| 摘要 |
A mechanical type transmission (3; MT) is provided between an input shaft (1) and an output shaft (2), and a hydrostatic liquid pressure type transmission (4; HST) is provided in juxtaposition with the mechanical type transmission. Provided between the input shaft and the MT is a third planetary gear mechanism (15) for reducing a rotation frequency of the input shaft to a reduced rotation frequency corresponding to a set reduction ratio, and provided are a fourth clutch mechanism (13) for inputting at the reduced rotation frequency in regions of low and medium transmission gear ratios, and a fifth clutch mechanism (14) for inputting at the rotation frequency of the input shaft in a region of high transmission gear ratio, so that an increase in operation mode can be obtained. A controller (18) performs intermittent switching control of the clutch mechanisms (10 to 14) and control of swash plate angle of a variable swash plate (51) so as to maintain an output to MT from HST in non-transmitting state, and seven points where a lockup operation can be made are provided between the low and high transmission gear ratios. Accordingly, points of lockup operation are increased to attain an enhancement of transmission efficiency at the time of lockup operation. An increase in points of lockup operation is realized while achieving an increase in output of the entire HST without making HST large-sized. An increase in points of lockup operation is realized without making the last reduction gear of a vehicle, to which a non-stage transmission is applied, large-sized.
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