Chain drive assembly

There are provided means for pressing link plates constituting a chain drive assembly in the axial direction of pins, whereby a clearance between the link plates arranged adjacent to each other in the transverse direction of the chain assembly is eliminated, and in turn, a frictional resistance between the link plates is increased. Oscillation of the chain stringer is thus suppressed, and hence a noise due to such oscillation is eliminated.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a chain drive assembly, and more particularly to 
a silent chain for transmitting a drive power from a fluid type torque 
converter of an automatic transmission to an auxiliary transmission. 
2. Description of the Prior Art 
A drive power transmitting mechanism incorporating a silent chain has 
suffered from noise during transmission of a drive power, which noise is 
principally caused by two factors: one is an elastic vibration sound 
resulting from a shock upon meshing of a chain with sprockets (a sound of 
meshing); and the other is a resonant sound developed as a result that a 
shock upon meshing of a chain with sprockets is increased by oscillation 
of the chain stringer. The first factor may be eliminated by correcting a 
sprocket tooth configuration properly to lower a shock upon meshing 
between the chain and sprockets. In order to eliminate oscillation of the 
chain stringer which constitutes the second factor, it is effective to use 
an anti-oscillation member, such as a tension member or a chain guide. 
However, such anti-oscillation member requires a considerable space for 
installation, needs fine adjustment of a gap between the member and the 
chain, suffers wear and the accompanied dust or the like which would 
impose an undesirable influence on other functional portions of a chain 
drive assembly, and is costly to manufacture. 
As other countermeasures against the second factor, a system has been 
proposed, of eliminating a clearance between link plates, so as to provide 
a resistance to the bending movement of the chain, thereby preventing 
oscillation of the chain stringer. With such a system, an increase in 
component is avoided unlike the case where an anti-oscillation member is 
employed, and yet, a resistance to the bending movement of the chain 
largely changes even by a small difference in thickness between link 
plates, and by swelling. Such a system has accordingly failed to provide a 
proper and constant bending-resistance value, and suffered from the 
accommodation of one link plate to the other and accelerated wear during 
the service of the chain, which would lead to a lowered frictional 
resistance and eventually make the system useless. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to provide a silent 
chain, which is free of the drawbacks described, and wherein oscillation 
of the chain stringer is successfully prevented, for reduction of noise. 
According to the present invention, link plates are urged in the overlapped 
portions thereof in the axial direction of link pins by means of press 
members. Consequently, a clearance between the overlapped portions of link 
plates is eliminated to increase a frictional resistance between link 
plates, thus providing an increased resistance to the bending movement of 
the silent chain. The oscillation of the chain stringer is thus 
suppressed, and hence noise resulting therefrom is eliminated. 
A device for preventing oscillation of the chain stringer according to the 
present invention does not require any special space, unlike a tension 
unit or a chain guide, and provides a fixed contact frictional force 
between plates in the event that such link plates are worn. Use of spring 
means having a non-linear spring constant minimizes a time-dependent 
variation in contact frictional force between link plates, irrespective of 
a degree of wear of each link plate during the service of the chain. This 
device is fit for use in suppression of oscillation of the chain stringer. 
The spring means incorporated into the chain drive assembly act to prevent 
vibration of link plates themselves, whereas a shock upon meshing of the 
chain with sprockets is suppressed. 
According to the present invention, a single leaf spring urges the link 
plates in the peripheral portions of two pinned points thereof which are 
spaced apart from each other in the longitudinal direction of the chain. 
The number of spring means necessary for the chain drive assembly is 
eliminated, with an improved assembly efficiency as well as an improved 
operational efficiency. 
Respective leaf springs present an arcuate profile having a fixed 
curvature. Such a leaf spring is easy and less costly to manufacture. 
Another leaf spring according to the present invention is curved at a given 
curvature in the mid portion thereof and has a small arc in each end 
portion thereof, which is curved opposite to the central curve thereof. 
Since the curved central portion of the leaf spring is maintained in 
engagement with a guide plate or a link plate, the contact surface 
pressure depends on a configuration or profile of a leaf spring and 
maintained at a proper value. 
A leaf spring according to another embodiment of the present invention is 
curved at a given curvature in the mid-portion thereof and made linear in 
the opposite end portions, so as to eliminate contact surface pressure. 
According to the present invention, the length of a leaf spring on a pitch 
circle of a sprocket is smaller than that of a link plate, such that an 
interference between the leaf spring and a sprocket is avoided, without a 
risk of the leaf spring being broken.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, there are provided a fluid type torque converter 1 
having an output shaft 2 and an auxiliary transmission 3 having an input 
shaft 4. Output shaft 2 and input shaft 4 extend in parallel to each other 
and are operatively connected to each other by means of a silent chain 5. 
A drive power of an engine 6 is thus transmitted by way of silent chain 5 
to auxiliary transmission 3. 
A link plate 11 has in the lower portion thereof tooth-shaped portions 
respectively having an outer flank 12 adapted to mesh with or engage a 
tooth of a sprocket, and an imperfect circular through-hole 13. Thus, both 
tooth-shaped portions are in mirror-image relation to each other, as a 
whole, with respect to the center line of the plate (FIG. 2). 
A guide plate 14 has nearly sector-shaped slots 15 which are in 
mirror-image relation to each other with respect to the center line of the 
plate (FIG. 3). 
Referring to FIGS. 4 through 6 which show a first embodiment of the present 
invention, silent chain 5 comprises plural groups of link plates 11, each 
group consisting of two or more link plates. Link plates of one group are 
arranged adjacent to each other transversely of the chain and coupled at 
the opposite end portions to one ends of the link plates of the 
neighboring groups in an overlapped fashion by inserting link pins 18 and 
rivet pins 19 into holes 13 in each link plate. Dished disc springs 8 
having a central circular hole 9 are interposed between link plates 11 
positioned transversely outermost of the chain and guide plates 14, 
respectively. Each link pin 18 and each rivet pin 19 extend into circular 
hole 9 in each dished disc spring 8. It should be noted that each rivet 
pin 19 is closely fitted in respective hole 15 in each guide plate 14 
placed at each longitudinal side of the chain, so as to provide a 
predetermined spring force to each dished disc spring 8. 
Each dished disc spring 8 acts on the overlapped portions of link plates 11 
to urge the link plates axially inward of link pin 18, so that a clearance 
between the overlapped portions of link plates is eliminated, with an 
increased frictional resistance between link plates 11, resulting in an 
increased resistance to the bending movement of the silent chain. 
Oscillation of the chain stringer is thus suppressed, and hence a noise 
due to such oscillation. 
FIGS. 7 through 9 show another embodiment of the present invention. Silent 
chain 5 comprises plural groups of link plates 11, each group consisting 
of two or more link plates coincident with each other in the position in 
the longitudinal direction of the chain. Link plates 11 of one group are 
coupled at the opposite ends to one end of link plates 11 of the 
neighboring groups by inserting link pins 18 and rivet pins 19 into holes 
13 in respective link plate. Each link pin 18 extends transversely of the 
chain from the link plate positioned outermost on one longitudinal side of 
the chain to the link plate positioned outermost on the other side 
thereof. On the other hand, each rivet pin 19 extends through the 
outermost link plates on both sides of the chain to pierce through holes 
15 in guide plates 14 placed on the opposite sides of the chain and is 
crushed at the opposite ends thereof, so as not to be slipped therefrom. 
In this embodiment, a leaf spring 23 is disposed between guide plate 14 and 
neighboring link plates 11 positioned transversely outermost of the chain 
in a manner to span between the neighboring link plates 11. Leaf spring 23 
is in engagement with guide plate 14 at the mid portion thereof and with 
the neighboring outermost link plates 11 at the opposite ends thereof. 
Each dished disc spring is secured to the link plates, with its hole 
brought in register with one of holes 13 in each link plate. Leaf spring 
23 is larger in length than a distance between two holes 13 provided in 
each link plate at a spacing from each other in the longitudinal direction 
thereof, so that the leaf spring may urges or press the opposite pinned 
portions of link plates 11 axially of rivet pin 19. The number of leaf 
spring 23, on the whole, of the silent chain 5 is eliminated, as compared 
with that of dished disc springs, with the saving in time of assembly. In 
this embodiment, leaf springs 23 and guide plates 14 are in coincidence 
with each other in the position in the longitudinal direction of the chain 
such that an improved assembly efficiency is provided. 
FIG. 10 shows silent chain 5 and a sprocket 24 which are in cooperative 
relation to each other, wherein flank 12 of one tooth-shaped portion of 
each link plate 11 is in contact with a tooth 25 of sprocket 24. Each leaf 
spring 23 acts on the overlapped portion of the neighboring link plates 11 
to eliminate a clearance between the link plates, thereby providing an 
increased contact resistance between the link plates. The bending 
resistance of silent chain 5 is thus increased, such that oscillation of 
the chain stringer is suppressed, and a noise due to such oscillation is 
prevented accordingly. 
FIG. 11 shows a still further embodiment, wherein leaf spring 23 extends 
between neighboring guide plates 14. Leaf spring 23 is maintained, at the 
mid portion thereof, in engagement with the outermost link plate 11, and 
at the opposite ends thereof, in engagement with the neighboring guide 
plates, respectively. The leaf spring in this embodiment acts in like 
manner as that of FIG. 7 with the same results. In this embodiment, leaf 
spring 23 extends between the neighboring two guide plates 14 lined up 
with each other. This arrangement is advantageous for preventing 
interference between leaf spring 23 and sprocket 24. 
In the embodiment shown in FIG. 12, the outermost link plate 11 and guide 
plate 14 are positioned in coincidence with each other in the longitudinal 
direction of the chain, with leaf spring 23 interposed therebetween. In 
this embodiment, a relative movement of leaf spring 23 to link plate 11 or 
guide plate 14 is not caused. Leaf spring 23 in this embodiment enjoys its 
long service life, with freedom from wear. 
In the embodiment of FIG. 13, the outermost link plate and the second link 
plate as counted from the outside of the chain are placed in coincidence 
with each other in the longitudinal direction of the chain, with leaf 
springs 23 interposed therebetween. In the embodiment, relative movement 
of leaf spring 25 to the outermost link plate or the second link plate is 
prevented. This arrangement is effective for protecting leaf spring 23 
against wear. Leaf spring 23 is positioned transversely inward of the 
silent chain. This arrangement is desirable from the lubrication and 
durability points of view. 
In the embodiment of FIG. 14, leaf spring 23 is interposed between the 
second link plate as counted from the transversely outside of the chain 
and the third link plate in a manner that the mid portion thereof contacts 
the third link plate and the opposite ends thereof contact the second link 
plate. Leaf spring 23 in this embodiment is positioned nearer to the 
center line of the chain. This arrangement is desirable from the 
viewpoints of lubrication and durability of the leaf spring. 
In the embodiment of FIG. 15, a pair of leaf springs 23 and 26 are disposed 
between the second link plates and the third link plates, in a manner that 
each pair of springs are in an opposed relation to each other, with the 
mid portions thereof maintained in contact with each other and with the 
opposite ends thereof maintained in contact with the second link plate and 
the third link plate, respectively, thus presenting symmetrical profile. 
Stress per leaf spring is eliminated and leaf springs 23 and 26 are 
positioned nearer to the center line of the chain, such that the improved 
lubrication and durability are provided for the leaf spring. 
FIGS. 16 through 18 shows a variety of leaf springs different in profile. 
Respective leaf spring 23 has through-holes 29, both of which are 
symmetrical with respect to the center line of the spring, and into which 
are inserted link pin 18 and rivet pin 19. Leaf spring 23 shown in FIG. 16 
has an arcuate profile having a given curvature; leaf spring 23 of FIG. 17 
is curved in one direction in the central portion at a given curvature and 
curved in the direction opposite the one direction at each end thereof, 
thereby having a small arc portion 30 thereat; and leaf spring 23 of FIG. 
18 is curved in the central portion at a given curvature to terminate at 
the linear opposite end portions 31. The leaf springs in FIGS. 17 and 18 
bring the small arc portions 30 and linear end portions 31 into contact 
with link plate 11 or guide plate 14. The leaf spring of FIG. 16 is easy 
to manufacture. The leaf spring of FIG. 17 insures a constant contact 
surface pressure owing to the small arc portions 30, irrespective of a 
difference in size being incurred due to configuration. The leaf spring of 
FIG. 18 provides a descreased contact surface pressure owing to the linear 
end portions 31. 
FIG. 19 is a front view of leaf spring 23 incorporated into the silent 
chain assembly. Leaf spring 23 has circular through-holes 29, into each of 
which link pin 18 and rivet pin 19 are inserted in a manner that a radial 
cap a is left between the inner diameter of hole 29 and the link pin or 
the rivet pin. Each side edge 34 of leaf spring 23 is deviated 
longitudinally inward of the silent chain from each flank 12 of link plate 
11 positioned behind the leaf spring. More specifically, there is a 
difference 2d between an edge-to-edge distance b of the leaf spring on a 
pitch circle 33 of sprocket 24 and a flank-to-flank distance c of the 
tooth-shaped portions of link plate 11 positioned behind the leaf spring. 
Since d&gt;a, then the interference between each side edge of leaf spring 23 
and tooth 25 of sprocket 24 is avoided, without a risk that an excessive 
stress is created on leaf spring 23, which would lead to damaging the leaf 
spring.