Selecting device of a power transmission system for a four-wheel drive vehicle

In a power transmission system for a four-wheel drive vehicle, having a transmission, a transmitting system for transmitting output of the transmission to front and rear wheels of the vehicle, the transmitting system including a double overrunning clutch comprising a forward overrunning clutch including a forward outer race provided with forward outer teeth on a periphery thereof, and forward spragges operatively disposed between said forward outer race and a shaft of said transmitting system, said shaft being rotatably connected to the front wheels, said forward overrunning clutch permitting faster rotation of said front wheels than said rear wheels in a first rotatable direction of said shaft corresponding to forward driving direction of the vehicle to prevent a tight corner braking phenomenon in said forward driving direction, and a reverse overrunning clutch including a reverse outer race provided with reverse outer teeth on a periphery thereof, and reverse spragges operatively disposed between said reverse outer race and said shaft of said transmitting system, said reverse overrunning clutch permitting faster rotation of said front wheels than said rear wheels in a second rotatable direction of said shaft corresponding to reverse driving of the vehicle to prevent said tight corner braking phenomenon in said reverse driving direction, the improvement in the system which comprises

• selecting means comprising an axially slidable sleeve rotatably connected to said transmitting system and provided with inner teeth selectively engagable separately or simultaneously together with said forward and/or reverse outer teeth, respectively, of the forward and reverse overrunning clutches for selectively engaging said forward and/or reverse overrunning clutches in said transmitting system in order to transmit said output to said front wheels, said inner teeth when engaging simultaneously together with said forward and reverse outer teeth locks said double overrunning clutch establishing a directly connected four-wheel driving mode,
• each of said forward outer teeth forming a first chamfer facing with a predetermined angle toward the first rotatable direction,
• each of said reverse outer teeth forming a second chamfer facing with said predetermined angle toward the second rotatable direction, and
• each of said inner teeth at both ends forming third and fourth chamfers respectively with said predetermined angle complementary to said first and second chamfers, respectively, so as to smoothly establish the directly connected non-overrunable four-wheel driving mode.