Hitachi Construction Machinery Co., Ltd.

Takeshi Kobayashi

Takashi Niidome

Kazuo Takiguchi

Mitsuhiro Yoshimoto

Hiroshi Matsuzaki

Katsumi Ueno

Ryouhei Yamashita

Hitoshi Kagiwada

Yoshinobu Kobayashi

Jun Okamura

Yoshifumi Takimoto

Yoshitomo Yabuuchi

Masaaki Andou

Masakazu Andou

A main spool () has a throttle passage () that, when the main spool () moves to an axial other side against a first return spring () in a main spool insertion hole (), communicates a pilot pressure chamber () with a first tank port () and limits a flow amount of hydraulic oil to be discharged to the first tank port () from the pilot pressure chamber (). When the main spool () moves to the axial other side along the main spool insertion hole (), the throttle passage () communicates the pilot pressure chamber () with the first tank port () before a state where a first pump port () is communicated with an output port () and a state where the output port () is blocked from the first tank port ().

Pressure reducing valve unit

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 motion converting section () and a translation bar () of a feedback mechanism () are provided between a lateral side of a swash plate () and a control sleeve () of a regulator (). When the swash plate () is in a neutral position, the motion converting section () is located in an initial position (F&#x2014;F) at one end of axial direction along an axis line (O&#x2014;O) passing through a tilting center (C) of tilting motions, and, when the swash plate () is driven to tilt in a forward or reverse direction, displaced to the other end of axial direction along the axis line (O&#x2014;O) to convert a tilting motion of the swash plate () into an axial displacement. Through the translation bar (), the axial displacement is transmitted to the control sleeve () of the regulator () as an axial displacement.

Inclined rotation control device of variable displacement hydraulic pump

A volume control valve for controlling the volume of a variable displacement type hydraulic rotary machine includes a valve housing provided with a bore in which a spool slides axially to selectively establish and block communication of a pressure oil feed/discharge port with a high pressure port and a tank port. A first pressure receiving portion is formed in the spool to receive a load pressure as a pilot pressure introduced from a pilot port for displacing the spool axially within the bore. A bottomed axial bore is formed in the spool which has a slidable piston therein defining an oil chamber between the piston end and the bottom of the bore to receive a hydraulic reaction force induced within the oil chamber. A second pressure receiving portion is formed by the bottom of the bore to receive an internal pressure of the oil chamber, thereby changing a total pressure receiving area of the spool in conjunction with the first pressure receiving portion. An oil passage is formed in the spool at a position corresponding to the oil chamber.

Volume control valve of variable displacement hydraulic rotating machine

Growing community of inventors

Kasumigaura, Japan

Takeshi Kobayashi