Cargo bed raising and lowering apparatus of dump truck

A cargo bed raising and lowering apparatus of a dump truck in which a cargo bed is connected to a vehicle body frame so that the cargo bed can be raised and lowered pivotally on a hinge, a flow path of hydraulic oil to be discharged from a hydraulic source is switched by a control valve according to an operation of a hoisting operation device to supply the hydraulic oil to each of a pair of hoist cylinders arranged at left and right end portions of the cargo bed in a vehicle width direction, and the cargo bed is raised or lowered according to extension or contraction of the hoist cylinders, the cargo bed raising and lowering apparatus comprising:

• an oil supply amount adjusting unit capable of individually adjusting oil supply amounts of the hydraulic oil to the pair of hoist cylinders;
• a cargo bed tilt detecting unit for detecting a tilt in the vehicle width direction of the cargo bed;
• an oil supply amount calculating unit for calculating the amount of the hydraulic oil to be supplied to each of the hoist cylinders based on the tilt of the cargo bed detected by the cargo bed tilt detecting unit;
• and
• an oil supply amount control unit for controlling the oil supply amount adjusting unit based on the amount of the hydraulic oil to be supplied to each of the hoist cylinders calculated by the oil supply amount calculating unit, wherein
• the cargo bed tilt detecting unit includes a pair of hoist cylinder pressure detecting sensors for detecting bottom pressures of the pair of hoist cylinders respectively, comprising a roll angle calculating unit for calculating a roll angle indicating the tilt of the cargo bed with respect to the vehicle body frame based on a difference between the pressures detected by the pair of hoist cylinder pressure detecting sensors.

A cargo bed raising and lowering apparatus of a dump truck in which a cargo bed is connected to a vehicle body frame so that the cargo bed can be raised and lowered pivotally on a hinge, a flow path of hydraulic oil to be discharged from a hydraulic source is switched by a control valve according to an operation of a hoisting operation device to supply the hydraulic oil to each of a pair of hoist cylinders arranged at left and right end portions of the cargo bed in a vehicle width direction, and the cargo bed is raised or lowered according to extension or contraction of the hoist cylinders, the cargo bed raising and lowering apparatus comprising:

• an oil supply amount adjusting unit capable of individually adjusting oil supply amounts of the hydraulic oil to the pair of hoist cylinders;
• a cargo bed tilt detecting unit for detecting a tilt in the vehicle width direction of the cargo bed;
• an oil supply amount calculating unit for calculating the amount of the hydraulic oil to be supplied to each of the hoist cylinders based on the tilt of the cargo bed detected by the cargo bed tilt detecting unit;
• and
• an oil supply amount control unit for controlling the oil supply amount adjusting unit based on the amount of the hydraulic oil to be supplied to each of the hoist cylinders calculated by the oil supply amount calculating unit, wherein
• the cargo bed tilt detecting unit includes four suspension cylinder pressure detecting sensors for detecting bottom pressures of suspension cylinders constituting four suspensions that independently suspend four wheels on front, rear, left, and right sides of the dump truck respectively, comprising a roll angle calculating unit for calculating a roll angle indicating the tilt of the cargo bed with respect to the vehicle body frame based on a difference among the pressures detected by the four suspension cylinder pressure detecting sensors.