Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Load responsive tension adjuster or shifter
Reexamination Certificate
2000-01-12
2003-02-25
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Load responsive tension adjuster or shifter
C474S140000
Reexamination Certificate
active
06524202
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a chain tensioner for chain drives which is particularly, though not exclusively, suitable for use as a tensioner on the timing chain of a motor vehicle engine. The present invention is a chain tensioner particularly suited for use in confined spaces having a flat blade spring element mechanically interlocked with a plastic shoe. The shoe may be of rigid filled nylon and engages the chain to be tensioned.
Conventionally, a blade tensioner is used as the tensioner to apply tension force onto a chain. One form of blade chain tensioner is shown in U. S. Pat. No. 3,490,302, which is incorporated herein by reference. Another example of a prior art blade tensioner is shown in
FIGS. 9-11
herein.
As shown in
FIG. 9
, the conventional blade tensioner
100
is composed of a shoe
101
made of resin that extends in an arcuate form. Multiple blade springs
102
extend along shoe
101
and are mounted on shoe
101
. A metal base or plate
120
supports shoe
101
. A first projecting portion
110
, having a curved surface
110
a
is formed at the tip or free end of shoe
101
. A concave opening or groove
111
, for housing one end of blade spring
102
, is formed in the projecting portion
110
and shoe
101
. A triangular projecting portion
112
is formed on the fixed end of shoe
101
. A concave opening or groove
113
, for housing the other end of blade spring
102
, is formed in the projecting portion
112
and shoe
101
.
Attachment holes
121
,
122
are formed on base
120
. A sliding surface
125
is formed at the tip of base
120
so that projecting part
110
, at the tip or free end of the shoe
101
can slide on it while in contact. As shown in
FIG. 10
, projecting portion
112
, on the fixed end of shoe
101
and one end of metal pin
130
, is fixed at the center of plate
120
and, on the other hand, a through hole
112
a,
formed in pin
130
, is inserted in the through hole
112
a.
Stopper ring
131
, for shoe
101
, is mounted on the tip of pin
130
. With this composition, shoe
101
is rotatable ground pin
130
. A chain (not shown) runs on sliding surface
101
a
of shoe
101
. When the chain is in operation, a pressure load acts on the chain via shoe
101
, as shown in
FIG. 11
, when the spring
102
deforms.
Not only the chain, but also the tensioner is exposed to wide-ranging temperature fluctuation in an automotive application. Therefore, the components of the tensioner repeat thermal expansion and thermal contraction during automobile operation.
However, in a conventional blade tensioner, the resin shoe is supported by a metal pin and the coefficients of thermal expansion of these components differ greatly from one another. Therefore, the difference occurs in the magnitude of thermal deformation of the shoe and pin and, as a result, smooth rotation of the shoe around the pin is hindered when there are high temperature fluctuations. In this case, the shape of the groove for housing the spring end on the fixed end of the shoe deforms and the operation of the spring can be adversely affected, thereby the blade tensioner response deteriorates.
This invention addresses such conventional problems and offers a blade tensioner that provides reduced deterioration of tensioner response and improves durability.
SUMMARY OF THE INVENTION
The blade tensioner of one embodiment of the present invention includes a blade tensioner that applies tension force to a chain. The blade tensioner has a base or bracket and a chain sliding or contacting surface over which the chain slides. The chain-contacting surface is a surface portion of a resin or plastic shoe having an arcuate shape. The shoe is made of a plastic material which will “creep.” “Creep” is the term used in the art to describe the tendency of the shoe to plastically deform in a gradual manner under elevated load and temperature. The fixed or proximal end of the shoe is rotatably mounted to a pin. The pin is formed of metal, preferably steel or aluminum. The pin is fixed to the base. The free end or distal part of the shoe slides freely on an adjacent sliding surface formed on the base. A flat blade spring or multiple blade springs are positioned on the side of the shoe opposite the chain-contacting surface of the shoe. The springs have ends inserted into grooves, slots or housings formed in the opposite ends of the shoe. A bushing is press-fit into a bore formed in the fixed end of the shoe and the pin is inserted rotatably into the bushing. The bushing is made of metal, preferably steel or aluminum, and more preferably being of the same metal as the pin. The bushing is press-fit on the fixed end of the blade shoe. Both the bushing and the pin are made of metal.
Therefore, different from a conventional blade tensioner, the difference in magnitude of thermal deformation of the bushing and pin is small, even with large temperature fluctuations, so that the clearance between these two components can be maintained at a nearly constant value. Thereby, the shoe can rotate smoothly around the pin and, as a result, deterioration of response due to temperature fluctuation can be reduced.
The blade tensioner of a second embodiment includes a blade tensioner that applies tension force to a chain. The blade tensioner has a base or bracket and a chain sliding or contacting surface over which the chain slides. The chain-contacting surface is a surface portion of a resin or plastic shoe. The fixed or proximal end of the shoe is rotatably mounted to a metal pin. The pin is fixed to the base. The free end or distal part of the shoe slides freely on an adjacent sliding surface formed on the base. A flat blade spring or multiple blade springs are positioned on the side of the shoe opposite the chain-contacting surface of the shoe. The springs have ends inserted into grooves, slots or housings formed in the opposite ends of the shoe. A metal bushing is press-fit into a bore formed in the fixed end of the shoe and the pin is inserted rotatably into the bushing. The blade spring end adjacent the fixed end of the shoe is inserted between the bushing and the face of the shoe opposite the chain-contacting surface. The bushing may be any suitable shape in cross-section. Preferably, the cross-section of the bushing is circular or polygonal. The end of the blade spring adjacent the fixed end of the shoe is inserted between the bushing and the blade shoe.
Therefore defective operation of the blade spring due to thermal deformation of the groove or concave part for housing the blade spring which is formed in the fixed end of the shoe does not occur as in the conventional blade tensioner. Thereby, deterioration of response of the blade tensioner is reduced.
The blade tensioner of a third embodiment of the present invention has a shoe provided with an arcuate form mounted to a base. The shoe has a chain sliding surface on which the chain slides. The fixed end of the shoe is provided rotatable around a metal pin that is fixed to the base. A free end of the shoe opposite the fixed end is provided to slide on the sliding surface formed in the base. A blade spring is mounted on the surface of the shoe that is opposite the chain sliding surface of the shoe. A projecting portion is formed at the widthwise center of the blade spring mounting surface of the shoe adjacent the fixed end of the shoe. A stepped bushing made of metal with a center portion having a relatively small diameter is press-fit into a through hole formed in the projecting portion. Large diameter elements, flanges or portions are provided on both ends of the bushing. A cut-out into which the projecting portion of the shoe is inserted is formed in the blade spring adjacent the fixed end of the shoe, and the spring end is inserted in a gap between the large diameter portion of the bushing and the shoe.
The bushing can have either a circular or polygonal cross-section. When it is circular, the contact point of the blade spring with the circular surface of the bushing acts as a pivot for applying the load. When it is polygonal, su
Tada Naosumi
Tsuruta Shinji
Borg-Warner Automotive K.K.
Bucci David A.
Dziegielewski Greg
Fitch Even Tabin & Flannery
Hansen Colby
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