Metal V-belt

Details Metal V-belt Metal V-belt

1999-06-23

2001-04-17

Marmor, Charles A (Department: 3681)

Endless belt power transmission systems or components

Friction drive belt

Including plural interconnected members each having a drive...

C474S201000

Reexamination Certificate

active

06217472

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a metal V-belt used for the transmission of power in a V-belt continuously variable transmission or the like, and more particularly to a metal V-belt characterized in the configuration of the endless belt-form metal ring member that constitutes this metal V-belt.
BACKGROUND OF THE INVENTION
Metal V-belts such as this have been known for some time, and are disclosed, for example, in Japanese Utility Model Laid-Open No. 62-131143, Japanese Patent Laid-Open No. 2-225840, and Japanese Patent Laid-Open No. 7-12177. These metal V-belts used in the past comprise an endless belt-form metal ring member and numerous metal element members (also called metal links) supported along this metal ring member, and are looped between a drive pulley and a driven pulley so as to transmit power. These two pulleys are designed so that the width of the V-groove thereof can be varied, and are designed so that the loop radius of the V-belt can be varied and the gear ratio continuously varied by varying this V-groove width.
When power is transmitted between the two pulleys by a metal V-belt such as this, the metal element members are pushed upon while the power is transmitted, so that the power is transmitted by the compression force acting on the metal element members. At this time a tensile force acts on the metal ring member that ties the numerous metal element members together in a ring, and flexural stress that varies with the rotation also acts on this metal ring member while the V-belt is looped and rotating between the two pulleys, with the tension and flexion repeatedly acting according to the rotational period of the metal V-belt between the two pulleys.
It is therefore necessary to take into account the tensile and flexural stress that thus repeatedly act on the metal ring member, and to optimize the material, shape, and so on thereof so that the strength and service life will be satisfactory with respect to this repeated stress. The metal ring member generally comprises a plurality of superposed, thin, endless belt-form metal ring sheets, and since power is transmitted in a state in which the innermost metal ring sheet is in contact with the metal element members, it is necessary at the design stage thereof to take into account the coefficient of friction between the metal ring sheets themselves and the coefficient of friction between the metal ring sheets and the metal elements.
Flexural stress can be unequivocally determined by the loop radius of the two pulleys, but tensile stress varies with each metal ring sheet depending on the above-mentioned coefficient of friction. In general, the coefficient of friction between the metal ring sheets (ring-ring coefficient of friction) is smaller than the coefficient of friction between the metal ring sheets and the (saddle surfaces of the) metal elements (ring-element coefficient of friction), so the change in tension is greatest at the innermost metal ring sheet, and when all of the metal ring sheets have the same thickness, the change in tensile stress is greatest for the innermost metal ring sheet. In the past, the metal rings comprised a plurality of metal ring sheets of the same material and the same thickness superposed in the radial direction, so the stress conditions were most severe at the innermost metal ring sheet for the above reason, and the innermost metal ring sheet was the most problematic in terms of strength and service life.
SUMMARY OF THE INVENTION
The present invention was conceived in light of the foregoing, and an object thereof is to extend the total service life as much as possible and obtain a metal V-belt with a long service life by decreasing the thickness of, and thereby reducing flexural stress in, the innermost metal ring sheet where the tensile stress conditions are harshest.
In order to achieve this object, the present invention is a metal V-belt for transmitting power, looped between a drive pulley and a driven pulley, and comprising an endless belt-form metal ring member ( such as the metal ring
31
in the embodiment) and numerous metal element members (such as metal elements
32
in the embodiment) supported along this metal ring member, wherein the metal ring member comprises a plurality of thin, endless belt-form metal ring sheets (such as metal ring sheets
33
(
1
) to
33
(n) in the embodiment) superposed in the radial direction, and of these plurality of metal ring sheets, the thickness of the innermost metal ring sheet ( such as metal ring sheet
33
(
1
) in the embodiment) is made less than the thickness of the other metal ring sheets ( such as metal ring sheets
33
(
2
) to
33
(n) in the embodiment).
Furthermore, it is preferable for the thickness of the innermost metal ring sheet to be set on the basis of the ratio of the coefficient of friction between the innermost metal ring sheet and the metal element members to the coefficient of friction between the other metal ring sheets.
There is less flexural stress in the innermost metal ring sheet when this metal ring sheet is thus made thinner. Still, because of the large coefficient of friction between the innermost metal ring sheet and the metal elements as mentioned above, it must be remembered that making the innermost metal ring sheet thinner increases the change in tensile stress. In the present invention, the optimal thickness is set by taking into consideration the increase in tensile stress and the decrease in flexural stress resulting from a reduction in the thickness of the innermost metal ring sheet. Flexural stress simply decreases according to changes in thickness, but the increase in tensile stress varies according to the coefficient of friction between the innermost metal ring sheet and the metal element member (ring-element coefficient of friction) and the coefficient of friction between the other metal ring sheets (ring-ring coefficient of friction), so the optimal thickness is set on the basis of these two coefficients of friction.
In this case, it is preferable for the repeated stress amplitude &sgr; a and the mean stress &sgr; m applied to the innermost metal ring sheet when the metal V-belt is looped between the drive pulley and the driven pulley to transmit power to be taken into account, and for the thickness of the innermost metal ring sheet to be set so as to maximize the fatigue life of the innermost metal ring sheet when repeatedly subjected to the stress amplitude &sgr; a and the mean stress &sgr; m. The stress amplitude &sgr; a and the mean stress &sgr; m here are both a combination of flexural stress and tensile stress, and the thickness setting can be performed under optimal conditions combining both the reduction in flexural stress and the increase in tensile stress resulting from a reduced metal ring sheet thickness.
It is preferable for the thickness of the innermost metal ring sheet to be set so as to maximize the fatigue life of the innermost metal ring sheet, as long as the fatigue life of the innermost metal ring sheet, produced by the repeated load acting thereon when the V-belt is looped between the drive pulley and the driven pulley to transmit power, is less than the fatigue life of the other metal ring sheets. This fatigue life can be extended by making the innermost metal ring sheet thinner, but depending on the coefficient of friction conditions, the fatigue life of the innermost metal ring sheet may be greater than the fatigue life of the other metal ring sheets, in which case it is best to set the thickness so as to maximize the fatigue life of the innermost metal ring sheet while not exceeding the fatigue life of the other metal ring sheets. This allows the thickness of all of the metal ring sheets to be optimized and the fatigue life of the metal V-belt as a whole to be maximized.
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 gi

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