U.S. patent application number 10/010592 was filed with the patent office on 2002-04-04 for blade-type chain tensioner.
This patent application is currently assigned to Borg-Warner Automotive, K.K.. Invention is credited to Adachi, Ryohei, Nakamura, Kensuke, Tada, Naosumi, Tsuruta, Shinji.
Application Number | 20020039941 10/010592 |
Document ID | / |
Family ID | 23915256 |
Filed Date | 2002-04-04 |
United States Patent
Application |
20020039941 |
Kind Code |
A1 |
Nakamura, Kensuke ; et
al. |
April 4, 2002 |
Blade-type chain tensioner
Abstract
A blade-type tensioner for chain drives which is suitable for
use as a tensioner of the timing chain of a motor vehicle engine.
The present invention is a chain tensioner particularly suited for
use in confined spaces having a blade spring element mechanically
interlocked with a plastic shoe. The shoe may be of rigid filled
nylon and engages the chain to be tensioned. The spring element is
interlocked to the plastic shoe by having ends inserted into
grooves formed in the opposite ends of the shoe. The shoe is
rotatably fixed to a base by way of a pin. The groove at the fixed
end of the shoe extends towards the tip of the fixed end of the
shoe past the pin attachment point. The groove at the free end of
the shoe extends toward the tip of the free end of the shoe past
the point at which the free end of the shoe bears upon a sliding
surface formed on the base.
Inventors: |
Nakamura, Kensuke;
(Wako-shi, JP) ; Adachi, Ryohei; (Wako-shi,
JP) ; Tada, Naosumi; (Mie, JP) ; Tsuruta,
Shinji; (Mie, JP) |
Correspondence
Address: |
BorgWarner Inc.
Patent Department
3001 West Big Beaver Road, Suite 200
P.O. Box 5060
Troy
MI
48007-5060
US
|
Assignee: |
Borg-Warner Automotive,
K.K.
|
Family ID: |
23915256 |
Appl. No.: |
10/010592 |
Filed: |
November 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10010592 |
Nov 8, 2001 |
|
|
|
09482233 |
Jan 13, 2000 |
|
|
|
Current U.S.
Class: |
474/111 ;
474/140 |
Current CPC
Class: |
G01G 19/021 20130101;
F16H 2007/0872 20130101; F16H 2007/0804 20130101; F16H 7/08
20130101 |
Class at
Publication: |
474/111 ;
474/140 |
International
Class: |
F16H 007/08; F16H
007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 1999 |
JP |
11-036886 |
Claims
What is claimed is:
1. A blade tensioner comprising: a base having a face; an arcuately
shaped shoe having a first side with a face for sliding engagement
with an associated chain, said shoe having a fixed end, said fixed
end being fixed to and rotatable around a pin fixed on said base
and said shoe having a free end opposite said fixed end, said free
end of said shoe being in sliding contact with said face formed on
said base; a blade spring provided along said shoe on an opposite
side of said shoe, said blade spring having end portions, said end
portions of said blade spring being inserted into grooves formed
respectively at said fixed end and said free end of said shoe, said
groove of said fixed end of said shoe extending toward a tip of
said fixed end beyond said pin, at least one of said grooves of
said shoe having a relief channel formed therein effective to
reduce contact between said blade spring end and said shoe.
2. The blade tensioner of claim 1, wherein said groove of said
fixed end of said shoe extends beyond a line (E) drawn
perpendicular to said face of said shoe through the center of said
pin.
3. The blade tensioner of claim 2, wherein said blade spring
contacts an end of said groove of said fixed end of said shoe at a
point toward said tip of said fixed end beyond said pin.
4. The blade tensioner of claim 3, wherein said relief channel
extends in a direction transverse to the longitudinal axis of said
shoe.
5. The blade tensioner of claim 4, wherein a guide is provided on
the slide face of said base adjacent to said free end of said shoe
to guide the travel of the free end of said shoe.
6. The blade tensioner of claim 5, wherein said guide is provided
with a pair of elements, said elements being located on opposite
edges of said slide face, each of said elements of said guide
having a convex curved face adjacent said edges of said free end of
said shoe.
7. The blade tensioner of claim 6, wherein a concave opening
extending in a direction transverse to the longitudinal axis of
said shoe is formed on said fixed end and said free end.
8. The blade tensioner of claim 7, wherein said concave opening is
filled with fiber-reinforced plastics.
9. The blade tensioner of claim 1, wherein said groove of said free
end of said shoe extends toward said tip of said free end beyond a
contact point between said free end and said slide face.
10. The blade tensioner of claim 9, wherein said groove of said
free end of said shoe extends toward said tip of said free end
beyond a line (F) drawn perpendicular to said face of said shoe
through said contact point.
11. The blade tensioner of claim 10, wherein said blade spring
contacts said groove of said free end of said shoe at a point
toward said tip of said free end beyond said contact point between
said free end and said slide face.
12. The blade tensioner of claim 11, wherein said fixed end and
said free end each have a channel formed therein adjacent said
blade spring ends, said channel extending in a direction transverse
to the longitudinal axis of said shoe.
13. The blade tensioner of claim 12, wherein a guide is provided on
the slide face of said base adjacent to said free end of said shoe
to guide the travel of the free end of said shoe.
14. The blade tensioner of claim 13, wherein said guide is provided
with a pair of elements, said elements being located on opposite
edges of said free end of said shoe, each of said elements having a
convex curved face adjacent said edges of said free end of said
shoe.
15. The blade tensioner of claim 14, wherein a concave opening
extending in a direction transverse to the longitudinal axis of
said shoe is formed on said fixed end and said free end.
16. The blade tensioner of claim 15, wherein said concave opening
is filled with fiber-reinforced plastics.
17. A blade tensioner comprising: a base having a face; an
arcuately shaped shoe having a first side with a face for sliding
engagement with an associated chain, said shoe having a fixed end,
said shoe fixed end being fixed to and rotatable around a pin fixed
on said base and said shoe having a free end opposite said shoe
fixed end, said shoe free end being in sliding contact with said
face formed on said base; a blade spring provided along said shoe
on an opposite side of said shoe, said blade spring having end
portions, said blade spring end portions being inserted into at
least a first groove formed at said fixed end and a second groove
formed at said shoe free end, a portion of said first groove
disposed between said pin and a tip of said fixed end, at least one
of said grooves having means for reducing contact between said
blade spring end and said shoe, said contact reducing means
disposed in said groove relative to said blade spring end effective
to reduce wear of said groove by said blade spring end.
18. The blade tensioner of claim 17, wherein the contact reducing
means are disposed in the first and second grooves.
19. The blade tensioner of claim 17, wherein the contact reducing
means are effective to reduce deterioration of the tension applied
to said associated chain by said tensioner due to interference
between said spring end and said shoe.
20. A method of providing a blade tensioner, the method comprising:
providing a base having a face; providing an arcuately shaped shoe
having a first side with a face for sliding engagement with an
associated chain, said shoe having a fixed end, said shoe fixed end
being fixed to and rotatable around a pin fixed on said base and
said shoe having a free end opposite said fixed end, said shoe free
end being in sliding contact with said face formed on said base;
providing a blade spring along said shoe on an opposite side of
said shoe, said blade spring having end portions; inserting said
blade spring end portions into a first groove formed at said shoe
fixed end and a second groove formed at said shoe free end, said
first groove having a portion disposed between said pin and a tip
of said fixed end; and forming a relief channel in at least one of
said grooves, said relief channel disposed in said groove relative
to said blade spring end effective to reduce contact between said
blade spring end and said shoe to reduce wear of said groove by
said blade spring end.
21. A blade tensioner comprising: a base having a face; an
arcuately shaped shoe having a first side with a face for sliding
engagement with an associated chain, said shoe having a fixed end,
said fixed end being fixed to and rotatable around a pin fixed on
said base and said shoe having a free end opposite said fixed end,
said free end of said shoe being in sliding contact with said face
formed on said base; a blade spring provided along said shoe on an
opposite side of said shoe, said blade spring having end portions,
a first of said blade spring end portions being inserted partially
into a first groove formed at said shoe fixed end, said first
groove having a terminus spaced from the tip of said shoe, a second
of said blade spring ends inserted into a second groove formed at
said shoe free end, the tip of said first blade spring end spaced
from said first groove terminus, said first groove having a portion
disposed between the tip of said shoe fixed end and said pin
effective to reduce the degree of opening of said first groove
during deformation of said shoe to reduce change of a contact point
between said first groove and said spring end.
22. The tensioner of claim 20, wherein said portion of said first
groove disposed between said tip of said fixed end and said pin is
effective to reduce deterioration of the tensioning of said
associated chain by said tensioner.
Description
BACKGROUND OF THE INVENTION
[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] Attachment holes 121, 122 are formed on base 120. Sliding
surface 125, the curved surface 110a 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.
[0006] In operation, the chain runs on sliding surface 101a 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.
[0007] 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.
[0008] 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.
[0009] 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
[0010] 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
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] It is preferable that the contact point of the blade spring
with the groove in the fixed end of the shoe is closer to the tip
of the fixed end than the pin attachment point. In this case,
opening of the groove on the fixed end of the blade shoe can be
reduced or eliminated.
[0020] In addition, it is preferable, in the distal groove on the
free end of the blade shoe, that the contact point between the
blade spring and free end is located further toward the tip of the
free end of the shoe than the contact point between the free end of
the shoe and the sliding surface of the base. In this case, opening
of the distal groove can be reduced or eliminated when the blade
shoe deforms
[0021] It is preferable to have a relief point or concavity formed
in the shoe adjacent the ends of the blade springs. The concavity
is a concave channel formed transversely across the grooves in both
ends of the shoe. This concave relief channel prevents interference
of the end of the blade spring with the blade shoe and defective
operation of the blade spring during operation of the tensioner is
prevented. Thereby, the deterioration of response of the blade
tensioner can be prevented. In addition, in such a case, wear of
the contact part of the blade shoe with the end of the blade spring
is prevented, so that the durability of the tensioner is
improved.
[0022] Formation of a concave space or opening that extends in the
width direction of the blade shoe at the fixed and free ends is
preferable and the weight of the blade shoe is reduced by it and
response of the tensioner is improved. In addition, filling of the
concave space with fiber-reinforced resin is preferable, and
improves the buckling strength of the ends of the blade shoe.
[0023] It is preferable to provide a guide element that guides the
sliding of the free end blade shoe on the sliding surface. The
guide element is attached to the sides to the sliding surface of
the base. It is preferable that this guide element be provided on
both widthwise sides of the sliding surface and a convex curved
surface be formed on the surface of each guide element adjacent the
sides of the free end of the shoe. Thereby the sliding resistance
between the guide element and the blade shoe is reduced and smooth
movement of the blade shoe is realized.
[0024] For a further understanding of the present invention and the
objects thereof, attention is directed to the drawings and the
following brief description thereof, to the detailed description of
the preferred embodiments of the invention and to the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a side view of the blade tensioner of the present
invention.
[0026] FIG. 2 is a cross-sectional view along indicated line II of
FIG. 1
[0027] FIG. 3 is a side view the blade tensioner of the present
invention.
[0028] FIG. 4 is a side view of a prior art blade tensioner
[0029] FIG. 5 is a side view of the blade tensioner of FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The embodiment mode of this invention is explained below
with the aid of the attached figures. FIG. 1 is a side view of a
blade tensioner of the present invention. FIG. 2 is a view along
the line described by arrow II of FIG. 1. FIG. 3 illustrates the
operation of the blade tensioner.
[0031] As shown in FIG. 1, blade tensioner 1 has a chain sliding
surface 2a on which the chain slides, a shoe 2 having an arcuate
form, multiple sheet spring-like blade springs 3 mounted along the
curved direction of the blade shoe 2 on the side opposite to the
chain sliding surface 2a of blade shoe 2, and a metal base 4 that
supports blade shoe 2.
[0032] A projecting portion 21 of the shoe is provided on the free
end of the blade shoe 2 and an arcuate surface 21s is formed in the
projecting part 21. On the other hand, flat sliding surface 41 is
formed at the tip of base 4 and the curved surface 21s of
projecting part 21 of blade shoe 2 and the surface 21s is made so
that curved surface 21s of projecting part 21 of blade shoe 2 can
slide on sliding surface 41 while in contact with sliding surface
41 at a point 21c. Distal groove 21a is formed in projecting part
21. The end of each blade spring 3 is inserted in distal groove 21a
and it is in contact with the shoe inside the groove at point
21g.
[0033] Projecting portion 22 is provided on the fixed end (opposite
the free end) of blade shoe 2 and proximal groove 22a is formed in
the projecting portion 22. The end of each blade spring 3 is
inserted in groove 22a and it is in contact with proximal groove
22a at point 22g.
[0034] On the other hand, one end of pin 5 is fixed near the center
of base 4 and pin 5 penetrates projecting portion 22 of blade shoe
2. Blade shoe 2 is supported rotatably by this pin 5. Stopper
washer 6, for blade shoe 2, is fixed to the tip of pin 5 to prevent
the shoe from becoming detached from the pin.
[0035] Groove 22a, formed in projection part 22 on the base side of
blade shoe 2, goes over the attachment point of pin 5 and extends
to the side of lip part 22b of projection part 22 that is the side
of tip part 22b on the side of the other end of blade shoe 2.
Concave relief part 22e is formed in the groove 22a to avoid
contact with rear end 3b of blade spring 3. Between blade spring 3
and groove 22a, contact point 22g is located further on the side of
tip part 22b of projection part 22 than the attachment point of pin
5.
[0036] Distal groove 21a formed in projecting portion 21 on the
free end of blade shoe 2 extends to contact point 21c of projecting
portion 21 and extends further in a longitudinal direction toward
the tip part 21b, i.e., on the endmost portion of the free end of
blade shoe 2. A concave channel or relief part 21e is formed
transversely across distal groove 21 a to avoid contact of tip 3a
of blade spring 3 with distal groove 21a. Contact point 21g,
between blade spring 3 and distal groove 21a, is located past a
line drawn perpendicular to the longitudinal axis of the blade
springs through the contact point 21c of projecting portion 21 with
sliding surface 41.
[0037] Concave spaces 21f, 22f that extend in the transverse or
width direction of the blade shoe are formed in projection parts
21, 22 of blade shoe 2. Formation of these concave spaces 21f, 22f
reduce the weight of blade shoe 2 and response of the tensioner is
improved.
[0038] Glass fiber reinforced resin FRP (Fiber Reinforced Plastic)
can be filled into the concave spaces 21f, 22f. In such a case, the
buckling strength of projection parts 21, 22 can be improved
further.
[0039] As shown in FIG. 2, a pair of guides 42, located at both
widthwise sides of blade shoe 2, are provided to sliding surface 41
of base 4. These guides 42 guide the sliding of projecting portion
21 of blade shoe 2 on sliding surface 41. In order to reduce the
sliding resistance between the surface and blade shoe 2, convex
curved surface 42a is formed on the side of each guide 42 adjacent
blade shoe 2. Smooth movement of blade shoe 2 is realized by these
convex curved surfaces 42a and the wear on these parts can be
reduced because convex curved surface 42a contacts the tip of the
blade spring 3.
[0040] When in operation, a chain (not shown) runs on the chain
sliding surface 2a of blade shoe 2. As shown in FIG. 3, chain
sliding surface 2a of blade shoe 2 pressure-contacts the chain so
that blade shoe 2 deforms to a flatter shape and thereby projecting
portion 21 at the tip slides on sliding surface 41 of base 4, while
blade shoe 2 rotates around pin 5. Each blade spring 3 deforms
similarly when blade shoe 2 deforms and the elastic repulsive force
of these blade springs acts 3 on the chain via blade shoe 2.
[0041] Proximal groove 22a, formed in projecting portion 22 on the
fixed end blade shoe 2, extends to the attachment point of pin 5
and further toward the tip 22b of projecting portion 22. Thereby,
the degree of opening of opening B of proximal groove 22a does not
change greatly when blade shoe 2 deforms. As a result, change of
the contact point between proximal groove 22a and blade spring 3 is
reduced. In this manner, deterioration of response of blade
tensioner 1 is reduced. In this case, generation of excessive
bending stress in blade shoe 2 is prevented, so that the durability
of blade tensioner 1 is improved.
[0042] Distal groove 21a, formed in projecting portion 21 on the
free end of blade shoe 2, extends beyond contact point 21c of
projecting portion 21 with sliding surface 41 to the tip part 21b
of projecting portion 21. Thereby, change of the contact point of
end part 3a of blade spring 3 with groove 21 a reduced even when
the degree of opening C of groove 21 on the tip side of blade shoe
2 changes. As a result, the adverse effect on the operation of
blade shoe 2 is reduced and deterioration of response of blade
tensioner 1 is reduced.
[0043] In addition, the opening of opening B on the fixed end of
proximal groove 22a of blade shoe 2 can be reduced when blade shoe
2 deforms because contact point 22g of blade spring 3, with groove
22a, in groove 22a, that is formed in projecting portion 22 on the
fixed end of blade shoe 2, is located more toward the tip portion
22b of projecting portion 22 than the pin attachment point.
[0044] Similarly, contact point 21g, of blade spring 3 with distal
groove 21a, in groove 21a, that is formed in projecting portion 21
on the free end of blade shoe 2, is located more toward the tip 21b
of projecting portion 21 than contact point 21c of projecting
portion 21 with sliding surface 41. Therefore, the opening of
opening C of groove 21a on the tip side of blade shoe 2 is reduced,
when blade shoe 2 deforms.
[0045] FIG. 3 includes lines E and F to illustrate defined points
on the tensioner shoe beyond which the grooves extend in a
longitudinal direction. In particular, line E is a line
perpendicular to the chain-contacting surface 2a of the shoe 2
which passes through the center of pin 5. The groove 22a extends
past line E towards the tip of the shoe shown at 22b. Similarly,
line F is a line perpendicular to the chain-contacting surface 2a
of the shoe 2 which passes through point 21c where the free end of
the shoe contacts the face 41 of the base 4. The groove 21a extends
past line F towards the tip of the shoe shown at 21b.
[0046] In addition, formation of concave relief parts 21e, 22e in
each groove 21a, 22a of blade shoe 2 prevents interference of ends
3a, 3b of blade spring 3 with blade shoe 2. The concave relief
parts are channels formed in the shoe ends transverse to the
longitudinal direction of the shoe. Thereby, operation of blade
spring 3 during operation of the blade tensioner 1 is improved and
deterioration of response of the blade tensioner 1 is reduced.
Also, in such case, wear on the contact point of blade shoe 2 with
blade spring ends 3a, 3b is prevented and, as a result, the
durability of the blade tensioner 1 is improved.
[0047] As detailed above, the proximal groove in the fixed end of
the blade shoe extends beyond the pin attachment point toward the
tip of the fixed end of the blade tensioner of this invention.
Thus, the change in the degree of opening of the opening of the
groove is reduced when the blade shoe deforms. As a result,
deterioration of response of the blade tensioner is reduced and, in
addition, in such a case, generation of excessive bending stress on
the blade shoe is reduced to obtain improved durability of the
blade tensioner.
[0048] In the blade tensioner of the present invention, the distal
groove on the free end of the blade shoe extends beyond the contact
point between the free end and the sliding surface toward the tip
of the shoe. Thus, the change of the contact point between the tip
of the blade spring and the groove is reduced for the distal groove
on the free end of the blade shoe, even when the degree of opening
of the distal groove is changed. Thereby, an adverse effect on the
operation of the blade shoe and deterioration of the response of
the blade tensioner is reduced.
[0049] While several embodiments of the invention are illustrated,
it will be understood that the invention is not limited to these
embodiments. Those skilled in the art to which the invention
pertains may make modifications and other embodiments employing the
principles of this invention, particularly upon considering the
foregoing teachings.
* * * * *