Belt for non-stage transmissions

Details Belt for non-stage transmissions Belt for non-stage transmissions

2002-01-15

2004-06-29

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

06755760

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a belt for a continuously variable transmission, which comprises a metal ring assembly comprising a plurality of endless metal rings laminated one on another, and a large number of metal elements each having a ring slot into which the metal ring assembly is fitted, the belt being wound around a drive pulley and a driven pulley to transmit a driving force between both of the pulleys.
BACKGROUND ART
There is an invention relating to such a belt for a continuously variable transmission, which is conventionally known from Japanese Patent Application Laid-open No.7-12177, and in which in order to inhibit the rolling of metal elements supported on a pair of metal ring assemblies to smoothly engage the metal elements in pulleys, a vertical (in a direction of thickness of the belt) clearance in each of the metal ring assemblies within a ring slot in a metal element (a difference between a groove width of the ring slot and a thickness of the metal ring assembly) is defined.
FIG. 11
shows a cross section of the belt for the continuously variable transmission described in the above-described Japanese Patent Application Laid-open No.7-12177. In this belt, metal ring assemblies
03
,
03
are engaged in a pair of left and right ring slots
02
,
02
in a metal element
01
. When the metal element
01
is not rolled, lower surfaces of the metal ring assemblies
03
,
03
are in contact with saddle surfaces
04
,
04
, and a clearance B is established between upper surfaces of the metal ring assemblies
03
,
03
and lower ear surfaces
05
,
05
. When the metal element
01
has been rolled in a direction of an arrow a in
FIG. 11
, the lower surface of one of the metal ring assemblies
03
is brought into contact with the saddle surface
04
at a point b, and an upper surface of the other metal ring assembly
03
is brought into contact with the lower ear surface
05
at a point c. By setting the clearance B so as to establish an expression, tan
−
B/A<1° wherein A represents a distance between the points b and c, it can be prevented that when the metal element
01
has been rolled at least at 1°, the pair of metal ring assemblies
03
,
03
are brought into contact with the saddle surface
04
and the lower ear surface
05
at the points b and c, whereby the metal element
01
is further rolled by a reaction force resulting from such contact.
The belt described in the above-described Japanese Patent Application Laid-open No.7-12177 is designed, so that the rolling of the metal element is inhibited. However, it is known that the clearance between the upper surface of the metal ring assembly and the lower ear surface also exerts a large influence to the durability of the metal ring assembly, when the metal element has been pitched. More specifically, when the metal element has been pitched, an edge of the lower ear surface is brought into contact with the upper surface of the metal ring assembly to generate a stress at such contact portion, thereby reducing the durability of the metal ring assembly. The pitching of the metal element occurs in the vicinity of an exit of a driven pulley by the following reason:
When the metal element
32
supported with the ring slots
35
,
35
fitted over the metal ring assemblies
31
,
31
has been inclined forwards in a direction of movement, as shown in
FIG. 3
, the following problem is encountered: Front ends of the lower ear surfaces
45
,
45
forming upper edges of the ring slots
35
,
35
in the direction of movement are brought into contact with the upper surfaces of the metal ring assemblies
31
,
31
(see a mark ◯ in
FIG. 3
) and hence, a large hertz stress is generated at such contact portion to exert an adverse influence to the durability of the metal ring assemblies
31
,
31
. The forward inclination of the metal element
32
in the direction of movement is generated by a tangent frictional force F received by the metal element
32
at its surface of contact with the pulley and by an urging force E between the metal elements
32
. Such a tendency is particularly remarkable at an exit area of the driven pulley (see FIG.
10
). The reason will be described below.
In
FIG. 3
, a moment generated in the direction of an arrow M by the tangent frictional force F acts to bring down the metal element
32
forwards in the direction of movement about the swinging center C. On the other hand, a radial (vertical) frictional force &mgr;E generated by the urging force E between the metal elements
32
generates a moment in the direction opposite from the arrow M in the metal element
32
and acts to bring down the metal element
32
backwards in the direction of movement about the swinging center C.
It is known that the tangent frictional force F received by the metal element
32
from the drive pulley
6
or the driven pulley
11
is large in the exit area of the drive pulley
6
or the driven pulley
11
, as shown in
FIG. 9A
, and the value of such tangent frictional force F reaches four times a value provided when it is supposed that the tangent frictional force F has been averagely distributed over the entire winding region of the pulley
6
or
11
, by reason that the pulley
6
or
11
is deformed, resulting in an axial thrust concentrated thereon, or by another reason. In addition, as shown in
FIG. 9B
, the urging force E between the metal elements
32
has a large value in the exit area of the drive pulley
6
, but assumes zero in the exit area of the driven pulley
11
. Therefore, the metal element
32
is most liable to be inclined forwards in the direction of movement in a position where the tangent frictional force F acting to incline the metal element
32
forwards in the direction of movement assumes a maximum value and the urging force E acting to inhibit the forward inclination of the metal element
32
in the direction of movement assumes zero, i.e., in the exit area of the driven pulley
11
.
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 a power transmitting efficiency, while preventing a reduction in durability of the metal ring assembly due to the pitching of the metal element.
To achieve the above object, according to the present invention, there is provided a belt for a continuously variable transmission, which comprises a metal ring assembly comprising a plurality of endless metal rings laminated one on another, and a large number of metal elements each having a ring slot into which the metal ring assembly is fitted, the belt being wound around a drive pulley and a driven pulley to transmit a driving force between both of the pulleys, each of the metal elements having a projection and a recess provided on front and rear surfaces thereof for engaging with preceding and succeeding ones of the metal elements, respectively, characterized in that when the size of a first vertical clearance between the projection and the recess of the metal element is represented by CL
NH
; the size of a second vertical clearance in the metal ring assembly within the ring slot is represented by CLy; a thickness of the metal ring assembly is represented by T
L
; and a vertical opening of the ring slot is represented by D, the following expression is established:
(CL
NH
/T
L
)+1<D/T
L
<(0.86
mm/T
L
)+1
With the above arrangement, the second vertical clearance CLy in the metal ring assembly within the ring slot is sized to be larger than the first vertical clearance CL
NH
between the projection and the recess of the metal element. Therefore, when the metal element has been pitched, the first clearance CL
NH
is first distinguished, whereby a further increase in pitch angle is inhibited, and the second clearance CLy is prevented from being distinguished. As a result, the upper surface of the metal ring assembly is prevented from being brought into contact with an upper edge of the ring slot to avoid a reduction in durability of the metal ring assem

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