V-belt pulley and variator

Details V-belt pulley and variator V-belt pulley and variator

1991-01-22

1992-07-07

Bui, Thuy M.

Endless belt power transmission systems or components

Pulley with belt-receiving groove formed by drive faces on...

F16H 5500

Patent

active

051278820

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention concerns transmissions having a variable ratio and being adjustable or automatically self-adjusting by means of pulleys consisting of sheaves being axially movable to each other and contacting on flanks of a V-belt or a like flexible link transmitting the power. The objects of the invention are pulleys and variators including them.


BACKGROUND OF THE INVENTION

The basis of the invention is an observation that power losses between the belt and the pulleys are mainly caused by lateral clearances and resiliences of the sheaves and belt dominating in relation to the bearing losses. For this reason the V-belt variators have generally a clearly lower efficiency rate than non-variable transmissions.
The basic idea of the invention is to modify the bearings of the sheaves by such a way, that the sheaves are not parallel when they are non-loaded or the belt is missing between them, but so inclined to each other that bending load caused by the belt makes them approximately parallel.
In itself it is not a new idea to make the sheave halves of a variable pulley non-parallel. It is known for example in the patent publications U.S. Pat. No. 3757594 (F 16 H 55/52) and G. 2041116 A (F 16 H 9/12).


SUMMARY OF THE INVENTION

The solution according to this invention is deviating from both devices mentioned afore by such a way that the distance of the contact rings on the sheaves is not smallest at the middle point of the touching area, but deviates from it approximately 45.degree. to the direction of rotation in the driven pulley and to the opposite direction in the driving pulley.
This improvement, which seems little and easy to be found, when valued afterwards, is however important, since without it no effect can be born reducing losses of the power and improving the efficiency.
The pulleys made according to the prior known inventions are functioning right only without loading torque moment. When the belt is loaded, the problems caused by its wedging and jamming can become even worse than in pulleys, where the sheaves are parallel before loading.
Particularly when the V-belt is wide or else laterally compressible the divergence of the sheaves shall be greater than required to compensate only the clearances and resiliences. In other words the distance between the sheaves shall be greatest approximately at the points, where the belt leaves the driving pulley and comes onto the driven pulley.
The sufficient total divergence is 0,1 . . . 0,4 grades or 0,0017 . . . 0,007 radians and the main means to accomplish it is to make the radial bearings eccentric and substitute the axial bearings partly or fully by rollers pushing and rolling against the rear sides of the sheaves. More in detail the characteristic features of the invention are discussed hereinbelow.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in the following with the aid of examples referring to the drawing attached, in which:
FIG. 1 presents in rear view a longitudinal section of a driving pulley of a bicycle variator according to the invention.
FIG. 2 presents a section of such a driving pulley, where the axial force pressing the sheaves together is produced as a sum effect of a notched cup spring, a multiple-end ball screw and a roller pressing on the outer rim of the cup spring.
FIG. 3 presents in cross view the driving pulley as described afore and a quarter of the notched cup spring, which can be similar also in the construction as presented in FIG. 1.
FIG. 4 presents schematically a V-belt variator, where the divergence of the sheaves is accomplished by support rollers substituting for the axial bearings.
FIG. 5 presents schematically a V-belt variator, where the support rollers are flat disks pressed radially between the rear sides of the sheaves and the particular supporting rings.
FIG. 6 presents an arrangement having less friction as before, where a wedge shaped ring is pressed between two conical surfaces each by means of two cylindrical support rollers.
FIG. 7 presents a construction, which is mo

REFERENCES:
patent: 3757594 (1973-09-01), Kumm

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