1. Field of the Invention
The present invention relates to twin clutch type speed-change apparatuses and, in particular, to a twin clutch type speed-change apparatus that applies a dog clutch to speed-change gears that slide on a main shaft and a countershaft for changing the number of speed-change steps.
2. Description of Background Art
A multi-step transmission is known wherein a plurality of speed-change gear pairs are configured such that shifting operation is executed to allow shift forks sliding parallel to a main shaft and to a countershaft to drive speed-change gears and sleeves slidable on the main shaft and the countershaft. An automatic transmission is also known that eliminates the operator's shifting operation by allowing an actuator such as an electric motor or the like to drive such shift forks.
Japanese Patent Laid-Open No. 2006-153235 discloses an automatic transmission allowing an actuator to drive shift forks configured to apply a synchromesh mechanism to a sleeve driven by the shift fork to reduce shift shock during shifting.
The synchromesh mechanism as shown in Japanese Patent Laid-Open No. 2006-153235 is composed of a plurality of parts to synchronize the rotating speeds of gears. Thus; the structure is complicated and the weight of the transmission may probably increase.
A twin clutch type speed-change apparatus may be configured to include a twin clutch composed of a first clutch and a second clutch so that a shifting operation can be enabled between two adjacent speed-change steps by switching the engaging/disengaging states between the first clutch and the second clutch. In such a case, it is desired to simplify the structure without use of the above-mentioned synchromesh mechanism.