Endless belt power transmission systems or components – Positive drive belt – Belt formed of rigid links
Reexamination Certificate
1999-12-23
2002-01-01
Marmor, Charles A (Department: 3681)
Endless belt power transmission systems or components
Positive drive belt
Belt formed of rigid links
Reexamination Certificate
active
06334829
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a double-meshing-type silent chain drive having a silent chain capable of meshing with sprockets located inside and outside the chain and also to a sprocket for use in the double-meshing-type silent chain drive.
2. Description of the Related Art
Conventionally, in some cases, a double-meshing-type silent chain capable of meshing with sprockets or toothed pulleys which are mounted on respective driven shafts located inside and outside the chain is used as a timing chain for transmitting rotational motion from the crankshaft of an engine to the cam-shaft of the engine or to the shaft of an auxiliary device such as an oil pump. A double-meshing-type silent chain is employed when driven shafts located inside and outside the chain must be rotated in opposite directions.
FIG. 17
shows a conventional double-meshing-type silent chain. In
FIG. 17
, an endless chain A
1
meshes with a sprocket A
2
located inside the chain A
1
as well as with a toothed pulley A
3
located outside the chain A
1
.
In the chain A
1
, links, each composed of three kinds of link plates having different shapes, are connected by pins A
4
. Specifically, guide link plates A
5
are disposed at the widthwise outermost sides of the chain A
1
as well as alternately along the longitudinal direction of the chain A
1
. As shown in
FIG. 18
, the guide link plate A
5
has a straight edge portion a formed at the inner circumferential side of the chain A
1
and two small meshing teeth b which are formed at the outer circumferential side of the chain A
1
to be located at longitudinally opposite end portions of the guide link plate
5
. The small meshing teeth b mesh with the toothed pulley A
3
.
A link plate A
6
is pin-connected with adjacent guide link plates A
5
at opposite end portions thereof such that the link plate A
6
is in contact with inside faces of the guide link plates A
5
. The link plate A
6
has two meshing teeth c formed at the inner circumferential side of the chain A
1
so as to mesh with the sprocket A
2
, as well as two small meshing teeth b formed at the outer circumferential side of the chain A
1
so as to mesh with the toothed pulley A
3
.
Plates A
7
and A
8
each have two meshing teeth c formed at the inner circumferential side of the chain A
1
so as to mesh with the sprocket A
2
, as well as a flat back face d formed opposite to the meshing teeth c.
Notably, the meshing teeth c formed at the inner circumferential side of the chain A
1
and the teeth of the sprocket A
2
, which mesh with the meshing teeth c, employ a standard tooth profile. By contrast, the meshing teeth b formed at the outer circumferential side of the chain A
1
and the teeth of the toothed pulley A
3
, which mesh with the meshing teeth b, employ a non-standard tooth profile.
The above conventional double-meshing-type silent chain employs three kinds of link plates having different shapes. Thus, in a step of manufacturing plates, link plate dies corresponding to the different link plate shapes must be used. Also, in an assembling step, a large number of kinds of component parts must be handled and controlled. As a result, manufacturing cost is high.
Also, since the profile of the meshing teeth formed at the outer circumferential side of the chain is smaller than the standard tooth profile, when a large load torque acts on the toothed pulley located outside the chain, the toothed pulley disengages from the chain and slips along the chain. Thus, a maximum torque that can be transmitted to the toothed pulley is smaller than that which can be transmitted to the sprocket located inside the chain. This significantly limits the selection of a device to be driven through engagement with the outer circumference side of the chain.
Further, the guide link plate has no meshing teeth at the inner circumferential side of the chain, but instead has the straight edge portion at the inner circumferential side of the chain. Consequently, the guide link plate is relatively heavy, causing an increase in the weight of the entire chain. This causes an increase in impact energy generated due to meshing engagement between the chain and the sprocket or between the chain and the toothed pulley when the chain travels, resulting in an increase in working noise.
Also, a heavy chain weight causes an increase in tension derived from a centrifugal force produced when the chain travels, accelerating wear of a shoe surface of a chain guide or the like as well as elongation of the chain. Particularly, when such a double-meshing-type silent chain is used as a timing chain for an engine, timing drive of the engine may be adversely effected.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a double-meshing-type silent chain drive which solves the above-mentioned problems involved in the prior art, enables a reduction in manufacturing cost through improvement of productivity, and enables transmission of a strong driving force between a double-meshing-type silent chain and a sprocket meshed with the chain along the outer circumference thereof.
Another object of the present invention is to provide a sprocket for meshing with the double-meshing-type silent chain, which is capable of suppressing chain vibration while maintaining high transmission efficiency.
To achieve the above object, the present invention provides a double-meshing-type silent chain drive comprising a double-meshing-type silent chain and a sprocket for meshing with the chain. The chain includes link plates having the identical side profile. Each link plate has two meshing teeth and a flat back face formed opposite to the meshing teeth. Two kinds of links are alternately arranged in the longitudinal direction of the chain, while the adjacent links are connected by pins. In one kind of link, an odd number of the link plates are disposed in the width direction of the chain. In the other kind of link, an even number of the link plates are disposed in the width direction of the chain. In each link, the link plates are oriented such that the meshing teeth of link plates located at widthwise opposite ends project outwardly with respect to the chain and the meshing teeth of the remaining link plates project inwardly with respect to the chain.
In the double-meshing-type silent chain of the present invention, all of the link plates have the identical side profile. Also, the outermost link plates of each link are oriented such that their meshing teeth project outwardly with respect to the chain. Thus, these outwardly projecting meshing teeth are meshed with a sprocket disposed outside the chain to thereby transmit power between the chain and the sprocket.
In each link, all the link plates except the outermost link plates are oriented such that the meshing teeth project inwardly with respect to the chain. These inwardly projecting meshing teeth are meshed with a sprocket disposed inside the chain to thereby transmit power between the chain and the sprocket.
Since all of the link plates have the identical side profile, the link plates can be manufactured through use of a single kind of link plate die. As compared to the case of a conventional chain of this kind composed of link plates having a plurality of side profiles, man-hours required for control of component parts can be reduced, and erroneous assembly can be prevented, thereby greatly improving productivity.
In contrast to the case of a conventional silent chain, large heavy guide plates having no teeth are not used, thereby reducing the weight of the entire chain.
Further, since meshing teeth which project outwardly with respect to the chain are profiled similarly to those which project inwardly with respect to the chain, there can be increased a torque that can be transmitted between the chain and a sprocket disposed outside the chain.
Preferably, the double-meshing-type silent chain of the present invention is such that, in each link, the meshing teeth of some link plates oriented in one direction project beyond the back faces of the r
Haginoya Tsutomu
Ichikawa Koichi
Kozakura Nobuto
Saito Toyonaga
Armstrong Westerman Hattori McLeland & Naughton LLP
Marmor Charles A
Pang Roger
Tsubakimoto Chain Co.
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