CA2146482A1 - Clutch ball ramp actuator with a mechanically released control clutch - Google Patents

Abstract

A mechanical release system for a ball ramp actuator is disclosed where the ball ramp actuator generates a clamping force on a driveline clutch when a control ring is rotated relative to an activation ring thereby causing a rolling element to traverse a pair of opposed ramps to axially expand the separation between the control ring and the activation ring to generate the clamping force. The ball ramp actuator is axially contracted and the driveline clutch is released using a relatively low release force level when the driver causing a rotation of a release arm which contacts a release bearing thereby causing a rotatable connected stop ring to axially move and release a control clutch which when engaged, frictionally connects the control ring to the transmission input shaft. A clamping spring acting upon the stop ring and a drive ring thereby supplying a clamping load on a control disc between the drive ring and a control collar within the control clutch thereby engaging the ball ramp actuator and the driveline clutch.

Description

2146~2 93-rTRN-459 CLUTCH BALL RAMP ACTUATOR WITH A
MECHANICALLY RELEASED CONTROL CLUTCH

RELATED APPLICATIONS
This application is related to USSN 08/165,684 entitled "Ball Ramp Mechanism For A Driveline Clutch" filed on December 13, 1993 and assigned to the same assignee, Eaton Corporation, as this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention The present invention relates to a ball ramp ~ctua~or with a 10 mechanically operated control clutch and more specifically, to a ball ramp actu~tor having a mechanically operated control clutch loaded with a clamping spring which is released by action of a control arm.

2. Descri,ulion of the Prior Art Driveline clutches co,nmoi1ly use a plurality of high rate 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 conl,ols the pressure plate spring mechanism is displaced by the vehicle driver operator by pressing on a clutch pedal so as to control the lock-20 up and release of the clutch.
USSN: 08/165,684 the disclosure of which is hereby incorporated by rererence, describes the use of a ball ramp actuator to supply the axial clamping force on a clutch disc where the position of the ball ramp mechanism is controlled by the electromagnetic force ge"erated by a coil on a control 25 clutch. The operation of the clutch depends in a large part on the clutch control electronic algorithm and its ability to properly energize the coil for the desired clutch engagement and disengagement.
In general, it is complicated to automate the operation of a driveline clutch, especially during start-up of the vehicle. An electronic 30 aulol"aled clutch system is complicated and expensive in one part due to the 214~4~
`` , number of sensors required to provide inputs to a clutch control electronic package. Another problem with the prior art is that speed sensors are required to measure among other parameters flywheel speed and transmission input shaft speed and a microprocessor is required to rapidly interpret these speed 5 signals calculate a slip speed and then ye"erale a control signal to the coil to increase the axial lock-up force of the ball ramp ~ctua~or should slip occur through the driveline clutch. This approach is slow and excessive slip can occur before action is taken to increase the clamping force. Excessive slip wears out the clutch prematurely.
A siyl,iricant disadvantage of a nonautomated mechanical system as described above, is that the force required by the driver to release the maindriveline clutch is quite high since the engagement springs must provide a relatively high clamping load on the clutch which must then be released by the force generated through the driver s leg. These high force levels required to 15 release the clutch result in driver fatigue, especially in heavy traffic.

SUMMARY OF THE INVENTION
The presenl invention is directed to a release mechanism for a driveline clutch ball ramp ~ctu~tor that supplies a clamping force to a main 20 driveline clutch disc. The ball ramp ~ctl l~tor is normally engaged and utilizes a clamping spring to load a control clutch which drives a control ring of the ball ramp mechanism. The normal position of the ball ramp mecl,ai,is", with the spring loaded control clutch is axially extended so as to cause engagement of the driveline clutch. When it is desired ~o disenyaye the driveline clutch, a 25 mechanical motion is supplied by the vehicle operator/driver which causes thecontrol clutch to disengage thereby allowing the ball ramp mecl ~"isl " to axially contract and release the driveline clutch disc. Various mechanical links from the driver to the clutch system can be used to supply the disengagement motion to the control clutch since the force level required to disengage the 30 driveline clutch has been significantly reduced using the present invention.
One provision of the present invention is to provide a mechanical clutch disengagement system having a low release force requirement.

21~4~2 Another provision of the present invention is to provide a mechanical clutch release system having a low clutch release force requirement using a ball ramp ~ct(l~tor.
Another provision of the present invention is to provide a 5mechanical clutch release system having a low clutch release force requirement using a mechanically gei16r~led control clutch load for activation of a ball ramp mecl ,a"isrn to cause engagement of a driveline clutch.
Still another provision of the present invention is to provide a mecl ,an c~! clutch control system having a low clutch release force requirement10using a spring loaded control clutch to energize a ball ramp mechanism to supply a clamlJing force to a driveline clutch.
The present invention provides for the low force mechanical release of a driveline clutch by the driver utilizing a ball ramp mechanism to generate the high disc clamping force and a rotating arm to axially I;spl~ce a 15portion of a spring loaded control clutch so as to control the engagement and ~isengagement of the ball ramp mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial cross se~ional view of the ball ramp actu~tor 20utilizing the control clutch and release mechanis", of the present invention;
FIG. 2 is a cross sectional view of the ball ramp ~ctll~tor of the ~,resent invention as shown in Figure 1 taken along line ll-ll;
FIG. 3 is a cross sectional view of the ball ramp mecl ,an;s", of the present invention as shown in Figure 1 taken along line lll-lll;
25FIG. 4 is a cross sectional view of the ball ramp mechanism of the present invention in a nonei~er~ d state taken along line IV-IV of Figure 3; andFIG. 5 is a cross sectional view of the ball ramp mechanism of the ~.r~sent invention in an energized state taken along line IV-IV of Figure 3.

Referring now to the drawings which are not intended to limit the present invention. Figure 1 is an axial cross-sectional view of a main driveline 2146~8~
-clutch system 2 including the ball ramp mechanism 14 to supply a clamping force to a driveline clutch assembly 5 which utilizes a control clutch 25 which incorporates the mechanical release meci,anis~ 15 of the present invention.
The main driveline clutch system 2 includes a flywheel 4 rotatably 5 driven by a prime mover (not shown) such as an inlernal combustion engine by its output crankshaft (not shown) which is coupled to a tra~s,nission 3 by a clutch assembly 5. A bellhousing 6 surrounds the flywheel 4 and supports the l,a,)sinission 3 including the lrans",ission input shaft 8 which extends to nonrot~tably engage a clutch disc 9 through a drive spline 13 engaging mating 10 splines 7 formed in the l,ansr"ission shaft 8. A pressure plate 12 is used toclamp the clutch disc 9 through attached friction pads 10 to the flywheel 4 thereby l,ans~er,iny the rotational power from the prime mover to the l,~"s",ission 3 through a lfansr":ssion input shaft 8 and eventually to the restof the vehicle driveline.
The pressure plate 12 is con,monly forced toward the flywheel 4 using a plurality of springs having a high spring rate. When the operator wishes to disengage the clutch disc 9, a mechanical release mechanis", is activated by the operator s pushing of a clutch pedal to overcome the force of the high rate springs thereby allowing the clutch disc 9 to slip relative to theflywheel 4. It should be understood, however, that neither the traditional high rate clutch springs nor the l~aditiGI)al heavy duty clutch telease mechanis") are features of the present invention. According to the presenl invention a ball ramp ,necl,an;sm 14 is utilized to force the pressure plate 12 toward the flywheel 4 which is disengaged by a driver ~ ted release mechanism 15 operating on a control clutch 25 which regu~ates the activation of the ball rampmec~,a";sm 14.
Ball ramp mecl ,anis",s are well known in the art and have been used to load l,ans",issiol, gear clutches as des~ibed in U.S. Patent No.
5078249 and dir~erenlial clutch packs as described in U.S. Patent No.
5 09~ 8~5 the disclosures of which are hereby expressly incorporated by reference. In these disclosures the ball ramp control ring is reacted against case ground by a coil or motor. RaCic~lly the ball ramp mechanism 14 214648~
-operates when relative motion between a control ring 16 and an activation ring 18 induced by the operation of the control clutch 25 causes one or more rolling elements 20A which can be traditional spherical type bearing elements held in relative position by a bearing cage (not shown) to be moved along a like 5 number of opposed ramps 22A and 23A formed in both the control ring 16 and the activation ring 18 respectively thereby axially increasing the separation distance between the control ring 16 and the activation ring 18. The activation ring 18 is no,1rotdlably ioined to the pressure plate 12 using a plurality of bolts 42 which have a smooth shoulder portion which allows the actuation ring 18 to axially slide toward and away from the pressure plate 12 as forced within the ball ramp mecl,a"is"~ 14. Figures 3-5 illustrate this geometry with more detail and precision rererence to which is made subsequently.
Thrust ~earing 24 has a plurality of thrust elements (which can be any type of thrust bearing) and is used to contain the axial forces generated byone or more ball ramp rolling elements 20A as they engage the ramps 22A and 23A in the activation ring 18 and the control ring 16 respectively. Axial forcesgenerated by the ball ramp ~Gtu~tor 14 are trans,nilled by the thrust elements 24 rolling in semi-circular thrust channels 60 formed into the thrust ring 19 and the control ring 16 which is also grooved to accept the thrust elements 24. The thrust ring 19 is attached to the plate exle~)sio" 17 which is bolted to the clutch housing 11 which is in turn bolted to the flywheel 4. In the opposite d;reclion,the force generated by the ball ramp ~ctuator 14 is transmitted to the Belville spring 40 into the pressure plate 12. Rotation of the control ring 16 relative to the activation ring 18 causes the activation ring 18 to move axially toward the flywheel 4 thereby causing the clutch disc 9 to be clamped between the pressure plate 12 and the flywheel 4 which effectively rolala~ly connects the flywheel 4 to the lrans",issiGn input shaft 8 (also known as an output shaft).
The Belville spring 40 is interposed between the activation ring 18 and the pressure`plate 12 where a smooth shank on pilot bolt 42 allows the pressure plate 12 to slide but not rotate relative to the activation ring 18. As an alternative to the Belville spring 40 any type of spring inducing the proper separation force could be utilized. The activation ring 18 axially loads the 2146~82 -pressure plate 12 through the Belville spring 40 so that its compliance functions to cushion any shock loads thereby preventing high loading of the ball ramp rolling elements 20A. The ball ramp mechanism 14 is mounted to the flywheel 4 through the ball ramp thrust ring 19 which is attached to the plate extension 17 which is in turn bolted to the clutch housing 11 which is bolted to the flywheel 4.
The centering spring 44 functions to control the position of the control ring 16 relative to the activation ring 18 when the control clutch 25 is not e,)eryi~ed such that verv little torque is applied through the ball ramp actl l~tor 10 14 especially when the engine is rapidly accelerated with the clutch asse"~bly 5 disengaged by unloading a control disc 28 of the control clutch 25 which unloads the ball ramp mecl,anis", 14. The cen~eri,lg spring 44 is shown as a tGr:jional tvpe spring which is reslrai,led in the clockwise direction by the clockwise retention pin 44A or similarly in the counterclockwise direction by the 15 co~ erclockwise rel~,ltion pin 44B. The cenleri"~a spring 44 is sl,essed by movement of the ball ramp tab ring 52, which is indirectly attached to the control ring 16 and the control clutch 25 as it moves relative to the activationtab ring 50 which is attached to the activation ring 18. When the ball ramp tab ring 52 moves in a clockwise direction the clockwise retention pin 44A conlac~
20 the oprosite side of the activation tab ring 50 causing the centering spring 44 to be ~t, essed and to generate a ce~ Iteri, ly force between the activation ring 18 and the control ring 16 that tends to return them to an orientation where no axial force is yeneraled by the ball ramp ~ctu~tor 14. Likewise when the ball ramp tab ring 52 moves in a counterclockwise direction the counlerclockwise 25 re~nliGn pin 44B contacts the op~ osite side of the activation tab ring 50 causing the cei,le,i"g spring 44 to be ~l~esse~ and to g6i,erale a centering force between the activation ring 18 and the control ring 16 that tends to return them to an orientation where no axial force is generated by the ball ramp actu~tQr 14.
The control clutch 25 is comprised of the annular control disc 28 that is nonrolalably connected to the ball ramp tab ring 52 through the flex ring 26 which is in turn nonrotalably connected to the control ring 16. An annular 21464~2 -drive ring 30 is nonrotatably and axially fixed to the transmission input shaft 8 through the connection segment 31. On one face of the drive ring 30 is attached a first friction pad 32 which frictionally couples the control disc 28 to the transmission input shaft 8 when the driveline clutch 5 is in the engagement 5 mode. On the opposite face of the drive ring 30 is attached a second friction pad 34 such that the two friction pads 32 and 34 oppose one another with the control disc 28 disposed inbetween for cla" ,~ ng by action of a clamping spring46 which ,uresses against the backside of the drive ring 30 and against a stop ring 40. The axial position of the stop ring 40 is determined in the direction 10 opposite the drive ring 30 by a snap ring 38 located and retained in the control clutch collar 36. The control clutch collar 36 is moved in a direction toward the drive ring 30 by a release bearing 44 which is nonrotatably but axially slidablealong the l~ans,nission input shaft 8. The stop ring 40 is rotationally coupled to the release bearing using a roller ball bearing 41. Thus by moving the release bearing 44 toward the drive ring 30, the clamping spring 46 is further com~.ressed against the axially sl~tioi ,ary drive ring 30 the stop ring 40 is no longer spring loaded against the snap ring 38 and the clamping force on the control disc 28 is reduced since the second friction pad 34 mounted to the control clutch collar 36 is no longer loaded against the collar 36 by the clamping spring 46. The result is that the transr"ission input shaft 8 is no longer hi~tio"ally connected to the control ring 16 of the ball ramp me~hanisn, 14 and a reduced axial clamping force is generated by the ball ramp mechanism 14 on the friction discs 10 thereby allowing the clutch asse"ll,ly 5 to be released.
The rotary motion of the release arm assembly 51 which forms part of the release mechanism 15 is controlled by the driver/operator through some type of linkage 54 which is attached to an exle,lsion arm 53 and is moved forward and backward so as to rotate the extension arm 53 about the lelease shaft 55. The exle"sion arm 53 is nonrolatably attached to the release shaft 55 which is rotationally supported by bearings 60 and 62 which are mounted to the Iransmission case 3 and/or the bellhousing 6 for rotation. The release arm 48 is also nonrotalaL,ly attached to the release shaft 55 and extends to form a 21~6~82 release yoke 49 which contacts the release collar 44 with two release pads 49A
and 49B.
To summarize the operation of the release mechanism 15 of the present invention which functions to effectuate a release of the clutch assembly5 using a relatively low force, the o,ueralor causes the linkage 54 to apply a pulling force on the exlensioil arm 53 of the release assembly 51 which rotates the release arm 48 and causes the release yoke 49 to contact the release collar 44 with two yoke pads 49A and 49B. The forward axial movement of the release collar 44 towards the ball ramp mechanism 14 forces the stop ring 40 towards the drive ring 30 which is fixed to the t.ansmissio" input shaft 8. The clamping spring 46 becomes more compressed and the control collar 36 moves so that the second friction pad 34 moves away from the first friction pad 32 and the control clutch disc 28 is allowed to rotate relative to the Ir ansmission input shaft 8. Since the control disc 28 is coupled to the control ring 16, the ball ramp mechanism 14 is unloaded and the ball ramp mechanism 14 then axially contracts thereby reducing the clamping load on the clutch friction disc 9. Thus, by utilizing the present invention, the driveline clutch 5 is released using there-luced mechanical force level required to compress the relatively light springload of the annular clamping spring 46 as opposed to the force level required to compress the prior art high ~ate clutch springs.
Figure 2 is a cross sectional view of the ball ramp ætu~tor of the - preseill invention as shown in Figure 1 taken along line ll-ll. The edge of the control clutch collar 36 and the stop ring 40 are shown with the release assembly 51 acting upon the release collar 44 through the yoke pads 49A and 49B. The extension arm 53 and the release arm 48 are nonrolaldL~ly allachecl to the release shaft 55 which is supported in bearings 60 and 62. The exle~ ~sion arm 53 is rotated by action of the driver/operator through some typeof mechanical linkage 54 when the driveline clutch assembly 5 is ready for release which rotates the release shaft 55 and the release yoke 49 which causes the yoke pads 49A and 49B to press against the release collar 44 which axially moves along with the attached control clutch collar 36 so as to release the control clutch 25 and the driveline clutch assembly 5.

2146~82 -g Refer,i,1y now to Figures 3, 4 and 5 to describe the G~)eratio~ of the ball ramp ~ctu~tor 14. A cross-sectional view of the ball ramp ~ctl~tor 14 taken along line lll-lll of Figure 1 is shown in Figure 3 and views taken along line IV-IV of Figure 3 showing the activation ring 18 and the control ring 16 separated by a rolling element 20A are shown in Figures 4 and 5. Three spherical rolling elei"enl~ 20A, 20B and 20C are spaced approximately 120 apart rolling in three tapered ramps 22A, 22B and 22C respectively as the control ring 16 is rotated relative to the activation ring 18. The rolling ele.),e,lls 20A, 20B and 20C can be held in a constant relative position to one another using a conventional type bearing cage (not shown). Any number of spherical rolling elements 20A, 20B and 20C and respective ramps 22 could be utilized depending on the desired rotalion and axial motion of the ball ramp ~ctl ~tor 14It is desiral,le to employ at least three spherical rolling elemenls 20A, 20B and 20C travelling on a like number of identical opposed ramps formed in both the control ring 16 and the activation ring 18 to provide stability to the control ring 16, the activation ring 18 and the thrust ring 19. Any type of rolling element 20 could be utilized such as a ball or a roller. The activation ring 18 is shown which rotates with the pressure plate 12, the pressure plate housing 11 and the flywheel 4 turning about axis of rotalion 59 cc nc;Jent with the axis of rol~tio"
57 of the lra,~sn,;ssioi) input shaft 8.
Three semi-circular, circumferential ramps 22A, 22B and 22C are shown formed in the face of the activation ring 18 with corresponding identical opposed ramps 23A, 23B and 23C (where 23B and 23C are not fully shown) formed in the face of the control ring 16 as shown in Figure 4. The control ring16 and the activation ring 18 are made of a high strength steel with the ramps 22A, 22B, 22C, 23A, 23~ and 23C carburized and hardened to RC 55 60. The ramps 22A, 22B, 22C, 23A, 23B and 23C are tapered in depth as more dearly shown in Figure 4 and circu"~ere"lially extend for approximately 120 (actually slightly less than 1209 to al!ow for a separation section between the ramps).
The axial separation 66 between the control ring 16 and the activation ring 18 is determined by the rotational orientation between the two corresponding opposed ramps such as 22A and 22B where the spherical rolling element 20A

2l4~4a~
-rolls on both ramps 22A and 22B as the control ring 16 is rota~e.l relative to the activation ring 18 on the same axis of rotation. The relative rotalion forces thtwo rings 16,18 apart or allows them to come closer together as determined by the position of the rolling elements 20A,20B, and 20C or their respective ramp pairs 22A,23A, and 22B,23B, and 22C, 23C thereby providing an axial movement for clamping the clutch disc 9 between the pressure plate 12 and the flywheel 4.
Figure 4 illusl~ales the rotaliGnal orienlaliGn of the control ring 16 and the activation ring 18 when the axial separation 66 is at a minimum when the ramps 22A and 23A are aligned and the spherical element 20A is in the deepest section of the ramps 22A and 23A. As the control ring 16 is rotated relative to the activation ring 18 by application of a control torque input from the cGnlrol clutch 25, the ramps 22A and 23A move relative to one another causing the spherical element 20A to roll on each of the ramp surfaces 22A and 23A
moving to a difterenl ~ ~ositisi, on both ramps 22A and 23A thereby forcing the control ring 16 and the activation ring 18 apart as shown in Figure 5 where the axial separation 66 has si~nifica"lly increased. A similar separalion force is generated by rolling el~ ei ll 20B rolling on ramp surfaces 22B and 23B and by rolling element 20C rolling on ramp surfaces 22C and 23C. The rotation of the control ring 16 is clearly illusl,aled in Figures 4 and 5 by the relative shffl in position of refere,~ce points 62 and 64 from directly opposed in Figure 4 to an offset position in Figure 5 calJse~ by rotation of the control ring 16 in the direction of the arrow. This axial displacement can be used for a variety of applications since the axial force level generated by the ball ramp mecl ,anisill 14 relative to the torque applied to the control ring 16 is quite high, typically a ratio of 100:1. Thus the ball ramp mec~,anisi" 14 can be used as iilustldlel~ inthis application to load a pressure plate 12 against a clutch disc 9 and flywheel 4 in a vehicle driveline with a low relative force required to control the engagement and disengagement of the main clutch assembly 5. Add;:io"al illustrative details of operation of a ball ramp actuator can be found by reference to U.S. Patent No. 4,805,486.
This invention has been described in great detail, sufficient to 21q ~482 enable one skilled in the art to make and use the same. Various alterations and mo~ific~tions of the invention will occur to those skilled in the art upon areading and u ".le,~landing of the foregoing spec;ficalion and it is intended toinclude all such alterations and modifications as part of the invention insofar as 5 they c~me within the scope of the a~.penJed daims.

Claims (15)

1. A ball ramp mechanism having a mechanical control system for coupling two rotating elements comprising:
an input element driven by a prime mover and rotating around an axis of rotation;
an output element having an axis of rotation congruent with said axis of rotation of said input element for rotating an output device;
a ball ramp actuator for generating an axial movement comprising; a control ring having an axis of rotation connected to and rotating with said output element, said control ring having at least two circumferential control ramps formed in a first face of said control ring about said axis of rotation of said control ring, said control ramps having a semi-circular cross-section and varying in axial depth; an equal 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 radial position to said control ramps in said control ring where said activation ramps oppose said control ramps and where each of said rolling elements is trapped between said activation ramp and a respective control ramp, said control ring axially and rotationally movably disposed relative to said activation ring;
coupling means for rotatably joining said input element to said output element where said coupling means varies the degree of rotational coupling between said input element and said output element according to the axial position of said control ring relative to said activation ring;
control means for applying a force to said control ring according to a control input, said control means comprised of a control clutch attached to said control ring for frictional connection to said output element and a mechanical release system where said control clutch connects and disconnects said control ring from said input element according to the state of said release system.

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 being joined to said coupling means.

3. The ball ramp mechanism of claim 1 wherein said rolling elements are spherically shaped.

4. The ball ramp mechanism of claim 1 wherein said coupling means is a friction clutch assembly 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;
a pressure plate having a friction surface for frictionally reacting against said clutch disc second friction surface where said pressure plate is connected to said flywheel and nonrotatably connected to said activation ring.

5. The ball ramp mechanism of claim 4 wherein a spring is interposed between said pressure plate and said activation ring for absorbing axial shock loads.

6. The ball ramp of claim 1 wherein said control ramps and said activation ramps taper in axial depth having a maximum depth at approximately a centerline of said control and activation ramps and a minimum depth at approximately each end of said control and actuation ramps.

7. The ball ramp mechanism of claim 1 wherein a torsional return spring is connected to said control ring and reacts against said activation ring to supply a centering force to said control ring with respect to said activationring.

8. The ball ramp mechanism of claim 1, wherein said release system comprises a pivoted arm with its rotational position controlled by an operator, said arm axially displacing a clamping spring, said clamping spring applying a load on said control clutch for connecting and disconnecting said control ring to said output element.

9. The ball ramp mechanism of claim 8, wherein said control clutch comprises an annular control disc connected to said control ring, where said control disc is interposed between a first friction pad and a second friction pad, said first and second friction pads being clamped against said control disc using said clamping spring, said first friction pad being mounted on an annular drive disc, said drive disc encircling and fixed to said output element and saidsecond friction pad being mounted to an annular control collar, said control collar encircling said input element where the axial position of said control collar relative to said control disc is determined by said pivoted arm.

10. The ball ramp mechanism of claim 9, wherein said clamping spring is contained between said drive disc and an annular stop ring where said stop ring is axially displaced by said pivoted arm contacting and axially displacing a release collar slidingly supported on said output element with a bearing joining said stop ring to said release collar to allow relative rotationtherebetween.

11. 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 ball ramp actuator for axially displacing said pressure plate toward said flywheel, said 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, the grooves on said activation ring and said adjacent control ring being arranged so that relative angular movement of said activation ring and control ring in either 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 rotatable about said axis of rotation;
a control clutch for linking said output shaft to said control ring, said control clutch comprising; a control disc attached to said control ring and rotatable about said axis of rotation, said control disc frictionally connected to said output shaft through a drive ring, where said control disposed and clamped between said drive ring and a control collar where said control collar is forced against said control disc using a clamping spring, said clamping spring having a first end reacting against said drive ring which is fixed to said output shaft, and a second end reacting against a stop ring thereby supplying a clamping force between said control collar and said drive ring, said stop ring having its axial position established by a release arm pivoting to contact a release bearing encircling and slidingly supported on said output shaft and rotatably connected to said stop ring where said release arm axially displaces said release bearing which axially displaces said stop ring to axially displace said control collar and release said clamping force between said first and second friction pads and said control disc.

12. The driveline clutch of claim 11, further comprising a torsional return spring said return spring being connected to said control ring and reacting against said activation ring to supply a centering force to said control ring with respect to said activation ring.

13. The driveline clutch of claim 11, further comprising a spring interposed between said pressure plate and said activation ring for absorbing axial shock loads.

14. The driveline clutch of claim 11, wherein said control ramps and said activation ramps are tapered in axial depth having a maximum depth at approximately a centerline of each of said control ramp and said activation ramp and a minimum depth at approximately each ends of said control and actuation ramps.

15. The driveline clutch of claim 11, wherein said control ring is reacted in an axial direction against a thrust ring through a thrust bearing, said thrust ring being indirectly attached to said flywheel.