Hitachi Construction Machinery Co., Ltd.

Youichi Kowatari

Kouji Ishikawa

Genroku Sugiyama

Toichi Hirata

Tsukasa Toyooka

Hidetoshi Satake

Kazunori Nakamura

Katsuaki Kodaka

Kazuhiro Ichimura

Yuuki Gotou

Shigehiro Yoshinaga

Tsuyoshi Nakamura

Hidenobu Tsukada

Masaki Yoshikawa

Hideo Karasawa

Nobuei Ariga

Yasuo Okano

Hidefumi Takegahara

Shigetoshi Konno

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

A pump torque control system is capable of preventing hunting due to interference between speed sensing control and control of an engine speed of a prime mover when the temperature of a hydraulic fluid is low. A maximum absorption torque is set in a regulatorthat controls displacement volumes of hydraulic pumpsandbased on a deviation between target and actual engine speeds of a prime mover. A second modification factor calculating sectionand a control gain modifying section, which are included in a controllerthat performs speed sensing control to ensure that the maximum absorption torque of the hydraulic pumpsandis reduced, change a control gain of the speed sensing control based on a value detected by the hydraulic temperature sensorto ensure that the control gain is reduced as the temperature of the hydraulic fluid is reduced.

Pump torque control system for hydraulic construction machine

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 work machine gear shifting control system provides gear shifting conditions for an automatic gear shifting mode in accordance with work site conditions. An areaof a display devicedisplays a permissible velocity setting range and setup operation guidance, and another areashows guidance to indicate whether the setting is acceptable or unacceptable. When the traveling velocity falls within the permissible velocity setting range, the displayed guidance changes to indicate that the setting is acceptable. When, in this instance, an operator presses a setup switchwith desired timing, a transmission gear shifting control sectionacquires the prevailing vehicle velocity and velocity ratio (or vehicle velocity), and stores adjustment values in an adjustment value storage sectionso that the vehicle velocity and velocity ratio become the gear shifting control threshold values for normal gear shifting control (steps Sto S).

Gear shifting control system for work machine

A work machine gear shifting control device is capable of readily identifying the cause of failure in learning the clutch hydraulic pressure for operating a transmission clutch. A transmission gear shifting control sectionis provided for each of clutches-, and performs a learning process in which each of a plurality of handling processes learns the clutch hydraulic pressure for each of the clutches-and determines the clutch hydraulic pressure characteristic values for operating the individual clutches. Further, the transmission gear shifting control sectionperforms a learning monitoring process in each of the plurality of handling processes to formulate an error judgment, which indicates whether learning has failed in each of the plurality of subprocesses, and displays the result of the judgment.

Gear shifting control device for work machine

Output correcting method in control system, control system, and

An engine torque, which corresponds to a target engine speed inputted in a controller, is determined by a functional computing function unit. A torque correction value is added to the engine torque, followed by the multiplication with a constant. The product is divided by a pump delivery pressure to determine a pump displacement. A target tilting corresponding to this value is determined by another functional computing function unit, and is then compared with another target tilting which has been determined from a negative control pressure. The smaller one is selected and is outputted as a target tilting. The torque correction value is set at an EEPROM through an input device as desired. Selection of a negative value as the torque correction value makes it possible to prevent occurrence of stalling.

Pump torque control system

A pilot pressure sensor detects a pilot pressure from an arm operating unit and outputs a pilot pressure signal. A drive signal corresponding to the pilot pressure signal is then outputted from a controller to a solenoid-operated proportional valve. Through the solenoid-operated proportional valve, a pilot pressure is fed to an auxiliary selector valve so that an opening of said auxiliary selector valve becomes greater. Of pressure oil delivered from a first hydraulic pump, a flow rate of the pressure oil to be branched to a side of a by-pass circuit is hence increased. The pressure oil fed through the by-pass circuit passes through a merging directional control valve and is caused to merge with pressure oil fed from a second hydraulic pump. The thus-merged pressure oil is then fed to a hydraulic arm cylinder.

Hydraulic by-pass circuit for a hydraulic shovel

A hydraulic system for a construction machine includes a hydraulic pump driven by a prime mover, actuators driven by a hydraulic fluid delivered from the hydraulic pump, flow control valves for controlling flow of the hydraulic fluid to the actuators and operation means for operating the flow control valves. A relief value sets a relief pressure for limiting the maximum delivery pressure of the hydraulic pump and relief pressure change means increase or decrease the relief pressure set by the relief valve. The relief pressure change means automatically increase or decrease the relief pressure in accordance with the input amount of the operation means.

Hydraulic drive system for construction machines

A controller 520 has a data portion 520c in which the relationship between a pump delivery pressure and a target opening area of a variable throttle 300a of a control valve 300 is set such that the target opening area is large when the pump delivery pressure is low, and small when the pump delivery pressure is high. An input portion 520a takes in a detection signal from a pump pressure sensor 700, a processing portion 520b reads the data from the data portion 520c and calculates a signal output to a solenoid proportional valve 590, and an output portion 520d converts the calculated signal into a command signal for the solenoid proportional valve 590 and outputs the command signal. Upon receiving the command signal from the controller 520, the solenoid proportional valve 590 produces a command pilot pressure for the control valve 300 corresponding to the input signal and controls the opening area of the variable throttle 300a.

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Kasumigaura, Japan

Youichi Kowatari