Torsional vibration damper for a lock-up clutch

A torsional vibration damper for a torque converter lock-up clutch having viscous and spring-damping characteristics during the initial relative movement between the input and output members of the clutch and a spring-damping characteristic during further relative movement. Viscous damping can also be provided during the further relative movement, if desired.

This invention relates to vibration dampers and more particularly to 
viscous damping of torsional vibrations. 
It is an object of this invention to provide an improved viscous damper for 
torsional vibration damping. 
It is another object of this invention to provide an improved torsional 
vibration damper wherein the initial damping phase is accomplished by a 
piston and cylinder for viscous damping and a spring for mechanical 
damping, and wherein the final damping phase is accomplished by another 
spring after the piston has bottomed in the cylinder. 
A further object of this invention is to provide an improved torsional 
damper disposed between the input and output members of a torque converter 
lock-up clutch and having a piston slidably disposed in the cylinder and 
drivingly connected to a plunger through a lost motion one-way driving 
connection to provide viscous damping when the piston moves relative to 
the cylinder and also having one spring means which provides damping 
during a viscous damping portion and another spring means which provides 
damping in parallel with the one spring means when the plunger moves 
relative to the piston.

Referring to the drawings, there is shown in FIG. 1, a clutch assembly, 
generally designated 10, having a clutch plate input member 12 with a 
frictional surface 14 bonded thereto, and an output member 16. The clutch 
plate 12 has a plurality of spokes 18, such as that shown in FIG. 3, which 
spokes 18 are aligned with similar spokes 20 formed on the output member 
16, such as those shown in FIG. 2. The spokes 18 and 20 have formed 
therebetween recesses or openings in which are disposed vibration dampers, 
generally designated 22. In FIG. 1, it is seen that four equally spaced 
vibration dampers 22 are utilized between the input member 12 and the 
output member 16 of the clutch assembly 10. 
The vibration dampers 22 include a cylinder portion 24 which has a rounded 
end portion 26 which abuts the spokes 18 and 20 in the "at rest" position 
shown in FIG. 2. The cylinder portion 24 has a bore 28 in which is 
slidably disposed a piston 30. The piston 30 has slidably disposed therein 
a spherically shaped head 32 of a plunger 34. The plunger 34 has a rounded 
end portion 36 which abuts the spokes 18 and 20 when the damper is in the 
"at rest" position. The rounded portion 36 of plunger 34 and rounded 
portion 26 of cylinder 24 are urged apart by a coil spring 38 to maintain 
abutting relationship between the damper 22 and the spokes 18 and 20. The 
piston 30 is urged into abutting relationship with the spherical head 32 
of the plunger 34 by a plurality of Belleville springs 40 which are 
compressed between the portion 36 of plunger 34 and the piston 30. 
The rounded portion 26 of cylinder 24 has a restricted passage 42 formed 
therein which communicates with the bore 28 of cylinder 24. The plunger 34 
has an axially extending passage 44 formed therein which is in fluid 
communication with the space between spokes 20. The spherical head 32 of 
plunger 34 has an opening 45 in which is disposed a ball 46 having freedom 
of movement to act as a check valve to control the admission of fluid 
through passage 44 to bore 28 as will be explained later. The ball 46 is 
larger than the passage 44. The opening 45 has material deformed therein, 
such as at 48, which prevents the ball 46 from leaving the plunger 34 in a 
lefthand direction, as viewed in FIG. 2, but provides sufficient opening 
to permit the free passage of fluid through passage 44 around ball 46 into 
bore 28 of cylinder 24. A cross channel 50 is drilled in plunger 34 
intersecting the axially extending passage 44. 
The clutch and damper assemblies are preferably used in a torque converter 
lock-up clutch such as that shown in U.S. Pat. No. 3,252,352 to General, 
et al., issued May 24, 1966. Therefore, the recesses, containing dampers 
22, are filled with hydraulic fluid so that fluid is available for the 
viscous damping operation. 
When the clutch is engaged, the input member 12, and therefore spokes 18, 
will move relative to the output member 16, and therefore spokes 20, as 
can be seen in FIG. 3, where full movement has occurred. During the 
initial relative movement, between the spokes 18 and 20, the spring 38 is 
compressed and the plunger 34 through Belleville springs 40 causes the 
piston 30 to be moved in the cylinder bore 28 thereby forcing fluid out of 
restriction 42. During this portion of movement, the ball 46 is seated in 
passage 44 to prevent fluid from moving through passage 44 and cross 
channel 50. During this portion of the movement in damper 22, both viscous 
and spring damping occur. 
After a predetermined amount of movement, the piston 30 will bottom in bore 
28 such that further relative movement between the spokes 18 and 20 causes 
compression of the Belleville springs 40 and movement of the plunger 34 
relative to the piston 30. The spherical end 32 of plunger 34 is 
preferably sized to have sufficient clearance between the inner surface of 
piston 30 and the spherical end 32 such that the free passage of fluid 
between the piston 30 and plunger 34 is permitted. It is, however, 
possible to design the clearance between these parts such that continued 
viscous damping can occur. It is also possible to design the stem portion 
of plunger 34 such that the fluid is moved within the inner cavity of the 
piston 30 from one side of the spherical end 32 to the other. Thus, the 
second or final phase of damping can be controlled to be either solely 
spring-damping or a combination of spring and viscous damping. Also, by 
controlling these clearances, it is possible to eliminate the restriction 
42 in cylinder 24 so that all of the fluid movement during viscous damping 
passes through the clearances. 
The relative movement spokes 18 and 20 occurs because of the torsional 
vibrations which are transmitted by the engine to the transmission. It is, 
of course, recognized that these torsional vibrations require relative 
movement in both directions, that is, clockwise and counterclockwise, 
between the spokes 18 and 20. 
The above description was directed toward that phase when spokes 18 are 
moving counterclockwise relative to spokes 20 as viewed in FIGS. 2 and 3. 
As the spokes 18 move clockwise relative to spokes 20, the ball 46 is 
moved against the displaced material 48 to admit fluid freely into the 
bore 28 of cylinder 24. Thus, the fluid returning to fill the bore 28 does 
not have to pass solely through restriction 42. Therefore, the bore 28 can 
be filled more rapidly than it can be exhausted. 
Since the relative movement between plunger 34 and piston 30 or cylinder 24 
will, at times, be angular, the plunger 34 has a tapered portion 52 
adjacent the spherical end 32, which cooperates with tapered portions 54 
and 56 formed on the piston 30, to permit relative angular movement 
between the plunger 34 and piston 30. A taper 58 is formed on the cylinder 
24 to maintain clearance between the plunger 34 and cylinder 24 when 
relative angular movement occurs. 
The damping characteristics can be readily controlled by controlling the 
spring rate constants in springs 38 and 40 and by controlling the size of 
the restriction 42. Thus, the initial damping phase can assume a slope or 
characteristic that is different than the final damping phase by judicious 
selection of the spring rate constants in the Belleville springs 40 and 
coil springs 38. It is also possible to use a coil spring in place of 
Belleville springs 40. 
The duration of the viscous damping phase can be controlled by judiciously 
selecting the length of piston 30 such that the bottoming of piston 30 in 
bore 28 can be selected to provide the desired amount of viscous damping 
between the input and output members of the clutch. While not shown, the 
dampers 22 can be enclosed on one side by sheet metal components to 
prevent the free passage of fluid from one side of the clutch to the other 
when used as a lock-up clutch in a torque converter. This will permit the 
fluid pressure within the torque converter to engage the clutch as shown 
in the above-mentioned General et al patent. The damper will also provide 
damping in a more conventional type clutch, such as that used with 
synchromesh transmissions, provided the clutch space is filled with 
hydraulic fluid. These types of so-called wet-clutches are well-known in 
the art. 
Obviously, many modifications and variations are possible in light of the 
above teaching. It is, therefore, to be understood that within the scope 
of the appended claims, the invention may be practiced otherwise than as 
specifically described.