Torsional damper type flywheel device

A torsional damper type flywheel device including a drive side flywheel, a driven side flywheel rotatable relative to the drive side flywheel, at least one kind of spring mechanism connected between the drive side and driven side flywheels, and a friction mechanism arranged in series with the spring mechanism. An inertial plate is fastened to the drive side flywheel so as to construct one portion of the drive side flywheel so that a mass center of the drive side flywheel is shifted to an engine side to prevent the drive side flywheel from being deformed to an engine side when rotated at high speeds. Further, the engine side drive plate is bent at its radially intermediate portion so that a radially outer portion of the drive plate approaches the axial center of the drive side flywheel. As a result, an axial increase in width of the flywheel device due to the provision of the inertial plate is minimized. Further, a friction mechanism of the flywheel device is improved by integrally forming a thrust lining with a centering bushing and contacting only a radially outer portion of a cone spring with a thrust plate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a torsional damper type flywheel device 
divided into two masses coupled to each other via a torsional spring. 
2. Description of the Related Art 
A prior art torsional damper type flywheel device is disclosed in, for 
example, Japanese Utility Model Publication SHO 63-42950. The flywheel 
device, as illustrated in FIGS. 8 (Prior Art) and 9 (Prior Art), includes 
a drive side flywheel 10', a driven side flywheel 20' rotatable relative 
to the drive side flywheel 10', a K spring mechanism 30' directly 
connected between the drive side and driven side flywheels, a K1 spring 
mechanism disposed parallel to the K spring mechanism, and a friction 
mechanism disposed in series with the K1 spring mechanism so that the 
series combination of the K1 spring and the friction mechanism is 
connected between the drive side and driven side flywheels. 
The drive side flywheel 10' includes an outer ring 12', an inner ring 14' 
disposed radially inside outer ring 12', an engine side drive plate 16' 
and a clutch side drive plate 18'. The drive plates 16' and 18' are 
fastened to the outer ring 12' by a plurality of rivets 15'. The drive 
plates 16' and 18' are constructed of steel for the purpose of increasing 
the structural reliability and reducing an axial length of the flywheel 
device. The inner ring 14' and engine side drive plate 16' are fastened to 
an engine crankshaft by a plurality of bolts. Windows 17' and 19' for 
supporting the K and K1 spring mechanisms therein are formed in the engine 
side drive plate 16' and clutch side drive plate 18', respectively. 
However, as seen from FIG. 8 (Prior Art), the inertial mass of the assembly 
of the drive side flywheel 10' and the spring mechanisms is axially spaced 
from a surface S' of the flywheel device contacting the engine crankshaft 
by a distance a'. As a result, when the flywheel device is rotated at high 
speeds and a centrifugal force F' arts on a center of the inertial mass of 
the assembly of the drive side flywheel 10' and the spring mechanisms, a 
moment M' (M' =F' * a') causes the drive side flywheel 10' to axially 
incline toward the engine crankshaft side, because the engine side drive 
plate 16' is constructed of a thin steel plate and can easily be deformed. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a torsional damper type flywheel 
device having a drive side flywheel with an engine side drive plate 
constructed of steel wherein the drive side flywheel is prevented from 
axially inclining when rotated at high speeds. 
Another object of the invention is to provide a torsional damper type 
flywheel device which can attain the above-described prevention of the 
inclining of the engine side flywheel without increasing the axial size of 
the flywheel device. 
Some improvements of structural components, for example, a friction 
mechanism, will be necessary to maintain the axial size of the flywheel 
device compact without degrading the operation of the flywheel device. 
Another object of the invention is to provide such improvements of the 
friction mechanism. 
In accordance with the present invention, the object can be attained by a 
torsional damper type fIywheel device including a drive side flywheel, a 
driven side flywheel coaxial with and rotatable relative to the drive side 
flywheel, and at least one kind of torsional spring mechanism connected 
between the drive side flywheel and the driven side flywheel. The drive 
side flywheel includes an outer ring, an inner ring disposed radially 
inside the outer ring, an engine side drive plate constructed of steel and 
disposed on an engine side of the outer ring, and a clutch side drive 
plate disposed on a clutch side of the outer ring. The engine side drive 
plate and the clutch side drive plate are fastened to the outer ring by a 
plurality of rivets, and the inner ring is fastened to the engine side 
drive plate. The drive side flywheel further includes an inertial plate 
disposed on an engine side of the engine side drive plate. The inertial 
plate is fastened to the assembly of the outer plate and the engine side 
and clutch side drive plates by the rivets. 
Each of the engine side drive plate and the driven plate is bent at a 
radially intermediate portion thereof so that a radially outer portion 
thereof approaches a center of the flywheel device in an axial direction 
of the flywheel device. 
A friction mechanism is further provided in series with the spring 
mechanism. The friction mechanism includes two thrust linings, a thrust 
plate, and a cone spring. One of the two thrust linings is integrally 
formed with an axially extending cylindrical centering portion. The cone 
spring presses the thrust plate at a radially outermost portion of the 
cone spring. The thrust plate is bent toward a radially outside portion of 
the cone spring at a radially outer portion of the thrust plate to form a 
step-like portion which guides the cone spring from the radially outside 
portion of the cone spring. 
Since the inertial plate is provided, the center of the inertial mass of 
the drive side flywheel, including the inertial plate and the spring 
mechanism, is shifted to an engine side by a certain amount so that a 
moment acting on the engine side drive plate is decreased. 
In a case where the engine side and clutch side drive plates of the drive 
side flywheel are bent at the radially intermediate portions thereof so 
that the radially outer portions of the engine side and clutch side drive 
plates approach the axial center of the drive side flywheel, the axial 
length of the drive side flywheel is prevented from increasing to a great 
extent despite the coupling of the inertial plate to the engine side drive 
plate, because the inertial plate is coupled to the engine side drive 
plate at the radially outer portion of the engine side drive plate. 
In a case where the above-described improvements of the friction mechanism 
are made, the thrust lining is centered to decrease abrasion of the 
lining. Further, an actual operating diameter of the cone spring is made 
large and the cone spring load is minimized so that durability of the cone 
spring is improved. Furthermore, the thrust plate can center the cone 
spring to prevent the occurrence of a non-uniform abrasion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to FIGS. 1 to 5, a torsional damper type flywheel device in 
accordance with the first embodiment of the invention will be explained. 
As illustrated in FIG. 1, the torsional damper type flywheel device 
generally includes a drive side flywheel 10, a driven side flywheel 20 
coaxial with and rotatable relative to the drive side flywheel 10, and at 
least one kind of spring mechanism 40 (a K spring, hereinafter) connected 
between the drive side flywheel 10 and driven side flywheel 20. 
The flywheel device may further include a control plate 30 rotatable 
relative to the drive side and driven side flywheels 10 and 20, a friction 
mechanism 50, and another kind of spring mechanism (not shown) which will 
be called a K1 spring hereinafter. The K spring 40 is directly connected 
between the drive side and driven side flywheels 10 and 20. The K1 spring 
is arranged in series with friction mechanism 50 to form an elastically 
connected Coulomb damper. The series combination of the K1 spring and 
friction mechanism 50 is connected between the drive side and driven side 
flywheels 10 and 20 in parallel with the K spring 40. The K1 spring and 
friction mechanism 50 are connected to each other via control plate 30. 
The parallel arrangement of the K spring 40 and the elastically connected 
friction mechanism 50 provides two kinds of vibrational characteristics: a 
K characteristic and a K+K1 characteristic. When the torque acting on the 
K1 spring is small, for example, at a standard range of engine speeds, the 
friction mechanism 50 does not slide. As a result, both K spring 40 and 
the K1 spring operate so that the flywheel device operates in accordance 
with the K+K1 characteristic. Since no frictional force exists in the K+K1 
characteristic, an excellent torque variation absorbing effect is 
obtained. When the engine speed approaches the resonance point of the K+K1 
characteristic during an engine start-up and stopping and therefore the 
torque acting on the K1 spring becomes great, the friction mechanism 50 
momentarily slides to make the K1 spring ineffective, so that the flywheel 
device changes its characteristic from the K+K1 characteristic to the K 
characteristic, thereby passing through the resonance point of the K+K1 
characteristic without causing a resonance. 
Structures of the components of the flywheel device will be explained in 
more detail with reference to FIGS. 1 and 2. The drive side flywheel 10 is 
coupled to an engine crankshaft by a plurality of blots 2. The drive side 
flywheel 10 includes an outer ring 12 including a ring gear, an inner ring 
14 disposed radially inside outer ring 12, an engine side drive plate 16 
disposed on an engine side of the outer ring 12, and a clutch side drive 
plate 18 disposed on a clutch side of the outer ring 12. The engine side 
and clutch side drive plates 16 and 18 are constructed of steel to reduce 
the thickness of each plate without reducing the structural reliability. 
The engine side and clutch side drive plates 16 and 18 are fastened to the 
outer ring 12 by a plurality of rivets 15. The inner ring 14 is fastened 
to an engine crankshaft together with the engine side drive plate 16. The 
engine side and clutch side drive plates 16 and 18 include windows 17 and 
19, respectively, for housing the K spring mechanism 40 therein. 
As illustrated in FIG. 1, the drive side flywheel 10 further includes an 
annular inertial plate 13 which is coupled to the assembly of the outer 
ring 12 and the drive plates 16 and 18 from the engine side of the 
assembly. The inertial plate 13 is fixed to the drive plate 16 using the 
same rivets 15 that are used for coupling the drive plates 16 and 18 to 
the outer ring 12. The inertial plate 13 covers the windows 17 from an 
engine crankshaft side so as to prevent dust from entering the interior of 
the flywheel device through the windows 17 and also provides a guide for 
the K springs 40 housed in the windows 17. Since the inertial plate 13 is 
provided, a center of the inertial mass of the drive side flywheel 10 is 
shifted to an engine crankshaft side in an axial direction of the flywheel 
device. As a result, an axial distance a between the axial inertial mass 
center of drive side flywheel 10 and a surface S of the drive side 
flywheel contacting the engine crankshaft is reduced in comparison with 
the axial distance a' (see FIG. 8 (Prior Art)) of the conventional 
flywheel device. This reduction of the axial distance also decreases the 
magnitude of a moment M which will be generated on the drive side flywheel 
when it is rotated at high speeds. 
For the purpose of preventing the axial size of the flywheel device from 
being increased due to the provision of inertial plate 13, a step-like 
portion is formed at a radially intermediate portion of the engine side 
drive plate 16. As a result, a radially outer portion of the engine side 
drive plate 16 located radially outside the step-like portion approaches 
toward the axial center of the flywheel device. Since the inertial plate 
13 is coupled to the assembly of the drive plates 16 and 18 and the outer 
ring 12 at the radially outer portion of engine side drive plate 16, an 
increase in the axial size of the flywheel device is minimized. FIG. 5 
illustrates that the axial dimension b of the flywheel device with the 
step-like portion in engine side drive plate 16 is smaller than an axial 
dimension b' of a flywheel device without a step-like portion in the 
engine side drive plate 16 which will be explained hereinafter with 
reference to FIG. 6 as the second embodiment of the present invention. 
As illustrated in FIG. 1, a radially outer portion of the outer ring 12 
extends toward an engine crankshaft to form an axial protrusion 12a. A 
radially outer surface of the inertial plate 13 and a radially outer 
surface of the engine side drive plate 16 engage a radially inner surface 
of the axial protrusion 12a. Due to the axial protrusion 12a, the inertial 
mass center is further shifted toward an engine crankshaft so that the 
moment M is further reduced. Further, since the axial protrusion 12a can 
bear a radial force due to the engagement between the inner surface of 
axial protrusion 12a and the outer surfaces of inertial plate 13 and 
engine side drive plate 16, a shear force which may act on the rivets 15 
when the drive side flywheel 10 is rotated at high speeds will be reduced 
to a great extent, and the structural reliability of the drive side 
flywheel 10 increases. 
As illustrated in FIG. 3, the clutch side drive plate 18 includes locally 
thinned portions 18c at a radially inner portion thereof and 
circumferentially between the windows 19. The locally thinned portions 
make the clutch side drive plate lighter further shifting the inertial 
mass center toward the engine crankshaft so that the moment M is further 
reduced. The locations of the locally thinned portions 18c are determined 
to maximize a rotational balance. The clutch side drive plate 18 includes 
first portions 18a with a greater width and second portions 18b with a 
smaller width. Since the thinned portions 18c are formed at radially inner 
portions of the first portions 18a, a stress line generated in the outer 
portion of the clutch side drive plate 18 is prevented from flowing toward 
radially inside corners of the windows 19. As a result, local stress 
concentration is unlikely to be caused at the corners of the windows 19, 
and the structural durability of the clutch side drive plate 18 increases. 
The driven side flywheel 20 is coupled to a power train of a vehicle via a 
clutch. The driven side flywheel 20 includes a flywheel body 22 axially 
opposing the drive side flywheel 10 and a driven plate 24 coupled to the 
flywheel body 22 by a plurality of bolts 26. The drive side flywheel 20 is 
rotatably supported by the inner ring 14 of the drive side flywheel 10 via 
a bearing 4 so that the drive side and driven side flywheels 10 and 20 are 
rotatable relative to each other about the axis of the flywheel device. 
The control plate 30 includes a pair of control plate elements coupled to 
each other by a plurality of rivets 32. Each control plate element 
includes an annular portion 30a and an arm 30b extending radially 
outwardly from the annular portion 30a. The control plate 30 detachably 
engages the K1 spring mechanism in a circumferential direction of the 
flywheel device at the arm 30b. The control plate 30 also slidably engages 
the friction mechanism 50 at the annular portion 30a so that the K1 spring 
and the friction mechanism 50 are connected to each other via the control 
plate 30. Each control plate element includes a step-like portion at a 
radially intermediate portion thereof so that a radially outer portion of 
each control plate element located radially outside the step-like portion 
approaches the axial center of the flywheel device. This structure helps 
to minimize the axial size of the flywheel device. 
Each K spring mechanism 40 includes a K spring 42 extending in the 
circumferential direction of the flywheel device and spring seats 44 
disposed at opposite ends of the K spring 42. Each K spring mechanism 40 
is directly connected between the drive side and driven side flywheels 10 
and 20. Thus, a torque is transmitted between the drive side and driven 
side flywheels 10 and 20 via two routes: a first route including the K 
spring mechanism 40 and a second route including the K1 spring mechanism, 
control plate 30 and friction mechanism 50 (an elastically connected 
Coulomb damper) which is arranged parallel to the first route. Both the K 
spring mechanism 40 and the K1 spring mechanism are housed in the windows 
formed in the drive plates of the drive side flywheel 10 so as to be 
detachable from the window defining walls in the circumferential direction 
of the flywheel device. 
The friction mechanism 50 is located between the annular portion 30a of the 
control plate 30 and an annular portion 24a of the driven plate 24 of the 
driven side flywheel 20. The friction mechanism 50 is arranged in series 
with the K1 spring so that it comprises an elastically connected Coulomb 
damper which only momentarily slides when a torque acting on the friction 
mechanism 50 exceeds a predetermined frictional force Fr. The friction 
mechanism 50 includes a thrust lining 54 located between the annular 
portion 24a of the driven plate 24 and the annular portion 30a of one of 
the control plate elements, another thrust lining 52 located between the 
annular portion 24a of the driven plate 24 and the annular portion 30a of 
the other of the control plate elements, a thrust plate 56, and a cone 
spring 58. The thrust linings 52 and 54 are constructed of abrasive 
material, and the thrust plate 56 and the cone spring 58 are constructed 
of metal. 
In one of the thrust linings 54, a centering bushing 54a is integrally 
formed. An inner surface of the centering bushing 54a slidably contacts an 
outer surface of the annular portion 24a of the driven plate 24 so as to 
center the thrust lining 54, and an outer surface of the centering bushing 
54a slidably contacts an inner surface of the annular portion 30a of one 
of the control plate elements. For the purpose of understanding the 
features of the friction mechanism 50 of the flywheel device of the 
present invention, FIGS. 10 (Prior Art) and 11 (Prior Art) illustrate the 
structures of a friction mechanism of the conventional flywheel device. In 
the conventional device, a centering bushing 51' separate from a lining 
54' are bonded to each other. When the two members 51' and 54' are bonded 
in manufacture thereof, misalignment may happen between the two members. 
If such a misalignment exists, eccentric abrasion of the two members will 
occur, which will decrease the life of the friction mechanism 50. In 
contrast, in the present invention, since the centering bushing 54a is 
integrally formed in the thrust lining 54, misalignment between the 
centering bushing 54a and the thrust lining 54 does not happen and the 
durability of the friction mechanism 50 increases. 
An area of the cone spring 58 which presses the thrust plate 56 is limited 
to a radially outer portion of the cone spring 58. In contrast, the 
conventional cone spring 58' presses the thrust plate 56' at a radially 
inner portion of the cone spring 58'. Since the cone spring 58 presses the 
thrust plate 56 at a radially outer portion of the cone spring 58, an 
actual diameter of the press circle is increased and a load generated in 
the cone spring 58 is decreased. This improves the durability of the cone 
spring 58. 
A width of the thrust plate 56 in the radial direction is increased in 
comparison with that of the conventional thrust plate 56'. FIG. 12 
illustrates what kind of deformation would be caused if the width of the 
thrust plate 56' which was contacted by an outer portion of the cone 
spring 58' were not increased. A radially outermost portion of the thrust 
plate 56' would receive a force F and a moment M from the cone spring 58' 
and would be deformed toward a thrust lining 52', and a radially outer 
portion 52a' of the thrust lining 52' would be severely abraded. In 
contrast, since the thrust plate 56 is increased in the radial width in 
the present invention, such a deformation of the thrust plate 56 does not 
happen and the durability of the friction mechanism 50 increases. 
As illustrated in FIGS. 2 and 4, a step-like portion is formed in the 
thrust plate 56 to form a radially outer portion 56a axially staggered 
with respect to a radially inner portion. An inner surface of the radially 
outer portion 56a engages an outer surface of the cone spring 58 so that 
the cone spring 58 is centered relative to the thrust plate 56. Formation 
of the step-like portion increases the rigidity of the thrust plate 56 and 
the centering of the cone spring 58 assures a stable operation of the 
friction mechanism 50 through which the durability of the friction 
mechanism 50 is increased. 
FIG. 6 illustrates a flywheel device in accordance with a second embodiment 
of the present invention. In the second embodiment, an engine side drive 
plate 16' does not include a step-like portion, though an inertial plate 
13 is provided to the drive side flywheel 10. Therefore, the axial size of 
the drive side flywheel 10 is not as minimized as in the first embodiment. 
Since the other structures are the same as those of the first embodiment, 
detailed descriptions therefore will be omitted. 
FIG. 7 illustrates a clutch side drive plate 18 of a flywheel device in 
accordance with a third embodiment of the present invention. In the third 
embodiment, the thinned portion 18c formed in the clutch side drive plate 
18 according to the first embodiment is substituted by a cut, removed 
portion 18c' so that the cut portion constructs a radially inwardly 
opening recess in the clutch side drive plate 18. In the third embodiment, 
the axial center of inertial mass of the drive side flywheel 10 is shifted 
more to an engine crankshaft side than in the first embodiment. Since the 
other structures are the same as those of the first embodiment, detailed 
descriptions therefore will be omitted. 
Among the above-described structures, the provision of the inertial plate 
13 for axially balancing the drive side flywheel 10, the step-like 
structure of the engine side drive plate 16 for minimizing the axial size 
of the drive side flywheel 10, the integral formation of the centering 
bushing 54a with the thrust lining 54, the limitation of the pressing area 
of the cone spring 58 to the radially outermost portion thereof, and the 
centering of the cone spring 58 by the outer portion 56a of the thrust 
plate 56 can be applied to any other type of torsional damper type 
flywheel device, for example, a flywheel device having only one kind of 
spring mechanism as opposed to the flywheel device having two kinds of 
spring mechanisms in accordance with the above-described embodiment. 
Although a few embodiments of the present invention have been described in 
detail, it will be appreciated by those skilled in the art that various 
modifications and alterations can be made to the particular embodiments 
shown without materially departing from the novel teachings and advantages 
of the present invention. Accordingly, it is to be understood that all 
such modifications and alterations are included within the spirit and 
scope of the present invention as defined by the following claims.