Patent Number: 6,332,316

Title: Hydraulic control device for working vehicle

Abstract: A hydraulic control device for a working vehicle capable of enhancingexcavating ability even when earth to be excavated is hard is provided.For this end, the device includes an unloading valve (14) for allowingdischarge oil from a second pump (5) to be freely drained, a pressureincreasing valve (22, 24) connected to a working machine circuit (9a)downstream of the junction of a working machine circuit (9, 9a) and anassistance circuit (13) for increasing a set pressure of pressure oil inthe downstream working machine circuit (9a), a check valve (17) forchecking back-flow of the pressure oil in the downstream working machinecircuit (9a) toward the unloading valve (14), and a controller (16) fordraining discharge oil from the second pump (5) by the unloading valve(14) and increasing the set pressure of the downstream working machinecircuit (9a) by the pressure increasing valve (22, 24) when a transmission(3) is shifted down from a second speed gear to a first speed gear onreceipt of an actuating signal from a shift-down switch (15).

Inventors: Morimoto; Katsuyuki (Kawagoe, JP), Nozawa; Yasuhiko (Kawajima-machi, JP), Saito; Hiroya (Kawagoe, JP)


International Classification: E02F 9/22 (20060101); F15B 11/00 (20060101); F15B 11/17 (20060101); F15B 11/028 (20060101); F16D 031/02 ()

Expiration Date: 12/25/2014