| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a steering device for construction machinery, capable of effectively attaining reductions in sizes, weights and costs of components. <P>SOLUTION: The steering device includes: cylinders 11, 12 for front wheels 1R, 1L changing directions thereof and cylinders 13, 14 for rear wheels 2R, 2L changing directions thereof and structured so that pressure oil from a hydraulic power source 15 is supplied to the cylinders for the front wheels and the cylinders for the rear wheels though a series oil hydraulic circuit 20. The steering device further includes: a relief valve 22 capable of changing a set pressure of the pressure oil supplied to the series oil hydraulic circuit from the hydraulic power source to at least two high and low stages; discrimination means 23 of discriminating whether a selection mode is a steering selection state of only the front wheels or rear wheels or a steering selection state of all wheels; and a switching means 24 for changing a set pressure by the relief valve based on a signal of the discrimination means and a pressure oil at a middle portion between a front wheel side circuit portion and the rear wheel side circuit portion of the series oil hydraulic circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT |
