Hydraulic cylinder It is a hydraulic actuator that converts hydraulic energy into mechanical energy and performs linear reciprocating motion (or swing motion). It is simple in structure and reliable in operation. When it is used to realize reciprocating movement, the reducer can be avoided, and there is no transmission clearance, so the movement is stable Hydraulic system It is widely used in. Output force of the hydraulic cylinder is proportional to effective area of the piston and pressure difference on both sides; The hydraulic cylinder is basically composed of cylinder barrel and head, piston and piston rod, sealing device, buffer device and exhaust device. The buffer device and exhaust device depend on the specific application, and other devices are indispensable.

1、 Classification of hydraulic cylinders

Hydraulic cylinders have various structural forms, and their classification methods are also various: according to the motion mode, they can be divided into linear reciprocating motion type and rotary swing type; According to the action of hydraulic pressure, it can be divided into single action type and double action type; According to the structure, it can be divided into piston type, plunger type, multi-stage telescopic sleeve type, gear rack type, etc; According to the installation form, it can be divided into pull rod, earring, foot, hinge shaft, etc; According to the pressure grade, it can be divided into 16Mpa, 25Mpa, 31.5Mpa, etc.

1. Piston type

The single piston rod hydraulic cylinder only has a piston rod at one end. As shown in the figure, it is a single piston hydraulic cylinder. Both the inlet and outlet oil ports A and B at both ends can be supplied with pressure oil or return oil to realize two-way movement, so it is called double acting cylinder.

The piston can only move in one direction, and its reverse movement needs to be completed by external force. But its stroke is generally more than that of piston hydraulic oil The cylinder is large.

Piston hydraulic oil Cylinders can be divided into single rod type and double rod type structures. Their fixation methods are cylinder block fixation and piston rod fixation. According to the action of hydraulic pressure, there are single acting type and double acting type. In single acting hydraulic oil In cylinder, pressure oil is only used for hydraulic pressure oil One cavity of the cylinder, the cylinder can move in one direction by hydraulic pressure, and the opposite direction can be achieved by external force (such as spring force, dead weight or external load); Double acting hydraulic pressure oil The movement of the cylinder piston in both directions is completed by the action of hydraulic pressure by alternately feeding oil into the two chambers.

Single rod double acting piston hydraulic oil The cylinder is only equipped with a piston rod on one side of the piston, so the effective area of the two chambers is different. When the oil supply is the same, the movement speed of the piston is different with the oil inlet from different chambers; When the load force to be overcome is the same, the oil supply pressure required by different cavities is different, or after the system pressure is set, the sanitation garbage truck hydraulic pressure oil The cylinder can overcome different load forces when moving in two directions.

2. Plunger type

(1) Plunger hydraulic oil The cylinder is a single acting hydraulic pressure oil The cylinder can only move in one direction by hydraulic pressure, and the return of the plunger depends on other external forces or the weight of the plunger;

(2) The plunger is only supported by the cylinder liner and does not contact the cylinder liner, so the cylinder liner is very easy to process, so it is suitable for long stroke hydraulic oil Cylinder;

(3) When working, the plunger is always under pressure, so it must have sufficient rigidity;

(4) The weight of plunger is often large, and it is easy to sag due to its own weight when it is placed horizontally, resulting in unilateral wear of seals and guides, so its vertical use is more favorable.

Telescopic hydraulic oil The cylinder has two or multiple pistons, telescopic hydraulic oil The sequence of piston extension in cylinder is from large to small, while the sequence of no-load retraction is generally from small to large. The telescopic cylinder can achieve a longer stroke, while the length is shorter when retracted, and the structure is more compact. This hydraulic pressure oil Cylinder is often used in construction machinery and agricultural machinery. There are multiple pistons moving at one time. When each piston moves step by step, its output speed and output force change.

3. Swing hydraulic oil Cylinder

Swing hydraulic oil Cylinder is an executive element that outputs torque and realizes reciprocating motion. It has several forms, such as single blade, double blade, spiral swing, etc. Vane type: the stator block is fixed on the cylinder block, while the blade and rotor are connected together. According to the oil inlet direction, the blade will drive the rotor to reciprocate. The spiral swing type is divided into single spiral swing type and double spiral type. Now double spiral type is commonly used, and the hydraulic pressure is lowered by two screw pairs oil The linear motion of the piston in the cylinder is transformed into the compound motion of linear motion and rotation, thus realizing the swing motion.