Patent ID: 8308597

Claim:
A speed change transmission system having: a hydrostatic stepless speed change device for receiving engine drive; and a planetary transmission device having a plurality of planetary transmission mechanisms for combining output of the hydrostatic stepless speed change device and the engine drive not undergoing a speed change action by the hydrostatic stepless speed change device; a combined driving force from the planetary transmission device being stage-divided into a plurality of speed ranges, and subjected to stepless speed changing at each speed range for output from an output rotary member; the speed change transmission system comprising: a first output gear interlocked to the planetary transmission device; a first input gear meshed with the first output gear; a first transmission shaft for supporting the first input gear; a first speed range setting clutch corresponding to the first transmission shaft, and having a first state for fixing the first input gear to the first transmission shaft, and a second state for allowing rotation of the first input gear relative to the first transmission shaft; a second output gear interlocked to the planetary transmission device; a second input gear meshed with the second output gear; a second transmission shaft for supporting the second input gear; and a second speed range setting clutch corresponding to the second transmission shaft, and having a first state for fixing the second input gear to the second transmission shaft, and a second state for allowing rotation of the second input gear relative to the second transmission shaft; wherein the first and second transmission shafts are arranged in parallel for selectively transmitting drive to the output rotary member, wherein the speed change transmission system comprises at least three transmission shafts including the first and second transmission shafts, having corresponding gear pairs and corresponding speed range setting clutches, and interlockable to the planetary transmission device through the gear pairs and the speed range setting clutches, and wherein the at least three transmission shafts are arranged in parallel for selectively transmitting drive to the output rotary member.