| 摘要 |
PROBLEM TO BE SOLVED: To prevent the running speed of a vehicle which incorporates a hydrostatic transmission, on running by its deadweight from becoming excessively high. SOLUTION: A hydrostatic transmission is communicated with a variable displacement type hydraulic pump 12 driven by an engine 11, and a hydraulic variable displacement type hydraulic motor 13 adapted to be rotated by hydraulic oil discharged from the hydraulic pump through main pipe lines 14, 15 in a closed circuit. The output shaft 17 of the hydraulic motor 13 is coupled to a wheel 21 through a rotary transmission mechanism 18. A rotational speed sensor 23 detects the number of rotations per unit time of the output shaft 17. When the running speed is higher than a set value, a proportional control pressure reducing valve 25 produces a signal pressure Px in accordance with a detection signal from the rotational speed sensor 23, and a displacement changing mechanism part 30 receives the signal pressure Px and changes the displacement of the hydraulic motor 13, the higher the signal pressure Px, the larger the volume.
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