Endless belt power transmission systems or components – Positive drive belt – Belt formed of rigid links
Reexamination Certificate
2001-08-28
2004-10-19
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Positive drive belt
Belt formed of rigid links
C474S212000
Reexamination Certificate
active
06805646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a double-sided meshing type silent chain having meshing teeth on both inner and outer peripheral sides thereof for mesh with teeth of sprockets.
2. Description of the Related Art
Conventionally, as a timing chain used for transmitting rotation of an engine crankshaft to a cam-shaft or a shaft of an auxiliary device such as an oil pump, there is known a double-sided meshing type silent chain having meshing teeth on both inner and outer peripheral sides thereof so that the meshing teeth on the inner peripheral side of the chain rotate sprockets mounted to the crankshaft and camshaft, respectively, and the meshing teeth on the outer peripheral side of the chain rotate a sprocket mounted to the shaft of the auxiliary device (Japanese Patent Laid-open Publications Nos. HEI-11-166600 and HEI-11-257439).
When the known double-sided meshing type silent chain is wound around a driving sprocket mounted to an engine crankshaft, a first driven sprocket mounted to a camshaft of an intake valve mechanism and a second driven sprocket mounted to a camshaft of an exhaust valve mechanism, the meshing teeth on the inner peripheral side of the chain mesh with the respective teeth of the driving and driven sprockets. Thus, all the sprockets rotate in the same direction. In the case where the meshing teeth on the outer peripheral side of the chain mesh with a sprocket mounted to the shaft of an auxiliary device such as an oil pump disposed on the outer peripheral side of the chain, the sprocket of the auxiliary device rotates in a direction opposite to the direction of rotation of the driving sprocket mounted to the crankshaft (Japanese Utility Model Registration No. 2553206).
FIGS. 13 and 14
show one example of the conventional double-sided meshing type silent chains. As shown in these figures, the double-sided meshing type silent chain
51
includes a plurality of interleaved link plates
55
,
56
each having a pair of meshing teeth
52
and a pair of pin-accommodation holes
53
, the link plates
55
,
56
being connected with one another by connecting pins
57
in an endless fashion in such a manner that the meshing teeth
52
project from both inner and outer peripheral sides of the chain
51
. The link plates
55
,
56
have a flat back surface
54
on a side thereof which is opposite to the front side on which the meshing teeth
52
are formed.
The link plates
55
,
56
are oriented such that the meshing teeth
52
of plural laminated inner link plates
55
located centrally in the width direction of the chain
51
project inwardly with respect to the chain
51
, and the meshing teeth
52
of two adjacent outer link plates
56
located at each end in the width direction of the chain
51
project outwardly with respect to the chain
51
. An outermost one of the outer link plates
56
which is located at each widthwise end of the chain
51
has pin-accommodation holes
53
in which connecting pins
57
are press-fit.
A sprocket used for mesh with the meshing teeth
52
projecting inwardly from a central portion of the chain
51
comprises a general sprocket
64
(
FIG. 17
) which is designed for mesh with a single-sided meshing type silent chain. In
FIG. 17
, numeral
65
denotes teeth of the sprocket
64
, and numeral
66
denotes a shaft on which the sprocket
64
is mounted.
Another example of the conventional double-sided meshing type silent chain is shown in
FIGS. 20 and 21
. The double-sided meshing type silent chain
68
is composed of inner link plates
55
and outer link plates
56
in a like manner as the silent chain
51
shown in
FIGS. 13 and 14
. The silent chain
68
is, however, different from the silent chain
51
in that connecting pins
57
are rotatably fit in the pin-accommodation holes
53
in the outermost link plates
56
located at opposite widthwise ends of the chain, and retainer rings
69
located outside the outermost link plates are firmly secured to the connecting pins
57
for preventing removal of the connecting pins
57
.
When the conventional double-sided meshing type silent chains
51
,
68
are wound around the driving sprocket on the engine crankshaft and the respective driven sprockets of the intake and exhaust valve mechanisms as previously described, one side which is in contact with these sprockets is an inner peripheral side of the silent chain, and the opposite side which is in contact with another sprocket mounted on the shaft of auxiliary device located outside the silent chain is an outer peripheral side of the silent chain.
The conventional double-sided meshing type silent chain shown in
FIGS. 13 and 14
has a problem that since the connecting pins
57
are press-fit in the pin-accommodation holes
53
of the outermost link plates
56
, when the outer link plates
65
are used for driving the sprocket of the auxiliary device shaft, the strength of the outermost link plates
56
is greatly reduced at an inner peripheral portion extending around each pin-accommodation hole
53
by the effect of a stress which is exerted on the winner peripheral surface of each pin-accommodation hole
53
when the meshing teeth
52
of the outermost link plates
56
collide with the teeth of the sprocket at the onset of meshing engagement, and a tensile stress which has been created in the inner peripheral portions of the pin-accommodation holes
53
of the outermost link plates due to press-fit connection with the connecting pins
57
. The mechanical strength of the silent chain is considerably reduced.
The outermost link plates
56
undergo deformation or swelling occurring complicatedly in the radial direction of the connecting pins
57
when the connecting pins
57
and the pin-accommodation holes
53
are press-fit with each other. This makes it difficult for an engagement surface, such as an inside flank or an outside flank of meshing tooth, to keep a desired profile. Since the meshing accuracy is an important requirement for the silent chain, design of the silent chain should be done with the foregoing deformation of the outermost link plates
56
taken into consideration.
A sprocket
61
, which meshes with the meshing teeth of the outer link plates
56
, supports side surfaces of every other inner link plates
55
in the longitudinal direction of the chain. This may deteriorate the traveling stability of the chain, allowing widthwise vibration and twisting of the chain to occur.
When the teeth
52
of the outer link plates
56
and the teeth
62
of the sprocket
61
mesh with each other on the outer peripheral side of the double-sided meshing type silent chain
51
, meshing at a portion of the chain
51
located on a line A—A shown in
FIG. 14
occurs in a manner shown in
FIG. 15
, in which the inner link plates
55
(indicated by hatching) located next to the outer link plates
56
are in slide contact with opposite inside surfaces of the sprocket
61
to thereby guide the travel of the chain. However, at a portion of the chain
51
located on a line B—B shown in
FIG. 14
, meshing occurs in a manner as shown in
FIG. 16
, in which the inner link plates
55
located next to the outer link plates
56
are not in slide contact with the opposite inside surfaces of the sprocket
61
. This may allow the chain to vibrate in the width direction thereof, thereby deteriorating the traveling stability of the chain. In
FIGS. 15 and 16
, numeral
63
denotes a shaft of the sprocket
61
.
Even when a shoe
67
of a chain tensioner or of a guide member is disposed on a back surface side of the outer link plates
56
for guiding the chain, as shown in
FIGS. 18 and 19
, portions of the silent chain
51
located on the lines A—A and B—B of
FIG. 14
are guided in such a manner as shown in
FIGS. 18 and 19
, respectively, in which only one of two adjacent outer link plates (indicated by hatching) is in sliding contact with the shoe
67
at each widthwise end of the chain. This arrangement increases surface pressure acting on the shoe
67
, thereby accelerating wear of the shoe
Kozakura Nobuto
Sato Toshifumi
Bucci David A.
Howson and Howson
McAnulty Timothy
Tsubakimoto Chain Co.
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