Patent ID: 8635927

Claim:
A speed change device for shifting a gear of a transmission, comprising: a plurality of speed-changing sleeves in said transmission, said plurality of speed-changing sleeves moving in an axial direction to shift the gear; a plurality of forks for moving said speed-changing sleeves, said plurality of forks comprising a plurality of fork operation members coupled thereto; a cylindrical drum that is installed so as to be reciprocally movable in the axial direction and being rotatably supported, the cylindrical surface of said cylindrical drum forming a plurality of drum grooves into which said fork operation members are fitted, wherein said drum grooves are each forming, continuously in a circumferential direction, small width portions with their both sides being perpendicular to an axial direction of said cylindrical drum and having a width in the axial direction of said cylindrical drum nearly equal to that of a fork operation member of said fork operation members, and large width portions having a groove width in the axial direction of said cylindrical drum larger than that of said fork operation member, said small width portions and said large width portions in the plurality of the drum grooves being provided such that said fork operation member positioned at said small width portion is changed depending upon a rotation of said cylindrical drum, whereby said fork operation member positioned at said small width portion of said drum groove is selected by the rotation of said cylindrical drum, and the selected fork operation member is moved in the axial direction of said cylindrical drum by the reciprocal motion of said cylindrical drum; a rotary drum sleeve that is arranged inside of said cylindrical drum; a threaded shaft that is arranged penetrating through said rotary drum sleeve in concentric with said rotary drum sleeve; a nut body that is located in said cylindrical drum at a portion apart from said rotary drum sleeve in an axial direction of said threaded shaft, wherein said cylindrical drum is fitted together onto said rotary drum sleeve so as to slide but so as not to rotate, and is screw-coupled via said nut body to said threaded shaft; and a select actuator and a shift actuator mounted on a casing of said transmission, each actuator operating independently, wherein said select actuator rotates said rotary drum sleeve around said threaded shaft accompanying the rotation of said cylindrical drum, and wherein said shift actuator rotates said threaded shaft accompanying the reciprocally movement of said cylindrical drum in the axial direction of said cylindrical drum.