Hitachi Construction Machinery Co., Ltd.

Kcm Corporation

Masaki Nukii

Koji Hyodo

Tetsuji Tanaka

Isamu Aoki

Yasunori Miyamoto

Masashi Yamashita

Fumihiro Nakao

Yuki Ahiko

Masaki Yoshikawa

Katsutaka Hara

Keisuke Naitou

Provided is a work vehicle capable of attaining a maximum vehicle speed specification value set in advance for each vehicle body even in the case where a device constituting an HST traveling drive system has deteriorated over time. In a wheel loaderequipped with an HST traveling drive system, a controlleris configured to, in the case where a detection pressure value P is equal to or less than a switching pressure value Ps corresponding to a switching point in the HST motorbetween a maximum displacement volume qmax and a minimum displacement volume qmin, and a detection vehicle speed value V is less than an upper limit vehicle speed specification value Vmaxs, limit the minimum displacement volume qmin of the HST motorto a first minimum displacement volume value qminless than a minimum displacement volume specification value qmins that is associated with the upper limit vehicle speed specification value Vmaxs.

Work vehicle

Provided is a loading work vehicle capable of improving work efficiency even when working on a slippery road surface. An HST-traveling-drive wheel loadercomprises a step-on amount detection sensor, a discharge pressure detection sensor, a mode switch device, and a controller. The controlleris configured to: determine whether a limit mode is selected by the mode switch device; specify an operation state of the wheel loaderwhen determining that the limit mode is selected; limit maximum traction force to a first set value which is set based on a static friction coefficient μ and vehicle weight when specifying that a bucketis pushed into a natural ground; and increase the maximum traction force from the first set value when specifying that excavation of the natural groundis started.

Loading work vehicle

Provided is a wheel loader capable of automatically decreasing vehicle speed without making an operator feel discomfort during a loading operation. A wheel loadermounted with a torque converter type traveling drive system comprises a controllerconfigured to control shifting of a transmission. When a vehicle body travels forward at vehicle speed corresponding to a second speed stage set greater by one speed stage than the lowest speed stage of the transmissionwhile operating the lift armupwardly, the controllersets, as a gear ratio of the transmission, an intermediate gear ratio between a gear ratio corresponding to the second speed stage and a gear ratio corresponding to a first speed stage, and outputs a signal for selecting a combination of a plurality of gears corresponding to the set gear ratio to each first to fifth solenoid control valvesA toE.

Wheel loader

A loading vehicle is capable of improving work efficiency by adjusting engine rotational speed with high accuracy in accordance with an operation state of the working device. An HST traveling driven wheel loader has an electrically controlled HST pump. A controller is configured to control input torque of the HST pumpand solenoid proportional pressure reducing valve is configured to generate control pressure for controlling displacement volume of the pump based on a control signal from the controller. The controller is configured to calculate the displacement volume q of the HST pump based on discharge pressure Pf of a loading hydraulic pump so that maximum input torque Thst of the HST pump decreases as the discharge pressure Pf or input torque of the loading hydraulic pump increases, and output a control signal corresponding to the calculated displacement volume q to the solenoid proportional pressure reducing valve.

Loading vehicle

A wheel loader is provided that can suppress abrupt change in vehicle speed accompanied by erroneous determination on a lift arm lifting operation. A wheel loader includes: an engine; an HST pump; an HST motor; a forward and reverse switch; a stepping amount sensor; an operation amount sensor; and a controller. The controller determines whether a specific condition for specifying an operation of the lift arm in an upper direction during forward travel of the vehicle body, on the basis of a forward and reverse switching signal, the stepping amount, and a pilot pressure pertaining to the lifting operation for the lift arm. In a case of the specific condition being satisfied, the vehicle speed is limited by controlling the displacement volume of the HST motor in conformity with increase in the pilot pressure.

Provided is a loading vehicle in which a control characteristic of traction force can be easily and finely set and changed while a configuration of a hydraulic circuit is simple. An HST traveling driven wheel loader includes an electronically controlled HST pump and HST motor, including a solenoid proportional pressure reducing valve to control displacement volume of the HST pump based on a control signal output from a controller. The controller stores characteristic tables indicating a correlation between discharge pressure of a loading hydraulic pump or an operation state of an engine and a maximum discharge pressure of the HST pump, and when the vehicle speed corresponds to work requiring traction force, outputs a control signal to the solenoid proportional pressure reducing valve so as to obtain the maximum discharge pressure Pm of the HST pump that corresponds to one of the characteristic tables.

To curb temperature rises in a control device for a supercharger and extend the life of the control device for the supercharger, a work vehicle includes a variable geometry supercharger with variable boost pressure, and a working device driven by pressure oil discharged from a working hydraulic pump, the work vehicle further including: a supercharger control device adapted to control the supercharger; a temperature detection device adapted to detect temperature of the supercharger control device; and a main control device adapted to limit at least one of maximum rotational speed of an engine and maximum vehicle speed of the work vehicle in case the temperature of the supercharger control device is above a predetermined temperature as compared to case the temperature of the supercharger control device is below the predetermined temperature.

Provided is a working vehicle capable of, while reducing fuel consumption, improving traveling performance only when high traveling performance is required. A wheel loadercomprises: an engine; a variable displacement HST pump; a variable displacement HST motorconnected to the HST pumpthrough a closed circuit; pressure sensorsA,B configured to load pressure of the HST motor; and a controller, wherein the controlleris configured to, in a case of determining that a load pressure detection value P is included in a predetermined pressure range of greater than load pressure P&#x3b1; corresponding to flat ground traveling and smaller than load pressure P&#x3b3; corresponding to an excavation operation, increase maximum rotational speed of the engineonly within the predetermined pressure range.

Working vehicle

Provide is a loading vehicle capable of quickly operating an object handling device in the upward direction while traveling forward. A wheel loadercomprises an engine, an HST pump, an HST motor, a forward/reverse changeover switch, a step-on amount sensor, a pressure sensor, and a controller. In a case where a specific condition for specifying lifting operation of a lift armduring forward traveling of the vehicle body is satisfied, the controllerincreases maximum rotational speed of the engine to a predetermined value Nmaxwhich is greater than maximum engine rotational speed Nmaxduring traveling on the flat ground, and limit maximum vehicle speed to a predetermined value Vmaxwhich is smaller than maximum vehicle speed Vmaxprior to the lifting operation of the lift arm

The present invention relates to a work vehicle including an engine, a hydraulic pump, a hydraulic motor to drive wheels, an HST circuit in which the hydraulic pump and the hydraulic motor are connected to each other in the form of a closed circuit, a reducing agent sensor that detects the state of a reducing agent used to clean exhaust gas from the engine, and an engine restrictor that restricts the rotational speed of the engine based on the output from the reducing agent sensor, and the work vehicle further includes a control unit that changes the tilting angle of the hydraulic pump or the hydraulic motor independently of the rotational speed of the engine to a tilting angle associated with minimum travel drive force necessary for self-travel of the work vehicle when the control unit determines that the engine restrictor has restricted the rotational speed of the engine.

A prime mover control device of a work vehicle equipped with a torque converter includes: a speed ratio calculation unit that calculates a speed ratio of the torque converter; and a rotational speed limit unit that, when a speed ratio falls within a preset speed ratio range, limits a maximum rotational speed of the prime mover to be lower as compared with a maximum rotational speed set when a speed ratio falls without the preset speed ratio range. When a state in which the speed ratio calculated by the speed ratio calculation unit falls within the preset speed ratio range is maintained for a predetermined time period, the rotational speed limit unit changes a maximum rotational speed of the prime mover to a higher maximum rotational speed than the limited maximum rotational speed limited to be lower by the rotational speed limit unit.

Growing community of inventors

Ushiku, Japan

Masaki Nukii