Kubota Corporation

Daiki Abe

Ryota Hamamoto

Yuji Fukuda

Jun Tomita

Yuya Konishi

Hiroaki Nakagawa

Kazuki Ueda

Yuya Tanabe

Kohei Nagao

Masaki Inaoka

Ryosuke Kinugawa

Kohei Kurachi

Yudai Koga

Fumitaka Fujisawa

Keigo Honda

Yoshihiro Ebata

Yasuhiro Nishida

Hiroya Hanano

Yasushi Otagaki

Shun Tsuruta

Takumi Usui

Fumiya Kozono

Yuki Bunryo

A work vehicle includes a primary pressure control valve configured to control a pilot primary pressure of pilot oil. A secondary pressure control valve is configured to control a pilot secondary pressure of the pilot oil. Control circuitry is configured to control a rotation speed of an engine according to a target rotation speed. The control circuitry is configured to control the primary pressure control valve and the secondary pressure control valve based on a first target value of the pilot primary pressure and a second target value of the pilot secondary pressure.

Work vehicle and control method for work vehicle

A working machine includes a traveling pump to be operated by power of a prime mover and deliver a hydraulic fluid; a traveling motor that rotates using the delivered hydraulic fluid; an operation valve that changes pilot pressure of a pilot fluid outputted to the traveling pump in response to operation of an operation member; an actuation valve that operates based on a control signal and changes primary pressure that is the pilot pressure of the pilot fluid supplied to the operation valve; a controller that controls opening of the actuation valve by outputting the control signal to the actuation valve; and a first detector that detects an actual number of revolutions of the traveling motor. The controller includes a changer that changes setting of the control signal such that the opening of the actuation valve increases as the actual number of revolutions of the traveling motor decreases.

Working machine including a controller configured to control an actuation valve based on traveling motor revolutions

A working machine includes a prime mover, a traveling pump driven by power of the prime mover to deliver hydraulic fluid, a traveling motor rotated by the hydraulic fluid delivered from the traveling pump, an operation valve configured to change a pilot pressure of pilot fluid output therefrom to the traveling pump according to operation of an operation member, an actuation valve to be activated according to a control signal so as to change a primary pressure supplied to the operation valve, a controller to perform setting of the control signal to be output to the actuation valve, and a pressure detection device to detect a secondary pressure output from the operation valve. The controller includes a setting change unit to change, based on the primary pressure and the secondary pressure, the setting of the control signal to be output to the actuation valve.

Working machine

A work vehicle includes a primary pressure control valve configured to control a pilot primary pressure of pilot oil. A secondary pressure control valve is configured to control a pilot secondary pressure of the pilot oil. Control circuitry is configured to control a rotation speed of an engine according to a target rotation speed. The control circuitry is configured to control the primary pressure control valve and the secondary pressure control valve based on a first target value of the pilot primary pressure and a second target value of the pilot secondary pressure. The control circuitry is configured to reduce the first target value and the second target value such that the second target value is higher than the first target value when the rotation speed of the engine detected by a rotation speed sensor becomes lower than the target rotation speed by a predetermined speed difference or more.

A method for controlling a work vehicle includes driving a first hydraulic pump and a second hydraulic pump by an engine to supply hydraulic fluid to a first hydraulic motor and a second hydraulic motor, respectively, to drive a first traveling device and a second traveling device, respectively. An operation state of a direction input device to operate a traveling direction of the work vehicle is detected. Based on the operation state detected, whether or not a traveling state of the work vehicle is a turning state. When it is determined that the traveling state is the turning state, a rotation command to decrease a target rotational speed of the engine from a first rotational speed to a second rotational speed is output.

Work vehicle and method for controlling work vehicle

A working machine includes a controller that performs shift shock reduction control when shift-down switching from a second state to a first state, in which a motor speed can be increased up to a first maximum speed lower than a second maximum speed available in the second state, is performed. The controller includes a first processor configured to, based on a drop amount that is a difference between target and actual numbers of revolutions of a prime mover, compute a first reduction amount for reducing an amount of hydraulic fluid supply from a traveling pump to a traveling motor, a second processor configured to compute a second reduction amount based on a degree of straight traveling of a machine body, and a reduction controller configured to, based on the first or second reduction amount, whichever is larger in absolute value, perform the shift shock reduction control.

A working machine includes a prime mover, a hydraulic pump driven by power of the prime mover, a cooler including a cooling fan rotated by either the power of the prime mover or hydraulic fluid delivered from the hydraulic pump, and a controller configured or programmed to perform a reduction control for reducing a target fan rotation speed that is a target rotation speed of the cooling fan in response to reduction of an actual prime mover rotation speed that is an actual rotation speed of the prime mover, and to perform, after the reduction control, a restoration control for restoring the target fan rotation speed. The controller is configured or programmed to make a difference between a reduction rate of the target fan rotation speed in the reduction control and an increase rate of the target fan rotation speed in the restoration control.

A hydraulic system for a working machine includes: a first hydraulic pump; a first hydraulic device; a hydraulic fluid tank; a first discharge fluid passage to allow hydraulic fluid discharged from the first hydraulic device to flow into the tank; a second hydraulic pump to suck fluid from the tank through a suction fluid passage; a second hydraulic device in which difference between flow rate of fluid from the second hydraulic pump device and that of discharged fluid changes according to actuation; a second discharge fluid passage connected to a suction port of the first hydraulic pump and allowing fluid discharged from the second hydraulic device to flow into the first hydraulic pump; a connecting fluid passage branching from the second discharge fluid passage and connected to the suction fluid passage between the tank and the second hydraulic pump; a supplier to supply fluid to the second discharge fluid passage.

Hydraulic system for working machine, and working machine

A working machine includes a prime mover, a rotation-speed operation actuator, a rotation detector, a hydraulic pump, a hydraulic unit, an operation valve capable of changing a pilot pressure of a pilot fluid supplied from the hydraulic pump to the hydraulic unit in accordance with an operation of an operation member, an actuation valve operating in accordance with a control signal and capable of changing a primary pressure as the pilot pressure of the pilot fluid supplied from the hydraulic pump to the operation valve, and a controller that outputs the control signal based on a difference between target and actual rotation speeds to the actuation valve to control an opening thereof. The controller has a mode including calculating the control signal based on the difference, correcting the calculated control signal, and increasing or decreasing a target primary pressure value set in accordance with the control signal.

Prime mover speed control for hydrostatic working machine

A working machine includes a first traveling fluid passage connected to a first pressure-receiving portion, a second traveling fluid passage connected to a second pressure-receiving portion, a third traveling fluid passage connected to a third pressure-receiving portion, a fourth traveling fluid passage fluidly connected to a fourth pressure-receiving portion, and a connection fluid passage connecting at least two of the first, second, third and fourth pressure-receiving portions to each other. When a traveling operation member is operated, operation fluid flows to the first pressure receiving portion through the first traveling fluid passage, to the second pressure receiving portion through the second traveling fluid passage, to the third pressure receiving portion through the third traveling fluid passage, and to the fourth pressure receiving portion through the fourth traveling fluid passage.

A control method for a fan of a work vehicle includes supplying, when an engine is started, a first current to a solenoid of a variable relief valve such that the hydraulic fluid flows by a first flow rate, supplying, when a rotational speed of the engine becomes larger than a first rotational speed threshold value, a second current larger than the first current to the solenoid such that the hydraulic fluid flows by a second flow rate smaller than the first flow rate to reduce the rotational speed of the fan, and supplying, when the rotational speed of the engine becomes larger than a second rotational speed threshold value that is larger than the first rotational speed threshold value, a current to the solenoid to change the rotational speed of the fan, the current corresponding to a temperature of liquid flowing in the work vehicle.

Work vehicle and control method for fan of work vehicle

A working machine includes: a machine body provided thereon with a traveling pump and a traveling motor; a traveling change-over valve shiftable between a first state where a rotation speed of the traveling motor is set to a first speed and a second state where the rotation speed is set to a second speed; an actuation valve operable to control a flow of operation fluid to an operation valve that changes a pressure of operation fluid to be applied to the traveling pump according to operation of an operation member; and a controller to perform a shock-mitigation control for reducing an opening degree of the actuation valve when the traveling change-over valve is shifted from the first state to the second state. The controller determines a reduction amount of the opening degree of the actuation valve reduced by the shock-mitigation control, based on a straight-traveling degree of the machine body.

A working machine includes a prime mover, a traveling pump driven by a power of the prime mover to deliver operation fluid, a traveling motor rotated by the operation fluid delivered from the traveling pump to have a rotation speed stage shiftable between a first speed stage and a second speed stage higher than the first speed stage, a traveling switching valve shiftable between a first state where the rotation speed stage of the traveling motor is set to the first speed stage and a second state where the rotation speed stage of the traveling motor is set to the second speed stage, an actuation valve configured to change a pilot pressure of a pilot fluid to control a flow of operation fluid delivered from the traveling pump, and a controller configured to control the pilot pressure of the pilot fluid output from the actuation valve so that a value of the pilot pressure differs depending on whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage.

A work machine includes a first oil passage connecting a first hydraulic pump and a first chamber of a bucket cylinder, a fourth oil passage connecting an arm control valve and a fourth chamber of an arm cylinder, a bypass oil passage connecting the fourth oil passage and the first oil passage, and a switching mechanism configured to control connection/disconnection of the fourth oil passage to/from the first oil passage via the bypass oil passage. Circuitry is configured to determine whether an uptilt operation to raise the arm and to tilt the bucket downward has been performed based on outputs of an arm operation detection sensor and a bucket operation detection sensor, and to control the switching mechanism to connect the fourth oil passage and the first oil passage when it is determined that the uptilt operation has been performed.

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Sakai, Japan

Daiki Abe