U.S. patent application number 09/382204 was filed with the patent office on 2001-12-13 for metal v-belt.
This patent application is currently assigned to Schaukowitch, Carl. Invention is credited to KANEHARA, SHIGERU, SHIMADA, TAKAMICHI.
Application Number | 20010051554 09/382204 |
Document ID | / |
Family ID | 17126178 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010051554 |
Kind Code |
A1 |
KANEHARA, SHIGERU ; et
al. |
December 13, 2001 |
METAL V-BELT
Abstract
Clearance Cs during a no-load stop and allowable value Cto of
total clearance Ct obtained as a sum of clearance Ch occurring due
to Hertzian stress are stipulated to a value less than height h of
male coupling 28 along with an allowable value .sigma.hmo of the
maximum Hertzian stress acting on rocking edge 26 being stipulated
to a value less than an upper limit value .sigma.ho of the Hertzian
stress that satisfies the opposing pitching lifespan. The radius of
curvature R of the rocking edge is set within a range that
satisfies R1.ltoreq.R.ltoreq.R2 for the radius of curvature R1
determined in correspondence with the allowable value .sigma.hmo of
the maximum Hertzian stress and the radius of curvature R2
determined in correspondence with the allowable value Cto of the
clearance between the total elements.
Inventors: |
KANEHARA, SHIGERU;
(WAKO-SHI, JP) ; SHIMADA, TAKAMICHI; (WAKO-SHI,
JP) |
Correspondence
Address: |
ARENT FOX KINTER PLOTKIN & KAHN PLLC
1050 Connecticut Avenue,
N.W., Suite 600
Washington
DC
20036-5339
US
|
Assignee: |
Schaukowitch, Carl
|
Family ID: |
17126178 |
Appl. No.: |
09/382204 |
Filed: |
August 23, 1999 |
Current U.S.
Class: |
474/242 |
Current CPC
Class: |
F16G 5/16 20130101 |
Class at
Publication: |
474/242 |
International
Class: |
F16G 005/16; F16G
001/22; F16G 001/21 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 1998 |
JP |
10-244936 |
Claims
What is claimed is:
1. A metal V-belt that comprises an endless belt shaped metal ring
member and a plurality of metal element members supported along
said metal ring member and that transmits power between a drive
pulley and a driven pulley, said metal element members have a
cross-sectional convex circular arc-shaped rocking edge with an
axis leaning against said opposing front and rear metal element
members along with having a convex portion and a concave portion on
the front and rear principal planes and by means of engaging said
opposing front and rear metal element members together, said convex
portion and said concave portion can be lined up in a row at the
front and rear on said metal element members and, the radius of
curvature R of said rocking edge is stipulated such that an
allowable value of a clearance between the total elements obtained
as a sum of a clearance between the elements during a no-load stop
when said metal V-belt is stretched between said drive pulley and
said driven pulley and a clearance between the elements occurring
due to Hertzian stress acting on said rocking edge of said metal
element members while said metal V-belt is transferring power is a
value less than the protruding height of said convex portion.
2. A metal V-belt as set forth in claim 1 characterized by each
said metal element member having a front surface and a rear surface
parallel to each other and a this front surface and rear surface
forming said principal plane, and a tapered surface whose thickness
reduces towards said rear surface side being formed on the lower
half of said front surface, and said rocking edge being formed
extending laterally at the boundary between said front surface and
said tapered surface, and said rocking edge having a convex
circular arc-shaped radius of curvature R in a cross-sectional
shape along the perpendicular surface extending forward and
rearward.
3. A metal V-belt as set forth in claim 2 characterized by on each
said metal element member said concave portion comprising a
cylindrical-shaped protruding female coupling and is formed on said
front surface and said convex portion comprising a
cylindrical-shaped protruding female coupling and is formed on said
rear surface, said male coupling engaging said female coupling of
the opposing front and rear metal element members forming a
composition wherein a plurality of metal element members are linked
in a row.
4. A metal V-belt as set forth in claim 1 characterized by said
clearance Cs during a no-load stop being calculated by the equation
Cs=Co-.DELTA.C from a reduced clearance amount .DELTA.C when an
initial clearance Co is wound between said drive pulley and said
driven pulley in a natural toroidal state.
5. A metal V-belt as set forth in claim 1 characterized by the
radius of curvature R of said rocking edge being stipulated such
that the maximum Hertzian stress acting on said rocking edge while
said metal V-belt is transferring power is a value less than the
allowable Hertzian stress that satisfies the opposing pitching
lifespan of said metal element members.
6. A metal V-belt as set forth in claim 5 characterized by the
radius of curvature R of said rocking edge being set within a range
that satisfies R1.ltoreq.R.ltoreq.R2 for a minimum radius of
curvature R1 when said maximum Hertzian stress is a value less than
the allowable Hertzian stress and a maximum radius of curvature R2
determined in correspondence with the maximum allowable value of
clearance between said total elements.
Description
FIELD OF THE INVENTION
[0001] The present invention is related to a metal V-belt used as a
power transmission means in a V-belt infinite variable-speed drive
and in particular to a metal V-belt that comprises metal
elements.
BACKGROUND OF THE INVENTION
[0002] This type of metal V-belt is already known conventionally
and is comprised by an endless belt shaped metal ring and a
plurality of elements supported along the metal ring. Further, this
metal V-belt transmits power between a drive pulley and a driven
pulley. Both of these pulleys can variably control the V channel
width and by means of variably controlling this V channel width,
the wrapping radius of the V-belt on both pulleys can be changed
and the change gear ratio changed in infinite steps.
[0003] FIG. 8 and FIG. 9 show examples of the composition of the
elements used in this type of metal V-belt. The element 30 has a
front surface 31 and a rear surface 32 parallel to each other and a
tapered surface 33 is formed on the lower half of the front surface
31. This tapered surface gradually changes its thickness along the
rear surface 32. Further, on the left and right sides of the
element 30 a ring channel 34 is formed whereon is attached a metal
ring (not shown in the figure).
[0004] A V side face 35 is formed on both the left and right sides
of the tapered surface 33. This V side face is supported on a
slanted surface of a pulley (not shown in the figure). The boundary
between the front surface 31 and the tapered surface 33 is a
rocking edge 36. Each element 30 allows this rocking edge 36 to
make contact with the rear surface 32 of the preceding adjacent
element 30 on the pulley allowing this to lean frontward and
rearward as an axis. Because of this, the V-belt can wind on the
pulley. Further, a cylindrical-shaped protruding male coupling 37
is formed on the front surface 31 and a round-shaped hole female
coupling 38 is formed on the rear surface 32. Both of these
couplings 37, 38 are engaged and connect to each other between
adjacent elements 30, 30 which in turn lines up forming one row on
the metal ring.
[0005] In a metal V-belt with this type of composition, when
relative slippage occurs between the elements and pulleys during
the transmission of power due to clearance (space) between the
elements or when the core of the metal belt shifts between the
driving and driven pulleys, there is the danger of the lifespan of
the V-belt being reduced because of friction between the members.
There have been numerous proposals up to now for metal V-belts
which implemented different element shapes in order to reduce
relative slippage during the transmission of power and core
shifting. Japanese Laid-open Patent Publication No. 06-272737 (A)
is an example of this. This example is one in which the pulley
winding radius characteristics are improved and the core shifting
is reduced by means of forming the lower end portion from the
rocking edge of the element in a shape that becomes thinner a the
end on the tapered surface and the convex circular arc-shaped
surface.
[0006] Besides this, for example, Japanese Patent Publication No.
08-30517 (B) discloses a composition wherein the rocking edge is a
shape that combines a circular arc-shaped surface with a large
diameter and a circular arc-shaped surface with a small diameter
and the adjacent element pitch on the pulleys is made smaller to
reduce the relative slippage between the elements and the pulleys.
Another example is Japanese Laid-open Patent Publication No.
05-106691 (A) in which is disclosed a composition wherein two or
more rocking edges are provided on the element to allow the
essential length of the perimeter of the V-belt to change in
response to the winding radius of the pulley which in turn controls
the amount the core shifts to minimum levels during speed changes.
An even further example is Japanese Laid-open Patent Publication
No. 10-47438 (A) in which is disclosed a composition wherein
rocking edges are provided on both the front surface and the rear
surface of the element to allow the changes in the clearance
between elements due to the velocity ratio thereby controlling
slippage between the V-belt and the pulleys.
[0007] However, when determining the shape of the elements of the
above-mentioned metal V-belts, in particular, the radius of
curvature of the convex circular arc-shaped rocking edge, the
Hertzian stress acting on the rocking edge during the transmission
of power was taken into account. This Hertzian stress is a
parameter that affects the clearance between the elements and the
opposing pitching lifespan. If this is not taken into account,
there will be excessive clearance and the slippage between the
pulleys and elements will grow larger and in addition there is a
possibility that pitching caused by rough contact at the rocking
edge may reduce the lifespan of the elements.
SUMMARY OF THE INVENTION
[0008] The object of the present invention is to provide a metal
V-belt with a composition that can maintain a suitable clearance
between elements.
[0009] A further object of the present invention is to provide a
metal V-belt with a composition that sufficiently satisfies a
performance resistant to pitching.
[0010] The metal V-belt of the present invention comprises an
endless belt shaped metal ring member and a plurality of metal
element members supported along the metal ring member. This V-belt
transmits power between a drive pulley and a driven pulley. The
metal element members have a cross-sectional convex circular
arc-shaped rocking edge with an axis leaning against the opposing
front and rear metal element members along with having a convex
portion (for example, the male coupling 28 in the embodiment) and a
concave portion (for example, the female coupling 29 in the
embodiment) on the principal plane. By means of engaging the
adjacent metal element members together, the convex portion and the
concave portion can be lined up in a row at the front and rear on
the metal element members. An allowable value of a clearance (Ct)
between the total elements obtained as a sum of clearance (Cs)
between the elements during a no-load stop when this metal V-belt
is stretched between the drive pulley and the driven pulley and
clearance (Ch) between the elements occurring due to Hertzian
stress acting on the rocking edge of the metal element members
while the metal V-belt is transferring power is stipulated to a
value less than the protruding height (for example, height h of
male coupling 28 in the embodiment) of the convex portion.
[0011] Furthermore, in the present invention, the maximum Hertzian
stress (.sigma.hm) acting on the rocking edge while the metal
V-belt is transferring power is stipulated to a value less than the
allowable Hertzian stress (.sigma.ho) that satisfies the opposing
pitching lifespan of the metal element members. Namely, the radius
of curvature R of the rocking edge is set within a range that
satisfies R1.ltoreq.R.ltoreq.R2 for a minimum radius of curvature
R1 determined in correspondence with the maximum Hertzian stress
and a maximum radius of curvature R2 determined in correspondence
with an allowable value of clearance between the total
elements.
[0012] If a metal V-belt with this type of composition is provided,
the clearance between the elements is always maintained at a fixed
gap (less than the protruding height of the convex portion).
Therefore, friction between the pulleys and element can be reduced
along with improving the transmission efficiency of the power.
Further, the opposing pitching lifespan is always satisfied thereby
improving endurance reliability. Even further, even if external
disturbances, such as vibration, occur while the metal V-belt is
transferring power, the linkage between the elements will not
separate thereby eliminating an possibility of damage to the
male-female engagement portion.
[0013] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will become more fully understood from
the detailed description given herein below and the accompanying
drawings which are given by way of illustration only and thus are
not limitative of the present invention and wherein:
[0015] FIG. 1 is an outline view showing a power transmission
apparatus provided with the metal V-belt of the present
invention;
[0016] FIG. 2 is a side view showing an expanded view of the metal
V-belt of FIG. 1;
[0017] FIG. 3 is a front view seen from arrows III-III of FIG.
2;
[0018] FIG. 4 is a table showing clearance reduction values from a
natural toroidal state of the metal V-belt of an embodiment;
[0019] FIG. 5 is a graph showing results in a LOW endurance motor
of an embodiment;
[0020] FIG. 6 is a graph showing results in a TOP endurance motor
of an embodiment;
[0021] FIG. 7 is a graph showing results in a OD endurance motor of
an embodiment;
[0022] FIG. 8 is a side view showing an example of the composition
of conventional elements;
[0023] FIG. 9 is a front view showing an example of the composition
of conventional elements.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] FIG. 1 shows a power transmission apparatus provided with
the metal V-belt of the present invention. This power transmission
apparatus 1 is comprised by a drive belt 2 mounted to a drive shaft
2a, a driven pulley 3 mounted to a driven shift 3a, and a metal
V-belt 10 (hereinafter referred to as V-belt) stretched between
both pulleys 2, 3. Both of the pulleys 2, 3 can variably control
the pulley channel width and by means of variably controlling this
pulley channel width, the wrapping radius for both pulleys 2, 3 of
the V-belt 10 can be changed and the change gear ratio from the
drive shaft 2a to the driven shaft 3a changed in infinite
steps.
[0025] FIG. 2 shows an expanded view this V-belt 10 and FIG. 3 is a
view seen from arrows III-III of FIG. 2. As can be understood from
these figures, the V-belt 10 is comprised by successively mounting
a plurality of elements 20, 20 - - - along an endless belt shaped
metal ring 11. Further, the metal ring 11 is formed by layering a
few rings (for example, 12 rings) of thin meal rings.
[0026] As shown in FIG. 3, ring channels 21 are formed on the left
and right sides of each element 20 and a pair of left and right
metal rings 11 are fitted into these channels 21. Because of this,
the innermost peripheral surface of the metal rings 21 rub against
the lower side of a saddle surface 22. Further, as shown in FIG. 2,
each element 20 has a front surface 23 and a rear surface 24
parallel to each other (the front surface 23 and rear surface 24
form a principal plane) and the lower half of the front surface 23
forms a tapered surface 25 such that the thickness reduces towards
the rear surface 24 side. A radius of curvature R exists in the
boundary between the front surface 23 and the tapered surface 25
and a cross-sectional convex circular arc-shaped rocking edge 26 is
formed extending laterally against both the front surface 23 and
the tapered surface 25. The center of the radius of curvature R of
the rocking edge 26 is positioned downward away from the saddle
surface 22 by only t.
[0027] Each element 20 is allowed to make contact with the rear
surface 24 of the preceding element 20 opposite the rocking edge 26
allowing the element to lean forward and rearward as an axis. This
makes it possible for the V-belt 10 to wind on both pulleys 2, 3.
Further, a V side face 27 is formed on both the left and right
sides of the tapered surface 25. This V side face is supported on a
slanted surface 2b (or 3b) of the pulley 2 (or 3). By means of
changing the channel width of the pulley 2 (or 3), the elements 20
can be moved up and down which in turn allows the winding radius of
the V-belt 10 to be changed.
[0028] A cylindrical-shaped protruding male coupling 28 is formed
on the upper half portion of the front surface 23 of each element
20 and a round-shaped hole female coupling 29 is formed on the
upper half portion of the rear surface 24. Each element 20 arranged
and mounted on the V-belt 10 engages its respective male coupling
28 into the female coupling 29 of the preceding element 20 thereby
controlling the lateral movement arranged on the V-belt 10.
[0029] Next, the transmission of power from the drive pulley 2 in
the power transmission apparatus 1 to the driven pulley 3 will be
described based on FIG. 1. When the drive pulley 2 rotates, that
rotation force becomes a pressing force between the elements 20, 20
on the V-belt 10 and is transmitted. This is what drives the driven
pulley 3. The means to transmit this pressing force are elements
20, 20 . . . of the region P2.about.P1.about.P3.about.P4 from among
all the elements 20, 20 . . . on the V-belt 10 which reach from a
front position P2 located away from an outlet (P1 of FIG. 1) of the
drive pulley 2 to an outlet P4 of the driven pulley 3 passing
through an inlet P3 of the driven pulley 3. Therefore, regions
other than these, namely, elements 20, 20 . . . of the region
P4.about.P5.about.P2 reaching from the outlet P4 of the driven
pulley 3 to the position P2 passing through the inlet P5 of the
drive pulley 2 are in an advancing state and do not transmit the
pressing force.
[0030] From among the element region P2.about.P1.about.P3.about.P4
that transmits the pressing force, region P6.about.P4 from the
position P6 in front of outlet P4 of the driven pulley 3 to the
outlet P4 of the driven pulley 3 are regions which gradually
release the pressing force between the elements 20, 20. And even
further, the element 20 forcibly protrudes from the outlet P4 in
order for the pressing force to be quickly released from the
restriction caused by the pulley slanted surface 3b on the outlet
P4 of the driven pulley 3. Because of this, there is a good
possibility that the elements 20, 20 . . . in the region
P4.about.P7 from the outlet P4 to the location P7 at that point
will be separated from each other and therefore, there is a good
possibility that the clearance obtained between adjacent elements
20, 20 will be at the maximum in the region P4.about.P7. Moreover,
the region P6.about.P4 are approximately 30% of the region
P3.about.P4.
[0031] The region P2.about.P1 from among the above-mentioned
element region P2.about.P1.about.P3.about.P4 which transmit the
pressing force are region wherein the elements 20, 20 . . . which
have advanced are gradually prepared to transmit the pressing force
without transmitting the pressing force in the region
P4.about.P5.about.P2. Because of this, when the clearance between
elements which have the V-belt 10 is large, the relative slippage
between the element 20 in the region P2.about.P1 and the drive
pulley 2 grows larger with the generation of heat between the
elements 20, 20 . . . and the drive pulley 2 causing the
transmission efficiency of the power to worsen. Therefore, it is
preferable for the clearance between elements which have the V-belt
10 to be as small as possible. Also, region P2.about.P1 is normally
approximately 20%.about.40% of the region P5.about.P1.
[0032] In the V-belt 10 with this type composition, a
characteristic in the present invention is the way to set the
radius of curvature in the rocking edge 26 of the element 20. This
is described in the following.
[0033] The above-mentioned V-belt 10 has clearance between the
elements in a natural toroidal state. However, besides the common
elements 20 which have identical thickness' P, this clearance
between the elements can be freely set to any value by means of
using an adjustment element 20 that has a thickness slightly
smaller than these common elements 20. Generally, the clearance
between the elements is know to be at its maximum in a natural
toroidal state and is reduced from this value when the V-belt 10 is
wound around the pulleys 2, 3. This reduced clearance amount
differs depending on the pitch radius ratio of the wound pulleys 2,
3, in other words, the change gear ratio r (=pitch radius of driven
pulley 3/pitch radius of drive pulley 2) and when the change gear
ratio r is 1.0, it is at its minimum and grows larger as the change
gear ratio r moves away from 1.0. Namely, if change gear ratio r1,
r2 are 1.0<r1<r2, the reduced clearance amount for r2 will
become larger and if change gear ratios r3, r4 are 1.0>r3>r4,
the reduced clearance amount for r4 will become larger.
Furthermore, if change gear ratios r1, r3 are 1/r1=r3, both of the
reduced clearance amounts will become equal.
[0034] Hereupon, if the clearance between the elements in a natural
toroidal state (hereinafter referred to as initial clearance) is Co
and the reduced clearance amount when the pulleys 2, 3 are wound is
.DELTA.C, the clearance between the elements in this wound state an
be represented by Cs as shown below. The clearance between the
elements Cs in this pulley wound state is fixed by a geometric
shape and this is referred to as clearance Cs during a no-load stop
hereinafter as clearance between the elements during a no-load
stop.
Cs=Co-.DELTA.C (1)
[0035] The clearance between the elements of the V-belt 10 as
described above is preferably small. As understood from equation
(1), the reason the initial clearance Co can be brought close to
the clearance reduction value .DELTA.C is to make the clearance Cs
during a no-load stop as small as possible although the initial
clearance Co can be made to match the clearance reduction value
.DELTA.C in a change gear ratio ro wherein the clearance reduction
value grows to its maximum value in order that pulley tension is
not applied to the V-belt 10 at any change gear ratio r. By means
of setting the initial clearance Co in this manner, the clearance
Cs during a no-load stop can be reduced to a minimum in all change
gear ratios r. Further, it is only natural that the clearance Cs
during a no-load stop becomes zero (0) at change gear ratio ro
wherein the clearance reduction value grows to its maximum
value.
[0036] In contrast, during the transmission of power, (while V-belt
10 moves), Hertzian stress (contact stress) .sigma.h acts on each
rocking element 26 in the element region
P2.about.P1.about.P3.about.P4 that transmits the pressing force of
the above-mentioned elements 20, 20 - - - . Because of this, the
elements 20, 20 . . . region P2.about.P1.about.P3.about.P4 deform
due to compressive elasticity and the distance between the centers
of the adjacent elements 20, 20 compresses. Then the clearance
between the elements increases from the clearance Cs during a
no-load stop. The clearance between the elements of this increased
portion is obtained by means of finding the total sum of the
approach value of the distance between the centers of each of the
adjacent elements 20, 20 using each Hertzian stress .sigma.h value
acting on the elements 20, 20 located in the region
P2.about.P1.about.P3.about.P- 4. This increase in the clearance
between the elements is caused by Hertzian stress .sigma.h and
hereinafter is referred to as clearance Ch due to Hertzian
stress.
[0037] If the change gear ratios r of the wound pulleys 2, 3 is
different, the clearance Ch due to Hertzian stress will change the
load conditions (such as input rpms and input torque) expected to
be examined at each change gear ratio and because the pressing
force between the blocks will also become different following this,
the magnitude of the clearance Ch due to Hertzian stress will be
dependent on the change gear ratio r in like manner to the
clearance Cs during a no-load stop. Further, if the sum of the
clearance Cs during a no-load stop and the clearance Ch due to
Hertzian stress is total clearance Ct (=Cs+Ch), this total
clearance Ct will also be dependent on the change gear ratio r.
[0038] As shown in a subsequent embodiment, when the change gear
ratios r are identical and the radius of curvature R of the rocking
edge 26 is allowed to be changed, the clearance Cs during a no-load
stop and the clearance Ch due to Hertzian stress will tend to
increase following increases in the radius of curvature R. Because
of this, the total clearance Ct will also increase following
increases in the radius of curvature R.
[0039] As described above, while the V-belt 10 is transmitting
power, the adjacent elements 20, 20 separate from each other mainly
in regions P4.about.P7 and at this time, the maximum obtainable
clearance between the elements that can occur between adjacent
elements 20, 20 is total clearance Ct. In order to maintain the
alignment of each element 20 on the metal ring 11, as described
above, the adjacent elements 20, 20 must link with the coupling
rings 28, 29 and at a minimum both coupling rings 28, 29 must be
maintain in a state in which they do not come apart. Hereupon, if
the clearance between the adjacent elements 20, 20 increases and
the coupling rings 28, 29 become come apart, not only will the
alignment of the elements 20 on the metal ring 11 be put in
disorder but there will be the danger that the male coupling 28
will ride up onto the rear surface 22 of the preceding element 20
damaging the female couplings 29, 30. In order to prevent this, it
is preferable for the maximum obtainable clearance between the
elements that can occur between adjacent elements 20, 20, namely,
the total clearance Ct to always be made a value less than the
coupling height h (see FIG. 2). Therefore, an allowable value Cto
of the total clearance Ct is set to a value less than the coupling
height h and an upper limit value of the rocking edge radius of
curvature R is set to a value R2 that corresponds to the allowable
value Cto.
[0040] Further, this is also shown in a subsequent embodiment. When
the change gear ratios r are identical and the radius of curvature
R of the rocking edge 26 is allowed to be changed, the maximum
Hertzian stress .sigma.hm (maximum value of Hertzian stress
.sigma.h) acting on the rocking edge 26 of each element 20 grows
larger following reductions in the rocking edge radius of curvature
R. The Hertzian stress ah acting on the rocking edge 26 allows
pitching to occur on that rocking edge 26 and when the Hertzian
stress .sigma.h acting on the rocking edge is higher than a fixed
value, there is the danger that the V-belt 10 may experience
reductions in its lifespan due to the pitching. Because of this,
the maximum Hertzian stress .sigma.hm acting on the rocking edge 26
must be less than an upper limit value .sigma.ho of the Hertzian
stress that satisfies the opposing pitching lifespan in order that
reductions in the lifespan of the V-belt 10 caused by at least
pitching does not occur. Therefore, the allowable value .sigma.ho
of the maximum Hertzian stress .sigma.hm is set to a value smaller
than the upper limit value .sigma.ho of the Hertzian stress that
satisfies the above-mentioned opposing pitching lifespan and the
lower limit value of the rocking edge radius of curvature R is set
to a value R1 that corresponds to the allowable value
.sigma.hmo.
[0041] In this manner, if the rocking edge radius of curvature R is
within the range R1.ltoreq.R.ltoreq.R2 using lower limit value R1
and upper limit value R2, the clearance between the elements will
always be maintained at a fixed gap (less than height h of the
female coupling 29). Therefore, friction between the metal ring 11
and the element 20 can be reduced along with relative slippage
between the metal ring 11 and the element 20 made smaller thereby
improving the transmission efficiency of the power. Further, the
opposing pitching lifespan is always satisfied thereby improving
endurance reliability. Even further, even if external disturbances,
such as vibration, occur while the V-belt 10 is transferring power,
the linkage between the adjacent elements 20, 20 will not separate
thereby eliminating an possibility of damage to the male-female
couplings 29, 30.
[0042] Next, as shown in the embodiments implemented by the
inventors, the procedure to set the range of the rocking edge
radius of curvature R will be described in detail. In this
embodiment, the specifications of the metal V-belt 10 were as
follows.
[0043] Element thickness P: 1.5 mm (element thickness to adjust
clearance is slightly smaller than this)
[0044] Start position t of the rocking edge radius of curvature R:
1.0 mm
[0045] Maximum inner peripheral length of the metal ring 11: 656
mm
[0046] Distance between axis of pulleys 2, 3: 155 mm
[0047] To start, changes to the rocking edge radius of curvature R
of the clearance reduction value .DELTA.C when the metal V-belt 10
of the above-mentioned specifications is stretched across the
pulleys 2, 3 were found for each change gear ratio r. There were
six types of rocking edge radius of curvature R, 4 mm, 6 mm, 8 mm,
10 mm, 12 mm and 14 mm and eight types of change gear ratios r 0.5,
61, 0.8, 1.0, 1.25, 1.64, 2. And 2.5. The table in FIG. 4 shows
these results.
[0048] As understood from the table in FIG. 4, the clearance
reduction value .DELTA.C is at its maximum at change gear ratio
r=2.5 for any rocking edge radius of curvature R. Therefore, in
this embodiment, the value of the initial clearance for each
rocking edge radius of curvature R is set such that is becomes
equal to the clearance reduction value .DELTA.C at change gear
ratio ro=2.5 (because of this, the clearance Cs during a no-load
stop at change gear ratio ro=2.5 is zero (0) for every radius of
curvature R).
[0049] After carrying out these settings, the clearance between the
elements and the maximum Hertzian stress .sigma.hm for the
following types of endurance motors were found.
[0050] {circle over (1)} LOW: change gear ratio=2.5, input
torque=14.5 kgf-m, input rpm=5500 rpm
[0051] {circle over (2)} TOP: change gear ratio=0.61, input
torque=14.3 kgf-m, input rpm=6000 rpm
[0052] {circle over (3)} OD (overdrive): change gear ratio=0.5,
input torque=14.5 kgf-m, input rpm=4000 rpm
[0053] The tables in FIG. 5 to FIG. 7 shows these results. These
tables show the clearance Cs during a no-load stop in the clearance
between elements, the clearance Ch occurring due to Hertzian
stress, and the total clearance Ct, respectively. The rocking edge
radius of curvature R (mm) is the horizontal axis on each of these
tables. The clearance between elements (mm) and the maximum
Hertzian stress .sigma.hm (kgf/mm2) is the vertical axis.
[0054] Based on FIG. 5 to FIG. 7, the allowable clearance value Cto
of the total clearance is set to a male coupling height h=0.7 mm
and the allowable value .sigma.hmo of the maximum Hertzian stress
is set to the upper limit value .sigma.ho of the Hertzian stress of
the element 20=120 kgf/mm2 in this embodiment and the lower limit
value R1 and the upper limit value R2 of the rocking edge radius of
curvature R were found. As a result, in {circle over (1)} LOW
endurance motor R1=6 mm (R2 was not found), in {circle over (2)}
TOP endurance motor R1=9 mm, R2=14 mm, and in {circle over (3)} OD
endurance motor R1=8 mm (R2 was not found). From these results, the
lower limit value R1 of the rocking edge radius of curvature R that
satisfies conditions in any of the endurance motors is R1=9 mm and
the upper limit value R2 is R2=14 mm. Therefore, the range of the
rocking edge radius of curvature R in this embodiment is set to be
9.ltoreq.R.ltoreq.14 (mm).
[0055] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
RELATED APPLICATIONS
[0056] This application claims the priority of Japanese Patent
Application No. 10-244936 filed on Aug. 31, 1998, which is
incorporated herein by reference.
* * * * *