Belt for continuously variable transmission

Details Belt for continuously variable transmission Belt for continuously variable transmission

2000-06-22

2001-12-25

Bucci, David A. (Department: 3682)

Endless belt power transmission systems or components

Friction drive belt

Including plural interconnected members each having a drive...

C474S244000, C474S201000

Reexamination Certificate

active

06332854

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a belt for a continuously variable transmission, including a large number of metal elements supported on metal ring assemblies each of which is comprised of a plurality of endless metal rings laminated one on another.
BACKGROUND ART
As shown in
FIGS. 2 and 3
, a pair of main surfaces
38
and
39
extending perpendicular to a direction of movement and parallel to each other are provided on front and rear sides of a metal element
32
in the direction of movement, and a slope
41
is formed radially inside the main surface
38
on the front side in the direction of movement so as to be continuous with the latter. A pair of adjacent ones of the metal elements
32
can be pitched relative to each other around a rocking edge
40
extending between the main surface
38
and the slope
41
. Therefore, as shown in
FIG. 4
, when the metal elements
32
are moved from a drive pulley
6
to a driven pulley
11
, the main surfaces
38
and
39
of the adjacent ones of the metal elements
32
are placed in abutment against each other to transmit a driving force. When the metal elements
32
are in a state wound around the drive pulley
6
or the driven pulley
11
, the interference of the metal elements
32
with each other can be avoided by the pitching around the rocking edge
40
.
The metal elements
32
of the belt for the continuously variable transmission perform a rectilinear translating movement in a chord portion of the belt between the drive pulley
6
and the driven pulley
11
and hence, the moving speeds of various portions of the metal element
32
are the same as one another. However, in a state in which the metal elements
32
are wound around the drive pulley
6
and the driven pulley
11
, the metal elements
32
perform a rotating movement about rotational axes of the drive pulley
6
and the driven pulley
11
and hence, the moving speed of a radially outer portion of the metal element
32
is larger than that of a radially inner portion of the metal element
32
.
At this time, the metal elements
32
wound around the pulleys
6
and
11
are brought into abutment against each other at the rocking edge
40
. Therefore, the speed of the rocking edge
40
of each of the metal elements
32
wound around the pulleys
6
and
11
(the pitch circular speed) is equal to the speed of the various portions of the metal elements
32
performing the rectilinear translating movement in the chord portion. Namely, the speed of the rocking edge
40
of the metal elements
32
at belt portions wound around the pulleys
6
and
11
and the speed of the rocking edge
40
of the metal elements
32
at belt portions which are not wound around the pulleys
6
and
11
(i.e., the chord portion), are the same as each other. Therefore, in the state in which the metal elements
32
are wound around the pulleys
6
and
11
, the speed of the radially outer portion of the metal element
32
than the rocking edge
40
is larger than the speed of the rocking edge
40
, and the speed of the radially inner portion of the metal element
32
than the rocking edge
40
is smaller than the speed of the rocking edge
40
.
Now, when the metal elements
32
lie in the chord portion between the drive pulley
6
and the driven pulley
11
to transmit the driving force, the main surfaces
38
and
39
of adjacent ones of the metal elements
32
are brought into close contact with each other and thus are prevented from being inclined. However, when the metal elements
32
lie in the chord portion between the driven pulley
11
and the drive pulley
6
to transmit no driving force, a small gap is produced between the adjacent ones of the metal elements
32
and hence, in a portion A in
FIG. 4
, the metal elements
32
may be meshed with the drive pulley
6
while remaining inclined in the direction of movement (with the pitching remaining occurred) in some cases. If the metal elements
32
are meshed with the drive pulley
6
while remaining inclined in the direction of movement, a movement for dissolving the pitching of the metal elements
32
and compacting the gap between the metal elements occurs in the chord portion near an outlet of the drive pulley
6
for resisting against an urging force acting between the elements and hence, the following problems arise: the wearing of the metal elements
32
and the pulley
6
is increased, and the power transmitting efficiency is reduced.
Therefore, a belt for a continuously variable transmission described in Japanese Patent Application Laid-open No.2-225840 is designed so that the center of gravity G of the metal element
32
is located in the vicinity of the rocking edge
40
or radially outside the rocking edge
40
, thereby preventing a gap from being produced between the metal elements
32
in the chord portion between the driven pulley
11
and the drive pulley
6
, so that the metal elements
32
in close contact with one another are smoothly meshed with the drive pulley
6
.
More specifically, the speed of the center of gravity G of the metal elements
32
in the chord portion between the pulleys
6
and
11
is equal to the pitch circular speed, but the speed of the center of gravity G of the metal elements
32
wound around the pulleys
6
and
11
is larger than the pitch circular speed, if the center of gravity G lies radially outside the rocking edge
40
. In other words, the kinetic energy of the metal elements
32
leaving the driven pulley
11
is larger than the kinetic energy of the metal elements
32
lying in the chord portion. The metal elements
32
lying in the chord portion are urged forwards (toward the drive pulley
6
) by a difference between the kinetic energies and are smoothly meshed with the drive pulley
6
in a state placed in close contact with one another.
In the prior art described above, the center of gravity G of the metal element
32
is allowed to lie radially inside the rocking edge
40
even at a distance of 0.5 mm from the latter. However, if the center of gravity G lies radially inside the rocking edge
40
, the kinetic energy of the metal element
32
leaving the driven pulley
11
becomes smaller than that of a metal element
32
lying in the chord portion and hence, the metal elements
32
lying in the chord portion cannot be meshed with the drive pulley
6
without being pitched in a state placed in close contact with one another. Therefore, it is required that the center of gravity G of the metal element
32
should lie radially outside the rocking edge
40
. In other words, it is required that a relation Vr<Vg should be established when Vr represents a speed of the rocking edge
40
at an instant when the metal element
32
leaves the driven pulley
11
, and Vg represents a speed of the center of gravity G of the metal element
32
.
Additionally, if the center of gravity G of the metal element
32
moves radially outside too away from the rocking edge
40
, the kinetic energy of the metal elements
32
which have left the driven pulley
11
becomes excessive and the metal elements
32
rotate so as to fall forwards, as shown in FIG.
10
. As a result, the energy is expended by the interference between a metal ring assembly
31
and a lower portion of an ear portion
36
, or by the interference of coupling, thereby resulting in loss of a force for delivering the metal elements
32
forwards. Therefore, there is a possibility that the metal elements
32
could not be meshed with the drive pulley
6
in the state free of the pitching.
DISCLOSURE OF THE INVENTION
The present invention has been accomplished with the above circumstances in view, and it is an object of the present invention to ensure that the center of gravity of the metal elements is defined correctly in a proper range, whereby the metal elements lying in the chord portion are meshed with the drive pulley in the state free of the pitching.
To achieve the above object, according to the present invention, there is provided a belt for a continuously variable transmission, comprising a large number

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