Hitachi Construction Machinery Co., Ltd.

Katsumi Ueno

Hiroshi Matsuzaki

Yoshinobu Kobayashi

Masami Ochiai

Takashi Yagyu

Tsutomu Udagawa

Mitsuhisa Tougasaki

Kazuo Takiguchi

Mitsuo Aihara

Kazuyuki Ino

Yukihiko Sugiyama

Takeshi Kobayashi

Ryouhei Yamashita

Masaaki Andou

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 control valve has a pressure chambercausing a pressure to act on a valve elementof a check valvean oil chamberaround the valve, a slotformed in the valve elementand interconnecting the oil chamberand the pressure chamberwith each other and, a control valveconnected directly to a divergence portionand the oil chamberand capable of permitting or cutting off communication between the divergence portionand the oil chamberand changing an opening degree of the communication, an intra-valve-element passage, a slotformed in an outer peripheral wall of the valve elementand communicating the passageand the chamberwith each other, and a spring-return auxiliary check valvefor allowing pressure oil to flow from a supply passageinto the intra-valve-element passage

Directional control valve device and directional control valve device block having directional control valve devices

A pressure selector valve () is provided between a hydraulic motor () and a directional control valve () to connect one of the main conduits (A), (B) on a high pressure side to a high pressure conduit () while connecting the other of the main conduits on a low pressure side to a low pressure conduit (). As an inertial body approaches a stop position, a spool valve () is switched to an open position (e), bringing a branch passage (A) of the high pressure conduit () into communication with the low pressure conduit. When the pressure difference between the main conduits becomes small, the pressure selector valve is automatically returned to a neutral position to cut off communication between the main conduits, suppressing a reversing movement of the hydraulic motor so that an inertial body can be brought to a stop smoothly.

Inertial body drive system

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

The control valve apparatus holds a seat valve member in a position seated on a valve seat to thereby prevent a backward flow even if the pressure in the inlet chamber side becomes lower than the pressure in the outlet chamber side. With a pilot control valve member is in a closed state, when the pressure in the inlet chamber is higher, a pressurized medium is introduced to the control pressure chamber via a first valve unit and is cut off from the outlet chamber by a second valve unit. When the pressure in the outlet chamber is higher, the pressurized medium is introduced to the control pressure chamber via the second valve unit and is cut off from the outlet chamber by the first valve unit.

Control valve apparatus and pressure circuit

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Tsuchiura, Japan

Katsumi Ueno