Canadian Patents Database / Patent 2369327 Summary

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(12) Patent Application: (11) CA 2369327
(54) English Title: AUTOTENSIONER
(54) French Title: TENDEUR AUTOMATIQUE
(51) International Patent Classification (IPC):
  • F16H 7/12 (2006.01)
  • F16H 7/08 (2006.01)
(72) Inventors :
  • AYUKAWA, KAZUMASA (Japan)
(73) Owners :
  • UNITTA COMPANY (Japan)
(71) Applicants :
  • UNITTA COMPANY (Japan)
(74) Agent: OSLER, HOSKIN & HARCOURT LLP
(74) Associate agent:
(45) Issued:
(22) Filed Date: 2002-01-24
(41) Open to Public Inspection: 2003-01-27
Examination requested: 2006-11-03
(30) Availability of licence: N/A
(30) Language of filing: English

(30) Application Priority Data:
Application No. Country/Territory Date
P2001-227584 Japan 2001-07-27

English Abstract





An autotensioner comprises a cup-shaped stationary member,
an arm rotatably attached to an opening of the stationary member.
An axial bore is formed in the bottom of the stationary member.
A rocking wall extending to the bottom is provided at the arm.
A first friction member is provided between the rocking wall
and the inner wall of the opening. The first friction member
is gripped between the rocking wall and the inner wall. A rocking
shaft extending to the bottom is provided at the center of a
lid portion of the arm. The rocking shaft is inserted in the
axial bore. A second friction member is provided between the
rocking shaft and the axial bore. The first friction member
and the second friction member are formed of a synthetic resin
mainly comprised of PPS, exhibit high limited PV factors, and
exhibit low coefficients of friction.


Note: Claims are shown in the official language in which they were submitted.




CLAIMS

1. An autotensioner comprising:
a cup-shaped stationary member that has an opening and a
bottom, in which an axial bore is formed;
an arm that is attached to said opening, said arm having
a rocking shaft which extends to said bottom and is inserted
into said axial bore, so that said arm rocks about said rocking
shaft, said arm having a stub shaft offset from said rocking
shaft and extending in the opposite direction to said rocking
shaft;
a pulley that rotates about said stub shaft to give a tension
to a transmission belt; and
a first friction member that is provided between an annular
wall of said stationary member, which is positioned close to
said opening, and a rocking wall formed on said arm, to generate
a first frictional resistance by rocking of said arm.
2. An autotensioner according to claim 1, further comprising
a second friction member interposed between said axial bore and
said rocking shaft to generate a second frictional resistance
by rocking of said arm.
3. An autotensioner according to claim 1, wherein said first
friction member has a friction surface generating said first
frictional resistance with said rocking wall by rocking of said
arm, the area of said friction surface being set to a size in
accordance with a maximum load acting on said first friction

23




member.
4. An autotensioner according to claim 2, wherein the area
of said friction surface of said first friction member is
determined by the following formula:
A = {(a+b)/a} x F/P
wherein A is the area of said friction surface of said first
friction member, a is the distance from a first peak position
where a maximum load acts on said first friction member to a
second peak position where a maximum load acts on said second
friction member, b is the distance from said first peak position
to a third peak position where a maximum load acts on said pulley,
F is a maximum load acting on said pulley, and P is a withstand
pressure of the first friction member.
5. An autotensioner according to claim 1, wherein said first
friction member is made of a synthetic resin mainly comprised
of polyphenyl sulfone, and said synthetic resin exhibits a
limited PV factor substantially exceeding 2.0 MPa.cndot.m/sec when
sliding against said arm at a speed of substantially 0.5 m/sec.
6. An autotensioner according to claim 1, wherein said rocking
wall and said annular wall face each other and are substantially
parallel, and said first friction member has a first bearing
portion formed in a tubular shape between said rocking wall and
said annular wall.
7. An autotensioner according to claim 1, wherein said rocking
wall faces said annular wall at a slant, and said first friction

24




member has a second bearing portion formed in a taper between
said rocking wall and said annular wall.
8. An autotensioner according to claim 1, wherein a
normal-rotation damping force, acting on said arm when said arm
moves in a first direction in which said transmission belt slacks,
is greater than a reverse-rotation damping force, acting on said
arm when said arm moves in a second direction in which said
transmission belt is tensioned.
9. An autotensioner according to claim 1, wherein a dynamic
damping force acting on said arm is greater than a static damping
force acting on said arm.
10. An autotensioner according to claim 9, wherein said dynamic
damping force is more than two times said static damping force.

25

Note: Descriptions are shown in the official language in which they were submitted.

t -- W
CA 02369327 2002-03-20
AUTOTENSIONER
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an autotensioner used in
a belt system for transmitting drive power of, for example, an
automobile engine to a driven pulley by a transmission belt.
2. Description of the Related Art
Conventionally, there is known an autotensioner, which is
to provided in a driven apparatus for transmitting drive power of
an automobile engine to a plurality o~ equipments through a
transmission belt, to reliably transmit the drive power to each
of the equipments by imparting tension to the transmission belt.
Such an autotensioner is provided with a stationary member so
that it can be fixed to an engine block, for example, an arm
rocking with respect to the stationary member, and a pulley
attached rotatably to the arm. A torsion coil spring, for example,
is housed in the stationary member so as to give tension to the
transmission belt through the pulley.
2o In such an autotensioner, when the transmission belt
vibrates, the arm rocks and a load acts between the arm and
stationary member. To counter this load and attenuate the
vibration of the belt and to prevent damage caused by contact
between the arm and the stationary member, a friction member
formed from a synthetic resin, for example, is fixed to the arm,
1

i
CA 02369327 2002-03-20
and slides against the stationary member when the arm rocks."
For the engagement of the friction member, it is known to use
a C-spring biasing the friction member from the inside thereof
by a substantially constant pressure. For example, this
configuration is disclosed in Japanese Unexamined Patent
Publication (Kokai) No. 8-338487.
However, a C-spring has to be set in material and shape
in accordance with the required pressure. Further, it is
necessary to provide a structure for engaging the C-spring with
1o the friction member. Thus, when using a C-spring, there are
the problems of a complicated configuration and increased
manufacturing cost.
SUI~IARY OF THE INVENTION
Therefore, an object of the present invention is to provide
an autotensioner in which a friction member is fixed by a simple
structure without using a C-spring to generate the required
damping force.
According to the present invention, there is provided a
cup-shaped stationary member, an arm, a pulley, and a first
friction member.
The cup-shaped stationary member has an opening and a bottom,
in which an axial bore is formed. The arm is attached to the
opening. The arm has a rocking shaft, which extends to the bottom
and is inserted into the axial bore, so that the arm rocks about
the rocking shaft. The arm has a stub shaft offset from the
2

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CA 02369327 2002-03-20
rocking shaft and extending in the opposite direction to the
rocking shaft. The pulley rotates about the stub shaft and gives
a tension to a transmission belt. The first friction member
is provided between an annular wall of the stationary member,
s which is positioned close to the opening, and a rocking wall
formed on the arm, to generate a first frictional resistance
by rocking of the arm.
By the simple structure in which the friction member is
gripped between the circumferential wall and the rocking wall,
1o a damping force is generated:
The autotensioner may be provided with a second friction
member interposed between the axial bore and the rocking shaft
to generate a second frictional resistance by rocking of the
arm. By providing this second friction member, along with the
15 first friction member, the rocking of the arm is attenuated.
Preferably, the first friction member has a friction surface
generating the first frictional resistance with the rocking wall
by rocking of the arm, and the area of the friction surface is
set to a size in accordance with a maximum load acting on the
2o first friction member.
The area of the friction surface of the first friction member
may be determined by the following formula:
A = {{a+b)/a~ x F/P
wherein A is the area of the friction surface of the first friction
2s member, a is the distance from a first peak position where a
3

CA 02369327 2002-03-20
maximum load acts on the second friction member to a second peak
position where a maximum load acts on the first friction member,
b is the distance from the second peak position to a third peak
position where a maximum load acts on the pulley, F is a maximum
s load acting on the pulley, and P is a withstand pressure of the
first friction member.
Preferably, the first friction member is made of a synthetic
resin mainly comprised of polyphenyl sulfone, and the synthetic
resin exhibits a limited PV factor substantially exceeding 2.0
to MPa-m/sec when sliding against the arm at a speed of substantially
0.5 m/sec. By making the first friction member of a material
with a high limited PV factor, a sufficient durability can be
exhibited against rocking of the arm.
The rocking wall and the annular wall may face each other
i5 and be substantially parallel, and the first friction member
may have a bearing portion formed in a tubular shape between
the rocking wall and the annular wall. Such a first friction
member is easy to form.
The rocking wall may face the annular wall at a slant, and
2o the first friction member may have a bearing portion formed in
a taper between the rocking wall and the annular wall. Such
a first friction member can exhibit a high durability with respect
to the radial load by adjusting the thickness of the shaft member
in accordance with the distribution of the load acting on the
2s bearing portion.
4

CA 02369327 2002-03-20
Preferably, a normal-rotation damping force, acting on the
arm when the arm moves in a first direction in which the
transmission belt slacks, is greater than a reverse-rotation
damping force, acting on the arm when the arm moves in a second
s direction in which the transmission belt is tensioned.
Further, preferably, a dynamic damping force acting on the
arm is greater than a static damping force acting on the arm.
In this case, the dynamic damping force is more than two times
the static damping force.
1o BRIEF DESCRIPTION OF THE DRAWINGS
The objects and advantages of the present invention will
be better understood from the following description, with
reference to the accompanying drawings in which:
Fig. 1 is a view of a belt system of an automobile engine
15 to which an autotensioner of a first embodiment is provided;
Fig. 2 is a view of the outside appearance of an
autotensioner of the first embodiment;
Fig. 3 is a sectional view of an autotensioner of the first
embodiment;
2o Fig. 4 is a graph for explaining a limited PV factor of
a first friction member;
Fig. 5 is a sectional view of a tensioner manufactured for
detecting the damping characteristics of the autotensioner of
the first embodiment;
2s Fig. 6 is a view showing a static hysteresis of a damping

CA 02369327 2002-03-20
force of an autotensioner of the first embodiment;
Fig. 7 is a view showing a dynamic hysteresis of a damping
force of an autotensioner of the first embodiment;
Fig. 8 is a view showing a result of detecting a change
of a normal-rotation damping force and a reverse-rotation damping
force relative to a rocking frequency of an arm;
Fig. 9 is a view showing the result indicated in Fig. 8
as a graph;
Fig. 10 is a sectional view of an autotensioner of a second
embodiment; and
Fig. 11 is a sectional view of an autotensioner of a third
embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described below with reference
is to embodiments shown in the drawings.
Fig. 1 is a view of a belt system of an automobile engine
to which an autotensioner of a first embodiment is provided,
while Fig. 2 is a view of the outer appearance of the
autotensioner.
2o An autotensioner 10 is mounted in the belt system shown
in Fig. 1. The belt system is provided with a drive pulley 11
attached to an output shaft of the engine, an air-conditioner
pulley 12, a power steering system pulley 13, an alternator pulley
14, idler pulleys 15 and 16, and the autotensioner or tensioner
25 10. An endless transmission belt 17 is wrapped around the pulleys.
6

CA 02369327 2002-03-20
Rotational drive force of the drive pulley 11 is transmitted
to the other pulleys by the transmission belt 17. The
transmission belt 17 is driven in the clockwise direction in
the drawing. The tensioner 10 biases the transmission belt 17
from the outside to impart tension to the transmission belt 17.
As shown in Fig. 2, the tensioner 10 has a cup-shaped
stationary member 20, which is fixed to the engine block (not
shown) . An arm 30 is swingably or rockably attached to the
stationary member 20, while a pulley 40 is rotatably supported
to by the arm 30. As shown in Fig. 1, a transmission belt 17 is
wrapped around the outer circumference of the pulley 40, and
the pulley 40 rotates along with the rotation of the transmission
belt 17. A torsion coil spring (not shown) is housed in the
stationary member 20, so that the pulley 40 is biased in a
direction imparting tension to the transmission belt 17 by this
biasing force. The arm 30 rocks or moves in an I direction in
which the transmission belt 17 slacks, and in a J direction in
which the transmission belt 17 tensions.
Fig. 3 shows a cross-section of the tensioner 10. The
2o stationary member 20 has a mounting portion 21 and a cup 22,
which has an opening 26 and a bottom 27. The mounting portion
21 has mounting holes 211 for fixing the stationary member 20
to the engine block.
The cup 22 is provided with a bearing engagement portion
222 extending from the center of the bottom 27 toward the opening
7

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CA 02369327 2002-03-20
26. The bearing engagement portion 222 has an axial bore 223.
The arm 30 is attached to the opening 26, and can rock about
the axis of the cup 22, or the axis of a rocking shaft 311 and
rocking wall 312, which are described later. The arm 30 has
s a lid portion 310, the rocking shaft 311, and a stub shaft 320.
The lid portion 310 is rotatably supported by the opening 26
through a first friction member 50 described later. The rocking
shaft 311 extends toward the bottom 27, and the stub shaft 320
offsets from the rocking shaft 311, and extends in the opposite
1o direction to the rocking shaft 311.
Two tubular portions extending toward the bottom 27 are
formed on the lid portion 310. The tubular portions are the
rocking shaft 311 and the rocking wall 312, and the rocking wall
312 has a larger diameter than the rocking shaft 311.
1s The rocking wall 312 is inserted in the opening 26 to face
an annular inner wall 224 of the stationary member 20, which
is positioned close to the opening 26, substantially in parallel .
The first friction member 50 is provided between the inner wall
224 and the rocking wall 312. The first friction member 50 has
2o a bearing 510, and a flange 520 projecting in a horizontal
direction from the outer surface of the bearing 510. The bearing
510 extends along the rocking wall 312 and the inner wall 224,
and exhibits a tubular shape. The bearing 510 acts as a bearing
for the radial load. The bearing 510 is gripped between the
2s inner wall 224 and the rocking wall 312. When the arm 30 rocks,
8

CA 02369327 2002-03-20
frictional resistance is caused between the rocking wall 312
and the bearing 510. The flange 520 acts as a thrust bearing
for causing smooth rocking of the arm 30.
The rocking shaft 311 becomes smaller in outside diameter
the further toward the bottom 27. The outside diameter of its
tip is smaller than the inside diameter of the axial bore 223.
A female thread is formed in the inner wall surface of the tip
of the rocking shaft 311.
The rocking shaft 311 is inserted in the axial bore 223.
to A tubular second friction member 60 is provided between the
rocking shaft 311 and the axial bore 223,. The second friction
member 60 exhibits a tapered shape becoming smaller in diameter
toward the opening 26. The second friction member 60 has a bearing
61 acting as a bearing of the radial load, and a flange 62 formed
i5 along a bottom surface 221 of the cup 22. When the rocking shaft
311 rocks about the axis, frictional resistance is caused between
the bearing 61 and the rocking shaft 311. The movement of the
rocking shaft 311 in the axial direction is limited by the flange
62 .
2o A disk 24 having substantially the same diameter as the
flange 62 is provided at the bottom surface of the second friction
member 60. An engagement bolt 23 is screwed into the tip of
the rocking shaft 311 via the disk 24.
A torsion coil spring 25 is housed in the space defined
25 by the lid portion 310 and the cup 22. The torsion coil spring
9

CA 02369327 2002-03-20
25 is formed by winding a metal material having a predetermined
coil length in a spiral. One end of the torsion coil spring
25 is engaged with the lid portion 310, while the other end is
engaged with the bottom surface 221. The torsion coil spring
s 25 always biases the arm 30 in the I direction (see Fig. 1).
In the arm 30, a columnar hole 321 is formed in the stub
shaft 320. A female thread is formed on the inner wall of the
columnar hole 321. A pulley 40 is rotatably attached to the
stub shaft 320 through a ball bearing 42. A pulley bolt 41 is
to screwed into the columnar hole 321, so that the pulley 40 is
fixed to the stub shaft 320. A dust shield 43 is provided between
the pulley bolt 41 and the ball bearing 42.
When the arm 30 rocks, the first friction member 50 and
the second friction member 60 slide between the stationary member
15 20 and the arm 30. Namely, the first friction member 50 slides
between the inner wall 224 and the rocking wall 312, and the
second friction member 60 slides between the axial bore 223 and
the rocking shaft 311. Namely, the tensioner 10 is supported
by the first friction member 50 and the second friction member
20 60 with respect to rocking of the arm 30. The first friction
member 50 and the second friction member 60 have to be formed
to exhibit sufficient durability against sliding with the arm
30. An explanation will be given of the first friction member
50 and the second friction member 60.
25 The first friction member 50 is formed using a synthetic

CA 02369327 2002-03-20
resin, which is mainly comprised of polyphenyl sulfone (PPS),
and contains partial aromatic nylon (PA-6T) shown in Japanese
Patent No. 2972561, and polyether sulfone (PES) shown in Japanese
Patent No. 2951321, etc.
s Fig. 4 is a graph of the limited PV factors of bearing members
J1 and J2 formed from conventionally known materials, and the
first friction member 50 formed by the synthetic resin G. Note
that, in the drawing, the abscissa shows the speed (m/sec) under
usage conditions, while the ordinate shows the PV factor
1o (MPa~m/sec) .
The bearing member J1 is made of PA-6T, while the bearing
member J2 is made of PES. As understood from Fig. 4, when the
arm 30 (see Fig. 3) slides with respect to the bearing members
J1 and J2 by a speed of substantially 0.5 m/sec, the limited
i5 PV factor of J1 is approximately 1.6 MPa~m/sec, while the limited
PV factor of J2 is approximately 2.0 MPa-m/sec. Conversely,
when the arm 30 slides against the first friction member 50 under
the same conditions, the first friction member 50 exhibits a
limited PV factor of approximately 4.0 MPa~m/sec. Thus, the
2o first friction member 50 made of the synthetic resin G has a
limited PV factor of about twice that of the bearing members
J1 and J2, and therefore has a relatively high limited PV factor.
The first friction member 50 is pressed by the rocking wall
312 by a load acting in a constant direction from the transmission
25 belt 17 (see Fig. 1). Further, the first friction member 50
11

i
CA 02369327 2002-03-20
slides against the rocking wall 312 because of the rocking of
the arm 30. If the tensioner 10 is used over a long period,
the first friction member 50 becomes worn due to this pressing
and sliding, and a problem may arise, in which the arm 30 is
s tilted. Conversely, in the embodiment, by making the first
friction member 50 of the synthetic resin G with a high limited
PV factor and a small wear factor, the durability is improved.
Similarly, the second friction member 60 is also made of a
material with a small wear factor.
1o Note that the wear factor k is defined according to the
following formula: ,
Ow = k-p-v-t
wherein ~w is the amount of wear of the friction member, p is
a pressure acting on the friction member, v is a relative speed
1s of the friction member to the arm 30, and t is amount of time
the friction member slides with the arm 30.
Since the first friction member 50 is subject to a relatively
strong load as compared with the second friction member 60, the
first friction member 50 is made of a material with a high limited
2o PV factor, i . a . , a material with a high withstand pressure value
so as to exhibit the good durability. The loads acting on the
first friction member 50 and the second friction member 60 can
be calculated as described later. Note that a first peak position
at which a maximum load occurs in the longitudinal direction
2s of the first friction member 50 is designated as D1, a second
12

CA 02369327 2002-03-20
peak position at which a maximum load occurs in the longitudinal
direction of the second friction member 60 is designated as D2,
and a third peak position at which a maximum load occurs in the
pulley 40 at the pulley outer surface 411 where the transmission
s belt 17 runs is designated as K.
When the transmission belt 17 vibrates, a load acts on the
pulley's outer surface 411 in a constant direction. The maximum
load acting on the third peak position K at this time is designated
as F. When the distance from the second peak position D2 to
1o the first peak position D1 is a, and the distance from the first
peak position D1 to the third peak position K is b, the load
fa acting on the first peak position D1 is expressed by the formula
(1)
fa = ~ (a+b) /a) x F (1)
1s Similarly, the load fb acting on the second peak position
D2 is expressed by the formula (2):
fb = (b/a) x F (2)
As can be understood from the formulas (1) and (2), the
smaller the distance a, the greater the load fa acting on the
2o first friction member 50 and the load fb acting on the second
friction member 60. Namely, by extending a friction surface
51 of the first friction member 50 to the bottom 27 to position
the first peak position Dl at the bottom 27 side (D'1 in Fig.
3), as shown by the broken line H in Fig. 3, it is possible to
2s increase the loads fa and fb. If the loads fa and fb are increased,
13

CA 02369327 2002-03-20
the frictional resistances occurring at the first friction member
50 and the second friction member 60 also increase, and it is
possible to increase the damping force of the tensioner 10.
At this time, the first friction member 50 and the second friction
s member 60 have to be formed so as to sufficiently withstand the
loads fa and fb acting at the peak positions D1 and D2.
The area A required for the member forming the first friction
member 50 to withstand the load fa is expressed by the formula
(3), when the value including a margin required for securing
1o safety with respect to the pressure value to be withstood
(withstand pressure value) is P.
A = fa/P (3)
As can be understood from the formula (3), the larger the
withstand pressure value P, the smaller the area required for
15 the friction surface 51. In the embodiment, since the first
friction member 50 is made of a material having a high withstand
pressure value P, the required area A may be made relatively
small. Further, according to the formula (3), the larger the
load fa, the larger the area A has to be made. Therefore, when
2o extending the first friction member 50 and moving the first peak
position D1 to the bottom 27 side (i.e., D'1) to increase the
load fa, it is possible to improve the durability of the first
friction member 50 by making the area A large.
After entering the formula (1) into the formula (3) , the
25 area A of the friction surface 51 is expressed by the formula
14

CA 02369327 2002-03-20
(Q)
A = ((a+b)/a} x F/P (4)
Similarly, the area 8 of the friction surface of the second
friction member 60 is expressed by the formula (5):
B = (b/a) x F/P
(5)
As described above, by extending the friction surface 51
of the first friction member 50 in the direction of the bottom
27, the load fa acting on the first friction member 50 and the
load fb acting on the second friction member 60 are increased.
to Further, by forming the first friction member 50 and the second
friction member 60 so as to withstand these loads, the frictional
resistance occurring due to the rocking of the arm 30 becomes
greater.
The damping force of the tensioner 10 is calculated from
the total of the frictional forces occurring in the first friction
member 50 and the second friction member 60. That is, the damping
force DF of the tensioner 10 is expressed by the formula (6).
Here, p1 is the coefficient of friction of the material forming
the first friction member 50, while u2 is the coefficient of
2o friction of the material forming the second friction member 60.
DF = u1 x fa + ~2 x fb (6)
Therefore, by increasing the loads fa and fb acting on the
first friction member 50 and the second friction member 60, the
tensioner 10 generates a large damping force. Thus, by adjusting
the loads fa and fb acting on the first friction member 50 and

CA 02369327 2002-03-20
the second friction member 60, the damping force of the tensioner w
can be adjusted. Note that it is of course also possible
to adjust the damping force of the tensioner IO by adjusting
the coefficients of friction u1 and p2 of the first friction
s member 50 and the second friction member 60. For example, it
is possible to change the coefficient of friction by blending
in PTFE or another material into the synthetic resin G comprised
mainly of PPS.
Next, experiment results regarding the damping force of
io the tensioner 10 will be described below.
A tensioner 70 shown in Fig. 5 is manufactured for detecting
the damping performance of the tensioner 10 of the embodiment.
The structure of the tensioner 70 is different from the tensioner
10 in that a ball bearing 71 is provided instead of the first
friction member 50 (see Fig. 3) , and a ball bearing 72 is provided
instead of the second friction member 60 (se Fig. 3) . The other
parts of the tensioner 70 are the same as those of the tensioner
10.
Fig. 6 shows a static hysteresis of a damping force of the
2o tensioner 10. Solid lines L1 and L2 relate to the tensioner
10. The solid line L1 indicates a load acting on the arm 30
when the arm 30 moves or rocks in the normal direction, i.e.,
in the J direction (see Fig. 1) , and the solid line L2 indicates
a load acting on the arm 30 when the arm 30 moves in the reverse
direction, i.e., in the I direction (see Fig. 1). A solid line
16

CA 02369327 2002-03-20
L3 relates to the tensioner 70, and indicates a load acting on
the arm 30 when the arm 30 moves in the normal or reverse direction.
The rocking frequency of the arm 30 is 0.02 Hz.
As understood from Fig. 6, when the arm 30 moves in the
s normal direction, the load linearly increases, and when the arm
30 moves in the reveres direction, the load linearly decreases.
In the tensioner 70 using the ball bearings 71 and 72, since
a frictional force does not substantially act on the arm 30,
the damping force acting on the arm 30 is constant regardless
of the moving directions of the arm 30 (see the solid line L3).
Conversely, in the tensioner 10 of the embodiment, due to the
first and second friction members 50 and 60, the normal-rotation
load (the solid line Ll) is greater than the reverse-rotation
load (the solid line L2), and the absolute value of the
1s normal-rotation damping force (S1) is greater than the absolute
value of the reverse-rotation damping force (S2). Namely, the
static hysteresis of the tensioner 10 is non-bisectional.
Fig. 7 shows a dynamic hysteresis of a damping force of
the tensioners. Solid line L4 indicates the dynamic
2o characteristics of the tensioner 10 of the embodiment. Namely,
the solid line L4 indicates a relationship between the angular
position of the arm 30 and the load acting on the arm 30 when
the arm 30 rocks . On the other hand, the solid line L5 indicates
dynamic characteristics of the tensioner 70 using the ball
2s bearings 71 and 72. Note that the rocking frequency of the arm
17
the second friction membe

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CA 02369327 2002-03-20
30 is 20 Hz.
As understood from Fig. 7, in the tensioner 70 using the
ball bearings 71 and 72, since a frictional force does not
substantially act on the arm 30, the damping force acting on
the arm 30 is constant regardless of the moving directions of
the arm 30 (see the solid line L5) . Conversely, in the tensioner
of the embodiment, the normal-rotation load is greater than
the reverse-rotation load and a hysteresis exists as described
above . Namely, the absolute value of the normal-rotation damping
to force (S3) , which is the difference between the normal-rotation
load and the load acting on the tensioner 70, is greater than
the absolute value of the reverse-rotation damping force (S4),
which is the difference between the reverse-rotation load and
the load acting on the tensioner 70. Thus, the dynamic hysteresis
of the tensioner 10 is non-bisectional similarly to the static
hysteresis.
Fig. 8 shows a result of detecting a change of a
normal-rotation damping force and a reverse-rotation damping
farce relative to a rocking frequency of the arm 30, and Fig.
9 is a graph in which the results shown in Fig. 8 are indicated.
As understood from the drawings, as the rocking speed or rocking
frequency becomes high, the damping force increases from a state
in which the rocking speed is slow (i . e. , 0 . 02 Hz) , and the damping
force becomes approximately constant when the rocking frequency
is over 10 Hz. Namely, the dynamic damping force acting on the
18

CA 02369327 2002-03-20
arm 30 is greater than the static damping force acting on the w
arm 30, and when the rocking frequency is 20 Hz, fox example,
the dynamic damping force is approximately 2.3 times the static
damping force.
s In an automobile engine, the rotational frequency of an
idling condition is between 20 and 30 Hz. In the tensioner 70
of the embodiment, the dynamic damping force is little changed
when the number of rotations is changed under conditions higher
than that of the idling condition. Namely, in the tensioner
10, the velocity dependency of the damping force under usage
conditions is small, and the tension of, the transmission belt
is always kept constant even when the number of rotation of the
engine is varied.
As described above, according to the first embodiment, the
1s damping force generated by a tensioner is kept constant without
using a C-spring.
With reference to Fig. 10, a second embodiment will be
described below. Note that components that are the same as those
in the first embodiment are assigned the same reference numerals .
2o The lid portion 81 in the tensioner 80 has a rocking wall
82 extending along the direction of the bottom 27. The rocking
wall 82 faces the inner wall 224 close to the opening 26 of the
cup 22 at a slant. Namely, the distance between the rocking
wall 82 and the inner wall 224 becomes narrower the closer to
2s the bottom 27,
19

CA 02369327 2002-03-20
A first friction member 90 is provided between the rocking
wall 82 and the inner wall 224. The bearing portion 910 of the
first friction member 90 extends along the rocking wall 82 and
the inner wall 224, and exhibits a tapered shape of a narrower
width toward the bottom 27. Since the tapered bearing portion
910 has a greater thickness compared with the tubular bearing
510 (see Fig. 3) in the first embodiment, the tapered bearing
portion 910 exhibits a higher durability to the radial load acting
on the bearing portion 910. Note that the configurations of
1o the second friction member 60, the stationary member 20, the
torsion coil spring 25, and the pulley 40 are similar to those
of the first embodiment.
According to the second embodiment, it is possible to attach
the first friction member 90 to the cup 20 without using a C-spring
etc. in the same way as in the first embodiment. Further,
according to the second embodiment, it is possible to form the
bearing portion 910 having a high durability with respect to
the radial load acting on the first friction member 90.
With reference to Fig. 11, a third embodiment will be
2o described below. Note that components that are the same as those
in the first embodiment are assigned the same reference numerals .
In the tensioner 100, the mounting portion 111 of the
stationary member 110 is formed at the outer circumference of
the bottom 27. A bolt hole 113 sunk toward the opening 26 is
formed at the center of the bottom surface 112. An engagement

i
CA 02369327 2002-03-20
bolt 23 and disk 24 are provided in the bolt hole 113. The "
engagement bolt 23 screws with the tip of the rocking shaft 311
of the lid portion 30 through the disk 24. The second friction
member 60 is interposed between the axial bore 223 and the rocking
s shaft 311.
The stationary member 110 is fixed to the engine block in
the state with the bottom surface 112 and engine block (not shown)
in abutment. The engagement bolt 23 and disk 24 are provided
in the bolt hole 113, and do not interfere with the engine block.
io The configurations of the first friction member 50, the second
friction member 60, the torsion coil spring 25, the arm 30, and
the pulley 40 are similar to those of the first embodiment.
According to the third embodiment, the present invention
can be applied even when it is necessary to provide the mounting
15 portion 111 at the bottom 27 due to the form of the belt system.
Thus, according to the third embodiment, it is possible to give
the function of a tensioner without using a C-spring etc. with
a configuration including the first friction member 50.
Note that, in the first through third embodiments, the
2o materials and the shapes of the first friction member 50 and
the second friction member 60 are determined based on the above
formulas ( 1 ) to (5 ) , but other correction formulas can be used,
taking into consideration the distribution of the load acting
on the friction members 50 and 60 or the wear due to use or other
25 factors.
21

CA 02369327 2002-03-20
Although the embodiments of the present invention have been
described herein with reference to the accompanying drawings,
obviously many modifications and changes may be made by those
skilled in this art without departing from the scope of the
s invention.
The present disclosure relates to subject matter contained
in Japanese Patent Application Nos. 2001-227584 (filed on July
27, 2001) and 2001-391336 (filed on December 25, 2001) which
are expressly incorporated herein, by reference, in their
to entireties.
22

A single figure which represents the drawing illustrating the invention.

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Admin Status

Title Date
Forecasted Issue Date Unavailable
(22) Filed 2002-01-24
(41) Open to Public Inspection 2003-01-27
Examination Requested 2006-11-03
Dead Application 2011-01-24

Abandonment History

Abandonment Date Reason Reinstatement Date
2010-01-25 FAILURE TO PAY APPLICATION MAINTENANCE FEE
2010-02-15 FAILURE TO PAY FINAL FEE

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Registration of Documents $100.00 2002-01-24
Filing $300.00 2002-01-24
Maintenance Fee - Application - New Act 2 2004-01-26 $100.00 2003-12-18
Maintenance Fee - Application - New Act 3 2005-01-24 $100.00 2005-01-12
Maintenance Fee - Application - New Act 4 2006-01-24 $100.00 2005-11-10
Request for Examination $800.00 2006-11-03
Maintenance Fee - Application - New Act 5 2007-01-24 $200.00 2006-11-03
Maintenance Fee - Application - New Act 6 2008-01-24 $200.00 2008-01-23
Maintenance Fee - Application - New Act 7 2009-01-26 $200.00 2008-11-14
Current owners on record shown in alphabetical order.
Current Owners on Record
UNITTA COMPANY
Past owners on record shown in alphabetical order.
Past Owners on Record
AYUKAWA, KAZUMASA
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Abstract 2002-03-20 1 25
Description 2002-03-20 22 808
Drawings 2002-03-20 10 201
Representative Drawing 2002-06-03 1 6
Cover Page 2003-01-02 1 36
Abstract 2002-01-24 1 26
Description 2002-01-24 22 862
Claims 2002-01-24 3 102
Description 2009-07-03 22 800
Claims 2009-07-03 3 90
Representative Drawing 2009-08-06 1 27
Correspondence 2002-02-26 1 17
Assignment 2002-01-24 3 156
Correspondence 2002-03-20 37 1,161
Prosecution-Amendment 2007-01-08 2 63
Fees 2003-12-18 1 40
Fees 2005-01-12 1 42
Fees 2005-11-10 1 41
Prosecution-Amendment 2006-11-03 1 45
Fees 2006-11-03 1 47
Fees 2008-01-23 1 49
Prosecution-Amendment 2009-01-12 2 48
Fees 2008-11-14 1 45
Prosecution-Amendment 2009-07-03 7 176