Automatic mechanical transmission apparatus with continuous variation of the transmission ratio from an infinite ratio up to a ratio less then 1/1

This invention relates to an automatic mechanical transmission apparatus with continuous variation of the transmission ratio from an infinite ratio up to a ratio less than 1/1, of the type employing centrifugal forces, comprising at least one driven plate bearing at least one continuous circular track, eccentric with respect to the common axis of the driving and driven shafts, and rollers which roll inside the circular track, being mounted to rotate about respective longitudinal axes, each of these rollers being borne by a rod connected to a pivot pin on the driving hub, characterized in that each rod bearing a roller is articulated on the outer part of a weight which is itself articulated on the hub fast with the driving shaft.

FIELD OF THE INVENTION 
The present invention relates to an automatic mechanical transmission 
apparatus with continuous variation of the transmission ratio from an 
infinite ratio up to a ratio less than 1/1, of the type employing 
centrifugal forces. 
BACKGROUND OF THE INVENTION 
Such a known apparatus, as described in Patent EP-A 0 172 557, comprises a 
driving shaft and a driven shaft, which are coaxial, a driving plate 
driven by the driving shaft, a driven plate fast with the driven shaft and 
bearing a continuous circular track eccentric with respect to the common 
axis of the driving and driven shafts, rollers which roll inside the 
circular track, each of these rollers being borne by a rod articulated, 
about a pivot axis, on the driving plate, the articulations of all the 
rods being uniformly distributed over a circle whose center lies on the 
common axis of the two coaxial shafts. Another known apparatus of this 
type comprises two independent assemblies of rollers, tracks, rods, 
articulations and driving plates, these two assemblies having eccentric 
axes diametrically opposite with respect to the common axis of the driving 
and driven shafts. 
In these known apparatus, a diameter A,A' (FIG. 1) passing through axis 0 
common to the driving and driven shafts and through axis 0' of the 
eccentric circular track determines, on this track, two 
semi-circumferences. In one semi-circumference A.A', the axis of each 
roller moves towards the axis 0 of the driving and driven shafts, whilst, 
in the other semi-circumference A'.A, the axis of each roller moves away 
from this axis 0. During the displacement between points A' and A, the 
roller undergoes an acceleration and an increase in its kinetic energy. 
Such acceleration is obtained by the driving force of the rod by the 
driving shaft and further to the angular position of the rod with respect 
to the tangent to the path determined by the track, this driving force has 
for its effect to reduce the centrifugal efforts of the roller in rotation 
on the semi-circumference A'A. On the contrary, during the displacement of 
point A to point A', along the opposite semi-circumference, the roller 
undergoes a deceleration and a reduction in its kinetic energy and 
likewise further to the angular position of the rod, such deceleration 
produces a thrust of the rod and an increase in the efforts of the rollers 
on the track when they rotate on this semi-circumference A.A'. The effects 
of such reductions of the efforts on the path A'.A and of such increases 
of the efforts on the path A.A' add up to exert on axis 0' of the track a 
torque which is transmitted to the driven shaft of axis 0. When the 
receiver begins to rotate then accelerates, the torques transmitted 
decrease as a function in particular of the difference in the speeds 
between the driving shaft and the receiver. This effect is translated by a 
reduction in the frequency of the accelerations and decelerations 
previously indicated. These torques tend towards a zero value when these 
speeds are equal and when the transmission ratio approaches 1/1, then they 
become negative and increasing when this ratio is less than 1/1. 
Furthermore, when the motor rotates, the rollers are subjected to 
continuous centrifugal forces which are exerted in all directions around 
the common axis 0. These centrifugal forces produce positive torques on 
axis 0' during the path from A towards A' and negative ones during the 
path from A' towards A. It will be observed that, further to the angular 
position of the rods with respect to the track, the distribution of the 
number of the rollers and consequently of the active masses, is unequal 
between the two semi-circumferences A.A' and A'.A, these active masses 
being more numerous on the path of A towards A'. The positive torques 
transmitted in part A.A' are then always greater than the negative torques 
transmitted in part A'.A. As a result, even when the ratio of the speeds 
is 1/1 and when the torques due to the accelerations and decelerations no 
longer exist, torques due solely to the centrifugal forces and to the 
unequal distribution of the tollers are always transmitted, the importance 
of these torques being a function of the speed of the motor/receiver 
assembly. 
The torques transmitted by the apparatus are in the first place the torques 
produced as a function of the increases and reductions in kinetic energy 
which are due, as explained previously, to the accelerations and 
decelerations of the rollers. These torques, which are the most important 
at start-up, decrease when the transmission ratio decreases and they tend 
towards a zero value on approaching the ratio 1/1. Moreover with the ratio 
1/1, the torques are transmitted further to the unequal distribution of 
the number of rollers and the centrifugal forces between the 
semi-circumferences A.A' and A'.A. 
This being so, any modification of the speeds and the driving torques 
reacts instantaneously on the transmission ratios and on the receiving 
torques and thus automatically adapts these different parameters to the 
operational conditions of the apparatus. 
However, the heretofore known apparatus of this type present numerous 
drawbacks. In fact, as the rollers roll on the track, in numerous 
situations as a function of the centrifugal forces developed, the rollers 
leave the track and fall on the driving shaft and, when the centrifugal 
forces increase, sometimes suddenly, the rollers are then rejected against 
the track. This results in repeated shocks which damage these members of 
the apparatus. The rollers are not heavy enough to provide sufficiently 
powerful centrifugal forces and the eccentricities between axis 0' of the 
track and the central axis 0 are too reduced to give the apparatus great 
efficiency. The apparatus present a considerable volume especially when 
they comprise at least two assemblies of rollers, tracks and driving 
plates in order to be balanced. 
An attentive examination of FIG. 1 will show that, in fact, the 
accelerations of the rollers in the semi-circumference A'A are produced 
only up to position A" located before position A, and the deceleration of 
the rollers effectively begins at position A" and continues, passing 
through A up to position A'. This zone of deceleration between A" and A 
unfortunately produces negative torques on axis 0' of the track, which 
cause part of the effect of the positive torques produced during the path 
in acceleration from A' to A", to be lost. 
It is an object of the present invention to overcome these drawbacks by 
producing an apparatus having the greatest efficiency in a reduced volume. 
SUMMARY OF THE INVENTION 
This object is attained, according to the invention, in that the apparatus 
comprises, on the driven plate, a second circular track, coaxial and 
inside the first track and on which each roller may roll externally, the 
two coaxial tracks allowing the rollers only a very small clearance 
therebetween. 
According to a complementary feature of the invention, each rod is 
articulated, not directly on the driving plate, but on a heavy weight 
which is itself articulated on the driving plate, and a spring disposed 
between the rod and the weight allows the weight/rod/roller assembly to 
pass zone A".A without noteworthy deceleration and to transfer the 
decelerations and corresponding torques in the positive zone A.A'. 
According to another complementary feature of the invention, each weight is 
rendered heavier in its outer part most remote from its articulation, on 
the driving plate, and the center of gravity of the heavy outer part of 
the weight is offset with respect to the straight line joining the center 
of the roller and the center of the articulation on the driving plate, and 
this forwardly in the direction of the displacement in rotation of the 
roller, with a view to increasing the forces of traction on the rod, 
intended to reduce the centrifugal efforts on the semi-circumference A'A. 
According to another complementary feature of the invention, in order to 
allow large angular clearances of the rods and weights, resulting from the 
considerable eccentricities used, each rod/weight assembly is disposed 
laterally with respect to the roller and is placed, with respect to this 
roller, on the driving plate side. 
The apparatus according to the invention presents a certain number of 
advantages. In the first place, it makes it possible to obtain a wide 
range of automatic continuous variation of the transmission ratio from the 
zero output speed up to beyond the ratio 1/1, which dispenses with using a 
clutch or coupling device between the driving shaft and the variable speed 
drive. Furthermore, the output torques upon start-up may be much greater 
than the nominal driving torque. It also allows an automatic adaptation of 
the ratios of the speeds and the torques to the optimum operational 
conditions. Its design is remarkably simple; it offers a considerable 
facility of manufacture and adaptation; its cost price is low; it presents 
a perfect dynamic balancing; it has a very good mechanical yield, a very 
small space requirement; it is robust and reliable and it enables the 
receiver to be retained by the motor. It also makes it possible to limit 
the range of variation of the speed ratio to the value 1/1 or a 
pre-displayed value. The apparatus according to the invention may be 
applied to very diverse power transmissions.

DETAILED DESCRIPTION OF THE DRAWINGS 
Referring now to the drawings, and firstly to FIGS. 1 and 3, the apparatus 
according to the invention comprises a transverse driving hub 1 fast with 
a driving shaft 2 driven in rotation about a central longitudinal axis 0. 
The driving hub 1, of circular shape, drives in rotation a circular driven 
plate 3 of axis 0 and fast with a coaxial tubular driven shaft 10 
surrounding the driving shaft 2. The driving hub 1 drives a plurality of 
rollers 4 of longitudinal axes B, i.e. parallel to axis 0, and mounted 
respectively to rotate freely about these axes B. Each roller 4 is mounted 
to rotate on a rod 5 which is articulated, about a longitudinal axis, on 
the outer part of a weight 6, via a longitudinal pivot 7 and each weight 6 
is itself articulated on the driving hub 1, via a pivot 8, about a 
longitudinal axis C. 
The pivot pin of each rod is borne by the weight 6 near its end opposite 
that which bears the pivot 8 and this axis of the rod 5 lies to the rear 
with respect to axis C of the pivot 8, this being considered with respect 
to the direction of rotation of the driving hub 1, which rotates in 
clockwise direction in FIGS. 1 and 2. A thrust spring 9 disposed between 
each rod 5 and the weight 6 which bears it, tends to move them away from 
one another, and the angular opening of the rod 5 is limited by a stop 11 
arranged on the weight 6. 
The apparatus according to the invention comprises a plurality of 
assemblies each constituted by a pivot 8, a weight 6, a rod 5, a spring 9 
and a roller 4, the axes C of the pivots 8 being distributed uniformly 
over an inner circle D centered on axis 0 and of smaller radius than the 
greatest distance between axis B of a roller 4 and the common axis 0. 
Rollers 4 roll on the inner face of a cylindrical skirt 12 which 
constitutes a circular track 13. The cylindrical skirt 12 is borne, in its 
central part, by an eccentric journal 14 of axis 0', via a rolling bearing 
(or bearing) 15. This eccentric journal 14 is fast with the driven plate 3 
of axis 0, coaxial with the driving shaft 2 on which it is centered via a 
rolling bearing 16. 
During rolling of rollers 4 on track 13, for example upon start-up or at 
slow speeds of rotation, contact of rollers 4 with track 13 may be lost. 
In order to avoid too considerable transverse displacements of axes B of 
rollers 4, the apparatus comprises, on the cylindrical skirt 12, a second 
circular track 17, coaxial and inside the first track 13 and on which each 
roller 4 may roll externally, the two coaxial tracks 13, 17 allowing the 
rollers only a very small clearance therebetween. 
In order to obtain a sufficiently large assembly of active masses subjected 
to the accelerations, decelerations and centrifugal forces, necessary for 
producing the torques, it is also provided, according to the invention, to 
render the weights heavier. Each of these weights 6 is thus rendered 
heavier in its outer part 6a most remote from its articulation 8 on the 
driving hub 1. This outer part 6a presents a greater width or dimension 
circumference-wise than that of the inner part 6b closest to the pivot 
axis C, as may be more readily seen FIG. 2. The center of gravity G of the 
weight 6/rod 5/roller 4 assembly is thus offset, with respect to the 
straight line BC, forwardly in the direction of rotation of rollers 4 
about axis 0. 
In order to obtain a perfect dynamic balancing of the apparatus and further 
to increase the transmissible torques, the apparatus according to the 
invention may comprise, according to another embodiment of the invention, 
a second assembly of weights 6', rods 5' and rollers 4' rolling on a third 
track 13' forming part of a second cylindrical skirt 12' mounted, via a 
roller bearing (or bearing) 15', on an eccentric journal 14' fast with a 
second driven plate 3' and whose axis 0" is eccentric with respect to the 
longitudinal axis 0, being diametrically opposite axis 0' of the first 
driven plate 3 bearing the first cylindrical skirt 12 and the first track 
13. This second assembly, which is disposed diametrically opposite with 
respect to the first assembly and being transversely offset by distance 
0'0", comprises weights 6 which are articulated, by pivots 8, on the 
driven hub fast with the driving shaft 2. The two weight 6,6'/rod 
5,5'/roller 4,4' assemblies are placed back to back between the two driven 
plates 3, 3'. The two transverse driven plates 3, 3' are furthermore 
connected to each other by a cylindrical body in order to form a 
cylindrical casing 3a containing all the mobile elements of the apparatus. 
The design of the apparatus according to the invention is such that the 
straight line BC (FIG. 1) joining axis B of rotation of a roller 4 to axis 
C of the pivot 8 of weight 6 on the driving hub 1, and the tangent to the 
circular path of the axis of rotation B of roller 4, form an angle a 
which, at its maximum value, is very open and which may vary, for example, 
from 0.degree. to 75.degree. in the course of a revolution, which makes it 
possible to use a considerable eccentricity 00' able to attain 6/10 of 
length BC. 
In order not to have to use rollers 4 of large diameter rolling at high 
speeds of rotation inside track 13 or 13', it has been provided, according 
to the invention, to arrange a roller bearing or bearing 15 or 15' between 
the circular track and its axis 0 or 0". The presence of this roller 
bearing 15 or 15' does not change the results mentioned above, but, by 
allowing the track or tracks 13, 13' to rotate at the same time as the 
roller 4, 4'/rod 5, 5'/weight 6, 6' assembly, rollers 4, 4' no longer have 
to undergo continuous and rapid rotations inside track 13, 13', but only 
relative clearances of small amplitude. This arrangement makes it possible 
to reduce the diameter of rollers 4, 4' as well as the outer dimensions of 
the apparatus. 
FIG. 4 shows another embodiment of the apparatus according to the 
invention. Whilst maintaining the same general characteristics as 
described hereinbefore, it differs from the embodiment of FIG. 3 in that 
the driven elements: tracks 13, 13' and roller bearings 15, 15' borne by 
the driven shaft 10, occupy a central position, and the driving elements: 
weights 6, 6', rods 5, 5' and rollers 4, 4' are borne by driving plates 
2a, 2b connected by a casing 2c which occupy an outer position and which 
contain all the elements. 
FIG. 5 shows another embodiment which differs from the preceding ones in 
that the driving hub 1 is mounted to rotate about the central driven shaft 
10, via a ring or roller bearings 18, and this driving hub 1 is driven in 
rotation by an intermediate plate 19 disposed between the two weight 6, 6' 
assemblies, and fast by its outer edge with the driving plate 20. The 
cylindrical skirts 12, 12' are mounted to rotate on two eccentric journals 
14, 14' fast with the central driven shaft 10. 
FIG. 6 is a front view of a weight/rod/roller/ spring assembly, in which 
weight 6 and rod 5 are spaced apart from each other by the thrust of a 
torsion spring 9 wound around pivot 7. 
For certain industrial applications using heat engines, it is possible to 
adjust and stabilize the output speeds of the driven shaft 10 by using a 
regulator device acting on the admission of the engine and therefore on 
the speeds of rotation and the torques. In that case, the variation is now 
automatically controlled only from start-up to the pre-adjusted output 
speed. Consequently, the range of variation of the output speeds is thus 
limited, stabilizing them at a pre-displayed value. 
If necessary, the invention provides a free-wheel element between the 
driving part and the receiving part in order to limit the range of 
variation to ratio 1/1 and to ensure that the motor is retained on this 
same ratio.