Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a belt and pulle~
power transmitting a~rangement or system for trans-
mission of rotary po~er ~rom the crankshaft or the
drive shaf-t of an internal combustion engine to various
power consuming devices associated with the engine.
Modern passenger cars as well as industrial/commercial
vehicles usually recluire an alternator or generator
driven by the crankshaft. The generator is necessary
to supply electrical power for operating headlights,
recharging the battery, supplying power to a radio,
etc. Further, many passenger vehicles and very nearly
all industrial vehicles of any si~e are equipped with
power steering and power brakes. These latter auxiliary
power devices are usually in the form of a rotary pump,
with the power required to operate them derived from
the engine crankshaft. It is customary to drive such
auxiliary power consuming devices by means of several
belts, the belts being driven by one or more pulleys
attached to the engine crankshaft or drive shaf-t.
It is known in the internal combustion engine
art that torsional vibrations are con-t:inuously cJenerated
in the crankshaft by virtue of -Ihe inheren-t mode of
operation and mcchanical characteristics of an internal
cornbustion enc~ine. It is already known that -the attain-
ment of dangerollsly hiyh resonan-t modes of such
torsional vibra-tions rnay be inhibited or prevented by,
for exarnple, -the placlng of a torsional vibration damper
on the crankshaft. Ilowever, such dampers do not eliminate
-torsional vibrations, they merely preclude the build-up
of such vibrations, in cer-tain resonan-t modes, -to high
magnitudes which could in some circumstances lead to
failure of the crankshaft. Such vibrations are,
oftentimes referred to as resonant vibrations. In
ac]dition to these (resonant) vibrations there exist
other vibrations, these latter being of relatively
high arnplitude (5 double amplitude) and relatively
low Erequencies, such as those present at low and at
engine idling speeds. These latter (slow) vibrations
are inherent in six cylinder engines as 3rd order
vibrations arrd in eight cylinder englnes as 4-th order
vibrations.
Because torsional vibrations are always
present, it is clear that a drive pulley attached to
the drive shaft will also be subject to torsional
vibrations, namely, the pulley will also exhibit tor-
sional vibrations in a back and forth manner while it
is turning unidirectionally with the crankshaft.
Wi-th the tendency of au-tomotive designers to employ a
single belt to drive the auxiliary power devices (as
opposed to the prior practice of employing a plurality
of belts) the total length of the driving belt is
accordinyly extended. While the number of driving
belts from the drive shaf-t drive pulley to the
auxiliary power devices is diminished, thus saving
expense, such new design procedures carry with them
certain disadvan-tages. One par-ticularly noticeable
disadvantage is present. Namely, the belt is rnore
suscep-tible to wear clue to the attainment of oscilla-
tions, in turn derived from the torsional vibrations of
the cranksllaEt to ~hich the pulley is attached. The
so--called slow vihratiolls are part;cu]arly troublesome
in this respect. l~ith a converltional pulley, the peri-
phery of the pulley ~ill obviously transrnit oscilla-
tions -to -the belt which passes around and is driven by
it. These oscillations, par-ticularly with lonc3er drive
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belts can result in the attainment of undesirably high
vibration amplitudes. In turn, large amplitude vibrations
of the driving belt may result in shor-ter belt life,impro-
per contact be-tween the driving belt and its driven aux-
iliary power devicesr and the belt may be thrown completelyoEf the pulleys.
Accordingly there is provided a pulley and belt sys-
tem for transmittiny power Erom the drive shaft oE an
internal combustion engine to one or more auxiliary,
pulley-driven power devices, the drive shaft possessing
torsional vibrations as it unidirectionally rotates, the
drive shaft coupled by means of a driving pulley to at
least one driven pulley for driving an auxiliary power
device such as a compressor, electrical generator or the
like, the improvemen-t comprising, the drive pulley being of
the fluid shear -type having a fluid coupling between the
pulley hub portion which is rigidly coupled to the drive
shaft and the radially ou-termost pulley portion which is
coupled to the belt, whereby the ~luid coupling isolates
the torsional vibrations of the drive shaft from the belt,
-to thereby lessen the occurrence of large ampli-tude vibra-
tions in the belt due to torsional vibra-tions in the drive
shaft.
IN THE DRAWI~IGS:
Figure 1 is a partially cross-sectional partially
schematic, view of a drive pulley Eormed in accordance with
this invention.
Figure 2 is a partially schematic perspective view
illustrating the use oE the pulley oE this invention in
combination with the crankshaEt oE an internal combustion
engine and auxiliary power devices.
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Referring now to Figure 1 of the drawings,
the numeral 10 denotes generally the fluid shear drive
pulley of this invention, the pulley receiving and
coupled to a crankshaft or drive shaft 12 of an
internal combustion engine. The shaft 12 passes through
the central portion of pulley hub 14, the hub being
optionally provided with one or rnore angularly spaced
apertures 16 to facili.tate attachrnent of the c.rank-
shaft 12 to the hub 14. Such attachment is not illu-
strated for purposes of clarity. The axial locationof the pulley along the shaft is no-t material for the
practice of this invention. The numeral 18 denotes an
angularly continuous and radially e~tending rib or web
mernber integrally attached to hub portion 14, the
radially outerrnost portion of the former carrying an
angularly continuous ring member or portion 17. The
numeral 20 denotes -the radially outermost portion or
rim of the pulley, the surface of the rim being
(optionally) provided with a plurality of angularly
continuous grooves to facilitate frictional contact
between the outermost pulley surface and the drive belt
(not illustratcd). The numeral 22 denotes a first side
cover while the numeral 24 denotes a second side cover.
These side covers are each angularly con-tinuous. The
nurnerals ~6 and 28 each schema-tically denote a seal
or seal beari.ng, the f~mction of which is to permit
relative rotation between the side covex members 22
and 24 which carry rim portion 20 and hub 14 which
carrles mclrlbcrs 18 and 17. Such seal bearings are
wel] kno~n so-ca].led shelf items, and any of a great
variety of con-;truct:ions of s~lch seal bcarings rnay be
selected. The nurneral 30 denotes an O-riny which may
either be square or round in transverse cross-section,
-the O--rings serving to establish a flu;.d seal between
the outer periphery OI member 20 of the pulley and the
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radially outermost Elanges of side covers 22 and 24~
The numeral 32 denotes an angularly con-tinuous cavity
between the exterior of ring-like portions 18 and 17
and the interior sur.Eaces of side covers 22, 24, seal
5 bearing members 26 and 28 and rim 20. At its time oE
manuEacture, the pulley 10 is provided witn a viscous
shear liquid which occupies and fills annular cavity
32.
It will be understood that constructions
of fluid shear pulleys themselves are already known,
as shown for example in U. S. Patents 3,430,743 to
Fujita, 3l498,431 to Sutaruk, and 3,910,391 to Detty.
In operation, with a belt (not illustrated)
running around a portion of the circumference of the
15 pulley 10 at rim portion 20 thereof, the crankshaEt 12
transmits torque to hub 14 by virtue of the rigid con-
nection therebetween. All of the -torsional vibrations
of the shaft 12 are accordingly present in the motion of
hub 14 during rotation. These motions are accordingly
also present in annular web 18 and ring member 17. sy
virtue of fluid shear coupling, an action well under-
stood by workers in the automotive arts, the unidirec-
tional rotary motion of hub 14 is transmitted to member
20 and associated covers 22 and 24 of the pulley by
virtue of fluid shear. However, because of -the fluid
shear connection between ring members 17 and 18 and
the outermost port:ion 20 of pulley 10, the relatively
large bac]c and forth twistings which represent the
(slow) torsional vibrations oE cranksha.Et 12 are
hardly transmitted at all to belt driving portion 20.
Thus, during operation, side covers 22 and 24 together
with pulley rim portion 20 rotate re:La-tive to ring
portions 17 and 18, with this relative rotation made
possible by means o:E rotary seal or seal bearing members
26 and 28 which also maintain the shear fluid in annular
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drive cavity or chamber 32.
Referring now to Figure 2 of the drawings,
the pulley of this invention is illustrated in com-
bination ~ith auxiliary power devices often found in
modern internal combustion engines. The numeral 34
denotes a belt driven by pulley 10 and driving a first
belt driven auxiliary power device such as an alter-
nator 36, a second auxiliary power device such as a
power steering pump 38, and a third auxiliary power
device such as a power brake pump 40. It will be
understood that the number and location of such auxi-
liary power devices relative to the pulley 10 may be
varied.
From a consideration of Figures 1 and 2, the
reader will now be in a position to comprehend that
torsional vibrations of the crankshaft 12 as it is
undergoing unidirectional motion, while transmitted
to hub 14, will be only very slightly transmitted, if
at all, to pulley rim portion 20 and hence will
effectively be absent from power or driving belt 34.
This lack of back and forth twistings of the periphery
or rim 20 of pulley 10 will result in a lesser pro-
bability of the build-up of undesirably high modes in
belt 3~ of both transverse and longitudinal vibrations.
In turn, this will result in longer belt life and also
a more uniform operation of the auxiliary power devices
36, 38 and 40.
