Friction gear transmission systems or components – Friction gear includes idler engaging facing concave surfaces – Toroidal
Patent
1992-07-29
1993-11-23
Braun, Leslie A.
Friction gear transmission systems or components
Friction gear includes idler engaging facing concave surfaces
Toroidal
476 72, 475192, F16H 1508
Patent
active
052639070
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
This invention relates to continuously-variable-ratio transmissions of the toroidal-race rolling-traction type. In the variator, that is to say the ratio-varying component, of such a transmission, coaxial and rotatable input and output discs confront each other, each disc being formed with a part-toroidal race coaxial with the disc itself, the races being complementary and thus conforming to different parts of the surface of a single common torus. Rollers of variable orientation roll in contact with both races, and transmit drive between them. When the roller contacts the output disc at a greater radius (relative to the common axis of the discs) than that at which it contacts the input disc, the output disc will rotate slower than the input disc. Conversely, when the corresponding radius at which the roller contacts the input disc is the greater, the output disc will rotate faster than the input disc. It relates in particular to such transmissions of the so-called "full toroidal" kind in which the races are so shaped that contact between the roller and a race can take place at a radius, measured from the common axis of the discs, that is substantially greater than the corresponding radius of the center of the common torus. It is a characteristic of a transmission of the full toroidal type, that the direction of the normal reaction at each point of contact between a race and a roller passes through the roller center.
BRIEF DESCRIPTION OF THE DRAWING(S)
In the accompanying diagrammatic drawings,
FIG. 1 is a section through the variator of a known transmission of the toroidal-race rolling-traction type and the full toroidal kind, taken in a plane including the transmission axis, and
FIGS. 2, 3 and 4 are local views taken in the directions indicated by arrows II, III and IV in FIG. 1.
FIG. 5 is a section through the variator of a toroidal-race rolling-traction type transmission.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
FIG. 1 shows an input disc 1 mounted on an input shaft 2, and an output disc 3 mounted on an output shaft 4. Shafts 2 and 4 share a common axis 5. Input disc 1 is formed with a part-toroidal race 6 and output disc 3 with a corresponding race 7. Although by torus we mean any ring-shaped body generated by rotating any closed plane figure of generally curved outline about a generator line sharing a common plane with the figure but lying outside its outline, in the typical known variator as shown in FIG. 1 the surfaces of races 6 and 7 conform to the surface of the special case of a torus generated by rotating a circle around axis 5, the circle and the axis lying in a common plane at all times. A set of roller--typically three in number--roll in contact with both of races 6 and 7 and transmit drive between them with reversal of direction, so that the direction of rotation of shaft 4 is always opposite to that of shaft 2. One of such rollers is shown at 10; each such roller rotates about an axle 11 which is mounted to rotate in a carriage 12. When carriage 12 is tilted as indicated by arrow 13, by means not shown but well known in the art, the ratio transmitted from disc 1 to disc 3 is varied.
In the upper half of FIG. 1 the roller 10, shown in full lines in the position referenced 9, lies with its diameter parallel to axis 5. Disc 3 therefore rotates at the same speed as disc 1, although with opposite sign. If roller 10 is tilted to the position shown in broken lines at 14 in the lower half of the Figure disc 3 will rotate slower than disc 1. Conversely if the roller is tilted to the position shown in broken lines at 15, disc 3 will rotate faster than disc 1.
As is shown in the arrowed enlarged view attached to FIG. 1, the rim 20 of roller 10 is rounded at a radius r.sub.c, known as the roller cross-radius and measured in a plane including the variator axis 5, that is smaller than the local torus radius r.sub.d of the race 7 measured in the same plane. In practice, r.sub.d is likely to be, say, twice r.sub.c. Unless the position of the roller centre is otherwise con
REFERENCES:
patent: Re20801 (1938-07-01), Gove et al.
patent: 2020677 (1935-11-01), Erban
patent: 2786363 (1957-03-01), Davies et al.
patent: 4484487 (1984-11-01), Kraus
patent: 4909092 (1990-03-01), Machida et al.
Braun Leslie A.
Torotrak (Development) Limited
Trousdell William O.
LandOfFree
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