Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02311075 2000-06-08
CANADA
Title: High-speed Overrunning, Instantaneous, Accessory Decoupler
Inventor: Pavel Babetin
!II
CA 02311075 2000-06-08
FIELD OF THE INVENTION:
The invention relates generally to multipurpose, minimal friction one-way
overrunning
clutches for use with serpentine belt driven components under high tension
often found in engines
in automotive applications.
BACKGROUND OF THE INVENTION:
Internal combustion engines incorporate belt systems and pulleys for
attachment to either
an engine crankshaft extension or to the drive spindle of an accessory. As
such, the accessories
are subject to the low speed oscillations of the engine caused by the inherent
pulsations of the
crankshaft spindle. The pistons of the engine, being forced down, cause the
crankshaft velocity to
fluctuate above and below a base level. In turn, the tension of the belt
driven by the crankshaft
spindle extension also fluctuates. Accessories are also subject to the sudden
decelerations of the
internal combustion engine of an automobile. These sudden decelerations often
occur during the
up shifts of the transmission where the engine speed is decreased.
When a sudden decrease in engine speed occurs, accessories, such as the
alternator and
other driven components, resist slowing down due to their rotational inertia.
Occasionally, this
can cause a loud "squeal" from the belt-pulley interface. This slippage causes
stress on the belt
and is also very annoying to drivers. In an attempt to remedy the problem,
designers of these
systems increased the tension of the belts at the cost of increased belt wear.
This countermeasure
also affected the accessories in that their output was forced to be
proportional to that of the
engine. Therefore, as the engine speed is decreased, so to is the output of
the accessories. Thus
the presence of an oscillatory component or a drive pulley that is inconstant
in its rotational
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velocity is detrimental to accessories and exposes conventional belt systems
to an increased stress.
There is an exigency for a device which can minimize the mooring of
oscillations to
accessories. There is a need for an arrangement which can eliminate "belt
squeal" and reduce the
loss of power provided by an accessory that is driven by an inconstant source.
SUMMARY OF THE INVENTION:
The present invention overcomes the drawbacks of the prior art by providing a
pulley
having a high speed clutch mechanism located in the hub of the circular pulley
which is
mechanically coupled to the accessory spindle. The circular pulley has a
peripheral edge
configured to engage the drive belt and a central hub opening. The hub opening
has a central
axis, an internal diameter, and an inside surface. An annular member is
coaxially and rigidly
mounted to the inside surface of the pulley hub opening, the annular member
having a central
opening with an inside diameter, a central axis and an inside surface.
Coaxially mounted within
the central opening of the annular member is a cylindrical member having a
first and second
opposite end portions and a central portion between the end portions. The
central portion of the
cylindrical member has an outside surface, an outside diameter and a plurality
of grooves equally
spaced along the circumference of the outside surface. Each groove is defined
by a first sloping
wall and a second sloping wall, the sloping walls being configured to retain a
roller bearing
between them. The outside diameter of the central portion of the cylindrical
member is slightly
less than the inside diameter of the annular member. The cylindrical member is
mechanically
coupled to the accessory spindle. A first bearing is mounted to the first end
portion of the
cylindrical member and a second bearing is mounted to the second end portion
of the cylindrical
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member. Both of the bearings are dimensioned and configured to position the
cylindrical member
at the center of the pulley hub with the annular member being positioned
between the bearings.
Furthermore, the bearings are also dimensioned so that the cylindrical member
does not touch the
annular member. Finally, the first and second sloping walls and the roller
bearings are all
dimensioned and configured to permit the cylindrical member to rotate freely
in a first direction
relative to the annular member, while preventing the annular member from
rotating in the first
direction relative to the cylindrical member.
Other objects and advantages of the invention will be evident from the
following detailed
description when read in conjunction with the accompanying drawings which
illustrate the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS:
FIGURE 1. is a schematic view of the present invention coupled to a motor.
FIGURE 2. is an exploded view of the present invention.
FIGURE 3. is a long sectional view of the invention.
1 S FIGURE 4. is a cross sectional view of the invention in its free wheeling
position.
FIGURE 4A is a cross sectional view of the clutch mechanism of the invention
in its free wheeling
position.
FIGURE 5. is a cross sectional view of the invention in its locking position.
FIGURE SA is a cross sectional view of the clutch mechanism of the invention
in its locking
position.
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DETAILED DESCRIPTION OF THE INVENTION:
The invention is a high rpm overrunning instantaneous accessory decoupler
which is
particularly useful for automobile internal combustion engines. As seen in
figure 1, a typical
automobile engine, shown generally as item 10, has a rotating fly wheel 12
which supplies power
to various accessories such as alternator 20 via a serpentine belt 14. As fly
wheel 12 rotates
serpentine belt 14 drives pulley 16 which in turn makes spindle 22 of
alternator 20 turn. In prior
art engines, a tensioner is provided between alternator 20 and fly wheel 12 in
order to maintain
the proper tension in belt 14. The present invention overcomes the drawbacks
of the prior art by
providing a high speed overrunning instantaneous decoupler in the form of hub
18 on pulley 16.
Hence, the present invention may be applied to existing engine systems merely
by replacing the
pulley hub.
Referring now to figure 2, the high speed overrunning instantaneous accessory
decoupler
consists of clutch assembly 15 mounted at the hub of pulley 28. Clutch
assembly 11 has a
cylindrical member 34 having elongated hub 36 and central ridge 38.
Cylindrical member 34 has a
plurality of grooves 42 equal distantly disposed along central ridge 38. Each
groove 42 is
dimensioned to retain roller 44. Cylindrical member 34 is dimensioned to fit
within opening 55 of
annular member 54. Cylindrical member 34 has an elongated hub 36 having
portions 46 and 50
located on either side of central ridge 38. Rollers 44 are secured within
grooves 42 by sealed
bearings 56 and 58 which are mounted to portions 46 and 50, respectively, of
hub 36. Clutch
assembly 11 is mounted within opening 32 of pulley 28. Angular member 54 has
clasp 52 which
permits the angular member to be rigidly mounted to pulley 28.
Refernng now to figure 3, clutch assembly 11 is mounted in pulley 28 such that
the clutch
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assembly acts as a hub for the pulley. Central ridge 38 of cylindrical member
34, rollers 44 and
annular member 54 form a decoupling mechanism, shown generally as item 15.
Decoupling
mechanism 15 is sealed between sealed bearings 56 and 58. By placing
decoupling mechanism 15
between sealed bearings 56 and 58, the bearings act to seal decoupling
mechanism 15 thereby
rendering the entire clutch assembly 11 maintenance free. If only one sealing
bearing were used,
then dirt and debris would eventually interfere with roller bearings 44. Given
the close tolerances
required for high speed applications, it is important that decoupling
mechanism 15 be as free from
contamination as possible. For high speed applications, it is also important
that clutch assembly
11 generate as little vibration as possible. By placing decoupling mechanism
15 between the
bearings, the amount of vibration clutch assembly 11 will generate is reduced.
Also, since central
ridge 38 and hub portions 46 and 50 are all part of cylindrical member 34,
then the vibration of
the entire assembly is further reduced.
Referring now to figures 4 and 4a, central ridge 38 of member 34 has a
plurality of
grooves 42 which extend parallel to central axis 40. Grooves 42 are defined by
first wall 60 and
second wall 62 which are formed in central ridge 38. The height of wall 62 is
defined as the
distance between top surface 39 of central ridge 38 and trough 61 which is the
deepest portion of
grooves 42. The height of wall 62 must be slightly greater than the diameter
of roller 44. Central
ridge 38 is mounted within opening 55 of angular member 54. The internal
diameter of opening
55 is slightly greater than the maximum outside diameter of central ridge 38
such that top surface
39 of the central ridge never contacts inside surface 57 of annular member 54.
When annular
member 54 begins to rotate faster than cylindrical member 34, roller bearings
44 are trapped
between sloping walls 60 and inside surface 57, which in turn forces member 34
to rotate along
CA 02311075 2000-06-08
with annular member 54. However, should annular member 54 slow down its
rotation relative to
cylindrical member 34, then roller bearings 44 make physical contact with
sloping walls 62 as
shown in figures 5 and SA. Since wall 62 is at an angle from ray 64, wall 62
exerts a centripetal
force onto roller bearing 44 which forces roller bearing 44 towards central
axis 40 and away from
annular member 54. Since the height of wall 62 is slightly greater than the
diameter of roller
bearings 44, the roller bearings do not then make contact with inner surface
57 of annular member
54 and cylindrical member 34 may rotate freely relative to annular member 54
in a clockwise
direction. It has been discovered that the angle at which wall 62 is
positioned relative to ray 64 is
critical for the proper operation of the decoupling device under high rmps. If
the angle between
wall 62 and ray 64 is too low, then wall 62 will not be able to exert
sufficient centripetal force on
roller bearing 44 to move it away from annular member 54. As a result, bearing
44 will contact
annular member 54 and cause the clutch mechanism to over heat. However, if
wall 62 at angled
too far away from ray 64, then roller bearing 44 will not engage inner surface
57 of annular
member 54 very quickly when the annular member rotates clockwise relative to
cylindrical
member 34.
It has been discovered that if wall 62 is angled approximately 30 degrees from
ray 64 then
roller bearings 44 will disengage from surface 57 almost instantaneously when
cylindrical member
34 begins to rotate quicker than angular member 54. In experimental trials, it
was discovered that
an angle of 20 degrees was insufficient since the roller bearings made
constant contact with the
annular member, causing the clutch mechanism to over heat and fail
prematurely.
The diameter of bearings 56 and 58 are selected so that surface 39 of central
ridge 38
never contacts inner surface 57 and annular member 54. When annular member 54
is rotating
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slower than cylindrical member 34, the bearings permit the cylindrical member
to rotate freely
with very little friction.
The present invention can be used with most any drive system, including V-
belt, poly V-
belt, timing belts, chains and gears. An added advantage of the design is
that, because accessories
can freewheel and slippage is no longer a concern, less surface area is
required on the pulley-belt
interface than the conventional 180°, and a tensioner is no longer
required. Because of the
reduced friction at the interface, pulleys can be made of less expensive and
lighter materials such
as aluminum and plastic. However, the greatest advantage of this specific
design is the very
minimal amount of friction.
Since the proposed clutch is implemented at the hub of the accessories drive
pulley, it has
no effect on what type of drive system is employed. Most any type of belt,
chain or gear system is
permissible as neither has an adverse affects. The clutches applications are
plentiful as its
instantaneous engagement renders it effective from 0 rpm to very high
revolutions, exceeding
20,000 rpm. The clutch produces no heat or vibration. The design also has high
torque and
shock capabilities.
The system which the design actuates is one that is both very versatile in the
lubrication
systems it is able to work in and is very efficient in providing very minimal
friction. Although the
clutch assembly can reside in an oil bath, providing a very stress reduced
environment, it is just as
effective when only bearing grease is utilized. Because the bearings are
sealed there is no
opportunity for leakage and maintenance is not required. These characteristics
ensure a long,
trouble free life.
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