Note: Descriptions are shown in the official language in which they were submitted.
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POLYGONAL SPRING COUPLING
BACKGROUND OF THE INVENTION
[0001] This application is a continuation-in-part application claiming
priority to U.S.
application Ser. 16/008,679, filed June 14, 2018.
[0002] The present invention relates to couplings across which torque is
transferred, in
particular to a coupling for use in a variety of industrial applications, such
as in a hybrid electric
generating and storage system associated with an internal combustion engine.
BACKGROUND OF THE INVENTION
[0003] Hybrid electric vehicles having an internal combustion engine combined
with a motor-
generator and an electrical energy storage system have been the focus of
considerable attention
in the automotive field, particularly in the field of passenger vehicles.
Development of hybrid
electric vehicle systems has only recently begun to attract significant
interest in commercial and
off-road vehicles, e.g., trucks and busses in Vehicle Classes 2-8, in earth-
moving equipment and
railroad applications, and in stationary internal combustion engine-powered
installations.
[0004] U.S. Patent Application No. 15/378,139, assigned to the present
Applicant and
incorporated by reference in full herein, discloses a novel approach to
providing the benefits of
hybrid electric technologies in which a hybrid electric vehicle system is
located at a front end of
an engine, with a motor-generator being arranged in a manner that requires
little or no extension
of the length of the front of the vehicle. This system is referred to as a
front end motor-generator
or "FEMG" system.
[0005] As used in this description, the "front end" of the engine is the end
opposite the end
from which engine-generated torque output is transferred to the primary torque
consumers, such
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as a vehicle's transmission and drive axles or a stationary engine
installation's load, such as a
pump drive. Typically, the rear end of an engine is where the engine's
flywheel is located, and
the front end is where components such as engine-driven accessories are
located (e.g., air
conditioning and compressed air compressors, engine cooling fans, coolant
pumps, power
steering pumps).
[0006] In this front end motor-generator system, the motor-generator is
located in the front
region of the engine, laterally offset to the side of the rotation axis of the
engine crankshaft, and
is supported on a torque transfer segment (also referred to as a "drive unit")
between the motor-
generator and the region immediately in front of the front end of the engine's
crankshaft. The
torque transfer segment may take the form of a narrow-depth parallel shaft
gearbox arranged
with its input rotation axis co-axial with the engine crankshaft.
[0007] An important feature of the front end generator system is that the
motor-generator
exchanges torque with the engine crankshaft via the torque transfer segment
and a switchable
coupling (i.e., disengageable) between the torque transfer segment and the
front end of the
crankshaft. The switchable coupling includes an engine-side portion coupled
directly to the
engine crankshaft, a drive portion engageable with the engine-side portion to
transfer torque
therebetween, and an engagement device, preferably an axially-actuated clutch
between the drive
portion and the engine-side portion. The engine-side portion of the coupling
includes a crankshaft
vibration damper (hereafter, a "damper"), unlike a conventional crankshaft
damper that
traditionally has been a separate element fixed to the crankshaft as a
dedicated crankshaft
vibration suppression device. This arrangement enables transfer of torque
between the accessory
drive, the motor-generator and the engine in a flexible manner, for example,
having the accessory
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drive being driven by different torque sources (e.g., the engine and/or the
motor-generator),
having the engine being the source of torque to drive the motor-generator as
an electric generator,
and/or having the motor-generator coupled to the engine and operated as a
motor to act as a
supplemental vehicle propulsion torque source.
[0008] Particularly preferably, the switchable coupling is an integrated
clutch-pulley-damper
unit having the clutch between the engine side damper portion and the drive
portion. The drive
side portion includes a drive flange configured to be coupled to the engine-
end of the torque
transfer segment, the drive flange also including one or more drive pulley
sections on its outer
circumference. This preferred configuration also has all three of the pulley,
clutch and damper
arranged concentrically, with at least two of these elements partially
overlapping one another
along their rotation axis. This arrangement results in a disengageable
coupling with a greatly
minimized axial depth to facilitate FEMG mounting in the space-constrained
environment in
front of an engine. The axial depth of the coupling may be further minimized
by reducing the
axial depth of the clutch, pulley and damper to a point at which the drive
pulley extends
concentrically around all or at least substantially all of the clutch and the
engine-side damper
portion of the coupling.
[0009] Alternatively, one or more of the three clutch, pulley and damper
portions may be
arranged co-axially with, but not axially overlapping the other portions as
needed to suit the
particular front end arrangements of engines from different engine suppliers.
For example, in an
engine application in which a belt drive is not aligned with the damper (i.e.,
the damper does not
have belt-driving grooves about its outer circumference, such as in some
Cummins engine
arrangements), the belt-driving surface of the pulley portion of the coupling
need not axially
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overlap the damper. In other applications having belt drive surfaces on the
outer circumference
of the damper and a further belt drive surface on a pulley mounted in front of
the damper, such as
in some Detroit Diesel engines, the coupling that would be used in place of
the original damper
and pulley may be arranged with both belt drive surfaces on a pulley that
extends axially over the
damper (i.e., the damper axially overlaps substantially all of both the damper
and the clutch), or
with a belt drive surface on the outer circumference of the damper, for
example, to drive engine
accessories that are never disconnected from the crankshaft, such as an engine
coolant pump,
while another other belt drive surface is located on the pulley member that
extends axially over
the clutch.
[0010] Previously, crankshaft dampers were typically designed with an outer
portion, typically
a concentric ring, resiliently connected to an inner hub of the damper
directly mounted on the
front end of the crankshaft. Such dampers were designed such that the inertia
of the outer
portion would permit the outer portion to concentrically oscillate about the
inner hub at a
frequency that effectively matched and offset crankshaft rotation vibrations
(i.e., small angular
irregularities in the crankshaft's rotation caused by "micro" accelerations
and decelerations of
the crankshaft associated with individual force pulses applied to the
crankshaft, e.g., individual
cylinder combustion events, individual cylinder compression stroke resistance,
etc.). Left
unaddressed, these crankshaft rotational speed oscillations can cause
significant damage to the
engine's internal components.
[0011] The addition of a switchable coupling, such as the clutch-pulley-
damper unit disclosed
in Application No. 15/378,139, to the front end of a crankshaft has the
potential to alter the
torsional stiffness seen by the crankshaft when the switchable coupling is
closed and the torque
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transfer segment is thereby coupled to the crankshaft. When so coupled, the
torque transfer
segment gear train and the attached motor-generator may present the crankshaft
with increased
inertia which can impact the natural frequency of the mass elastic system. The
result can be less
effective damping of the crankshaft vibrations than desired.
[0012] The present invention provides a switchable coupling which addresses
this problem by
including a resilient portion in the clutch-pulley-damper unit that
effectively isolates much of the
additional inertia of the torque transfer segment and motor-generator from the
engine crankshaft.
[0013] Preferably, at the point at which the drive input to the torque
transfer segment is
coupled to the output of the switchable coupling (in the clutch-pulley-damper
unit and gearbox in
Application No. 15/378,139, via a male-female spline connection), a polygonal-
shaped coupling
is provided, with at least one of the male and female polygonal portions
having area in which
additional flexibility is incorporated. For example, on the male side of a
triangular polygonal
coupling, near each of the three corners a slot (or other geometry) may be
provided that allows
each corner to slightly flex when loaded by angular vibration pulses from the
crankshaft. Such
an arrangement would allow the male portion of the torque transfer segment-to-
switchable
coupling arrangement to rotate slightly relative to the female portion in
response to the
crankshaft vibrations. The present invention is not limited to a slot
configuration, but may use
any aperture geometry the provides the desired amount of resilient response to
crankshaft
acceleration/deceleration pulses.
[0014] With the present invention's the use of a polygonal drive arrangement
with vibration-
absorbing features, the crankshaft is effectively isolated from the inertia of
the torque transfer
segment and motor-generator by the vibration-absorbing features. The clutch-
pulley-damper unit
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therefore may be designed in a manner that keeps its vibration response range
seen by the
crankshaft in the range of the crankshaft vibrations, yet ensure the
crankshaft is still able to
transmit its full drive torque to the torque transfer segment and the motor-
generator.
[0015] The shape of the polygonal coupling is not limited to a triangular
polygon, but instead
may have any number of sides, as long as the polygon is modified to induce the
desired coupling
flexibility as in the triangular example. Moreover, the present invention is
not limited to any
particular shape (e.g., oval, dog-bone), as long as the vibration-absorbing
portions of the shape
permit the coupling to absorb circumferential vibrations while still
maintaining the ability to
transfer torque output from the crankshaft to the torque transfer segment, as
would a splined
coupling.
[0016] An
additional factor to consider in the design of the present invention is the
ratio of
torsional strength to torsional stiffness of the coupling. The torsional
stiffness of the coupling is
reduced with decreasing stiffness of the portions of the coupling at the
corners of the polygon,
which allows the corners to slightly flex in response to angular vibration
pulses, for example by
including transverse breaks in portions of the coupling that are radially
adjacent to
circumferentially-oriented recesses at each apex, thereby forming separate
circumferentially-
oriented "arms" that can independently flex. Similarly, the ratio of torsional
flexibility to
torsional strength may be increased by omitting such breaks, resulting in a
solid "bridge" section
between a recess and the axial face of the coupling part. The result is a
stiffer, but to an even
greater degree stronger, arrangement that increases the ratio of torsional
strength to torsional
stiffness. The torsional strength/weight ratio may also be altered by altering
the relative sizes of
the circumferentially-aligned recesses relative to the thickness of the
radially adjacent portions.
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[0017] Regardless of the specific approach taken, it is desirable to have
the ratio of torsional
strength to torsional stiffness to be optimized for the application,
particularly where the resonant
frequency is to be kept as low as possible.
[0018] A further aspect of the present invention is the opportunity to provide
increased
vibration damping in the coupling, by including a damping medium in the
recesses. A small
amount of damping is provided inherently by the coupling material's elasticity
(i.e., a small
amount of energy dissipation in the form of heat generated by friction between
components and
hysteresis of the material as it is compressed and tensioned in response to
vibrations). This
damping may be significantly increased by the additional of a damping medium
in the coupling
recesses, particularly in embodiments in which the arms are separated and thus
capable of greater
relative movement. Suitable damping materials include an elastomer, wax, a
sponge-like
material and/or another material capable of dissipating kinetic energy
generated by relative
movements in response to angular vibrations.
[0019] The polygonal coupling of the present invention is not limited to use
in front end
motor-generator systems, or to applications in which an internal combustion
engine is present.
The potential applications of the inventive polygonal coupling include any
application in which
torque is transferred over a rotating coupling, such as between driven and a
driving shafts. Such
applications include various industrial applications, such as torque transfer
to and/or from an
electric motor, a compressor, a pump, a gear drive, a transmission, and the
like. Moreover, the
present invention is not limited to internal combustion engine applications,
but may be used with
any form of power transmission device, such as an electric motor of a vehicle
equipped with an
electric drive motor.
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[0020] Other objects, advantages and novel features of the present invention
will become
apparent from the following detailed description of the invention when
considered in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figs. 1A and 1B are schematic illustrations of an overall view of the
arrangements of
an FEMG system in accordance with an embodiment in Application No. 15/378,139.
[0022] Figs. 2A-2C are cross-section views of an embodiment of a clutch-pulley-
damper and
assembled FEMG components in accordance with an embodiment in Application No.
15/378,139.
[0023] Figs. 3A-3C are views of the components of the Figs. 2A-2C clutch-
pulley-damper unit.
[0024] Figs. 4A-4B are oblique views of components of a polygonal coupling in
accordance
with an embodiment of the present invention.
[0025] Fig. 5 is an oblique view of a component of a polygonal coupling in
accordance with
another embodiment of the present invention.
[0026] Figs. 6A-6B provide a cross-section view of an assembled embodiment of
the
polygonal coupling of the present invention.
[0027] Fig. 7 is an oblique view of another embodiment of a polygonal coupling
in
accordance with the present invention.
[0028] Fig. 8 is an oblique view of an embodiment of the present invention
with a damping
material integrated therein.
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DETAILED DESCRIPTION OF THE DRAWINGS
[0029] Fig. 1A is a schematic illustration showing components of an embodiment
of an FEMG
system as in Application No. 15/378,139. Fig. 1B is a schematic illustration
of several of the
FEMG system components in the chassis of a commercial vehicle. In this
arrangement, the
engine accessories (including air compressor 1, air conditioning compressor 2
and engine cooling
fan 7 arranged to pull cooling air through engine coolant radiator 20) are
belt-driven from a pulley
5. The pulley 5 is located co-axially with a damper 6 coupled directly to the
crankshaft of the
internal combustion engine 8. The accessories may be directly driven by the
drive belt or
provided with their own on/off or variable-speed clutches (not illustrated)
which permit partial or
total disengagement of an individually clutch-equipped accessory from the belt
drive.
[0030] In addition to driving the accessory drive belt, the pulley 5 is
coupled a drive unit
having reduction gears 4 to transfer torque between a crankshaft end of the
drive unit and an
opposite end which is coupled to a motor-generator 3 (the drive unit housing
is not illustrated in
this figure for clarity). A disengageable coupling in the form of a clutch 15
is arranged between
the crankshaft damper 6 and the pulley 5 (and hence the drive unit and the
motor-generator 3).
Although schematically illustrated as axially-separate components for clarity
in Fig. 1A, in this
embodiment the crankshaft 6, clutch 15 and pulley 5 axially overlap one
another at least
partially, thereby minimizing an axial depth of the combined pulley-clutch-
damper unit in front
of the engine. Actuation of the pulley-clutch-damper clutch 15 between its
engaged and
disengaged states is controlled by an electronic control unit (ECU) 13.
[0031] On the electrical side of the motor-generator 3, the motor-generator
is electrically
connected to a power invertor 14 which converts alternating current (AC)
generated by the
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motor-generator output to direct current (DC) useable in an energy storage and
distribution
system. The power invertor 14 likewise in the reverse direction converts
direct current from the
energy storage and distribution system to alternating current input to power
the motor-generator
3 as a torque-producing electric motor. The inverter 14 is electrically
connected to an energy
storage unit 11 (hereafter, an "energy store"), which can both receive energy
for storage and
output energy on an on-demand basis.
[0032] In this embodiment, the energy store 11 contains Lithium-based storage
cells having a
nominal charged voltage of approximately 3.7 V per cell (operating range of
2.1 V to 4.1 V),
connected in series to provide a nominal energy store voltage of 400 volts
(operating voltage
range of approximately 300 V to 400 volts) with a storage capacity of between
approximately 12
and 17 kilowatt-hours of electrical energy. Alternatively, the cells may be
connected in series and
parallel as needed to suit the application. For example, 28 modules with four
series-connected
cells per module could be connected in series and in parallel to provide an
energy store with the
same 17 kilowatt hours of stored energy as the first example above, but with a
nominal operating
voltage of 200 V volts and twice the current output of the first example.
[0033] In addition to the relatively high-capacity, low charge-discharge rate
Lithium-based
storage cells, the energy store 11 in this embodiment includes a number of
relatively low-capacity,
high charge-discharge rate of super capacitors to provide the energy store the
ability over short
periods to receive and/or discharge very large electrical currents that could
not be handled by the
Lithium-based storage cells (such cells being typically limited to
charge/discharge rates of less
than 1 C to only a few C).
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[0034] Figures 2A-2C show cross-section views of an embodiment in Application
No.
15/378,139 of the clutch-pulley-damper unit 19 and of an assembled
configuration of FEMG
system hardware with this clutch-pulley-damper embodiment. In this embodiment
the gearbox
16 containing reduction gears 4 receives the motor-generator 3 at a motor-
generator end of the
gearbox. The motor-generator 3 is secured to the housing of gearbox 16 with
fasteners such as
bolts (not illustrated). A rotor shaft 18 of the motor-generator 3 engages a
corresponding central
bore of the adjacent co-axially-located gear of the reduction gears 4 to
permit transfer of torque
between the motor-generator 3 and the reduction gears 4.
[0035] At the crankshaft end of the gearbox 16, the reduction gear 4 which is
co-axially-
aligned with the clutch-pulley-damper unit 19 is coupled for co-rotation to
pulley side of the
clutch-pulley-damper unit 19, in this embodiment by bolts (not shown) passing
through the co-
axial reduction gear 4. The engine-side portion of the coupling (the portion
having the
crankshaft damper 6) is configured to be coupled to the front end of the
engine crankshaft by
fasteners or other suitable connections that ensure co-rotation of the engine-
side portion 6 with
the crankshaft. As described further below, the gearbox 16 is separately
mounted to a structure
that maintains the clutch-pulley-damper unit 19 co-axially aligned with the
front end of the
engine crankshaft.
[0036] The cross-section view in Fig. 2B is a view from above the FEMG front
end hardware,
and the oblique cross-section view in Fig. 2C is a view at the crankshaft end
of the gearbox 16.
In this embodiment, the gearbox, motor-generator and clutch-pulley-damper unit
assembly is
arranged with the motor-generator 3 being located on the left side of the
engine crankshaft and
on the front side of the gearbox 16 (the side away from the front of the
engine), where the motor-
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generator 3 may be located either in a space below or directly behind the
vehicle's engine
coolant radiator 20. Alternatively, in order to accommodate different vehicle
arrangements the
gearbox 16 may be mounted with the motor-generator 3 to the rear of the
gearbox 16, preferably
in a space laterally to the left side of the engine crankshaft (for example,
adjacent to the oil pan at
the bottom of the engine). The gearbox 16 further may be provided with dual-
sided motor-
generator mounting features, such that a common gearbox design may be used
both in vehicle
applications with a front-mounted motor-generator and vehicle applications
with the motor-
generator mounted to the rear side of the gearbox.
[0037] Figs. 3A-3C are views of the components of the clutch-pulley-damper
unit 19 of Figs.
2A-2C. When assembled, the unit is unusually narrow in the axial direction due
to the
substantial axial overlapping of the pulley 5, engine-side portion 6
(hereafter, damper 6) and
clutch 15. In this embodiment the pulley 5 has two belt drive portions 21
configured to drive
accessory drive belts (not illustrated), for example, one portion arranged to
drive the engine
cooling fan 7 surrounding the clutch 15, and another portion arranged to drive
other engine
accessories such as the air compressor 1. The drive belt portions 21 in this
example
concentrically surround the damper 6 and the clutch 15 (the belt drive portion
21 surrounding the
damper 6 is omitted in Figs. 2B and 2C for clarity).
[0038] Within the clutch-pulley-damper unit 19 the clutch 15 includes two
axially-engaging
dog clutch elements 25, 26. As shown in the Figs. 2A-2C cross-section views,
the central core
dog clutch element 25 is fixed for rotation with the damper 6, in this
embodiment by bolts
extending through axial bolt holes 28 from the FEMG gearbox side of the clutch-
pulley-damper
unit 19. The pulley 5 is rotationally supported on the central core element 25
by bearings 34.
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[0039] An engine-side portion of the outer circumference of the central core
dog clutch
element 25 includes external splines 29 arranged to engage corresponding
internal splines 30 at
an inner circumference of the axially-movable dog clutch element 26. The
external splines 29
and internal splines 30 are in constant engagement, such that the movable dog
clutch element 26
rotates with the damper 6 while being movable axially along the damper
rotation axis.
[0040] The movable dog clutch element 26 is also provided with axially forward-
facing dogs
31 distributed circumferentially about the gearbox side of the element 26 (the
side facing away
from the engine). These dogs 31 are configured to engage spaces between
corresponding dogs
32 on an engine-facing side of the pulley 5, as shown in Fig. 3C. The movable
dog clutch
element 26 is biased in the clutch-pulley-damper unit in an engaged position
by a spring 33
located between the damper 6 and the movable dog clutch element 26, as shown
in Fig. 2A.
Figures 2B and 2C show the clutch disengaged position, in which the spring 33
is compressed as
the movable dog clutch element 26 is axially displaced toward the damper 6.
[0041] In this embodiment a clutch throw-out rod 27 is located concentrically
within the
central core dog clutch element 25. The engine-side end of the throw-out rod
27 is arranged to
apply an axial clutch disengagement force that overcomes the bias of spring 33
to axially
displace the dog clutch element 26 toward the damper 6, thereby disengaging
its forward-facing
dogs 31 from the corresponding dogs 32 at the engine-facing side of the pulley
5. In this
embodiment, the gearbox end of the clutch throw-out rod 27 is provided with a
bushing 303 and
a bearing 304 which enables the bushing to remain stationary while the throw-
out rod 27 rotates.
[0042] The clutch throw-out rod 27 is axially displaced to disengage and
engage the dog
clutch 15 by a clutch actuator 22. In this embodiment the clutch actuator 22
is pneumatically-
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actuated, with compressed air entering fitting 305 over clutch actuator
diaphragm 41 and thereby
urging the center portion of the diaphragm 41 into contact with the throw-out
rod bushing 303 to
axially displace the clutch throw-out rod 27 toward the engine to disengage
the clutch 15. When
compressed air pressure is removed from the clutch actuator the diaphragm 41
retracts away
from the engine, allowing the biasing spring 33 to axially displace the throw-
out rod 27 and the
dog clutch element 26 toward the pulley 5 to reengage the clutch dogs 31, 32
so that the pulley 5
co-rotates with the damper 6.
[0043] Figs. 4A and 4B show an embodiment in accordance with the present
invention of a
polygonal coupling 90 between an input element of the torque transfer segment
(pulley-end gear
36) and an output element of the clutch-pulley-damper unit 19 (pulley 5).
Figure 4A illustrates
this polygonal coupling embodiment's male portion 91 carried on the gearbox
pulley-end gear
36, and a female portion 92 formed in the opposing region 96 of the pulley 5.
The locations of
the male and female portions may be reversed between the pulley 5 and the
gearbox pulley-end
gear 36. Fig. 4B is a reverse side view of the pulley 5 in Fig. 4A, showing
the face of pulley
region 96 that abuts the face of the gearbox pulley-end gear 36 containing the
male portion 91.
[0044] The polygonal coupling male portion 91 includes a plurality of
axially-aligned recesses
93, here arranged at the peaks of the lobes of the male polygon. The material
between the
recesses 93 and the outer circumference of the male portion 91 is undercut by
grooves 94, such
that elastically-deflectable arms 95 are formed on the periphery of the
polygonal coupling male
portion 91. The recesses 93 are arrayed in both directions so that the male
portion 91 has
engineered flexibility in both the forward and reverse rotation directions.
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[0045] With this configuration, the present invention permits a small amount
of relative
rotation between the polygonal coupling male portion 91 and female portion 92,
and hence
between the pulley-end gear 36 and the pulley 5, while the broad surfaces of
the sides of the
polygon male and female portions ensure that the coupling can transfer a full
torque load
between the pulley 5 and the pulley-end gear 36 as the crankshaft rotated.
This relative rotation
effectively de-couples the inertia of the torque transfer segment and the
motor-generator from the
crankshaft over the relatively small angular displacement of the crankshaft
during its vibrations
(its micro-accelerations and decelerations), while still maintaining full
torque transfer capability
across the polygonal coupling.
[0046] The recesses 93 in this embodiment are linear slots, which are
relatively easy to
manufacture in a simple milling operation. However, the recesses are not
limited to this shape.
For example, the recesses may be curved, and may have other features such as a
broad circular
end that reduces local stresses and the potential for crack development over a
large number
flexing cycles of the arms 95. Similarly, the shape and width of the grooves
94 which separate
the arms 95 from the face of the pulley-end gear 36 may vary in shape, height
and depth as
desired to suit a particular application. Such variations of the recesses 93
and grooves 94 are
permissible as long as the configuration of the polygonal coupling 90 is such
that the arms 95 are
capable of enduring a large number of flexing cycles over the design life of
the polygonal
coupling, and the recesses and grooves are sized to provide a degree of
flexibility that permits
the clutch-pulley-damper unit 19 to present a desired degree of torsional
stiffness to the engine
crankshaft.
[0047] The material of the polygonal coupling may be selected based on the
amount of torque
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to be transferred across the coupling, the size of the polygonal coupling
components, the
temperature in the operating environment, etc.. For example, in high torque
applications and/or
in applications in which the male and female polygonal coupling portions are
small (thus
increasing the local stresses at the mating surfaces of the male and female
portions), a high-
strength material such as steel may be used to ensure sufficient longevity of
the coupling.
Alternatively, in lower torque loading and/or local stress applications in
lower-temperature
environments, other materials such as plastic or rubber coupling portions may
be used. Further,
mixtures of materials are possible. For example, one of the male or female
components may be
designed as a sacrificial portion, so that in the event of overloading of the
polygonal coupling
only the sacrificial side of the coupling is damaged.
[0048] In a further embodiment of the present invention schematically
illustrated in Fig. 5, the
recesses 93 and arms 95 are provided on the female portion of the coupling,
positioned such that
the arms 95 may be elastically deformed outwards by the corners of the male
polygon to
accommodate the desired small amount of relative rotation between the pulley 5
and the torque
transfer segment gear 36 (which may have a solid male portion of the
coupling). As in the
embodiment in Fig. 4, the recesses 93 must be sized and configured to endure a
large number of
flexing cycles over the design life of the polygonal coupling, while providing
a degree of
flexibility that permits the clutch-pulley-damper unit 19 to present a desired
degree of torsional
stiffness to the engine crankshaft.
[0049] Figure 6B presents a cross-section view of an embodiment of a polygonal
coupling as
in Fig. 4A in an assembled state, taken along section line A-A in Fig. 6A. In
this view the male
portion 91 of the gearbox pulley-end gear 36 is inserted into, and axially
overlapped by, the
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female portion 92 in the region 96 of the pulley 5. In this state, engine
crankshaft micro-
accelerations/decelerations may be substantially absorbed by the resilient
arms 95 of the male
portion 91 as the female portion 92 oscillates about the axis of rotation in
response to the
crankshaft's motions.
[0050] Figure 7 shows a portion of a coupling embodiment in which the
torsional stiffness of
the coupling is increased relative to a coupling such as that shown in Fig. 4A
by not creating a
slot between the arms 95 that are radially outward of the recesses 93, but
instead maintaining the
respective pairs of arms 95 together at their apex 97 to form a more
rotationally strong and stiff
structure. The length and radial width of the arms may be increased or
decreased relative to one
another and/or in absolute size, as necessary to obtained a desired amount of
torsional strength
and stiffness.
[0051] Figure 8 shows another embodiment of a coupling similar to that shown
in Fig. 4A,
provided with a damping material 98 in the recesses 93 to provide increased
energy dissipation
capacity and thereby increase the coupling's ability to dampen movement caused
by the engine's
crankshaft vibrations.
[0052] The foregoing disclosure has been set forth merely to illustrate the
invention and is not
intended to be limiting. Because such modifications of the disclosed
embodiments incorporating
the spirit and substance of the invention may occur to persons skilled in the
art, the invention
should be construed to include everything within the scope of the appended
claims and
equivalents thereof.
[0053] Listing of reference labels:
1 air compressor
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2 air conditioning compressor
3 motor-generator
4 drive unit gears
pulley
6 damper
7 engine cooling fan
8 engine
9 vehicle batteries
DC/DC converter
11 energy store
12 battery management system
13 FEMG electronic control unit
14 AC/DC power inverter
clutch
16 gearbox
17 flange shaft
18 rotor shaft
19 clutch-pulley-damper unit
engine coolant radiator
21 belt drive portions
22 clutch actuator
23 clutch plates
24 clutch spring
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25, 26 dog clutch elements
27 clutch throw-out rod
28 bolt holes
29 external splines
30 internal splines
31,32 dogs
33 spring
34 bearings
90 polygonal coupling
91 polygonal coupling male portion
92 polygonal coupling female portion
93 recesses
94 grooves
95 arms
96 pulley outside face
97 apex
98 damping medium
303 bushing
304 bearing
305 fitting
19
