| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent from missing the right timing in changing a transmission gear ratio of HST for reducing a shift shock when a velocity stage of a variable speed transmission device is automatically changed.SOLUTION: In the case that a load torque of a driving motor 32 is within a first range D, stepped variable transmission control means 84 performs automatically a shift-down operation from a state in which a power is transmitted by a high-speed side transmission mechanism 60 to a state in which a power is transmitted by a low-speed side transmission mechanism 50, and in turn, in the case that the load torque of the driving motor 32 is within a second range D, the stepped variable transmission control means 84 performs automatically a shift-up operation from a state in which a power is transmitted by the low-speed side transmission mechanism 50 to a state in which a power is transmitted by the high-speed side transmission mechanism 60. In the case that the stepped variable transmission control means 84 performs an automatic changing of a velocity stage of a stepped variable transmission device 40, continuously variable transmission control means 83 controls a capacity Q of the driving motor 32 within a period from starting changing of the velocity stage to a period just before its completion so as to change a transmission gear ratio of HST in an opposite direction to that of the change of a transmission gear ratio at the stepped variable transmission device under changing of the velocity stage.</p> |
