Belt for continuously variable transmission

Details Belt for continuously variable transmission Belt for continuously variable transmission

2000-09-08

2003-09-30

Charles, Marcus (Department: 3682)

Endless belt power transmission systems or components

Friction drive belt

Including plural interconnected members each having a drive...

C474S201000

Reexamination Certificate

active

06626783

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a belt for a continuously variable transmission which includes a metal ring assembly comprised of a plurality of endless metal rings laminated one upon another, and a plurality of metal elements each having a ring slot into which the metal ring assembly is fitted, and which is wound around a drive pulley and a driven pulley to transmit a driving force between the drive pulley and the driven pulley.
2. Description of the Related Art
There is such a belt for the continuously variable transmission, which is known from Japanese Patent Application Laid-open No. 2-225840, and in which the gravity center of the metal element is positioned in the vicinity of, or radially outside (above), a rocking edge in order to eliminate the gap formed between the adjacent metal elements in a chord section extending from the driven pulley to the drive pulley, and to bring the metal elements into engagement with the drive pulley in a correct attitude in which they are not inclined forwardly or rearwardly.
The conventionally known belt is intended to stabilize the attitude of the metal element in the chord section extending from the driven pulley to the drive pulley, but does not have an effect of stabilizing the attitude of the metal element which is in engagement with the pulley.
More specifically, if the metal element engaged with the pulley is pitched forwardly or rearwardly from a radial direction about the axis of rotation of the pulley, there is a possibility that the state of the metal element engaged with the pulley will become abnormal, whereby the attitude of the metal element will not only become unstable, but also front and rear edges of the saddle surface of the metal element will be brought into local contact with the lower surface of the metal ring assembly to exert an adverse influence upon the durability of the metal ring assembly. The direction and magnitude of the pitching of the metal element are determined depending on a tangent frictional force FV received from the surface of contact with the pulley by the metal element and an urging force E provided between the respective metal elements. The tendency of inclination of the metal element is particularly conspicuous in an exit region of the driven pulley. The reason will be described below.
It is known that the tangent frictional force FV received by the metal element
32
(see
FIG. 3
) from the drive pulley
6
or the driven pulley
11
is large in the exit region of the drive pulley
6
or the driven pulley
11
, as shown in
FIGS. 7A and 7B
, and assumes a value about four times a value provided when the tangent frictional force FV has been averagely distributed over the entire wound region of the pulley
6
or
11
by a reason that the pulley
6
or
11
has been deformed, resulting in the concentration of an axial thrust, or for another reason. As is apparent from
FIG. 3
, the tangent frictional force FV is applied to the metal element
32
so as to fall the metal element forwardly in the direction of movement about the swinging center
44
.
In addition, as shown in
FIG. 7B
, the urging force E provided between the metal elements
32
and inhibiting the inclination of the metal element
32
assumes a large value in the exit region (position b) of the drive pulley
6
, but is 0 (zero) in the exit region (positioned) of the driven pulley
11
. As is apparent from
FIG. 3
, a radial frictional force E
1
is applied to the front and rear surfaces of the metal element
32
by the urging force E so as to fall the metal element
32
rearwardly in the direction of movement about the swinging center
44
; namely, so as to oppose a moment generated by the tangent frictional force FV. Therefore, in a position where the tangent frictional force FV inclining the metal element
32
forwardly in the direction of movement is largest and the urging force E inhibiting the inclination of the metal elements
32
is 0 (zero), i.e., in the exit region (the position d) of the driven pulley
11
, the metal element
32
is liable to be inclined to the largest extent.
The reason why the peak value of the tangent frictional force FV received by the metal element
32
from the driven pulley
11
reaches about four times the value provided when the tangent frictional force FV has been averagely distributed over the entire wound region of the pulley
11
, is considered as follows:
FIG. 8
shows the results of the measurement of the tangent frictional force FV and the urging force E between the metal elements
32
to determine how they are varied in accordance with a variation in rotational angle &thgr;. Points a, e, b, c, f and d on the axis of the abscissas correspond to the positions shown in
FIG. 7B
, respectively. As shown in
FIGS. 9A and 9B
, a sensor for measuring the urging force E between the metal elements
32
comprises an assembly which includes a beam formed into a U-shape and a strain gauge attached to an inner surface of the beam and which is mounted in a recess defined in the main surface of the metal element
32
. The sensor measures the urging force E, based on the flexure of the beam produced by the urging force E. As shown in
FIG. 10
, a sensor for measuring the tangent frictional force FV of the metal element
32
comprises strain gauges attached in a pair of recesses defined in laterally opposite sides of an element body of the metal element
32
, and measures the tangent frictional force FV based on the flexure of the element body produced by the tangent frictional force FV. It should be noted that the element body is flexed by an axial thrust transmitted from the V-face of the pulley to the metal element
32
and hence, an output from the strain gauge includes a component provided by the tangent frictional force FV and a component (a constant value) provided by the axial thrust transmitted from the V-face of the pulley.
As is apparent from
FIGS. 7 and 8
, the tangent frictional force FV assumes a peak value in the position in the exit region of the driven pulley
11
, and the urging force E assumes the maximum value in the position f (point P) short of the position d. The urging force between the metal elements
32
is generated by the tangent frictional force FV received by the metal elements
32
from the pulley, and a rate of variation in urging force E is proportional to the tangent frictional force FV. Namely, an equation, dE/d&thgr;=k * FV is established, wherein &thgr; represents a rotational angle of the pulley, and k is a constant.
In
FIG. 8
, when the urging force E assumes the maximum value at the point P, dE/d&thgr;=0 is established and hence, the tangent frictional force FV is equal to 0 (zero) at the point P. As described above, the graph of the tangent frictional force FV in
FIG. 8
includes the component provided by the tangent frictional force FV and the component provided by the axial thrust transmitted from the V-face of the pulley, but a substantial tangent frictional force FV resulting from the elimination of the component provided by the axial thrust transmitted from the V-face of the pulley can be detected by determining a point on the axis of the abscissas at which the tangent frictional force FV is equal to 0 (zero) from the point P at which dE/d&thgr; is equal to 0 (zero).
The tangent frictional force FV assuming 0 (zero) at the point f reaches a peak value A
MAX
at the point d corresponding to the exit of the driven pulley
11
, but an integration value of tangent frictional force FV between the points f and d corresponds to one half of an area (A
MAX
* L
1
) of a triangle having a base provided by a distance L
1
between the points f and d and a height provided by the peak value A
MAX
(see an obliquely-lined region shown in FIG.
8
). On the other hand, the tangent frictional force FV is distributed uniformly in a region between the points c and d, which is a wound region of the driven pulley
11
. If it is supposed that an average value of the tangent frictional force FV is A
AVE
, an integr

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