Hydraulic Cylinder Fundamentals And Composition

The hydraulic cylinder is a critical transmission component in a hydraulic system and is widely used in various mechanical equipment, such as automobiles, engineering machinery, and aerospace. It utilizes the pressure change of hydraulic oil to achieve the transmission of large forces and precise control of motion. This article will delve into the working principle, main applications, and role of the hydraulic cylinder in the hydraulic system.

What is a hydraulic cylinder?

A hydraulic cylinder is a mechanical device that utilizes hydraulic principles to generate power. It is commonly used in converting hydraulic energy into mechanical energy. A hydraulic cylinder consists of a cylinder body, piston, piston rod, seals, and oil ports. By regulating the pressure and flow of hydraulic oil, a hydraulic cylinder can achieve various movement forms such as pushing and pulling, lifting, and lowering.

The working principle of hydraulic cylinders is based on Pascal's principle. 

Pascal's principle states that in a closed container, pressure exerted on a liquid by an external force is evenly transmitted to every point in the container. In a hydraulic system, a hydraulic pump provides pressure oil into the hydraulic cylinder, causing the piston inside the cylinder to bear pressure. The piston moves under the pressure of the oil, thereby causing the piston rod to perform corresponding linear motion.


Hydraulic oil enters the hydraulic cylinder: The hydraulic pump pushes the hydraulic oil into the cylinder through the inlet port on one side of the cylinder.


Piston motion: The pressure of hydraulic oil exerts force on the piston, causing it to move along the axis of the hydraulic cylinder with a pushing force. The oil chamber on one end of the piston is under high pressure, while the oil chamber on the other end is under low pressure, thus generating a pushing force.


Hydraulic oil discharge: After the hydraulic oil is pushed to the other end by the piston, the pressure-reduced oil flow exits through the discharge port of the hydraulic cylinder, completing a work cycle.


By adjusting the output pressure and flow rate of the hydraulic pump, the movement speed, travel distance, and force exerted by the hydraulic ram can be controlled.



The structure and composition of hydraulic rods
The basic structure of a hydraulic rod consists of the following parts:
Cylinder: The cylinder is the outer shell of the hydraulic rod and primarily serves to hold the hydraulic oil and the movement of the piston. It is usually made of steel or aluminum alloy and is designed to be pressure-resistant and corrosion-resistant.


Piston and piston rod: The piston moves axially within the cylinder, and the piston rod connects to the piston and converts its motion into external mechanical motion.


Sealing Device: The sealing device for the hydraulic cylinder is a key component for preventing oil leakage. It typically includes O-rings and seal rings. The sealing device can effectively prevent oil leakage and reduce wear.


Oil inlet and oil outlet: The oil inlet is used for the input of hydraulic oil, while the oil outlet is used for the discharge of hydraulic oil.