Transmission and method of up-shifting for transmission

An up-shifting method for a transmission in which a plurality of gears are relatively rotatably supported on a rotational shaft, and in which a desired shift stage is achieved by selectively connecting any one of the plurality of gears to the rotational shaft by means of a corresponding one of clutch mechanisms,

• each of the clutch mechanism including
• a strut-installation groove formed in an outer circumferential portion of the rotational shaft that is formed to have a hollow structure;
• a strut swingably supported in an inside of the strut-installation groove;
• a first engagement face which is formed on a trailing side of the strut in a rotational direction of the gear and which is capable of engaging with a cutaway formed in an inner circumferential surface of the gear;
• and
• a second engagement face which is formed on a leading side of the strut in the rotational direction of the gear and which engages with the strut-installation groove, and
• each of the clutch mechanisms being capable of switching the following states in accordance with the position of a slide cam that is disposed in an inside of the rotational shaft so as to be movable in an axial direction, and that performs the up-shifting operation by sequentially changing each swinging state of the strut of each shift stage, said states being:
• an engaged state where the first engagement face of the strut is forced to protrude in the cutaway of the gear;
• a one-way state where the first engagement face of the strut and the cutaway of the gear are engaged with or disengaged from each other in accordance with the rotating direction of the gear relative to the rotational shaft;
• and
• a disengaged state where the first engagement face of the strut is forced to withdraw from the cutaway of the gear,
• wherein the up-shifting method comprises:
• a first step of moving the slide cam in the up-shifting direction from a first position to a second position,
• in the first position, the gear set of the lower-speed side shift stage being in the engaged state and the gear set of the higher-speed side shift stage being in the disengaged state, and
• in the second position, the gear set of the lower-speed side shift stage being in the one-way state where the gear set is capable of transmitting the driving force and the gear set of the higher-speed side shift stage being in the disengaged state;
• and
• a second step of moving the slide cam in the up-shifting direction from the second position to a third position,
• in the third position, the gear set of the higher-speed side shift stage being in the engaged state and the gear set of the lower-speed side shift stage being in the disengaged state.