Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Tension adjuster has surface in sliding contact with belt
Reexamination Certificate
2000-01-13
2002-04-02
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Tension adjuster has surface in sliding contact with belt
Reexamination Certificate
active
06364796
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 prior art blade chain tensioner is shown in U.S. Pat. No. 3,490,302, which is incorporated herein by reference. Another example of a blade tensioner is shown in FIG.
4
and
FIG. 5
herein.
As shown in
FIG. 4
, the conventional blade tensioner
100
is composed of a shoe
101
made of resin that extends in an arc form, multiple blade springs
102
that extend along shoe
101
and are mounted on shoe
101
, and a metal base
120
that rotatably supports one end of shoe
101
.
A first projecting portion
110
is formed at the tip or free end of shoe
101
. Distal groove
111
, for housing one end of blade spring
102
, is formed in the projecting portion
110
. A second projecting portion
112
is formed on the fixed end of shoe
101
. Proximal groove
113
, for housing the other end of blade spring
102
, is formed in the second projecting portion
112
.
Attachment holes
121
,
122
are formed on base
120
. Sliding surface
125
, the curved surface
110
a
of which is formed in projecting portion
110
at the free end of shoe
101
, and which can slide in contact, is formed at the tip of base
120
. One end of metal pin
130
is fixed at the center of base
120
. Pin
130
passes through projecting portion
112
on the fixed end of shoe
101
and a stop ring (not shown) for shoe
101
is mounted on the free end of the shoe. The shoe
101
is thus rotatable around pin
130
.
In operation, the chain runs on sliding surface
101
a
of shoe
101
, and a pressure load from blade spring
102
(see
FIG. 5
) acts on the chain via shoe
101
. However, in the conventional blade tensioner, projecting portion
112
on the fixed end of the shoe moves in the direction of arrow a as shoe
101
deforms from a small radius curvature, shown in
FIG. 4
, to a large radius curvature, as shown in
FIG. 5
in shoe
101
. As a result, the degree of opening of the proximal groove
113
increases. When the degree of opening of proximal groove
113
changes, the contact position of the end part of blade spring
102
with groove
113
changes and the operation of the blade shoe is adversely affected causing deterioration of the response of the blade tensioner.
Similarly, for projecting portion
110
on the free end of shoe
101
, the contact position of the end part of blade spring
102
with distal groove
111
changes when the degree of opening of the open part of distal groove
111
changes due to deformation of shoe
101
. Accordingly, the operation of the blade shoe can be adversely affected.
The stiffness of shoe
101
cannot be made high in automotive applications where the temperature change is large, because a large bending stress acts at the portion of shoe
101
shown at the arrow A when shoe
101
deforms.
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 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 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 metal pin. The pin is fixed to the base. The free end or distal part of the shoe slides freely on an adjacent slide 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. The springs have ends inserted into grooves, slots or housings formed in the ends of the shoe. The proximal groove which receives the blade springs in the fixed end of the shoe extends longitudinally toward the tip of the fixed end of the shoe beyond the point where the pin passes through the shoe.
The blade tensioner of a second embodiment includes a blade tensioner to apply tension force to a chain. The blade tensioner is mounted to a base and has a chain sliding surface over which the chain slides. The sliding surface forms a portion of a shoe and has an arcuate shape. The free end of the shoe slides on a slide surface formed in the base. The fixed end of the shoe is mounted rotatably around a metal pin that is fixed to the base. The shoe is kept under load by a blade spring, the ends of which are inserted in a proximal and distal groove formed in the fixed end and the free end of the blade shoe respectively. The distal groove on the free end of the shoe extends longitudinally toward the tip of the free end of the shoe beyond the contact point between the free end of the shoe and the sliding surface of the base.
The blade tensioner of a third embodiment has blade springs whose ends contact a side of the proximal groove at a point which is located longitudinally beyond the attachment position of the pin in a direction toward the tip of the fixed end of the shoe.
The blade tensioner of a fourth embodiment has blade springs whose ends contact a side of the distal groove at a point which is located longitudinally beyond the contact point between the free end of the shoe and the sliding surface of the base.
The blade tensioner of a fifth embodiment, has a concave relief portion or channel formed in the proximal and distal grooves for preventing contact between the blade spring ends and the shoe.
The blade tensioner of a sixth embodiment has a concave space or opening that extends across the width or transverse direction of the blade shoe formed in the fixed and the free ends of the shoe. The concave space may be filled with fiber-reinforced resin.
The blade tensioner of a seventh embodiment has a guide portion that guides the free end of the blade shoe on the sliding surface. The guide portion extends from the edges of the sliding surface of the base. The guide part is provided on both sides in the width direction of the sliding surface and has convex curved members adjacent the blade shoe.
In the present invention, in one or more embodiments, the proximal groove on the fixed end of the blade shoe opens past the pin attachment point and extends further toward the tip of the fixed end of the shoe. Thereby, the degree of opening of the groove opening does not change greatly when the blade shoe deforms and, as a result, the change of the contact point between the groove and the end of the blade spring is reduced. Furthermore, deterioration of the response of the blade tensioner is reduced in this manner. In this case, generation of excessive bending stress in the blade shoe is prevented so that the durability of the blade tensioner is improved.
As for the distal groove on the free end of the blade shoe, it is also preferred that it extends past the contact point between the free end of the shoe and sliding surface or face on the base and extends further in a longitudinally outward direction. In this case, the change of the contact point between the tip of the blade spring and groove is reduced even when the degree of groove opening changes, so that an adverse effect on the operation of the blade shoe is reduced and deterioration of the response of the blade tensioner is reduced.
It is preferable that the contact point of the blade spring with the groove in the fixed end of the shoe
Adachi Ryohei
Nakamura Kensuke
Tada Naosumi
Tsuruta Shinji
Borg-Warner Automotive K.K.
Bucci David A.
Dziegielewski Greg
Fitch Even Tabin & Flannery
Hansen Colby
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