Hitachi Construction Machinery Co., Ltd.

Kazuhiro Ichimura

Hidetoshi Satake

Katsuaki Kodaka

Yukihiro Tatsuno

Yuuki Gotou

Akira Tatsumi

Youichi Kowatari

Seiji Tamura

Mitsuo Kihara

Hiroshi Tsukui

Hiroshi Onoue

Junichi Hosono

Yuuji Nagashima

Kazuo Asano

Kentaro Itoga

Shigetaka Nakamura

Toshihiko Shinya

Hideki Haramoto

Hideaki Sayama

Wataru Kondou

Saburo Yoshio

Akiko Yoshio, Legal Representative

An object is to reduce a load acting on an engine upon starting up the engine such that the engine can be quickly started up to reliably feed pressure oil from a hydraulic pump to an accumulator. A hydraulic control system is provided with first accumulators () connected to a hydraulic pump () via a first line () and second accumulators () connected to a second line () branching from the first line (), an on/off valve () arranged in the second line and interposed between the first line () and the second accumulators (), an operation detection device () for detecting whether or not a starter () is in an operation state, a rotational frequency detection device (a rotary encoder () and rotational frequency calculation device ()) for detecting a rotational frequency of an engine (), and a valve control device for, upon detection of the operation state of the starter () by the operation detection device (), controlling a valve position of the on/off valve () at a closed position until the rotational frequency reaches an idling rotational frequency set beforehand but then controlling the valve position of the on/off valve () at a closed position.

Hydraulic control device of wheeled industrial vehicle

There are provided: control valves-that control flow of pressure oil from the hydraulic sourceto the hydraulic actuators-; electric lever devices-that output electrical operation signals v-vin correspondence to lever operation; electromagnetic proportional valves-through which control pressures for controlling the control valves-are output; a pressure calculating unitthat calculates control pressures P-Pin correspondence to the operation signals V-v; a control unitthat controls the electromagnetic proportional valves-so that control pressures to be output from the electromagnetic proportional valves-become the control pressures P-Pthat have been calculated; a high-pressure selection circuit-that selects a higher pressure between control pressures that have been output from the electromagnetic proportional valves-; pressure detectorsandthat detect a control pressure selected by the high-pressure selection circuit-; an abnormality determination unitthat determines an abnormality in the electromagnetic proportional valves-based upon the control pressure detected by the pressure detectorsandand the control pressure calculated by the pressure calculating unit; and an inhibiting deviceandthat prohibits control of the control valves-when it is determined that an abnormality has occurred in the electromagnetic proportional valves-

Safety device for hydraulic working machine

A prime mover rotation speed control system for hydraulically driven vehicle includes: a hydraulic pump driven by a prime mover; a hydraulic motor for traveling driven with pressure oil supplied from the hydraulic pump; an operation member that outputs a travel command in accordance with an amount of operation by the operation member; a flow control device that controls one of a flow of the pressure oil from the hydraulic pump to the hydraulic motor and a flow rate of the pressure oil discharged from the hydraulic motor, based on the travel command that is output in accordance with the amount of operation by the operation member; a target rotation number outputting device that outputs a target rotation number of the prime mover based on a command; a rotation number control device that controls a rotation number of the prime mover to be the target rotation number; a vehicle speed detection device that detects a vehicle speed; and a vehicle speed calculation device that calculates a target vehicle speed in accordance with the amount of operation by the operation member. The rotation number control device includes a correction device that adjusts the target rotation number based on the vehicle speed detected by the vehicle speed detection device and the target vehicle speed calculated by the vehicle speed calculation device.

Prime mover rotation speed control system for hydraulically driven vehicle

The present invention includes a hydraulic brake devicethat generates a braking force corresponding to an operation of a brake pedalperformed while the vehicle is traveling, a brake lock meansfor applying a hydraulic lock on the hydraulic brake deviceand releasing the hydraulic lock, a brake pedal operation detection meansfor detecting an operation of the brake pedal, and a control meansfor controlling the brake lock meansso as to apply the hydraulic lock on the hydraulic brake deviceupon detecting via the brake pedal operation detection meansa predetermined depressing operation of the brake pedal

Work vehicle control device

There are provided: control valves-that control flow of pressure oil from the hydraulic sourceto the hydraulic actuators-; electric lever devices-that output electrical operation signals, which are drive instructions for the hydraulic actuators-, in correspondence to lever operation; and a control unit-andthat controls the control valves-in correspondence to the operation signals. When the determination unit determines that an operation signal is not within the normal range, the hydraulic actuators-are allowed to be driven with flow of pressure oil to the hydraulic actuators-limited more significantly than in a case where it is decided that an operation signal is within the normal range.

A control system for a work vehicle includes: a negative-type parking brake device that starts operating in response to a parking brake instruction; an output device that outputs the parking brake instruction; a service brake device that operates in response to an operation of a brake pedal by an operator; and a brake control device that operates the service brake device regardless of a pedal operation by the operator when the parking brake instruction is output from the output device.

Control system for work vehicle

A pedal lock control device for work vehicle includes: a motor driving device that drives a travel hydraulic motor in response to an operation amount of a travel pedal; a locking device that locks the travel pedal in a state of being operated; an instruction device that instructs lock and unlock of the travel pedal by the locking device upon an operation by an operator; a first detection device that detects a first signal change according to an unlock operation which is an operation that reflects an intention of an operator to release the locking device and is other than an unlock operation by the instruction device; a second detection device that detects a second signal change according to an unlock operation which is an operation that reflects an intention of an operator to release the locking device and is other than the unlock operation by the instruction device, with the second signal change being different from the first signal change; and a lock control device that unlocks the locking device when an unlock operation is detected by at least one of the first detection device and the second detection device in a state where the travel pedal is locked by the locking device.

Pedal lock control device for work vehicle

A pedal lock control device for work vehicle includes: a motor driving device that drives a travel hydraulic motor according to an operation amount of a travel pedal; a locking device that locks the travel pedal in a state of being operated; an instruction device that instructs lock and unlock of the travel pedal by the locking device upon an operation by an operator; a lock intention detection device that detects an intention of an operator to permit lock of the travel pedal; and a lock control device that locks the travel pedal by the locking device when an intention of the operator to permit lock is detected by the lock intention detection device and lock of the travel pedal is instructed by the instruction device.

A rotational speed pickup(traveling speed detection means), a hydraulic pressure sensor(traveling operation detection means), a hydraulic pressure sensor(drive status detection means), and a voltage sensor(transmission shift position detection means) detect parameters regarding the traveling state of a hydraulic traveling vehicle. A control unit, a solenoid proportional valve, an engine control system, and a motor regulatordetermine the operating state of the hydraulic traveling vehicle based on the parameters regarding the traveling state, and control the equivalent displacement of the traveling system including a hydraulic traveling motorand the maximum flow rate supplied to the hydraulic traveling motoraccording to the result of determination. The pump flow rate and motor displacement are controlled according to the traveling state in this way, thereby ensuring favorable traveling performance without degrading the fuel efficiency.

Traveling control apparatus for hydraulic traveling vehicle

A prime mover control device of a construction machine includes a hydraulic pump () driven by a prime mover (), an actuator () driven with pressure oil discharged from the hydraulic pump (), and a control valve () that controls a flow of the pressure oil from the hydraulic pump () to the actuator () in response to an operation of a first operating member (). The prime mover control device includes a first set means () that sets a first set rotation speed Nt of the prime mover () according to the operation of the first operating member (), a second set means () that sets a second set rotation speed Nx of the prime mover () according to an operation of a second operating member (), a selection member () that selects one of a first mode and a second mode, and a rotation speed control means () that controls a prime mover rotation speed to match with a maximum value of the first set rotation speed Nt and the second set rotation speed Nx when the selection member () selects the first mode, and controls the prime mover rotation speed to match with the second set rotation speed Nx when the selection member () selects the second mode.

Prime mover control device of construction machine

An engine control device for a work vehicle includes a hydraulic pump driven by an engine, a hydraulic actuator driven with pressure oil supplied from the hydraulic pump, a drive disallower for disallowing drive of the hydraulic actuator with the pressure oil supplied from the hydraulic pump, a disallowed drive detector for detecting whether or not the drive disallower is disallowing the drive; and a rotation rate controller for executing control so as to adjust an engine speed to a low rotation rate, lower than a minimum rotation rate (hereafter referred to as a low idle rotation rate) at which the hydraulic actuator can still be driven, at least when the disallowed drive detector detects that the drive disallower is disallowing the drive.

Engine control device for work vehicle

The present invention includes: a hydraulic pumpthat is driven by a driving motor; a travel motion motorthat is driven with pressure oil supplied from the hydraulic pump; a travel motion control valvethat controls a flow rate of the pressure oil supplied from the hydraulic pumpto the travel motion motor; a means for operationwith which the travel motion control valveis operated; a means for rotation rate detectionthat detects a rotation rate N of the travel motion motor; and a means for motor over rotation preventionthat reduces the rotation rate of the travel motion motorif the means for rotation rate detectiondetects a rotation rate equal to or higher than a predetermined rotation rate upper limit Nmax.

Travel motion control apparatus for hydraulically driven vehicle, hydraulically driven vehicle and wheel hydraulic excavator

An operation circuit for a work vehicle drives an electromagnetic actuator by generating an operation signal corresponding to a switch operation and drives a work actuator in response to the drive of the electromagnetic actuator. By installing a specific detachable electric circuit unit in a first operation circuit that generates a first operation signal in response to an operation of a specific switch, the first operation circuit can be modified to a second operation circuit that generates a second operation signal different from the first operation signal in response to an operation of the same switch.

Operation circuit for a work vehicle

The present invention includes a hydraulic pump (), a variable displacement hydraulic motor () for traveling driven by pressure oil from the hydraulic pump (), a motor displacement control means () for adjusting a displacement of the hydraulic motor () in correspondence to a drive pressure at the hydraulic motor (), an operating member () through which a forward travel command and a backward travel command for the vehicle are issued, a control means () to be driven in response to an operation of the operating member (), for controlling a flow of pressure oil from the hydraulic pump () to the hydraulic motor (), a reverse operation detection means (A,B) for detecting a reverse operation of the operating member () performed to a reverse side opposite from a direction along which the vehicle is advancing, and a cavitation preventing means (A,B) engaged in operation so as to prevent occurrence of cavitation at the hydraulic motor () when the reverse operation at the operating member () is detected by the reverse operation detection means (A,B).

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Niihari-gun, Japan

Kazuhiro Ichimura