Hardware knowledge base: hydraulic cylinder

Summary

The pressure cylinder is a hydraulic actuator that converts hydraulic energy into mechanical energy and performs linear reciprocating motion.

Hydraulic cylinder

Definition and composition

Hydraulic cylinders are hydraulic actuators that convert hydraulic energy into mechanical energy and perform linear reciprocating motion (or oscillating motion). Its structure is simple and reliable. When it is used to realize reciprocating motion, the deceleration device can be eliminated, and there is no transmission gap and the movement is stable. Therefore, it is widely used in various mechanical hydraulic systems. The output force of the hydraulic cylinder is proportional to the effective area of ​​the piston and the pressure difference between the two sides; the hydraulic cylinder basically consists of a cylinder barrel and a cylinder head, a piston and a piston rod, a sealing device, a buffer device and an exhaust device.

The cushioning device and the exhaust device depend on the specific application, and other devices are essential.

Hydraulic cylinder type:

According to the structure of commonly used hydraulic cylinders, it can be divided into four types:

Piston type

A single rod hydraulic cylinder only has a piston rod at one end. The figure shows a single-piston hydraulic cylinder. Both ends of the import and export of oil port A and B can pass the pressure oil or return oil to achieve two-way movement, it is called double-acting cylinder.

2. Piston type

(1) The plunger-type hydraulic cylinder is a type of single-acting hydraulic cylinder. It can only realize the movement in one direction by the hydraulic pressure. The return stroke of the plunger must rely on the external force or the self weight of the plunger.

(2) The plunger is only supported by the liner and not in contact with the cylinder liner, so that the liner is easy to process, so it is suitable for long-stroke hydraulic cylinders;

(3) The plunger is always under pressure during operation, so it must have sufficient rigidity;

(4) The weight of the plunger tends to be large, and it is prone to sagging due to its own weight when placed horizontally, resulting in unilateral abrasion of the seal and the guide, so its vertical use is more advantageous.

3. Telescopic

Telescopic hydraulic cylinders have two or more stages of pistons. The pistons in telescopic hydraulic cylinders protrude from the largest to the smallest, while the order of no-load retraction is generally from small to large. Telescopic cylinders allow longer strokes, shorter lengths when retracted, and a more compact structure. Such hydraulic cylinders are commonly used in construction machinery and agricultural machinery.

Swing hydraulic cylinder is the actuator that outputs torque and realizes reciprocating motion. It is also called swing hydraulic motor. There are two types of single Blade and double blade. The stator block is fixed on the cylinder block, and the blades and the rotor are connected together. According to the direction of oil intake, the blades will drive the rotor to swing back and forth.