshaft of an engine is coupled to a transmission line by a phaser introducing a waving, along a crankshaft rotation, angle difference between the crankshaft and the transmission line, the waving angle difference is preventing vibrations transmission from the crankshaft to the transmission line.
The application of the PatVRA in a straight-four plane-crankshaft engine, i.e. in a typical 4-cylinder engine (the flywheel is shown transparent):
As the "cross-plane" crankshaft sraight-four engines (Yamaha-R1, motoGP), the above Vibrations Reduction mechanism prevents inertia torque pulses from passing to transmission and load, without sacrificing the advantages of the typical plane-crankshaft straight-four engine.
Engines like the single cylinder, the typical two cylinder in-line, the boxer with two or four cylinders, the typical four cylinder in-line have a common characteristic / disadvantage: the total kinetic energy of their pistons and connecting rods varies significantly during the cycle.
In order to rotate the crankshaft at constant angular velocity while it drives connecting rods and pistons, a strong oscillating torque is necessary.
Without this torque a fluctuation of the angular velocity of the crankshaft, during a crankshaft rotation, is unavoidable, i.e. an angle difference of the crankshaft from where it would be if it were rotating with its mean angular velocity.
To experimentally identify the fluctuation of the crankshaft angular velocity, the cylinder head of the engine is removed (to release the engine from gas pressure loads), the crankshaft is driven (through a resilient coupling) to rotate at some mean angular velocity, and the instant angular velocity of the crankshaft versus the crankshaft rotation angle is measured.
The fluctuation of the crankshaft angular velocity increases in case the flywheel is removed.
To practically experience what the fluctuation of the crankshaft angular velocity causes: with a car powered by the engine operating at high rpm (round per minute) and cruising on a highway, the gas pedal is released; while the combustion torque pulses to the transmission and to the tires are eliminated, the fluctuation of the crankshaft angular velocity continues transmitting inertia torque pulses to the transmission and to the tires, creating noise and vibrations, and increasing friction and wear.
In comparison, in a 4-in-line cross-plane crankshaft engine (an arrangement used in some mass production motorcycle engines and in some moto-GP / racing motorcycle engines) the total kinetic energy of the four pistons remains nearly constant along a crankshaft rotation, while the gearbox receives almost pure combustion torque pulses improving, among others, the feeling and the grip of the rear tire with the road; these advantages come with the disadvantage of uneven firing.
In Figs. 2 to 5, 10 to 13, 18 to 21 and 26 it is shown a mechanism / linkage / phaser.
The rotation - at constant angular velocity - of the transmission member 5 about the rotation axis 4, causes through the control member 7 and the links (or connecting rods) 8 and 9, the rotation of the crankshaft 3 about the rotation axis 4 at a variable, along a rotation of the crankshaft, angular velocity. The angle difference between the transmission member 5 and the crankshaft 3 versus the rotation of the crankshaft is shown by the curve (a) of Fig. 1.
Fig. 2 and 10 show a 80.5 degrees angle difference between the transmission member 5 and the crankshaft 3; in Figs. 3 and 11 the transmission member 5 is rotated by 90 degrees causing an increase of the angle difference at 83.3 degrees; in Figs. 4 and 12 the transmission member is rotated for another 90 degrees causing a decrease of the angle difference at 80.5 degrees; in Figs. 5 and 13 the transmission member is rotated by another 90 degrees causing an increase of the angle difference at 83.3 degrees.
In Figs. 11 and 13 the centers of the pivots of the links 8 and 9 are at a straight line; there is where the angle difference between the crankshaft 3 and the transmission 5 maximizes. The control member 7 keeps / holds the pivot between the two links 8 and 9 at constant distance from the rotation center of the control member 7, avoiding "uncertainty". The mechanism generates a second order angle difference (Fig. 1, (a)): the angle difference maximizes two times per crank rotation (Figs. 11 and 13) and minimizes two times per crank rotation (Figs. 10 and 12).
In Figs. 6 to 9, 14 to 17, 22 to 25 and 27 it is shown a similar mechanism (only the lengths of the various links change). The rotation - at constant angular speed - of the transmission member 5 causes, through the control member 7 and the links (or connecting rods) 8 and 9, the rotation of the crankshaft 3 at a variable, along a rotation of the crankshaft, angular velocity. The angle difference between the crankshaft 3 and the transmission member 5, versus the rotation of the crankshaft, is shown by the curve (b) of Fig. 1, and is substantially larger than that of the curve (a); and as the curve (a) it is of second order, too.
From Figs. 6 and 14 to Figs. 7 and 15 the transmission member rotates for 90 degrees causing an increase of the angle difference from 68.3 degrees to 79.3 degrees; from Figs. 7 and 15 to Figs. 8 and 16 the transmission member rotates for 90 degrees causing a decrease of the angle difference from 79.3 degrees to 68.3 degrees; from Figs. 8 and 16 to Figs. 9 and 17 the transmission member rotates for 90 degrees causing an increase of the angle difference from 68.3 degrees to 79.3 degrees.
In Figs. 28 to 30 it is shown the application of the PatVar in a 4-cylinder plane-crankshaft engine (plane crankshaft means that the crankshaft rotation axis and the centers of all the crankpins are on a plane).
The flywheel is rotatably mounted, by a roller bearing, on the crankshaft 3.
The control member 7 is rotatably mounted on the casing 2 of the engine 1 by a roller bearing (it is the big diameter roller bearing).
The link (or connecting rod) 9 is pivotally mounted, at one end, to the transmission member 5 (which, in this case, is the flywheel), the link 9 is pivotally mounted, at its other end, to the link 8. The link 8 is, at its other end, pivotally mounted on the crankshaft 3 (actually on an arm secured to the crankshaft, in the specific case). The control member 7 is pivotally mounted to the links 8 and 9.
When the crankshaft is driven (through an elastic / resilient connection, and with the cylinder head and the flywheel removed) to rotate at an angular velocity, the mass and the mass distribution of the rotating / reciprocating parts (crankshaft, connecting rods and pistons, Figs. 28 to 30) causes an angle difference between the crankshaft and a shaft rotating uniformly with the mean angular velocity of the crankshaft.
This "angle difference" is presented by a curve like the curve (b) of Fig. 1.
The design of the phaser 6 (the lengths of its various links, their arrangement etc) is based on this "angle difference".
With the proper phaser, the transfer of torsion inertia loads between the crankshaft and the transmission line (the gear box in this case) is substantially reduced or even eliminated.
This means that at operation the flywheel (and the load) can receive nearly pure combustion torque pulses and no inertia torque pulses. This also means that at high revs with closed throttle, the engine can leave unloaded the transmission from idling torque, reducing the noise and the friction.
The PatVRA.exe windows "exe" program demonstrates the basics of the mechanism:
The blue arm rotates at constant angular velocity.
The long green arm rotates at variable angular velocity.
The red "sinusoidal" / "waving" curve, at bottom, is the angle difference between the blue arm (flywheel?) and the long green arm (crankshaft?)
The connection can remain rid of inertia torsion loads.
