Transmissions of the toroidal-race rolling-traction type

Details Transmissions of the toroidal-race rolling-traction type Transmissions of the toroidal-race rolling-traction type

1992-05-28

1993-08-03

Wright, Dirk

Planetary gear transmission systems or components

Nonplanetary variable speed or direction transmission...

Nonplanetary transmission is friction gearing

F16H 1552

Patent

active

052324141

DESCRIPTION:

BRIEF SUMMARY
This invention relates to transmissions of the toroidal-race rolling-traction type, capable of operating in two different modes or "regimes". Such transmissions, of which examples are shown in patent specification GB-A-1078791, are well known to the man in the art, and comprise in driveline succession a ratio-varying unit or "variator" and one or more gear units of epicyclic or like type. Typically there are two such units, each unit having a component capable of being engaged by a clutch, brake or the like. The output of the second gear unit acts as the output member of the transmission as a whole. With the engaged component of one gear unit held and the other free, traverse of the variator from one end of its ratio range to the other causes the output member to progress continuously from maximum reverse speed, through a condition known as "geared neutral" in which the member is stationary, and then to gather forward speed. During this process the transmission is said to be in "low regime". The components and ratios of the gear units are so chosen that the first engagement may now be released and the second made in its place, without any instantaneous change to the transmitted ratio. The transmission is now said to be in "high regime", and if the variator is now traversed back to the original end of its ratio range, the forward speed of the output member increases continuously.
Sometimes it is desirable to arrange all the major components of such a transmission as nearly as possible coaxial with the operating axis of the variator. Whereas this arrangement is commonplace in toroidal-race transmissions capable of working in a single regime only--as described for example in patent specification GB-A-957145--in a two-regime transmission this has in the past posed two points for particular consideration. Firstly, because the output member of the variator often lies axially-central within that unit, with input members to either side of it, the connection between the variator output and any gear unit downstream of the variator has frequently--as in Patent Specification EP-B-0149892 for example--been in the form of a rotating drum which surrounds and rotates around those parts of the variator that lie downstream of its output member. This can be inconvenient for various reasons, for example if it is wished to ground some of those downstream components of the variator on the housing of the transmission as a whole. Secondly, in many known transmissions of this type it has been found necessary to use different gearing combinations for the two gear units which follow the variator. This naturally adds to complexity and expense by increasing the total number of parts used in the transmission as a whole, and it has frequently--as in patent specifications GB-B-2150240 and EP-B-0149892, for example--required the use of a compound epicyclic gear with double planets for one of the gear units.
The present invention aims to provide a simpler design, potentially with less parts, for a transmission of the concentric type already described.
The invention is defined by the claims and will now be described, by way of example, with reference to the accompanying drawing which is an axial section through the principal components of such a transmission.
The input shaft 1 of a ratio-varying unit ("variator") 2 of the toroidal-race rolling-traction type carries two input discs 3, 4 and is rotated about the operating axis 5 by a prime mover 6. Rollers 7, of variable orientation, transmit drive between input discs 3, 4 and a single but double-faced output disc 8 located midway between the input discs.
A speed-reducing epicyclic gear unit 10 is located axially-downstream of the variator. The sun gear 11 of this unit is mounted on input shaft 1, and the annulus gear 12 can be anchored to the transmission casing 9 by the engagement of a brake 13.
A second and so-called "mixing" epicyclic gear unit 15 is located downstream of unit 10 in the transmission driveline, and the annulus gear 16 of this unit is connected to the output shaft 17 of the

REFERENCES:
patent: 3277745 (1966-10-01), Harned et al.
patent: 4693134 (1987-09-01), Kraus
patent: 4872371 (1989-10-01), Fellows
patent: 5139466 (1992-08-01), Perry

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