Dynamic damper and coupling mechanism

The dynamic damper allows for a stable operation of a sub-clutch without complicating a structure of the sub-clutch. A dynamic damper 170 attached to a coupling mechanism 191 for coupling a crankshaft 90 of an engine and an input shaft 9 of a transmission includes a mass member 171, a sub-clutch 173 and an annular rubber member 172. The sub-clutch 173 has a release member 186 which can be directly coupled to an inner peripheral portion of a diaphragm spring 4b and is axially movable, and releases the interlocked relationship between the input shaft 9 and the mass member 171 when the crankshaft 90 and the input shaft 9 are released from each other. The annular rubber member 172 elastically couples the input shaft 9 and the mass member 171 together in a rotating direction when the sub-clutch 173 keeps the interlock relationship between the input shaft 9 and the mass member 171.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention generally relates a dynamic damper and a coupling mechanism. 
More specifically, the present invention relates to a dynamic damper which 
rotates with an input shaft of a transmission for dampening vibrations. 
2. Background Information 
In connection with such a dynamic damper and a coupling mechanism, the 
assignee has already developed related inventions disclosed in Japanese 
Laid-Open Patent Publication No. 6-48031 (1994) as well as other similar 
dynamic dampers and coupling mechanisms. 
In the above-mentioned prior arts, a second flywheel forming a mass portion 
is coupled to a drive and transmission system through a torsional damper 
mechanism to dampen a torsional vibration on the drive and transmission 
system only when a clutch disk is pressed against a first flywheel. 
Thereby, an operation impeding shifting of the transmission is suppressed 
in a disengaged state of a clutch while suppressing gear noises (neutral 
noises) of the transmission in a neutral state as well as vibrations and 
noises of the transmission during driving of a vehicle. 
In the above prior art, a frictional dampening mechanism (sub-clutch) is 
employed for coupling the second flywheel to the drive and transmission 
system. The sub-clutch is operated to engage by utilizing an axial 
movement of the clutch disk, which occurs when the clutch disk is pressed 
against the first flywheel. More specifically, a motion of a spline hub, 
which occurs in accordance with the movement of the clutch disk is 
utilized to engage frictionally the sub-clutch. 
However, the distance of axial movement of the clutch disk is very short. 
Further, due to deflection of a plate and others which couple the clutch 
disk to the spline hub, the distance of axial movement of the spline hub 
is shorter than the distance of axial movement of the clutch disk. 
Therefore, a member for engaging and disengaging the sub-clutch moves only 
a small distance. Accordingly, the sub-clutch may operate unstably. For 
avoiding this unstable operation, the sub-clutch may be adapted to require 
only a small movement for stable operation. However, this may complicate 
the structure of the sub-clutch. 
In view of the above, there exists a need for a dynamic damper and a 
coupling mechanism which overcomes the above-mentioned problems in the 
prior art. This invention addresses these needs in the prior art as well 
as other needs, which will become apparent to those skilled in the art 
from this disclosure. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a dynamic damper, which allows a 
more stable operation of the sub-clutch without complicating the structure 
of the sub-clutch. 
According to a first aspect of the present invention, a dynamic damper 
attached to a coupling mechanism includes a mass portion, a sub-clutch and 
an elastic portion. 
The coupling mechanism is a mechanism including a flywheel assembly, a 
clutch disk assembly and a clutch cover assembly. The coupling mechanism 
is operable to engage and disengage a crankshaft of an engine with and 
from an input shaft of a transmission in accordance with an axial movement 
of a release bearing. The flywheel assembly is non-rotatably coupled to 
the crankshaft of the engine. The clutch disk assembly is non-rotatably 
coupled to the input shaft of the transmission. The clutch cover assembly 
has a diaphragm spring, and frictionally engages the flywheel assembly and 
the clutch disk assembly by a biasing force of the diaphragm spring. The 
release bearing is fixed to an inner peripheral portion of the diaphragm 
spring. By the axial movement of the release bearing, the biasing force of 
the diaphragm spring is released, and the coupling between the crankshaft 
of the engine and the input shaft of the transmission is released. 
The mass portion can rotate in accordance with rotation of the input shaft 
of the transmission. The sub-clutch has a release member for releasing an 
interlocked relationship between the input shaft of the transmission and 
the mass portion when the coupling between the crankshaft of the engine 
and the input shaft of the transmission is also released. The release 
member can be directly coupled to the release bearing or the inner 
peripheral portion of the pressure plate, and can move axially. The 
elastic portion elastically couples the input shaft of the transmission 
and the mass portion together in a rotating direction when the sub-clutch 
operates the input shaft of the transmission and the mass portion in an 
interlocked manner. 
According to this aspect of the present invention, the coupling mechanism 
provided with the above dynamic damper mechanism for supplying a torque 
from the crankshaft of the engine through the flywheel assembly, the 
clutch cover assembly, the clutch disk assembly to the input shaft of the 
transmission. When the clutch disk assembly is frictionally engaged with 
the flywheel assembly, i.e., when the coupling mechanism is in the coupled 
state, the sub-clutch acts to operate the dynamic damper in accordance 
with the rotation of the input shaft of the transmission. Therefore, the 
dynamic damper dampens neutral noises in the neutral state of the 
transmission as well as noises thereof during driving. The above structure 
does not employ an inertia damper which avoids a resonance by mere 
addition of an inertia, but employs the dynamic damper. Therefore, it is 
possible to dampen the vibration of the input shaft of the transmission in 
a partial rotation range. Consequently, the vibration can be reduced to a 
level, which cannot be attained by the internal damper. 
For releasing the interlocked operation of the dynamic damper, the 
structure of the present invention is provided with the release member 
being directly coupled to the release bearing or the inner peripheral 
portion of the pressure plate for axial movement. The distance of movement 
of the release bearing and the inner peripheral portion of the pressure 
plate is larger than the distance in which the prior art clutch disk 
assembly moves a release member to release the sub-clutch in the prior 
art. Therefore, engagement and disengagement of the sub-clutch of the 
present invention can be performed more stably than the prior art. 
According to the dynamic damper of this aspect of the present invention, 
the member for operating the sub-clutch can axially move a longer distance 
than the prior art. Therefore, it is not necessary to complicate the 
structure compared with the prior art, and the operation of the sub-clutch 
can be stable. 
According to a second aspect of the present invention, the dynamic damper 
according to the first aspect further has such a feature that the release 
member is disposed between the input shaft of the transmission and the 
clutch disk assembly. The release member has an inner peripheral portion 
non-rotatably engaged with the outer peripheral portion of the input shaft 
of the transmission and an outer peripheral portion non-rotatably engaged 
with the inner peripheral portion of the clutch disk assembly. 
In this aspect, the clutch disk assembly and the input shaft of the 
transmission are coupled together in the rotating direction via the 
release member. The release member can transmit the motion of the release 
bearing disposed, for example, on the transmission side of the clutch disk 
assembly to the sub-clutch disposed on the engine side of the clutch disk 
assembly. Therefore, arrangement of the dynamic damper with respect the 
position of the release bearing can be determined more freely, and the 
space within the coupling mechanism can be used effectively for arranging 
the dynamic damper. 
According to a third aspect of the present invention, a coupling mechanism 
for coupling a crankshaft of an engine and an input shaft of a 
transmission includes a flywheel assembly, a clutch disk assembly, a 
clutch cover assembly and a dynamic damper. The flywheel assembly is 
non-rotatably coupled to the crankshaft of the engine. The clutch disk 
assembly is coupled to the input shaft of the transmission. The clutch 
cover assembly has a diaphragm spring, and frictionally engages the 
flywheel assembly and the clutch disk assembly. The dynamic damper of the 
flywheel assembly is the same as that according to the first or second 
aspect of the present invention. 
The foregoing and other objects, aspects advantages and salient features of 
the present invention will become apparent to those skilled in the art 
from the following detailed description, which, taken in conjunction with 
the annexed drawings, discloses a preferred embodiment of the present 
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring initially to FIG. 1, a partial cross-sectional view of a coupling 
mechanism 191 is illustrated which includes a dynamic damper 170 in 
accordance with one embodiment of the present invention. The coupling 
mechanism 191 is provided for engaging and disengaging a crankshaft 90 of 
an engine with and from an input shaft 9 of a transmission, and includes a 
dynamic damper 170 which is connected by a sub-clutch 173 to the input 
shaft 9 of the transmission for dampening a vibration of the transmission. 
The coupling mechanism 191 is basically formed of a flywheel assembly 160, 
a clutch cover assembly 4, a clutch disk assembly 5 and the dynamic damper 
170. A rotation axis of the coupling mechanism 190 is represented by line 
O--O in FIG. 1. 
The flywheel assembly 160 is non-rotatably coupled to the crankshaft 90 of 
the engine. The flywheel assembly 160 is basically formed of a flywheel 
161 and an annular or circular plate member 162. The flywheel 161 and the 
annular plate member 162 have their outer peripheral portions fixedly 
connected together. The inner peripheral portion of the annular plate 
member 162 is fixedly coupled to the crankshaft 90 of the engine by a 
plurality of circumferentially equally spaced apart bolts (only one 
shown). 
The clutch cover assembly 4 is basically formed of a clutch cover 4a, an 
annular diaphragm spring 4b and a pressure plate 4c which is biased toward 
the engine (leftward as viewed in FIG. 1) by the diaphragm spring 4b. The 
clutch cover assembly 4 can bias the pressure plate 4c toward the flywheel 
161 to hold the outer peripheral portion (frictional engagement portion) 
of the clutch disk assembly 5 between the flywheel 161 and the pressure 
plate 4c for frictional engagement between the flywheel assembly 4 and the 
clutch disk assembly 5. The clutch cover 4a is fixed at its outer 
peripheral portion to an end of the flywheel 161 near the engine (i.e., a 
right end as viewed in FIG. 1). The inner peripheral portion of the clutch 
cover 4a carries a radially middle portion (more specifically, a 
relatively outer portion) of the diaphragm spring 4b via wire rings 4d. 
The pressure plate 4c is held within the clutch cover 4a by the outer 
peripheral portion of the diaphragm spring 4b and others parts in a 
conventional manner. The pressure plate 4c moves axially when a release 
bearing 100 fixed to the inner periphery of the diaphragm spring 4b is 
moved along the rotation axis O--O (i.e., an axial direction) to apply a 
biasing force from the diaphragm spring 4b to the pressure plate 4c or 
releasing the biasing force thereof In this structure, the distance of 
axial movement of the release bearing 100 and the inner periphery of the 
diaphragm spring 4b is shorter than the distance of movement of the 
pressure plate 4c and the diaphragm spring 4b (see FIG. 1). 
A clutch disk assembly 5 is basically formed of a frictional engagement 
portion having friction facings 5a, a splined hub 5c and coil springs 5b. 
The coil springs 5b elastically couple the frictional engagement portion 
and the splined hub 5c together in the rotating direction. The inner 
periphery of the splined hub 5c has splines which engage the outer spline 
teeth 186c of a release member 186, which in turn has interval splines 
that engage the splines of the input shaft 9 of the transmission as will 
be described later. 
The dynamic damper 170 is basically formed of an annular mass member (mass 
portion) 171, an annular rubber member (elastic portion) 172, a support 
member 174 and a sub-clutch 173. The mass member 171 is disposed between 
the flywheel 161 and the annular plate member 162. The annular rubber 
member 172 elastically couples the mass member 171 to the support member 
174 in the circumferential, axial and radial directions. 
As shown in FIG. 2, the support member 174 is formed of a cylindrical 
portion 174a and an annular or circular plate portion 174b extending 
radially outward from the end of the cylindrical portion 174a nearest to 
the transmission. The inner peripheral surface of the cylindrical portion 
174a is fixed to an outer race of a ball bearing 107. The inner race of 
the ball bearing 107 is fixed to the inner peripheral portion of the 
annular plate member 162 of the flywheel assembly 160. Therefore, the 
support member 174 is rotatably carried by the flywheel assembly 160 but 
is unmovably coupled to the flywheel assembly 160 in the radial and axial 
directions by the ball bearing 107. The outer peripheral surface of the 
cylindrical portion 174a and a portion of the surface of the annular plate 
portion 174b opposed to the engine are fixedly coupled to the inner 
peripheral portion of the annular rubber member 172 in a conventional 
manner. 
Still referring to FIG. 2, the sub-clutch 173 is a mechanism for engaging 
and disengaging the above three components (i.e., mass member 171, annular 
rubber member 172 and support member 174) with and from the input shaft 9 
of the transmission. The sub-clutch 173 is of a frictional engagement type 
clutch. As shown in FIGS. 1 and 2, the sub-clutch 173 is basically formed 
of the foregoing support member 174 as well as a sub-clutch housing 181 (a 
first part), a friction plate 182 (a second part), an indirect member 184, 
a small diaphragm spring 185, a cylindrical release member 186, retainer 
members 187 and a transmission member 188. 
The sub-clutch housing 181 is formed of a cylindrical portion 181a and a 
frictional engagement portion 18 lb which extends radially inward from the 
end of the cylindrical portion 181a near the transmission (i.e., right end 
as viewed in FIG. 2). The surface of the cylindrical portion 181 a facing 
the engine (i.e., left side as viewed in FIG. 2) is in contact with the 
outer peripheral portion of the annular plate member 174b of the support 
member 174. Preferably, the cylindrical portion 181a of the sub-clutch 
housing 181 is fixedly coupled to the annular plate member 174b by rivets. 
The cylindrical portion 181 a is provided at its inner peripheral surface 
with engagement portions 181c which project radially inwardly to engage 
the indirect member 184 as discussed below. 
The friction plate 182 includes a thin annular plate with friction members 
183 which fixedly couple the axially opposite facing surfaces of its outer 
peripheral portion. The friction plate 182 is fixed at its inner 
peripheral portion to the release member 186. The outer peripheral portion 
of the friction plate 182 is located on the engine side with respect to 
the frictional engagement portion 181b of the sub-clutch housing 181. More 
specifically, the friction plate 182 is located between the frictional 
engagement portion 181b of the sub-clutch housing 181 and the support 
member 174. The friction plate 182 is normally biased against the 
frictional engagement portion 181b by the diaphragm spring 185, which 
presses the indirect member 184 against the friction plate 182. 
The indirect member 184 is an annular plate which is provided at its 
radially middle portion with an annular projection 184a projecting toward 
the engine. The indirect member 184 has its outer peripheral portion 
partially engaged with the engagement portion 181c of the sub-clutch 
housing 181. Therefore, indirect member 184 is axially movable with 
respect to the sub-clutch housing 181, but is circumferentially 
non-rotatable with respect to the sub-clutch housing 181. This arrangement 
suppressing rattling within the sub-clutch housing 181. This indirect 
member 184 is disposed on the engine side with respect to the outer 
peripheral portion of the friction plate 182. 
The small diaphragm spring 185 is formed of a radially outer biasing 
portion 185a having an annular and conical form and a plurality of release 
levers 185b extending radially inward from the radially outer biasing 
portion 185a. The radially outer biasing portion 185a is disposed on the 
engine side with respect to the indirect member 184. The annular plate 
portion 174b of the support member 174 prohibits the movement of the outer 
periphery of the radially outer biasing portion 185a toward the engine. 
Thus, the radially outer biasing portion 185a pushes the outer peripheral 
portion of the friction plate 182 against the frictional engagement 
portion 181b of the sub-clutch housing 181 through the projection 184a of 
the indirect member 184. The inner peripheral portion of the release 
levers 185b are in contact with the end surface of a cylindrical main 
portion 186a of the release member 186 which is opposed to the engine. 
The release member 186 is formed of the cylindrical main portion 186a 
having inner spline teeth 186b formed at the inner peripheral surface of 
the cylindrical main portion 186a, outer spline teeth 186c formed at the 
outer peripheral surface of the cylindrical main portion 186a and a fixing 
portion 186d extending radially outward from a portion of the cylindrical 
main portion 186a near the engine. The cylindrical main portion 186a is 
disposed radially between the splined hub 5c and the input shaft 9 of the 
transmission. The inner spline teeth 186b of the cylindrical main portion 
186a are non-rotatably engaged with the outer spline teeth of the input 
shaft 9 of the transmission. The splined hub 5c is non-rotatably supported 
on the cylindrical main portion 186b by the outer spline teeth 186b 
engaging the spline teeth of the splined hub 5c. Thus, the release member 
186 is axially movable and circumferentially non-rotatable with respect to 
the input shaft 9 of the transmission and the splined hub 5c. The inner 
peripheral portion of the friction plate 182 is fixed to the outer 
peripheral portion of the fixing portion 186d by a plurality of rivets or 
the like. A portion of the cylindrical main portion 186a near the 
transmission carries the annular transmission member 188 fixed thereto by 
the retainer members 187. 
The transmission member 188 comes into contact with the inner peripheral 
portion of the diaphragm spring 4b to transmit the moving force of the 
release bearing 100 toward the engine to the release member 186 when the 
release bearing 100 and the inner peripheral portion of the diaphragm 
spring 4b move toward the engine. A space having an axial length of S is 
normally kept between the transmission member 188 and the inner peripheral 
portion of the diaphragm spring 4b such that the diaphragm spring 185 
normally holds the friction plate 182 against the frictional engagement 
portion 181b of the sub-clutch housing 181. 
The operation of the coupling mechanism 191 and its the dynamic damper 170 
will now be described below. Rotation of the crankshaft 90 of the engine 
is transmitted to the input shaft 9 of the transmission through the 
flywheel assembly 160, clutch cover assembly 4 and clutch disk assembly 5 
in a relatively conventional manner. 
When the coupling mechanism 191 is in the engaged state shown in FIG. 1, 
the diaphragm spring 4b biases the pressure plate 4c toward the flywheel 
161, and the frictional engagement portion of the clutch disk assembly 5 
is held between the flywheel 161 and the pressure plate 4c. Thereby, the 
crankshaft 90 of the engine is coupled to the input shaft 9 of the 
transmission. In this engaged state, as best shown in FIG. 2, the small 
diaphragm spring 185 also biases the outer peripheral portion of the 
friction plate 182 toward the transmission, such that the sub-clutch 
housing 181 and the friction plate 182 are frictionally engaged. 
Therefore, the input shaft 9 of the transmission is operatively coupled to 
the mass portion 171, annular rubber member 172 and support member 174 of 
the dynamic damper 170 through the release member 186, friction plate 182 
and sub-clutch housing 181. 
When the dynamic damper 170 is operatively coupled to the input shaft 9 of 
the transmission, the dynamic damper 170 damps neutral noises of the 
transmission and noises during driving. In particular, the dynamic damper 
170 actively damps the vibration of the transmission in a partial rotation 
range. 
When the coupling mechanism 191 is to be released, the release bearing 100 
is moved toward the engine from the position shown in FIG. 1 in a 
conventional manner. When the release bearing 100 starts to move toward 
the engine, the outer peripheral portion of the diaphragm spring 4b moves 
toward the transmission so that the pressure plate 4c is released and 
moves toward the transmission. Thereby, the frictional engagement portion 
of the clutch disk assembly 5 is first released from the flywheel 161 and 
the pressure plate 4c, and the crankshaft 90 of the engine is decoupled 
from the input shaft 9 of the transmission. 
As the release bearing 100 moves toward the engine, the spaces disappears 
so that the release bearing 100 pushes against the transmission member 188 
to move the release member 186 toward the engine. This pushing force moves 
the release member 186 toward the engine such that the inner peripheral 
portion of the small diaphragm spring 185 and the friction plate 182 also 
move toward the engine. This movement decreases the biasing force applied 
by the small diaphragm spring 185 against the friction plate 182. Thus, 
the frictional engagement between the friction plate 182 and the 
sub-clutch housing 181 is released. Thereby, the mass member 171 and the 
annular rubber member 172 of the dynamic damper 170 no longer rotates 
together with the input shaft 9 of the transmission so that the inertia of 
the input shaft 9 of the transmission decreases. In the disengaged state 
of the coupling mechanism 191, a shifting operation of the transmission 
can be performed smoothly. 
The above structure directly utilizes the motion of the release bearing for 
releasing the interlocked relationship of the dynamic damper 170 with 
respect to the input shaft 9 of the transmission. Therefore, the operation 
of the sub-clutch 173 can be stabilized without complicating the structure 
of the sub-clutch 173, compared with a conventional structure in which the 
sub-clutch is operated by utilizing the motion of the spline hub or the 
like. 
For releasing the interlocked operation of the dynamic damper, the 
structure of the present invention is provided with the release member 
being directly coupled to the release bearing or the inner peripheral 
portion of the pressure plate for axial movement. The distance of movement 
of the release bearing and the inner peripheral portion of the pressure 
plate is larger than the distance in which the prior art clutch disk 
assembly moves a release member to release the sub-clutch in the prior 
art. Therefore, engagement and disengagement of the sub-clutch of the 
present invention can be performed more stably than the prior art. 
While only one embodiment has been chosen to illustrate the present 
invention, it will be apparent to those skilled in the art from this 
disclosure that various changes and modifications can be made herein 
without departing from the scope of the invention as defined in the 
appended claims.