Note: Descriptions are shown in the official language in which they were submitted.
PULLEY. BALL BEARING AND BELT TRANSMITTING DEVICE
BACKGROUND OF THE INVENTION
This invention generally relates to a pulley and a
ball bearing for a pulley. In particular, the invention
relates to a hall bearing for use i.ri a timing belt of an
engine of an automobile, and a pulley to be contacted with
a belt for driving accessory of an automobile.
In a timing belt for an engine df an automobile, or
an accessory driving belt, a pulley is arranged so as to
increase an angle of contact of a belt for the purpose of
applying an appropriate tension to the belt. Fig. 1Z shows
a constructional example of a timing belt. This timing
belt includes a belt E which is stretched around a driving
pulley A secured to a crankshaft, a driven pulley B, B
secured to a camshaft, a tensioner pulley C rotatably
mounted on a stationary shaft, and an idler pulley D
mounted on a stationary shaft. Among the above-mentioned
pulleys, the pulleys C and D mounted on the respective
stationary shafts are usually constituted by a ball bearing
supported pulley. The ball bearing is fitted within the
inner diameter of the pulley. It is noted that the
stationary shaft for the tensioner pulley C is displaceably
supported in elongated openings provided in a frame for
supporting the tensioner pulley. By this, tension
adjustment of the belt is permitted.
Such a kind of pulley may include a pulley in which
a peripheral surface of the pulley to be engaged by a belt
is provided directly around the outer diametez~ of an outer
1
ring of a ball bearing (called a hack type outer ring). It
is noted,. however, that a pulley of the type shown in Fig_
13 is frequently used. This pulley includes a pulley body
1I having a peripheral surface llc and a ball bearing 12
which are engaged with each other as a unit.
The pulley body 11 is pressed from a steel plate,
The pulley body 11 includes an outer cylindrical portion
lla around which a belt is extended, and an inner
cylindrical portion llb fitted over.an outer ring 12a of
the ball bearing 12. A peripheral surface Ilc of the
pulley is provided around the outer diameter of the outer
cylindrical portion 11a. The ball bearing 12 includes the
outer ring 12a fitted within the inner cylindrical portion
llb of the pulley body 11, an inner ring 12b fitted over a
stationary shaft (not shown), a retainer 12d for retaining
a plurality of balls 12c provided in a space between the
raceway surf aces of the inner and outer rings 12b and 12a,
and a seal 12e for sealing a grease.
In the above-mentioned pulley, and when the pulley
body 11 is rotated by a rotational driving force from the
belt, the outer ring 12a of the ball bearing 12a fitted
within the pulley body is rotated integrally with the
pu 1 ley . body 1 I .
In the above-mentioned pulley, the ball bearing 12
is of a outer ring rotation type, and usually, a deep
groove ball bearLng is used provided with zero contact angle.
When the above-mentioned pulley is driven under
cold ambient, abnormal noise (hoot sound) may be caused,
depending upon a given specification of the pulley and/or
2
operational condition. Such abnormal sound under cold
condition, i. e., abnormal noise under cold ambient is not
always caused during use. Occurz-ence of such abnormal
noise under cold ambient greatly deper~d5 upon a given
ambient temperature. Thus, it occurs only in a very
limited area (for example, Hokkaido Prefecture in Japan).
Such abnormal~noise under cold ambient occurs in a brief
time (within one minute at the longest) after an engine
start of an automobile. Thereafter, no abnormal noise is
caused. Abnormal noise is frequently caused when a deep
groove ball bearing of a single row type is used as a ball
bearing_ Occurrence of abnormal noise is reduced when an
angular ball bearing of a plural row type is used.
Abnormal,~noise under cold ambient has a:eomplexed
nature as mentioned above, so that it is difficult to
reproduce such abnormal. noise under cold ambient.
Accordingly, the cause or mechanism for the occurrence of
abnormal noise has not been definitely clarified. As far
as a pulley for use with an automobile is concerned, it is
operated at a high temperature and at a high speed. Thus,
durability is one of the important factors for such
pulleys, Accordingly, any counter-measures leading to a
reduction in durability could not be employed.
For the reasons given above, no particular means
for elimination of such abnormal noise under cold ambient
has been proposed heretofore.
Conventionally, a grease having a superior property
at lower temperature (being able to form uniform oil film
in the contact portions between the rolling element and the
' 3
C~2184~40
raceway surfaces of the inner and outer rings) has been
proposed in order to eliminate abnormal noise under cold
ambient. This counter-measure is intended to restrict
occurrence of abnormal noise under cold ambient by
increasing lubrication ability of a grease under cold
ambient, and expected to give a relatively high effect. It
is noted, however, that such a grease has an lower
viscosity, so as to provide an insufficient lubrication
ability at high temperature. This may lead to a reduced
durability.
Accordingly, it is the main object of the invention
to provide means, keeping the function of a pulley, for
effectively restricting or preventing occurrence of
abnormal noise under cold ambient, while, at the same time,
satisfying durability and cost effectiveness.
SUMMARY OF THE INVENTION
Generally speaking, ozl film on a raceway surface
tends to become uneven and irregular during cold ambient.
due to the increase in viscosity of base oil of a grease_
When such unevenness and irregularity of the oil film
occur, the friction coefficient between a rolling element
and the raceway surface is caused to be periodically
changed within a small range, so as to cause self-excited
vibration of the rolling element.
The applicant has discovered several mechanisms to
be occurred during a test for reproducing abnormal noise
under cold ambient.
1. When abnormal noise occurred under cold
ambient, a pulley (outer ring) was being oscillated in the
4
C A2184 ~ 4~J
axial direction. The frequency component at that time
corresponded to the acoustic frequency of the abnormal
noise (hoot sound) under cold ambient.
2. When no abnormal noise occurred unde r cold
ambient, the above frequency component could not be found.
3. T'he frequency component when abnormal noise
occurred under cold ambient, the same phase is recognized
at two measuring points 180 degrees on the end face of the
pulley_
Although a mechanism in which abnormal noise under
cold ambient occurs has not been completely analyzed, it is
considered fxom the above xesults that the abnormal noise
under cold ambient is caused mainly by the fact that
resonance of vibration of the pulley system is caused by
self-excited vibration of the rolling element, so that the
outer ring is caused to be oscillated in the axial
direction (translational movement).
The present invention is aimed, based on the above
assumption, a,t provision of a construction or arrangement
for effectively restricting axial vibration of the outer
ring due to the self-excited vibration of the rolling
element, in order to eliminate abnormal noise. under cold
ambient.
Accordingly, the present invention provides a
pulley including a pulley body having a peripheral surface
which is contacted with a belt to be driven by an engine of
an automobile. The pulley body is fitted on the outer
diameter of an outer ring of a ball bearing. The ball
bearing is arranged in a single row, so as to give a
C~2~ ~4~ ~~
contact angle. By this, behavior of the rolling element,
in particular, the behavior in the axial direction may be
restricted, so that the self--excited vibration of the
rolling element is effectively restricted.. By this,
frequency components in the axial direction of the pulley
may be restricted. The term "single row" is meant to
express a ball bearing having a single row of rolling
element. The term "contact angle" is meant to indicate an
angle tv be defined by a line along which a load is applied
to the rolling element and a plane perpendiCUlar to the
central axis of the ball bearing. When the contact angle
is increased, the effect to restrict the self-excited
vibration of~ the rolling element is increased, so as to
restrict occurrence of abnormal noise under cold ambient.
It is noted, howevex, that, when the contact angle is
excessively increased, disadvantages such as decrease in
service life of the bearing may occur, Accordingly, the
contact angle should be selected at an appropriate value,
considering the above advantages and disadvantages.
It is desirable that each ball of the ball bee ring
and, among the inner and outer rings, at least the outer
ring are contacted at two points. The inner ring and each
ball may be contacted at one point or at two points.
It i,s not likely that a uniform load is applied to
the two contact points, even when the outer ring and the
rolling element are contacted at two points. Usually, a
load is concentrated to only one contact point by reason of
vibration of the belt sv that sliding friction xs
frequently caused at the other contact point. Usually,
6
'~~~2184~ 4f~
such sliding friction would disappear in brief of time. It
is noted, however, that the sliding friction would continue
for an extended period of time, depending upon the ambient
in which the bearing is used. There would be a risk in
which one contact point is heated to a high temperature due
to friction heat, so as to degrade the bearing ability.
In order to eliminate the above problem, an oil
groove is provided at a position adjacent to each contact
position between the raceway surface of the outer ring and
the rolling element, in accordance with the invention,
During running of the bearing, the grease contained within
the oil grooves is continuously supplied to the two contact
points, so that they may be lubricated by the grease.
Thus, either one of the contact points may be prevented to
be heated to an extremely high temperature, even when it
lacks oil film. Certain quantity of grease may be
maintained within the oil groove even after the shut down
of the operation. Thus, uniform oil film may be quickly
formed in the raceway surface of the outer ring at the time
of restarting of the operation. In this respect, it is
also possible to restrict occurrence of abnormal noise
under cold ambient which is caused mainly by unevenness of
oil film upon restarting of the operation. After shut down
of the operation, grease is flown into the lower portion of
the bearing, i. e., the bottom of the oil groove.
The present invention also provides a ball bearing
for a pulley. The ball bearing includes an outer ring
having an outer diameter. The outer diameter of the
bearing is fitted within a pulley body of the pulley. 'fhe
cA2~ 84~ ~.o
pulley body includes a peripheral surface which is engaged
by a belt to be driven by an engine of an automobile. The
ball bearing is arranged in a single row so as to give a
contact angle.
The invention also provides a ball bearing having
an outer ring. The outer diameter of the outer ring is
fitted within a pulley body having a peripheral surface
which is engaged by a belt to be driven by an engine of an
automobile. The ball bearing is arranged in a singly xow,
A rolling element of the bearing and, among the inner and
outer rings, at least the outer ring are contacted with
each other at two points. An oil groove is provided at a
position adjacent to each Contact position between the
raceway surface of the outer ring and the rolling element.
When the raceway groove of the outer ring of the
ball bearing is configured to be Gothic arch, elliptic,
parabolic or hyperbolic, each ball and the outer ring may
be contacted at two points. When the raceway groove of the
inner ring is similarly configured, each ball and the inner
ring may be contacted at two points. It is also noted that
the pulley body and the outer ring may be integrally formed.
The above-mentioned constructions may all be
similarly applied to a fan for forcibly cooling cooling
water of an engine. Sometimes, such a fan is rotatably
mounted on a shift through a ball bearing, the shaft being
driven by the engine. In such a case, abnormal noise under
cold ambient may be caused mainly due to the self-excited
vibration of the rolling element.
In accordance with the invention, a belt is
8
extended between a~drive pulley and a driven pulley. The
belt includes a drive surface and a backside surface. The
drive surface of the belt is engaged with the driving
pulley and the driven pulley. An idler pulley is disposed
between the driving pulley and the driven pulley. The
idler pulley includes a pulley body hav~.ng a peripheral
surface which is engaged by the belt. The pulley body is
fitted over the outer diameter of the outer ring of a ball
bearing. The pulley body and the outer ring may be
integrally formed. The idler pulley is engaged with the
backside surface of the belt. The idler pulley and the
backside surface of the belt are contacted through two or
more recess/protrusion engagement portions spaced along the
width of the belt.
By this, anti-vibration effect of the belt is
exerted, so as to restrict behavior, in particular, the
axial behavior, of the outer ring, so that vibration of the
outer ring in the axial direction is effectively
restricted, whereby high frequency component in the axial
direction of the pulley may be restricted. The term "idler
pulley" is meant to indicate a pulley rotatably supported
by a stationary shaft. Thus, not only the idler pulley D,
but also the tensioner pulley C shown in Fig. 12 is
included in the category of "idler pulley".
A belt according to the invention may he utilized
in a belt transmitting device including an idler puJ.Iey
disposed between a driving pulley and a driven pulley, the
idler pulley including a pulley body having a peripheral
surface. The pulley body is fitted on the outer diameter
9
of a outer ring of a ball bearing. The belt includes a
drive surface and a backside surface. The drive surface is
engaged with the drive pulley and the driven pulley. The
hack side surface is engaged with the drive pulley and
extended between the drive pulley and the driven pulley.
The backside surface of the belt is provided with plural
rows of engagement portions, the engagement portion being
foamed by a recessed groove or a protrusion.
The idler pulley according to the invention may be
used in a belt transmitting de vice. The belt transmitting
device includes a belt extended between a drive pulley and
a driven pulley. The belt includes a drive surf ace and a
backside surface. The drive surface is engaged with the
drive pulley and the driven pulley- The idler pulley
includes a pulley body having a peripheral surface which is
engaged with the belt. The pulley body is fitted on (or
integrally formed with ) the outer diameter of an outer
ring of a ball bearing. The idler pulley is engaged with
the backside surface of the belt and disposed between the
drive pulley and the driven pulley. The peripheral surface
of the pulley is provided with plural rows of. annular
engaged portions wh~.ch is formed by a recessed groove or a
protrusion.
Due td the above construction, the present
invention provides pax-ticular advantages mentioned below.
1. By giving a contact angle to the ball bearing.
or by contacting together the outer ring and the rolling
element of the ball bearing at two points, the behavior, in
particular, the behavior in the axial direction of the
rolling element may be restricted. By this, self-excited
vibration, which is considered to be one of the causes for
the occurrence of abnormal noise under cold ambient, may be
effectively x'estricted. Angular deflection of the pulley
may be reduced. Thus, vibration of the belt is restricted,
so as to increase durability and ability of the belt and
the ball bearing.
Z. A grease reservoir, may be formed, depending
upon the configuration of the raceway surface. The grease
reservoir advantageously contributes to the formation of
oil film.
3. When an oil groove is formed at a position
adjacent to each~contact position between the raceway
surface of the outer ring and the rolling element, a grease
reservoir may be provided. When sliding friction is caused
at one of the contact points, lack of oil film at that
contact point may be restricted, so as to maintain an
increased lubrication condition. Uniform oil film may be
quickly formed in the raceway surface of the outer ring by
means of the grease contained within the oil groove, upon
restart of the operation. This, together with the above
means (the outer ring and the rolling element are contacted
at two points), reliably prevents occurrence of abnormal
noise under cold ambient.
4. In the belt transmitting device, the idler
pulley and the backside surface of the belt are engaged
through two or more recess/protrusion engagement portions
spaced along the width of the belt. By this, anti--
vibration effect of the belt is exerted, so as to restrict
1I
i~~ ~ ~~
the behavior, in particulaz~, the axial behavior of the
outer ring. Thus, it is possible prevent occurrence of
abnormal noise under cold ambient.
5. The above advantages may be brought about,
regardless of the type of seal grease. Unlike prior art
pulley utilizing a grease having superior property at low
temperature. decrease in durability at high temperature
will not be expected. The invention does not require
complexed construction of the bearing. The invention also
permits mass-production of the 'products in cost-effective
manner.
The above-mentioned advantages 1 to 3 and 5 may be
similarly obtained when the invention is applied to a
cooling fan for forcibly cooling water for an engine.
BRIEF bESCRIPTION OF THE DRAWINGS
Fig_ 1 is a cross-sectional view showing a pulley
according to the invention;
Fig_ 2 is a cross-sectional view showing a ball
bearing fitted in the pulley;
Fi,g. 3 shows test conditions and the results of a
performance test on a pulley incorporating a four-point
contact ball bearing aceo~ding to the invention;
Fig. 4 is a cross-sectional view showing angular
deflection when an outer ring and a ball are contacted at
one point;
Fig_ 5 is a cross-sectional view showing a three-
point contact ball bearing;
Fig. 6 is a cross-sectional view showing a pulley
according to the invention;
I2
7?;4~~
Fig. 7 is a cross-sectional view showing a ball
bearing fitted in the pulley shown in Fig. 6;
Fig. 8 is a cross-sectional view showing a three-
point contact ball bearing:
Fig. 9 is a cross-sectional view showing a ball
bearing having an oil groove in the boundary between a
raceway surf ace and the inner diametrical surface of the
outer ring;
Fig. 10 is an enlarged view, in section, of ~a main .
part of an idler pulley to be used in a belt transmission
according to the invention:
Fig. I1 is a cross,sectional view showing an idler
pulley having a pulley body of a different configuration;
Fig. 12 is a front elevational view showing one
constructional example of a timing belt for an automobile;
Fig. 13 is a cross-sectional view showing a pulley
according to prior art;
Fig. 14 is a cross-sectional view showing one
constructional. example of a cooling fan; and
Fig. 15 is an enlarged front elevational view
showing a hole provided in a plate of a clutch mechanism.
DES R~ON OF PREFERRED EMBODIMENTS
A pulley and a ball bearing for a pulley according
to the invention will be explained with reference to Figs.
1 to 9.
The pulley shown in Fig. 1 is an idler pulley to be
used in a timing belt for an automobile. The pulley
includes a pulley body 1 pressed from a steel plate, and a
ball bearing 2 of a single row type fitted within the inner
13
~,~~ o ~?~ ~ ~~.r~
diameter of the pulley body 1. The pulley 1 is constructed
by an annular body including an inner cylindrical portion
la, a flange portion 1b extending radially outwardly from
one end of the inner cylindrical portion la, an outer
cylindrical portion lc extending axially from the flange
portion 1b, and a collar portion 1d extending radially
inwardly from the other end of the inner cylindrical
portion la. An outer ring 2a of the ball bearing 2 is
fitted within the inner diameter of the inner cylindrical
portion la. The outer cylindrical portion lc has its outer
diameter a peripheral surface 1e with which a belt (not
shown) is engaged or contacted. The pulley serves as an
idler since the peripheral surface 1e is contacted with the
belt.
Fig. 2 is a cross-sectional view showing the ball
bearing 2 fitted in the pulley. The ball bearing 2 is a
four-point contact ball bearing. The ball bearing includes
an outer ring 2a fitted within the inner diameter of the
inner cylindrical portion 1a of the pulley body 1, an inner
ring 2b fitted in a stationary shaft (not shown) , a
plurality of balls (rolling elements) 2c provided between
the raceway surfaces 3b. 3a of the inner and outer rings
2b, 2a, a retainer 2d for retaining balls 2c equidistally
in the circumferential direction, and a pair of seals 2e
for sealing a quantity of grease. The outer ring 2a and
the inner ring 2b are separately formed in an integral
form. The raceway surface 3a of the outer ring Za and the
raceway surface 3b of the inner ring 2b of the ball bearing
form a so-called Gothic arch groove having two centers of
14
CA213~+1 ~-~
curvature, Thus, the raceway surfaces form a predetermined
contact angle " ~ " when they are in contact with the
balls. That is to say, the ball 2c and the outer ring 2a,
and the ball 2c and the inner ring 2b, respectively are in
contact with each other at two points between which the
deepest portion of the raceway surface 3a or 3b is
positioned. The~raceway surfaces 3a, 3b may take another
configuration, other than the Gothic arch groove, which has
a curvature in the contact area greater than that of the
ball Zc, such as an elliptic, parabolic or hyperbolic groove.
Fig. 3 shows test condition and the test results of
a test performed on a pulley incorporating the f our-point
contact ball bearing according to the invention, which test
having been conducted under the condition which the
applicant has once found to reproduce abnormal noise at
cold condition.
Since the contact angle ' ~ " (alpha) is applied to
the ball bearing 2, the behavior of the ball 2c, in
particular the behavior in the axial direction, is
restricted, so that occurrence of self-exc~.ted vibration
may be effectively restricted. Since the Gothic arch is
provided. grease reservoirs 4, 5 are formed at the bottom
of each of the raceway surfaces 3a, 3b. This
advantageously contributes to the formation of grease film,
in particular under cold circumstance.
In a con~rentional deep groove ball bearing, it is
considered that, strictly speaking, the ball Ze and the
outer ring 2a are contacted with each other at one point.
as shown in Fig. ~. Thus, when a belt is driven by the
1S
pulley, the outer ring Za is frequently caused to be
oscillated about the contact point between the outer ring
2a and the ball Zc as a center of oscillation. as shown in
Fig. 4 by two~dotted line. This phenomenon is generally
referred to as an "angular deflection". On the contrary,
and in accordance with the present invention, the ball 2c
and the outer ring 2a are contacted with each other at two
points, as mentioned above. Thus, it is possible to reduce
the angular deflection of the outer zing Za, so that
vibration of the belt may be restricted, It is also
possible to prevent leakage of the grease within the
bearing, whereby durability of the belt and the bearing may
be increased.
Although the four-point contact ball bearing has
been explained in the above, the ball bearing is not
restricted to such a four~point contact ball bearing.
Specifically, it is possible to restrict the behavior of
the balls to a substantial degree, provided that a contact
angle " a ".is defined at least between the outer ring 2a
and the ball 2c, and that the outer ring 2a and the ball Zc
are contacted with each other at two points, so that
occurrence of abnormal sound under cold ambient is
restricted. Accordingly, a three-point contact ball
bearing shown in Eig. 5 may be used, wherein the inner ring
2b and the ball Zc are contacted at one point. It is also
noted that the same advantages may be obtained by
integrally forming the pulley body 1 and the outer ring 2a
of the ball bearing Z, so as to give a contact angle " a "
to the ball bearing portion.
16
A pulley shown in Fig, 6 is an idler pulley for use
with an accessory drive belt of an automobile. This pulley
is the same in construction as the pulley shown in Fig. 1,
with the exception of the construction of the ball bearing 2.
Fig. 7 is a cross-sectional view showing a ball
bearing 2 fitted in the pulley shown in Fig. 6. The ball
bearing 2 is a four-point contact ball bearing which is the
same as that shown in Fig. 2. The raceway surface of the
outer ring Za and the raceway surface 3b of the inner ring
2b define a so-called Gothic arch groove having two centers
of curvature. Thus, the raceway surfaces form a
predetermined contact angle "a " when they are in contact
with, the balls. That is to say, the ball Zc and the outer
ring 2a, and the ball Zc and the inner ring 2b,
respectively are in contact with each other at two points
between which the deepest portion of the raceway surface 3a
or 3b is positioned (the contact points between the ball Zc
and the raceway surface 3a of the outer ring are indicated
by P and Q in the drawing.).
Annular grease reservoirs 4a, 4b are respectively
formed in the deepest portions of the raceway surfaces 3a,
3b respectively. The grease reservoirs facilitate
formation of ail film, particularly under cold ambient_
The configuration of each of the grease reservoirs 4a, 4b
may be desirably determined. For example, the Gothic arch
groove may be used, as in the case of the reservoir 9b in
the inner ring. Alternatively, a recessed groove may be
used, as in the case of the reservoir 4a in the outer ring.
In this case, the raceway surfaces 3a, 3b may also
17
,,
~~~~~~~~!
take another configuration, other than the Gothic arch
groove, which has a curvature in the contact area greater
than that of the ball 2c, such as an elliptic, parabolic or
hyperbolic groove.
Oil grooves 5, 5 in the form of annulus having its
center at the shaft center 0-0 are formed in~the raceway
surface 3a of the outer ring adjacent to the contact points
P, Q between the outer ring 2a and the ball 2c. The grease
reservoir 4a is positl.oned between the oil grooves 5, 5.
The oil grooves 5. 5 are disposed slightly radially
inwardly of the respective contact points P, ~, so that the
grease may be surely supplied to the contact points P, Q
due to the centrifugal force during rotation of the
pulley, The locations of the oil grooves 5, 5 from the
shaft center 0-0 are the same, so as to cause the same
amount of grease to be flown into the respective contact
points.
When the outer ring 2a and the ball Zc of the ball
bearing 2 are contacted at two points, as mentioned above,
the behavior of the balls 2c, in particular, the behavior
in the axial direction of the balls 2c is restricted, so
that occurrence of abnormal noise under cold ambient due to
self--excited vibration of balls Zc may be effectively
restricted.
lNhen a load is concentrated to one of the contact
points due to the vibration of the belt, while the other
contact point is caused to generate heat due to the sliding
friction, a quantity of grease is supplied to the other
contact point from the oil groove 5 at a radially inward
18
L~~~~~~~l;1~~1
position by reason of a centrifugal force, for the purpose
of lubrication. By this, lacking of oil film at the
contact point may be prevented, so as to maintain an
inexeased lubrication condition. It is also noted that
certain quantity of grease is kept in the oil grooves 5
even after the shutdown of the operation. By this, a
uniform oil film may be quickly formed in the raceway
surface 3a of the outer ring at the time of restarting.
From this point of view, it is also possible to restrict
occurrence of abnormal noise under cold ambient.
Another ball bearings, other than the four-point
contact bearing ball Z, may be used, at least provided that
the outer ring Za and the ball 2e are contacted at two
points. Por example, a three-point contact bearing ball
may be used wherein the inner ring 2b and the ball 2c are
contacted at one point, as shown in Fig. 8_ The oil
grooves 5, 5 may be provided at any position adjacent to
the contact points P, Q. The oil grooves may be provided
at the boundary between the raceway surface 3a of the outer
ring 2a and the inner diametrical surface. Similar
advantages may be obtained when the pulley body 1 and the
outer ring Za of the ball bearing 2 are integrally formed.
It is noted that the above-mentioned abnormal noise
under cold ambient may be caused not only in the case of
the pulley, but also in the case of a cooling fan for
forcibly cooling a quantity of cooling water of a
radiator. As shown in Figs. 14 (a) and (b), the fan 30
includes an annular casing (rotatable member) 35, and a
plurality of blades 31 attached to the periphery of the
19
~'~~~~ ~4? 40
casing 35 and extending in the radial direction. The
casing 35 is fitted over an outer ring 32a of a ball
bearing 32. The fan 30 is rotatably mounted on a main
shaft 33 which is rotated by an engine (the main shaft is
bolted td a flange portion far example of a pump shaft). A
temperature-responsive clutch mechanism 34 is disposed
between the main shaft 33 and the fan 30. The temperature-
responsive clutch mechanism is adapted to be engaged and
disengaged in .accordance with a temperature change of the
outside air. .Thus, a torque may be.transmitted from the
main shaft 33 through the clutch mechanism 34 to the f an
30. An exemplary construction for the clutch mechanism 34
will be explained below.
A drive disk 36 is fixedly fitted over the main
shaft 33 at its forward end. The drive disk 36 is rotated
in unison with the main shaft 33, A disk-shaped plate 37
is disposed at the forward end side of the drive disk 36.
The plate 37 and the casing 35 cooperate to form a first
chamber 39 serving as a torque transmission chamber
therebetween. The plate 37 and a covet 38 cooperate to
form a second chamber 40 serving as a reservoir for oil
(viscid Cviscous] fluid for torque transmission, such as
silicone oil or the like). A plate spring 42 is disposed
in the second chamber 40. The plate spring 42 has one end
attached to a valve 41 and the other end secured to the
plate 37. A bimetal 43 is secured to the coven 38. A
piston 44 is mounted on the bimetal 43. The piston 44 is
arranged coincidently with the axis (0-0) of the main shaft
33.
i
~~2 ~ 8414fl
In the above construction. the bimetal 43 would not
be bent hardly, when the outside air temperature is low, as
shown in Fig. 14(a), so that the piston 44 urges the plate
spring 42 to the right-hand side in the drawing. At this
time, the valve 41 attached to the plate spring 42 extends
through a hole 45 in the outer diameter portion of the
plate 3? and contact with the front surface of the drive
disk 36 in the first chamber 39. The hole 45 includes, as
shown in Fig. 15, an insertion hole 45a and a connective
hole 45b continuously formed therewith. The valve 41 is
inserted into the insez~tion hole 45a. Since there exists
always a relative.velocity as between the drive disk 36 and
the side of the casing 35 or the valve 41, the oil
(indicated by numerous dots) between the drive disk 36 and
the plate 37 is scraped out therefrom into the second
chamber 40 through the connective hole 45b, by means of the
valve 41 serving as a weir. In this condition, most oil in
the first chamber 39 is flown into the second chamber 40,
so that only a small quantity of oil is remained in the
first chamber 39. Thus. the transmitting torque is
reduced, so that the rotational speed of the fan 30 becomes
low. It is noted that the arrow mark in Fig. 15 indicates
the direction of rotation of the drive disk 36.
When the outside air temperature is high, the
bimetal 43 is bent as shown in Fig. 14(b). Thus, the valve
41 is displaced in the left-hand side in the drawing,
whereby the piston 44 is disengaged from the hole 45 by
reason of the elasticity of the plate spring 42. Thus, the
above-mentioned scraping-out effect is disabled, so that
21
r~;~.~4~ ~(~
the oil in the first and second chambers 39, 40
respectively are communicated with each other through the
hole 45, so as to form the same level. At this time, the
oil is filled to the effective transmission surface of the
first chamber 39, so that a predetermined amount of torque
may be transmitted, so as to increase the rotational speed
of the fan 30.
When the above-mentioned fan 30 incorporates a ball
bearing having a construction the same as that of the above-
mentioned ball beaxing for the pulley, occurrence of
abnormal noise under cold ambient may be reliably prevented.
Now, a belt transmitting device according to the
invention will be explained with reference to Figs. 10 and
11.
The pulley shown in Fig. 10 is an idler pulley for
use in an accessary drive belt of an automobile. The
pulley includes a pulley body 1 pressed from a steel plate,
and a deep groove ball bearing of a single row type fitted
within the inner diameter of the pulley body 1. The pulley
body 1 is constructed by an annular body which includes an
innex cylindrical portion la, a flange portion 1b extending
radially outwardly from one end of the inner cylindrical
portion la, an outer cylindrical portion lc extending
axially from the flange portion 1b, and a collar 1d
extending radially inwardly from the other end of the inner
cylindrical portion la. An outer ring 2a of the ball
bearing 2 is fitted within the inner diameter of the inner
cylindrical portion la. A peripheral surface Ie fo.r
contact with a back side surface 4b of the belt 4 is
22
provided in the outer diameter of the outer cylindrical
portion lc. The peripherally surface 1e is contacted with
the belt 4, so that the pulley serves as an idler.
The ball bearing Z includes an outer ring 2a fitted
within the inner diameter of the inner cylindrical portion
la of the pulley body 1, an inner ring 2b fitted over a
stationary shaft (not shown), a plurality of balls disposed
in a space between the raceway surface 3b of the inner ring
2b and the raceway surface 3a of the outer ring 2a,~ a
retainer 2d for equidistantly retaining the balls 2c in the
circumferential direction, and a pair of seals 2e for
sealing a guantity of grease. The outer ring 2a and the
inner ring 2b are separately formed in an integral form_
The belt 9 includes a drive surface 4a and the back
side surface 4b. The back side surface 4b of the belt 4 is
formed with a pair of engagement portions 5 spaced along
the width of the belt 4. Each of the engagement portions 5
is a protrusion having a cross-section of a substantially V-
shaped configuration. The engagement portions 5 are
arranged in parallel with each other and extend entirely
along the periphery of the back side surface 4b of the belt
4_ The periphe~'al surface 1e of the pulley body 1 is also
provided with a pair of engaged portions 6 which are also
spaced from one another along the width of the belt 4.
Each of the engaged portion 6 is formed ~.nto a
configuration of recessed groove so as to be engageable
with a respective engagement portion 5.
A V-belt is known in the art as a belt having a
protrusion. It is noted, however, that, in such a known V-
23
~A~~~~~
belt, the protrusion is provided in the drive surface 4a to
be engaged with a drive pulley or a driven pulley. Thus,
it is different in construction from the above-mentioned
belt 4 in which the protrusion is provided in the backside
surface 4b. Accordingly, known Y-belt is not used in the
above-mentioned transmitting device.
The back side surface 4b of the belt 4 and the
peripheral surface le of the pulley are engaged with each
other through the recesses and protrusions provided at two
positions spaced along the width of the belt 4. Thus, the
belt 4 restricts the outer ring Za in the axial direction,
so as to restrict occurrence of vibration of the outer ring
in the axial direction. By this, occurrence of abnormal
noise under cold ambient may be restricted.
Fig. 11 shows a pulley body 1 formed from a thick-
walled cylinder. The pulley body 1 is fitted over an outer
ring 2a of a bearing 2, In this case, it is also possible
to obtain the advantages the same as those obtained in the
pulley shown in Fig,~l0. Similar advantages may be also
obtained, when the pulley body 1 and the outer ring 2a are
integrally formed.
The above-mentioned advantages may be obtained not
only from the construction in which, as shown in Figs. 10
and 11, the engagement portion 5 in the backside surface 4b
of the belt is a protrusion, and the engaged portion B in
the peripheral surface le of the pulley is a recessed
groove, but also from the construction in which. on the
contrary to the above, a recessed groove is provided in the
backside surface 4b of the belt and a protrusion is
z4
0218414p
provided in the peripheral surface 1e of the pulley. It is
also possible to provide a protrusion and a recessed
groove, arranged in parallel with each other, in the
backside surface 4b of the belt and to provide a recessed
groove and a protrusion to be engaged with the above
protrusion and recessed groove, respectively, i.n the
peripheral surface 1e of the pulley.
The number of the engagement portions) 5 and the
engaged portions) is desirably selected. One or more rows
of engagement/engaged portions may be provided. It is
noted, however, that.the outer ring 2a is not sufficiently
restricted In the axial direction when a single row of
engagement/engaged portion is provided. Thus, it is
desirable to provide two or more rows of engagement/engaged
portions, so as to effectively restrict occurrence of
abnormal noise.
The invention is not limited, in its application,
to the above--mentioned timing belt of an automobile, The
invention is applicable to any belt tranmitting device in
which one or more idler pulleys C, D are disposed between a
drive pulley (A in Fig. 10) and one or more driven pulleys
(B) .
