Patent ID: 8899035
Filing Date: 2014-12-02
Classification: E02F,F15B

Abstract:
1. A hydraulic control apparatus for a work machine, comprising: an engine that provides a driving source for the work machine; an accelerator dial being set to one position of plural positions to set an engine speed in accordance with the position of the accelerator dial; a hydraulic pump that is provided on an open center hydraulic circuit and is driven by the engine, the output of the hydraulic pump being set in accordance with the position of the accelerator dial, and the hydraulic pump having a pump characteristic for minimizing a discharge flow rate of the hydraulic pump in accordance with the position of the accelerator dial when the negative control pressure is equal to or greater than a first predetermined pressure; a hydraulic actuator that is interposed on the hydraulic circuit and is operated responsive to a hydraulic fluid provided by the hydraulic pump; a negative control circuit that directs a hydraulic pressure in a center bypass in the hydraulic circuit to the hydraulic pump, as a negative control pressure; an orifice provided on the center bypass and having a choking characteristic wherein the negative control pressure decreases below the first predetermined pressure as the flow rate decreases; an idling detection device that detects whether the hydraulic actuator is a non-operated state or not; and a negative control pressure control device that controls the negative control pressure to an arbitrary value, wherein the negative control pressure control device controls the negative control pressure by forcing it to the first predetermined pressure or higher irrespective of the position of the accelerator dial when the non-operating state of the hydraulic actuator is detected by the idling detection device.