Transmission and sub-transmission with mutually contending helical gears

Claim 1

A transmission for an automotive vehicle, comprising: (a) a main transmission device comprising: a main casing; a rotatably supported power output shaft; a tubular intermediate shaft rotatably supported parallel to the power output shaft; and a plurality of helical gears on said shafts for transmitting rotational power between them; the helical engagement of at least one pair of said helical gears, one of which is on said tubular intermediate shaft, exerting a first axial force on said tubular intermediate shaft when said pair of helical gears are transmitting rotational power with said tubular intermediate shaft rotating in a certain predetermined rotational direction; (b) a power input shaft coaxial with the tubular intermediate shaft and passing through its central hole, with its one end protruding out of one end of said tubular intermediate shaft, and its other end protruding out of the other end of said tubular intermediate shaft and being driven; and (c) a substransmission comprising: a sub-casing; a helical sun gear; a carrier connected to said one end of the power input shaft; a helical ring gear connected to said one end of the tubular intermediate shaft; a plurality of helical pinions rotatably supported by the carrier and meshed between the sun gear and the ring gear; and a frictional engagement means which selectively connects said sun gear to either said sub-casing or said ring gear, and which comprises a frictional engagement element rotationally connected with said sun gear, a spring which drives said frictional engagement element in a first axial direction opposite to the direction of said first axial force toward engagement with said ring gear and exerts a second axial force on said tubular intermediate shaft via said frictional engagement element and said ring gear when said frictional engagement means is connecting said sun gear to said ring gear, said second axial force opposing to said first axial force, and a fluid pressure actuator which, when actuated, drives said frictional engagement element in a second axial direction opposite to said first axial direction toward engagement with said sub-casing by overcoming said spring; wherein the handedness of said ring gear and said pinions is so arranged that, when the power input shaft and the carrier are being driven in said certain rotational direction and are rotationally driving the ring gear and the tubular intermediate shaft via a planetary movement of the planetary pinions, in said certain rotational direction, the helical engagement of said planetary pinions and said ring gear exerts a third axial force on said tubular intermediate shaft via said ring gear wheich is opposed to said first axial force.