Hydraulic Cylinder Introduction

Hydraulic cylinder is a hydraulic actuator that transforms hydraulic energy into mechanical energy and does linear reciprocating motion (or oscillating motion), which is also one of the hydraulic parts. It is simple in structure and reliable in operation. When using it to achieve reciprocating motion, it can eliminate the deceleration device, and there is no transmission gap, smooth movement, so it is widely used in the hydraulic system of various machines. The output force of hydraulic cylinder is proportional to the effective area of the piston and the pressure difference between its two sides; the hydraulic cylinder basically consists of cylinder barrel and cylinder head, piston and piston rod, sealing device, buffer device and exhaust device. The buffer and exhaust device depend on the specific application, while other devices are essential.

Introduction

Hydraulic cylinder is the executive component of hydraulic transmission system, it is the energy conversion device that converts hydraulic energy into mechanical energy. The hydraulic motor is to achieve continuous rotary motion, while the hydraulic cylinder is to achieve reciprocating motion. The structure of hydraulic cylinders includes piston cylinder, plunger cylinder and oscillating cylinder. The piston cylinder and plunger cylinder achieve reciprocating linear motion and output speed and thrust, while the oscillating cylinder achieves reciprocating oscillation and outputs angular speed (speed) and torque. In addition to being used individually, hydraulic cylinders can also be used in combination of two or more or with other mechanisms. To accomplish special functions. Hydraulic cylinders are simple and reliable and are widely used in the hydraulic system of machine tools.

Classification

There are various structural forms of hydraulic cylinders and various methods of classification: according to the motion mode, it can be divided into linear reciprocating motion and rotary oscillating type; according to the action of liquid pressure, it can be divided into single-acting type and double-acting type; according to the structure form, it can be divided into piston type, plunger type, multi-stage telescopic sleeve type, rack and pinion type, etc.; according to the installation form, it can be divided into tie rod, earring, foot, hinge shaft, etc.; according to the pressure level, it can be divided into 16 Mpa, 25Mpa, 31.5Mpa, etc.

Piston Type

A single piston rod hydraulic cylinder has a piston rod at only one end. As shown in Figure 1 is a single piston hydraulic cylinder. Its two ends of the import and export ports A and B can pass pressure oil or return oil, in order to achieve two-way movement, so called double-action cylinder.

The piston can only move in one direction, and its reverse direction movement needs to be completed by external force. But its stroke is generally larger than the piston type hydraulic cylinder.

Piston hydraulic cylinder can be divided into single-rod and double-rod two kinds of structure, its fixed way by the cylinder body fixed and piston rod fixed two kinds, according to the role of hydraulic pressure there are single-acting and double-acting type. In single-acting hydraulic cylinder, the pressure oil is only supplied to one cavity of the cylinder, and the liquid pressure makes the cylinder realize single direction movement, and the opposite direction movement is realized by external force (such as spring force, self-weight or external load, etc.); while the double-acting hydraulic cylinder piston movement in two directions is done by two cavities alternately feeding oil and relying on the action of liquid pressure.

Piston Type

piston hydraulic cylinder is a single-acting hydraulic cylinder, by hydraulic pressure can only achieve a direction of movement, the plunger return to rely on other external forces or the self-weight of the plunger;.
the plunger is only supported by the cylinder sleeve and not in contact with the sleeve, so the sleeve is very easy to process, so it is suitable for long stroke hydraulic cylinder.
the plunger is always under pressure when working, so it must have sufficient stiffness.
plunger weight is often large, horizontal placement is easy to sag due to self-weight, resulting in seals and guide single-sided wear, so its vertical use is more favorable.

Piston Type

Telescopic hydraulic cylinder has two or more stages of piston, telescopic hydraulic cylinder piston out of the sequence from large to small, and no load retraction sequence is generally from small to large. Telescopic cylinder can achieve a longer stroke, and retracted length is shorter, more compact structure. This type of hydraulic cylinder is commonly used in construction and agricultural machinery. There are multiple pistons moving at once, each piston moving one by one, the output speed and output force are variable.

Piston Type

Oscillating hydraulic cylinder is an actuating element that outputs torque and achieves reciprocating motion. There are several forms such as single vane, double vane and spiral oscillation. Vane type: the stator block is fixed on the cylinder, while the vane and rotor are connected together. According to the direction of oil feed, the vane will drive the rotor to make reciprocating oscillation. Spiral oscillation type and divided into single spiral oscillation and double spiral two, now double spiral is more commonly used, rely on two spiral vice descending hydraulic cylinder piston linear motion into linear motion and rotation motion of the composite motion, so as to achieve oscillation motion.