U.S. patent application number 15/805080 was filed with the patent office on 2018-03-01 for decoupler with tuned damping and methods associated therewith.
The applicant listed for this patent is LITENS AUTOMOTIVE PARTNERSHIP. Invention is credited to John R. ANTCHAK, Justin BOUDREAU, Patrick D. MARION, Gary J. SPICER, Lucas E. WILSON, Jun XU.
Application Number | 20180058507 15/805080 |
Document ID | / |
Family ID | 46050277 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180058507 |
Kind Code |
A1 |
ANTCHAK; John R. ; et
al. |
March 1, 2018 |
DECOUPLER WITH TUNED DAMPING AND METHODS ASSOCIATED THEREWITH
Abstract
In an aspect, the invention relates to a decoupler that is
positionable between a shaft (eg. for an alternator) and an endless
power transmitting element (eg. a belt) on an engine. The decoupler
includes a hub that mounts to the shaft, and a pulley that engages
the endless power transmitting element, an isolation spring between
the hub and the shaft. The decoupler provides at least a selected
damping torque between the hub and the pulley.
Inventors: |
ANTCHAK; John R.; (Aurora,
CA) ; XU; Jun; (Woodbridge, CA) ; MARION;
Patrick D.; (Aurora, CA) ; WILSON; Lucas E.;
(Toronto, CA) ; BOUDREAU; Justin; (Callander,
CA) ; SPICER; Gary J.; (Mississauga, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LITENS AUTOMOTIVE PARTNERSHIP |
Woodbridge |
|
CA |
|
|
Family ID: |
46050277 |
Appl. No.: |
15/805080 |
Filed: |
November 6, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13878879 |
Apr 11, 2013 |
|
|
|
PCT/CA2011/001263 |
Nov 14, 2011 |
|
|
|
15805080 |
|
|
|
|
61413475 |
Nov 14, 2010 |
|
|
|
61414682 |
Nov 17, 2010 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02B 67/06 20130101;
F16D 41/206 20130101; F16D 3/12 20130101; F16H 2055/366 20130101;
F16D 3/14 20130101; Y10T 29/49764 20150115; F16H 55/36 20130101;
F16D 7/025 20130101 |
International
Class: |
F16D 3/12 20060101
F16D003/12; F16D 7/02 20060101 F16D007/02; F02B 67/06 20060101
F02B067/06; F16H 55/36 20060101 F16H055/36; F16D 41/20 20060101
F16D041/20; F16D 3/14 20060101 F16D003/14 |
Claims
1. An endless drive arrangement for an engine, comprising: a
crankshaft pulley mountable to a crankshaft from the engine; an
alternator pulley mounted to an input shaft of an alternator,
wherein the alternator operates at at least a first switching
frequency and a second switching frequency; an endless drive member
that is positioned to transfer power from the crankshaft pulley to
the alternator pulley such that first order vibrations are produced
at the crankshaft; and a decoupler including a hub that is adapted
to be coupled to the alternator shaft such that the alternator
shaft co-rotates with the hub about a rotational axis, a pulley
rotatably coupled to the hub, the pulley having an outer periphery
that is positioned to engage the endless power transmitting
element, an isolation spring positioned to transfer rotational
force from the pulley to the hub and to accommodate torsional
vibration between the pulley and the hub, a first friction surface
operatively connected with the pulley, a second friction surface
operatively connected with the hub, a biasing member positioned to
exert a bias force between the first and second friction surfaces,
and a retainer engaging the biasing member to maintain the bias
force, wherein the second switching frequency is near a natural
resonance frequency of the decoupler and the bias force between the
first and second friction surfaces generates a damping torque
during relative rotational movement between the pulley and the hub
which attenuates said first order vibrations so as to reduce a
tendency of the alternator to operate at the second switching
frequency, thereby reducing a tendency of the alternator of
transmitting vibration to the decoupler at frequencies near the
natural frequency.
2. An endless drive arrangement as claimed in claim 1, wherein the
natural frequency is about 15 Hz.
3. An endless drive arrangement as claimed in claim 2, wherein the
second switching frequency is in the range of about 5 Hz to about
20 Hz.
4. An endless drive arrangement as claimed in claim 1, wherein the
damping torque results in a peak-to-peak angular range of relative
movement between the pulley and the hub of less than about 1
degree.
5. An endless drive arrangement as claimed in claim 1, wherein the
damping torque is selected such that a peak-to-peak angular range
of movement between the pulley and the hub results in at least a
selected fatigue life for the isolation spring.
6. An endless drive arrangement as claimed in claim 1, wherein the
decoupler includes a one-way clutch that enables the hub to overrun
the pulley.
7. A decoupler for an endless drive arrangement which includes a
crankshaft-driven pulley, an alternator pulley mounted to an input
shaft of an alternator which operates at at least first and second
switching frequencies, and an endless drive member that is
positioned to transfer power from the crankshaft pulley to the
alternator pulley, wherein first order vibrations are produced at
the crankshaft, the decoupler comprising: a hub that is mountable
to the alternator shaft such that the alternator shaft co-rotates
with the hub about a rotational axis; a pulley rotatably coupled to
the hub, the pulley having an outer periphery that is adapted to
engage the endless power transmitting element; an isolation spring
positioned to transfer rotational force from the pulley to the hub
and to accommodate torsional vibration between the pulley and the
hub; a first friction surface operatively connected with the
pulley; a second friction surface operatively connected with the
hub; a biasing member positioned to exert a bias force between the
first and second friction surfaces; and a retainer engaging the
biasing member to maintain the bias force, wherein the second
switching frequency is near a natural resonance frequency of the
decoupler and the bias force between the first and second friction
surfaces generates a damping torque during relative rotational
movement between the pulley and the hub which attenuates said first
order vibrations so as to reduce a tendency of the alternator to
operate at the second switching frequency, thereby reducing a
tendency of the alternator of transmitting vibration to the
decoupler at frequencies near the natural frequency.
8. A decoupler as claimed in claim 7, wherein the natural frequency
is about 15 Hz.
9. A decoupler as claimed in claim 8, wherein the second switching
frequency is in the range of about 5 Hz to about 20 Hz.
10. A decoupler as claimed in claim 7, wherein the damping results
in a peak-to-peak angular range of relative movement between the
pulley and the hub of less than about 1 degree.
11. A decoupler as claimed in claim 7, wherein the damping torque
is selected such that a peak-to-peak angular range of movement
between the pulley and the hub results in at least a selected
fatigue life for the isolation spring.
12. A decoupler as claimed in claim 1, wherein the decoupler
includes a one-way clutch that enables the hub to overrun the
pulley.
13. A method for operating an engine accessory drive which includes
a crankshaft-driven pulley, an alternator pulley mounted to an
input shaft of an alternator operable at a plurality of switching
frequencies, and an endless drive member that is positioned to
transfer power from the crankshaft pulley to the alternator pulley,
the method including: installing a decoupler for transferring
torque between the alternator shaft and the endless drive member,
the decoupler including (i) a hub coupled to the alternator shaft,
(ii) a pulley rotatably coupled to the hub, the pulley having an
outer periphery that engages the endless power transmitting
element, (iii) an isolation spring positioned to transfer
rotational force from the pulley to the hub and to accommodate
torsional vibration between the pulley and the hub, (iv) a first
friction surface operatively connected with the pulley, and (v) a
second friction surface operatively connected with the hub;
rotating the crankshaft so as to rotate the engine accessory drive;
generating a damping torque during relative rotational movement
between the decoupler pulley and the decoupler hub by engaging the
first and second friction surfaces with sufficient force to
attenuate first order vibrations from the engine in order to reduce
the tendency of the alternator to operate at a switching frequency
near a natural frequency of the decoupler, thereby reducing a
tendency of the alternator to transmit vibration to the decoupler
at frequencies near the natural frequency.
14. A method as claimed in claim 13, wherein the natural frequency
is about 15 Hz.
15. A method as claimed in claim 14, wherein the second switching
frequency is in the range of about 5 Hz to about 20 Hz.
16. A method as claimed in claim 13, wherein the damping results in
a peak-to-peak angular range of relative movement between the
pulley and the hub of less than about 1 degree.
17. A method as claimed in claim 13, wherein the damping is
selected such that a peak-to-peak angular range of movement between
the pulley and the hub results in at least a selected fatigue life
for the isolation spring.
18. A decoupler as claimed in claim 13, wherein the decoupler
includes a one-way clutch that enables the hub to overrun the
pulley.
Description
[0001] This application is a Continuation of U.S. patent
application Ser. No. 13/878,879 which is a national phase entry
application of PCT/CA2011/001263, filed Nov. 14, 2011, which claims
the benefit of: U.S. Provisional Application No. 61/413,475, filed
Nov. 14, 2010 and U.S. Provisional Application No. 61/414,682,
filed Nov. 17, 2010, the contents of all of which are incorporated
herein by reference in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to decoupling mechanisms for
allowing belt driven accessories to operate temporarily at a speed
other than the speed of the belt, and more particularly to
decoupling mechanisms for alternators.
BACKGROUND OF THE INVENTION
[0003] It is known to provide a decoupling mechanism on an
accessory, such as an alternator, that is driven by a belt from the
crankshaft of an engine in a vehicle. Such a decoupling mechanism,
which may be referred to as a decoupler assembly or a decoupler,
permits the associated accessory to operate temporarily at a speed
that is different than the speed of the belt. As is known, the
crankshaft undergoes cycles of accelerations and decelerations
associated with the firing of the cylinders in the engine. The
decoupler permits the alternator shaft to rotate at a relatively
constant speed even though the crankshaft from the engine, and
hence, the pulley of the decoupler, will be subjected to these same
cycles of decelerations and accelerations, commonly referred to as
rotary torsional vibrations, or torsionals.
[0004] Such a decoupler is a valuable addition to the powertrain of
the vehicle. However, some engines are harsher on the decoupler
than other engines and decouplers on such engines do not last as
long as would otherwise be desired. It would be advantageous to
provide a decoupler that worked on such engines.
SUMMARY OF THE INVENTION
[0005] In an aspect, the invention relates to a decoupler that is
positionable between a shaft (eg. for an alternator) and an endless
power transmitting element (eg. a belt) on an engine. The decoupler
includes a hub that mounts to the shaft, and a pulley that engages
the endless power transmitting element, an isolation spring between
the hub and the shaft. The decoupler provides at least a selected
damping torque between the hub and the pulley.
[0006] The damping torque may be selected to provide less than a
selected maximum amount of torsional vibration to the hub of the
decoupler particularly in a selected frequency range. In particular
providing less than the selected maximum amount of torsional
vibration to the hub of the decoupler in the selected frequency
range is useful when the decoupler is connected to a shaft of an
alternator. It has been found that this inhibits the voltage
regulator of the alternator from controlling the alternator at a
switching frequency that is in the range of 15 Hz, which may be
near the natural frequency of the decoupler. Inhibiting the
alternator from having such a switching frequency reduces any
torsional vibration induced in the hub from the alternator, in that
frequency range. This reduces the overall torsional vibration
incurred by the hub, which improves the fatigue life of the
isolation spring.
[0007] Through significant testing it has been found that the
voltage regulator of the alternator may be upset by current
fluctuations that result from first order vibrations that are
incurred by the alternator rotor. When this occurs, the voltage
regulator itself may switch to a switching frequency in the range
of about 15 Hz. When it does this, it generates a vibration in the
alternator rotor that it transmitted back into the hub of the
decoupler. Because this frequency is near the natural frequency of
the decoupler the hub may respond with a significantly increased
amplitude of vibration (i.e. the hub will reciprocate through a
higher angular range). This increased angular range of
reciprocation can significantly increase the stressed on the
isolation spring in the decoupler and thereby reduce its fatigue
life. By damping the vibrations from the engine, and in particular
the first order vibrations so that they are attenuated by a
selected amount before reaching the hub (and therefore before they
reach the alternator rotor) the voltage regulator is less likely to
respond to the current fluctuations generated thereby with a
switching frequency in the 15 Hz range. Thus the voltage regulator
will have a reduced tendency of feeding more vibration back into
the alternator rotor and the hub of the decoupler at frequencies
near the natural frequency of the hub.
[0008] In a particular embodiment, the decoupler includes, a hub, a
pulley, an isolation spring, a first friction surface, a second
friction surface and a retainer. The hub is adapted to be coupled
to the shaft such that the shaft co-rotates with the hub about a
rotational axis. The pulley is rotatably coupled to the hub and has
an outer periphery that is adapted to engage the endless power
transmitting element. The isolation spring is positioned to
transfer rotational force from the pulley to the hub and to
accommodate torsional vibration between the pulley and the hub. The
first friction surface is operatively connected with the pulley.
The second friction surface is operatively connected with the hub.
The friction surface biasing member is positioned for exerting a
biasing force to biasing the first and second friction surfaces
against each other. The retainer is engaged with the friction
surface biasing member and positioned to cause the friction surface
biasing member to apply at least a selected biasing force on the
first and second friction surfaces thereby generating at least a
selected damping torque during relative rotational movement between
the pulley and the hub.
[0009] The damping structure biasing member may be a Belleville
washer, which may have any suitable number of waves to suit the
application. Alternatively, the damping structure biasing member
may be a helical compression spring. As a further alternative, the
damping structure biasing member may be one of a plurality of
helical compression springs. In such an alternative embodiment, the
damping structure may further include a support member that has the
friction member on one side and a plurality of blind apertures or
other spring supports on the other side for receiving and
supporting the compression springs, such that the plurality of
damping structure biasing members each are positioned independently
of one another to urge the friction member in parallel with one
another. In another alternative embodiment, a plurality of damping
structure biasing members could be arranged in series with one
another (e.g. end-to-end).
[0010] In an aspect, the invention relates to a test decoupler for
use in helping to produce a production decoupler. The test
decoupler is positionable between a shaft (eg. for an alternator)
and an endless power transmitting element (eg. a belt) on an engine
or on a test setup intended to simulate an engine. The test
decoupler includes a hub that mounts to the shaft, and a pulley
that engages the endless power transmitting element, an isolation
spring between the hub and the shaft. The test decoupler is capable
of adjusting the amount of damping torque it produces between the
hub and the pulley. In this way it can be used to help determine a
suitable damping torque to provide in the production decoupler.
[0011] In an embodiment, the test decoupler includes, a hub, a
pulley, an isolation spring, a first friction surface, a second
friction surface and a retainer. The hub is adapted to be coupled
to the shaft such that the shaft co-rotates with the hub about a
rotational axis. The pulley is rotatably coupled to the hub and has
an outer periphery that is adapted to engage the endless power
transmitting element. The isolation spring is positioned to
transfer rotational force from the pulley to the hub and to
accommodate torsional vibration between the pulley and the hub. The
first friction surface is operatively connected with the pulley.
The second friction surface is operatively connected with the hub.
The friction surface biasing member is positioned for exerting a
biasing force to biasing the first and second friction surfaces
against each other. The retainer is engaged with the friction
surface biasing member. The position of the retainer controls the
biasing force of the friction surface biasing member. The retainer
is adjustable in position.
[0012] In another aspect, the invention is directed to a method of
producing a production decoupler for an engine, comprising: [0013]
a) providing resonance data associated with the engine; [0014] b)
determining using software an approximate damping torque to provide
a selected amount of damping between a hub and a pulley of the
production decoupler based on the resonance data provided in step
a); [0015] c) providing a test decoupler that is capable of
providing an adjustable damping torque including the approximate
damping torque determined in step b); [0016] d) selecting a final
damping torque to be provided by the production decoupler by
applying torsional vibrations on the test decoupler, based on the
resonance data of step a); and [0017] e) producing the production
decoupler that includes a production hub that is adapted to be
coupled to a shaft such that the shaft co-rotates with the hub
about a rotational axis, a pulley rotatably coupled to the hub and
having an outer periphery that is adapted to engage an endless
power transmitting element driven by the engine, and an isolation
spring positioned to transfer rotational force from the pulley to
the hub and to accommodate torsional vibration between the pulley
and the hub, wherein the production decoupler applies at least the
final damping torque between the production hub and the production
pulley.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The present invention will now be described by way of
example only with reference to the attached drawings, in which:
[0019] FIG. 1 is an elevation view of an engine with a plurality of
belt driven accessories, one of which has a decoupler in accordance
with an embodiment of the present invention;
[0020] FIG. 2 is an exploded perspective view of the decoupler
shown in FIG. 1;
[0021] FIG. 3 is a magnified sectional view of the decoupler shown
in FIG. 2;
[0022] FIG. 4 is a magnified sectional view of a variant of the
decoupler shown in FIG. 2;
[0023] FIG. 5 is a magnified sectional view of another variant of
the decoupler shown in FIG. 2,
[0024] FIG. 6 is a magnified sectional view of another variant of
the decoupler shown in FIG. 2;
[0025] FIG. 7a is a graph showing the vibration response of the
pulley and hub from the decoupler of FIG. 1 over a range of
frequencies;
[0026] FIG. 7b is a graph showing the torque response of the
decoupler of FIG. 1 in relation to relative displacement between
the pulley and hub;
[0027] FIG. 8 is a magnified sectional view of a test decoupler
that is capable of adjustable damping torque for use in designing
the decoupler shown in FIG. 1, in accordance with another
embodiment of the invention;
[0028] FIG. 9 is a flow diagram of a method of producing a
decoupler, in accordance with another embodiment of the
invention;
[0029] FIG. 10 is a magnified sectional view of a decoupler that is
capable of adjustable damping torque and including an actuator for
adjustment of the damping torque, in accordance with another
embodiment of the invention;
[0030] FIG. 11 is a magnified sectional view of a portion of the
decoupler shown in FIG. 10; and
[0031] FIG. 12 is a magnified sectional view of another decoupler
that is capable of adjustable damping torque and including an
actuator for adjustment of the damping torque, in accordance with
another embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Reference is made to FIG. 1, which shows an engine 10 for a
vehicle. The engine 10 includes a crankshaft 12 which drives an
endless drive element, which may be, for example, a belt 14. Via
the belt 14, the engine 10 drives a plurality of accessories 16
(shown in dashed outlines), such as an alternator 18. Each
accessory 16 includes an input drive shaft 15 with a pulley 13
thereon, which is driven by the belt 14. A decoupler 20 is provided
instead of a pulley, between the belt 14 and the input shaft 15 of
any one or more of the belt driven accessories 16, an in particular
the alternator 18.
[0033] Reference is made to FIG. 2, which shows a sectional view of
the decoupler 20. The decoupler 20 includes a hub 22, a pulley 24,
a first bearing member 26, a second bearing member 27, an isolation
spring 28, a carrier 30, and a one-way clutch 31, which in this
exemplary embodiment is a one-way wrap spring clutch comprising a
wrap spring 32.
[0034] The hub 22 may be adapted to mount to the accessory shaft 15
(FIG. 1) in any suitable way. For example, the hub 22 may have a
shaft-mounting aperture 36 therethrough that is used for the
mounting of the hub 22 to the end of the shaft 15, for co-rotation
of the hub 22 and the shaft 15 about an axis A.
[0035] The pulley 24 is rotatably coupled to the hub 22. The pulley
24 has an outer surface 40 which is configured to engage the belt
14. The outer surface 40 is shown as having grooves 42. The belt 14
may thus be a multiple-V belt. It will be understood however, that
the outer surface 40 of the pulley 24 may have any other suitable
configuration and the belt 14 need not be a multiple-V belt. For
example, the pulley 24 could have a single groove and the belt 14
could be a single V belt, or the pulley 24 may have a generally
flat portion for engaging a flat belt 14. The pulley 24 further
includes an inner surface 43, which the wrap spring 32 may engage
in order to couple the pulley and hub 22 together. The pulley 24
may be made from any suitable material, such as a steel, or
aluminum, or in some cases a polymeric material, such as certain
types of nylon, phenolic or other materials.
[0036] The first bearing member 26 rotatably supports the pulley 24
on the hub 22 at a first (proximal) axial end 44 of the pulley 24.
The first bearing member 26 may be any suitable type of bearing
member, such as a bushing made from nylon-4-6 or for some
applications it could be PX9A which is made by DSM in Birmingham,
Mich., USA, or some other suitable polymeric material, and may be
molded directly on the pulley 24 in a two step molding process in
embodiments wherein a molded pulley is provided. It may be possible
to use a bearing (e.g. a ball bearing) as the first bearing member
26 instead of a bushing. In such a case, the bearing could be
inserted into a mold cavity and the pulley 24 could be molded over
the bearing 26. Instead of a bearing, a metallic (e.g. bronze)
bushing may be provided, which can be inserted into a mold cavity
for the pulley molding process in similar fashion to the
aforementioned bearing.
[0037] The second bearing member 27 is positioned at a second
(distal) axial end 46 of the pulley 24 so as to rotatably support
the pulley 24 on a pulley support surface 48 of the hub 22. The
second bearing member 27 may mount to the pulley 24 and to the hub
22 in any suitable ways. In the embodiment shown, the second
bearing member 27 may be molded around the pulley support surface
48 by an injection molding process wherein the hub 22 forms part of
the mold. The hub 22 may have a coating thereon prior to insertion
into the mold cavity, to prevent strong adherence of the bearing
member 27 to the pulley support surface 48 during the molding
process, so that after removal of the hub 22 and bearing member 27
from the molding machine (not shown), the bearing member 27 can
rotate about the hub 22. The bearing member 27 may be press-fit
into a seat 49 on the pulley 24, and may be welded (e.g. laser
welded) with the pulley 24 in embodiments wherein the pulley 24 is
made from a suitable polymeric material. In such instances, the
material of the pulley 24 and the material of the first bearing
member 26 are selected so as to be compatible for joining by
whatever suitable joining process is selected, such as laser
welding. It will be noted that other ways of joining the second
bearing member 27 and the pulley 24 may be employed, such as
adhesive bonding, and/or using mechanical joining elements (e.g.
resilient locking tabs) that would lock the bearing member 27 to
the pulley.
[0038] The isolation spring 28 is provided to accommodate
oscillations in the speed of the belt 14 relative to the shaft 15.
The isolation spring 28 may be a helical torsion spring that has a
first helical end 50 that is held in an annular slot and that abuts
a radially extending driver wall 52 (FIG. 3) on the carrier 30. The
isolation spring 28 has a second helical end 53 (FIG. 2) that
engages a similar driver wall (not shown) on the hub 22. In the
embodiment shown, the isolation spring 28 has a plurality of coils
58 between the first and second ends 50 and 53. The coils 58 are
preferably spaced apart by a selected amount and the isolation
spring 28 is preferably under a selected amount of axial
compression to ensure that the first and second helical ends 50 and
53 of the spring 28 are abutted with the respective walls on the
carrier 30 and hub 22. An example of a suitable engagement between
the isolation spring 28, the hub 22 and the carrier 30 is shown and
described in U.S. Pat. No. 7,712,592, the contents of which are
incorporated herein by reference. A thrust plate 73 may be provided
to receive the axial thrust force of the carrier 30 resulting from
the axial compression of the spring 28.
[0039] The isolation spring 28 may be made from any suitable
material, such as a suitable spring steel. The isolation spring 28
may have any suitable cross-sectional shape. In the figures, the
isolation spring 28 is shown as having a generally rectangular
cross-sectional shape, which provides it with a relatively high
torsional resistance (i.e. spring rate) for a given occupied
volume. However, a suitable spring rate may be obtained with other
cross-sectional shapes, such as a circular cross-sectional shape or
a square cross-sectional shape.
[0040] Alternatively, the isolation spring 28 may be compression
spring. As a further alternative, the isolation spring 28 may be
one of two or more isolation springs, each of which is a
compression spring. Such a configuration is shown in U.S. Pat. No.
7,708,661 and US Patent application publication no. 2008/0312014,
PCT publication no. 2007/074016, PCT publication no. 2008/022897,
PCT publication no. 2008/067915, and PCT publication no.
2008/071306, all of which are hereby incorporated by reference in
their entirety.
[0041] In the embodiment shown in FIG. 2, a sleeve 57 is provided
between the isolation spring 28 and the clutch spring 32. The
sleeve 57 is, in the embodiment shown, a helical member itself,
although it could have any other suitable configuration such as a
hollow cylindrical shape. The sleeve 57 acts as a torque limiter by
limiting the amount of room available for radial expansion of the
isolation spring 28 (in embodiments wherein the isolation spring 28
is a torsion spring). Thus when a torque is provided by the pulley
24 that exceeds a selected limit, the isolation spring 28 expands
until it is constrained by the sleeve 57. An example of a suitable
sleeve 57 is shown and described in U.S. Pat. No. 7,766,774, the
contents of which are hereby incorporated by reference.
[0042] The helical clutch spring 32 has a first end 51 that is
engageable with a radial wall 55 of the carrier 30 and that may be
fixedly connected to the carrier 30. The helical clutch spring 32
has a second end 59 that may be free floating.
[0043] The carrier 30 may be made from any suitable material such
as, for example, a suitable nylon or the like.
[0044] When a torque is applied from the belt 14 to the pulley 24
to drive the pulley 24 at a speed that is faster than that of the
shaft 15, friction between the inner surface 43 of the pulley 24
and the coils of the clutch spring 32 drives at least one of the
coils of the clutch spring 32 at least some angle in a first
rotational direction about the axis A, relative to the first end 51
of the clutch spring 32. The relative movement between the one or
more coils driven by the pulley 24 relative to the first end 51
causes the clutch spring to expand radially, which further
strengthens the grip between the coils of the clutch spring 32 and
the inner surface 43 of the pulley 24. As a result, the first end
59 of the clutch spring 32 transmits the torque from the pulley to
the carrier 30. The carrier 30 transmits the torque to the hub 22
through the isolation spring 28. As a result, the hub 22 is brought
up to the speed of the pulley 24. Thus, when the pulley 24 rotates
faster than the hub 22, the clutch spring 32 operatively connects
the pulley 24 to the carrier 30 and therefore to the hub 22.
[0045] At the distal end of the hub 22 is a first friction surface
60 that engages a second friction surface 62 on a friction member
64. The friction member 60 is operatively connected to the hub 22
(in this particular instance it is directly on the hub 22). The
friction surface 62 is operatively connected to the pulley 24. In
this exemplary embodiment it is on the friction member 64, which is
adjacent to and axially and rotationally coupled to a thrust washer
66. A friction surface biasing member 68 is engaged axially and
rotationally with the thrust washer 66 and is retained in place by
a retainer member 69, and a seal cap 71 is provided to cover the
distal end to prevent intrusion of dirt and debris into the
interior space of the decoupler 20. The biasing member 68 urges the
friction surfaces 60 and 62 into engagement with each other with a
selected force. This selected force directly affects the frictional
force that the friction surfaces 60 and 62 exert on each other. The
biasing member 68 in FIGS. 2 and 3 is a Belleville washer 70.
However, it will be understood that other types of biasing member
could be used, such as for example, a helical compression spring 72
as shown in FIG. 4, a plurality of compression springs 74 as shown
in FIG. 5, or a monolithic elastomeric biasing member 76 as shown
in FIG. 6. Each of the friction member 64, the thrust member 66,
the biasing member 68 and the retainer 69 may be fixed rotationally
with the pulley 24 by any suitable means. For example, they may
each have a radial protrusion that extends into an axially
extending slot in the pulley 24. It will also be noted that in the
embodiments shown in FIGS. 4, 5 and 6 there is an additional thrust
plate (not numbered) between the retainer 69 and the biasing member
68 to assist with the distribution of force between them.
[0046] In each of these embodiments, the biasing member 68 is
positioned so that a selected normal force is applied on the
friction surfaces 60 and 62. Additionally, the materials that make
up the first and second friction surfaces 60 and 62 and the surface
finishes provided on these surfaces 60 and 62 are selected so that
these surfaces have a selected coefficient of friction. By
providing a selected coefficient of friction between the surfaces
60 and 62 and by providing a selected normal force, a selected
frictional force is exerted on the hub 22.
[0047] In the particular embodiment shown, the friction member 64
is engaged with the hub 22 directly. It is possible for the
friction member 64 to engage the hub 22 indirectly (e.g. through
engagement with a friction surface on another member that is itself
connected directly to the hub 22).
[0048] The selected frictional force may be referred to as a
selected damping force, which exerts a selected damping torque on
the hub 22. The purpose of this selected damping torque is
described below.
[0049] When an engine, such as engine 10, operates it is well known
that the crankshaft speed oscillates between high and low values
about a mean speed. The mean speed of the crankshaft 12 depends, of
course, on the RPM of the engine. The speed variations of the
crankshaft are an inherent property of internal combustion engines
due to the firing of the cylinders, which generates linear motion
in the pistons, which is transferred to the crankshaft 12 via
connecting rods. These speed variations of the crankshaft 12 are
transferred to the crankshaft pulley, from the crankshaft pulley
into the belt 14, and from the belt 14 to the decoupler pulley
24.
[0050] For a 4-cylinder engine the crankshaft 12 (and therefore the
decoupler pulley 24) undergo second-order vibrations. That is to
say, the frequency of the vibration of the pulley 24 is the speed
of the engine x the number of cylinders/2. Thus, for a 4-cylinder
engine at idle (e.g. about 750 RPM), the decoupler pulley 24
undergoes vibration at 750 rotations/minute.times.1 minute/60
seconds.times.4/2=25 Hz.
[0051] Reference is made to FIGS. 7a and 7b, which show test
results from a test performed on a test bench configured to
simulate the driving of the alternator 18 through a front engine
accessory drive of the type that is commonly employed in vehicles,
that is driven by a 4-cylinder engine at idle. Referring to FIG.
7a, the curve shown at 80 represents the amount of angular
oscillation that the pulley 24 undergoes in relation to frequency.
As can be seen, and as expected, at a frequency of about 25 Hz,
there is a peak 82 in the curve 80 indicative of a vibration of
about 8 degrees peak-to-peak. One can observe, however, that there
is a (much smaller) peak shown at 84 at about 12.5 Hz indicative of
a pulley vibration of less than a degree peak-to-peak. This is an
unexpected first order vibration, which may be due to several
factors, such as an imbalance in the crankshaft or some other
component in the FEAD system. An additional cause of such first
order vibrations however, occurs particularly in diesel engines. To
optimize catalytic converter function, such engines may alternate
between rich and lean firings. This generates a torque pulse twice
per cycle on a 4-cylinder, which means once per rotation of the
crankshaft. This is therefore a first order vibration.
[0052] The curve shown at 86 in FIG. 7a represents the amount of
angular oscillation that the hub 22 undergoes in relation to
frequency. As expected, there is a peak 88 at about 25 Hz that is
the result of the pulley oscillation at 25 Hz. The amplitude of the
oscillations at 25 Hz is about 4 degrees peak-to-peak. This is
expected given the approximate diameter ratio of the pulley 24 to
the hub 22. However, it can be seen that there is also a peak 90 at
the first order frequency (i.e. 12.5 Hz in this case). This peak 90
shows that very small vibrations at the pulley 24 (i.e. less than 1
degree) result in unexpectedly large vibrations at the hub 22
(about 5.5 degrees peak-to-peak).
[0053] Further analysis revealed that what appears to be occurring
is that the alternator's voltage regulator, changes its switching
frequency in certain situations to a frequency that is in the range
of about 15 Hz. The voltage regulator controls the voltage output
of the alternator 18, keeping the voltage constant regardless of
changes in engine speed (and therefore alternator rotor speed) and
electrical load. To carry this out, the voltage regulator
cyclically activates and deactivates the voltage at the excitation
windings thereby controlling the ratio of on time to off time so as
to adjust the output voltage based on the voltage generated in the
alternator. The voltage regulator is controlled based on a number
of inputs, and as such a number of situations can affect the
actions of the voltage regulator. For example, rotor speed
fluctuation can cause fluctuations in the current generated by the
alternator. This can cause the voltage regulator to change (drop)
the switching frequency to compensate for the fluctuating
current.
[0054] This effect on the voltage regulator is particularly strong
when there are first order vibrations transferred into the
decoupler 20 from the engine 10. When exposed to these first order
vibrations in particular the voltage regulator may react by
changing the switching frequency to a frequency in the range of
about 15 Hz.
[0055] The switching of the voltage regulator causes a certain
amount of torsional vibration in the alternator rotor and shaft,
which is transferred into the hub 22 of the decoupler 20. Thus, the
oscillations that result in the hub 22 are partly caused by the
oscillations in the pulley 24 and partly caused by the oscillations
in the alternator shaft (shown at 94 in FIG. 1). It will be noted
that the decoupler 20 may have a natural resonance frequency that
is somewhere in the range of about 5 Hz to about 20 Hz, or more
precisely from about 12 Hz to about 15 Hz. Vibrational inputs to
the hub 22 that are near the natural resonance frequency of the
decoupler 20 can become magnified. As noted above, the switching
frequency of the voltage regulator may be in the range of 15 Hz in
some situations when the voltage regulator is affected by the
fluctuations in the rotor speed. Thus the hub 22 can be subjected
to torsional vibrations from the alternator shaft at a frequency
that is near the natural frequency of the decoupler 20. Also as
noted above, there can be first order vibrations (which are near
the natural frequency of the decoupler 20 when the engine is at
idle) which are transmitted to the pulley 24 and through to the hub
22, which are the result of imbalances in the crankshaft 12 and the
like.
[0056] The amount of damping torque provided in the exemplary
decoupler 20 whose performance is shown in FIG. 7a is here is 0.29
in overrunning mode (i.e. when the hub 22 overruns the pulley 24).
In non-overunning mode the damping torque is half of the difference
in the upper and lower portions of the torque curve shown at 89 in
FIG. 7b.
[0057] The torsional vibrations at the hub 22 that are near the
natural frequency of the decoupler 20 and which therefore may get
magnified can impact the operating life of the decoupler 20, and in
particular the operating life of the isolation spring 28. The
particular amount of torsional vibration that would be considered
acceptable will vary from application to application. It is
possible that the operating life of the decoupler 20 may be
considered to be acceptable even though there is a 5.5 degrees
peak-to-peak oscillation when the engine is at idle. It depends of
course on many factors, such as the material of construction of the
components that make up the decoupler 20, and the number of
operational cycles that would constitute an acceptable operating
life. The operating life may, however, be considered too short. It
has been determined that a way of extending the operating life of
the decoupler 20 is to reduce the amplitude of vibration of the hub
22.
[0058] Thus, it is possible when designing the decoupler to start
by selecting a suitable operating life for it, then to decide what
maximum amplitude of vibration in the hub 22 is acceptable. The
amplitude of vibration can be controlled via damping. The amount of
damping that is required may be established empirically, by running
mathematical models, or by any other suitable method. In an
embodiment, the mathematical models would be run first. The results
from those models could be used to produce a test decoupler that is
capable of adjustable damping. This test decoupler is shown at 100
in FIG. 8. This test decoupler 100 may have many components similar
to those on the decoupler 10 shown in FIG. 2, such as a hub 122, a
pulley 124, an isolation spring 128, a wrap spring 132, a sleeve
157, bearing members 126 and 127, a thrust member 166, a friction
member 164 with a friction surface 162 thereon for engagement with
friction surface 160 on the hub 122, and may further include some
additional structure. For example, the decoupler 100 includes a
biasing member 102 that is made up of a plurality of Belleville
washers 70. Furthermore, the retainer, shown at 104 is axially
adjustable in position by means of a threaded exterior surface 106
on the retainer 104, that mates with a threaded surface 107 on the
pulley shown at 124. The threaded surfaces 106 and 107 also provide
structure with which the retainer 104 is held in whatever position
it is adjusted to. By providing the test decoupler 100, the damping
torque applied in the decoupler 100 can be easily set to the value
determined by the mathematical models, and can then be adjusted up
or down quickly in situ if it is determined that the oscillations
are too large. The oscillations can be measured during testing
using a number of different types of sensor that can provide
precise information relating to the angular position of the pulley
124 and the hub, shown at 22. For example, the 2SA-10 Sentron
sensor manufactured by Sentron AG, Baarerstrasse 73, 630O Zug,
Switzerland is a suitable sensor that can be used to measure the
torsional vibrations. Use of such a sensor to measure torsional
vibrations is described in PCT publication WO2006/045181 the
contents of which are incorporated herein by reference. The sensor
for the pulley 124 is shown at 108 and the sensor for the hub 122
is shown at 110. Sensor 110 is shown at the opposite end of
alternator shaft 15 (i.e. at the opposite end to the end that the
decoupler 100 is mounted to).
[0059] A controller 111 may be provided to receive signals from the
sensors 108 and 110 and can indicate to an operator what the
torsional vibrations are. The operator can then adjust the position
of the retainer 104 on the decoupler 100 to increase or decrease
the damping force until the torsional vibrations at the hub 122 are
below the determined limit (i.e. are below the maximum amplitude of
vibration calculated for the desired operating life). Alternatively
the system could be automated so that the controller 111 controls
the retainer 104 and positions it as necessary to achieve less than
a selected torsional vibration at the hub 122.
[0060] This test decoupler 100 may be used to assist in carrying
out a method of producing the production decoupler 20. The method
includes:
[0061] a) providing resonance data associated with the engine;
[0062] b) determining using software an approximate damping torque
to provide a selected amount of damping between a hub and a pulley
of the production decoupler 20 based on the resonance data provided
in step a);
[0063] c) providing a test decoupler (i.e. the test decoupler 100)
that is capable of adjustable damping torque;
[0064] d) determining a suitable damping torque for use with the
production decoupler 20 using the test decoupler 100, based on the
approximate damping torque determined in step b); and
[0065] e) producing the production decoupler 20 with a production
hub 22, a production pulley 24, a production friction member 64 and
a production biasing member 68 that is positioned and held to
generate a biasing force on the friction member 64 so that the
friction member 64 provides at least the suitable damping torque
between the hub 22 and the pulley 24. These steps are shown at 201,
202, 204, 206 and 208 respectively in the flow diagram shown in
FIG. 9, relating to a method 200. It will be noted that it is at
least conceivable that step b) could be omitted, and that step d)
could be carried out simply by progressively increasing the damping
torque until a selected result is observed. For example, the
damping torque can be increased until any torsional vibration
observed in the hub 122 is less than a selected level.
[0066] In step a), providing the resonance data may be achieved by
receiving the resonance data from a manufacturer of the engine, or
alternatively by receiving an example engine from the manufacturer
and testing it and measuring the resonance. Providing the resonance
data may also be carried out as follows. A customer (eg. an engine
manufacturer) initially gives the entity that is manufacturing the
decoupler 20 (which may simply be referred to as `the entity`),
some preliminary engineering data related to the inertia of various
components on the engine relating to the drive of the endless power
transmitting element. Also the customer may give the entity
projected loads and load profiles (steady frictional load, or
periodic pulsating load) of each component and information
regarding the endless power transmitting element, such as belt
stiffness if it is a belt. The entity takes the data and conducts a
preliminary analysis using software such as a simulation program.
The preliminary analysis results in an initial design for the
production decoupler 20 including an approximate spring rate for
the production isolation spring 28 for reducing the severity of the
resonances described by the resonance data, a maximum permissible
angular vibration in order to maintain a minimum fatigue life for
the isolation spring 28, and a prediction of an approximate damping
torque that needs to be provided by the production decoupler 20 to
achieve the desired fatigue life. Several design iterations may be
traded back and forth between the customer and the entity during
the process of designing and building a prototype engine.
[0067] The entity then refines the prediction of the minimum
damping torque by conducting tests using the test decoupler 100 in
FIG. 8. Preferably the tests are conducted on the actual vehicle
containing the actual engine on which the production decoupler 20
will be provided. This permits testing over the most complete range
of scenarios (idling while certain belt driven accessories are on,
such as the A/C compressor, and while certain electrical
accessories are on such as the lights), and can include the actual
ECU with its final programming (or as close to it as is available).
This is useful because the ECU can provide useful data to the
person adjusting the test decoupler 100, such as, for example,
alternator current, power steering pressure, A/C pressure, and the
like. Additionally, the voltage regulator is in many modern
vehicles no longer a separate component. Its function is instead
carried out by the ECU. If a complete vehicle is not available for
testing, an option is to use a test engine.
[0068] Sensors, such as, for example a Rotec sensor by SCHENCK
RoTec GmbH of Darmstadt, Germany, may be provided for detecting the
angular positions of the pulley 124 and the hub 122 during the
above described testing with the test decoupler 100. Using such
sensors, the test decoupler 100 can be adjusted in its damping
torque (e.g. by adjustment of the retainer to progressively
increase the biasing force on the friction member 164) until the
angular vibration of the hub 122 falls below the maximum
permissible angular vibration to achieve the minimum desired
fatigue life for the spring 28. For example, the damping torque may
be increased until the angular vibration observed at the hub 122
falls below 1 degree peak-to-peak. It has been observed that
providing a suitable amount of damping has a particularly
beneficial effect in relation to first order vibrations. More
particularly, by damping out first order vibrations transmitted
from the engine before they reach the hub 22 (i.e. between the
pulley 24 and the hub 22), the aforementioned current fluctuations
that occur in the alternator appear to be lower and the voltage
regulator appears to have a reduced tendency to react with a
switching frequency in the 15 Hz range. As a result, the voltage
regulator would contribute less to the vibrations of the hub 22 in
that frequency range.
[0069] If an engine is not available then an option would be to
acquire the components only, such as the alternator, the power
steering pump, the A/C compressor, and whatever other accessories
are driven by the belt. These components would be mounted onto a
thick metal backing plate in the correct X, Y and Z positions (i.e.
in the positions they will be mounted in when in the production
vehicle), and would be connected and controlled to generate the
correct loads (eg. power steering pressure, A/C pressure, etc.)
when rotated. This mounting plate may be assembled to a large
servo-hydraulic rotary torsional actuator drive system,
manufactured by servo-hydraulic companies such as MTS Systems
Corporation of Eden Prairie, Minn., USA, Team Machine Tools Inc. of
Concord, Ontario, Canada, or Horiba Automotive Test Systems Inc, of
Burlington, Ontario, Canada. The driveshaft of the servo-hydraulic
rotary torsional actuator drive system may spin the crankshaft from
idle (eg. about 600 RPM) to redline (eg. about 7,000 RPM), while
imputing simulated torsional vibrations into the belt drive in
order to simulate the primary combustion cycle torsional vibration
input (e.g. a second-order vibration for a four cylinder engine),
and the upper order harmonic vibrations, in order to simulate the
operation of a real engine.
[0070] During such a test, the torsional vibration within the
system may be measured at each major component using any suitable
means such as a torsional rotary vibration measurement system, or
TRVMS, (which is in effect a sophisticated FFT (fast Fourier
transform) analyzer), which is designed specifically for the
analysis of rotary torsional vibrations at multiple shafts.
[0071] Other quantities may be measured, such as instantaneous belt
span tension within each belt span between pulleys (eg. using
hub-load sensors), belt span flutter (eg. using lasers or microwave
radar sensors), belt tensioner arm oscillation deflection (using
suitable sensors), as well as the instantaneous load of each pulley
(alternator current, power steering pressure, A/C pressure,
etc.).
[0072] With these measurements the entity determines the overall
`health` of the belt drive (while `belt` is used in some instances,
it will understood that the endless power transmitting element may
be something other than a belt) under several real life conditions
which can be programmed and simulated into the MTS servo-hydraulic
test machine to mimic the torsional vibrations of the
crankshaft.
[0073] In such a test, the adjustable test decoupler 100 uses a
very fine thread 106 machined into the inner diameter of the
lead-in collar (the lead-in collar is the uppermost portion of the
pulley 124) so as to permit fine axial adjustment of the retainer
104.
[0074] A "drive nut" (i.e. the retainer 104) can be threaded into
or out of the threaded lead-in collar by rotating the drive nut in
a clockwise or counter-clockwise fashion, thereby adjusting its
axial position. The threaded drive nut 104 can be stopped and
temporarily locked in any position within the threaded collar, by
the use of a secondary locknut in the threaded collar.
[0075] The damping ratio (and therefore the damping force and the
damping torque) within the test decoupler 100 can be increased by
turning the drive nut 104 down onto the wave washer to increase the
biasing force exerted by biasing member 102. The damping ratio (and
therefore the damping force and the damping torque) can be
decreased by backing the drive nut 104 out, decreasing the biasing
force exerted by the biasing member 102 on the test friction member
164.
[0076] During this test, a variety of different wave washers
(Belleville washers) with higher or lower spring rates could be
employed. Additionally, a variety of different frictional damping
components could be employed, using materials with greater or
lesser friction coefficients and longevity characteristics.
[0077] Many other tests may be performed by the entity on the
endless power transmission element itself, in order to determine
its exact mechanical properties (eg. lateral and linear spring
rates, stiffness, frictional values, belt stretch, etc).
[0078] Once the retainer 104 has been adjusted successfully to
provide an angular vibration at the hub 122 that is sufficiently
low, the test decoupler 100 may be mounted in a system where the
torque exerted by the decoupler 100 and the biasing force exerted
by the biasing member 102 can be measured. A torque curve similar
to the curve xx in FIG. 7b may be generated. Once this data is
known, a design for the production decoupler 20 can be made,
wherein particular materials and surface finishes can be selected
for use in the first and second friction surfaces 60 and 62, and
the biasing member 68 and its biasing force can be selected so as
to achieve the particular damping torque that is desired. An
example of a material that may, for some applications, be suitable
on the friction surface 62 of the friction member 64 is EkaGrip by
Ceradyne Inc. of Costa Mesa, Calif., USA. The prototype can then be
tested on a production engine and preferably in a production
vehicle to verify that is provides less than the maximum the
desired angular vibration on the hub 22.
[0079] It will be noted that the production decoupler 20 need not
be adjustable in terms of its damping force and damping torque.
[0080] The adjustable damping arrangement shown and described on
the test decoupler 100 may be applied to other types of decouplers,
such as those described in U.S. Pat. Nos. 5,156,573, 7,766,774,
7,153,227, 7,591,357, 7,624,852, all of which are incorporated
herein by reference in their entirety.
[0081] In some embodiments it may be possible to employ two or more
different types of biasing member together, such as, for example, a
Belleville washer in conjunction with (i.e. in series with or in
parallel with) either a single helical compression spring or
multiple helical compression springs.
[0082] Several other combinations and permutations would be
possible also, depending upon the packaging space available for the
pulley length and diameter.
[0083] While automotive alternator decoupler pulleys are sometimes
severely limited in both length and diameter due to underhood
packaging constraints, the invention may be applicable to much
larger engine applications, such as engines for buses, trucks,
military, commercial, construction and industrial engine
applications, which may be more tolerant to larger envelope
packages. Such engines may permit the larger configurations of the
biasing members 68 depicted in FIGS. 4, 5 and 6. Another solution
where space is limited may be to provide a hollow shaft for the
alternator, and to provide an inner shaft within an outer shaft for
the alternator. The outer shaft would be connected to the rotor of
the alternator. The pulley 24 would be fixedly mounted to the inner
shaft. The rest of the decoupler 20 would be provided to connect
the inner and outer shafts, at the opposite end of the alternator
to end with the pulley 24.
[0084] When manufacturing the decoupler 20, the position of the
retainer 69 impacts the biasing force exerted by the biasing member
68 on the friction member 64, which, as noted above, impacts the
damping torque provided by the friction surfaces 60 and 62. To
ensure that the retainer 69 is positioned in a suitable position so
that the desired damping torque is provided, the manufacture of the
decoupler 20 can entail:
[0085] a) providing an assembly comprising the hub 22, the friction
member 64, the thrust member 66 and the biasing member 68;
[0086] b) measuring the biasing force exerted by the biasing member
68;
[0087] c) compressing (or more generally, flexing) the biasing
member 68 to progressively increase the biasing force against the
friction member 64 until the measured biasing force reaches a
selected value; and
[0088] d) fixing the retainer 69 in position to maintain the amount
of flexure (compression) reached in step c).
[0089] Instead of measuring the biasing force and fixing the
retainer 69 when a selected force is reached, the process may
involve:
[0090] a) measuring the amount of compression or flexure in the
biasing member 68;
[0091] b) compressing it until a selected amount of
flexure/compression is reached; and
[0092] c) fixing the retainer 69 in position to maintain the amount
of flexure (compression) reached in step b).
[0093] Fixing the retainer 69 may be achieved, for example, by
staking the retainer 69 in place in the pulley 24, or by crimping a
lip of the pulley 24 into engagement with the retainer 69 to hold
the retainer 69 in place. Some types of biasing member may have
less sensitivity to small variations in their level of compression
(flexure) and so such steps may not be as beneficial. Sufficient
consistency from decoupler to decoupler may be achieved in such
cases by simply manufacturing them and inserting the retainer in a
pre-configured location (e.g. a slot that is milled into the pulley
24 before the biasing member 64 is inserted into the pulley 24
against the thrust member 66. While FIG. 3 shows such an
arrangement it is possible that the use of crimping or staking may
be preferable so as to provide high consistency in the biasing
force exerted by the Belleville washer 70.
[0094] It will be noted that any damping torque that is greater
than the selected torque would be sufficient to keep the
oscillations of the hub 22 sufficiently small so as to keep the
operating life of the isolation spring 28 above a desired limit.
However, it will be noted that as the damping torque increases, the
wear on the friction surfaces 60 and 62 increases, which could
impact their operating life, and the parasitic losses associated
with use of the decoupler 20 increase. Thus, it is beneficial to
keep the damping torque as close as possible to the selected
damping torque so as to achieve the intended operating life of the
spring 28 while minimizing the wear on the friction surfaces 60 and
62 and minimizing the parasitic losses associated with use of the
decoupler 20.
[0095] Reference is made to FIG. 10, which shows a decoupler 300 in
accordance with another embodiment of the present invention. The
decoupler 300 is capable of changing the amount of damping torque
that is applied between the pulley 24 and the hub 22. The decoupler
300 may be similar to the decoupler 20 shown in FIG. 4, for
example, employing the helical compression spring 72, or
alternatively it could be similar to the decoupler 20 shown in FIG.
5 or 6, or even the decoupler 20 shown in FIG. 3. The decoupler 300
includes, however, an actuator 302 that compresses (or more
generally, flexes) the biasing member 28 by a selectable amount.
The actuator 302, in the embodiment shown in FIG. 10 includes an
actuator drive 304 that is mounted to a fixed support member in the
vehicle, and a driven member 306 that is operatively engageable
with the biasing member 28 (e.g. by directly abutting the biasing
member 28). The driven member 306 may be a threaded member 308 that
engages a worm gear (not shown) that is rotated by a motor (not
shown) in the actuator drive 304. Rotation of the threaded member
308 selectably advances or retracts the threaded member 308 towards
and away from the biasing member 28, thereby providing infinite
adjustment capability of the biasing force of the biasing member 28
over a particular range of movement of the threaded member.
Adjusting the biasing force adjusts the damping torque applied
between the hub 22 and pulley 24. The actuator 302 can be
controlled to apply a high biasing force (and therefore a high
damping torque) in situations where the decoupler 300 is incurring
or is predicted to incur high torsional vibrations, and a low
biasing force (and therefore a lower damping torque) in all other
situations. In this way, a high damping torque is applied when
needed to prevent high stresses on the isolation spring 28, and a
low damping torque is applied in all other situations thereby
reducing parasitic losses associated with the decoupler 300.
[0096] The driven member 306 in this exemplary embodiment includes
the aforementioned threaded member 308, an end member 310, a
bearing 312 permitting relative rotation of the threaded member 308
and the end member 310, and an actuator thrust member 314 for
receiving the end member 310 and for transmitting the force exerted
by the end member 310 on the biasing member 68. A seal cap is not
shown in FIG. 10 so as not to obscure the other components of the
decoupler 300, however, as shown in FIG. 11, the seal cap 71 may be
provided, and includes a pass-through aperture 316 that seals
around the axially movable end member 310 so as to prevent the
entry of contaminants into the interior of the decoupler 300. Power
for the actuator drive 304 (i.e. for the motor) may be obtained
from any suitable source such as the vehicle battery (not shown) or
from the alternator itself.
[0097] The end member 310 may be configured at its tip to have
relatively low friction so as to inhibit heat buildup and damage to
it and to the thrust member 314 when they are engaged. It will be
noted that they may be engaged during high damping torque periods,
but they may be spaced from each other (i.e. the end member 310 may
be retracted from the thrust member 314 entirely during low damping
torque periods. A suitable tip treatment may be for example
providing a polymeric (e.g. nylon) spherical tip, or a spherical
tip that blends into a conical portion, as shown.
[0098] The actuators described herein may include electric motors
as described above. However, it is alternatively possible to
provide actuators that are pneumatic, hydraulic or powered by any
other suitable means. For example, it is possible to provide an
actuator that is a phase change actuator that is powered by causing
a phase change in a material, such as a wax or any other suitable
material. The expansion or contraction, (depending on whether the
material melted or solidified), changes the overall volume of the
material which is used to drive a member (e.g. a piston in a
cylinder housing) in one direction or another. Another type of
actuator is powered by a shape memory material such as a shape
memory alloy. Where the actuators are shape memory material or
phase change materials, electrical power may be used to drive their
actuation. In the case of phase change materials, the electrical
power may be used to heat them, for example. Where the actuators
are pneumatic, they may be vacuum actuators or positive pressure
actuators. They may use air bladders, pneumatic cylinders, or some
other suitable way of being operated. Any of these actuators may be
either linear actuators or rotary actuators.
[0099] It will be noted that some of the actuators described herein
provide infinite adjustability (e.g. actuator 302) as to the amount
of compression is provided on the biasing member 68. It is
alternatively possible to provide an actuator that is capable of as
few as two positions for a driven member, such as a linear or a
rotary solenoid, or a phase-change actuator. The two positions
would include a first position wherein the driven member causes the
biasing member 68 to exert a relatively high biasing force on the
friction member 64 so as to generate a high damping torque, and a
second position wherein the driven member causes the biasing member
68 to exert a relatively low biasing force on the friction member
64 so as to generate a low damping torque.
[0100] Reference is made to FIG. 12, which shows a decoupler 325
with a phase change actuator 323 that is positioned on the pulley
24 itself. In this embodiment, the pulley 24 has a support member
327 on it that holds the actuator 325. The actuator 323 itself may
be any suitable type of actuator, such as, for example, a phase
change actuator with a piston 328 and a cylinder 329 filled with a
phase change material, such as a suitable wax. The piston 328 would
thus constitute the driven member. Heating of the phase change
material would drive the piston 328 outward from the cylinder 329
to drive the thrust member 314 to compress the biasing member 68.
Cooling of the phase change material would permit the piston 328 to
be driven back into the cylinder 329 under the urging of the
biasing member 68. To heat the phase change material, electrical
power from some source (e.g. the vehicle's battery) would be
provided to a slip ring assembly 321 and transmitted therethrough
to a shaft 330 that extends from the back of the cylinder 329.
Power from this shaft is used to heat the phase change material
(e.g. via a resistive heating element).
[0101] While the actuator 302 permits the actuator drive 304 to be
mounted remotely from the pulley 24, it may be desirable due to
underhood packaging constraints to provide an actuator that permits
greater flexibility in the positioning of the drive. To address
this, an actuator could be provided wherein the driven member is a
push-pull cable, which slides within a sheath that has a free end
held by a bracket mounted in facing relationship to the thrust
member 314. The push-pull cable could be driven forward through the
sheath to push the thrust member 314 to compress the biasing member
68 and increase the damping torque. The push-pull cable could be
considered to be the driven member such an actuator. The actuator
drive itself could be made up of any suitable structure, such as a
solenoid having two or more positions that has the push-pull cable
connected thereto, or a motor and gear arrangement that has the
push-pull cable connected thereto.
[0102] The actuator 302 provides infinite adjustability as to the
amount of compression is provided on the biasing member 68. It is
alternatively possible to provide an actuator that is capable of as
few as two positions for a driven member, including a first
position wherein the driven member causes the biasing member 68 to
exert a relatively high biasing force on the friction member 64 so
as to generate a high damping torque, and a second position wherein
the driven member causes the biasing member 68 to exert a
relatively low biasing force on the friction member 64 so as to
generate a low damping torque. Such an actuator could be, for
example, a solenoid that is positionable in two or more positions.
The solenoid could be a linear solenoid or a rotary solenoid.
[0103] Where availability of room is a concern, the alternator
shaft itself could be a hollow shaft and a suitable drive could be
provided at the other end of the alternator shaft (i.e. the end
opposite to the end with the decoupler 20 on it) whereby a driven
member extends through the alternator shaft from the other end to
the end with the decoupler.
[0104] The controller 318 may be provided to control the operation
of any of the actuators described herein. Where controller 318 is
provided, it may optionally operate the actuator drive based on
open loop control. For example, the controller 318 may control the
actuator based on inputs such as engine speed, alternator status
(charging or not charging), and optionally the status of other
accessories driven by the belt 14 (FIG. 1). The controller 318 may
position the actuator in a low- or high-damping torque position
based on a lookup table with a map of the different combinations of
statuses and properties that are measured of the components of the
engine.
[0105] Alternatively, the controller 318 may optionally operate the
actuator drive based on closed loop control. For example, sensors
may be provided on several components to assist the controller 318
in determining whether the hub 22 is incurring or is about to incur
unacceptably large torsional vibrations. These sensors can be
positioned to detect such properties as belt flutter, crankshaft
torsional vibrations, hub torsional vibrations, and the like. When
the controller 318 detects that large torsional vibrations at the
hub 22 are imminent or are being incurred, the controller 318 can
operate the actuator to increase the damping torque. While
providing the high damping torque the controller 318 can continue
to monitor the sensor signals and can reduce the damping torque
when it detects that the belt system is stable and large torsional
vibrations are no longer imminent.
[0106] Suitable sensors can be used to detect the angular position
of a rotating object with high precision and thus could be used to
detect angular displacements of the hub 22 and pulley 24, and of
the crankshaft pulley. As noted above, a suitable sensor would be
the 2SA-10 Sentron sensor manufactured by Sentron AG, Baarerstrasse
73, 630O Zug, Switzerland. Such a sensor may be capable of sensing
angular displacement of the hub 22 by being positioned on the other
end of the alternator shaft 15 (i.e. the end opposite to the end on
which the decoupler is positioned), as shown in FIG. 10. The sensor
is shown at 319. The controller 318 would receive signals from
sensor 319.
[0107] Additionally, suitable sensors could be provided to detect
the angular position of a tensioner arm on a tensioner used to
tension the belt 14. An example of a suitable sensor for this
purpose is the KMZ41 sensor sold by Philips Semiconductor.
[0108] While the above description constitutes a plurality of
embodiments of the present invention, it will be appreciated that
the present invention is susceptible to further modification and
change without departing from the fair meaning of the accompanying
claims.
TABLE-US-00001 Listing of Elements Element Number FIG. Engine 10 1
Crankshaft 12 1 Pulley 13 1 Belt 14 1 Drive shaft 15 1 Accessories
16 1 Alternator 18 1 Decoupler 20 1 Hub 22 2 Pulley 24 2 First
bearing member 26 2 Second bearing member 27 2 Isolation spring 28
2 Carrier 30 2 One-way clutch 31 2 Wrap spring 32 2 Outer surface
40 2 Grooves 42 2 Inner surface 43 2 First (proximal) axial end 44
2 Second (distal) axial end 46 2 First helical end 50 3 First end
51 2 Driver wall 52 3 Second helical end 53 2 Radial wall 55 2
Sleeve 57 2 Coils 58 2 Second end 59 2 Thrust plate 73 2 First
friction surface 60 3 Second friction surface 62 3 Friction member
64 3 Thrust washer 66 3 Biasing member 68 3 Retainer member 69 3
Belleville washer 70 3 Seal cap 71 2 Helical compression spring 72
4 Compression springs 74 5 Biasing member 76 6 Curve 80 7a Peak 82
7a Peak 84 7a Curve 86 7b Peak 88 7b Peak 90 7b Test decoupler 100
8 Biasing member 102 8 Retainer 104 8 Threaded exterior surface 106
8 Threaded surface 107 8 Sensor 108 8 Sensor 110 8 Controller 111 8
Hub 122 8 Pulley 124 8 Bearing member 126 8 Bearing member 127 8
Isolation spring 128 8 Wrap spring 132 8 Sleeve 157 8 Friction
surface 160 8 Friction surface 162 8 Friction member 164 8 Thrust
member 166 8 Method step 201 9 Method step 202 9 Method step 204 9
Method step 206 9 Method step 208 9 Decoupler 300 10 Actuator 302
10 Actuator drive 304 10 Driven member 306 10 Threaded member 308
10 End member 310 10 Bearing 312 10 Thrust member 314 10
Pass-through aperture 316 11 Controller 318 11 Slip ring assembly
321 12 Decoupler 325 12 Phase change actuator 323 12 Support member
327 12 Piston 328 12 Cylinder 329 12 Shaft 330 12
* * * * *