Hitachi Construction Machinery Co., Ltd.

Tsukasa Toyooka

Genroku Sugiyama

Toichi Hirata

Tsuyoshi Nakamura

Kouji Ishikawa

Youichi Kowatari

Makoto Sugaya

Kazunori Nakamura

Tsutomu Udagawa

Akira Nakayama

Hideaki Tanaka

Takatoshi Ooki

Yoichi Kowatari

Ei Takahashi

Nobuei Ariga

Eiji Egawa

Tadatoshi Shimamura

Shigehiro Yoshinaga

Kazuo Takiguchi

Koji Ishikawa

Masaki Egashira

Kensuke Satou

Masao Nishimura

Kensuke Sato

Akira Tatsumi

Makoto Matsushita

Masao Kariya

Yuuji Nagashima

Hidefumi Takegahara

Masao Kashiwagi

Hideo Sorata

Tarou Takahashi

Yasuharu Gotou

Ikuo Inagaki

Norio Onuma

Tsuyoshi Hitachi Kenki Tsukubaryo Nakamura

Masao Hitachi Kenki Tsukubaryo Nishimura

A travel control device for a work vehicle includes: a hydraulic pump; a plurality of hydraulic motors connected to the hydraulic pump in parallel through a closed-circuit connection, that drive different wheels with pressure oil delivered from the hydraulic pump; a slip detection device that detects a slip occurring at each of the wheels; and a flow control device that reduces, upon detection of a slip occurring at any of the wheels by the slip detection device, a quantity of pressure oil supplied to a hydraulic motor for driving the wheel at which the slip has been detected, among the plurality of hydraulic motors.

Travel control device for work vehicle and work vehicle

A travel drive system for a work vehicle includes: an HST drive device comprising a hydraulic pump driven by a prime mover and a hydraulic motor connected to the hydraulic pump by a closed circuit; an electric motor driven by using electric power generated by drive of the prime mover; a first drive wheel driven by the HST drive device; a second drive wheel driven by the electric motor; a vehicle speed detector that detects a vehicle speed; and a control unit that distributes output of the prime mover to the HST drive device and to the electric motor such that, as the vehicle speed detected by the vehicle speed detector increases, a proportion of a first power distributed to the HST drive device decreases and a proportion of a second power distributed to the electric motor increases.

Travel drive system for work vehicle, work vehicle, and travel drive method

A hydro-static transmission travel system for a working machine enables the working machine to travel over a range from low speed to high speed with a simplified circuit arrangement. By referring to a machine traveling speed (vehicle speed) based on a detected signal from a rotation sensor, a controller computes respective target tilting amounts of hydraulic motorsand controls the tilting amount for the hydraulic motors and a clutch. Depending on whether the traveling speed exceeds a setting speed as a reference boundary, the controller selectively switches over a drive mode between low-speed four-wheel drive, in which travel unitsare both driven, and high-speed two-wheel drive, in which the front-wheel side hydraulic motoris controlled to zero displacement and only the rear-wheel side travel unitis driven.

HST travel system for working machine

To permit smooth performance of both of an operation requiring a high pressure and an operation desired to produce a pressure at a suppressed level, a shuttle block positioned between pilot operating units and flow control valves and pump regulators is arranged in association with shuttle valves, which select maximum pressures of groups of operation signal pressures produced by the pilot operating units, respectively, and at least one of the plural groups of operation signals, and is constructed to include hydraulic selector valves and a boom-lowering, hydraulic selector valve that are operable in particular ways.

Hydraulic circuit device of hydraulic working machine

To keep one of three hydraulic pumps unaffected by variations in torque of the remaining hydraulic pumps when the three hydraulic pumps are used, displacements of the first and second hydraulic pumps are controlled based on their own delivery pressures P,Pand a pressure Pobtained by reducing through a reducing valvea delivery pressure Pfrom the third hydraulic pump, while a displacement of the third hydraulic pumpis controlled only by its own delivery pressure PThe pressure oil delivered from the third hydraulic pumptherefore, remains unaffected by variations in delivery flow rates from the first and second hydraulic pumpsin other words, by variations in their torque consumptions, so that the third hydraulic pump is assured to provide a stable flow rate.

Hydraulic circuit of construction machinery

A joining directional control valveis disposed to supply, to an arm cylindernot only a hydraulic fluid delivered from a first hydraulic pumpbut also a hydraulic fluid delivered from a second hydraulic pumpwhen an arm directional control valveis driven. Respective delivery pressures of the hydraulic pumpsare detected by pressure sensorsand the opening area of a recovery control valveis controlled depending on a lower one of the detected pressures from the pressure sensorssuch that, even in the combined operation of the arm cylinderand another actuatorthe hydraulic fluid can be recovered for return to the arm cylinderwhen the load pressure of the arm cylinderis low. Thus, by supplying the hydraulic fluids from the two hydraulic pumps to the particular actuator for which the hydraulic fluid is to be recovered, a recovery flow rate is ensured when the load of the particular actuator is low in the combined operation.

Oil pressure circuit for working machines

One of the mode lampsandof the mode indicatorcorresponding to the current steering mode is turned on yellow and the other mode lamps are turned on green or turned off, thereby indicating whether front wheelsand rear wheelsare at neutral. A controllerdoes not operate a mode changing valveeven with an instruction outputted from a mode change switchwhen the front and rear wheels are not at neutral, and operates, in response to an instruction outputted from the mode change switch, the mode changing valveto establish a steering mode corresponding to the instruction when the front and rear wheels are at neutral. Also, the mode indicatoris controlled to always indicate, as the current steering mode, one corresponding to the steering mode actually established by the mode changing valve. With those features, in a working vehicle in which the mode of steering front and rear wheels can be changed over between two-wheel steering and four-wheel steering, a steering system having superior operability and high reliability can be provided.

Steering system for working truck

To keep one of three hydraulic pumps unaffected by variations in torque of the remaining hydraulic pumps when the three hydraulic pumps are used, displacements of the first and second hydraulic pumps are controlled based on their own delivery pressures P, Pand a pressure P' obtained by reducing through a reducing valvea delivery pressure Pfrom the third hydraulic pump, while a displacement of the third hydraulic pumpis controlled only by its own delivery pressure P. The pressure oil delivered from the third hydraulic pump, therefore, remains unaffected by variations in delivery flow rates from the first and second hydraulic pumps, in other words, by variations in their torque consumptions, so that the third hydraulic pump is assured to provide a stable flow rate.

Pipe breakage control valve device

Provided are hydraulic pumps , a control valve group connected to the pump and including a bypass on/off valve , a control valve group connected to the pump and including a reserve-actuator-controlling, directional control valve , a communication line communicating a most upstream side of the control valve group with a supply line to the reserve-actuator-controlling, directional control valve , a merge control valve for communicating or cutting off the communication line , an interlocked control means for changing over the merge control valve to an open position and the bypass on/off valve to a closed position in association with a change-over operation of the reserve-actuator-controlling, directional control valve , and a selective control valve capable of taking one of a state, in which the operation to change over the merge control valve by the interlocked control means is feasible, and another state in which the operation to change over the merge control valve by the interlocked control means is infeasible. The control valve group , the control valve group , the communication line and the merge control valve are arranged in a housing such that a change or the like in a maximum value of an operating speed of an actuator, said operating speed being controlled by the reserve directional control valve, can be achieved.

Hydraulic driving device of civil engineering and construction machinery

A hose rupture control valve unit includes a housing provided with two input/output ports. One input/output port is directly attached to a bottom port of a hydraulic cylinder, and the other input/output port is connected to one of actuator ports of a control valve via an actuator line. Within the housing, there are provided a poppet valve body serving as a main valve, a spool valve body serving as a pilot valve which is operated with a pilot pressure supplied as an external signal from a manual pilot valve, thereby operating the poppet valve body, and a small spool having the function of an overload relief valve. The above construction reduces the number of components arranged in a flow passage through which a hydraulic fluid passes at a large flow rate, and hence a pressure loss. A further reduction in overall size and production cost of the valve unit is achieved.

Hose rupture control valve unit

A hydraulic drive system is provided with a signal guide system for guiding a delivery pressure of a pump as a command pressure via a line and a port, another signal guide system for guiding a pilot pressure of a pilot pump as another command pressure via a line and a port, a tilting control unit for controlling the displacement of the pump by the command pressures guided to the ports, a controller having a command current-setting unit for setting a relationship between a target engine speed and a command current, a target engine speed-indicating unit for an engine, and a solenoid-operated proportional valve for allowing the pilot pressure of the line to pass as is while no drive signal is outputted from the controller but for being reduced in opening to change the pilot pressure to a smaller value when a drive signal is outputted from the controller.

Hydraulic drive system for hydraulic work vehicle

A hydraulic drive system includes a closed center directional control valve connected to a hydraulic pump through a hydraulic fluid supply line and controlling a flow of a hydraulic fluid supplied to an actuator. A throttle and cutoff means for throttling and cutting off an unloading circuit depending on a operation amount of the directional control valve is installed in the unloading circuit interconnecting the hydraulic fluid supply line and a reservoir. The throttle and cutoff means comprises a logic valve including a feedback slit of which an opening area is increased and decreased depending on an amount by which a valve body is moved, and a pilot variable throttle for controlling a rate of a pilot flow passing the feedback slit depending on the operation amount of the directional control valve.

Hydraulic drive system and directional control valve apparatus in hydraulic machine

A tournament oil path constituting apparatus in which while a laminated block is constituted by laminating a number of oil path plates, a number of shuttle valve holes and connection grooves made continuous to the shuttle valve holes are formed at overlap faces of the oil path plates, shuttle valves are integrated to the shuttle valve holes, introductory oil paths communicating with the shuttle valve holes are formed at both of the oil path plates formed with the shuttle valve holes and the oil path plates having match faces on sides of the shuttle valve holes and a high pressure oil is selected by the shuttle valves from pressure oils conducted both of the introductory oil paths and conducted to the connection grooves. The tournament oil path constituting apparatus also including a number of main paths penetrating the number of laminated oil path plates and branch grooves branched from the main paths.

Tournament oil path constituting apparatus

Output correcting method in control system, control system, and

Growing community of inventors

Ibaraki-ken, Japan

Tsukasa Toyooka