Patent ID: 8713930
Filing Date: 2014-05-06
Classification: E02F,F04B,F15B

Abstract:
1. A negative control type hydraulic system comprising: an engine; at least one variable-displacement hydraulic pump connected to the engine; at least one hydraulic actuator connected to the hydraulic pump; switching valves installed in a center bypass line of the hydraulic pump and shifted, in accordance with the supply of signal pressure from the outside, to control a flow of hydraulic fluid supplied to the hydraulic actuator; pilot signal pressure generation means installed on a downstream side of the center bypass line to generate signal pressure for variably controlling a discharge flow rate of the hydraulic pump; a control lever outputting signal pressure in proportion to a manipulation amount; a shuttle valve selecting and outputting one of hydraulic fluid supplied from the hydraulic pump through a pilot line that is branched and connected to the center bypass line and return hydraulic fluid supplied through a recycle return line that is connected to a recycle valve recycling the hydraulic fluid that is returned from the hydraulic actuator; and a pressure reducing valve installed in a pilot line between the shuttle valve and the control lever, and controlling hydraulic fluid supplied from the shuttle valve when the control lever is manipulated so that the hydraulic fluid supplied through the shuttle valve can be used as the signal pressure in accordance with the manipulation of the control lever.