The working principle of the hydraulic cylinder is based on the basic principle of hydraulic transmission. It uses hydraulic oil as the working medium and pushes the piston to move through the pressure of the hydraulic system to achieve mechanical work. The hydraulic cylinder is usually an actuator in the hydraulic system, which is used to convert hydraulic energy into mechanical energy. The following is a detailed description of the working principle of the hydraulic cylinder:

1. Basic composition of hydraulic cylinder
The hydraulic cylinder is mainly composed of the following parts:
Cylinder body: It is the outer shell of the cylinder and bears the pressure of the hydraulic oil.
Piston: It is located inside the cylinder and performs linear reciprocating motion through the action of hydraulic oil.
Piston rod: It is connected to the piston and usually extends from one end of the cylinder body to transmit force.
End cover: The sealing component at both ends of the hydraulic cylinder is used to fix the piston and piston rod.
Seal: It is used to prevent hydraulic oil leakage and ensure the sealing of the cylinder.
Oil port: The pipe interface connecting the hydraulic system and the cylinder.

2. Working process
The working process of the hydraulic cylinder includes two main stages: extension and retraction. The working principle of each stage is slightly different.
(1) Extension process (piston rod extension)
When the hydraulic system provides pressurized oil, the oil enters the cylinder through one end of the cylinder (usually the blind end of the cylinder body). The pressurized oil pushes the piston forward, and the piston rod also extends outward with the piston. At this time:
The pressurized oil at the blind end of the cylinder pushes the piston to move.
A pressure oil chamber is formed on one side of the piston rod (i.e., the other side of the piston is the oil discharge chamber).
At the same time, the hydraulic oil flows back from the other side of the piston to the return oil system of the hydraulic pump through the outlet.
(2) Retraction process (piston rod retraction)
When the hydraulic system switches the oil circuit, the pressurized oil enters the other end of the cylinder (i.e., the piston rod end), the piston moves in the opposite direction, and the piston rod is pulled back. At this time:
The pressurized oil at the piston rod end pushes the piston to move in the opposite direction, discharging the hydraulic oil from the blind end.
The reverse movement of the piston causes the piston rod to retract and enter the cylinder.

3. Working principle of hydraulic cylinder
Piston side: When hydraulic oil enters the piston side (blind end) of the cylinder through high pressure, it pushes the piston forward.
Other side of the piston: The other side of the piston will discharge oil and return to the oil pump or return tank.
In this way, the hydraulic cylinder can achieve linear motion and generate enough force to drive mechanical equipment (such as bulldozers, lifts, rollers, etc.).

4. Control of hydraulic cylinder
The movement of hydraulic cylinder can be controlled in different ways:
Pressure control: Control the thrust of the cylinder by adjusting the output pressure of the oil pump.
Flow control: Adjust the speed of the cylinder by controlling the flow of hydraulic oil.
Direction control: Control the flow direction of the oil through valves (such as check valves, solenoid valves, etc.), thereby changing the extension and contraction direction of the cylinder.

Summary
The working principle of the hydraulic cylinder is to use the pressure of the fluid in the hydraulic system to drive the piston to move linearly, thereby converting it into mechanical energy. The pressure and flow of hydraulic oil control the speed and force of the cylinder. The hydraulic cylinders produced by engineering cylinder manufacturers are widely used in various fields such as engineering machinery, ship equipment, manufacturing industry, etc. that require large torque and thrust.