is directed to systems and methods which provide a
solution to the problem of torsional spring rattle in accessory drive tuning devices such as
decouplers or isolator pulleys. The solution is designated a "spring lock" and utilizes
factional engagement. One method of achieving a "spring lock" comprises a spring
pocket adapted to wedgingly engage with a spring end. The pocket may have a wedgeshape
adapted so that the spring end wedges into the pocket when biased into the pocket.
[0004] In other embodiments, the spring end may be tapered for wedging into the
pocket. Both the pocket and spring end may be wedge shaped.
[0005] Another method of achieving a "spring lock" is to use an interference fit
between at least a portion of the spring inner or outer diameter and a corresponding
pocket surface as means of holding the spring in place.
[0006] One or both ends of the torsional spring may engage with associated
pockets. When both spring ends engage with their respective pockets, the same
embodiment or two different embodiments of frictionally engaging spring locks may be
utilized.
[0007] The foregoing has outlined rather broadly the features and technical
advantages of the present invention in order that the detailed description of the invention
that follows may be better understood. Additional features and advantages of the
invention will be described hereinafter which form the subject of the claims of the
invention. It should be appreciated by those skilled in the art that the conception and
specific embodiment disclosed may be readily utilized as a basis for modifying or
designing other structures for carrying out the same purposes of the present invention. It
should also be realized by those skilled in the art that such equivalent constructions do not
depart from the scope of the invention as set forth in the appended claims. The novel
features which are believed to be characteristic of the invention, both as to its
organization and method of operation, together with further objects and advantages will
be better understood from the following description when considered in connection with
the accompanying figures. It is to be expressly understood, however, that each of the
figures is provided for the purpose of illustration and description only and is not intended
as a definition of the limits of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The accompanying drawings, which are incorporated in and form part of the
specification in which like numerals designate like parts, illustrate embodiments of the
present invention and together with the description, serve to explain the principles of the
invention. In the drawings:
[0009] FIG. 1 is sectional view of a device according to an embodiment of the
invention;
[0010] FIG. 2 is a blow-up perspective view of the device of FIG. 1;
[0011] FIG. 3 is a plan view of a spring carrier with a wedge-shaped pocket;
[0012] FIG. 4 is a perspective view of a spring in the spring carrier of FIG. 3;
[0013] FIG. 5 illustrates mathematically how a wedge may be set;
[0014] FIG. 6 illustrates how a set wedge may resist release;
[0015] FIG. 7 illustrates mechanical and noise measurements on a device without a
spring lock feature;
[0016] FIG. 8 illustrates mechanical and noise measurements on a device with a
wedge-shaped spring lock feature according to an embodiment of the invention;
[0017] FIG. 9 is a section view of a device that uses an interference fit to the spring
inner diameter to hold the spring in place according to an embodiment of the invention;
[0018] FIG. 10 is an exploded view of the device of FIG. 9;
[0019] FIG. 11 shows a more detailed view of the pulley for the embodiment of
FIG. 9;
[0020] FIG. 12 shows a sectional view of the pulley of FIG. 11;
[0021] FIG. 13 shows a more detailed view of the clutch carrier for the embodiment
of FIG. 9;
[0022] FIG. 14 shows a sectional view of the clutch carrier of FIG. 13;
[0023] FIG. 15 is a section view of a device that uses an interference fit to the
spring outer diameter to hold the spring in place according to an embodiment of the
invention;
[0024] FIG. 16 shows a more detailed view of the pulley for the device of FIG. 15;
[0025] FIG. 17 shows a sectional view of the pulley of FIG. 16;
[0026] FIG. 18 shows a more detailed view of the clutch carrier for the device of
FIG. 15; and
[0027] FIG. 19 shows a sectional view of the clutch carrier of FIG. 18.
DETAILED DESCRIPTION
[0028] This invention relates to accessory drive tuning devices with torsion springs
for isolation angular vibrations. The device may or may not have a one-way clutch, but in
either case the torsional spring must be kept in position to prevent spring rattle. Spring
rattle occurs when the spring is allowed to slide in and out of its pocket. The speed
fluctuation resulting from the torsional vibration of a firing engine can cause the spring to
slide out in a clockwise and counter-clockwise direction relative to the rotating direction
of the pulley. The re-engagement of the spring can create a noise that would be
unacceptable to the customer. What is needed is a locking method to retain the end of the
torsional spring in its pocket. To make retaining of the spring end feasible for
manufacturing the locking method needs to be self engaging.
[0029] Generally, herein "isolator" is the spring function which provides relative
displacement, while being still connected, and "decoupler" is the clutch function which
provides an on or off connection. Also, generally "torsional vibration" refers to the
twisting of the crankshaft - which is generally controlled by a crank damper, and angular
vibration is the rigid body motion of the crank nose which effects the accessory belt drive
system ("ABDS"). An isolator decoupler preferably works on the crank angular vibration
input to the ABDS, for example, protecting the alternator, but generally not affecting the
crank torsional vibration.
[0030] FIG. 1 is a section view of one example of an accessory drive tuning device
100 according to an embodiment of the invention. FIG. is an exploded view of the
device 100 of FIG. 1. In FIG's 1 and 2, the torsional spring 4 is housed in pulley 5 and
spring carrier 6. FIG. 3 is a plan view of spring carrier 6 showing the spring pocket 610
with wedge taper 612. FIG. 4 is a perspective view of the spring 4 in the wedge in spring
carrier 6. A similar wedge-shaped pocket for the opposite end of spring 4 may be
included in pulley 5. FIG. 5 illustrates how the wedge is set in terms of the setting force
P, which biases the spring into the pocket, and the resulting wedging force Fy. FIG. 6
illustrates the resistance force R after it is set with the setting force P. The resistance
force will hold the spring from moving out of the wedge. If R is less than or equal to Fy,
then the spring will not pull free from the wedge. This condition results in Equation 1. If
Equation 1 is met then the wedge will be self locking and hold the spring in place.
[0031] Equation 1: m/tan Q > 1
[0032] q = Wedge angle
[0033] m = Coefficient of friction
[0034] The other parts of the exemplary device 100 of FIG' s 1 and 2 may be
described in more detail. Pulley 5 engages a belt (not shown) to drive a device such as an
alternator. Pulley 5 houses ball bearing 8 and needle bearing 3 which allow relative
motion between shaft 1 and pulley 5 while transferring the radial load to shaft 1. Pulley 5
is the input to the device and power flows from pulley 5 to one end of coil spring 4, then
from the other end of spring 4 to spring carrier 6. Pulley 5 and spring carrier 6 each have
a recess or pocket 610 machined therein with circular arc 6 11 to receive Spring 4. The
start of circular arc 6 11 has radial taper 612 to retain the spring. The angle of radial taper
612 is such that it is a self locking wedge. The end 614 of the pocket would be the stop
but for the wedge effect of taper 612. The device may include various covers, caps, seals,
spacers, reinforcing rings or the like, such as covers 9 and 2 and ring 7 in FIGs 1 and 2.
Other optional device features include one-way clutch 10.
[0035] To illustrate how the design works as shown in FIG. 3 the wedge angle as
shown is 5°. If we assume that pulley 5 and spring carrier 6 and spring 4 are made of
steel and assume that the steel surfaces are lubricated such that the coefficient of friction
is 0.15 then these conditions satisfy Equation 1 and the spring will stay in place unless it
is pulled out by some other greater force.
[0036] A prototype isolator decoupler with a torsional spring and with a spring
carrier with a wedge-shaped pocket machined therein to function as a stop and catch for
the spring end was constructed. The device included a one-way clutch device and was
constructed to test the invention. The spring rattling problem was solved in the prototype.
FIG's 7 and 8 show the noise, pulley speed, and rotor speed with and without the wedgeshaped
pocket. FIG. 7 is without the wedge-shaped pocket and FIG. 8 is with the wedgeshaped
pocket. Comparing the measured noise level (sound pressure in Pa) from both
FIG's 7 and 8 it is clear that there is less noise with the wedge-shaped pocket. Further
proof that the spring is not sliding out is the speed of the rotor. Both FIG's 7 and 8 have
the same input at the pulley and the rotor speed represents the output. The device with
the wedge-shaped pocket has a higher rotor speed in comparison to the device without the
wedge shaped pocket. The difference in speed is due to the spring sliding in and out of
the pocket only in the device without the wedge shaped pocket.
[0037] Either or both sides of the pocket could be angled to form the wedge. The
spring end could be tapered as well, but that is not necessary. The spring end could be
tapered or wedge-shaped instead of the pocket. An advantage of the invention is that it is
self-engaging and self-locking, so that if the forces increase so that a spring end
disengages, the engagement force will generally increase also to engage the spring end in
the wedge-shaped pocket even tighter than before it slipped out, thereby locking it in or
stabilizing it for the higher force level.
[0038] FIG. 9 is a section view of accessory drive tuning device 200 that illustrates
a second embodiment in which an interference fit to the spring inner diameter is used as a
means to hold the spring in place. FIG. 10 is an exploded view of device 200. In FIG's
9-10, parts numbered 1-3 and 7-10 are as described above for the first embodiment. As
shown in FIG's 9, 11 and 12, at least a portion of outer cylindrical surface 151 of pulley
15 is larger in diameter than inner diameter 141 of spring 14. This frictionally restrains
spring 14 from sliding out of spring pocket 152 of pulley 15 which is shown in FIG. 11.
The other end of spring 14 may be retained in a similar fashion. As shown in FIG's 9, 13
and 14, at least a portion of outer cylindrical surface 161 of clutch carrier 16 is larger in
diameter than spring inner diameter 142 of spring 14. This frictionally restrains spring 14
from sliding out of spring pocket 162 which is shown in FIG. 13.
[0039] FIG. 15 is a section view of accessory drive tuning device 300 that
illustrates a third embodiment where an interference fit to the spring outer diameter is
used as a means to hold the spring in place. As shown in FIG's 15 - 17, at least a portion
of inner cylindrical surface 251 of pulley 25 is smaller in diameter than outer diameter
241 of spring 24. This holds spring 24 from sliding out of spring pocket 252 of pulley 25
which is shown in FIG. 16. The other end of spring 24 may be retained in a similar
fashion or via one of the other embodiments described herein. As shown in FIG's 15, 18
and 19, at least a portion of inner cylindrical surface 261 of clutch carrier 26 is smaller in
diameter than spring outer diameter 242 of spring 24. This frictionally restrains spring 24
from sliding out of spring pocket 262 which is shown in FIG. 18.
[0040] Although the present invention and its advantages have been described in
detail, it should be understood that various changes, substitutions, and alterations can be
made herein without departing from the scope of the invention as defined by the
appended claims. Moreover, the scope of the present application is not intended to be
limited to the particular embodiments of the process, machine, manufacture, composition
of matter, means, methods, and steps described in the specification. As one of ordinary
skill in the art will readily appreciate from the disclosure of the present invention,
processes, machines, manufacture, compositions of matter, means, methods, or steps,
presently existing or later to be developed that perform substantially the same function or
achieve substantially the same result as the corresponding embodiments described herein
may be utilized according to the present invention. Accordingly, the appended claims are
intended to include within their scope such processes, machines, manufacture,
compositions of matter, means, methods, or steps. The invention disclosed herein may
suitably be practiced in the absence of any element that is not specifically disclosed
herein.

CLAIMS
claimed is:
An isolator decoupler comprising a torsional spring and a spring carrier with a
wedge-shaped pocket machined therein that engages an end of said torsional
spring.
The isolator decoupler of claim 1 wherein said engagement is by friction when
the end of said torsional spring is biased or wedged into said wedge-shaped
pocket.
The isolator decoupler of claim 2 wherein both ends of said torsional spring
engage in respective wedge-shaped pockets.
The isolator decoupler of claim 2 wherein the end of said torsional spring is
tapered.
An isolator decoupler comprising:
a torsional spring having a tapered end; and
a spring carrier with a pocket machined therein that engages said tapered end
of said torsional spring.
The isolator decoupler of claim 5 wherein said engagement is by friction when
the end of said torsional spring is biased or wedged into said pocket.
The isolator decoupler of claim 6 wherein both ends of said torsional spring
are tapered and engage in respective pockets.
The isolator decoupler of claim 6 wherein said pocket is wedge shaped.
An accessory drive tuning device comprising:
a torsional spring having a spring end; and
a spring carrier having a pocket arranged to accept said spring end;
wherein said spring end is frictionally restrained in said pocket.
The accessory drive tuning device of claim 9 wherein said factional restraint
is due to an interference fit between an outer cylindrical surface of said spring
carrier and the inner diameter of a portion of said torsional spring.
11. The accessory drive tuning device of claim 9 wherein said factional restraint
is due to an interference fit between an inner cylindrical surface of said spring
carrier and the outer diameter of a portion of said torsional spring.
12. The accessory drive tuning device of claim 9 wherein said factional restraint
is due to a wedging engagement between said spring end and said pocket.
13. The accessory drive tuning device of claim 1 wherein said spring end is
wedge shaped.
14. The accessory drive tuning device of claim 12 wherein said pocket is wedge
shaped.