Patent ID: 7172527

Claim:
A planetary-gear-type multiple-step transmission for a vehicle, having a plurality of drive positions which are selectively established, said transmission comprising: a stationary member; an input rotary member; an output rotary member; a first transmission unit which is connected to said input rotary member; and a second transmission unit which is connected to said output rotary member, wherein said first transmission unit has first and second intermediate transmitting paths through which a rotary motion of said input rotary member is transmittable to said second transmission unit such that a speed of the rotary motion transmitted through said second intermediate transmitting path is lower than a speed of the rotary motion transmitted through said first intermediate transmitting path, wherein said second transmission unit includes two planetary gear sets each having a sun gear, a carrier and a ring gear, said second transmission unit further including first and second brakes, and first, second, third and fourth clutches, wherein said second transmission unit constitutes first, second, third and fourth rotary modules, each of which is provided by at least one of the sun gears, carriers and ring gears of said two planetary gear sets, wherein said first rotary module is selectively connected to said second intermediate transmitting path through said second clutch, while being selectively connected to said stationary member through said first brake, wherein said second rotary module is selectively connected to said first intermediate transmitting path through said third clutch, while being selectively connected to said stationary member through said second brake, wherein said third rotary module is connected to said output rotary member, wherein said fourth rotary module is selectively connected to said first intermediate transmitting path through said fourth clutch, while being selectively connected to said second intermediate transmitting path through said first clutch, wherein said plurality of drive positions are established by selectively engaging and releasing said brakes and said clutches, wherein said second rotary module is rotatable at a rotational speed, which is intermediate between rotational speeds of the respective first and third rotary modules except when the rotational speeds of said respective first and third rotary modules are equal to each other, wherein said third rotary module rotational speed which is intermediate between rotational speeds of the respective second and fourth rotary modules except when the rotational speeds of said respective second and fourth rotary modules are equal to each other, and wherein a difference between rotational speeds of the respective second and third rotary modules is larger than a difference between rotational speeds of the respective third and fourth rotary modules except when the rotational speeds of said respective second and fourth rotary modules are equal to each other.