Crane slewing control device and crane equipped with same

A crane slewing control device used for a crane including:

• a lower body;
• an upper slewing body supported by the lower body to be able to slew about a slewing center axis extending in an up-and-down direction with respect to the lower body;
• a controller including circuitry that receives an operation to slew the upper slewing body with respect to the lower body and outputs a slewing command signal according to magnitude of the operation, the controller allowing an operation by a worker for slewing the upper slewing body to be applied to the controller;
• a slewing drive unit capable of slewing the upper slewing body with respect to the lower body;
• an attachment including a proximal end pivotably supported by the upper slewing body in a hoisting direction and a distal end opposite the proximal end, the attachment being attachable to and detachable from the upper slewing body;
• and
• a hoist cargo rope hanging down from the distal end of the attachment and connected to a hoist cargo,
• the crane slewing control device comprising:
• an attachment information acquisition unit that acquires attachment information, the attachment information being information peculiar to the attachment for setting a maximum slewing angular velocity that is a maximum value of a slewing angular velocity based on a transverse load that is a load along a slewing direction of the upper slewing body acting on the attachment due to the slewing angular velocity of the upper slewing body;
• an angular velocity setting unit that sets the maximum slewing angular velocity that is allowed in a slewing operation of the upper slewing body based on at least the attachment information acquired by the attachment information acquisition unit;
• and
• a slewing control unit that receives the slewing command signal output from the controller and controls the slewing drive unit to cause the upper slewing body to slew with respect to the lower body in response to the slewing command signal, the slewing control unit controlling the slewing drive unit such that the slewing angular velocity of the upper slewing body does not exceed the maximum slewing angular velocity set by the angular velocity setting unit, wherein
• the slewing drive unit of the crane includes:
• an engine including an output shaft;
• a variable displacement hydraulic pump that is coupled to the output shaft and discharges a hydraulic oil by power input from the output shaft, the hydraulic pump being able to receive input of a tilt command signal and change a maximum discharge amount of the hydraulic oil according to magnitude of the tilt command signal;
• a hydraulic slewing motor that includes a plurality of hydraulic chambers inside and generates driving force to slew the upper slewing body by receiving the hydraulic oil supplied from the hydraulic pump into one of the plurality of hydraulic chambers and discharging the hydraulic oil from another hydraulic chamber of the plurality of hydraulic chambers;
• and
• a flow rate adjustment mechanism that includes a control valve interposed between the hydraulic pump and the slewing motor, and adjusts a flow rate of the hydraulic oil supplied to the slewing motor out of the hydraulic oil discharged from the hydraulic pump in response to the slewing command signal output from the controller,
• the slewing control unit limits a discharge amount of the hydraulic oil discharged from the hydraulic pump such that the slewing angular velocity of the upper slewing body does not exceed the maximum slewing angular velocity by inputting the tilt command signal corresponding to the maximum slewing angular velocity set by the angular velocity setting unit into the hydraulic pump,
• the hydraulic pump discharges the hydraulic oil of a minimum discharge amount greater than zero, and
• when the discharge amount of the hydraulic pump corresponding to the maximum slewing angular velocity set by the angular velocity setting unit is greater than the minimum discharge amount, the slewing control unit limits the discharge amount of the hydraulic oil discharged from the hydraulic pump such that the slewing angular velocity of the upper slewing body does not exceed the maximum slewing angular velocity by inputting the tilt command signal corresponding to the maximum slewing angular velocity into the hydraulic pump,
• meanwhile, when the discharge amount of the hydraulic pump corresponding to the maximum slewing angular velocity set by the angular velocity setting unit is smaller than the minimum discharge amount, the slewing control unit limits the flow rate of the hydraulic oil supplied from the flow rate adjustment mechanism to the slewing motor such that the slewing angular velocity of the upper slewing body does not exceed the maximum slewing angular velocity regardless of magnitude of the slewing command signal by inputting a compulsory command signal corresponding to the maximum slewing angular velocity into the flow rate adjustment mechanism.