Hitachi Construction Machinery Co., Ltd.

Yoshinobu Kobayashi

Hiroshi Matsuzaki

Katsumi Ueno

Mitsuhisa Tougasaki

Takeshi Kobayashi

Ryouhei Yamashita

Masaaki Andou

Satoru Kubota

A valve housing of a multiple valve device is formed by being split into two parts, that is, a first housing block and a second housing block abutting against and separated away from each other at positions of facing joining surfaces. Three or more spool sliding bores are provided on the first housing block forming a three-dimensional structure. The other spool sliding bores are provided on the second housing block forming a three-dimensional structure. A relief valve for suppressing maximum pressures in a plurality of oil passages to a predetermined set pressure or less is provided on one of the first and second housing blocks. This relief valve is arranged at a position closer to the joining surfaces than each of the spool sliding bores provided in the one of housing blocks.

Multiple valve device

A boom control valve and a pulsation absorption control valve are provided in the halfway point of a center bypass line. The pulsation absorption control valve is arranged in a position downstream of the boom control valve. The pulsation absorption control valve is switched to a blockade position and a communication position by a pilot pressure from a remote control valve. The pulsation absorption control valve is constituted such that one main line out of a pair of main lines is communicated with or blocked off from an accumulator via one communication line and the other main line is communicated with or blocked off from the side of a tank via the other communication line. The accumulator is operated as a dynamic damper at the traveling of a vehicle. This arrangement enables the construction of the communication line to be simplified, thus improving operability at assembling.

Hydraulic control device for working vehicle

A hydraulic ride control system for a working vehicle such as a wheel loader is provided with boom cylinders, an actuator control valve for controlling a pressure in bottom pressure chambers of the boom cylinders, an accumulator connected to the bottom pressure chambers of the boom cylinders via a connection line, an opening control valve having a pilot chamber to selectively communicating or cutting off the connection line depending on a pressure in the pilot chamber, and a selector unit for selectively feeding a pressure to or draining a pressure from the pilot chamber. The selector unit comprises a controller for variably controlling an opening of the opening control valve.

Hydraulic ride control system for working vehicle

Growing community of inventors

Kasumigaura, Japan

Yoshinobu Kobayashi