Abstract: A work vehicle includes a speed limit calculation portion, a speed determination portion, an adjustment portion, and a boom speed determination portion. The speed limit calculation portion calculates a speed limit for limiting a speed of a cutting edge of a bucket. The speed determination portion determines whether or not a speed of raising the boom has been lowered when an amount of operation of an arm is smaller than a prescribed amount. The adjustment portion delays speed change to the speed limit. The boom speed determination portion determines a target speed of the boom based on the speed limit after delay by the adjustment portion when it is determined that the speed of raising the boom has been lowered, and determines a target speed of the boom based on the speed limit calculated when it is not determined that the speed of raising the boom has been lowered.

Abstract: A work vehicle includes a boom, an arm, a bucket, an arm control member, a speed limit determination portion, and a target speed determination portion. The speed limit determination portion determines a speed limit for limiting a speed of a cutting edge of the bucket in accordance with a distance between a cutting edge and a design surface. The target speed determination portion determines a target speed of the boom based on the speed limit. The speed limit determination portion decides on a speed limit calculated based on correlation between the speed limit and the distance between the design surface and the cutting edge when an amount of operation of the arm control member is equal to or greater than a prescribed amount and decides on a speed limit lower than the speed limit calculated based on the correlation when the amount of operation is smaller than the prescribed amount.

Abstract: There is provided a work vehicle in which a work implement can be freely operated. The work vehicle includes: a design surface information acquiring unit for acquiring data of a design surface indicative of a target shape of a work object by the work implement; a cutting edge position computing unit for computing a position of a cutting edge of a bucket; and an operation restricting unit for executing operation restriction control by which, when the cutting edge of the bucket comes closer to the design surface, operation of the work implement is stopped before the cutting edge of the bucket reaches the design surface. In a case where the cutting edge is located away from the design surface in a downward perpendicular direction by a prescribed distance or longer, the operation restricting unit does not execute the operation restriction control.

Abstract: There is provided a hydraulic excavator in which invasion of a design surface by a work implement can be suppressed. A boom-lowering proportional solenoid valve is provided in a boom-lowering pilot conduit connected to a boom-lowering pilot port. A first pressure sensor detects a pressure generated in the boom-lowering pilot conduit between a control lever and the boom-lowering proportional solenoid valve. A controller controls an opening degree of the boom-lowering proportional solenoid valve based on the pressure detected by the first pressure sensor. The controller gently increases, from zero, a current value outputted to the boom-lowering proportional solenoid valve.

Abstract: A work vehicle includes a boom, an arm, a bucket, an arm cylinder, a direction control valve, a calculation portion, and a speed determination portion. The calculation portion calculates an estimated speed of the arm cylinder based on correlation between an amount of movement of the spool of the direction control valve in accordance with an amount of operation of an arm control lever and a speed of the arm cylinder. The speed determination portion determines a target speed of the boom based on the estimated speed of the arm cylinder. When the amount of operation of the arm control lever is smaller than a prescribed amount, the calculation portion calculates a speed higher than a speed of the arm cylinder in accordance with correlation as the estimated speed of the arm cylinder.

Abstract: A work vehicle includes a speed limit calculation portion, a speed determination portion, an adjustment portion, and a boom speed determination portion. The speed limit calculation portion calculates a speed limit for limiting a speed of a cutting edge of a bucket. The speed determination portion determines whether or not a speed of raising the boom has been lowered when an amount of operation of an arm is smaller than a prescribed amount. The adjustment portion delays speed change to the speed limit. The boom speed determination portion determines a target speed of the boom based on the speed limit after delay by the adjustment portion when it is determined that the speed of raising the boom has been lowered, and determines a target speed of the boom based on the speed limit calculated when it is not determined that the speed of raising the boom has been lowered.

Abstract: There is provided a work vehicle in which sudden operation of a work implement can be suppressed. The work vehicle includes a design surface information acquiring unit for acquiring data of a design surface indicative of a target shape of a work object by the work implement; a cutting edge position computing unit for computing a position of a cutting edge of a bucket; and an operation restricting unit for executing operation restriction control by which a boom is forcibly raised in accordance with a relative position of the cutting edge to the design surface, and the position of the cutting edge is restricted to an upper part of the design surface. In a state where the cutting edge is located away from the design surface in a downward perpendicular direction by a prescribed distance or longer, the operation restricting unit does not execute the operation restriction control.

Abstract: There is provided a work vehicle in which a work implement can be freely operated. The work vehicle includes: a design surface information acquiring unit for acquiring data of a design surface indicative of a target shape of a work object by the work implement; a cutting edge position computing unit for computing a position of a cutting edge of a bucket; and an operation restricting unit for executing operation restriction control by which, when the cutting edge of the bucket comes closer to the design surface, operation of the work implement is stopped before the cutting edge of the bucket reaches the design surface. In a case where the cutting edge is located away from the design surface in a downward perpendicular direction by a prescribed distance or longer, the operation restricting unit does not execute the operation restriction control.

Abstract: There is provided a hydraulic excavator in which invasion of a design surface by a work implement can be suppressed. A boom-lowering proportional solenoid valve is provided in a boom-lowering pilot conduit connected to a boom-lowering pilot port. A first pressure sensor detects a pressure generated in the boom-lowering pilot conduit between a control lever and the boom-lowering proportional solenoid valve. A controller controls an opening degree of the boom-lowering proportional solenoid valve based on the pressure detected by the first pressure sensor. The controller gently increases, from zero, a current value outputted to the boom-lowering proportional solenoid valve.

Abstract: There is provided a hydraulic excavator in which occurrence of minute vibrations in a control lever can be suppressed. A boom-raising proportional solenoid valve is provided in a boom-raising pilot conduit. A boom-lowering proportional solenoid valve is provided in a boom-lowering pilot conduit. A controller controls an opening degree of the boom-lowering proportional solenoid valve based on a pressure generated in the boom-lowering pilot conduit between the control lever and the boom-lowering proportional solenoid valve, and controls an opening degree of the boom-raising proportional solenoid valve. An amount of increase in current per unit time when the controller outputs, to the boom-lowering proportional solenoid valve, an instruction signal for instructing an increase in opening degree is smaller than an amount of increase in current per unit time when the controller outputs, to the boom-raising proportional solenoid valve, an instruction signal for instructing an increase in opening degree.

Abstract: There is provided a hydraulic excavator in which occurrence of minute vibrations in a control lever can be suppressed. The hydraulic excavator includes: a first pilot pressure control valve outputting a pilot pressure in accordance with operation of the control lever; an upstream pilot conduit having one end connected to the first pilot pressure control valve; a proportional solenoid valve connected to the other end of the upstream pilot conduit; a downstream pilot conduit having one end connected to the proportional solenoid valve; and a pilot switching valve for a boom having a second pilot port connected to the other end of the downstream pilot conduit, and controlling operation of the boom. A volume of the upstream pilot conduit is larger than a volume of the downstream pilot conduit.

Abstract: There is provided a hydraulic excavator in which occurrence of minute vibrations in a control lever can be suppressed. The hydraulic excavator includes: a first pilot pressure control valve outputting a pilot pressure in accordance with operation of the control lever; an upstream pilot conduit having one end connected to the first pilot pressure control valve; a proportional solenoid valve connected to the other end of the upstream pilot conduit; a downstream pilot conduit having one end connected to the proportional solenoid valve; and a pilot switching valve for a boom having a second pilot port connected to the other end of the downstream pilot conduit, and controlling operation of the boom. A volume of the upstream pilot conduit is larger than a volume of the downstream pilot conduit.

Abstract: A work vehicle is provided with an engine, a traveling device driven by driving force from the engine to cause the work vehicle to travel, a first hydraulic pump driven by the driving force from the engine to discharge hydraulic oil, and a cooling device having a cooling fan driven by the hydraulic oil supplied by the first hydraulic pump to cool the engine, and a control unit. The control unit performs a normal cooling control in which an upper limit fan speed is determined based on an engine speed, and a cooling suppression control in which the upper limit fan speed determined based on the engine speed is suppressed to be less than the upper limit fan speed during the normal cooling control when a predetermined operation required to increase the engine speed is performed.

Abstract: A work vehicle is provided with an engine, a traveling device driven by driving force from the engine to cause the work vehicle to travel, a first hydraulic pump driven by the driving force from the engine to discharge hydraulic oil, and a cooling device having a cooling fan driven by the hydraulic oil supplied by the first hydraulic pump to cool the engine, and a control unit. The control unit performs a normal cooling control in which an upper limit fan speed is determined based on an engine speed, and a cooling suppression control in which the upper limit fan speed determined based on the engine speed is suppressed to be less than the upper limit fan speed during the normal cooling control when a predetermined operation required to increase the engine speed is performed.

Abstract: A hydraulic control apparatus which is used in order to prevent the blade from falling over on the pitch back side during a dual tilting operation, and to operate the left and right tilting cylinders in a uniform manner even in case where there is a large difference in the load pressure between the left and right tilting cylinders. In cases where it is desired to perform a dual tilting operation, the operator moves the operating lever either leftward or rightward while pressing the dual tilting switch of the operating lever. As a result of the switch being pressed, an electrical control signal that places the flow-combining/flow-dividing switching valve or flow-combining/flow-dividing valve in the flow-dividing position is generated by the controller, and the electrical control signal is output to the flow-combining/flow-dividing switching valve so that the flow-combining/flow-dividing switching valve or flow-combining/flow-dividing valve is switched to the flow-dividing position.

Abstract: A hydraulic control apparatus which is used in order to prevent the blade from falling over on the pitch back side during a dual tilting operation, and to operate the left and right tilting cylinders in a uniform manner even in case where there is a large difference in the load pressure between the left and right tilting cylinders. In cases where it is desired to perform a dual tilting operation, the operator moves the operating lever either leftward or rightward while pressing the dual tilting switch of the operating lever. As a result of the switch being pressed, an electrical control signal that places the flow-combining/flow-dividing switching valve or flow-combining/flow-dividing valve in the flow-dividing position is generated by the controller, and the electrical control signal is output to the flow-combining/flow-dividing switching valve so that the flow-combining/flow-dividing switching valve or flow-combining/flow-dividing valve is switched to the flow-dividing position.

Abstract: An optimal pump flow for both dual tilt operations and single tilt operations is obtained at low cost without increasing the complexity of the device constitution. Where there is a wish to implement a dual tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value decreases and a comparatively small flow is supplied from the hydraulic pump to the left and right tilt cylinders. Accordingly, the extension/retraction speed of the left and right tilt cylinders decreases. Where there is a wish to implement a single tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value increases and a comparatively large flow is supplied from the hydraulic pump to the left cylinder. Accordingly, the extension/retraction speed of the left tilt cylinder increases.

Abstract: An optimal pump flow for both dual tilt operations and single tilt operations is obtained at low cost without increasing the complexity of the device constitution. Where there is a wish to implement a dual tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value decreases and a comparatively small flow is supplied from the hydraulic pump to the left and right tilt cylinders. Accordingly, the extension/retraction speed of the left and right tilt cylinders decreases. Where there is a wish to implement a single tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value increases and a comparatively large flow is supplied from the hydraulic pump to the left cylinder. Accordingly, the extension/retraction speed of the left tilt cylinder increases.