Oil-pressure controlling device for earthmoving machine

Abstract

An optimal pump flow for both dual tilt operations and single tilt operations is obtained at low cost without increasing the complexity of the device constitution. Where there is a wish to implement a dual tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value decreases and a comparatively small flow is supplied from the hydraulic pump to the left and right tilt cylinders. Accordingly, the extension/retraction speed of the left and right tilt cylinders decreases. Where there is a wish to implement a single tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value increases and a comparatively large flow is supplied from the hydraulic pump to the left cylinder. Accordingly, the extension/retraction speed of the left tilt cylinder increases. In this way, the tilt operating speed of the blade in dual tilt operations is made to be the same as the tilt operating speed of the blade in single tilt operations. By virtue of this, when a changeover is implemented from a dual tilt operation to a single tilt operation (or when the reverse changeover thereto is implemented), the operating speed of the bladeis unaltered and the discomfort associated with the alteration of the operating speed when this changeover is implemented can be alleviated. Accordingly, the operability throughout the working of the bulldozer is markedly improved.