| 摘要 |
<p>PURPOSE:To prevent increase of a running motor circuit pressure, by a method wherein, when steering is effected on a poor road surface condition, a high and low speed switching valve is automatically switched to a low speed position in linkage with driving of the one running motor. CONSTITUTION:When steering is effected on a poor road surface condition, when a switching valve 5 is in a left position being a high speed shift, only a lever 2 for left control is driven. In which case, a pilot pressure from a pilot pump 1 is exerted on the driving part of a control 11 to shift the driving part to a left position, and pressure oil from a main pump 10 is guided to a running motor 16 to drive a caterpillar. In this case, since, by means of a pilot pressure fed through a switching valve 3, a switching valve 24 is shifted to a left position, even if a switching valve 5 is shifted at a high speed, a high and low speed switching valve 14 is shifted to a low speed position, and catapillar is operated at a low speed.</p> |
