Automatic transmission assembly for a vehicle, and vehicle incorporating same

An automatic transmission assembly for transmitting rotary power from a crankshaft to a drive train component, said automatic transmission assembly comprising

• a main shaft operatively connected with said crankshaft;
• an auxiliary shaft operatively connected with said main shaft;
• a transmission unit having a plurality of gear pairs which provide a plurality of gear positions between the main shaft and the auxiliary shaft;
• a twin clutch assembly having a first clutch and a second clutch disposed on one of said main shaft and said auxiliary shaft;
• said twin clutch assembly selectively and operatively transmitting a rotary drive power from the crankshaft to said transmission unit;
• a shift drum operatively connected to the transmission unit;
• a shift fork selectively engagable with the shift drum;
• a shift position sensor which detects an angular position of said shift drum;
• said shift position sensor being operatively connected to said shift drum;
• a controller which changes angular positions of the shift drum for actuating the shift fork;
• and
• said controller providing an engagement and a disengagement position of said twin clutch assembly for selecting one of said plurality of gear pairs to transmit said rotary drive power from the crankshaft to said transmission unit;
• wherein:
• said transmission unit shifts transmission of said rotary drive power between adjacent two of said plurality of gear positions in response to switching of said first clutch and said second clutch into and out of engagement position when said shift drum is in a predetermined angular position for a selected gear position;
• said shift drum comprises a partially neutral position disposed thereon between said predetermined angular positions of said shift drum;
• said partially neutral position is configured to temporarily reduce the angular speed of said shift drum when the shift drum is being angularly rotated;
• and
• the shift position sensor detects said predetermined angular positions and said partially neutral position.

A vehicle comprising a power unit including a crankcase, a crankshaft rotatably supported in the crankcase, and a transmission assembly operatively connected to said crankshaft;

• said transmission assembly comprising:
• a main shaft operatively connected with said crankshaft;
• an auxiliary shaft operatively connected with said main shaft;
• a transmission unit having a plurality of gear pairs which provide a plurality of gear positions between the main shaft and the auxiliary shaft;
• a pair of clutches having a first clutch and a second clutch disposed on said main shaft, said pair of clutches selectively and operatively transmitting a rotary drive power from the crankshaft to said transmission unit;
• a shift drum operatively connected to the transmission unit;
• said shift drum comprising a plurality of angular positions corresponding to said plurality of gear positions;
• a shift fork selectively engagable with the shift drum;
• a shift position sensor which detects an angular position of said shift drum;
• said shift position sensor being operatively connected to said shift drum;
• a controller which changes an angular position of the shift drum for actuating the shift fork;
• said controller selectively engaging one of said first clutch and said second clutch with said crankshaft to transmit said rotary drive power from the crankshaft to said transmission unit;
• wherein said transmission unit shifts transmission of said rotary drive power between adjacent two of said plurality of gear positions by selectively engaging one of said first clutch and said second clutch when said shift drum is in a predetermined angular position for a selected gear position,
• said controller performs a preliminary upshifting action in advance by controlling angular rotation of said shift drum to a first selected angular position based on a next gear position in an upshifting direction while said rotary drive power from the crankshaft to the transmission unit is being maintained at a present gear position,
• wherein when an upshifting command is output, said controller engages one of said first clutch and said second clutch depending on the upshifting command,
• when a downshifting command is output, said controller performs a preliminary downshifting action in advance by controlling angular rotation of said shift drum to a second selected angular positions depending on a next gear position in a downshifting direction based on said downshifting command, and
• when the shift position sensor detects a completion of said preliminary downshifting action based on said second selected angular position of said shift drum, said controller operatively engages one of said first clutch and said second clutch with said crankshaft.