Shift mechanism, and vehicle equipped therewith

Abstract

A shift mechanism that provides a shift mechanism for enabling smooth gear shifting by a transmission, and a vehicle equipped therewith. With this mechanism, a shift drum, to which shift forks are connected via grooves on an outer periphery, is held every predetermined rotation angle. When differences are produced in the degree of rotation between a third rotating member that rotates by motor rotation and a second rotating member that rotates in accordance with the third rotating member, bias is accumulated in a torsion spring. Bias that is accumulated is released when the rotation angle of the third rotating member equals or exceeds a predetermined angle of rotation, rotating a first rotating member via a second rotating member, and rotating the shift drum quickly.

1 . A shift mechanism for moving shift forks connected to a gear of a transmission and changing a gear position of the transmission, the shift mechanism comprising:
 a shift cam arranged on an outer periphery thereof, cam grooves arranged to engage the shift forks, to rotate at a predetermined rotation angle, and to move the shift forks at a certain rotation angle;   a cam phase holding section arranged to hold the shift cam at phases determined per the certain rotation angle;   a rotating section arranged to rotate in forward and reverse directions from a reference position, and to rotate and to move the shift cam through the certain rotation angle;   a transferring section arranged to rotate by section of motor rotation, to rotate in one of the forward and reverse directions from the reference rotation position, and, by transferring that rotation to the rotating section, rotates the rotating section;   a regulating section arranged to, while the transferring section is rotating in one direction, regulate the rotation of the rotating section until a predetermined rotation angle is reached, and to allow the rotation of the rotating section at or above the certain rotation angle;   a bias accumulating section including a biasing member arranged to increase a bias following an increase in a rotation angle of the transferring section in the one direction; and   an accumulated torque releasing section arranged to, when the rotation angle of the transferring section reaches the predetermined rotation angle, release the bias accumulated in the bias accumulating section and to transfer torque to the transferring section; wherein   the rotating section is arranged to make the shift cam held in the cam phase holding section rotate by section of rotation of the transferring section to which torque is applied from the accumulated torque releasing section.   
   
   
       2 . The shift mechanism according to  claim 1 , wherein
 every time a transmission gear of the transmission is shifted one gear, the shift cam rotates in a same direction two consecutive times, in accordance with the rotating section;   the cam phase holding section is arranged to apply rotation torque of a same direction, to the shift cam that is rotating; and   when the shift cam rotates in the same direction two consecutive times, torque that is supplied from the torque supply section to the shift cam in the first rotation is greater than the rotation torque supplied from the torque supply section to the shift cam in the second rotation.   
   
   
       3 . The shift mechanism according to  claim 1 , further comprising a torque transferring section arranged to transfer torque from the rotating section to the shift cam; wherein
 after the transferring section rotates through a predetermined rotation angle or more in one of forward and reverse directions from the reference rotation position, the transferring section rotates in the other one of the forward and reverse directions and returns to the reference rotation position;   after the rotating section rotates in one of the forward and reverse directions from the reference rotation position in accordance with the transferring section, the rotating section rotates in the other one of the forward and reverse direction and returns to the reference rotation position; and   the torque transferring section is arranged to transfer torque from the rotating section to the shift cam when the rotating section rotates from the reference rotation position in accordance with the transferring section, and does not transfer torque from the rotating section to the shift cam when the rotating section rotates and returns to the reference rotation position.   
   
   
       4 . The shift mechanism according to  claim 1 , wherein the transmission includes:
 a first clutch arranged to input rotation power transferred from a crankshaft to a first main shaft and to output the rotation power to a driving wheel via an odd-numbered transmission gear mechanism including odd-numbered transmission gears; and   a second clutch arranged to input the rotation power transferred from the crankshaft to a second main shaft and to output the rotation power to the driving wheel via an even-numbered transmission gear mechanism including even-numbered transmission gears; wherein   the first and second main shafts are provided in a mutually rotatable fashion on an axis parallel or substantially parallel to the crankshaft; and   a portion in the second main shaft where drive to be output to the driving wheel via the even-numbered transmission gear mechanism is transmitted has substantially a same outer diameter as a portion in the first main shaft where drive to be output to the driving wheel via the odd-numbered transmission gear mechanism, and is located not to coaxially overlap the portion in the first main shaft; and   the shift cam changes the gear positions of the odd-numbered transmission gear mechanism and the even-numbered transmission gear mechanism alternately, via the shift forks, per the certain rotation angle.   
   
   
       5 . A vehicle comprising:
 an engine;   a driving wheel; and   a transmission arranged to transmit torque produced in the engine to the driving wheel at a plurality transmission gear ratios; wherein   the transmission comprises the shift mechanism according to  claim 1 .