Truck cranes are a series of products produced in batches with many types. The QY-12 fully hydraulic truck crane is taken as an example to introduce the structure and working principle of its main components. ? (As shown in the picture) is the external graphic of QY12 truck crane. Its main technical parameters are as follows: Maximum lifting capacity: 12000kg when the working radius is 3m Maximum lifting capacity moment: 358kN.m Main boom: 3 sections Overall machine weight: 13200kg Driving performance: Maximum speed 70km/ h, the maximum climbing angle is 12.9o? The QY12 truck crane is a full-rotation hydraulic crane with a three-section telescopic boom. The power take-off device is located on the right side of the crane chassis transmission. When the crane switches from driving to crane operation, the power take-off joystick is manipulated in the chassis cab to engage the power take-off device. The car engine power is transmitted to the gear pump through the power take-off device, and the gear The pump works. The pressure oil generated by the gear pump drives the crane's outrigger control and upper car rotation, luffing, telescopic mechanism and winch mechanism through the hydraulic system. ?

The outriggers are of "H"-shaped structure. The front and rear fixed legs are welded under the chassis respectively. The four movable outriggers are respectively installed in the front and rear fixed leg boxes. The outrigger structure is hydraulically driven. ? The movable outriggers are controlled by the outrigger control valve. They can operate simultaneously or individually. Generally, the horizontal outriggers are extended first and then the vertical legs are extended. When retracting, the vertical outriggers should be retracted first. , and then the horizontal leg is retracted. ? The main arm of the boom is a three-section, four-sided box-shaped boom, and the telescopic mechanism is a single-stage oil cylinder plus a steel wire rope (as shown in the figure). ? In order to improve the stability of the telescopic cylinder, the telescopic cylinder is installed upside down in the telescopic arm. The piston rod head is hinged and fixed to the tail of the basic arm, and the simple end of the cylinder is hinged and fixed to the root of the two-section arm. When the telescopic cylinder extends, the piston rod is fixed and the basic arm does not move, and the cylinder movement pushes out the two-section arm. When the telescopic oil cylinder retracts, the cylinder movement pulls the two-section arm back. ? The lifting mechanism consists of a hydraulic motor, a double-stage cylindrical gear, a reducer, a brake, a drum, a wire rope, and a lifting hook system. The brake is a normally closed friction plate dry brake. Its control is realized by the brake cylinder, and the heavy object can be stopped at any position during the lifting process without sliding down. A balance valve is installed in the hydraulic circuit of the lifting mechanism to control the speed at which the weight drops. ? The slewing mechanism is composed of a hydraulic motor, a worm gear reducer, a slewing bearing, etc. When the rotary mechanism is working, the gear pump supplies pressure oil and is driven by a quantitative motor. It can realize forward and reverse rotation through the control of the rotary distribution valve. ? The luffing mechanism consists of a boom, a turntable and a forward-inclined double-acting oil cylinder. Its luffing action is achieved through the expansion and contraction of the double-acting cylinder. The function of the luffing mechanism is to change the elevation angle of the boom, thereby making the crane The distance (i.e. amplitude) between the hook and the upper car's rotation center is changed.