Continuously variable transmission

Abstract

The invention is concerned with a continuously variable transmission incorporating a variator of the type having at least two co-axial races (D1-D4) between which drive is transferred at a continuously variable variator ratio. The variator races are mounted for rotation about a variator shaft ( 15 ). The transmission has a layshaft ( 18 ) which is laterally separated from the variator shaft. It has two epicyclic gears. A splitter epicyclic ( 14 ) has an input member driven from the transmission input ( 10 ) and two output members arranged respectively to drive the layshaft and the variator shaft. A recirculater epicyclic has first and second input members for coupling respectively to the variator shaft and to the layshaft and a recirculater output member. An arrangement of clutches is provided for selectively engaging any of at least three regimes. In one regime the recirculater output member drives the transmission output. In another the layshaft drives the transmission output. In a third, the variator shaft drives the transmission output. The arrangement of the components is such that the variator shaft is co-axial with the transmission output, the recirculater epicyclic, a first coupling, between the recirculater output member and the transmission output, which serves to drive the transmission output in the first regime, and a second coupling, between the variator shaft and the transmission output, which serves to drive the transmission output in the third above-mentioned regime.

What is claimed is: 
     
         1 - 17 . (canceled) 
     
     
         18 . A unit for attachment to a continuously variable host transmission in order to provide the transmission with an additional regime, the unit comprising a rotary final transmission output, a first rotary input engageable with a first output of the host transmission, a second rotary input engageable with a second output of the host transmission, and an arrangement of gearing and clutches for selectively connecting the final transmission output to at least one of the first and second rotary inputs. 
     
     
         19 . A unit as claimed in  claim 18  further comprising gearing for providing a speed change between at least one of the inputs and the final transmission output. 
     
     
         20 . A unit as claimed in  claim 18  in which the first rotary input is constantly connected to the first transmission output and the second rotary input is selectively connectable to the final transmission output by means of a clutch. 
     
     
         21 . A unit as claimed  claim 18  in which the first rotary input and the final transmission output are epicyclic and an epicyclic gearing arrangement is provided for operatively coupling them. 
     
     
         22 . A unit as claimed in  claim 18  in which the second rotary input and the final transmission output are offset from one another and a gear arrangement is provided for operatively coupling them.