Planetary gear transmission systems or components – Planet pinion is friction gear – Variable speed ratio
Patent
1990-08-14
1992-08-18
Lorence, Richard
Planetary gear transmission systems or components
Planet pinion is friction gear
Variable speed ratio
475216, 475217, 74721, 74194, F16H 1550
Patent
active
051394669
DESCRIPTION:
BRIEF SUMMARY
This invention relates to continuously variable transmissions and particularly to a transmission which has two modes or regimes. In a first regime an output member of a variator, such as a toroidal race, rolling traction variator, drives an output shaft or other transmission member directly, such as through a simple gearing or chain connection. In a second regime the output member of the variator drives the output transmission by way of an epicyclic movement providing power recirculation. In both regimes the transmission ratio between the input and output members in the variator can be continuously varied between a minimum and a maximum. For a toroidal race rolling traction variator the variation in transmission ratio is effected by means for altering the rotary axes of rollers which engage toroidal races defined by the input and output members of the variator.
Normally the said second regime is employed for speed ratios between reverse and low forward speed and the said first regime is employed for higher speeds. Various examples of such transmissions are well known.
It is necessary to provide means for changing from one regime to the other. Several such means are known. The one described in U.S. Pat. No. 4,638,687 relies on the arrangement of the transmission to include a relative reversal as between the transmission paths from the output member of the variator to an output shaft. The known system includes a one way drive (such as a sprag clutch) to achieve change over, and in the specific example described in that application, an automatic change over between regimes. The arrangement is such however that the change-over between regimes must occur at some point within the range of variation of transmission ratio of the variator. Moreover, the drive system between the roller epicyclic and the output transmission member is complex and includes two parallel paths, one path typically comprising a sprag clutch and the other path comprising a locking member.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide a transmission of generally similar type, in which the change over between regimes can be a shockless synchronous change, there being no change in overall transmission ratio during the change in regimes, and the transmission is considerably simplified, avoiding the use of parallel transmission paths between the power recirculation system and the output transmission member and the consequent necessity of a change in transmission path within the second regime.
To this end, the transmission is arranged such that when the second or "low" regime provides a maximum forward speed, the ratio of the variator is at its maximum reduction and this corresponds to the minimum forward speed provided in the first or "high" regime. A change over between regimes under these circumstances is a shockless synchronous change. Only simple declutching and clutching operations are required for the change over and, where clutches are provided in both the transmission path directly from the output member of the variator to the output transmission member (such as the output shaft) and in the transmission path between the power recirculation system and the said output transmission member, both clutches could be engaged during the change over between regimes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates one embodiment of the invention.
FIG. 2 illustrates a second embodiment of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Referring firstly to FIG. 1, an input shaft 1 for the transmission unit has fixed to it a first, input member 2 of a variable transmission unit, herein called a variator, comprising a toroidal race confronting a second, output member 3 of the unit likewise comprising a toroidal race. Rollers 4 engage the two toroidal races and by means of a known adjusting system 5 can be changed in their axes of rotation to provide a continuously variable transmission ratio between the input and output members of the unit. Typically the range of transmission ratio can vary betwee
REFERENCES:
patent: 2060884 (1936-11-01), Madle475216
Farley Walter C.
Levi Benjamin
Lorence Richard
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