Abstract: This expansion device is an expansion device that expands and contracts an boom, the expansion device including: a first hydraulic source that discharges a first working fluid; an expandable cylinder that has a fixed part and a movable part and is operated by the first working fluid; a second hydraulic source that is provided to the movable part, discharges the second working fluid, and is a separate hydraulic source from the first hydraulic source; a first connecting mechanism that is operated by the second working fluid and switches between a connected state and a disconnected state of the first boom element and the movable part; and a second connecting mechanism that is operated by the second working fluid and switches between a connected state and a disconnected state of the first boom element and the second boom element.

Abstract: This work machine includes: a first hydraulic cylinder and a second hydraulic cylinder that telescope a telescopic boom on the basis of hydraulic oil supply and discharge, a switching valve that is disposed on a pressure relief circuit for connecting the first hydraulic cylinder and the second hydraulic cylinder to a tank, and a control unit that causes the switching valve to connect the first hydraulic cylinder to the tank and releases the pressure in the first hydraulic cylinder when contracting or extending the second hydraulic cylinder in a condition in which the first hydraulic cylinder is contracted.

Abstract: A work vehicle includes: an operation tool that is operated by an operator; and a controller that determines a target flow rate for hydraulic oil fed to a hydraulic device on a basis of the amount of operation of the operation tool. The controller calculates a bleed-off target flow rate on a basis of the flow rate of hydraulic oil fed from a hydraulic oil pump and the target flow rate for hydraulic oil fed to the hydraulic device, calculates a bleed-off throttle differential pressure on a basis of a pressure of hydraulic oil fed from the hydraulic oil pump and a pressure of hydraulic oil in a hydraulic oil tank, calculates a bleed-off target opening area on a basis of the bleed-off target flow rate and the bleed-off throttle differential pressure, and controls a hydraulic oil control valve such that the bleed-off target opening area is achieved.

Abstract: This crane is provided with: a telescopic boom that can be extended; an extension device for extending the telescopic boom; a hydraulic pressure source provided in the extension device; a cylinder connection mechanism connected to the hydraulic pressure source and switching between the states of connection and non-connection with the telescopic boom on the basis of the supply and discharge of hydraulic oil; a first oil path for connecting the hydraulic pressure source and the cylinder connection mechanism; a first valve that is provided on the first oil path and switches the supply and discharge state of the hydraulic oil with respect to the cylinder connection mechanism; and a second oil path that bypasses the first valve and connects the hydraulic pressure source and the cylinder connection mechanism.

Abstract: This expansion device is an expansion device that expands and contracts an boom, the expansion device including: a first hydraulic source that discharges a first working fluid; an expandable cylinder that has a fixed part and a movable part and is operated by the first working fluid; a second hydraulic source that is provided to the movable part, discharges the second working fluid, and is a separate hydraulic source from the first hydraulic source; a first connecting mechanism that is operated by the second working fluid and switches between a connected state and a disconnected state of the first boom element and the movable part; and a second connecting mechanism that is operated by the second working fluid and switches between a connected state and a disconnected state of the first boom element and the second boom element.

Abstract: A work vehicle includes: an operation tool that is operated by an operator; and a controller that determines a target flow rate for hydraulic oil fed to a hydraulic device on a basis of the amount of operation of the operation tool. The controller calculates a bleed-off target flow rate on a basis of the flow rate of hydraulic oil fed from a hydraulic oil pump and the target flow rate for hydraulic oil fed to the hydraulic device, calculates a bleed-off throttle differential pressure on a basis of a pressure of hydraulic oil fed from the hydraulic oil pump and a pressure of hydraulic oil in a hydraulic oil tank, calculates a bleed-off target opening area on a basis of the bleed-off target flow rate and the bleed-off throttle differential pressure, and controls a hydraulic oil control valve such that the bleed-off target opening area is achieved.

Abstract: This crane is provided with: a telescopic boom that can be extended; an extension device for extending the telescopic boom; a hydraulic pressure source provided in the extension device; a cylinder connection mechanism connected to the hydraulic pressure source and switching between the states of connection and non-connection with the telescopic boom on the basis of the supply and discharge of hydraulic oil; a first oil path for connecting the hydraulic pressure source and the cylinder connection mechanism; a first valve that is provided on the first oil path and switches the supply and discharge state of the hydraulic oil with respect to the cylinder connection mechanism; and a second oil path that bypasses the first valve and connects the hydraulic pressure source and the cylinder connection mechanism.

Abstract: An informing device is an informing device mounted on a work vehicle that includes a lower base body, and a swivel body swivelably provided at the lower base body. The informing device includes a first detection unit that detects the actual amount of rotation of a drive device which swivels the swivel body or a driven part driven by the drive device, and a notification unit that issues a notification regarding information corresponding to the amount of rotation detected by the first detection unit.

Abstract: This hydraulic system is provided with: a hydraulic pump; a pilot-type control valve; an electromagnetic proportional valve; a controller; and a pilot pressure switching unit which is capable of switching the electromagnetic proportional valve supply pressure to a first pressure during a normal operation, or to a second pressure lower than the first pressure. The control valve is provided with a bleed-off passage, and is capable of controlling the operating oil pressure supplied to the actuator, according to the opening area thereof. During an emergency operation, the electromagnetic proportional valve supply pressure is switched from the first pressure to the second pressure, the electromagnetic proportional valve is brought into a fully opened state, and the operating oil discharge amount from the hydraulic pump increases and decreases, and the operating oil pressure increases and decreases, and thus the operating speed of the actuator is controlled.

Abstract: The failure detection device is a failure detection device of a pilot circuit, the pilot circuit including: a pilot pressure source; a pilot pressure supply unit that supplies pilot pressure to a control valve; a pilot oil path that connects the pilot pressure source and a pilot pressure supply unit; and a pressure control unit that controls a pressure of the pilot oil path, the failure detection device including: a pressure sensor that measures the pressure on a downstream side in a pilot pressure supply direction of the pressure control unit; and a controller that controls the pressure control unit to sequentially switch the pressure of the pilot oil path and performs a failure diagnosis based on a measurement result of the pressure sensor at this time, as an operation lever which receives an operation for operating the actuator returns to a neutral state.

Abstract: Provided is a crane capable of allowing an operator to recognize an error in work information or in a number of windings set in a safety device. A main tension of a main wire rope is calculated from a main output torque of a main winch, a sub output torque of a sub winch, a main drum winding radius of the main winch, and a sub drum winding radius of the sub winch. An estimated hanging load, which is calculated from the main tension, a sub tension of a sub wire rope and the number of windings of the wire rope set in a safety device, is compared with an actual hanging load calculated from fluctuating thrust force and boom information. Thus, the suitability of a work kind or a winding number set in the safety device is determined.

Abstract: This hydraulic system is provided with a hydraulic pump, a control valve, and a pilot pressure supply unit. The pilot pressure supply unit has: an electromagnetic proportional valve that has a detent-type emergency manual operation function with which a pilot oil passage can be opened manually and generates pilot pressure for a control valve; a controller that controls the degree of opening of the electromagnetic proportional valve in accordance with the operation of an operation lever; and a pilot pressure switching unit that switches the oil pressure state of the pilot pressure supply unit between an on-loading state and an unloading state. The pilot pressure switching unit performs control to implement the unloading state when the electromagnetic proportional valve is being opened manually and performs control to implement the on-loading state after the electromagnetic proportional valve has been opened manually.

Abstract: A crane 1, the hook (main hook 24) of which is stored on the lower end of a boom 7, and the winch (main winch 9) of which can be moved by a hydraulic motor 37, said crane being provided with a pressure sensor 55 capable of detecting the pressure of hydraulic fluid being delivered to the hydraulic motor 37, and a controller 61 capable of recognizing changes in the pressure of the hydraulic fluid on the basis of a signal from the pressure sensor 55, and also being provided with an anomaly warning means Mi capable of providing warning of anomalies pertaining to the storage of at least the hook (24), the controller 61 activating the anomaly warning means Mi when it is determined that the pressure of the hydraulic fluid when the hook has been stored is below a minimum value.

Abstract: The unload circuit includes a pump oil passage that connects between a hydraulic pump and a direction control valve, a tank oil passage that connects between the direction control valve and a hydraulic tank, a pressure compensating flow control valve interposed between the pump oil passage and the tank oil passage, a pilot operated relief valve interposed between the pump oil passage and the tank oil passage, and an unloading solenoid valve interposed in a vent oil passage of the pilot operated relief valve. The failure diagnosis device includes a pressure sensor that measures a pressure of the pump oil passage, and a controller that receives a pressure signal from the pressure sensor. The controller performs failure diagnosis of the unload circuit based on a differential pressure between a first pump oil passage pressure during unloading and a second pump oil passage pressure during on-loading.

Abstract: This hydraulic system is provided with: a hydraulic pump; a pilot-type control valve; an electromagnetic proportional valve; a controller; and a pilot pressure switching unit which is capable of switching the electromagnetic proportional valve supply pressure to a first pressure during a normal operation, or to a second pressure lower than the first pressure. The control valve is provided with a bleed-off passage, and is capable of controlling the operating oil pressure supplied to the actuator, according to the opening area thereof. During an emergency operation, the electromagnetic proportional valve supply pressure is switched from the first pressure to the second pressure, the electromagnetic proportional valve is brought into a fully opened state, and the operating oil discharge amount from the hydraulic pump increases and decreases, and the operating oil pressure increases and decreases, and thus the operating speed of the actuator is controlled.

Abstract: A crane is disclosed, the crane includes detachable hydraulic cylinder including a head side oil chamber and a rod side oil chamber both to be connected to a control valve through a joint, in which a head side hydraulic detecting section and a rod side hydraulic detecting section are each provided to the hydraulic cylinder, and a connection state between the hydraulic cylinder and the control valve is determined based on a head side hydraulic pressure and a rod side hydraulic pressure in a period until a predetermined time elapses after supply of electric power to the head side hydraulic detecting section and the rod side hydraulic detecting section is started and an operation tool for hydraulic cylinder switches the control valve to a state of supplying hydraulic fluid to the hydraulic cylinder.

Abstract: The failure detection device is a failure detection device of a pilot circuit, the pilot circuit including: a pilot pressure source; a pilot pressure supply unit that supplies pilot pressure to a control valve; a pilot oil path that connects the pilot pressure source and a pilot pressure supply unit; and a pressure control unit that controls a pressure of the pilot oil path, the failure detection device including: a pressure sensor that measures the pressure on a downstream side in a pilot pressure supply direction of the pressure control unit; and a controller that controls the pressure control unit to sequentially switch the pressure of the pilot oil path and performs a failure diagnosis based on a measurement result of the pressure sensor at this time, as an operation lever which receives an operation for operating the actuator returns to a neutral state.

Abstract: An actuator control device performs a reception process in which designations of a minimum operation amount and maximum operation amount of an operation unit for driving an actuator, and a maximum driving speed which is the actuator driving speed corresponding to the maximum operation amount are received. It also performs a determination process in which a function representing a characteristic line that links a first point, which corresponds to the minimum operation amount and the driving speed of 0, and a second point, which corresponds to the maximum operation amount and the maximum driving speed, is stored in a storage unit as a drive control characteristic and a drive control process in which, in response to operation of the operation unit, the actuator is driven at a driving speed corresponding to the operation amount specified by the drive control characteristic stored in the storage unit.

Abstract: An expansion/contraction mechanism includes a telescopic cylinder, boom fixing means, cylinder-boom connecting means, and a hydraulic-pressure supply unit, and telescopes a plurality of booms except a base boom by telescoping the telescopic cylinder. The hydraulic-pressure supply unit includes a pneumatic-pressure source, a selector valve which selects a destination of air provided from the pneumatic-pressure source, a first pneumatic path through which first air sent from the selector valve circulates, a second pneumatic path through which second air sent from the selector valve circulates, a first pneumatic-to-hydraulic conversion unit which converts a pneumatic pressure provided by the first air to a hydraulic pressure and supplies the hydraulic pressure to a first hydraulic cylinder, and a second pneumatic-to-hydraulic conversion unit which converts a pneumatic pressure provided by the second air to a hydraulic pressure and supplies the hydraulic pressure to a second hydraulic cylinder.

Abstract: Provided is a crane capable of allowing an operator to recognize an error in work information or in a number of windings set in a safety device. A main tension of a main wire rope is calculated from a main output torque of a main winch, a sub output torque of a sub winch, a main drum winding radius of the main winch, and a sub drum winding radius of the sub winch. An estimated hanging load, which is calculated from the main tension, a sub tension of a sub wire rope and the number of windings of the wire rope set in a safety device, is compared with an actual hanging load calculated from fluctuating thrust force and boom information. Thus, the suitability of a work kind or a winding number set in the safety device is determined.