Vibration damper with variable rate springs and damping friction

A vibration damper assembly for the clutch driven plate utilized in an automotive vehicle which provides a first stage of travel with a low spring rate and zero or low damping friction and a second stage of travel with an increased spring rate and increased damping friction as required for the remaining travel. A generally conventional clutch driven plate assembly has aligned spring windows in the plates and hub flange receiving low rate compression springs and additional aligned spring windows receiving the higher rate compression springs; the windows in the hub flange being enlarged relative to the windows in the plates, a generally annular friction plate received within the central opening of the spring retainer plate with peripheral tangs on the friction plate received in enlarged notches in the retainer plate inner periphery to provide a limited lost motion, and a thrust plate and Belleville spring urging said friction plate against the hub.

BACKGROUND OF THE INVENTION 
Clutch driven plates generally utilize vibration damping means in a 
manually-actuated vehicle transmission to overcome objectionable vibration 
and rattle during the torsional coupling of the engine driven shaft and 
the transmission input shaft by a friction clutch. A conventional 
vibration damper assembly includes a hub having an internally splined 
passage to receive the splined end of a transmission input shaft and a 
radial flange, a clutch plate journalled on the hub and carrying the 
friction facings at its periphery, a spring retainer plate journalled on 
the hub on the opposite side of the hub flange from the clutch plate, and 
damper springs positioned in axially aligned sets of spring windows in the 
hub flange and the clutch and spring retainer plates. The clutch plate and 
spring retainer plate are connected together by stop pins extending 
through elongated peripheral notches in the hub flange. 
This damper assembly provides for a substantially constant rate of energy 
dissipation, and friction washers may be positioned between the hub flange 
and the clutch and spring retainer plates to provide additional damping 
friction in predetermined stages. However, the above described vibration 
damper assembly has proved to be inadequate where specialized problems 
occur, such as gear rattle at an idle condition, necessitating a 
multi-stage vibration damping arrangement, with or without friction 
damping in the stages. The present invention provides such a multi-stage 
damper to overcome the specialized problems encountered in a vehicle drive 
line. 
SUMMARY OF THE INVENTION 
The present invention comprehends the provision of a multi-stage vibration 
damper in a friction clutch plate to provide a low spring rate first stage 
with zero or low damping friction for the initial travel and a second 
stage of travel with an increased spring rate and increased damping 
friction as required for the remaining travel of the damper assembly. The 
first stage of travel utilizes a pair of diametrically opposed low rate 
compression springs with substantially no friction damping, and the second 
stage of travel utilizes four sets of compression damping springs having a 
higher spring rate; the second stage being accompanied by movement of a 
friction plate together with a spring retainer plate of the clutch plate 
assembly. The friction plate includes peripheral tangs received in notches 
formed in the inner periphery of the retainer plate, the slots being 
dimensioned to provide relative lost motion during the first stage of 
travel of the damper assembly. 
The present invention also comprehends the provision of a multi-stage 
vibration damper assembly which will provide damping friction variations 
of zero friction, single friction or double friction as desired by 
addition of a second friction plate and by modification of the clearances 
between the slot and tang connection of the friction plates in the 
vibration damper assembly. In this assembly, a first friction plate is 
positioned within the inner periphery of and in the same plane of the 
spring retainer plate while the second friction plate is located between 
parallel thrust plates adjacent the spring retainer plate and has 
forwardly projecting tangs received in slots formed in the retainer plate 
at a larger diameter than the diameter of the first friction plate. The 
second friction plate will be picked up at the same or a later point than 
the first friction plate upon the rotary movement of the spring retainer 
plate. 
Further objects are to provide a construction of maximum simplicity, 
efficiency, economy and ease of assembly and operation, and such further 
objects, advantages, and capabilities as will later more fully appear and 
are inherently possessed thereby.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring more particularly to the disclosure in the drawings wherein are 
shown illustrative embodiments of the present invention, FIGS. 1 through 4 
disclose a clutch driven plate assembly 10 having a two-stage vibration 
damper within the assembly to provide multi-stage vibration damping. The 
clutch plate assembly includes a hub with a generally tubular barrel 11 
and having flattened portions 20 and an integral radial flange 12 
intermediate the ends of the barrel and formed with a pair of 
diametrically opposed smaller spring windows 13 and four circumferentially 
spaced larger spring windows 14. The periphery 15 of the flange is 
provided with elongated arcuate notches 16 to receive stop pins 17. 
A clutch driven plate 18 is journalled at its inner periphery 19 on the hub 
barrel 11 and carries annular friction facings 21 adjacent its outer 
periphery; the facings being secured to the plate by rivets 22. The plate 
has a pair of smaller spring windows 23, four larger spring windows 24 and 
a plurality of openings 25 to receive an end of each stop pin 17. A spring 
retainer plate 26 located on the opposite side of the hub flange 12 has a 
pair of smaller spring windows 27, four larger spring windows 28 and a 
plurality of openings 29 to receive the opposite ends of the stop pins 17. 
The inner periphery 31 of the plate 26 is spaced outwardly from the hub 
barrel 11 and is provided with a plurality of circumferentially spaced 
notches 32 for a purpose to be later described. 
Each set of smaller spring windows 13, 23 and 27 are all of the same 
arcuate length and are axially aligned to receive a low rate compression 
spring 33 therein for the first stage of travel. Likewise each set of 
larger spring windows 14,24 and 28 are axially aligned to receive damper 
springs or spring sets 34; the windows 14 in the hub flange 12 being a 
greater arcuate length than the windows 24 and 28 to provide limited lost 
motion in operation of the damper. 
Journalled on the hub barrel 11 is a generally annular friction plate 35 
having circumferentially spaced tangs 36 on the outer periphery received 
in the notches 32 of the spring retainer plate 26; both the plate 26 and 
friction plate 35 lying in a common plane and in sliding engagement with 
the side of the hub flange 12. An annular thrust plate 37 having inner 
flattened surfaces 38 cooperating with the hub flats on the barrel 11 
remains stationary with the hub barrel in frictional sliding engagement 
with the rotating friction plate 35, and a Belleville spring 39 is located 
on the barrel against the thrust plate 37 and retained by a snap ring 40 
received in a groove 41 in the barrel. The Belleville spring 39 urges the 
thrust plate 37 against the friction plate 35 to create frictional sliding 
engagement with the hub flange 12. Each notch 32 has a greater arcuate 
length than the tang 36 received therein to provide a clearance "x" (FIG. 
3) in one or both of the drive and coast directions. 
When torque is applied through engagement of the friction facings 21 with 
the rotating surfaces of the flywheel and pressure plate (not shown) of 
the clutch, plates 18 and 26 move in unison compressing the pair of 
diametrically opposed low rate damper springs 33 while the higher rate 
springs 34 are not compressed due to the enlarged windows 14 in the hub 
flange. During this first stage of travel, zero or low damping friction 
occurs as the plate 26 rotates relative to the stationary friction plate 
35 through the distance "x" (FIG. 3). When the slots or notches 32 of 
plate 26 contact the tangs 36 of the friction plate, the plates 26 and 35 
rotate in unison to provide a greater damping friction, the thrust plate 
37 remaining stationary, as required for the remainder of damper travel. 
The tangs are desirably picked up when the higher rate springs 34 contact 
the hub flange to be compressed for the second stage of travel. The 
assembly then provides the requisite damping action between the friction 
facings and the hub barrel transmitting torque to the transmission input 
shaft received in the splined passage 42 in the hub barrel. 
FIGS. 5 through 10 disclose an alternate embodiment of damper assembly 45 
wherein the parts identical to those of FIGS. 1 through 4 will have the 
same reference numeral with a script a. This assembly includes a clutch 
hub having a barrel 11a having flats 20a and flange 12a, a clutch driven 
plate 18a journalled on the hub barrel and carrying the friction facings 
21a, and a spring retainer plate 26a secured to the clutch plate 18a by 
stop pins 17a extending through peripheral notches 16a in the hub flange 
12a. Small spring windows 13a, 23a and 27a in the hub flange 12a, clutch 
plate 18a and spring retainer plate 26a, respectively, have equal lengths 
and are axially aligned to receive low rate damper springs 33a. Likewise, 
the larger spring windows 14a, 24a and 28a are axially aligned to receive 
higher rate damper springs 34a; the windows 14a having a greater length 
than the windows 24a and 28a to provide lost motion between the springs 
34a and flange 12a during the first stage of travel. 
The inner periphery 31a of the spring retainer plate 26a is provided with 
notches 32a to receive the tangs 36a of the friction plate 35a; the 
notches providing a distance "x" (FIG. 8) on each side of the tangs 36a. A 
first thrust plate 37a having flats 38a is biased by the Belleville spring 
39a frictionally against the friction plate 35a, while a second thrust 
plate 46 having flats 47 parallels to the first thrust plate 37a and is 
directly engaged by the Belleville spring 39a. Located between the thrust 
plates 37a and 46 is a second friction plate 48 journalled on the hub 
barrel 11a. The outer periphery 49 of plate 48 is provided with outwardly 
and then forwardly extending ears or tangs 50 which are received in 
elongated arcuate slots 51 in the spring retainer plate 26a; the slots 51 
being positioned between and radially outwardly of the notches 32a in the 
inner periphery 31a. The slots 51 provide a circumferential clearance "y" 
(FIG. 8) relative to the tangs 50. 
This alternate embodiment 45 provides damping friction variations of zero 
or low friction, single friction or double friction as desired by 
modifying the clearance "x" and "y" as seen in FIG. 8, between the tangs 
and slots or notches in the damping friction area. One arrangement 
utilizes an equal clearance in both the notches 32a and the slots 51 to 
provide double friction in the second stage of travel. Thus, where "x" 
equals "y", initial application of torque to the clutch plate 18a causes 
rotation of the plates 18a and 26a relative to the hub flange 12a 
compressing the low rate springs 33a until the springs 34a contact the 
edges of spring windows 14a of the hub flange; the plate 26a also moving 
relative to the friction plates 35a and 48. At the point where the springs 
34a engage the flange windows 14a, the notches 32a and slots 51 pick up 
the tangs 36a and 50, respectively to provide double friction resulting 
from the Belleville spring 39a and thrust plates 37a and 46 acting on the 
friction plates 35a and 48. 
By adjusting the clearances so that "y" is greater than "x", a third stage 
friction damping action is obtained. Thus, rotation of the spring retainer 
plate 26a relative to the friction plates 35a and 48 provides a first 
stage of zero or low friction through the clearance "x". When the notches 
32a pick up the tangs 36a, a single friction damping occurs through 
rotation of friction plate 35a in frictional contact with the hub flange 
12a and the thrust plate 37a. When the plates 26a and 35a rotate through 
the distance of "y" minus "x", the slots 51 then pick up the tangs 50 of 
the second friction plate 48 to provide a double friction damping action 
for the remainder of travel. FIG. 10 discloses the travel of the damper 
assembly as all of the springs 33a and 34a are compressed until the stop 
pins 17a move to and contact the ends of the elongated notches 16a. The 
relative angular position of the retainer plate 26a to the friction plates 
35a and 48 remains the same as in FIG. 9 and only the angular relationship 
to the hub 11a has changed due to the continued travel. 
Obviously, whether the transition from zero damping to single friction 
damping or double friction damping occurs simultaneously with the 
engagement of the high rate damper springs is a matter of choice. The 
transition could occur earlier, simultaneously or later than the 
initiation of compression of the high rate damping springs depending on 
the damping characteristics desired for the clutch assembly. Also, in both 
embodiments, the clearance "x" or the clearances "x" and "y" are shown for 
both the drive and coast directions of rotation of the clutch assembly, 
however, depending on the desired characteristics, the clearance for the 
coast side in the notches 32 or 32a and the slots 51 may be omitted. In 
that case, a multi-stage friction damping would only occur in the drive 
direction of rotation.