Structure and working principle of hydraulic cylinders
Hydraulic cylinders achieve energy conversion through the coordinated action of precision structures. Their performance is directly affected by sealing, material strength, and cushioning efficiency.
Release Time：
2025-05-30
The structure and working principle of a hydraulic cylinder are as follows:
I. Core Structure of a Hydraulic Cylinder
Cylinder Tube and Cylinder Head
The cylinder tube is the main body of the hydraulic cylinder, forming a sealed oil chamber with the cylinder head to withstand the thrust of high-pressure hydraulic oil. The cylinder head is connected by welding, threading, or bolts, and the material is often 35# or 45# steel or cast iron.
Piston and Piston Rod
The piston converts hydraulic energy into mechanical energy, and its effective area determines the output force; the piston rod transmits power, and the material is mostly medium carbon steel (such as 45# steel). The coaxiality tolerance of the two needs to be controlled within 0.03mm.
Sealing Device
Includes piston seal, piston rod seal, and end cover seal to prevent hydraulic oil leakage. For example, a dust seal and a guide sleeve are used for sealing between the piston rod and the cylinder head.
Buffer Device
Located at the end of the cylinder tube, it reduces the impact force of the piston hitting the end cover through a throttle hole or an adjustable buffer valve, avoiding violent vibration.
Guide Sleeve and Exhaust Device
The guide sleeve supports the piston rod and ensures motion accuracy, and the material is mostly wear-resistant cast iron or bronze; the exhaust device is used to remove air from the oil chamber to ensure smooth operation.
II. Working Principle
The hydraulic cylinder drives the piston to move through the pressure oil provided by the hydraulic system to achieve mechanical energy output:
Single-acting Hydraulic Cylinder
Hydraulic oil enters from one side to push the piston out, and the return stroke relies on a spring or external force for resetting.
Double-acting Hydraulic Cylinder
Hydraulic oil alternately enters the two oil chambers of the piston to achieve bidirectional drive. For example, when oil enters the rodless chamber, the thrust is large and the speed is slow; when oil enters the rod chamber, the thrust is small and the speed is fast.
Differential Hydraulic Cylinder
Uses the difference in effective area on both sides of the piston to achieve fast movement. During differential connection, pressure oil is simultaneously introduced into both chambers, and the piston moves at high speed towards the rod chamber.
III. Typical Application Forms
Type Features
Plunger Cylinder Only outputs force in one direction, requires external force for resetting, suitable for long stroke scenarios.
Telescopic Cylinder Multi-stage sleeve structure, can achieve ultra-long stroke, often used in cranes and dump trucks.
Swing Cylinder Outputs reciprocating rotary motion, suitable for mechanical devices that require angle adjustment.
IV. Key Technical Points
Material Selection: Pistons commonly use aluminum alloy or cast iron to balance lightweight and strength; guide sleeves require high wear resistance (such as bronze).
Sealing Optimization: Improve durability by combining sealing rings and dust seals to prevent hydraulic oil leakage and contaminant ingress.
Buffer Design: Slider shock absorbers or multi-stage buffer structures can reduce impact noise and extend equipment life.
Hydraulic cylinders achieve energy conversion through precise structural coordination, and their performance is directly affected by sealing, material strength, and buffering efficiency.
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