U.S. patent application number 09/952165 was filed with the patent office on 2002-01-10 for vibration damper for the crankshaft of a piston engine.
This patent application is currently assigned to LuK Lamellen und Kupplungsbau GmbH. Invention is credited to Gerhardt, Friedrich, Haas, Wolfgang, Lehmann, Steffen, Reik, Wolfgang, Ruder, Willi, Schmitt, Ruben.
Application Number | 20020002960 09/952165 |
Document ID | / |
Family ID | 7841653 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020002960 |
Kind Code |
A1 |
Haas, Wolfgang ; et
al. |
January 10, 2002 |
Vibration damper for the crankshaft of a piston engine
Abstract
The crankshaft of a piston engine is assembled with a vibration
damper into a discrete module prior to mounting of such module in
axial and/or radial bearings of the housing of the engine. The
damper has an input element which rotates with the camshaft and a
mass which is angularly movable relative to the input element
against the resistance of coil springs. The input element can be
provided with a sleeve which surrounds a snout at one axial end of
the crankshaft. Alternatively, the damper can be installed in or on
or can constitute a cheek of the crankshaft. The coil springs can
operate in parallel with a friction generating device which also
opposes rotation of the input element and the mass of the damper
relative to each other.
Inventors: |
Haas, Wolfgang; (Achern,
DE) ; Schmitt, Ruben; (Buhl, DE) ; Gerhardt,
Friedrich; (Kehl-Leutesheim, DE) ; Reik,
Wolfgang; (Buhl, DE) ; Lehmann, Steffen;
(Ettlingen, DE) ; Ruder, Willi; (Lahr,
DE) |
Correspondence
Address: |
DARBY & DARBY P.C.
805 Third Avenue
New York
NY
10022
US
|
Assignee: |
LuK Lamellen und Kupplungsbau
GmbH
|
Family ID: |
7841653 |
Appl. No.: |
09/952165 |
Filed: |
September 12, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09952165 |
Sep 12, 2001 |
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09661422 |
Sep 13, 2000 |
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6308678 |
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09661422 |
Sep 13, 2000 |
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09146505 |
Sep 2, 1998 |
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6142115 |
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Current U.S.
Class: |
123/192.1 ;
123/192.2; 74/603 |
Current CPC
Class: |
F16F 15/28 20130101;
F02B 67/08 20130101; F16F 15/283 20130101; F16F 15/36 20130101;
Y10T 74/2128 20150115; F16F 15/264 20130101; F02B 75/06 20130101;
Y10T 74/2183 20150115; F16F 15/26 20130101; F16F 15/1421
20130101 |
Class at
Publication: |
123/192.1 ;
123/192.2; 74/603 |
International
Class: |
F02B 075/06 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 1997 |
DE |
197 39 374.8 |
Claims
1. A vibration damper for use in a piston engine having a housing
and a crankshaft, said crankshaft being rotatable in said housing
about an axis, said damper being arranged to be mounted on said
crankshaft in a position such that it is confined in said housing
upon mounting of said crankshaft in said housing, said damper
including an input element rotatable with said crankshaft about
said axis, at least one mass movable relative to said input
element, and at least one resilient energy storing element arranged
to oppose movements of said input element and said mass relative to
each other, the crankshaft including at least one portion extending
radially of said axis and is bounded by first surfaces, said input
element having a substantially U-shaped form surrounding said at
least one portion and including two legs forming second surfaces,
said second surfaces at least partially contacting said first
surfaces, the damper further including fastener means connecting
said input element to said at least one portion and form-locking
connections which are effective between said first and second
surfaces.
2. The damper of claim 1, wherein said form-locking connection is
configured to take up the centrifugal force acting on the vibration
damper so that the centrifugal force does not stress the fastener
means.
3. The damper of claim 1, wherein the second surfaces have portions
that are at least approximately at a right angle in relation to the
direction in which the legs are oriented.
4. The damper of claim 1, further comprising: at least one friction
generating device arranged to oppose at least certain stages of
movement of said at least one mass relative to said input element,
said at least one energy storing element being positioned to apply
to said at least one friction generating device a force which
entails the generation of a frictional damping action at least when
said at least one mass is caused to move relative to said input
element.
5. The damper of claim 1, wherein said input element and said at
least one mass are movable relative to each other and said
resilient means is interposed between said input element and said
at least one mass to oppose rotation of said input element and said
at least one mass relative to each other.
6. The damper of claim 1, wherein said resilient energy storing
element comprises at least one coil spring.
7. The damper of claim 1, further comprising at least one friction
generating device arranged to oppose at least certain stages of
rotation of said input element and said at least one mass relative
to each other.
8. The damper of claim 1, wherein said crankshaft comprises at
least one cheek, said vibration damper being adjacent said at least
one cheek as seen in the direction of said axis.
9. The damper of claim 1, wherein said at least one mass is a
rotary inertia-enhancing mass, said input element and said at least
one mass being rotatable relative to each other and said damping
means further comprising at least one friction generating device
arranged to oppose rotation of said input element and said at least
one mass relative to each other.
10. The damper of claim 1, wherein said crankshaft has at least one
cheek and said damping means is provided on said at least one
cheek.
11. The damper of claim 1, wherein said crankshaft includes a
portion which is rotatable about a predetermined axis and said
damping means is a ring concentric with said portion of said
crankshaft.
12. The damper of claim 11, wherein said portion of said crankshaft
is a snout.
13. The damper of claim 1, wherein said crankshaft comprises at
least one cheek, said housing including a wall spaced apart from
said at least one cheek in the direction of said axis and said
damping means being disposed between said wall and said at least
one cheek.
14. The damper of claim 1 3, wherein said crankshaft further
comprises a portion which is rotatably mounted in said wall.
15. The damper of claim 1, wherein said crankshaft comprises a
snout, said damping means being mounted on said snout.
16. The damper of claim 1, wherein said input element is affixed to
said crankshaft.
17. The damper of claim 1, wherein the input element is arranged to
receive torque from said crankshaft, and further comprising means
for limiting the magnitude of torque which the crankshaft can
transmit to said input element.
18. The damper of claim 17, wherein said means for limiting the
magnitude of torque comprises a slip clutch.
19. The damper of claim 1, wherein the input element is a rotary
annular element having first and second sides and the at least one
mass is a rotary mass adjacent at least one of the sides as seen in
the direction of said axis, said mass and said input element being
rotatable relative to each other about said axis and said at least
one energy storing element being arranged to yieldably oppose
rotation of said input element and said mass relative to each
other, said at least one friction generating device operating
between said input element and said mass.
20. The damper of claim 1 9, wherein said at least one friction
generating device is arranged to operate in parallel with said at
least one energy storing element.
21. The damper of claim 1, wherein the at least one mass is a
composite mass and the input element is an annular input element
flanked at least in part by two portions of said composite mass,
said portions of said mass being rotatable relative to said input
element and being spaced apart from each other in the direction of
said axis, said at least one resilient energy storing element being
disposed in windows provided therefor in said input element and in
at least one of said portions of said mass to oppose rotation of
said input element and said at least one portion of said mass
relative to each other.
22. The damper of claim 21, further comprising: means for
non-rotatably connecting said portions of said mass to each
other.
23. The damper of claim 21, wherein said at least one energy
storing element comprises a coil spring and said at least one
portion of said mass has an annular shape.
24. The damper of claim 21, wherein said at least one friction
generating device is arranged to oppose rotation of said mass and
said input element relative to each other.
25. The damper of claim 24, wherein said at least one friction
generating device comprises at least one energy storing member
reacting against one of said input element and said mass and
bearing against the other of said input element and said mass.
26. The damper of claim 1, wherein said crankshaft includes an end
portion and said input element has a tubular extension arranged to
at least partially surround said end portion of said
crankshaft.
27. The damper of claim 26, wherein said at least one resilient
energy storing element is disposed at a first radial distance from
said axis and said extension is disposed at a second radial
distance from said axis less than said first radial distance.
28. The damper of claim 26, wherein said extension of said input
element and said end portion of said crankshaft cooperate to
provide a thrust bearing for said crankshaft.
29. A vibration damper for use in a piston engine having a housing
and a crankshaft, said crankshaft being rotatable in said housing
about an axis, said damper being arranged to be mounted on said
crankshaft in a position such that it is confined in said housing
upon mounting of said crankshaft in said housing, said damper
including an input element rotatable with said crankshaft about
said axis, at least one mass movable relative to said input
element, and at least one resilient energy storing element arranged
to oppose movements of said input element and said at least one
mass to each other, the crankshaft including at least one portion
extending radially of said axis and flanked by two surfaces, said
input element having a substantially U-shaped form surrounding said
at least one portion and including two legs at least partially
contacting said two surfaces, the damper further including fastener
means connecting said input element to said at least one portion
and form-locking connections which are effective between said legs
and said at least one portion.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to improvements in piston engines
(also known as reciprocating or displacement engines), and more
particularly to improvements in methods of and means for preventing
or reducing the extent and/or frequency of stray movements of
crankshafts in such engines. Still more particularly, the invention
relates to improvements in the construction and mounting of
vibration dampers for the crankshafts of piston engines.
[0002] Published German patent application Ser. No. 195 19 261
discloses a torsional vibration damper which comprises an annular
casing adapted to be connected to the shaft of a machine and
confining a flywheel which is rotatable relative to the casing
against the opposition of a body of viscous fluid. This published
application proposes to position the casing of the vibration damper
at the front end face of, and to fasten the casing to, the front
end (snout) of the crankshaft. A drawback of such proposal is that
the thus attached damper occupies a substantial amount of space
which is not always available under the hoods of certain types of
motor vehicles (such as compact cars), especially if the engine is
installed transversely of the direction of forward movement of the
conveyance.
[0003] Published German patent application Ser. No. 40 25 848
discloses a modified vibration damper which is intended for use in
piston engines and employs annular flywheels as well as a hub which
is to be secured to the crankshaft of the engine. The annular
flywheels are movably secured to the hub by buffers of rubber or
other suitable elastomeric material. The hub is provided with or
carries a pulley for one or more endless belts serving to transmit
motion to the camshaft of the engine and/or to one or more
auxiliary aggregates of the motor vehicle.
[0004] One of the purposes of vibration dampers for the crankshafts
of piston engines is to suppress the characteristic frequencies
(harmonic vibrations) of the crankshafts. In many instances, the
characteristic frequency of the crankshaft in the housing of a
piston engine is in the range of between 300 and 450 Hz. Such
frequency is induced primarily as a result of iregularities
attributable to compression and expansion that take place in the
cylinders for the pistons of the engine. Vibrations at the
torsional resonancy can result in breakage of the crankshaft, and
this is the reason that the crankshafts of piston engines are
normally equipped with vibration dampers (e.g., in the form of
heavy, rubber-mounted wheels in front of the crankshaft) to counter
harmonic vibrations.
[0005] In order to achieve a satisfactory vibration damping action,
the vibration damping frequency must be selected with a rather high
degree of accuracy. As already mentioned above, presently known
attempts at adequate damping of vibrations of a crankshaft in a
piston engine include the provision of at least one annular
flywheel which is movably connected to a hub or another input
element of the vibration damper by a buffer of rubber (or other
energy-storing elastomeric material), or by a body of oil or
another suitable viscous fluid.
[0006] In addition to their often excessive space requirements, the
aforediscussed presently known vibration dampers for the
crankshafts of piston engines exhibit the drawback that the
viscosity of fluid can be greatly influenced by changes of
temperature and that such temperature changes can also exert an
undue influence upon the spring gradient of the elastomeric
material. It is to be borne in mind that a vibration damper for the
crankshaft of a piston engine is installed in immediate or very
close proximity to one or more sources of pronounced heat. Attempts
to overcome or to reduce the undesirable influence of elevated
temperatures upon the predictability and reliability of operation
of conventional vibration dampers for crankshafts include the
utilization of oversized vibration damping masses to thus widen the
frequency range within which the damper is or should be effective.
However, the utilization of oversized masses brings about other
serious problems and drawbacks such as a greatly increased fuel
consumption and an increased resistance of rotary components of the
piston engine to the setting in rotary motion.
OBJECTS OF THE INVENTION
[0007] An object of the invention is to provide a vibration damper
which can be utilized with the crankshaft of a piston engine and is
less affected by temperature changes and/or elevated temperatures
than heretofore known vibration dampers for crankshafts.
[0008] Another object of the invention is to provide a vibration
damper which can stand pronounced thermal stresses for exended
periods of time.
[0009] A further object of the invention is to provide a vibration
damper which is constructed and assembled and which can be
installed in a piston engine in such a way that it can effectively
counter harmonic vibrations of a crankshaft during each stage of
operation of the piston engine.
[0010] An additional object of the invention is to provide a novel
and improved crankshaft-vibration damper combination which is not
affected, or not appreciably affected, by pronounced temperature
changes and which can be utilized in lieu of and as a superior
substitute for conventional crankshaft-vibration damper
combinations.
[0011] Still another object of the invention is to provide a novel
and improved method of assembling a piston engine wherein the
crankshaft is prevented from carrying out any, or from carrying out
excessive, harmonic vibrations.
[0012] A further object of the invention is to provide a novel and
improved module which embodies a-crankshaft and can be utilized in
piston engines as a superior substitute for conventional
crankshaft-vibration damper combinations.
[0013] Another object of the invention is to design a vibration
damper for the crankshaft of a piston engine in such a way that the
range of thermal influence upon the frequency range in which the
vibration damper is effective is much narrower than in connection
with the utilization of conventional vibration dampers for the
crankshafts of piston engines.
[0014] An additional object of the invention is to provide a
simple, compact and inexpensive but highly effective vibration
damper which can be put to use in all or nearly all types of piston
engines to oppose stray movements of the crankshaft.
[0015] Still another object of the invention is to provide a damper
which can be readily installed in the housing of a piston
engine.
[0016] A further object of the invention is to provide a piston
engine which embodies one or more dampers of the above outlined
character.
[0017] Another object of the invention is to provide a piston
engine with a novel and improved housing for the crankshaft and for
a damper which serves to counter-harmonic vibrations of the
crankshaft.
[0018] An additional object of the invention is to provide a motor
vehicle embodying a piston engine which utilizes the above outlined
crankshaft-vibration damper combination.
[0019] Still another object of the invention is to provide a piston
engine wherein the vibration damper for the crankshaft need not be
provided with a discrete lubricating system.
SUMMARY OF THE INVENTION
[0020] One feature of the present invention resides in the
provision of a piston engine which comprises a housing, a
crankshaft which is rotatably journalled in the housing, and means
for damping vibrations of the housing and the crankshaft relative
to each other. The damping means is at least partially confined in
the housing and is provided on the crankshaft.
[0021] In accordance with a presently preferred embodiment, the
damping means is fully or practically fully confined in the housing
of the piston engine.
[0022] A presently preferred embodiment of the damping means
comprises a rotary input element and at least one rotary
inertia-enhancing mass. The input element and the at least one mass
are rotatable relative to each other, and the damping means further
comprises energy storing resilient means interposed between the
input element and the at least one mass to oppose rotation of the
input element and the at least one mass relative to each other. The
energy storing resilient means can comprise one or more coil
springs, and the piston engine can further comprise at least one
friction generating device which is installed to oppose at least
certain stages of rotation of the input element and the at least
one mass relative to each other.
[0023] It is possible to utilize the friction generating device(s)
in lieu of the energy storing resilient element or elements.
[0024] The damping means can be mounted on or in or adjacent a
cheek or web of the crankshaft. For example, the damping means can
be located adjacent a cheek as seen in the axial direction of the
crankshaft.
[0025] The damping means can include or constitute a ring which is
concentric with a portion of the crankshaft, for example, with an
end portion referred to as snout.
[0026] A cheek of the crankshaft can be positioned adjacent to but
still spaced apart from a wall of the housing (as seen in the axial
direction of the crankshaft), and the damping means can be disposed
in the housing between such cheek and the wall. The crankshaft can
comprise a portion (such as the aforementioned snout) which is
rotatably mounted in the wall.
[0027] The aforementioned input element of the damping means is
rotatable with the crankshaft; the input element can be fixed to
the shaft by a suitable form-locking connection or permanently,
e.g., by welding.
[0028] The damping means or the piston engine can further comprise
means for limiting the magnitude of torque which the crankshaft can
transmit to the input element of the damping means. For example,
the torque limiting means can comprise one or more slip
clutches.
[0029] The input element of the damping means can constitute a
rotary annular body and the mass of the damping means can be
designed and mounted in such a way that it is adjacent at least one
side of the annular input element (as seen in the axial direction
of the crankshaft). The mass and the input element are rotatable
relative to each other against the opposition of the aforementioned
resilient energy storing element or elements. If provided, a
friction generating device can be installed to operate between the
input element and the mass; such friction generating device can
operate in parallel with the energy storing element(s).
[0030] If the mass comprises several discrete portions, e.g., two
discrete portions, such discrete portions can be located at
opposite sides of the annular input element of the damping means
and can be spaced apart from each other in the axial direction of
the crankshaft. Each energy storing element of the damping means is
preferably installed in windows which are provided therefor in the
input element and in at least one portion of the mass to oppose
rotation of the input element and the at least one portion of the
mass relative to each other. Such damping means preferably further
comprises means (e.g., rivets) for non-rotatably connecting the
portions of the mass to each other. As already mentioned
hereinbefore, it is presently preferred to employ energy storing
resilient elements in the form of coil springs, and each portion of
the mass can but need not have an annular shape. If the just
described embodiment of the damping means employs at least one
friction generating device which serves to oppose rotation of the
mass and the input element relative to each other (e.g., in
parallel with the coil spring or springs), the friction generating
device can comprise at least one energy storing member (e.g., a
diaphragm spring or a corrugated washer-like spring) which reacts
against the mass or against the input element and bears upon the
input element or the mass.
[0031] The input element of the damping means can be provided with
a tubular extension which surrounds an end portion of the
crankshaft, such as the aforementioned snout. The extension is
preferably located radially inwardly of the resilient energy
storing element or elements of the damping means. It is possible to
design the extension in such a way that it constitutes an axial
and/or a radial bearing for the end portion of the crankshaft in
the housing.
[0032] Another feature of the invention resides in the provision of
a vibration damper which can be utilized in a piston engine having
a housing and a crankshaft which is rotatable relative to the
housing by one or more connecting rods receiving motion from
pistons, and which serves to transmit torque to (or which
constitutes) the rotary output element of the engine, e.g., an
output element which can transmit torque to a friction clutch in
the power train of a motor vehicle. The crankshaft and the
vibration damper constitute a module which is ready to be rotatably
mounted in the housing of the piston engine.
[0033] The damper can be designed in such a way that it includes a
portion which surrounds an end portion of the crankshaft.
[0034] The input and output elements of the vibration damper
forming part of the module can be immediately adjacent a cheek or
web of the crankshaft.
[0035] Alternatively, a cheek of the crankshaft can be constituted
(either entirely or in part) by the vibration damper of the
module.
[0036] The damper can constitute an annular or a substantially
U-shaped (such as horseshoe-shaped) structure.
[0037] The crankshaft can be designed in such a way that it
includes a cheek and an oval or substantially oval portion adjacent
the cheek. Such oval portion can extend radially of the rotational
axis of the crankshaft and it can be flanked by two surfaces which
are at least substantially normal to such axis. The damper has a
substantially U-shaped outline, it surrounds the oval portion, and
includes two legs which at least partially abut the cheek. Fastener
means (e.g., bolts or screws) is provided to reliably connect the
legs of the damper to the cheek; alternatively, the damper can be
permanently affixed (e.g., welded) to the cheek.
[0038] A further feature of the invention resides in the provision
of a method of assembling a piston engine wherein a crankshaft is
rotatable in a housing and has a tendency to perform at times
harmonic vibrations in actual use of the engine. The method
comprises the steps of assembling the crankshaft and at least one
vibration damper into a module, and thereupon rotatably mounting
the crankshaft of the thus obtained module in the housing.
[0039] The assembling step can include incorporating the at least
one vibration damper into a cheek of the crankshaft.
[0040] The assembling step can also include combining the
crankshaft with a plurality of identical or different vibration
dampers.
[0041] The novel features which are considered as characteristic of
the invention are set forth in particular in the appended claims.
The improved vibration damper itself, however, both as to its
construction and the modes of assembling, installing and utilizing
the same, together with numerous additional important and
advantageous features and attributes thereof, will be best
understood upon perusal of the following detailed description of
certain presently preferred specific embodiments with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] FIG. 1 is a fragmentary partly elevational and partly axial
sectional view of the housing and the crankshaft of a piston engine
wherein the harmonic vibrations of the crankshaft can be opposed by
a damper which embodies one form of the present invention;
[0043] FIG. 2 is a transverse sectional view substantially as seen
in the direction of arrows from the line II-II in FIG. 1;
[0044] FIG. 3 is a fragmentary partly elevational and partly axial
sectional view similar to that shown in FIG. 1 but depicting a
modified crankshaft and a modified vibration damper for the
crankshaft;
[0045] FIG. 4 is a fragmentary partly elevational and partly
sectional view of a piston engine embodying a different
crankshaft-vibration damper combination, with the damper attached
to and partially surrounding one cheek of the crankshaft;
[0046] FIG. 5 is a transverse sectional view substantially as seen
in the direction of arrows from the line V-V in FIG. 4;
[0047] FIG. 5a is a fragmentary transverse sectional view showing a
modification of the crankshaft-damper combination which is
illustrated in FIGS. 4 and 5;
[0048] FIG. 6 is a view similar to that of FIG. 4 but showing a
different combination of a cheek and a vibration damper;
[0049] FIG. 7 is a transverse sectional view substantially as seen
in the direction of arrows from the line VII-VII of FIG. 6;
[0050] FIG. 8 is an enlarged view of a detail of the structure
which is shown in FIG. 6;
[0051] FIG. 9 is a fragmentary transverse sectional view of a
crakshaft-damper combination which constitutes a first modification
of the structure shown in FIGS. 6 to 8; and
[0052] FIG. 10 is a similar fragmentary transverse sectional view
of a second modification of the crankshaft-damper combination shown
in FIGS. 6 to 8.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0053] FIGS. 1 and 2 show certain details of a prime mover 1 which
is an internal combustion engine, and more specifically a piston
engine (also called reciprocating or displacement engine and
hereinafter called engine or piston engine) adapted to be put to
use in the power train of a motor vehicle. As a rule, the output
member (namely the rotary crankshaft 3 of the engine 1 shown in
FIGS. 1 and 2) transmits torque to the input element (not shown) of
a torque transmitting system (such a driver-operated or automated
or automatic clutch) which, in turn, transmits torque to the input
element of a manually or automatically shiftable change-speed
transmission. Reference may be had, for example, to commonly owned
U.S. Pat. No. 5,374,218 granted Dec. 20, 1993 to Wolfgang Reik et
al. for "APPARATUS FOR COMPENSATION OF FLUCTUATIONS OF TORQUE"
which shows (only schematically) a combustion engine and a
transmission as well as the details of a friction clutch which
transmits torque from the rotary output element of the engine to
the rotary input element of the transmission.
[0054] The crankshaft 3 is rotatably journalled in a housing 2 of
the engine 1 and comprises one or more crankpins 4 (only one shown
in FIG. 1). In a manner well known from the art of piston engines,
each crankpin is orbited about the axis 8A of the crankshaft 3 by a
discrete connecting rod which is connected to a reciprocable piston
of the engine. As concerns the construction and mode of operation
of piston engines, reference may be had, for example, to pages
80-87 of the German-language "Taschenbuch fur den Maschinenbau"
(18th Edition) by Dubbel and/or to pages 382-399 of the
German-language "Kraftfahrtechnisches Taschenbuch" (22nd Edition)
published by Bosch and/or to "Modern Automotive Technology" by
James E. Duffy (1994 Edition, published by The Goodheart-Willcox
Company, Inc., Tinley Park, Ill.).
[0055] The disclosures of all patents and other publications, as
well as of all patent applications (including the parent German
patent application Ser. No. 197 39 374.8 filed Sep. 9, 1997)) which
are identified in this specification are incorporated herein by
reference.
[0056] The crankpin 4 which is shown in FIG. 1 is flanked by two
cheeks 5. The right-hand cheek 5 transmits rotary motion to a
bearing journal 7 (e.g., a main bearing journal at one axial end of
the crankshaft 3) which is rotatable in a sleeve-like radial
bearing 9 mounted in the housing 2. The left-hand cheek 5 of FIG. 1
is of one piece with or is connected to the front end (also called
snout) 6 of the crankshaft 3, and this snout is indirectly mounted
in a sleeve-like radial bearing 8 which, in turn, is installed in a
radially extending wall 19 of the housing 2. The axes of the
bearings 8, 9 coincide with the axis 8A of the crankshaft 3.
[0057] It is clear that the illustrated bearing 8 and/or 9 can be
replaced with an antifriction roller bearing having an inner race,
an outer race and at least one annulus of spherical and/or other
rolling elements between the two races. Furthermore, if the
crankshaft 3 comprises two or more crankpins 4, it comprises two or
more bearing journals (corresponding to the journal 7) and at least
one additional journal can be mounted in the housing 2 by way of a
sleeve bearing or another suitable friction reducing bearing. For
example, the bearing journals which are separated from each other
by sets of two or three crankpins can be rotatably mounted in the
housing of the piston engine.
[0058] The housing 2 contains a vibration damper 10 which comprises
an input element 11 rigidly (non-rotatably) affixed to the snout 6
by a threaded fastener 12. The illustrated fastener 12 is a bolt
having an externally threaded shank received in a tapped bore 13 of
the snout 6 in such a way that the axis of the properly inserted
fastener coincides with the axis 8A of the crankshaft 3. However,
the input element 11 can be non-rotatably secured to the crankshaft
3 in a number of other ways. For example, it is possible to resort
to a form-locking connection including a profiled portion of the
input element 11 which is caused to receive or surround a
complementary profiled portion of the crankshaft. Alternatively,
the input element 11 (or an equivalent input element) can be pinned
or bonded to the crankshaft. The bonding operation can involve
pressure welding, resistance pressure welding, resistance fusion
welding, radiation welding, inert gas arc welding or fusion
welding. Reference may be had to pages G4-G7 of the aforementioned
German-language publication "Taschenbuch fur den Maschinenbau"
(18th Edition) by Dubbel.
[0059] The input element 11 of the damper 10 which is shown in
FIGS. 1 and 2 comprises an annular (washer-like) radially outer
portion 14 which is flanked by and indirectly supports two
ring-shaped portions 16, 17 of a flywheel or mass 15. The radially
outer portion of the left-hand cheek 5 of FIG. 1 is configurated in
such a way that it provides room for confinement of the radially
outer portion 14 of the input element 11 and of the portions 16, 17
of the mass 15 between this cheek and the radial wall 19 of the
housing 2. More specifically, the left-hand cheek 5 of FIG. 5 is
configurated to provide room for the adjacent portion 17 of the
mass 15.
[0060] The portion 14 of the input element 11 and the portions 16,
17 of the mass 15 are provided with at least partially registering
windows 14a, 16a, 17a which extend in the circumferential direction
of the mass 15 5 (see FIG. 2), and each such set of at least
partially registering windows receives portions of a discrete
energy storing element 18 in the form of a coil spring, preferably
a steel spring. The springs 18 oppose rotation of the input element
11 and the mass 15 relative to each other.
[0061] The input element 11 serves as a means for centering the
entire damper 10 on the snout 6 of the crankshaft 3, at least in a
direction as seen radially of the axis 8A. To this end, the
radially inner portion of the input element 11 comprises a
sleeve-like tubular extension 20 which surrounds the snout 6
radially inwardly of the annular portion 11 and forms part of a
cupped member 21 further including an end wall 22 abutting the
adjacent end face 23 of the snout 6 under the action of the head of
the fastener 12. It is preferred to configurate the extension 20 in
such a way that it snugly receives the snout 6.
[0062] The tubular extension 20 is directly surrounded by the
sleeve-like radial bearing 8 which is mounted in the wall 19 of the
housing 2. The bearing 8 can rotate with the extension 20 relative
to the wall 19, or the extension 20 can rotate relative to the
bearing 8. At least one of the bearings 8, 9 can be designed as a
combined radial and thrust bearing to hold the crankshaft 3 and the
damper 10 against axial movement relative to the housing 2.
[0063] FIG. 1 shows that the damper 10 is mounted at the free end
(snout 6) of the crankshaft 3, i.e., at the end which is remote
from the torque transmitting end of the crankshaft. Such torque
tranmitting end (constituted by the bearing journal 7 or a bearing
journal (not shown) to the right of the journal 7) constitutes the
rotary output element of the engine 1 and can transmit torque to
the input element (such as a flywheel) of the afore-mntioned torque
transmitting system (e.g., a friction clutch) which, in turn is
engageable or disengageable to transmit, or to interrupt the
transmission of, torque to the input element of a change-speed
transmission in the power train of a motor vehicle. Reference may
be had again to U.S. Pat. No. 5,374,218 to Reik et al.
[0064] The damper 10 (or an equivalent damper) can be installed in
the housing 2 to the right of the right-hand cheek 5 shown in FIG.
1 or at the very output end of the crankshaft 3. It is also
possible to install one or more dampers in the housing of a piston
engine adjacent an intermediate portion of the crankshaft. Still
further, and particularly if the crankshaft is a so-called
composite crankshaft, the housing of the engine can confine two or
more dampers, e.g., two dampers adjacent different pairs of cheeks
of the composite crankshaft.
[0065] The bearing 8, the cupped portion 21 of the input element 11
and the fastener 12 are sealed from the surrounding atmosphere by a
cover or closure 24 having a radially extending outer portion which
is sealingly secured to the outer side of the wall 19. FIG. 1 shows
that the closure 24 is bonded to the wall 19. However, it is also
possible to secure the closure 24 to the housing 2 by means of
suitable fasteners (screws, bolts or the like, not shown); it is
then advisable to install a washer or another suitable sealing
element between the housing 2 and the closure 24 (or another
reliable closure). The closure 24 prevents the escape of lubricant
for the crankshaft 3 and the damper 10 from the housing 2.
[0066] The housing 2 further confines a hysteresis or frictional
damping device 25 which operates in parallel with the coil springs
18 of the damper 10. The damping device 25 which is shown in FIG. 1
comprises an energy storing member 26, such as a diaphragm spring,
which is installed in prestressed condition to react against the
annular portion 14 of the input member 11 radially inwardly of the
coil springs 18, and to act (in the direction of the axis 8A)
against the adjacent side of the portion 16 of the two-piece mass
15.
[0067] The portions 16, 17 of the mass 15 are fixedly secured to
each other by distancing elements in the form of rivets 27 which
alternate with pairs of coil springs 18 (as seen in the
circumferential direction of the damper 10) and extend (preferably
with a predetermined clearance) through openings 28 of the annular
portion 14 of the input element 11. The rivets 27 ensure that the
diaphragm spring 26 of the damping device 25 can urge the left-hand
side (as viewed in FIG. 1) of the portion 17 of the mass 15 against
the right-hand side of the annular portion 11. In other words, the
rivets 27 ensure that, since the portion 16 is in indirect
frictional engagement with the annular portion 14 by way of the
diaphragm spring 26, the portion 17 is in direct frictional
engagement with the portion 14.
[0068] The rivets 27 and the surfaces bounding the respective
openings 28 in the portion 14 of the input element 11 further serve
as a means for limiting the extent of angular movability of the
input element 11 and the mass 15 relative to each other. Of course,
it is equally possible to rely on other modes of limiting the
extent of angular movement of the parts 11 and 15 of the damper 10
relative to each other (in addition to or in lieu of accurate
dimensioning of the openings 28 for the shanks of the rivets 27).
For example, the angular movability of the parts 11, 15 relative to
each other can be limited by the coil springs 18; such angular
movability is terminated when the neighboring convolutions of the
coil springs 18 are caused to abut each other, i.e., when the coil
springs begin to act as solid blocks or bodies (as seen in the
circumferential direction of the damper 10).
[0069] The axial dimensions of the piston engine 1 can be reduced
by replacing the illustrated threaded fastener 12 with one or more
countersunk screws (not shown).
[0070] Furthermore, a discrete radial bearing 8 can be omitted by
providing the external surface of the extension 20 of the input
element 11 with one or more coats of a suitable wear-resistant
friction reducing material. It is also advisable to harden the
extension 20, either in its entirety or at least along its external
surface. For example, one can resort to an inductive or radiation
hardening procedure.
[0071] The parts 11, 16 and 17 of the damper 10 which is shown in
FIG. 1 are made of a suitable metallic sheet material. An advantage
of such construction is that the entire damper occupies a minimal
amount of space as seen in the direction of the axis 8A and can be
readily confined between the left-hand cheek 5 of FIG. 1 and the
wall 19 of the housing 2. The making of the parts 11, 16 and 17 of
a metallic sheet material contributes to simplicity of manufacture
and lower cost of the damper 10 as well as to lower cost of the
entire piston engine.
[0072] The basic function of the damper 10 is carried out by the
mass 15 in conjunction with the coil springs 18. These springs can
be installed in a partially stressed condition. It has been found
that the damper 10 operates quite satisfactorily if the springs 18
are prestressed to an extent corresponding to about 50% of the
maxium possible stress. However, the initial stress can be more or
less than 50%. Another advantage of initial stressing of the
springs 18 is that the mass 15 is not likely to oscillate relative
to the input element 11 of the damper 10, i.e., that, under normal
circumstances, there is no play or no undue play between the input
element 11 and the portions 16, 17 of the mass 15.
[0073] The initial stressing of the coil springs 18 and the
dimensions of the windows 14a, 16a, 17a can be selected in such a
way that the damper 10 can carry out its function in several
successive stages. This can be readily accomplished by selecting
the dimensions of the windows and the initial stressing of the
springs 18 in such a way that a first set of springs begins to
offer a resistance to angular displacement of the input element 11
and mass 15 right from the start, and that at least one further set
of springs 18 begins to offer a resistance to such angular
displacements after the input element 11 and the mass 15 have
already completed a certain initial angular movement relative to
each other. The number of stages can be one, two or more than
two.
[0074] It is further possible to select the energy which is stored
by the springs 18 and the mass 15 in such a way that the damping
frequency corresponds or is properly related to the characteristic
frequency of the crankshaft 3.
[0075] The frictional damping device 25 can be used jointly with or
in lieu of or can be replaced by a velocity-dependent or
velocity-proportional damping by means of oil or another viscous
fluid in one or more gaps between parts which are caused to move
relative to each other. For example, a velocity-proportional
damping action can be arrived at by selecting a correspondingly
narrow or wide gap or clearance between at least one of the annular
portions 16, 17 of the mass 15 and the annular radially outer
portion 14 of the input element 11.
[0076] An important advantage of the feature that the damper 10 is
installed in the housing 2 of the engine 1 is that the lubricating
system for the crankshaft and/or certain other parts of the engine
can also serve as a means for lubricating the damper 10 as well as
to establish the aforediscussed velocity-dependent damping through
one or more properly dimensioned gaps between the input element 11
and the mass 15 of the damper 10. Still further, such lubricant can
serve as a means for withdrawing heat from the parts of the damper
10.
[0077] Adequate lubrication of and withdrawal of heat from the
constituents of the damper 10 is highly importaant because this
entails a much less pronounced wear upon the neighboring parts
which are in contact with and move relative to each other and hence
a longer useful life of the entire piston engine.
[0078] An advantage of coil springs (18) which consist of steel
(rather than another metallic or a plastic material) is that the
spring characteristics of such energy storing elements are not
affected, or not overly affected, by pronounced temperature
changes. This, in turn, brings about the important advantage that
the damper frequency and/or the range of damper frequencies can be
selected with a high degree of accuracy and remains at least
substantially unchanged in actual use of the piston engine.
Therefore, it is possible to employ a relatively small damper
having a relatively small mass, i.e., the improved damper 10 is
surprisingly compact. Moreover, such damper can reladily stand
elevated temperaturs (such as up to 130.degree. C.) which develop
or are likely to develop in actual use of the engine 1.
[0079] FIG. 3 illustrates a portion of a second piston engine
wherein the length of the housing 102 (as seen in the axial
direction of the crankshaft 103) is less than the length of the
housing 2 in the piston engine 1 of FIGS. 1 and 2. One of the
reasons is that the input element 111 of the vibration damper 110
which is shown in FIG. 3 is assembled of two separately produced
parts, namely a washer-like annular radially outer portion 111 and
a centrally located cylindrical sleeve-like part 120. The latter is
welded (as at 121) to the radially innermost part of the annular
portion 114 to constitute a functional equivalent of the extension
20 of the input element 11 in the damper 10 of FIGS. 1 and 2. The
part 120 can be said to constitute a radial bearing which surrounds
the snout 106 of the crankshaft 103 and extends into a blind bore
or recess 102a in the radially extending wall 119 of the housing
102.
[0080] The connection 121 between the parts 114 and 120 of the
input element 111 of the damper 110 is preferably established by
laser beam welding. However, it also possible to resort to any
other of the aforementioned welding techniques.
[0081] An important advantage of the method of assembling the input
element 111 of two separately produced parts 114, 120 is that the
internal and/or external surface of the cylindrical part 120 can be
readily finished with a desirable high degree of precision (e.g.,
at the exterior of the part 120 to thus obtain a highly
satisfactory radial bearing 108). The cylindrical part 120 can be a
press fit on the snout 106 of the crankshaft 103 and a precise
sliding fit in the blind bore 102a of the wall 119. For example,
the part 120 can be shrunk onto the snout 106. However, it is
equally within the purview of the invention to non-rotatably secure
the cylindrical part 120 to the snout 106 in any other suitable
way, e.g., in accordance with any one of the procedures already
described in connection with the mounting of the extension 20 on
the snout 6 of the crankshaft 3 shown in FIGS. 1 and 2. By way of
example only, at least the internal surface of the cylindrical part
120 can be facetted and can non-rotatably surround a facetted
complementary external surface of the snout 106.
[0082] It is also possible to provide a radial bearing 108 which
incudes one or more layers of friction reducing wear-resistant
material applied to the external surface of the part 120 and/or to
the surface surrounding the blind bore 102a. Still further, it is
possible to employ a separately produced sleeve-like radial bearing
(corresponding to the sleeve 8) which is inserted between the part
120 and the surrounding portion of the wall 102. Still further, it
is possible to select the diameter of the blind bore 102a in such a
way that the internal surface surrounding such bore and the
external surface of the part 120 provide room for a radial or
combined radial and axial antifriction bearing with inner and outer
races and one or more annuli of spherical and/or other rolling
elements between the two races.
[0083] Another advantage of the embodiment a portion of which is
illustrated in FIG. 3 is that the closure or cover 24 of FIG. 1 can
be dispensed with. This entails savings in material and labor and
contributes to compactness of the piston engine (as seen in the
axial direction of the crankshaft 103).
[0084] Each of the housings 2 and 102 can be assembled of two or
more separately produced parts. For example, the housing 2 of the
piston engine 1 can be assembled of at least two separately
produced parts which are fixedly and sealingly secured to each
other in the region of the crankpin 4.
[0085] The mode of operation of the damper 210 which is shown in
FIGS. 4 and-5 is determined by a pair of arcuate masses 215 in
conjunction with pairs of compression springs 218 each of which is
shown as constituting a relatively short coil spring. The masses
215 and the associated pairs of coil springs 218 are confined in an
arcuate housing or casing 230. The casing 230 of the damper 210
which is shown in FIGS. 4 and 5 is a one-piece metallic body having
two arcuate chambers 231 each of which movably receives one of the
masses 215 and the corresponding pair of coil springs 218. The
chambers 231 are open at both axial ends of the casing 230 (see
FIG. 4) and their centers of curvature are preferably located on
the axis of the crankshaft 203 which is rotatably journalled in the
housing (not shown) of the piston engine embodying the crankshaft
203 and the vibration damper 210.
[0086] The illustrated masses 215 are relatively thick (as measured
in the axial direction of the crankshaft 203) and can be made of a
sintered metallic material. When the crankshaft 203 rotates (i.e.,
when the piston engine is on), the masses 215 tend to move radially
outwardly under the action of centrifugal force and to frictionally
engage the concave internal surfaces of the arcuate walls 232
forming part of the casing 230 and bounding the radially outermost
portions of the respective arcuate chambers 231. The extent of
frictional engagement (and more specifically the magnitude of the
frictional force which develops between any one of the masses 215
and the respective wall 232 is a function of the RPM of the
crankshaft 203 (i.e., of the damper 210).
[0087] The magnitude of the just mentioned force is further
dependent upon the prestressing and actual stressing of the pairs
of coil springs 218 which react against radially extending portions
of the casing 230 and bear against the end portions of the
respective masses 215 (this can be readily seen in FIG. 5). The
initial stressing of the coil springs 218 is preferably selected in
such a way that one coil spring of each pair continues to store
some energy when the other spring of the respective pair is under
maximum compression (i.e., when the convolutions of the other
spring abut each other and cause the spring to act as a solid
block). This ensures that the coil springs 218 remain in optimum
positions relative to the respective masses 215 and relative to the
casing 230, not only as seen in the axial direction but also as
seen in the circumferential direction of the casing. The latter
constitutes the input element of the damper 210 and is fixedly
secured to one of the two cheeks 205 shown in FIG. 4.
[0088] Another advantage of coil springs 218 which are prestressed
during each stage of operation of the piston engine (as well as
when the engine is turned off) is that each of the masses 215 is
invariably held in the respective chamber 231 without any play or
without a play which could adversely affect the operation of the
damper 210.
[0089] The parameters of the coil springs 218 and of the masses 215
are preferably selected in such a way that the damping frequency of
the damper 210 is properly related to the characteristic frequency
of the crankshaft 203. The ends of the chambers 231 (as seen in the
axial direction of the crankshaft 203) are sealed by suitable lids
233. The lids 233, 234 which are shown in FIG. 4 are arcuate parts
made of sheet metal; such lids are secured to the casing by bonding
(such as welding), by rivets and/or other types of fasteners and/or
by calking.
[0090] As can be readily seen in FIG. 5, the casing (input element)
230 of the damper 210 is substantially U-shaped (this casing
actually resembles a saddle or a horseshoe) and surrounds a major
portion of the respective cheek 205. The casing 230 can be slipped
onto the left-hand cheek 205 of FIG. 4 in a direction to the right,
i.e., toward the illustrated crankpin 204. When the mounting of the
casing 230 on the respective cheek 205 is completed, two parallel
legs 235, 236 of the casing (such legs extend transversely of the
axis of the crankshaft 203 and in a direction away prom the
chambers 231) are closely adjacent two parallel sides of the cheek
205 and are affixed to the cheek (i.e., to the crankshaft 203) by
bolts 237 or any other suitable fasteners. The axes of the properly
mounted fasteners preferably intersect or are very close to the
axis of the illustrated crankpin 204.
[0091] When the masses 215 are in frictional engagement with the
respective outer walls 232 of the casing 230 under the action of
centrifugal force, these masses operate in parallel with the coil
springs 218.
[0092] At least one of the chambers 231 can communicate with the
interior of the housing for the crankshaft 203 by way of one or
more channels (not specifically shown) so that it can receive some
of the lubricant which serves to lubricate and remove heat from the
bearings for the crankpin(s) 204 and/or end portions of the
crankshaft. In addition, the passage or passages for the flow of
lubricant (e.g., oil) into and from one or more chambers 231 can be
dimensioned in such a way that they cause the development of an
additional damping action, namely an action which assists the
damping action furnished by the masses 215 and coil springs 218.
This even further reduces the likelihood of the development of
harmonic vibrations.
[0093] Additional damping action can be achieved by resorting to
one or two energy storing members corresponding to the diaphragm
spring 26 shown in FIG. 1. For example, one such diaphragm spring
can be inserted (in prestressed condition) between the masses 215
and the lid 233, and another diaphragm spring can be installed
between the masses 215 and the lid 234. The diaphragm spring(s) can
be utilized alone or with one or more suitably stressed leaf
springs, or they can be replaced by leaf springs.
[0094] FIG. 5 shows by broken lines a coil spring 241 which reacts
against the inner side of the respective wall 232 and bears upon
the surface at the bottom of a radially outwardly widening recess
or socket 240 in the convex radially outer surface of the
respective mass 215. The purpose of the coil spring 241 is to bias
the respective mass 215 radially inwardly in the respective chamber
231, i.e., counter to the bias of the respective pair of coil
springs 218 and counter to the action of centrifugal force which
develops when the casing 230 is caused to rotate with the
crankshaft 203, i.e., when the piston engine is on. An important
advantage of the coil spring 241 (or an equivalent biasing means)
is that, by properly selecting the initial bias of the spring 241,
one can select that rotational speed of the crankshaft 203 at which
the centrifugal force acting upon the mass 215 which is biased by
the spring 241 overcomes the bias of the spring 241 and compels the
convex radially outer surface of the mass 215 to frictionally
engage the complementary concave internal surface of the respective
wall 232. The bias of the spring 241 can be selected in such a way
that, when the piston engine embodying the structure of FIGS. 4 and
5 is idle, or when the RPM of the crankshaft 203 is below a
predetermined threshold value, the spring 241 can bias the concave
radially inner surface of the respective mass 215 into frictional
engagement with the convex external surface of the arcuate radially
inner wall 242 of the casing 230.
[0095] It is clear that the dimensions and bias of the coil spring
241 as well as the dimensions and configuration of the recess 240
must be selected with a view to ensure that the surfaces bounding
the recess 240 do not: prevent the spring 241 from assuming
(inclined) positions corresponding to the end positions of the
corresponding mass 215 in the respective chamber 231.
[0096] For example, the initial bias of the spring 241 can be
related to the bulk of the mass 215 and to the initial bias of the
respective coil springs 218 in such a way that, when the RPM of the
crankshaft 203 is relatively low, the mass 215 does not contact the
walls 232 and 242 of the casing 230 or is in negligible or
relatively weak frictional engagement with one of the walls 232,
242. Furthermore, the initial bias of the spring 241 can be such
that, when the action of centrifugal force upon the mass 215
matches or closely approximates the action of the mass 215 upon the
spring 241, frictional engagement between the mass and the casing
230 is nil or practically nil. Such state of equilibrium develops
at a preselected RPM of the crankshaft 203, i.e., the damping
action which develops as a result of frictional engagement of the
mass 215 with the casing 230 can be varied (determined in advance)
by the simple expedient of properly selecting the initial bias or
prestressing of the spring 241. The initial bias of the spring 241
can be selected with a view to ensure that the force applied to the
mass 215 by this spring and the centrifugal force acting upon the
mass balance each other within a certain range of rotational speeds
of the crankshaft 203. If the RPM drops below the lower limit of
such range, the frictional engagement between the mass and the
casing 230 can be further reduced, and the frictional engagement
can increase (or can begin to be effective) if the RPM of the
crankshaft rises above the upper limit of the range.
[0097] It is further clear that a spring 241 (or one or more
equivalent resilient biasing means) can be provided for each mass
215 of the damper 210. Moreover, though FIG. 4 shows a damper 210
on only one of the two illustrated cheeks 205 of the crankshaft
203, each of these cheeks can carry a discrete damper, and the two
dampers may but need not be identical.
[0098] If the crankshaft 210 of FIGS. 4 and 5 comprises two or more
crankpins 204 (depending on the number of pistons in the engine),
two or more dampers 210 or equivalent dampers can be distributed in
the axial direction of the crankshaft, depending on the desired
overall damping action and on the damping capacity of individual
dampers. Moreover, the distribution of the dampers in the axial
direction of the crankshaft can be further selected with a view to
prevent or to at least reduce any unbalance of the crankshaft. This
reduces the likelihood of extensive wear upon the radial and/or
axial bearings for the crankshaft.
[0099] The structure shown in the lower right-hand corner of FIG. 4
is to represent a damper which may but need not be identical with
the damper 210. Alternatively, or in addition to its vibration
damping action, such structure can act as a counterweight which
opposes or prevents an imbalance of the crankshaft.
[0100] FIG. 5a shows a portion of a camshaft 303 and a portion of a
casing 330 constituting a modification of the one-piece casing 230
forming part of the damper 210 shown in FIGS. , 4 and 5. The casing
330 is assembled of several sections or parts which must be secured
(e.g., welded) to each other in order to establish a solid and
long-lasting chambered receptacle for masses 315 (only one shown in
FIG. 5a) and associated pairs of coil springs corresponding to the
coil springs 218 shown in FIGS. 4 and 5.
[0101] The connection between the composite casing 330 and the
camshaft 303 comprises threaded fasteners 337 (only one shown in
FIG. 5a) which are normal to but do not intersect the axis of the
crankpin (indicated in FIG. 5a by broken lines). In contrast to the
fasteners 237 of FIG. 5 (these fasteners are subjected to shearing
stesses), the fasteners including the fastener 337 actually shown
in FIG. 5a are subjected to axial stresses.
[0102] As already mentioned in connection with the description of
the piston engine including the structure of FIGS. 4 and 5, the
casing 230 constitutes the input element of the damper 210.
However, and since the casing 230 is fixedly secured to one of the
cheeks 205, such cheek also forms part of the input element of the
damper 210. The same holds true for the casing 330 of the damper
shown in FIG. 5a. In other words, the damper 210 (as well as the
damper including the structure of FIG. 5a) is directly incorporated
into the respective crankshaft (203 in FIGS. 4 and 5). It can be
said that the crankshaft 203 and the damper 210 constitute two
components of a module which can be assembled preparatory to
incorporation of such module into the housing 202 of the piston
engine. Save for the feature that it comprises a composite housing,
the damper of FIG. 5a is assumed to be identical with or clearly
analogous to the damper 210, i.e., one cheek of the crankshaft 303
can be said to form part of the input element of the damper 310,
and this damper can be assembled with the crankshaft 303 before the
thus obtained module is installed in the housing of the piston
engine.
[0103] The situation is somewhat different in the embodiments of
FIGS. 1-2 and 3 because the dampers 10 and 110 are not mounted on
or integrated into the adjacent cheeks but are affixed to the
snouts (6 and 106) of the respective crankshafts 3 and 103.
[0104] FIGS. 6, 7 and 8 illustrate the details of an additional
damper 410 which constitutes a second modification of the damper
210 of FIGS. 4 and 5. As can be readily seen in FIG. 7, the casing
430 of the damper 410 has a substantially U-shaped cross-sectional
outline, and each of FIGS. 6 and 7 shows that the casing 430
surrounds a substantial portion of one cheek 405 of the crankshaft
403. The orientation of the threaded fasteners 437 (shown in FIGS.
6 and 7) which serve to fixedly secure the casing 430 to the
respective cheek 405 is similar to that of the fasteners 237 shown
in FIG. 5.
[0105] FIG. 6 shows that the non-referenced right-hand cheek of the
crankshaft 403 is larger than the left-hand cheek 405. The reason
is that the left-hand cheek 405 is smaller on purpose in order to
provide room for the casing 430 of the damper 410. In other words,
it can be stated that the damper 410 forms part of the respective
cheek 405 or that this cheek forms part of the damper 410.
[0106] The mass of the damper 410 is composed of two identical or
similar flat arcuate parts 415, 416 which are located at opposite
sides of a centrally located flange or web 451 of the casing 430
(i.e., of a portion of the input element of the damper 410). The
discs 415, 416 are non-rotatably connected to and spaced apart from
each other by a set of axially parallel rivets 450. These rivets
can be replaced by threaded fasteners, or the discs 415, 416 can be
welded or otherwise bonded to each other. If the discs 415, 416 are
to be welded to each other, at least one of these discs can be
provided with axially parallel lugs which are bonded to the other
disc.
[0107] The web 451 has an arcuate shape and resembles a portion of
a flat washer which extends radially of the axis of the crankshaft
403 between a trough-shaped inner wall 452 and a trough-shaped
outer wall 453 of the casing 430. The web 451 and the walls 452,
453 define two arcuate pockets which are located at the opposite
sides of the web 451, which can have the same depth (as measured
axially of the crankshaft 403), one of which receives the disc 415,
and the other of which receives the disc 416 of the mass of the
damper 410. The dimensions of the just mentioned pockets and of the
discs 415, 416 are or can be selected in such a way that each of
the two discs is fully (see FIG. 6) or only partially confined or
received in the respective pocket.
[0108] When the crankshaft 403 is caused to rotate, the discs 415,
416 tend to move radially outwardly toward the inner side of the
wall 453 at the respective sides of the web 451. However, the
arrangement is such that the convex external surfaces of the discs
415, 416 cannot bear directly upon the inner side of the wall 453
because the damper 410 further comprises two arcuate bearing
inserts or shoes 454, 455 one of which is located at the periphery
of the disc 415 at one side of the web 451 and the other of which
is located at the periphery of the disc 416 at the other side of
the web 451. The shoes 454, 455 are or can be made of a material
which is resistant to wear and can be readily finished to contact
the respective disc 415 or 416 or the respective portion of the
internal surface of the wall 453 with a minimum of friction. In the
embodiment of FIGS. 6 to 8, the shoes 454 and 455 are respectively
secured to the radially outermost portions of the discs 415 and 416
by dovetailed connectors 456. Other types of form-locking
connections between the shoes 454, 455 and the respective discs
415, 416 can be utilized with equal or similar advantage. It is
also possible to calk or bond (e.g., weld or glue) the shoes 454,
455 to the peripheries of the respective discs 415, 416.
[0109] The damper 410 further comprises energy storing elements 418
in the form of coil springs each of which is received in a window
457 of the disc 415, in a window 459 of the web 451 and in a window
458 of the disc 416. The configuration of the surfaces bounding the
windows 457, 458, 459 is preferably selected in such a way that the
coil springs 418 are held against any undue movement in the radial
as well as in the axial direction of the crankshaft 403.
[0110] The lengths of the coil springs 418 as well as the
dimensions of the windows 457, 458 relative to the dimensions of
the windows 459 are preferably selected in such a way that at least
the two outermost coil springs 418 (i.e., the coil springs adjacent
to the two fasteners 437, as viewed in FIG. 7) are installed in a
prestressed condition. The extent of initial stressing is
preferably such that one of the two outermost springs 418 continues
to store a certain amount of energy when the other outermost spring
has already undergone a maximal (total) compression so that its
convolutions abut each other and together form a solid block which
cannot undergo any further compression. The advantages of such
prestressing of at least some of the coil springs 418 are the same
as or clearly analogous to those already described in connection
with the coil springs 218 of the damper 210 shown in FIGS. 4 and
5.
[0111] It has been found that the damper 410 operates quite
satisfactorily if the two neighboring centrally located coil
springs 418 (such as the two lowermost springs 418 shown in FIG. 7)
are also installed in a prestressed condition and actually bear
against each other.
[0112] FIG. 7 shows that the median window 459 of the web 451 is
longer (as seen in the circumferential direction of the casing 430)
than the other two windows 459 (for the two upper springs 418, as
viewed in FIG. 7) and receives portions of the two centrally
located springs 418. The longer median window 459 of the web 451 is
partially overlapped by radially extending portions 461 of the
discs 415, 416. The portions 461 flank those portions of the two
median coil springs 418 which abut each other in the longer window
459. Such mounting ensures that the two median coil springs 418
operate in series.
[0113] FIG. 8 shows a friction generating device including a
corrugated spring 462 and a friction ring 463 installed between the
web 451 and, the disc 416. The spring 462 reacts against the disc
416 and urges the friction ring 463 against the adjacent side of
the web 451. At the same time, the spring 462 pulls the disc 464 in
a direction to the right, as viewed in FIG. 8, i.e., into
frictional engagement with the adjacent side of the web 451.
Actually, the spring 462 urges the disc 415 against a second
friction disc 464 which, in turn, bears against the adjacent side
of the web 451. The friction disc 463 and/or 464 can be omitted by
increasing the thicknesses of the disc 415 and/or 416.
[0114] The fasteners 437 serve as one of the means for securing the
frame 430 to the respective cheek 405. In order to further reduce
the likelihood of separation of the casing 430 from the crankshaft
403, particularly under the action of centrifugal force, the piston
engine embodying the structure of FIGS. 6 to 8 further comprises
two form-locking connections 465, 465 which are effective between
the end portions of the inner wall 452 of the casing 430 and the
adjacent portions of the cheek 405. Each of these form-locking
connections comprises a prismatic male connector 467 at the
respective end of the inner wall 452 and a complementary female
connector 468 (in the form of a groove parallel to the axis of the
crankshaft 403) in the cheek 405. It is clear that the male
connectors can be provided on the cheek 405 and the female
connectors are then provided in the casing 430, that one male
connector can be provided on the casing 430 and the other male
connector can be provided on the cheek 405, or that the
form-locking connections 465, 466 can be replaced by or used
jointly with other types of connections.
[0115] The casing 430 has a substantially U-shaped cross sectional
outline, the same as the casing 230 of the damper 210, and can be
made of a suitable metallic material.
[0116] FIG. 9 illustrates a portion of a damper 510 and a portion
of a crankshaft 503. In contrast to the form-locking connections
465, 466 of FIG. 7, the form-locking connection between the
crankshaft 503 and the casing of the damper 510 comprises a male
connector 566 which is provided on the cheek of the crankshaft and
extends into a complementary female connector in the casing of the
damper 510. In addition, the male connector 566 is bounded by at
least two surfaces which make a right angle; this brings about the
advantage that the centrifugal force which is opposed by such
form-locking connections cannot act upon the shanks of the threaded
fasteners 537 (only one shown in FIG. 9) which correspond to the
fasteners 437 shown in FIG. 7. The form-locking connections (only
one can be seen in FIG. 9) which include male connectors 566
establish a particularly firm mechanical bond between the casing of
the damper 510 and the selected cheek of the crankshaft 503.
[0117] It is advisable to provide the improved damper with a
lubricating system which ensures a positive (forced) circulation of
oil or another suitable lubricant. Such lubricating system can
constitute the lubricating system of the piston engine or a
discrete lubricating system which is designed to lubricate only the
component parts of the damper, namely the input element, the mass
and the energy storing elements between the input element and the
mass. For example, a discrete lubricating system for the damper can
include an arrangement which injects lubricant into the damper.
[0118] FIG. 10 illustrates a further damper 610 which is affixed to
a cheek 605 of the crankshaft 603 by a mechanical connection 667
including mating axially parallel splines 668 and 669 provided on
the cheek 605 and on the inner wall of the casing 630,
respectively. The splines 668, 669 have substantially trapezoidal
cross-sectional outlines.
[0119] It is possible to design the splines 668, 669 of the
connection 667 in such a way that they taper in the axial direction
of the crankshaft 603. This ensures that, once properly assembled,
the connection 667 is automatically held against separation of its
splines in one axial direction of the crankshaft. Uncontrolled
movements in the opposite direction can be prevented by employing,
for example, a split ring (not shown) which is carried by the
crankshaft 603 and extends into a groove of the casing 630.
Alternatively, the split ring or an analogous ring can be secured
to the crankshaft 603 in such a way that it overlies the end faces
at the larger ends of the splines 669 on the casing 630.
[0120] An additional important advantage of energy storing elements
(such as the coil springs 418 of the damper 410 shown in FIGS. 6 to
8) which are installed in their casing (430 of the damper 410) or
solely between the input element and the mass of the damper
(reference may be had, for example, to the damper 10 of FIGS. 1 and
2) in prestressed condition is that such initial stressing of the
energy storing elements compensates for eventual manufacturing
tolerances and/or for wear upon the component parts of the damper.
Thus, initial stressing ensures that the characteristic curve of
the damper is predictable (i.e., it follows a preselected optimum
pattern) during each stage of angular displacement of the input
element and the mass relative to each other; this includes the
initial stage when the input element and/or the mass is caused to
turn from a starting or zero position, and this also embraces
angular displacements of the input element and the mass relative to
each other after the energy storing elements and/or the surfaces
surrounding the windows for the energy storing elements have
undergone at least a certain amount of wear. Otherwise stated,
initial stressing of the energy storing elements of the damper
ensures that the spring constant remains unchanged and that the
damping frequency also remains at least substantially constant
during the useful life of the damper.
[0121] Another important advantage of the improved damper is that
it can be readily installed in piston engines of known design upon
relatively small alterations of the housing (FIGS. 1-3) or a cheek
(FIGS. 4-10). For example, each of the casings shown in FIGS. 4 to
10 can be mounted on its crankshaft by the simple expedient of
slipping it onto the selected cheek in the axial direction of the
crankshaft. This simplifies and reduces the cost of assembly of the
damper with the crankshaft and the cost of installing the
crankshaft in the housing of the engine.
[0122] As already mentioned hereinbefore, the improved damper can
serve the additional purpose of acting as a counterweight for the
crankshaft. Such function can be performed with particular
advantage by a damper which is mounted on a cheek of the
crankshaft, especially on a cheek flanking the first crankpin.
[0123] As also mentioned hereinbefore, it might be desirable to
provide a crankshaft with two or even more dampers. For example,
the crankshaft 3 of FIGS. 1 and 2 can cooperate with two dampers,
namely the illustrated damper 10 which is affixed to the snout 6
and a second damper (not shown) which is mounted on the main
bearing journal at the other axial end of the crankshaft 3. It is
equally possible to employ the damper 10 (which is mounted on the
snout 6) with a second damper which is mounted on one of the cheeks
5 forming part of the crankshaft 3.
[0124] It is also within the purview of the invention to mount the
damper (or one of two or more dampers) on the crankshaft in such a
way that a torque limiting device determines the magnitude of
torque which can be transmitted between the crankshaft and the
input element of the damper. For example, one can employ a suitable
slip clutch which operates between the input element of the damper
and an adjacent portion of the crankshaft.
[0125] The making of at least some of the constituents of the
improved damper from a metallic sheet material is desirable in many
instances because this contributes to lower cost of the damper. For
example, the parts 11, 16 and 17 of the damper 10 can be made of
sheet metal. The making of the parts 16, 17 involves simple
stamping, and the making of the part 11 involves a stamping
operation followed by an embossing or an analogous deforming
operation to form the cupped portion 21.
[0126] The frictional damping device 25 of the piston engine 1
shown in FIGS. 1 and 2 can be designed to be effective during each
and every stage of angular movement of the input element 11 and the
mass 15 relative to each other. However, it is also possible to
employ a friction generating device which operates with a certain
delay, particularly when the direction of angular movement of the
input element relative to the mass (or vice versa) is reversed.
Thus, and referring again to FIGS. 1-2, the frictional damping
device 25 can be designed in such a way that it becomes active
after the input element 11 has completed a certain angular movement
(relative to the mass 15) from a starting or neutral position, or
after the input element 11 has reversed the direction of its
movement so that the initial stage of such angular movement in the
newly selected direction takes place relative to the mass 15. The
same can apply for movements of the mass 15 relative to the input
element 11.
[0127] It is further possible to equip a damper with several
frictional damping devices, e.g., with a device (such as 25) which
is active whenever one of the parts 11, 15 turns or tends to turn
relative to the other of these parts, and with a device which
becomes effective only after one of the parts 11, 15 has already
completed a predetermined angular movement relative to the other of
these parts. This holds true regardless of whether the improved
vibration damper is mounted adjacent to one of the cheeks forming
part of a crankshaft, or is mounted on (so that it surrounds a
portion of) a cheek, or is designed in such a way that it forms
part of a cheek or that the cheek is a component part of the
improved vibration damper.
[0128] Without further analysis, the foregoing will so fully reveal
the gist of the present invention that others can, by applying
current knowledge, readily adapt it for various applications
without omitting features that, from the standpoint of prior art,
fairly constitute essential characteristics of the generic and
specific aspects of the above outlined contribution to the art of
vibration dampers for the crankshafts of piston engines and,
therefore, such adaptations should and are intended to be
comprehended within the meaning and range of equivalence of the
appended claims.
* * * * *