U.S. patent application number 09/867188 was filed with the patent office on 2001-11-15 for tensioner for applying tension to force transmitting member.
This patent application is currently assigned to NHK Spring Co., Ltd.. Invention is credited to Amano, Tanehira, Ishii, Kazuo, Kawanabe, Kenjiro, Kobayashi, Takao, Takahashi, Shigemasa.
Application Number | 20010041635 09/867188 |
Document ID | / |
Family ID | 26573014 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010041635 |
Kind Code |
A1 |
Ishii, Kazuo ; et
al. |
November 15, 2001 |
Tensioner for applying tension to force transmitting member
Abstract
A tensioner comprises shaft members that mate with each other by
means of thread portions. A first shaft member is rotatable with
respect to a casing and is restrained from moving in its axial
direction. A second shaft member, which is restrained from rotating
with respect to the casing, is movable in its axial direction. A
torsion spring applies torque in a first direction to the first
shaft member. A torque switching member, which can switch
frictional torque in association with the rotation of the first
shaft member, is provided between the first shaft member and the
casing.
Inventors: |
Ishii, Kazuo; (Kamiina-gun,
JP) ; Takahashi, Shigemasa; (Komagane-shi, JP)
; Amano, Tanehira; (Komagane-shi, JP) ; Kobayashi,
Takao; (Komagane-shi, JP) ; Kawanabe, Kenjiro;
(Ina-shi, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN &
LANGER & CHICK, PC
767 THIRD AVENUE
25TH AVE
NEW YORK
NY
10017-2023
US
|
Assignee: |
NHK Spring Co., Ltd.
Yokohama-shi
JP
|
Family ID: |
26573014 |
Appl. No.: |
09/867188 |
Filed: |
May 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09867188 |
May 29, 2001 |
|
|
|
PCT/JP99/06700 |
Nov 30, 1999 |
|
|
|
Current U.S.
Class: |
474/101 ;
474/135; 474/136 |
Current CPC
Class: |
F16H 2007/0857 20130101;
F16H 7/0831 20130101; F16H 7/08 20130101; F16H 2007/081
20130101 |
Class at
Publication: |
474/101 ;
474/135; 474/136 |
International
Class: |
F16H 007/08; F16H
007/12; F16H 007/22 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 1998 |
JP |
10-339685 |
Nov 18, 1999 |
JP |
11-328865 |
Claims
What is claimed is:
1. A tensioner comprising: a first shaft member rotatably inserted
in a casing so as to be restrained from axial movement and having a
first thread portion; a second shaft member having a second thread
portion mating with said first thread portion, axially movable with
respect to said casing, and restrained from rotation; a torsion
spring for generating torque capable of rotating said first shaft
member; and torque switching means for changing the turning torque
of said first shaft member in accordance with the rotational angle
of said first shaft member.
2. A tensioner according to claim 1, wherein said torque switching
means includes a torque switching member for changing frictional
torque depending on the rotational angle, narrow or wide, of said
first shaft member.
3. A tensioner according to claim 2, which comprises a receiving
member provided for rotation between an end face of said first
shaft member and said casing and an elastic member adapted to
couple said first shaft member and said receiving member when the
rotational angle of said first shaft member exceeds a given
value.
4. A tensioner according to claim 2, which comprises a receiving
member provided for rotation between an end face of said first
shaft member and said casing, a projection provided on said first
shaft member or said receiving member, and a recess having a
surface adapted to engage said projection to couple said first
shaft member and said receiving member when the rotational angle of
said first shaft member exceeds a given value.
5. A tensioner according to claim 2, which comprises a first
receiving member capable of receiving an end portion of said first
shaft member for rotation and adapted to rotate said first shaft
member while generating a small frictional force as long as the
rotational angle of said first shaft member is narrow and to rotate
with said first shaft member when the rotational angle of said
first shaft member exceeds a given value, and a second receiving
member provided between said first receiving member and said casing
and adapted to rotate said first receiving member while generating
a frictional force greater than said frictional force when said
first receiving member rotates.
6. A tensioner according to claim 5, which comprises an elastic
member adapted to couple said first shaft member and said first
receiving member when the rotational angle of said first shaft
member exceeds a given value.
7. A tensioner according to claim 5, which comprises a third
receiving member provided between said first shaft member and said
first receiving member and adapted to rotate said first shaft
member while generating a small frictional force as long as the
rotational angle of said first shaft member is narrow and to rotate
with said first shaft member when the rotational angle of said
first shaft member exceeds a given value.
8. A tensioner according to claim 7, which comprises a first
connecting elastic member provided between said first receiving
member and said third receiving member and adapted to couple said
first receiving member and said third receiving member when the
rotational angle of said third receiving member exceeds a given
value, and a second connecting elastic member provided between said
first shaft member and said third receiving member and adapted to
couple said first shaft member and said third receiving member when
the rotational angle of said first shaft member exceeds a given
value.
9. A tensioner according to claim 1, wherein said torque switching
means changes frictional torque at least three stages in accordance
with the rotational angle of said first shaft member.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Continuation Application of PCT Application No.
PCT/JP99/06700, filed Nov. 30, 1999, which was not published under
PCT Article 21(2) in English.
[0002] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Applications No. 10-339685,
filed Nov. 30, 1998; and No. 11-328865, filed Nov. 18, 1999, the
entire contents of both of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to a tensioner for
appropriately maintaining the tension of a force transmitting
member, such as an endless belt or endless chain, in a power
transmission mechanism that uses the force transmitting member.
[0004] A force transmitting member, such as an endless belt or
chain, is used in a power transmission mechanism that transmits
rotary motion to cam shaft in an engine of an automobile, for
example. In some cases, a tensioner is used to keep the tension of
the force transmitting member appropriate. FIGS. 21 and 22
individually show sections of a conventional tensioner. This
tensioner is provided with a casing 1. A first shaft member 2 and a
tubular second shaft member 3 are inserted in the casing 1. The
casing 1 is provided with a flange portion lb that has a mounting
hole la for fixation on an apparatus such as an engine. An external
thread portion is formed on the outer surface of the first shaft
member 2. An internal thread portion is formed on the inner surface
of the second shaft member 3. These external and internal thread
portions mate with each other. A rear end portion 2a of the first
shaft member 2 is inserted in a fitting hole 9 that is formed
inside the casing 1. The end face of the rear end portion 2a is in
contact with the inner surface of the casing 1. A torsion spring 4
is provided around the first shaft member 2. One end 4a of the
torsion spring 4 is anchored to the first shaft member 2, while the
other end 4b is anchored to the casing 1. If the spring 4 is
twisted, the repulsive force of the spring 4 generates torque that
causes the first shaft member 2 to rotate. The first shaft member 2
is rotatable with respect to the casing 1.
[0005] The cylindrical second shaft member 3 penetrates a sliding
hole 5a that is formed in a bearing 5. A shown in FIG. 22, both the
outer peripheral surface of the second shaft member 3 and the inner
peripheral surface of the sliding hole 5a are noncircular. Thus,
the second shaft member 3 is allowed to move in its axial direction
with respect to the bearing 5, and is prevented from rotating. If
the first shaft member 2 is rotated by means of the repulsive force
of the torsion spring 4, therefore, the second shaft member 3
generates an axial thrust without rotating. For example, the
repulsive force of the spring 4 acts in a direction such that it
causes the second shaft member 3 to project from the casing 1. A
moderate tension can be applied to the aforesaid force transmitting
member, the belt or chain, by applying this thrust to the force
transmitting member. If the second shaft member 3 pushes the force
transmitting member, a reactive force from the force transmitting
member acts on the shaft member 3. The shaft member 3 moves in its
axial direction to a position such that this reaction force (input
load) balances with the thrust of the shaft member 3 that is
generated by means of the torsion spring 4. Thus, the conventional
tensioner has a linear characteristic such that the input load is
proportional to the movement of the second shaft member 3.
[0006] The tension of the force transmitting member, the chain or
belt, continuously changes depending on the operating conditions of
the engine, for example. Since the conventional tensioner has
linear characteristics, however, it cannot easily cope with a wide
variation in input load.
[0007] The following is a description of the relation between the
force (thrust) of the tensioner which pushes the force transmitting
member and a displacement amplitude a of the tensioner. The
stiffness of the tensioner can be represented by the movement
(i.e., displacement amplitude .sigma.) of the second shaft member
relative to the load received from the force transmitting member.
Although a tensioner with great thrust and high stiffness can
resist a heavy input load, its displacement amplitude .sigma. is
small. If the thrust of the tensioner is made smaller, in contrast
with this, a heavy input load cannot be coped with, although the
displacement amplitude .sigma. can be made greater. The
displacement amplitude .sigma. becomes smaller if the stiffness of
the tensioner for a large engine displacement is enhanced. Thus, a
high-stiffness tensioner must inevitably be designed to function
within a narrow range of displacement amplitude .sigma., that is,
the degree of freedom of the tensioner design is low.
[0008] The object of the present invention is to provide a
tensioner capable of coping with a large variation of amplitude
despite its high stiffness, thereby dealing with a wide range of
input loads.
BRIEF SUMMARY OF THE INVENTION
[0009] A tensioner of the present invention comprises: a first
shaft member rotatably inserted in a casing so as to be restrained
from axial movement and having a first thread portion; a second
shaft member having a second thread portion mating with the first
thread portion, axially movable with respect to the casing, and
restrained from rotation; a torsion spring for generating torque
capable of rotating the first shaft member; and torque switching
means for changing the turning torque of the first shaft member in
accordance with the rotational angle of the first shaft member.
[0010] The torque switching means can use a torque switching member
that is adapted to generate a small frictional torque when the
rotational angle of the first shaft member is narrow and to
generate a large frictional torque when the rotational angle is
wide.
[0011] In the tensioner of this invention, the load applied to the
second shaft from a force transmitting member such as a belt or
chain causes the first thread portion and the second thread portion
to rotate the first shaft member. As long as the rotational angle
after the start of rotation of the first shaft member is narrow,
the torque switching member generates a small turning torque. If
the rotational angle of the first shaft member becomes wider, the
torque switching member generates a strong turning torque. Thus, a
heavy received load can be coped with, and a small amplitude
displacement can be followed satisfactorily. The force transmitting
member that is used in a large-displacement engine or the like, for
example, can cope with wide variations in the received load, and an
appropriate tension can be applied to the force transmitting
member.
[0012] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0013] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0014] FIG. 1 is a sectional view of a tensioner according to a
first embodiment of the present invention;
[0015] FIG. 2 is a sectional view of a part of an engine showing an
example of use of the tensioner shown in FIG. 1;
[0016] FIG. 3 is an exploded perspective view of a torque switching
member of the tensioner shown in FIG. 1;
[0017] FIG. 4 is a diagram showing the relation between the axial
length of the tensioner shown in FIG. 1 and torque;
[0018] FIG. 5A is a sectional view of a part of the tensioner shown
in FIG. 1;
[0019] FIG. 5B is a sectional view of a part of a tensioner
according to a second embodiment of the present invention;
[0020] FIG. 5C is a sectional view of a part of a tensioner
according to a third embodiment of the present invention;
[0021] FIG. 6A is a sectional view of a tensioner according to a
fourth embodiment of the present invention;
[0022] FIG. 6B is a sectional view of the tensioner taken along
line F6-F6 of FIG. 6A;
[0023] FIG. 7 is an enlarged view of a part of the tensioner shown
in FIG. 6A;
[0024] FIG. 8A is a sectional view of a tensioner according to a
fifth embodiment of the present invention;
[0025] FIG. 8B is a sectional view of the tensioner taken along
line F8-F8 of FIG. 8A;
[0026] FIG. 9 is an exploded perspective view of a part of a
tensioner according to a sixth embodiment of the present
invention;
[0027] FIG. 10A is a sectional view of a part of the tensioner
shown in FIG. 9;
[0028] FIG. 10B is a sectional view of a part of a tensioner
according to a seventh embodiment of the present invention;
[0029] FIG. 11 is a sectional view of a part of a tensioner
according to an eighth embodiment of the present invention;
[0030] FIG. 12 is a sectional view of a part of a tensioner
according to a ninth embodiment of the present invention;
[0031] FIG. 13 is a sectional view taken along line F13-F13 of FIG.
12;
[0032] FIG. 14 is a sectional view of a tensioner according to a
tenth embodiment of the present invention;
[0033] FIG. 15 is a diagram showing the relation between the axial
length of the tensioner shown in FIG. 14 and torque;
[0034] FIG. 16 is a sectional view of a tensioner according to an
eleventh embodiment of the present invention;
[0035] FIG. 17 is a diagram showing the relation between the axial
length of the tensioner shown in FIG. 16 and torque;
[0036] FIG. 18 is a sectional view of a tensioner according to a
twelfth embodiment of the present invention;
[0037] FIG. 19 is a diagram showing the relation between the axial
length of the tensioner shown in FIG. 18 and torque;
[0038] FIG. 20 is a sectional view of a tensioner according to a
thirteenth embodiment of the present invention;
[0039] FIG. 21 is a sectional view of a conventional tensioner;
and
[0040] FIG. 22 is a sectional view of the tensioner shown in FIG.
21 taken in the diametrical direction.
DETAILED DESCRIPTION OF THE INVENTION
[0041] A first embodiment of the present invention will now be
described with reference to FIGS. 1 to 5A. In the description of
the embodiments to follow, like numerals are used to designate
common components.
[0042] A tensioner 10 shown in FIG. 1 is used in a power
transmission mechanism 101 of an automotive engine 100 shown in
FIG. 2, for example. The power transmission mechanism 101 transmits
rotary motion of the engine 100 to a camshaft 103 by means of an
endless force transmitting member 102 such as a timing belt or
chain. The tensioner 10, which is mounted in a given position on
the engine 100, generates thrust mentioned later, thereby pushing
the force transmitting member 102 in the direction indicated by
arrow V.
[0043] The tensioner 10 comprises a hollow casing 11, a first shaft
member 12, and a second shaft member 13. Thread portions 16 and 17
of these shaft members 12 and 13 engage each other in a threaded
manner, thereby forming a shaft assembly S. The shaft assembly S is
inserted in the casing 11. The casing 11 is formed having a cavity
portion 14 that extends in the axial direction of the casing 11 and
in which the shaft assembly S is to be inserted. The front end
portion of the casing 11 has an opening, through which the second
shaft member 13 advances and retreats. A tapped hole 15 is formed
in the rear end portion of the casing 11. A bolt 15a for sealing
the interior of the casing 11 is screwed into the tapped hole
15.
[0044] The external thread portion 16 is formed on the first shaft
member 12. With respect to its axial direction, the first shaft
member 12 includes a region 12a in which the external thread
portion 16 is formed and a torque adjusting portion 12b. The second
shaft member 13 is cylindrical and has the internal thread portion
17 on its inner peripheral surface. The external thread portion 16
engages the internal thread portion 17, thereby forming the shaft
assembly S. Usually, these thread portions 16 and 17 are designed
to have a wider lead angle than conventional threads have. For
example, multiple threads such as triple threads are used for
them.
[0045] A torsion spring 18 is provided around the shaft assembly S.
The torsion spring 18 extends in the axial direction of the shaft
members 12 and 13. One end portion 18a of the torsion spring 18 is
anchored to the first shaft member 12, while the other end portion
18b is anchored to the casing 11. The rear end portion of the first
shaft member 12 is formed having a slit 19 that extends in the
axial direction of the shaft member 12. The one end portion 18a of
the torsion spring 18 is inserted in the slit 19. A bearing member
20 is fixed to the front part of the casing 11. The other end
portion 18b of the torsion spring 18 is fixed by means of the
bearing member 20. The bolt 15a is removed from the tapped hole 15,
an operating member W such as a screwdriver is inserted into the
hole 15 from the outside of the casing 11, and the distal end of
the operating member W is plugged into the slit 19. If this is
done, the first shaft member 12 can be rotated by means of the
operating member w. If the spring 18 is twisted after the first
shaft member 12 is rotated in a first direction (e.g., clockwise),
the spring 18 stores elastic energy (initial torque) that urges the
shaft member 12 to rotate in a second direction (e.g.,
counterclockwise).
[0046] The bearing member 20 is fixed to the front end portion of
the casing 11 by means of a snap ring 21. The bearing member 20 is
formed having a noncircular sliding hole 20a through which the
second shaft member 13 is passed. The diametrical cross section of
the second shaft member 13 has a noncircular shape corresponding to
the sliding hole 20a. Although the second shaft member 13 can
axially move with respect to the casing 11, therefore, it is
prevented from rotating. A cap 22 is provided on the front end of
the second shaft member 13. As shown in FIG. 2, the second shaft
member 13 directly or indirectly abuts on the force transmitting
member 102 through the cap 22.
[0047] If the shaft member 12 is rotated in the first direction by
means of the operating member W, the torsion spring 18 is twisted.
The spring 18 stores elastic energy that urges the first shaft
member 12 to rotate in the second direction. On the other hand, the
second shaft member 13 is prevented from rotating by the bearing
member 20. If the first shaft member 12 is rotated in the first
direction by means of the operating member W, therefore, the second
shaft member 13 moves in a direction such that it is drawn into the
casing 11.
[0048] When the first shaft member 12 rotates in the second
direction by means of the elastic energy stored by the spring 18,
its torque acts on the second shaft member 13. Since the rotation
of the second shaft member 13 is prevented by the bearing member
20, however, the second shaft member 13 is subjected to thrust in a
direction such that it projects from the casing 11. On the other
hand, a load Z that is delivered from the force transmitting member
102 to the second shaft member 13 acts in a direction such that the
second shaft member 13 is pushed back into the casing 11.
Accordingly, torque is generated such that the first shaft member
12 is rotated in the first direction. Forces that resist this
torque include frictional torque generated between the first shaft
member 12 and the casing 11, the repulsive force of the torsion
spring 18, etc. As the second shaft member 13 moves to a position
where those resisting forces balance with the aforesaid input load,
a moderate tension can be applied to the force transmitting member
102.
[0049] The tensioner 10 of this embodiment is provided with a
torque switching member 30 between the casing 11 and the first
shaft member 12. As shown in FIG. 3, the torque switching member 30
includes a first shaft receiving member 31 and a second shaft
receiving member 32. In this specification, the shaft receiving
member sometimes may be referred to simply as "receiving member."
The torque adjusting portion 12b of the first shaft member 12 is
provided with an end member 33. An end portion of the torque
adjusting portion 12b is inserted in the end member 33. The shaft
member 12 and the end member 33 are fixed to each other by means of
a pin 34. The end member 33, which rotates integrally with the
shaft member 12, constitutes a part of the first shaft member 12.
The end member 33 is formed having a projection 35 that projects
toward the first shaft receiving member 31. The end member 33 may
be formed integrally with the first shaft member 12 on an end
portion of the shaft member 12.
[0050] The first receiving member 31 is in the form of a cylinder
having given inside and outside diameters and includes a bottom
portion 31b. As shown in FIG. 5A, the end portion of the first
shaft member 12 is rotatably inserted in the first receiving member
31. An end face 12f of the first shaft member 12 rotates in contact
with the bottom portion 31b of the first receiving member 31 with a
contact diameter D1. The first receiving member 31 is formed having
a recess 36 that receives the projection 35 of the end member 33.
The recess 36 has a given length with respect to the
circumferential direction of the receiving member 31. The
projection 35 can move (rotate) in the circumferential direction of
the receiving member 31 within the range of the circumference
length of the recess 36. When the projection 35 moves in the recess
36, the first shaft member 12 and the receiving member 31 never
rotate integrally with each other. In other words, the first shaft
member 12 can race with respect to the first receiving member 31
within the angular range indicated by E in FIG. 3.
[0051] If the projection 35 moves within the range of E in the
circumferential direction of the recess 36, the projection 35 abuts
against an inner surface 36a or 36b of the recess 36 in the
circumferential direction. When the projection 35 abuts against the
inner surface 36a or 36b, the first shaft member 12 rotates
integrally with the receiving member 31.
[0052] The second receiving member 32 is fixed to the casing 11 in
a manner such that it is press-fitted into a circular hollow 37 in
the casing 11. The receiving member 32 is in the form of a cylinder
having given inside and outside diameters and includes a bottom
portion 32b. The first receiving member 31 is rotatably inserted in
the second receiving member 32. As shown in FIG. 5A, the bottom
portion 31b of the first receiving member 31 and the bottom portion
32b of the second receiving member 32 touch each other
substantially throughout the surface. These receiving members 31
and 32 can relatively rotate in a manner such that they are in
contact with each other with a contact diameter D2.
[0053] The first shaft member 12 is supported in the hollow 37 of
the casing 11 by means of the first and second receiving members 31
and 32 that mate with each other. Accordingly, the first shaft
member 12 can smoothly rotate without unexpected movement. The
receiving members 31 and 32 are formed having connecting holes 31a
and 32a, respectively, in positions corresponding to the slit 19.
In applying the aforesaid initial torque to the torsion spring 18,
the distal end of the operating member W (shown in FIG. 1) can be
fitted into the slit 19 through the connecting holes 31a and 32a.
Depending on the material of the casing 11, the end portion of the
first shaft member 12 may be inserted directly into the circular
hollow 37 in the casing 11 without using the second receiving
member 32. This particular feature is applicable to all the
following embodiments.
[0054] The first shaft member 12 can rotate in both the first and
second directions with respect to the first receiving member 31.
Thus, the projection 35 moves between the inner side surface 36a or
36b of the recess 36 as long as the shaft member 12 rotates within
the aforesaid range of E with respect to the first receiving member
31. In this case, only the shaft member 12 rotates with the second
receiving member 32 and the first receiving member 31 kept stopped.
Thus, the end face 12f of the first shaft member 12 rotates in
contact with the bottom portion 31b of the first receiving member
31 with the contact diameter D1. Accordingly, a relatively small
frictional torque corresponding to the contact diameter D1 is
generated.
[0055] If the first shaft member 12 rotates further, the projection
35 engages the inner side surface 36a or 36b of the recess 36.
Based on this engagement, the first receiving member 31 rotates
integrally with the shaft member 12. Thus, the bottom portion 31b
of the first receiving member 31 rotates in contact with the bottom
portion 32b of the second receiving member 32 with the contact
diameter D2. Accordingly, a relatively strong frictional torque
corresponding to the contact diameter D2 is generated.
[0056] FIG. 4 shows the relation between turning torque that is
generated when the second shaft member 13 is subjected to the input
load and the axial length of the tensioner 10 of the first
embodiment. When the first shaft member 12 starts to rotate under
the input load, the projection 35 moves in the recess 36 in the
initial stage of the rotation. As this is done, the shaft member 12
rotates with the contact diameter D1 with respect to the first
receiving member 31, so that a relatively small frictional
resistance is generated. If the shaft member 12 rotates in the
first direction, the repulsive force of the torsion spring 18
increases. However, the repulsive force is small as long as the
torsion of the torsion spring 18 is small. Accordingly, the shaft
member 12 rotates with a relatively small torque Tl, thereby
applying a small push force V to the force transmitting member
102.
[0057] If the input load from the force transmitting member 102
increases so that the second shaft member 13 is further pushed back
into the casing 11, the projection 35 abuts against the inner side
surface 36a of the recess 36. Thereupon, the first shaft member 12
and the first receiving member 31 start to rotate in a body. In
this case, the friction diameter changes into D2, the frictional
torque increases, and the repulsive force of the torsion spring 18
also increases. Thus, the shaft member 12 starts to rotate with a
strong turning torque T2 at a point P1, as shown in FIG. 4, thereby
applying a relatively strong push force V to the force transmitting
member 102.
[0058] When the received load decreases, as when the received load
increases, the shaft member 12 rotates with the friction diameter
D1 to generate a small turning torque as long as the rotational
angle of the shaft member 12 is narrow. If the rotational angle of
the shaft member 12 becomes wider, the projection 35 abuts against
the inner side surface 36b of the recess 36, whereupon the shaft
member 12 and the receiving member 31 rotate with the friction
diameter D2. Thus, a strong turning torque is generated.
[0059] According to this first embodiment, the stiffness of the
tensioner against a heavy received load can be improved without
failing to secure a relatively great amplitude displacement by
switching the contact diameter for the rotation of the first shaft
member 12 between D1 and D2 according to the rotational angle.
Accordingly, this tensioner can cope with input loads ranging from
light ones to heavy ones. If the load applied to the tensioner 10
from the force transmitting member 102 in an engine or the like,
for example, is light, therefore, the second shaft member 13 can
satisfactorily follow a small amplitude displacement, so that the
tension of the force transmitting member 102 can be kept at an
appropriate value.
[0060] FIG. 5B shows a second embodiment of this invention. In this
embodiment, a first receiving member 31 is formed having a taper
surface 38 of which the thickness increases toward its center.
Thus, a contact diameter D1 for contact between a first shaft
member 12 and the first receiving member 31 is made further smaller
than the aforesaid contact diameter D1 according to the first
embodiment.
[0061] FIG. 5C shows a third embodiment of this invention. In this
embodiment, a recess 49 is formed in the central portion of the
lower surface of a first receiving member 31. Thus, the first
receiving member 31 touches a second receiving member 32 with a
contact diameter D2 in an annular end face around the recess 49. By
doing this, the contact diameter D2 can be kept fixed even if the
receiving member 31 is worn to a certain degree. Although both
FIGS. 5B and 5C show only those portions which are needed in
explaining the contact diameters D1 and D2, other portions are
constructed in the same manner as in the first embodiment.
[0062] FIGS. 6A to 7 show a fourth embodiment of this invention.
One end portion 18a of a torsion spring 18 of this embodiment
extends in the diametrical direction of a first receiving member
31, and penetrates a recess 36 of the first receiving member 31. In
this case, the one end portion 18a of the spring 18 can move in
some measure in the recess 36 with respect to the circumferential
direction of first receiving member 31. In this allowable range for
the movement, the first receiving member 31 is stationary even
though a first shaft member 12 rotates. If the rotational angle of
the shaft member 12 becomes wider, the one end portion 18a of the
spring 18 engages an inner side surface 36a or 36b of the recess
36, thereby causing the first receiving member 31 to rotate
integrally with the shaft member 12. Since the one end portion 18a
of the spring 18 of this embodiment fulfills the same function with
the end member 33 of the first embodiment, the number of components
of the tensioner 10 can be reduced.
[0063] FIGS. 8A and 8B show a fifth embodiment of this invention.
In this embodiment, one end portion 18a of a spring 18 and an
anchor piece 39 are inserted in a slit 19. The anchor piece 39
extends in the diametrical direction of a first receiving member
31, and both end portions 39a of the anchor piece 39 are situated
inside a recess 36 of the first receiving member 31. The first
receiving member 31 never rotates in the allowable range for the
movement of the end portion 39a of the anchor piece 39 in the
recess 36 when the first shaft member 12 rotates. If the rotational
angle of the shaft member 12 becomes wider, the end portion 39a of
the anchor piece 39 abuts against an inner side surface 36a or 36b
of the recess 36, whereupon the first receiving member 31 rotates
with the shaft member 12. Thus, the anchor piece 39 fulfills the
same function with the end member 33 of the first embodiment. In
these fourth and fifth embodiments also, the turning torque can be
changed by switching the rotational contact diameter of an end face
12f of the first shaft member 12 between D1 and D2.
[0064] FIGS. 9 and 10A show a sixth embodiment of this invention.
In the case of this embodiment, a second receiving member 32 is
formed having a pair of recesses 40. Projections 41 are formed on a
first receiving member 31. The projections 41, which are situated
inside the recesses 40, can move within the range of the length of
the recesses 40 with respect to the circumferential direction of
the second receiving member 32. As shown in FIG. 10A, the bottom
surface of the first receiving member 31 is formed having a taper
surface 42 of which the thickness increases toward the center. By
doing this, a contact diameter D2 for contact between the first
receiving member 31 and the second receiving member 32 is made
smaller than a contact diameter D1 for contact between the first
receiving member 31 and a first shaft member 12.
[0065] In the case of this embodiment (FIGS. 9 and 10A), the first
receiving member 31 rotates with the shaft member 12 in the
allowable range for the movement of the projections 41 in the
recesses 40 when the first shaft member 12 rotates. At this point
in time, the contact diameter is D2, and a generated frictional
torque is relatively small. If the rotational angle of the shaft
member 12 becomes wider, the projections 41 abut against inner side
surfaces 40a or 40b of the recesses 40, whereupon the rotation of
the first receiving member 31 stops, so that only the shaft member
12 rotates with the large contact diameter D2. A frictional torque
generated in this case is greater than one that is obtained when
the shaft member 12 rotates with the contact diameter D2. Thus,
also in this embodiment, the turning torque of the first shaft
member 12 can be changed in two stages.
[0066] FIG. 10B shows a seventh embodiment of this invention. The
fundamental arrangement of this embodiment resembles that of the
sixth embodiment. In the seventh embodiment, however, a portion 43
that is thicker than its surrounding region is formed in the center
of a bottom portion 32b of a second receiving member 32. Thus, a
contact diameter D2 for contact between a first receiving member 31
and the second receiving member 32 is made smaller than a contact
diameter D1 for contact between the first receiving member 31 and a
first shaft member 12. In this seventh embodiment, as in the sixth
embodiment, therefore, the turning torque can be changed in two
stages.
[0067] FIG. 11 shows an eighth embodiment of this invention. The
fundamental arrangement of this embodiment resembles that of the
sixth embodiment (FIG. 10A). In the case of the eighth embodiment,
however, a taper surface 42 is formed on the bottom portion of a
first receiving member 31 so that a first contact diameter D1 and a
second contact diameter D2 are substantially equal.
[0068] In the case where D1 and D2 are equal, as in the case of
this embodiment, the properties of the surface of a contact portion
between the shaft member 12 and the receiving member 31 and the
properties of the surface of a contact portion between the
receiving members 31 and 32 are differentiated so that the
respective frictional torques of the two contact portions are
different. The turning torques T1 and T2 can be differentiated by
varying, for example, the type of plating for the two contact
portions, surface hardness, or material of the contact portions.
Thus, the value of the turning torque can be adjusted by suitably
treating or modifying the surfaces of the contact portions. This
technical idea is also applicable to the first to seventh
embodiments described above.
[0069] FIGS. 12 and 13 show a tensioner of a ninth embodiment of
this invention. The tensioner of this embodiment comprises a first
receiving member 31 in which an end member 33 is inserted for
rotation, a second receiving member 32 in which the receiving
member 31 is inserted for rotation, and a third receiving member 45
in which the second receiving member 32 is inserted for rotation.
The third receiving member 45 is fixed to the bottom surface of a
casing 11.
[0070] As shown in FIG. 13, a projection 35 formed on the end
member 33 penetrates a recess 36 formed in the first receiving
member 31. The projection 35 can move between inner side surfaces
36a and 36b of the recess 36 with respect to the circumferential
direction of the first receiving member 31. The first receiving
member 31 is formed having a projection 46 like the projection 35
of the end member 33. The second receiving member 32 is formed
having a recess 47 that is penetrated by the projection 46. The
projection 46 can move between inner side surfaces 47a and 47b of
the recess 47 with respect to the circumferential direction of the
second receiving member 32. When a shaft member 12 rotates, the
projection 35 moves in the recess 36 as long as the rotational
angle is narrow, so that the first receiving member 31 and the
second receiving member 32 are stopped. Since the contact diameter
of the shaft member 12 is then D1, the turning torque is minimal.
If the rotational angle of the shaft member 12 increases by a
certain degree, the first projection 35 first abuts against the
inner side surface 36a or 36b of the recess 36. Thereupon, the
first receiving member 31 rotates with the shaft member 12. As long
as the rotational angle of the first receiving member 31 is narrow,
the second projection 46 moves in the recess 47, so that the second
receiving member 32 never rotates. Since the contact diameter is
then D2, the turning torque is medium. If the shaft member 12
rotates further, the projection 46 abuts against the inner side
surface 47a or 47b of the recess 47. Thereupon, the second
receiving member 32 also rotates with the shaft member 12. Since
the contact diameter is then D3, the turning torque is maximal.
Thus, in the tensioner of the ninth embodiment, the turning torque
of the shaft member 12 can be changed more finely in three stages.
In this embodiment also, the type of plating for the individual
members, surface hardness, or material may be varied in order to
differentiate the respective frictional torques of the aforesaid
three contact portions.
[0071] FIG. 14 shows a tenth embodiment of this invention. A
tensioner 10 of this embodiment is provided with a connecting
spring 50 that constitutes a clutch mechanism. Further, a torsion
spring 18 is provided around a first shaft member 12. On the other
hand, the torsion spring 18 of the tensioner 10 of each of the
foregoing embodiments is provided covering the first shaft member
12 and a second shaft member 13. However, the torsion springs 18 of
any of the embodiments have the basic function of applying torque
to the first shaft member 12 in common. The repulsive force of the
torsion springs 18 described in connection with these embodiments
acts in the direction to push out the shaft member 13 from the
casing 11. Depending on the direction of the input load, however,
the repulsive force of the torsion springs 18 may be made to act in
the direction to push back the shaft member 13 into the casing
11.
[0072] The tensioner 10 of this tenth embodiment is also provided
with a tubular second receiving member 32 that is fixed in the
casing 11. The receiving member 32 has a bottom portion 32b. A
tubular first receiving member 31 having a bottom portion 31b is
rotatably inserted in the receiving member 32. An end portion of
the first shaft member 12 is rotatably inserted in the first
receiving member 31. A hole 32d is formed in the center of the
bottom portion 32b of the second receiving member 32. A protrusion
31d to be inserted into the hole 32d is formed in the center of the
bottom portion 31b of the first receiving member 31. The protrusion
31d projects into a tapped hole 15 through the hole 32d. A slit 31c
is formed in the distal end of the protrusion 31d.
[0073] One end portion 18a of the torsion spring 18 is anchored to
the first receiving member 31. The other end portion 18b of the
torsion spring 18 is anchored to the casing 11. The connecting
spring 50 is provided between the inner peripheral surface of the
torsion spring 18 and the outer peripheral surface of a torque
adjusting portion 12b of the shaft member 12. One end 50a of the
connecting spring 50 is anchored to the first receiving member 31.
The other end 50b of the connecting spring 50 is anchored to the
first shaft member 12. Torques that are generated as the torsion
spring 18 and the connecting spring 50 are twisted have the same
direction.
[0074] An operating member W such as a screwdriver is inserted into
the tensioner 10 of this tenth embodiment (FIG. 14) through the
hole 15, and the distal end of the operating member W is fitted
into the slit 31c. Then, the respective ends 18a and 50a of the
springs 18 and 50 are individually rotated for a given number of
times in a first direction by turning the operating member W. The
first shaft member 12 is connected to the first receiving member 31
by means of the connecting spring 50. If the receiving member 31 is
rotated in the first direction, therefore, the connecting spring 50
causes the first shaft member 12 to rotate in the first direction.
This rotation causes the second shaft member 13 to move in a
direction such that it is drawn into the casing 11. Simultaneously
with this rotation, the torsion spring 18 is twisted in a direction
such that it stores a repulsive force, whereupon it is given
initial torque.
[0075] If an external load to push the second shaft member 13 is
applied to the tensioner 10 of the tenth embodiment that is given
the first torque, the load is transmitted to the first shaft member
12 via thread portions 16 and 17, whereupon the first shaft member
12 rotates. As long as the received load is so light that the
connecting spring 50 is twisted only slightly, the first receiving
member 31 never rotates if the shaft member 12 rotates. In this
case, an end face 12f of the shaft member 12 rotates with a contact
diameter D1 with respect to the bottom portion 31b of the first
receiving member 31, so that a small frictional torque is
generated.
[0076] If the received load increases so that the rotational angle
of the shaft member 12 widens, the first receiving member 31 is
coupled to the shaft member 12 as the twist of the connecting
spring 50 increases. Thereupon, the receiving member 31 and the
shaft member 12 rotate. In this case, the first receiving member 31
rotates with a contact diameter D2 with respect to the second
receiving member 32, so that the turning torque increases.
[0077] FIG. 15 shows changes of the turning torque of the tensioner
10 of the tenth embodiment. When the first shaft member 12 rotates
for a narrow rotational angle (or with a light received load), a
turning torque T1 based on the contact diameter D1 is generated.
When the second shaft member 13 further moves in the axial
direction as the received load increases, the shaft member 12 and
the receiving member 31 are coupled to each other at a point P2 of
FIG. 15 by means of the connecting spring 50. In this case, a
relatively strong turning torque T2 is generated on the basis of
the contact diameter D2.
[0078] If the increased received load is reduced so that the shaft
member 12 rotates in the opposite direction, the contact diameter
changes according to the rotational angle, so that the turning
torque can be changed.
[0079] As seen from FIG. 15, the turning torque T1 in the first
stage and the turning torque T2 in the second stage are continuous
with each other, and there exists no step portion Q such as the one
shown in FIG. 4. Thus, according to this tenth embodiment, the
change of the turning torque is mediated by the elastic action of
the connecting spring 50, so that the continuity between T1 and T2
can be obtained. According to the tenth embodiment arranged in this
manner, compared with the foregoing embodiments, the fluctuation of
the turning torque can be smoothed.
[0080] FIG. 16 shows a tensioner 10 of an eleventh embodiment of
this invention. This tensioner 10 comprises a protrusion 12c formed
on a first shaft member 12 and rubber members 51 provided on the
protrusion 12c. The protrusion 12c and the rubber members 51 are
situated inside a recess 36 that is formed in a first receiving
member 31. The protrusion 12c and the recess 36 constitute a clutch
mechanism that connects the first shaft member 12 and the first
receiving member 31. A cylindrical second receiving member 32
having a bottom portion 32b is fixed to a casing 11. A cylindrical
first receiving member 31 having a bottom portion 31b is rotatably
inserted in the receiving member 32. An end portion of the first
shaft member 12 is rotatably inserted in the first receiving member
31. The protrusion 12c is formed on the peripheral surface of the
first receiving member 31. The rubber members 51 that function as
elastic members are attached individually to the opposite side
faces of the protrusion 12c. The rubber members 51 face inner side
surfaces 36a and 36b of the recess 36, individually. Further, a
torsion spring 18 is provided around the first shaft member 12 and
the first receiving member 31. One end portion 18a of the torsion
spring 18 is anchored to the first receiving member 31. The other
end portion 18b of the torsion spring 18 is anchored to the casing
11. The tensioner 10 of this eleventh embodiment, like the tenth
embodiment, is provided with a protrusion 31d having a slit 31c for
initial torque, a hole 32d, etc.
[0081] If the tensioner 10 of the eleventh embodiment is subjected
to load in the direction to push a second shaft member 13, the load
is transmitted to the first shaft member 12 via thread portions 16
and 17, whereupon the first shaft member 12 rotates. As long as the
rotational angle of the shaft member 12 is narrow, the protrusion
12c moves in the recess 36, so that the first receiving member 31
never rotates. In this case, the shaft member 12 rotates with a
contact diameter D1, so that the turning torque is relatively
small.
[0082] If the received load increases so that the rotational angle
of the shaft member 12 widens, the rubber members 51 engage the
inner side surface 36a or 36b of the recess 36. This engagement
causes the rubber members 51 to be compressed as the receiving
member 31 and the shaft member 12 are coupled to each other.
Thereupon, the receiving member 31 and the shaft member 12 rotate.
Thus, the first receiving member 31 rotates with a contact diameter
D2 with respect to the second receiving member 32. Accordingly, the
turning torque increases.
[0083] If the increased received load is reduced, the repulsive
force of the spring 18 causes the first receiving member 31 to
rotate in a second direction, and the first shaft member 12 also
rotates in the second direction. Thus, the second shaft member 13
moves in a direction such that it projects from the casing 11. In
this case, the turning torque can be also changed between a smaller
turning torque T1 for the contact diameter D1 and a greater turning
torque T2 for the contact diameter D2, depending on the rotational
angle of the shaft member 12.
[0084] FIG. 17 shows change of the turning torque of the tensioner
10 of the eleventh embodiment. As seen from FIG. 17, the turning
torque Ti in the first stage and the turning torque T2 in the
second stage are continuous with each other with P3 between them,
and moreover, the torque T1 in the first stage is represented by a
downwardly convex curved line. The characteristic of this torque T1
can be obtained as the rubber members 51 are compressed between the
protrusion 12c and the inner side surface 36a or 36b.
[0085] FIG. 18 shows a tensioner 10 of a twelfth embodiment of this
invention. The tensioner 10 of this embodiment has a protrusion 12d
and a recess 36 to be penetrated by the protrusion 12d, besides
aforementioned tenth embodiment (FIG. 14). If the rotational angle
of a first shaft member 12 is narrow, the protrusion 12d can move
between inner side surfaces 36a and 36b of the recess 36. The
protrusion 12d and the inner side surfaces 36a and 36b of the
recess 36 constitute a clutch mechanism. This clutch mechanism
regulates the angular range in which the shaft member 12 and a
receiving member 31 can rotate with respect to each other.
[0086] One end portion 18a of a torsion spring 18 is anchored to
the first receiving member 31, while the other end portion 18b is
anchored to the casing 11. One end 50a of a connecting spring 50 is
anchored to the first receiving member 31, while the other end 50b
is anchored to the first shaft member 12.
[0087] The protrusion 12d is formed on the peripheral surface of
the first shaft member 12. The recess 36 is formed in an end
portion of the first receiving member 31, covering a given length
with respect to its circumferential direction. The protrusion 12d
is situated in the recess 36. Thus, the angle at which the shaft
member 12 and the receiving member 31 can rotate relatively to each
other is regulated according to the circumferential length of the
recess 36.
[0088] If a load in the direction to push a second shaft member 13
from the outside is applied to the tensioner 10 (FIG. 18) of the
twelfth embodiment, the load is transmitted to the first shaft
member 12 via thread portions 16 and 17, whereupon the first shaft
member 12 rotates. If the received load is light, that is, if the
rotational angle of the shaft member 12 is narrow, the protrusion
12d moves in the recess 36. Accordingly, the first receiving member
31 never rotates, and only the shaft member 12 rotates. In this
case, an end face 12f of the shaft member 12 rotates with a contact
diameter D1 with respect to a bottom portion 31b of the first
receiving member 31, so that a small frictional torque is
generated.
[0089] If the received load increases so that the rotational angle
of the shaft member 12 widens, the twist of the connecting spring
50 increases, and the protrusion 12d abuts against the inner side
surface 36a of the recess 36, whereupon the receiving member 31
rotates with the shaft member 12. In this case, the first receiving
member 31 rotates with a contact diameter D2 with respect to a
second receiving member 32, so that a strong frictional torque is
generated. FIG. 19 shows change of the turning torque of the
tensioner 10 of the twelfth embodiment. The contact diameter
changes from D1 to D2 at a point P4 in FIG. 19. A step portion Q
between T1 and T2 can be reduced with use of the connecting spring
50.
[0090] FIG. 20 shows a tensioner of a thirteenth embodiment of this
invention. This tensioner has a third receiving member 60 and a
second connecting spring 61, besides aforementioned tenth
embodiment (FIG. 14). First and second receiving members 31 and 32,
torsion spring 18, and first connecting spring 50 share the same
constructions and functions with those of the tenth embodiment.
[0091] In this thirteenth embodiment, a first shaft member 12 is
rotatably inserted in the third receiving member 60. The third
receiving member 60 is rotatably inserted in the first receiving
member 31. The second connecting spring 61 is provided between the
inner peripheral surface of the connecting spring 50 and the outer
peripheral surface of the shaft member 12. One end 61a of the
second connecting spring 61 is anchored to the third receiving
member 60. The other end 61b of the second connecting spring 61 is
anchored to the first shaft member 12. The direction of the
repulsive force that is generated as the torsion spring 18 is
twisted is coincident with the direction of the repulsive force
that is generated as the connecting springs 50 and 61 are
twisted.
[0092] An operating member such as a screwdriver is inserted into
the tensioner 10 of this thirteenth embodiment (FIG. 20) through a
hole 15, and its distal end is fitted into a slit 31c. Then, the
torsion spring 18 and the connecting springs 50 and 61 are
individually rotated for a given number of times in a first
direction by turning the operating member. When the first receiving
member 31 rotates in the first direction, the twist of the
connecting springs 50 and 61 increases, so that the first shaft
member 12 rotates in the first direction. This rotation causes a
second shaft member 13 to move in a direction such that it is drawn
into the casing 11. Simultaneously with this rotation, the torsion
spring 18 is twisted in a direction such that it stores a repulsive
force, whereupon it is given initial torque.
[0093] If an external load to push the second shaft member 13 is
applied to this tensioner 10, the load is transmitted to the first
shaft member 12 via thread portions 16 and 17, whereupon the first
shaft member 12 rotates. As long as the received load is so light
that the rotational angle of the shaft member 12 is narrow, the
twist of the connecting spring 61 is so small that the third
receiving member 60 never rotates. In this case, an end face 12f of
the shaft member 12 rotates with a contact diameter D1 with respect
to a bottom portion 60b of the third receiving member 60, so that a
relatively small frictional torque is generated.
[0094] If the received load increases so that the rotational angle
of the shaft member 12 widens, the twist of the second connecting
spring 61 increases, so that the connecting spring 61 causes the
shaft member 12 and the third receiving member 60 to rotate with
each other. In this case, the third receiving member 60 rotates
with a contact diameter D2 with respect to the first receiving
member 31, so that a medium frictional torque is generated.
[0095] If the received load further increases so that the shaft
member 12 rotates further, the twist of the first connecting spring
50 increases, whereupon first receiving member 31 is also rotated
via the connecting spring 50. In this case, the first receiving
member 31 rotates with a contact diameter D3 with respect to the
second receiving member 32, so that the frictional torque is
maximal.
[0096] If the increased received load is reduced so that the
tensioner 10 is actuated in the opposite direction, the repulsive
force of the torsion spring 18 causes the first shaft member 12 to
rotate in a second direction. When the received load is reduced in
this manner, just as when the received load increases, the contact
diameter changes in three stages in accordance with the rotational
angle of the shaft member 12, so that the turning torque can be
changed gradually.
[0097] In the tensioner of this thirteenth embodiment, the turning
torque of the shaft member 12 can be changed more finely in three
stages. In this embodiment also, the type of plating for the
individual members, surface hardness, or material may be varied in
order to differentiate the respective frictional torques of the
aforesaid three contact portions. Although the turning torque is
changed in three stages in either of the ninth and thirteenth
embodiments, it may alternatively be changed in four stages or
more.
[0098] As is evident from the above description, the tensioner of
the present invention can be suitably used in a power transmission
mechanism that uses an endless belt, endless chain, etc., such as
an automotive engine, for example.
[0099] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *