The hydraulic cylinder is the executive element of hydraulic transmission, which is directly related to the working mechanism of the main engine. For different models and mechanisms, hydraulic cylinders have different uses and working requirements. Therefore, before designing the hydraulic cylinder, it is necessary to analyze the working conditions of the entire hydraulic system, compile the load diagram, select the working pressure of the system, and then select the structure type according to the use requirements, and determine its main work according to the load conditions, motion requirements, strokes, etc. Size, strength, stability, and buffering checks are carried out, and then the structural design is carried out.

Design content and steps of hydraulic cylinder

(1) Select the type of hydraulic cylinder and the structure of each part.

(2) Determine the working parameters and structural dimensions of the hydraulic cylinder.

(3) Calculation and checking of structural strength and stiffness.

(4) Design of guiding, sealing, dustproof, exhausting, and buffering devices.

(5) Draw assembly drawings, and parts drawings, and write design instructions.

What should be paid attention to in the design of a hydraulic cylinder?

Whether the design and use of the hydraulic cylinder are correct or not directly affects its performance and whether it is prone to failure. In this regard, problems such as improper installation of the hydraulic cylinder, eccentric load on the piston rod, sagging of the hydraulic cylinder or piston, and instability of the pressure rod of the piston rod are often encountered. Therefore, when designing hydraulic cylinders, the following points must be paid attention to:

(1) Try to make the piston rod of the hydraulic cylinder bear the load under tension, or have good stability under pressure

(2) Consider the braking problem at the end of the hydraulic cylinder stroke and the exhaust problem of the hydraulic cylinder. If there is no buffer device and exhaust device in the cylinder, corresponding measures should be taken in the system, but not all hydraulic cylinders need to consider these problems.

(3) Correctly determine the installation and fixing method of the hydraulic cylinder. If the piston rod that is subjected to bending cannot be connected with a thread, it should be connected with a spigot. Hydraulic rams cannot be positioned with keys or pins at both ends. It should only be positioned at one end so as not to hinder its expansion when heated. Such as shock loads compress the piston rod. The positioning piece must be set at the end of the piston rod, or at the end of the cylinder head if it is stretched.

(4) The structure of each part of the hydraulic cylinder should be designed according to the recommended structural form and design standards, and the structure should be as simple and compact as possible, and easy to process, assemble and maintain.

(5) Under the condition that the motion stroke and load force can be met, the outline size of the hydraulic cylinder should be reduced as much as possible.

(6) It should be sealed reliably and dustproof well. The reliable sealing of hydraulic cylinders is an important factor for their normal operation. If the leakage is serious, it will not only reduce the working efficiency of the hydraulic cylinder but even make it unable to work normally (for example, it cannot meet the requirements of load force and movement speed, etc.). Good dustproof measures help to improve the working life of hydraulic cylinders.

The design content of the hydraulic cylinder is not static. According to the specific situation, some design content can be omitted or less, or some new content can be added. The design steps may need to be modified many times to get the correct and reasonable design results. When designing a hydraulic cylinder, the correct selection of the type of hydraulic cylinder is the premise of all design calculations. When selecting the type of hydraulic cylinder, it is necessary to proceed from the requirements of the action characteristics, stroke length, and movement performance of the machine and equipment, and at the same time, the installation space and specific location provided by the structural characteristics of the main engine for the hydraulic cylinder should be considered. For example, it is simple and convenient to directly use the hydraulic cylinder to realize the reciprocating linear motion of the machine. For occasions requiring the same reciprocating speed, a double-piston-rod hydraulic cylinder can be used; if there is a requirement for rapid return, a single-piston-rod hydraulic cylinder should be used, and a differential connection can be considered. When the stroke is long, a plunger cylinder can be used to reduce the difficulty of the processing; when the stroke is long but the load is not large, some transmission devices can also be considered to expand the stroke. The reciprocating swing motion can be realized by either a swinging hydraulic cylinder or a linear hydraulic cylinder plus a link mechanism or a gear-rack mechanism.