Note: Descriptions are shown in the official language in which they were submitted.
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
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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.
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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.
30DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
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
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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
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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
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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
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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
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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.
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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
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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
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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.
