U.S. patent number RE36,502 [Application Number 08/994,590] was granted by the patent office on 2000-01-18 for clutch ball ramp actuator with drive and coast apply.
This patent grant is currently assigned to Eaton Corporation. Invention is credited to David A. Janson, Gregory J. Organek, David M. Preston.
United States Patent |
RE36,502 |
Organek , et al. |
January 18, 2000 |
Clutch ball ramp actuator with drive and coast apply
Abstract
A first ball ramp actuator having a control ring acting with an
activation ring to supply an axial clutch clamping force in a
vehicle driving mode and a second ball ramp actuator using the
control ring acting with a clutch pressure plate to supply an axial
clutch clamping force in a vehicle coast mode where one side of a
one-way clutch is attached to the control ring and another side is
attached to a support bracket that is frictionally coupled to a
transmission input shaft to maintain an energized rotational
relationship with the activation ring when in the coast mode.
Inventors: |
Organek; Gregory J. (Detroit,
MI), Preston; David M. (Clarkston, MI), Janson; David
A. (Plymouth, MI) |
Assignee: |
Eaton Corporation (Cleveland,
OH)
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Family
ID: |
22697023 |
Appl.
No.: |
08/994,590 |
Filed: |
December 19, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
189366 |
Jan 31, 1994 |
05485904 |
Jan 23, 1996 |
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Current U.S.
Class: |
192/35; 192/40;
192/48.2; 192/48.92; 192/54.52; 192/84.1; 192/84.7; 192/93A |
Current CPC
Class: |
F16D
23/12 (20130101); F16D 27/112 (20130101); F16D
47/04 (20130101); F16D 27/004 (20130101); F16D
2023/123 (20130101) |
Current International
Class: |
F16D
23/00 (20060101); F16D 27/112 (20060101); F16D
47/00 (20060101); F16D 47/04 (20060101); F16D
23/12 (20060101); F16D 27/10 (20060101); F16D
013/04 (); F16D 027/112 (); F16D 043/20 () |
Field of
Search: |
;192/35,40,48.2,48.92,54.52,70.23,93A,84C,84.7,84.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bonck; Rodney H.
Attorney, Agent or Firm: Uthoff, Jr.; Loren H. Gordon;
Howard D.
Claims
We claim:
1. A ball ramp mechanism for coupling two rotating elements
comprising:
an input element driven by a prime mover and rotating about an axis
of rotation;
an output element having an axis of rotation coaxial with said axis
of rotation of said input element for rotating an output
device;
a first ball ramp actuator for generating an axial movement
comprising; an annular control ring adapted to be magnetically
coupled to said output element and to rotate therewith, said
control ring having at least two circumferential control ramps
formed in a first face of said control ring, said control ramps
varying in axial depth, an equivalent number of rolling elements
one occupying each of said ramps, an activation ring having an axis
of rotation along said axis of rotation of said control ring, said
activation ring having at least two activation ramps substantially
identical in number, shape and .[.a dial.]. .Iadd.radial
.Iaddend.position to said control ramps in said control ring where
said activation ramps at least partially oppose said control ramps
and where each of said rolling elements is trapped between said
activation ramp and a respective at least partially opposed control
ramp, said control ring axially and rotationally movably disposed
relative to said activation ring;
a second ball ramp actuator for generating an axial movement
wherein said activation ring has a plurality of opposite acting
circumferential activation coast ramps formed in a second face of
said activation ring and substantially identical partially opposed
plate ramps formed in a pressure plate where said plate ramps and
said coast ramps have a variable depth with an equivalent number of
rolling elements one occupying each pair of partially opposed ramps
which roll along said coast ramps and said plate ramps and operate
to axially displace the activation ring from the pressure plate
when rotated in a relative direction opposite to the direction of
rotation causing axial displacement of said first ball ramp
actuator;
coupling means for rotatably joining said input element to said
output element where said coupling means varies the degree of
rotational .[.Coupling.]. .Iadd.coupling .Iaddend.between said
input element and said output element according to the axial
position of said control ring relative to said activation ring,
said coupling means comprising: a flywheel attached to said input
element having a friction surface; a clutch disc having a first
friction surface for frictionally reacting against said flywheel
friction surface and a second friction surface; said pressure plate
having a friction surface for frictionally reacting against said
clutch disc second friction surface where said pressure plate is
nonrotatably connected to said flywheel;
a locking ring nonrotatably attached to said output element;
a control support element disposed between said control ring and
said locking ring, said control support rotatably supported by said
output element;
a coil for creating a magnetic field in said locking ring and said
control ring and said control support thereby magnetically joining
said control ring to said output element, .[.Said.]. .Iadd.said
.Iaddend.coil being electrically energized by a clutch control unit
where said activation ring rotates with said input element and said
control ring rotates with said output element according to said
control means;
control clutch means for limiting the rotation of said activation
ring relative to said control ring when said coil is energized,
said clutch means attached to said control support and to said
activation ring.
2. The ball ramp mechanism of claim 1, wherein said input element
comprises a flywheel and where said output element comprises a
transmission input shaft, said flywheel rotatably joined to said
coupling means.
3. The ball ramp mechanism of claim 1, wherein said coil is
attached to a transmission case.
4. The ball ramp mechanism of claim 1, wherein a friction pad is
mounted to said control support for frictionally contacting said
control ring and supplying a rotational torque thereto.
5. The ball ramp mechanism of claim 1, wherein said rolling
elements are spherically shaped.
6. A driveline clutch for coupling a flywheel to a transmission
input shaft comprising:
a flywheel rotated about an axis of rotation by a prime mover;
a driveline transmission having an input shaft and a housing;
a clutch disc splined to said input shaft radially extending from
said input shaft and having friction material on a first surface
and a second surface where said first surface frictionally engages
said flywheel;
a pressure plate encircling said input shaft having a first surface
for frictionally engaging said second surface of said clutch
disc;
a first ball ramp mechanism for moving said pressure plate toward
said clutch disc and said flywheel thereby causing said clutch disc
to be clamped therebetween comprising; an activation ring
encircling said input shaft, said activation ring being connected
to said pressure plate where axial movement of said activation ring
results in axial movement of said pressure plate; a control ring
encircling said input shaft and disposed adjacent to said
activation ring, said control ring and said activation ring having
opposed faces provided with circumferentially extending grooves,
arranged in at least three opposed pairs, said grooves having
portions of varying depth, and rolling members disposed one in each
opposed pair of grooves, the grooves on said activation ring and
said adjacent control ring being arranged so that relative angular
movement of said activation ring and said control ring in a drive
direction, from a starting position thereof, causes axial movement
of said activation ring away from said control ring and operating
to axially displace said adjacent pressure plate;
a second ball ramp mechanism for moving said pressure plate toward
said clutch disc and said flywheel thereby causing said clutch disc
to be clamped therebetween disposed between said pressure plate and
said activation ring, said pressure plate and said activation ring
having opposed faces provided with circumferentially extending
grooves arranged in at least three partially opposed pairs, said
grooves having portions of varying depth; and rolling members
disposed one in each opposed pair of grooves, the grooves on said
pressure plate and said adjacent activation ring being arranged so
that relative angular movement of said activation ring and said
pressure plate in an opposite drive direction, from a starting
position thereof, causes axial movement of said pressure plate
toward said clutch disc;
bearing means operative to absorb axial thrust loads from said
control ring, said bearing means reacting against said flywheel
through a support member;
a locking ring nonrotatably attached to said transmission input
shaft;
a control clutch having a first friction element attached to said
control ring and a second friction element nonrotatably attached to
said input shaft where upon application, said control clutch
frictionally couples said control ring to said input shaft;
a control support having a magnetic section disposed between said
control ring and said locking ring, said control support having a
control support extension section rotatably supported by said input
shaft;
a one-way clutch having one side attached to said activation ring
and a second side attached to said control support oriented to
prevent said activation ring from rotating with respect to said
control ring in a direction to release said ball ramp
mechanism;
a coil for inducing a magnetic field in said control ring, said
control support and said locking ring thereby magnetically coupling
said control ring to said transmission input shaft.
7. The driveline clutch of claim 6, wherein said control support
has a friction element attached to said magnetic section disposed
to frictionally engage said control ring upon energization of said
coil.
8. The driveline clutch of claim 6, wherein said rolling members
are spherical.
9. A driveline clutch employing a ball ramp actuator
comprising:
an input shaft rotatable about an axis of rotation;
an output shaft rotating about said axis of rotation;
a flywheel having a friction surface, said flywheel attached to
said input shaft and rotating therewith about said axis of
rotation;
a clutch disc having a first friction surface and a second friction
surface rotatable about said axis of rotation of said input shaft,
said first friction surface opposed to said flywheel friction
surface;
a pressure plate having a friction surface opposed to said second
friction surface of said clutch disc, said pressure plate rotatable
about said axis of rotation and nonrotatably connected to said
flywheel;
a first ball ramp actuator for axially displacing said pressure
plate toward said flywheel, said first ball ramp actuator
comprising a control ring and an activation ring having opposed
faces provided with circumferentially extending grooves, arranged
as at least three opposed pairs of grooves, including portions of
varying depth, and rolling members disposed one in each opposed
pair of grooves, said grooves on said activation ring and said
adjacent control ring being arranged so that relative angular
movement of said activation ring and said control ring in a first
direction, from a starting position thereof, causes axial movement
of said activation ring away from said control ring to move said
pressure plate toward said flywheel thereby clamping said clutch
disc, said actuation plate being linked to said pressure plate,
said coupling ring and said actuation ring being rotatable about
said axis of rotation;
a second ball ramp actuator for axially displacing said pressure
plate toward said flywheel, said second ball ramp actuator
comprising said activation ring and said pressure plate having
opposed faces provided with circumferentially extending grooves,
arranged as at least three opposed pairs of grooves, including
portions of varying depth, and rolling members disposed one in each
opposed pair of grooves, said grooves on said activation ring and
said adjacent pressure plate being arranged so that relative
angular movement of said activation ring and said pressure plate in
a second direction opposite to said first direction, from a
starting position thereof, causes axial movement of said pressure
plate away from said activation ring to move said pressure plate
toward said flywheel thereby clamping said clutch disc;
a locking ring nonrotatably attached to said output shaft;
a coil for inducing a magnetic field in said locking ring;
a one-way clutch having one side releasably coupled to said
transmission input shaft through said locking ring and a second
side attached to said activation ring for preventing relative
rotation of said activation ring and said control ring when said
coil is energized;
coupling means for linking said output shaft to said control
ring.
10. The driveline clutch of claim 9, wherein said coil is
electrically energized by an electronic clutch control unit.
11. The driveline clutch of claim 9, wherein said coupling means is
comprised of a control support having a magnetic section disposed
between said control ring and said locking ring and an extension
section rotatably attached to said transmission input shaft where
said magnetic section frictionally engages said locking ring and
rotates therewith when said coil is electrically energized.
12. The driveline clutch of claim 11, wherein a friction disc is
attached to said magnetic section where said friction disc contacts
and frictionally engages said control ring when said coil is
electrically energized.
Description
RELATED APPLICATIONS
This application is related to application U.S. Ser. No. 08/189,342
and filed on Jan. 31, 1994, and application U.S. Ser. No.
08/165,684 filed on Dec. 13, 1993, both assigned to the same
assignee, Eaton Corporation, as this application.
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle driveline clutch and
more particularly, to a driveline clutch where a friction disc is
clamped to an engine flywheel using a ball ramp actuator where a
one-way clutch is used to provide drive and coast driveline clutch
lock-up.
Driveline clutches commonly use a plurality of springs to clamp a
friction disc to an engine flywheel. The springs are disposed
within a pressure plate assembly which is bolted to the flywheel. A
mechanical linkage that controls the pressure plate spring
mechanism is displaced by the operator to control the lock-up and
release of the clutch.
Efforts to automate the operation of the clutch using electronics
are currently underway. It is known to use an electromechanical or
hydraulic actuator connected to the mechanical linkage to, in
essence, replace the operator for more accurate clutch operation
during transmission shifting. Using such an actuator, the
mechanical linkage is moved in response to an electrical control
signal generated by a central microprocessor used to process a
variety of vehicle sensor inputs and other operating conditions to
determine when and in what manner the driveline clutch should be
activated, or deactivated.
The use of a ball ramp actuator to load a clutch pack in a vehicle
driveline differential is known. U.S. Pat. Nos. 5,092,825 and
4,805,486, the disclosures of which are hereby incorporated by
reference, disclose limited slip differentials where a clutch pack
is loaded in response to the activation of a ball ramp actuator
initiated by rotation of a servo motor or a solenoid driven brake
shoe on an activating ring. The advantage of the ball ramp
mechanism over other actuators is that it converts rotary motion
into axial motion with a very high force amplification, often 100:1
or greater. A ball ramp actuator has also been utilized in a
vehicle transmission to engage and disengage gearsets by loading a
gear clutch pack in response to a signal as disclosed in U.S. Pat.
No. 5,078,249 the disclosure of which is hereby incorporated by
reference.
In both of these applications, one side of the ball ramp actuator,
commonly called a control ring, reacts against case ground through
the force induced by an electromagnetic field generated by a coil
or is rotated by an electric motor relative to case ground. To
generate greater clamping forces, the electrical current supplied
to the coil or motor is increased thereby increasing the reaction
of the control ring to case ground which rotates the control ring
relative to an activation ring thereby causing rolling elements to
engage ramps in the control and activation ring which increase the
axial movement and clamping force on the clutch pack.
One problem with the use of a ball ramp actuator to supply the
clutch clamping force is that the mechanics of prior art
unidirectional ball ramp mechanisms result in a loss of clamping
force when the vehicle is in a coast mode. Once the engine power is
reduced and the driveline is actually overrunning the engine (coast
mode), the prior art ball ramp actuator with single ramp
unidirectional actuation will disengage the clutch thereby
eliminating the potential for engine braking of the vehicle.
In other words, this type of prior art ball ramp actuated clutch
using a ball ramp having only a single ramp angle, will cause the
clutch to disengage when the engine is not supplying rotational
energy into the transmission when the vehicle is coasting. When
coasting, the flywheel is no longer supplying rotational energy to
either the transmission or the ball ramp actuator. In this
circumstance, the relative rotation of the activation ring and
control ring has been reversed such that the ball ramp axial
displacement is collapsed thereby allowing the pressure plate to
pull away from the clutch disc. The result is that the engine is
disengaged from the transmission and any engine braking effort is
eliminated.
The ball ramp actuator comprises a plurality of roller elements, a
control ring and an opposed activation ring where the activation
ring and the control ring define at least three opposed single ramp
surfaces formed as circumferential semi-circular grooves, each pair
of opposed grooves containing one roller element. A plurality of
thrust balls (or other type of thrust bearing) are interposed
between the control ring and a housing member, rotating with and
connected to the input member such as a flywheel. An
electromagnetic coil is disposed adjacent to one element of a
control clutch so as to induce a magnetic field that loads the
control clutch which in turn applies a force on the control ring of
the ball ramp actuator. The control clutch can be similar to those
commonly used for vehicle air conditioning compressors.
SUMMARY OF THE INVENTION
As an alternative, reference is made to an efficient, quick acting
ball ramp clutch actuator as disclosed in patent application Ser.
No. 08/165,684 filed on Dec. 13, 1993 having an attorney docket
number 93-RTRN-456. The ball ramp mechanism in the Ser. No.
08/165,684 disclosure has dual angle ramps where the clutch is
locked in both the drive and coast mode of vehicle operation. That
invention also provides for a ball ramp actuator for an
electronically controlled clutch such as might be used in a motor
vehicle. The present invention uses a ball ramp actuator having
single angle ramps which allow the outside diameter of the ball
ramp actuator to be significantly reduced.
The present invention is characterized by a flywheel and a
transmission input shaft being coupled through a control ring
having single direction variable depth grooves (ramps) and an
activation ring having single direction variable depth grooves at
least partially opposed to those of the control ring of a ball ramp
actuator where the activation ring is prevented from
counterrotating by a one-way clutch. An electromagnetic coil is
used to activate a control clutch which frictionally couples the
control ring to the transmission input shaft. The ball ramp
actuator provides a clamping force on the clutch friction disc
whose amplitude immediately increases with the differential speed
between the input (flywheel) and output (transmission) shafts
without complex electronic intervention using the coil. Upon
lock-up between the flywheel and the transmission input shaft, the
parasitic energy loss is minimized since there is no slippage in
the control clutch which is connected to the transmission input
shaft as opposed to case ground as found in prior art systems.
One provision of the present invention is to prevent a ball ramp
actuated clutch from disengaging when the input torque is
reversed.
Another provision of the present invention is to prevent a ball
ramp actuated clutch from disengaging by locking the rotational
orientation between a control ring arid an activation ring using a
one-way clutch when the driveline input is reversed.
Still another provision of the present invention is to prevent a
first ball ramp mechanism from disengaging when the driveline
torque is reversed by locking the rotational orientation between a
control ring and an activation ring and providing a ball ramp
mechanism between the control ring and a pressure plate which
energizes in a direction opposite to the first ball ramp
mechanism.
The present invention makes use of a one-way clutch defined for
purposes of this application as any mechanism which permits
rotation of an element in one direction and prevents substantial
rotation in an opposite direction. The purpose of the one-way
clutch as used in the ball ramp actuator of the present invention
is to hold the actuation ring in a fixed position relative to the
control ring so as to maintain the existing clamping force on the
clutch plate when the input torque is reversed such as in a vehicle
coast mode. Using a one-way clutch of the present invention allows
a clutch having a unidirectional ball ramp actuator with single
angle ramps (grooves) (which only applies a clamping load when the
control ring is rotated in one direction relative to the activation
ring) to apply a clutch clamping force when the engine is driving
or being driven. A bidirectional ball ramp actuator such as that
disclosed in U.S. Ser. No. 08/165,684 has dual angle ramps which
operate in either direction of rotation and a one-way clutch would
not serve any meaningful purpose other than prevent a momentary
clutch release upon a vehicle drive to coast transition.
With the use of a one-way clutch acting essentially between a
transmission input shaft and the actuation ring of a ball ramp
actuator having single angle grooves, the clamping force of a
clutch disc can be maintained as the input torque to the driveline
clutch is reversed. A second ball ramp mechanism with reverse
acting ramps can be used between the actuation ring and the
pressure plate: to provide an additional clamping force upon torque
reversal.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial cross-sectional view of the ball ramp actuator
of the present invention mounted to input and output members;
FIG. 2 is a front sectional view taken along line II--II of FIG. 1
of the activation ring, control ring and pressure plate of the ball
ramp actuator of the present invention:
FIG. 3 is a sectional view of FIG. 2 taken along line III--III of
FIG. 2 of the ball ramp actuator of the present invention with the
actuator in a non-energized state;
FIG. 4 is a sectional view of FIG. 2 taken along line III--III of
FIG. 2 of the ball ramp actuator of the present invention with the
actuator in an energized state; and
FIG. 5 is a sectional view of FIG. 2 taken along line III--III of
FIG. 2 of the ball ramp actuator of the present invention with both
the first and second ball ramp mechanisms energized.
DETAILED DESCRIPTION OR THE PREFERRED EMBODIMENT
Referring now to the drawings, which are not intended to limit the
present invention, FIG. 1 is a partial cross-sectional view of the
main driveline clutch assembly of the type in which the present
invention is utilized to energize a driveline clutch by supplying
an axial force to a pressure plate 12 which acts to clamp a clutch
disc 9 to an engine flywheel 4. Most all of the elements herein
described have circular peripheral edges and encircle the
transmission input shaft 8 and rotate on a common axis of rotation
59. FIG. 1 shows only a portion of the clutch assembly elements
which are symmetrical around the axis of rotation 59.
The engine flywheel 4 is rotatably driven by a prime mover (not
shown) such as an internal combustion engine through its crankshaft
(also not shown). The crankshaft rotates the flywheel 4 which is
coupled to a transmission 3 through the driveline clutch assembly
of the present invention by the clamping action of the pressure
plate 12 to the clutch disc 9 which rotatably drives the
transmission input shaft 8. A pressure plate 12 is used to clamp
the clutch disc 9 which is nonrotatably attached to the
transmission input shaft 8 through engagement of a plurality of
shaft splines 13 and mating clutch disc splines 11 through attached
friction pads 10 to the flywheel 4 thereby transferring the
rotational power from the engine to the transmission 3 and
subsequently to the rest of the vehicle driveline.
The pressure plate 12 is typically forced toward the flywheel 4
using a reaction of a plurality of high spring rate clutch springs.
When the operator wishes to disengage the clutch disc 9, a
mechanical release mechanism is activated by movement of the
operator's foot and leg thereby overcoming the force of the clutch
springs and allowing the clutch disc to slip relative to the
flywheel 4. It should be understood, that neither the clutch
springs nor the mechanical release mechanism are features of the
present invention. Instead, a first ball ramp actuator mechanism 5A
is used to axially force the pressure plate 12 toward the flywheel
4 which is controlled by clutch control electronics 15 which
controls most all of the transmission 3 shifting sequences.
Ball ramp mechanisms are well known in the art and have been used
to load transmission gear clutches as disclosed in U.S. Pat. No.
5,078,249, the disclosure of which is hereby incorporated by
reference, and differential clutch packs; as disclosed in U.S. Pat.
No. 5,092,825, the disclosure which is incorporated by reference.
In the prior art, the ball ramp control mechanism is energized
through a reaction of a control ring against case ground by an
electrical coil or motor. The detailed operation of the ball ramp
actuator 5 is disclosed in U.S. Pat. No. 5,078,249 and U.S. Pat.
No. 5,092,825.
In essence, relative motion between a control ring 16 and an
activation ring 18 being driven through the pressure plate 12 by
the second ball ramp mechanism 5B which is locked by its geometry
causes one or more rolling elements 20A (which can be spherically
shaped or barrel shaped in addition to other designs) to roll along
a like number of opposed ramps 22A and 23A formed in the control
ring 16 and the activation ring 18. FIG. 2 illustrates this
geometry with more detail and precision, reference to which is made
subsequently.
Referring once again to FIG. 1, the annular control ring 16 is
axially loaded by the first ball ramp mechanism 5A and reacts
against a thrust bearing 27 which is trapped between the control
ring 16 and a mechanism support member 34 which is attached to the
flywheel 4. The support bearing 27 provides for axial support of
the control ring 16 while allowing for relative rotation with
respect to the support member 34.
The control ring 16 is frictionally coupled to the transmission
input shaft 8 through the action of an energizing coil 30 which
causes the control ring 16 to be axially loaded against a friction
element 28 thereby completing the coupling arrangement to the
transmission input shaft 8. The coil 30 is electrically energized
using a clutch control unit 15 which in turn can be controlled by a
vehicle system electronic control unit (not shown). The electrical
current is introduced into the coil 30 by the clutch control unit
15 where the electrical current in the coil 30 creates a magnetic
field 36 which flows through a narrow air gap 35 through the
control support 37 (specifically the magnetic section 37B) through
the locking ring 32 into the control ring 16 and then returning to
the coil 30 in a circular manner. The coil 30 creates the magnetic
field 36 which provides electromagnetic coupling of the control
ring 16 to the locking ring 32 through the friction element 28 and
control support magnetic section 37B and functions to frictionally
couple the control ring 16 to the transmission input shaft 8. The
coil 30 is mounted to case ground through support bracket 31 which
is attached to the case of the transmission 3. The narrow air gap
35 exists between the coil 30 and the locking ring 32 since the
coil 30 is grounded and the locking ring 32 rotates with the
transmission input shaft 8.
A control support extension section 37A (which is joined to the
magnetic section 37B to form the control support 37) supports one
side of a one-way clutch 38. A second side of the one-way clutch 38
is mounted to the activation ring 18. The purpose of the one-way
clutch 38 is to prevent relative rotation between the control ring
16 and the activation ring 18 so as to maintain the position of the
first ball ramp mechanism 5A such that the coupling between the
flywheel 4 and the transmission input shaft 8 is maintained in any
vehicle operating mode such as drive or coast and in addition
serves to drive the second ball ramp mechanism 5B in coast mode. In
this manner, the engine can act as a brake to slow the vehicle when
in a vehicle coast mode since the ball ramp actuator remains in the
energized state by operation of the one-way clutch 38. In the prior
art, the ball ramp clutch mechanism with a one-way ramp would
disengage the clutch whenever the rotational torque is reversed
such as in the vehicle coast mode.
The one-way clutch 38 functions to lock the activation ring 18 to
the control support extension 37A which is connected to the
magnetic section 37B to form the control support 37 which is in
turn rotatably supported by the transmission input shaft 8. Bushing
39 surrounds the transmission main shaft 8 and serves to rotatably
support the control support 37 at the control support extension
37A. Thus, unless the coil 30 is energized, the control support 37
is free to rotate thereby allowing the one-way clutch to rotate
with the control ring 16 so that the control ring 16 and the
activation ring 18 are free to assume a non-energized rotational
orientation.
In normal operation, when the engine is powering the vehicle
driveline through rotation of its flywheel 4 then through the ball
ramp clutch assembly 2, the one-way clutch 38 is free to allow
motion in one direction between the activation ring 18 and control
ring 16 which further clamps the pressure plate 12. The one-way
clutch 38 does not permit the relative rotation of the control ring
18 relative to the activation ring 16 so as to reduce the clamping
force on the clutch disc 9 so long as the coil 30 is energized to
magnetically connect the control support 37 through its magnetic
section 37B to the transmission input shaft 8 through the locking
ring 32. The clutch disc 9 is clamped between the pressure plate 12
and the flywheel 4 and is composed of a plurality of friction
plates 10 and a spline 11 which slidingly and nonrotatably engages
the transmission input shaft 8 through splines 13 thereby
completing the torque transfer path.
When the vehicle is in a coast mode, where the driveline is
powering the engine, the; one-way clutch 38 locks the activation
ring 18 to the locking ring 32 through the control support
extension 37A where the coil 30, if energized, is also functioning
to frictionally lock the control ring 16 to the locking ring 32,
and locking ring 32 is splined to input shaft 8 and in turn
supplies coast torque to ball ramp mechanism 5B to activate and
supply a clamping force to the clutch disc 9, thereby maintaining
the relative rotational orientation between the control ring 16,
the activation ring 18 and input shaft 8. The result is that the
clamping force supplied by the control ring 18 and the activation
ring 16 is maintained at its current level and additional clamping
is provided whenever the vehicle goes into a coast mode such that
the transmission input shaft 8 transfers power to the engine
flywheel 4.
To further clamp the clutch disc 9 between the flywheel 4 and the
pressure plate 12 in the coast mode where the driveline is rotating
the engine, the second ball ramp mechanism 5B is energized in the
opposite rotational direction to the first ball ramp mechanism 5A.
The second ball ramp mechanism 5B does not provide for relative
movement between the activation ring 18 and the pressure plate 12
when the engine is powering the vehicle. When the torque transfer
is reversed in the vehicle coast mode, the activation rings rotate
through a small angle relative to the pressure plate 12 thereby
causing a plurality of rolling elements 26A, 26B and 26C to travel
along opposing ramps 24A and 25A, 24B and 25B, and 24C and 25C
respectively which causes the second ball ramp mechanism 5B to
expand axially thereby supply additional clamping force to the
clutch disc 9.
The pressure plate 12 is nonrotatably coupled to the engine
flywheel 4 by way of a retaining bolt 40 where the pressure plate
12 is slidably connected to the retaining bolt 40 and is forced
away from the flywheel 4 by the return spring 42. In this manner,
when the first and second ball ramp mechanisms 5A and 5B are in a
non-energized state, the return spring 42 forces the pressure plate
12 away from the flywheel 4 thereby releasing the clutch disc 9 so
that the engine flywheel 4 can freely rotate relative to the
transmission input shaft 8 and no torque is transferred through the
clutch assembly. A bellhousing 6 surrounds the flywheel 4 and the
ball ramp clutch assembly 2 where it is common practice to bolt the
transmission 3 to the bellhousing 6.
Now referring to FIGS. 2, 3, 4 and 5, the control ring 16 is shaped
in a disc configuration surrounding the transmission input shaft 8
and rotating about a common axis of rotation 59. The control ring
16 has a plurality of radial grooves 22A, 22B and 22C formed
therein which vary in axial depth along their length. Grooves 22A,
22B and 22C are shown in more detail by reference to FIGS. 3, 4 and
5 and constrain spherical elements 20A, 20B and 20C. In a similar
manner, activation ring 18 contains a like number and orientation
of circumferentially extending (at a constant radius to the axis of
rotation 59) grooves directly opposing the grooves in the control
ring. Specifically, control ring groove 22A is partially opposed to
activation ring groove 23A when the ball ramp mechanism 5 is in a
non-energized state as shown in FIG. 3 and directly opposes the
activation ring groove 23A when in a fully energized state (not
shown).
Upon relative rotational motion between the control ring 16 and the
activation ring 18, the spherical element 20A rolls relative to the
control ring groove 22A and activation control ring groove 23A
where the variable depth of the grooves 22A and 23A as shown in
FIG. 4 provide for an axial motion that tends to separate the
control ring 16 from the activation ring 18. This axial motion is
shown by reference to the separation gap 44. In the non-energized
state as shown in FIG. 3, the separation gap 44 is relatively
narrow and after relative rotation of the control ring 16 and the
activation ring 18 to the energized state shown in FIG. 4, the
separation gap is significantly wider as discussed infra.
The axial motion supplied by the first and second ball ramp
mechanisms 5A and 5B are used to axially move the pressure plate 12
toward the flywheel 4 thereby supplying a clamping force on the
clutch disc 9. This motion is more clearly exemplified in FIGS. 3,
4 and 5 and reference thereto will now be made. FIGS. 3, 4 and 5
are sectional views of FIG. 2 taken along line III--III of the
control ring 16 and the activation ring 18 and the pressure plate
12 of the present invention. FIG. 3 shows the first ball ramp
mechanism 5A in a non-energized state where the spherical element
20A is located at the deepest depth of the control ring groove 22A
and the deepest portion of the activation ring groove 23A thereby
establishing a relatively narrow separation gap 44 between the
control ring 16 and the activation ring 18. Also shown is the
second ball ramp mechanism 5B between the activation ring 18 and
the pressure plate 12 where spherical element 26A is located in the
deepest portion of the activation ring groove 24A and the deepest
portion of the pressure plate groove 25A thereby establishing a
relatively narrow separation gap 46.
FIG. 4 illustrates the relationship between the control ring 16,
the activation ring 18 and the pressure plate 12 when the first
ball ramp mechanism 5A is energized by supplying electrical current
to the coil 30 from the clutch control unit 15 and the engine is
supplying torque to the driveline. The magnetic interaction between
the coil 30, the locking ring 32, the control support 37 and the
control ring 16 causes the friction element 28 to contact and
frictionally connect the control ring 16 to the transmission input
shaft 8. Thus, since the pressure plate 12 is rotating and attached
to the engine flywheel 4, and ball ramp mechanism 5B cannot rotate
in an engine drive direction, if there is relative rotational speed
differences between the engine flywheel 4 and the transmission
input shaft 8 there is relative rotational motion induced between
the pressure plate 12 and the control ring 16. This relative
rotational motion causes the control ring 16 to rotate relative to
the activation ring 18 to establish a geometrical relationship as
shown in FIG. 4. The separation gap 44 is significantly increased
as compared to the non-energized state of FIG. 3 while the
separation gap 46 remains the same as in the, non-energized state
in FIG. 3 since the second ball ramp mechanism 5B is locked until
the torque is reversed. The spherical element 20A has rolled along
both the control ring groove 22A and the activation ring groove 23A
to an intermediate depth of the grooves 22A and 23A thereby further
separating the control ring 16 from the activation ring 18 and
providing axial movement from the support member 34 as shown by the
increase in the separation gap 44 which is transferred to the
pressure plate 12 for clamping of the clutch disc 9 to the flywheel
4.
To provide engine braking effect in the vehicle coast operating
mode, the coil 30 remains energized and the one-way clutch 38
operates against the control support 37 to prevent the first ball
ramp mechanism 5A from releasing. The second ball ramp mechanism 5B
has a reversed direction ramp orientation between the activation
ring 18 and the pressure plate 12 so that reverse torque transfer
results in activation of the second ball ramp actuator 5B thereby
increasing the clamping force of the pressure plate 12 on the
clutch disc 9. Referring to FIG. 5, spherical element 26A has
rolled along activation ring groove 24A and pressure plate groove
25A (also referred to as plate grooves) to an intermediate depth of
the grooves 24A and 25A thereby increasing the separation gap 46 as
compared to that shown in FIGS. 3 and 4. The result is that
additional axial motion is applied to the pressure plate 12
relative to the engine flywheel 4 and the support member 34 which
clamps the clutch disc 9 between the pressure plate 12 and the
engine flywheel 4 thereby frictionally connecting the flywheel 4 to
the transmission input shaft 8.
According to the present invention, once the clutch assembly 2 is
engaged by action of either the first ball ramp actuator 5A or the
second ball ramp actuator 5B, the engine can supply power to the
vehicle driveline thereby propelling the vehicle. When it is no
longer desirable to increase the speed of the vehicle by supplying
power from the engine to the driveline, the engine power is
decreased and the engine can act as a brake to the vehicle by
reversing the flow of rotational power from the engine to the
driveline to one flowing from the driveline to tile engine. The
one-way clutch 38 serves to maintain the relative rotational
position of the activation ring 18 relative to the control ring 16
and the pressure plate 12 thereby maintaining the clamping force
between the pressure plate 12 and the flywheel 4 to maintain the
frictional coupling between the transmission input shaft 8 and the
flywheel 4 so that the driveline can supply rotational power to the
engine which, if the engine throttle is closed, will tend to brake
the vehicle. An additional clamping force can be supplied by a
second ball ramp mechanism 5B placed between the activation ring 18
and the pressure plate 12 designed to energize when the torque flow
reverses as during vehicle coasting.
This invention has been described in great detail, sufficient to
enable one skilled in the art to make and use the same. Various
alterations and modifications of the invention will occur to those
skilled in the art upon the reading and understanding of the
foregoing specification, and it is intended to include all such
alterations and modifications as part of the invention, insofar as
they come within the scope of the intended claims.
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