Sprocket assembly for silent timing chain system

Details Sprocket assembly for silent timing chain system Sprocket assembly for silent timing chain system

2000-07-25

2002-10-22

Marmor, Charles A (Department: 3681)

Endless belt power transmission systems or components

Positive drive pulley or guide roll

And additional coaxial surface for engaging same belt in...

C474S161000, C464S077000

Reexamination Certificate

active

06468173

ABSTRACT:

BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a timing chain system, and in particular, to an improved sprocket assembly for an automotive timing chain system capable of reducing noise.
(b) Description of the Related Art
As well known, internal combustion engines employ poppet valves that are operated by a camshaft that is driven by a crankshaft, with a suitable timing mechanism, and timing chains are used to transmit power and motion between the camshaft and the crankshaft. These chains are formed of ranks of links interleaved with adjacent ranks of links and having aligned apertures for receiving pivot pins to join the ranks and provide articulation of the chain as it passes around the driving and driven sprockets.
FIG. 1
shows a conventional internal combustion engine embodying a timing chain and sprocket system.
As shown in
FIG. 1
, a driving sprocket
51
on the crankshaft
60
and the driven sprocket
52
on the camshaft
61
are connected to each other by a timing chain
53
. The sprockets
51
and
52
have a plurality of teeth
62
equally spaced around the circumference of the driving and driven sprockets
51
and
52
, and the timing chain
53
consists of pairs of inside links
54
alternating with pairs of flanking guide links
65
joined by pivot pins
55
insulated by rollers
56
such that the chain
53
engages the driving and driven sprockets
51
and
52
.
The tension of the timing chain
53
is adjusted by a damper
58
and a tension device
59
mounted to an engine block.
In this configuration, the engine torque is transmitted to the drive sprocket
52
via the crankshaft
60
and consequently to the driven sprocket
52
on the camshaft
61
by the chain
53
such that the camshaft
61
rotates so as to operate a valve system.
FIG. 2
is an enlarged view of a camshaft sprocket engaged with the chain. As shown in
FIG. 2
, the chain
53
wraps on the sprocket
52
in a way that the pivot pins
55
having rollers
56
are inserted between the teeth
62
such that the teeth on the sprocket act to transfer a load from the chain
53
.
In this timing chain system, however, the friction surface between the rollers
56
insulating the pivot pins
55
and the driven sprocket
52
is large so backlash is generated, and in particular there exists a gap “C” between the pivot pin
55
and the roller
56
such that vibration noise is caused by engine resonance. Also, the rollers
56
generate noise when they contact the sprocket
52
.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above problems of the prior art.
It is an object of the present invention to provide an improved sprocket for a timing chain system allowing a reduction in backlash between the chain and the sprocket by integrally forming an auxiliary sprocket with the driving and driven sprockets, resulting in a reduction of noise.
It is another object of the present invention to provide an improved sprocket for a timing chain system capable of preventing vibration noise from between the pivot pin and the roller from being generated by integrally forming an auxiliary sprocket with the driving and driven sprockets.
To achieve the above object, a sprocket assembly for an automotive timing chain system comprises a main sprocket, an auxiliary sprocket mounted onto one side of the main sprocket for assisting the main sprocket, and an elastic member elastically coupling the auxiliary sprocket to the main sprocket for generating an elastic force between the main and auxiliary sprockets.


REFERENCES:
patent: 2659220 (1953-11-01), Cherry
patent: 3220273 (1965-11-01), Christian
patent: 3487706 (1970-01-01), Resener
patent: 4043214 (1977-08-01), Westlake
patent: 4175796 (1979-11-01), Boggs et al.
patent: 4261214 (1981-04-01), Watanabe et al.
patent: 5316524 (1994-05-01), Wong et al.
patent: 6267701 (2001-07-01), Mott

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