Combined axial and torsional crankshaft vibration damper for reciprocating engine

A combined axial and torsional crankshaft vibration damper for reciprocating engines comprising a hub fastened to a crankshaft and a inertia ring connected to the hub by a material that transmits a portion of the vibratory movement of the crankshaft to the inertia ring which tends to continue constant rotational movement and resists the vibrational movement and dampens the axial and torsional vibration of the crankshaft.

TECHNICAL FIELD 
The invention relates to a vibration damper and more particularly to a 
combined axial and torsional crankshaft vibration damper for a 
reciprocating engine. 
BACKGROUND ART 
The increased emphasis on improving power density and first cost of 
internal combustion engines has led to increased running speed, increased 
piston stroke and increased peak firing pressures of combustion with in 
the cylinders. These improvements tend to place the crankshaft under 
increasingly higher stress and vibratory torque. 
Increased running speed places the internal combustion engine crankshaft 
under higher stress due to higher inertial loading as well as bringing 
previously excluded natural modes of vibration within the new higher 
operating speed range of the engine. 
Increasing the piston stroke of the engine enlarges the engine's 
displacement and its power output. However the crankshafts pins or throws 
must be set further from the central supporting main journals to achieve 
the increased stroke. The lengthening of the crankshaft support geometry 
to carry pin loads makes the crankshaft more flexible and weaker. 
In the past only very large internal combustion engines with piston bore 
diameters above 300 millimeters were under much risk from crankshaft 
failure due to axial vibration. Crankshaft axial vibration is a mode of 
vibration resulting from the crankshaft expanding and compressing along 
its axis of rotation. This mode of vibration affects the crankshaft cheeks 
or pin throws. The cheek is that part of the crankshaft connecting the 
main journals with the eccentrically mounted pins. The U shape of the 
cheeks and pins extending from the main journals make the cheeks 
susceptible to vibration toward and away from the middle of the "U's", 
much like a "U" shaped tuning fork. Typically the comparatively short, 
stiff and low weight crankshafts of engines with less than 300 millimeter 
piston bores lacked problems with axial modes of vibration. The stiffness 
and light weight of heretofore made small crankshafts predetermined them 
to have comparatively high natural frequencies, which were well above 
frequencies excited at the engines highest operating speed. 
Internal combustion engine crankshafts must also endure high torsional 
vibrations. Since internal combustion engines do not produce smooth power 
and experiences positive and negative speed fluctuations within each 
revolution of the crankshaft. Normally the engine is equipped with a 
flywheel to smooth the torque and speed fluctuations, which would 
otherwise be more significantly present in the engine drive line. When the 
engine revolves subcomponents and segments about the crankshaft centerline 
as well as subcomponents and segments of any driven piece of equipment, 
there is always certain rotational flexibility between successive rotating 
masses. The flexibility existing between the rotating masses of the engine 
drive line allow for slight angular deflections to propagate among, 
between and through the engine drive line. This angular vibration makes 
the internal combustion engine experience torsional vibrations between the 
drive line masses. 
Torsional vibrations and/or axial vibrations present within an internal 
combustion engine may not be acceptable. As these vibrations may lead to 
infinitely high stress resonance conditions, which cause parts to 
catastrophically fail or may be unacceptable for customer stipulated 
reasons or perceptions. 
British Patent 1,016,914 describes a cylinder connected to the engine block 
and having pressurized lubrication oil supplied to both sides of a piston 
disposed in the cylinder and connected to the crankshaft to dampen axial 
vibrations. 
DISCLOSURE OF THE INVENTION 
In general, a combined axial and torsional crankshaft vibration damper for 
a reciprocating engine when made in accordance with this invention, 
comprises a hub portion fastened to the crankshaft and an inertia ring 
connected to the hub portion by a material causing the inertia ring to 
rotate at the present average speed of the crankshaft and absorb a portion 
of the axial and torsional vibrational movement of the crankshaft relative 
to the inertia ring. The inertia ring tries to continue constant 
rotational motion producing a resistance to the transmitted vibrational 
movement of the crankshaft transmitted to the inertia ring through the 
material. A portion of the resistance of the inertia ring is transmitted 
back to the crankshaft by the material dampening the axial and torsional 
vibrations of the crankshaft.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to the drawings in detail and in particular to FIG. 1, there 
is shown a combined axial and torsional crankshaft vibration damper 1 for 
a reciprocating engine (not shown) comprising a hub portion 3 connected to 
a crankshaft 5 and an inertia ring 7. The inertia ring 7 is connected to 
the hub portion 3 by a flat ring 9 made of an elastomer material, which is 
bonded to and compressed between the hub portion 3 and a thin metal ring 
11. Two spaced apart flat rings 13 made of the elastomer material are 
bonded to and compressed between the thin metal ring 11 and the inertia 
ring 7. The elastomer rings 9 and 13 provide sufficient flexibility 
between the inertia ring 7 and the hub 3 to allow the inertia ring to 
rotate at the present average speed of the crankshaft 5, which varies in 
speed within one single revolution. The elastomer rings 9 and 13 also 
absorb a portion of the axial and torsional vibratory movement of the 
crankshaft 5 relative to the inertia ring 7, which tries to maintain or 
continue constant rotational motion. Thus, the inertia ring 7 resists any 
motion changes transmitted via the elastomer rings 9 and 13 and moves to a 
lesser degree. The resistance of the inertia ring 7 is transmitted back to 
the crankshaft 5 by the elastomer rings 9 and 13 to dampen the axial and 
torsional vibrations of the crankshaft 5. Changing the thickness and 
formulation of the elastomer ring 9 affects torsional damping more than 
axial damping. While changing the thickness and formulation of the 
elastomer rings 13 affects axial damping more than torsional damping. The 
elastomer rings 9 and 13 are formulated to hold up when subjected to 
repeated shear stresses and may have different stiffness. 
Referring now to FIG. 2 in detail there is shown a hub 15 having an outer 
peripheral ring 17 with a rectangular cross section and an inertia ring 21 
having a plate 23 and 25 fastened on opposite sides thereof. The plates 23 
and 25 extend over the outer peripheral ring 17 with a space between the 
ring 17 the plates 23 and 25 and the inertia ring 21. Elastomer rings 27, 
29 and 31 are disposed on three sides of the outer peripheral ring 17, the 
plates 23 and 25 and the inertia ring 21. It is not required that the 
elastomer rings 27, 29 and 31 be bonded to the hub 15 or to the inertia 
ring 21. The elastomer rings 27, 29 and 31 are shown as separate, but it 
is understood that they may be made integral and have different 
formulation and thickness. The side elastomer rings 27 and 29 have a major 
affect on the degree of axial damping and the ring 31 has a major affect 
on torsional vibration. The elastomer rings 27, 29 and 31 cooperate with 
the hub 15 and inertia ring 21 to dampen axial and torsional crankshaft 
vibrations. 
Referring now to FIG. 3 there is shown a hub 3 having a inertia ring 33 
with a centrally disposed circumferential groove 35 disposed adjacent the 
hub 3. An elastomer ring 37 is disposed between the hub 3 and the inertia 
ring 33. The elastomer ring is bonded to and compressed between the hub 3 
and the inertia ring 33 outboard of the groove 35 and cooperates therewith 
to dampen axial and torsional crankshaft vibrations. The amount of axial 
and torsional vibration dampened may be varied by changing the width of 
the groove 35 and the thickness and formulation of the elastomer ring 37. 
Referring now to FIG. 4 in detail there is shown a hub 41 having a 
circumferential chamber 43 that receives an inertia ring 45. There is 
clearance between the inertia ring 45 and the chamber 43. A viscous fluid 
material 47 fills the clearance between the inertia ring 45 and the 
chamber 43. There is at least one hole 49 extending through the inertia 
ring 45. As the hub 41 rotates with the crankshaft 5 the viscous fluid 47 
shears, but transfers the rotating energy from the hub to the inertia ring 
45 which reaches the present average speed of the crankshaft 5. A portion 
of the axial and torsional movement of the crankshaft 5 relative to the 
inertia ring 45 is transmitted through the viscous fluid 47 to the inertia 
ring 45. The inertia ring tries to maintain constant rotational motion and 
resists the transmitted vibrational movement of the crankshaft 5. The 
resistance of the inertia ring 45 is transmitted back to the crankshaft 5 
through the viscous fluid 47 to dampen the axial and torsional vibration 
of the crankshaft 5. The viscosity of the fluid 47 and the clearance 
between the chamber 43 and the inertia ring 45 affect the degree of 
torsional damping. And the size and/or number of the holes and the 
viscosity of the viscous fluid 47 cooperate to control the period and 
magnitude of pressure differential between opposite sides of the inertia 
ring 45 and thereby control the degree axial damping. 
Referring now to FIG. 5 there is shown a hub 41 having a circumferential 
chamber 43 that receives an inertia ring 51. There is clearance between 
the inertia ring 51 and the chamber 43. A viscous fluid material 47 fills 
the clearance between the inertia ring 51 and the chamber 43. The inertia 
ring 51 comprises a plurality of disks 53 and 55 stacked one against 
another and fastened together. Outboard disks 53 are welded to inner and 
outer rings 57 and 59. The disks 53 and 55 have at least one through hole 
formed by aligning holes 61 and 63 in adjacent disks 53 and 55. The disks 
53 have a small hole 61 and are disposed adjacent the disks 55, which have 
a large hole 63 forming a labyrinth to control the period and magnitude of 
pressure differential between opposite sides of the inertia ring 51 and 
thereby control the degree of axial damping. 
Referring now to FIG. 6 there is shown a hub 41 having a circumferential 
chamber 43 that receives an inertia ring 65. There is clearance between 
the inertia ring 65 and the chamber 43. A viscous fluid material 47 fills 
the clearance between the inertia ring 65 and the chamber 43. The inertia 
ring 65 comprises a plurality of grooves 67 and 69 on radial inner and 
radial outer surfaces 71 and 73 of the inertia ring 65 forming a 
labyrinth. The labyrinths provide a high pressure differential between 
opposite sides of the inertia ring 65 with larger radial clearance between 
the chamber 43 and the inner and outer surfaces 71 and 73 of the inertia 
ring 65. 
INDUSTRIAL APPLICABILITY 
The combined axial and torsional vibration damper 1 for reciprocating 
engine has the hub 3, 15 or 41 connected to the crankshaft 5 and an 
inertia ring 7, 21, 33, 45, 51 or 65 connected to the hub 3, 15 or 41 by a 
material that transmits a portion of the vibratory movement of the 
crankshaft 5 to the inertia ring 7, 21, 33, 45, 51 or 65, which tends to 
continue constant rotational movement and resists the vibrational 
movement. This resistance is transmitted back to the hub 3, 7 or 41 
through the material to dampen the axial and torsional vibration of the 
crankshaft 5. 
The axial and torsional damper 1 can be made smaller, more durable and 
cheaper. It also provides improved serviceability and inspection of the 
axial and torsional vibration damper by placing it outside the engine 
block. 
While the preferred embodiments described herein set forth the best mode to 
practice this invention presently contemplated by the inventor, numerous 
modifications and adaptations of this invention will be apparent to others 
of ordinary skill in the art. Therefore, the embodiments are to be 
considered as illustrative and exemplary and it is understood that the 
claims are intended to cover such modifications and adaptations as they 
are considered to be within the spirit and scope of this invention.