Hydraulic cylinder is the key executive component to realize energy conversion in hydraulic system, which is widely used in industrial machinery, construction machinery, aerospace and other fields. In the design process of hydraulic system, the calculation of hydraulic cylinder is very important, which is directly related to the performance, efficiency and reliability of the system. This paper will introduce the basic calculation steps of hydraulic cylinder in detail.
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First, clear design parameters
Before the calculation of hydraulic cylinder, the following basic design parameters should be defined first:
1. Load force (f): the external force that the hydraulic cylinder needs to overcome, in Newton (n).
2. Motion speed (V): the motion speed of the piston rod of the hydraulic cylinder, in meters per second (m/s).
3. Stroke (L): the maximum stroke length of the piston of the hydraulic cylinder, in millimeters (mm).
4. Working pressure (P): the working pressure provided by the hydraulic system, usually MPa or bar.
5. System efficiency (η): the comprehensive efficiency of the hydraulic system, which is generally between 0.7 and 0.9.
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Second, calculate the hydraulic cylinder thrust and tension.
According to the load force and working pressure, the piston area required by the hydraulic cylinder can be calculated:
# Thrust formula:
$$ F_{ ext{ push }} = P imes A_{ ext{ no clubbed }} imes eta $$
# Tension formula:
$$ F_{ ext{ la }} = P imes (A_{ ext{ without a cavity }}-A_{ ext{ with a cavity }}) imes eta $$
Among them:
-$ A_{ ext{ rodless cavity}} $: effective area of rodless cavity (i.e. piston area);
-$ A_{ ext{ with rod cavity}} $: effective area of rod cavity (i.e.
cross-sectional area of piston rod);
-$ eta $: system efficiency;
By knowing the load force and the set working pressure, the required piston area can be deduced, and the cylinder diameter can be determined.
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Third, determine the cylinder diameter and rod diameter
According to the required effective area, calculate the inner diameter (cylinder diameter) of the hydraulic cylinder and the diameter (rod diameter) of the piston rod:
# Cylinder diameter calculation:
$$ D = sqrt{frac{4A}{pi}} $$
Where a is the required effective area.
# Rod diameter selection:
The selection of rod diameter should consider the stability and compression resistance of hydraulic cylinder, which is generally 0.4 ~ 0.6 times of cylinder diameter.
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Fourth, calculate the traffic demand
The running speed of the hydraulic cylinder is determined by the input flow, and the calculation formula is as follows:
$$ Q = A imes v imes 60 $$
The unit
is liters per minute (L/min).
Among them:
-A: effective area (m²)；;
-v: speed (m/s);
-60 is the unit conversion factor.
The minimum oil supply flow of hydraulic pump can be determined by this formula.
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Five, check the strength and stability of hydraulic cylinder
When the hydraulic cylinder works under high pressure, it is necessary to check the strength, including the wall thickness of the cylinder, the strength of the connecting bolt of the end cover and the bending stability of the piston rod.
1. Check the cylinder wall thickness
2. Stability check of piston rod and compression bar (Euler formula)
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Six, choose the seal and accessories
Select appropriate sealing materials and structures according to working environment and medium, such as O-ring and Y-ring. At the same time, choose appropriate accessories such as buffer device and exhaust device to improve service life and performance.
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tag
The calculation of hydraulic cylinder is a systematic project, which involves the interaction of multiple parameters. Only through scientific calculation method and reasonable selection design can the hydraulic cylinder run efficiently, stably and safely. In practical application, it is necessary to combine engineering experience and simulation analysis to further optimize the design results.