Viscous fluid torsional vibration dampening device having an elastic slider configured to provide friction dampening

A flywheel assembly comprises a first flywheel, a second flywheel supported on the first flywheel so as to be rotatable, a drive member connected to said first flywheel to ensure a space in which viscous fluid can be contained therebetween, a driven member connected to the second flywheel to constitute, together with the first flywheel and the drive member, a fluid chamber with which viscous fluid is filled, a coil spiring for elastically connecting the members to each other, and a viscous damper part for moving viscous fluid in the fluid chamber in response to relative rotation between both the members to create viscous resistance. The driven member has a window hole containing the coil spring and a fluid supplying path connecting with the fluid chamber from the window hole. The viscous damper part has chokes for creating viscous resistance when the first flywheel and the driven member are relatively rotated. The chokes are opened and closed by sliders which can be pressed against the wall of the fluid chamber in a dry friction state. The driven member has a plurality of recesses concaved radially inward on its outer peripheral surface. The sliders respectively have projections projected into the recesses of the driven member, and the chokes are formed between the recesses and the projections.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a torsional vibration damping 
device, and more particularly, to a torsional vibration damping device for 
use between an input rotation member and an output rotation member of a 
power transmission apparatus. 
Viscous or fluid dampening devices employed in automotive flywheel devices 
are known. Such dampening devices are typically disposed between an input 
flywheel and an output flywheel of a flywheel assembly or power 
transmission apparatus. Examples of this type of conventional device 
include a flywheel device used in, for example, the engine of an 
automobile. 
One such prior art device in includes a first flywheel, a second flywheel 
coupled coaxially to the first flywheel for limited rotary displacement, 
and a viscous damper mechanism disposed between both the flywheels for 
elastically connecting the flywheels to each other and dampening torsional 
vibration between the flywheels by the viscous resistance of viscous fluid 
in response to rotary displacement between the two flywheels. The viscous 
dampening mechanism has an annular case fixed to the first flywheel and 
choke activating members disposed so as to be circumferentially movable 
within the annular case. The annular case is filled with viscous fluid. 
The dampening mechanism includes an output member connected to the second 
flywheel, and has a plurality of projections projected into the annular 
case. The choke activating members are in a cap shape, and are 
respectively fitted in the projections of the output member and are 
movable through a predetermined angle relative to the projections. Chokes 
through which viscous fluid can pass are formed between the choke 
activating members and the projections. 
In the above described conventional torsional vibration damping device, 
fluid passes through the chokes formed between the choke activating 
members and the projections of the output member in response to relative 
displacement of the first and second flywheels. The chokes limit fluid 
passage thus dampening vibration during relative displacement of the 
flywheels. In addition, if respective ends of the choke activating members 
abut against the projections, the chocks are closed. 
In the conventional device, however, there is typically insufficient 
resistance force to restrain the longitudinal vibration of the body of an 
automobile during tip-in and tip-out of the automobile and the vibration 
thereof when starting the engine. The reason for this is that the volume 
of viscous fluid in the annular case is insufficient, thereby to make it 
difficult to obtain a sufficient resistance force. 
In the above described conventional torsional damping device, a radially 
outer surface of the output member functions as a part of each chokes. 
Since the radial outer surface of the output member has a plurality of 
radial projections, it is difficult to manufacture, machine or process the 
radially outer surface of the output member with high precision. 
SUMMARY OF THE INVENTION 
An object of the present invention is to obtain a large damping force which 
has not been obtained in the conventional construction. 
Another object of the present invention is to replenish a fluid chamber 
with a sufficient amount of viscous fluid to obtain desired viscous 
resistance. 
Still another object of the present invention is to make it easy to 
manufacture and process an output member. 
A torsional vibration damping device according to a first aspect of the 
present invention is a torsional vibration damping device of a power 
transmission apparatus having an input rotation member and an output 
rotation member which is connected to the input rotation member so as to 
be relatively rotatable and to which power from the input rotation member 
is transmitted. The torsional vibration damping device includes a viscous 
damping part and a dry friction part. The viscous damping part is formed 
between the input rotation member and the output rotation member and 
includes a choke through which fluid passes in response to relative 
rotation between the input rotation member and the output rotation member 
for damping torsional vibration. The dry friction part damps the torsional 
vibration by dry friction in response to rotary displacement of the input 
and output members. 
The relative displacement between the input rotation member and the output 
rotation member causes fluid to pass through the choke of the viscous 
damping part. The choke provides a viscous resistance force to damp the 
torsional vibration. In addition, the dry friction part produces a dry 
frictional force. 
According to a second aspect of the present invention, a torsional 
vibration damping device of a power transmission apparatus includes an 
input rotation member and an output rotation member which are connected to 
each other to allow for limited rotary displacement therebetween and 
through which power is transmitted. The limited rotary displacement is 
defined by two angular displacement ranges, a first range and a second 
range, the second range being larger that the first range. 
The apparatus includes an input member, an output member and a viscous 
damper mechanism. The input member is connected to the input rotation 
member, to constitute, together with the input rotation member, an annular 
fluid chamber filled with viscous fluid. The output rotation member is 
connected to the output rotation member, and has an abutting part 
projected into the fluid chamber. The viscous damper mechanism produces a 
first viscous damping force in the first displacement range, and produces 
a second viscous damping force in the second displacement range, the 
second damping force greater than the first damping force. The viscous 
damper mechanism is provided in the fluid chamber, and has first and 
second chokes through which fluid passes in response to relative rotation 
between the input rotation member and the output rotation member and a 
choke activating member moved in the fluid chamber to open and close the 
first choke. The choke activating member has an abutting part which abuts 
against the output member to press one surface of the choke activating 
member against a wall surface of the fluid chamber in a dry friction state 
for damping torsional vibration. 
If the input rotation member and the output rotation member are relatively 
rotated in the first displacement range, fluid passes through the first 
choke to produce the first viscous damping force. If the relative 
torsional angle is increased, an abutting part of the choke activating 
member abuts against the abutting part of the output member, to close the 
first choke. Fluid passes through the second choke in the second 
displacement range to produce the second viscous damping force. 
If the choke activating member abuts against the output member and then, 
the relative torsional angle is further increased, one surface of the 
choke activating member is pressed against the wall surface of the fluid 
chamber by the abutment. A fluid film between the surface of the choke 
activating member and the wall surface of the fluid chamber is removed by 
the pressing, whereby both the choke activating member and the fluid 
chamber slide while being pressed against each other in a dry friction 
state. Therefore, a large frictional force is obtained. 
In this construction, the dry friction state is caused by a part of the 
choke activating member for opening and closing the first choke. 
Therefore, it is possible to obtain a large frictional force in a simple 
structure. 
According to a third aspect of the present invention,an input rotation 
member to which power is inputted is connected to an output rotation 
member so as to be relatively rotatable therewith and through which the 
power from the input rotation member is transmitted, a viscous damping 
part and an annular sealing member are disposed between input and output 
members. 
The above described viscous damping part is formed between the input 
rotation member and the output rotation member and includes a choke 
through which fluid passes in response to relative rotation between the 
input rotation member and the output rotation member and an annular fluid 
chamber filled with viscous fluid. The annular sealing member is pressed 
against both the rotation members when pressure is exerted on the fluid 
chamber, to seal viscous fluid with which the fluid chamber is filled. 
If power is inputted to the input rotation member, the power is transmitted 
to the output rotation member. If the torsional vibration is transmitted 
to the input rotation member, both the rotation members are relatively 
rotated, whereby a viscous resistance force is produced by viscous fluid 
in the annular fluid chamber to damp the torsional vibration. Since the 
pressure is exerted on the fluid chamber at the time of the relative 
rotation, the annular sealing member is pressed against both the rotation 
members. Therefore, it is possible to reduce the leakage of viscous fluid 
from the annular fluid chamber, thereby to obtain a large resistance 
force. 
A fourth aspect of the present invention includes a torsional vibration 
damping device of a power transmission apparatus having an input rotation 
member and an output rotation member which are connected to each other so 
as to be relatively rotatable and through which power is transmitted. The 
torsional vibration damping device comprises an input member, an annular 
output member, and a plurality of slide stoppers. The input member is 
connected to the input rotation member and together with the input 
rotation member, forms an annular fluid chamber. The annular output member 
is connected to the output rotation member, and has its radially outer 
surface forming a part of the fluid chamber and having a plurality of 
recesses directed radially inward. The plurality of slide stoppers are 
disposed so as to be circumferentially movable in the annular fluid 
chamber and respectively have projections projected into the recesses of 
the output member to form chokes through which fluid can pass. 
If the slide stoppers are moved in the fluid chamber by torsional 
vibration, the torsional vibration is damped by a resistance force 
produced when fluid passes through the chokes. 
The radially outer portion of the output member need not be provided with 
projections. Consequently, the radially outer surface of the output member 
can be subjected to lathe machining, whereby the radially outer surface 
forms high-precision chokes. 
A fifth aspect of the present invention includes a first flywheel and a 
second flywheel supported on the first flywheel so as to be rotatable, 
first and second members, an elastic member, and a viscous damping part. 
The first member is connected to the first flywheel, to ensure a space in 
which viscous fluid can be contained therebetween. The second member is 
connected to the second flywheel, to constitute, together with the first 
flywheel and the first member, a fluid chamber with which viscous fluid is 
filled. The elastic member elastically connects the first and second 
members to each other. The viscous damping part moves viscous fluid in the 
fluid chamber to create viscous resistance in response to relative 
rotation between the first and second members. The second member has a 
window hole for containing the elastic member, and has a fluid supplying 
path connecting with the fluid chamber from the window hole. 
If torque is inputted to the first flywheel, the torque is transmitted from 
the first member to the second member through the elastic member, to 
further rotate the second flywheel. If torsional vibration is transmitted 
to radially rotate the first flywheel and the second flywheel, the elastic 
member repeatedly expands and contracts and the viscous damping part 
produces viscous resistance, to damp the torsional vibration. At this 
time, when viscous fluid leaks out of the fluid chamber, the fluid chamber 
is replenished with viscous fluid through the fluid supplying path from 
the window hole of the second member. Since the inside of the window hole 
of the second member is a place where the largest amount of viscous fluid 
is accumulated, the fluid chamber is replenished with a sufficient amount 
of viscous fluid, to obtain a desired viscous resistance force. 
The foregoing and other objects, aspects and advantages of the present 
invention will become more apparent from the following detailed 
description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a power transmission apparatus employing one embodiment of the 
present invention. The left side is the front side (engine side) and the 
right side is the rear side (transmission side). 
The power transmission apparatus is mainly composed of a flywheel assembly 
1, a clutch disc 101, and a clutch cover assembly 102. 
As shown in FIGS. 1 through 4, the flywheel assembly 1 mainly comprises a 
first flywheel 2, a second flywheel 3, and a viscous damper mechanism 4 
disposed between the first flywheel 2 and the second flywheel 3. The first 
flywheel 2 is fixed to an end of an engine crankshaft by a bolt 25. The 
second flywheel 3 has a friction surface 3a against which a friction 
member of the clutch disc 101 is pressed on its rear side surface. In 
addition, a clutch cover of the clutch cover assembly 102 is fixed to a 
radially outer portion of the friction surface 3a. 
The first flywheel 2 is a substantially disc-shaped member, and has a hub 
portion 2a, a disc portion 2b extending outward from the hub portion 2a 
and formed integrally therewith, and a rim 2c extending backward from a 
radially outer portion of the disc portion 2b. An annular recess is formed 
between the hub portion 2a and the rim 2c, and the viscous damper 
mechanism 4 is contained in the recess. Two rolling bearings 22 and 23 are 
mounted side-by-side on a radially outer portion of the hub portion 2a. 
Each of the bearings 22 and 23 is one of a lubricant sealing type having 
sealing members mounted on both its sides. A snap ring 24 is fitted in a 
radially outer surface of the hub portion 2a to regulate backward movement 
of the bearings. 
The second flywheel 3 is a substantially disc-shaped member, and its 
radially inner portion is removably fixed to a driven member 6 (as 
described below) of the viscous damper mechanism 4 by a bolt 21. In 
addition, a radially inner end of the second flywheel 3 regulates the 
backward movement of the rolling bearings 22 and 23. Further, a hole 3b is 
formed in the radially inner portion of the second flywheel 3 allowing the 
clutch disc 101 and the viscous damper mechanism 4 to communicate with 
each other. 
The viscous damper mechanism 4, shwon in FIG. 2, is mainly composed of a 
disc-shaped drive plate 5 fixed to the first flywheel 2, a disc-shaped 
driven member 6 having its radially inner portion supported on the first 
flywheel 2 through the rolling bearings 22 and 23, coil springs 12a, 12b 
and 12c for elastically connecting an input member comprising the first 
flywheel 2 and the drive plate 5 and the driven member 6 to each other in 
the circumferential direction, the above members being shown in FIGS. 2 
and 3. The viscous damper mechanism 4 further includes a viscous damper 
part 7 for damping torsional vibration by viscosity of fluid, as indicated 
in FIG. 2 and described in grerater detail below. The viscous damper 
mechanism 4, has an annular chamber 7a formed by the first flywheel 2, the 
drive plate 5, and the driven boss 6a of the driven member 6 is filled 
with viscous fluid. A radially outer end of the drive plate 5 is fixed to 
the rim 2c of the first flywheel 2 by a plurality of bolts 19. An annular 
sealing member 20 is disposed between a radially inner end of the drive 
plate 5 and the driven boss 6a of the driven member 6. The sealing member 
20 and the above described sealing members of the bearings 22 and 23 seal 
a radially inner end of the above described annular chamber 7a. 
Since the drive plate 5 is mounted on the first flywheel 2 by the bolts, 
the viscous damper mechanism 4 can be replaced by removing the drive plate 
5. Consequently, the viscous damper mechanism 4 can be overhauled, thereby 
making it possible to cope with a large-sized vehicle. 
The driven member 6 is a casting member formed in a disc shape, and is 
disposed between the disc portion 2b of the first flywheel 2 and the drive 
plate 5. The driven member 6 has the driven boss 6a flanged backward from 
its radially inner portion, as described above. The rolling bearings 22 
and 23 are mounted on a radially inner portion of the driven boss 6a, and 
the radially inner portion of the second flywheel 3 is fixed to the driven 
boss 6a by the bolt 21. Six window holes 6b are formed circumferentially 
equidistant in a radially intermediate portion of the driven member 6. The 
window holes 6b extend in the direction of rotation, and coil springs 12a, 
12b and 12c are contained in the window holes 6b. 
As shown in FIG. 3, the coil springs 12c are respectively contained in the 
radially opposing two window holes 6b (the window holes in the vertical 
direction of FIG. 3) out of the six window holes 6b of the driven member 
6. The coil spring 12c abuts against end surfaces in the circumferential 
direction of the window hole 6b through spring sheets 13. The 
large-diameter coil spring 12a and the small-diameter coil spring 12b 
disposed therein are contained in each of the remaining four window holes 
6b. 
Although spring sheets 13 are disposed in both ends of the coil springs 12a 
and 12b, predetermined clearances are respectively ensured between the 
spring sheets 13 and the end surfaces in the circumferential direction of 
the window hole 6b in a torsion free state. The spring sheet 13 has a 
radially outer supporting part 13a and a boss 13b. The large diameter coil 
spring 12a has its radially outer portion supported on the radially outer 
supporting parts 13a of the spring sheets 13, and the small diameter coil 
spring 12b has its radially inner portion supported on the bosses 13b of 
the spring sheets 13. The coil springs 12a and 12b are prevented from 
interfering with each other because they are coaxially retained by the 
spring sheets 13. 
The first flywheel 2 and the drive plate 5 respectively have abutting parts 
which abut against ends of each of the spring sheets 13, whereby the input 
member comprising the first flywheel 2 and the drive plate 5 and the 
driven member 6 are elastically connected to each other in the direction 
of rotation. In FIG. 3, an abutting part 2e of the first flywheel 2 is 
illustrated. 
The viscous damper part 7 is mainly composed of an annular fluid chamber 
7a, and a stopper member 8 and a a slider element 10, hereinafter referred 
to as slide stopper 10 formed of an elastic resin material, which are 
disposed in the annular fluid chamber 7a. 
The annular fluid chamber 7a, described above, is further constructed to be 
enclosed by a radially inner surface of the rim 2c of the first flywheel 
2, a radially outer surface of the driven member 6, and the disc portion 
2b of the first flywheel 2 and the drive plate 5. It is filled with 
viscous fluid. Six stopper member 8 are disposed circumferentially 
equidistant in the annular fluid chamber 7a, and divide the annular fluid 
chamber 7a into six division chambers. The stopper member 8 is connected 
to the first flywheel 2 and the drive plate 5 by pins 9 so as not to be 
relatively rotatable. A choke C.sub.2 through which viscous fluid can pass 
between the division chambers is formed between a radially inner surface 
of the stopper member 8 and the radially outer surface of the driven 
member 6. Recesses 6c are formed between the window holes 6b on a radially 
outer edge of the driven member 6; each recess is concave and all are 
generally circumferentially equidistantly spaced apart from each other. 
Each recess is formed with inclined surfaces 6e (see FIG. 4) which serve 
as cam surfaces, as described further below. A liquid supplying hole 6d 
extending radially outward from the center of the window hole 6b and 
opening to the annular fluid chamber 7a is formed in the middle between 
the adjacent recesses 6c. This hole 6d is positioned in the center of the 
stopper member 8 in a torsion free state. 
The slide stopper 10 is formed of resin, and is disposed between adjacent 
stopper members 8. Within the chamber the stopper members 8 and the slide 
stoppers 10 further define first arcuate chambers 14 and a second arcuate 
chambers 15. The slide stopper 10 has its radially outer surface formed in 
a circular arc shape along the radially outer surface of the rim 2c and 
has its radially inner surface formed in a circular arc shape along the 
radially outer surface of the driven member 6. The slide stopper 10 has a 
projection 10a projected radially inward from its center. The projection 
10a is disposed in the recess 6c of the driven member 6 and divides it 
into a first sub-chamber 16 and a second sub-chamber 17. Each projection 
10a is provided with cam surfaces 10b. Further, a choke C.sub.1 through 
which viscous fluid can pass between the first sub-chamber 16 and the 
second sub-chamber 17 is formed between a radially inner end of the 
projection 10a and the bottom surface of the recess 6c. 
The choke C.sub.1 is so formed as to have a larger flow passage 
cross-sectional area than that of the choke C.sub.2. In addition, the 
inclined surfaces 6e of the recess 6c and the cam surfaces 10b of the 
projection 10a of the slide stopper 10 are complimentarily inclined. When 
any of the surfaces 10b and 6e abut one another, the choke C.sub.1 closes 
restricting fluid flow. If the cam surfaces 10b and the surfaces 6e are 
further pressed against one another during relative motion of the 
flywheels 2 and 3, the slide stopper 10 is urged radially outward due to 
the inclination of the surfaces 10b and 6e, as described below with 
respect to the force diagram in FIG. 6. 
A radially inner portion of the annular fluid chamber 7a is sealed by 
annular sealing members 11 formed of Teflon or heat-resistant and 
wear-resistant resin. The sealing members 11 are respectively disposed 
between the first flywheel 2 and the driven member 6 and between the drive 
plate 5 and the driven member 6. As shown in detail in FIG. 5, one of the 
sealing members 11 is movably disposed between an annular groove 2d formed 
in the first flywheel 2 and an end surface of the driven member 6. 
Although the sealing member 11 is disposed in the annular groove 2d, as 
indicated by a dotted line in FIG. 5, when no pressure is applied to the 
annular fluid chamber 7a, the sealing member 11 is moved to a position 
indicated by a solid line in FIG. 5, and when pressure P is applied, the 
radially inner portion of the annular fluid chamber 7a becomes sealed, the 
movement of the seal indicated in FIG. 5 by the arrow Z depicted within 
the seal 11. A similar annular groove is also formed in the drive plate 5, 
and the other sealing member 11 is disposed inside. 
The benefit of the above described construction is that it is not necessary 
to have radial projections extending from the driven member 6, thus radial 
outer surface can be processed of the driven member 6 can be processed and 
the choke C.sub.2 may be formed easily and precisely by lathe. 
Manufacturing costs are thus reduced, and since the slide stoppers 10 are 
formed separately, the formations of projections are made easy. 
Description is now made of operations of the flywheel assembly according to 
the above described embodiment. 
When torque is input to the first flywheel 2 from the crankshaft on the 
engine side, the torque is subsequently transmitted to the second flywheel 
3 through the driven member 6, the coil springs 12a, 12b and 12c, as well 
as the viscous damper mechanism 4. At this time, if torsional vibration is 
inputted from the engine, the coil springs 12a, 12b and 12c repeatedly 
expand and contract, and the viscous damping part 7 produces a viscous 
resistance force to damp torsional vibration. 
With reference to FIG. 4, description is now made of operations at the time 
of relative rotation between the first flywheel 2 and the second flywheel 
3. 
When torque is input to the first flywheel 2 from the crankshaft on the 
engine side, the first flywheel 2 and the drive plate 5 are rotated 
relative to the driven member 6. The first flywheel 2 and the drive plate 
5 then rotate in the direction of rotation R.sub.1 away from their 
position in a torsion free state shown in FIG. 4. When the drive plate 5 
rotates in the direction of rotation R.sub.1 relative to the driven member 
6, the slide stopper 10 is similarly moved in the direction of rotation 
R.sub.1. Consequently, the volume of the second sub-chamber 17 is 
decreased and at the same time, the volume of the first sub-chamber 16 is 
increased. Specifically, fluid in the second sub-chamber 17 flows to the 
first sub-chamber 16 through the choke C.sub.1 as the slide stopper 10 is 
moved. Since the flow passage cross-sectional area of the choke C.sub.1 is 
large, the viscous resistance thereof is small. In addition, only the coil 
spring 12c is compressed in a range of small torsional angle, while the 
coil springs 12a and 12b are not compressed until the spring sheet 13 
abuts against the window hole 6b of the driven member 6. Consequently, low 
rigidity and small viscosity are exerted up to the point where the spring 
seat 13 abuts against the window hole 6b (i.e. a small torsional 
displacement angle). 
If the torsional displacement angle in the direction of rotation R.sub.1 is 
increased, the projection 10a of the slide stopper 10 abuts against the 
end surface of the recess 6c of the driven member 6 (see FIG. 6). 
Consequently, the choke C.sub.1 is closed and then the choke C.sub.2 
functions. The projection 10a is pressed against the end surface of the 
recess 6c, i.e. cam surface 10b engage surfaces 6e, a force A 
perpendicular to both abutting inclined surfaces is produced. The force A 
can be separated into a circumferential component of force B and a radial 
component of force C. The component of force C and a centrifugal force 
cause the slide stopper 10 to be pressed radially outward, whereby the 
radially outer surface of the slide stopper 10 is pressed against the 
radially inner surface of the rim 2c, and thus eliminating any clearance 
therebetween. If the first flywheel 2 continues to rotate relative to the 
slide stopper 10, where the stopper 10 is fixed to the driven member 6, a 
large resistance force is produced therebetween due to dry friction. The 
resistance force can be adjusted by manipulation of the complimentary 
angles of the abutting inclined surfaces 10b and 6e of the projections 10a 
and the recess 6c. 
If the torsional angle shown in FIG. 6 is further increased to that shown 
in FIG. 7, the coil springs 12a and 12b start to be compressed. In the 
angular displacement range where springs 12a and 12b are compressed, high 
rigidity characteristics or responses are obtained. At the same time, 
fluid in the first arcuate chamber 14 flows into the second arcuate 
chamber 15 through the choke C.sub.2. Since the flow passage 
cross-sectional area of the choke C.sub.2 is small, large viscous 
resistance is experienced. The above described dry frictional resistance 
is added to the viscous resistance, thereby obtaining a large resistance 
force. 
Furthermore, the stopper member 8 is moved in the direction of rotation 
R.sub.1 at this time, whereby the liquid supplying hole 6d of the driven 
member 6 opens to the second arcuate chamber 15. Therefore fluid, 
accumulated in the window hole 6b of the driven member 6, quickly flows 
into the second arcuate chamber 15 by the centrifugal force and an 
increased attraction force from the second arcuate chamber 15. Since the 
inside of the window hole 6b is a place where the largest amount of 
viscous fluid is accumulated in the radially inner portion of the annular 
fluid chamber 7a, a sufficient amount of fluid can be returned to the 
annular fluid chamber 7a, thereby making it difficult to cause the 
shortage of fluid in the annular fluid chamber 7a. 
If the torsional angle shown in FIG. 7 is increased to that shown in FIG. 
8, the stopper member 8 abuts against the slide stopper 10. Consequently, 
the relative rotation between the first flywheel 2 and the drive plate 5 
and the driven member 6 is constrained. 
FIG. 9 is a diagram showing torsional characteristics of the flywheel 
assembly 1, where a solid line indicates static torsional characteristics, 
and a dotted line indicates dynamic torsional characteristics. In the 
static torsional characteristics, a region of small hysteresis torque 
H.sub.1 which can be seen in a range of small torsional angle is an angle 
range in which the slide stopper 10 is rotated relative to the driven 
member 6 so that the choke C.sub.1 functions. Large hysteresis torque 
H.sub.2 is produced by the choke C.sub.2. The reason why the small 
hysteresis torque H.sub.1 in a range of large torsional angle is seen is 
that when small torsional vibration (for example, combustion fluctuation) 
is caused in a state where the drive plate 5 is rotated through a 
predetermined angle relative to the driven member 6, the slide stopper 10 
is separated from the end in the circumferential direction of the recess 
6c of the driven member 6 so that the choke C.sub.1 functions. Since the 
small hysteresis torque H.sub.1 can be thus produced irrespective of the 
relative angle of the drive plate 5 with the driven member 6, it is 
possible to effectively damp slight vibration at the time of, for example, 
combustion fluctuation. 
In the dynamic torsional characteristics shown in FIG. 9, viscosity becomes 
significantly larger than the conventional one. The reasons for this are 
mainly as follows: 
.circleincircle. Since a sufficient amount of fluid is returned to the 
annular fluid chamber 7a from the window hole 6a of the driven member 6, 
it is difficult to cause the shortage of viscous fluid. 
.circleincircle. Since the sealing member 11 seals the annular fluid 
chamber 7a and the driven member 6 is integrally formed, little fluid 
leaks. 
.circleincircle. A dry frictional force produced by pressing the radially 
outer surface of the slide stopper 10 against the radially inner surface 
of the rim 2c is added to the viscosity. 
Since a large viscous damping force is exerted on such a large torsional 
angle, back-and-forth vibration of the body of an automobile at the time 
of tip-in and tip-out and vibration thereof at the time of starting the 
engine are restrained. 
Description will now made of method of assembly of the above described 
flywheel assembly 1. 
First, the rolling bearings 22 and 23 are forced into the radially inner 
portion of the driven boss 6a of the driven member 6. The driven member 6 
with the bearings 22 and 23 mounted thereon is mounted on the first 
flywheel 2. At this time, the bearings 22 and 23 are forced into the 
radially outer portion of the hub portion 2a of the first flywheel 2. The 
sealing member 11 is previously inserted into the annular groove 2d of the 
first flywheel 2. After the driven member 6 is mounted on the first 
flywheel 2, the snap ring 24 is mounted on the hub portion 2a. Further, 
the spring sheet 13 and the coil springs 12a, 12b and 12c are mounted on 
the driven member 6. The stopper members 8 are mounted in the annular 
fluid chamber 7a with the pins 9, and the slide stopper 10 is further 
inserted into the annular fluid chamber 7a. In this state, fluid (for 
example, grease) is put in a portion corresponding to the fluid chamber 
7a. The drive plate 5, an annular groove of which the sealing member 11 is 
inserted, is fixed to the rim 2c of the first flywheel 2 by the bolts 19. 
Subsequently, the sealing member 20 is inserted between the radially inner 
portion of the drive plate 5 and the radially outer portion of the driven 
boss 6a. 
After the viscous damper mechanism 4 is assembled in the above described 
manner, the second flywheel 3 is fixed to the driven boss 6a of the driven 
member 6 using bolts 21. 
In such an assembling method, the second flywheel 3 can be easily mounted 
and removed by removing or tightening the bolt 21. Moreover, in mounting 
and removing the second flywheel 3, the bearings 22 and 23 and the sealing 
member 20 need not be touched, thereby decreasing wear on the bearings 22 
and 23 and the sealing member 20; thus lengthening their usable lifespan. 
In another embodiment of the present invention, the position of the liquid 
supplying hole is changed, as shown in FIG. 10, thereby it is possible to 
adjust torsional characteristics. If a fluid supplying hole 51 is shifted 
in the direction of rotation R.sub.2, as shown in FIG. 10, the fluid 
supplying hole 51 openly communicates with the first arcuate chamber 14 at 
the time point where a slide stopper 10 abuts against a driven member 6 (a 
state shown in FIG. 6 in the above described embodiment). Consequently, a 
choke C.sub.2 does not function until the fluid supplying hole 51 is 
filled with a stopper member 8. The position and the size of a fluid 
supplying hole and the number of fluid supplying holes are thus changed, 
thereby to make it possible to adjust the torsional characteristics. 
In still another embodiment, an example in which a driven member and a 
driven boss are separately provided is shown in FIG. 11. In this case, the 
driven member in the above described embodiment is constituted by three 
driven plates 66. Wave-shaped inner teeth 66a are formed in a radially 
inner portion of the driven plate 66, and wave-shaped outer teeth which 
are engaged with the wave-shaped inner teeth 66a are formed in a radially 
outer portion of a driven boss 86. The driven plate 66 and the driven boss 
86 are thus separated from each other by a serration, whereby the 
deflection of a second flywheel 3 does not easily affect the driven plate 
66. As with the first embodiment, the present embodiment allows for easy 
removal of the second flywheel 3, improving duration in which the rolling 
bearings 82 and 83 are usable. The embodiment depicted in FIG. 11 also 
includes a seal member 80, which is similar to the seal 220 depicted in 
FIG. 2. 
Various details of the invention may be changed without departing from its 
spirit nor its scope. Furthermore, the foregoing description of the 
embodiment according to the present invention is provided for the purpose 
of illustration only, and not for the purpose of limiting of the invention 
as defined by the appended claims and their equivalents.